import {
  useMutation,
  useQuery,
  useQueryClient,
  useSuspenseQuery,
} from "@tanstack/react-query"
import { useNavigate } from "@tanstack/react-router"
import {
  Background,
  BackgroundVariant,
  type Connection,
  type Edge,
  type EdgeChange,
  type Node as FlowCanvasNode,
  type NodeChange,
  ReactFlow,
  ReactFlowProvider,
  useNodesState,
  useReactFlow,
  useStore,
  useUpdateNodeInternals,
} from "@xyflow/react"
import { Workflow } from "lucide-react"
import { motion } from "motion/react"
import { useCallback, useEffect, useMemo, useRef, useState } from "react"

import {
  type DevicePublic,
  type FlowDef_Input,
  type FlowDetail,
  FlowsService,
  type MessageSpec,
  type NodeDef_Input,
  RunsService,
} from "@/client"
import { DiscardDraftDialog } from "@/components/Common/Dock"
import {
  DEVICE_TYPE,
  deviceNodeOf,
  type ReportedPort,
  withPort,
} from "@/components/Devices/ports"
import { useTheme } from "@/components/theme-provider"
import { Button } from "@/components/ui/button"
import {
  Dialog,
  DialogContent,
  DialogDescription,
  DialogFooter,
  DialogHeader,
  DialogTitle,
} from "@/components/ui/dialog"
import useAuth from "@/hooks/useAuth"
import useCustomToast from "@/hooks/useCustomToast"
import { useIsMobile } from "@/hooks/useMobile"
import { scaleIn } from "@/lib/motion"
import { notify } from "@/lib/notificationStore"
import { safeStorage } from "@/lib/safeStorage"
import { inCodeEditor, useShortcuts } from "@/lib/shortcuts"
import { cn } from "@/lib/utils"
import { CanvasTitle } from "./CanvasTitle"
import { CommandPalette } from "./CommandPalette"
import {
  bindingsKey,
  boundaryKey,
  deriveEdges,
  type FlowEdgeData,
  flowOf,
  portOf,
  qualify,
} from "./deriveEdges"
import { EdgeInspector, type InspectedEdge } from "./EdgeInspector"
import { EndpointNode } from "./EndpointNode"
import {
  deriveEndpoints,
  ENDPOINT_TYPE,
  type EndpointNodeData,
  isEndpointNode,
} from "./endpoints"
import { FIT_VIEW, FIT_VIEW_PANEL, FlowDock } from "./FlowDock"
import { FlowNode, type FlowNodeData } from "./FlowNode"
import { FlowPanel } from "./FlowPanel"
import { InputInspector, type InspectedInput } from "./InputInspector"
import { LiveEdge } from "./LiveEdge"
import {
  type Direction,
  type Layout,
  layoutGraph,
  type NodeShape,
} from "./layout"
import { NodePanel } from "./NodePanel"
import { RunDialog } from "./RunDialog"
import "./flow.css"
import { liveStore, useFlowPaused } from "./liveStore"
import {
  flowKeys,
  flowQueryOptions,
  flowsQueryOptions,
  nodeTypesQueryOptions,
  useAutosave,
  useDiscardDraft,
  usePublish,
} from "./queries"
import { useFlowSocket } from "./useFlowSocket"

const nodeTypes = { flow: FlowNode, [ENDPOINT_TYPE]: EndpointNode }

/**
 * Where every node sits and how every edge runs, once the engine has said so.
 *
 * The layout is a chunk of its own and answers asynchronously, so a canvas has
 * a moment before it knows where anything goes. It draws nothing at all until
 * then — a route already shows a skeleton for that — and an *edit* keeps the
 * arrangement it had, so only the node that changed lands a frame late rather
 * than the whole graph flickering through the corner.
 */
function useLayout(
  ids: string[],
  edges: Edge[],
  direction: Direction,
  shapes: Map<string, NodeShape>,
  shapeKey: string,
): Layout | null {
  const [placed, setPlaced] = useState<Layout | null>(null)
  // biome-ignore lint/correctness/useExhaustiveDependencies: the shape key is the dependency; the arrays are rebuilt every render.
  useEffect(() => {
    let stale = false
    layoutGraph(ids, edges, direction, shapes).then((layout) => {
      // A graph edited while the last one was still being laid out has already
      // asked for another; that one is the answer, not this.
      if (!stale) setPlaced(layout)
    })
    return () => {
      stale = true
    }
  }, [shapeKey, edges])
  return placed
}

/** Is this canvas node actually part of the flow document? */
const isDocumentNode = (node: { id: string }) => !isEndpointNode(node)
const edgeTypes = { live: LiveEdge }

type Rebind = {
  nodeId: string
  nodeLabel: string
  port: string
  from: string
  to: string
  dtype: MessageSpec["dtype"]
}

/** A finished message rename, waiting on an answer about the rest of the flow. */
type MessageRename = {
  from: string
  to: string
  /** How many other nodes are still bound to the old name. */
  count: number
}

/** Documents to step back and forward through, newest last. */
type History = {
  past: FlowDef_Input[]
  future: FlowDef_Input[]
  /** When the last entry was recorded, so a burst of typing stays one edit. */
  at: number
}

const HISTORY_LIMIT = 50
const TYPING_WINDOW = 500

/** Nodes copied here, and the code of the ones carrying their own. */
type NodeClipboard = {
  nodes: NodeDef_Input[]
  sources: Record<string, string>
}

// ponytail: localStorage, so a copy survives a flow switch or a second tab but
// not a second browser. The system clipboard if that ever matters.
const CLIPBOARD_KEY = "fluksio.nodeClipboard"

/**
 * Remember the document as it was before a change.
 *
 * Fields commit on every keystroke, so consecutive edits that leave the same
 * nodes in place fold into the entry already on the stack. Anything that adds
 * or removes a node is a finished action and starts its own.
 */
function record(
  history: History,
  previous: FlowDef_Input,
  next: FlowDef_Input,
  settled: boolean,
) {
  const before = previous.nodes ?? []
  const after = next.nodes ?? []
  const sameNodes =
    before.length === after.length &&
    before.every((node, index) => node.id === after[index].id)
  const stillTyping =
    !settled && sameNodes && Date.now() - history.at < TYPING_WINDOW

  if (!stillTyping) {
    history.past.push(previous)
    if (history.past.length > HISTORY_LIMIT) history.past.shift()
  }
  history.at = settled ? 0 : Date.now()
  // A new change is a new branch: what was undone is not coming back.
  history.future = []
}

/** Positions come from the layout, so xyflow's own state only tracks identity. */
function toCanvasNodes(definitions: NodeDef_Input[]): FlowCanvasNode[] {
  return definitions.map((node) => ({
    id: node.id,
    type: "flow",
    position: { x: 0, y: 0 },
    data: {},
  }))
}

/**
 * The dot grid lives in flow space, so React Flow shrinks it along with the
 * zoom. Below 1:1 that leaves sub-pixel dots on a fractional grid, which the
 * canvas can only render as a moiré haze — the whole viewport reads as blurry.
 * Taking the zoom back out of both the radius and the spacing gives the same
 * crisp 1.5px dots, 24px apart, whatever the zoom is.
 */
function CanvasBackground() {
  const zoom = useStore((state) => state.transform[2])
  // In octaves, so the grid halves rather than drifting as you zoom.
  const step = 2 ** Math.round(Math.log2(1 / zoom))
  return (
    <Background
      variant={BackgroundVariant.Dots}
      gap={24 * step}
      size={1.5 / zoom}
    />
  )
}

/**
 * Whether arriving on this id selects it. A node does, and so does another
 * flow's label, which is where a link from that flow lands; every other
 * endpoint opens what it stands for instead.
 */
function landsOn(id: string): boolean {
  return !isEndpointNode({ id }) || id.startsWith("flow:")
}

/** A name that does not collide with the nodes already on the canvas. */
function uniqueNodeId(existing: NodeDef_Input[], type: string): string {
  const taken = new Set(existing.map((node) => node.id))
  for (let index = 1; ; index += 1) {
    const candidate = index === 1 ? type : `${type}_${index}`
    if (!taken.has(candidate)) return candidate
  }
}

function FlowEditorInner({
  flowName,
  focus,
  onReload,
}: {
  flowName: string
  /** A node or endpoint to arrive on, from the address bar. */
  focus?: string
  onReload: () => void
}) {
  const navigate = useNavigate()
  const queryClient = useQueryClient()
  const { showErrorToast, showSuccessToast } = useCustomToast()
  const { fitView } = useReactFlow()
  const updateNodeInternals = useUpdateNodeInternals()
  const { resolvedTheme } = useTheme()

  const { data: flows } = useSuspenseQuery(flowsQueryOptions())
  const { data: detail } = useSuspenseQuery(flowQueryOptions(flowName))
  const { data: nodeTypeInfo } = useQuery(nodeTypesQueryOptions())

  const {
    save,
    flush,
    conflict,
    resolveConflict,
    adopt,
    mutation: saving,
  } = useAutosave(flowName)
  const publish = usePublish(flowName)
  const discard = useDiscardDraft(flowName)

  // The whole working document, so a flow-level edit is an edit like any
  // other — undoable, and on screen before the server has seen it.
  const [flowDoc, setFlowDoc] = useState<FlowDef_Input>(() => detail.definition)
  const definitions = useMemo(() => flowDoc.nodes ?? [], [flowDoc])
  const [canvasNodes, setCanvasNodes, onNodesChange] = useUnpositionedNodes(
    detail.definition.nodes ?? [],
  )
  // An endpoint is never selected; arriving on one opens it instead (below).
  // Another flow's label is the exception: it is where a link from that flow
  // lands, so it is selected like a node.
  const [selectedId, setSelectedId] = useState<string | null>(
    focus && landsOn(focus) ? focus : null,
  )
  const [paletteOpen, setPaletteOpen] = useState(false)
  const [inspected, setInspected] = useState<InspectedEdge | null>(null)
  const [inspectedInput, setInspectedInput] = useState<InspectedInput | null>(
    null,
  )
  // The edges are derived, so xyflow's own selection would be thrown away on
  // every rebuild: the ids live here instead and are marked on at render.
  const [selectedEdges, setSelectedEdges] = useState<ReadonlySet<string>>(
    () => new Set(),
  )
  const [rebind, setRebind] = useState<Rebind | null>(null)
  const [renamed, setRenamed] = useState<MessageRename | null>(null)
  const [flowPanelOpen, setFlowPanelOpen] = useState(false)
  // A batch run is asked for its parameters before it is submitted.
  const [runOpen, setRunOpen] = useState(false)
  // Throwing an edit away is offered from the dock, so its confirmation lives
  // here rather than inside the settings panel.
  const [discardOpen, setDiscardOpen] = useState(false)
  // The editor at full size takes the width the canvas chrome does not need.
  const [editorExpanded, setEditorExpanded] = useState(false)
  // The dock hosts the logs, but a failing node opens them too, at its own
  // lines — so which node and whether it is open belong here.
  const [logsOpen, setLogsOpen] = useState(false)
  const [logsNode, setLogsNode] = useState<string | null>(null)

  const issues = detail.issues ?? []
  const paused = useFlowPaused(flowName)

  // Keep the latest document in a ref so autosave never captures a stale copy.
  const latest = useRef<FlowDef_Input>(detail.definition)
  const history = useRef<History>({ past: [], future: [], at: 0 })

  /** Put a document on the canvas and on its way to the server. */
  const applyDoc = useCallback(
    (next: FlowDef_Input) => {
      setFlowDoc(next)
      latest.current = next
      save(next)
    },
    [save],
  )

  /** Apply a change to the whole document and make it undoable. */
  const commitDoc = useCallback(
    (next: FlowDef_Input, settled = false) => {
      record(history.current, latest.current, next, settled)
      applyDoc(next)
    },
    [applyDoc],
  )

  /** The same, for the changes that only touch the nodes. */
  const commit = useCallback(
    (nodes: NodeDef_Input[]) => {
      commitDoc({ ...latest.current, nodes })
    },
    [commitDoc],
  )

  /**
   * Step through the history. Undo and redo save like any other edit, so the
   * autosave debounce collapses a run of them into one write.
   */
  const step = useCallback(
    (back: boolean) => {
      const { past, future } = history.current
      const remembered = (back ? past : future).pop()
      if (!remembered) return
      ;(back ? future : past).push(latest.current)
      history.current.at = 0
      // xyflow owns the positions, so hand it the remembered ones too.
      setCanvasNodes(toCanvasNodes(remembered.nodes ?? []))
      applyDoc(remembered)
      setInspected(null)
    },
    [applyDoc, setCanvasNodes],
  )

  const typeLabels = useMemo(
    () => new Map((nodeTypeInfo ?? []).map((info) => [info.type, info.title])),
    [nodeTypeInfo],
  )

  // Which types bring code of their own, so a copy has something to carry.
  const sourceTypes = useMemo(
    () =>
      new Set(
        (nodeTypeInfo ?? [])
          .filter((info) => info.has_source)
          .map((info) => info.type),
      ),
    [nodeTypeInfo],
  )

  // Which types run code of their own, a source or a command. Adding one is a
  // superuser's, so nobody else is offered one.
  const { user } = useAuth()
  const mayEditCode = Boolean(user?.is_superuser)
  const lockedTypes = useMemo(
    () =>
      new Set(
        mayEditCode
          ? []
          : (nodeTypeInfo ?? [])
              .filter((info) => info.runs_code)
              .map((info) => info.type),
      ),
    [nodeTypeInfo, mayEditCode],
  )

  // Which types came from an installed connector rather than the engine. They
  // cannot be in the icon map, so they share one.
  const pluginTypes = useMemo(
    () =>
      new Set(
        (nodeTypeInfo ?? [])
          .filter((info) => info.plugin)
          .map((info) => info.type),
      ),
    [nodeTypeInfo],
  )

  const issuesByNode = useMemo(() => {
    const map = new Map<string, string[]>()
    for (const issue of issues) {
      // A node's dot and border are its status channel, and status has no
      // warning tier — an advisory is not a fault, so it says its piece in the
      // dock rather than painting the node red.
      if (!issue.node || issue.advisory) continue
      const list = map.get(issue.node) ?? []
      list.push(issue.message)
      map.set(issue.node, list)
    }
    return map
  }, [issues])

  const showLogs = useCallback((nodeId: string) => {
    setLogsNode(nodeId)
    setLogsOpen(true)
  }, [])

  // Canvas nodes carry the definition so the node component can render it.
  const renderedNodes = useMemo(
    () =>
      canvasNodes.map((node) => {
        const definition = definitions.find((entry) => entry.id === node.id)
        const nodeIssues = issuesByNode.get(`${flowName}.${node.id}`) ?? []
        return {
          ...node,
          selected: node.selected || node.id === selectedId,
          data: {
            definition: definition ?? { id: node.id },
            flow: flowName,
            typeLabel:
              typeLabels.get(definition?.type ?? "") ?? definition?.type ?? "",
            isPlugin: pluginTypes.has(definition?.type ?? ""),
            issueText: nodeIssues.join("\n"),
            onShowLogs: showLogs,
          } satisfies FlowNodeData,
        }
      }),
    [
      canvasNodes,
      definitions,
      flowName,
      issuesByNode,
      pluginTypes,
      selectedId,
      showLogs,
      typeLabels,
    ],
  )

  // A cheap fingerprint of the wiring, and the only thing the layout depends
  // on: what the graph looks like follows from what is wired to what. The
  // flow's own boundary is drawn too, so a declared input counts as wiring.
  const key = `${bindingsKey(definitions)}|${boundaryKey(flowDoc)}`

  // Offer the names already in play: everything published is worth reading,
  // and an input nobody provides yet is worth publishing.
  // biome-ignore lint/correctness/useExhaustiveDependencies: the bindings key is what changes names.
  const suggestions = useMemo(() => {
    const provided = new Set<string>()
    const consumed = new Set<string>()
    for (const node of definitions) {
      for (const spec of node.provides ?? []) {
        if (spec.name) provided.add(spec.name)
      }
      for (const spec of node.requires ?? []) {
        if (spec.name) consumed.add(spec.name)
      }
    }
    return {
      consumes: [...provided].sort(),
      provides: [...consumed].filter((name) => !provided.has(name)).sort(),
    }
  }, [key])

  /**
   * Where clicking an endpoint takes you: the thing it stands for.
   *
   * `via` is the node here it is wired to. The other flow draws that node as
   * a label of its own, which is where following the link lands.
   */
  const openEndpoint = useCallback(
    (id: string, via?: string) => {
      const [kind, rest] = id.split(":", 2)
      if (kind === "input" || kind === "output") {
        // This flow's own boundary, declared in its settings.
        setSelectedId(null)
        setFlowPanelOpen(true)
      } else if (kind === "dashboard") {
        navigate({
          to: "/dashboards/$name",
          params: { name: (rest ?? "").split(":")[0] },
        })
      } else if (kind === "flow") {
        navigate({
          to: "/flows/$flowName",
          params: { flowName: (rest ?? "").split(".")[0] },
          search: { node: `flow:${via ? `${flowName}.${via}` : flowName}` },
        })
      }
    },
    [navigate, flowName],
  )

  // React Flow measures a node once and keeps the size on it. An endpoint is
  // not in `canvasNodes`, so the measurement it reports back has nowhere to
  // land: without carrying it over by hand the endpoint arrives unmeasured on
  // the next render, and React Flow draws an unmeasured node hidden, taking
  // the edges attached to it with it.
  const measured = useRef(new Map<string, { width: number; height: number }>())
  const trackMeasured = useCallback(
    (changes: NodeChange<FlowCanvasNode>[]) => {
      for (const change of changes) {
        if (change.type !== "dimensions" || !change.dimensions) continue
        if (isEndpointNode({ id: change.id })) {
          measured.current.set(change.id, change.dimensions)
        }
      }
      onNodesChange(changes)
    },
    [onNodesChange],
  )

  /** Selection is all an edge change can carry here: nothing else is stored. */
  const onEdgesChange = useCallback((changes: EdgeChange[]) => {
    const selections = changes.filter((change) => change.type === "select")
    if (!selections.length) return
    setSelectedEdges((current) => {
      const next = new Set(current)
      for (const change of selections) {
        if (change.selected) next.add(change.id)
        else next.delete(change.id)
      }
      return next
    })
  }, [])

  // Dashboards and other flows wired into this one. They are drawn but never
  // stored: they join at render, after everything that reads or writes
  // canvasNodes, so an autosave, an undo or a delete cannot reach them.
  // biome-ignore lint/correctness/useExhaustiveDependencies: the key covers the wiring, which is all these depend on.
  const external = useMemo(() => {
    const built = deriveEndpoints(
      detail.endpoints ?? [],
      definitions,
      flowName,
      flowDoc,
    )
    return {
      ...built,
      nodes: built.nodes.map((node) => {
        const size = measured.current.get(node.id)
        return size ? { ...node, measured: size, ...size } : node
      }),
    }
  }, [detail.endpoints, key, flowName])

  // Edges follow from the name bindings, so they are derived, never stored.
  // biome-ignore lint/correctness/useExhaustiveDependencies: the key is the dependency; the array identity changes on every render.
  const edges = useMemo(
    () => [...deriveEdges(definitions, flowName), ...external.edges],
    [key, flowName, detail.endpoints],
  )

  // Arrived from another flow: the label standing for the node the link left
  // from, or failing that any label of that flow. Its edges are lit with it,
  // so the connection that was followed is the one that reads first.
  const landing = useMemo(() => {
    if (!selectedId?.startsWith("flow:")) return null
    const ids = external.nodes.map((node) => node.id)
    if (ids.includes(selectedId)) return selectedId
    const origin = flowOf(selectedId.slice("flow:".length))
    return ids.find((id) => id.startsWith(`flow:${origin}.`)) ?? null
  }, [selectedId, external])

  const isMobile = useIsMobile()
  // Which way the graph runs. A phone has height to spare and no width, so it
  // reads top to bottom; everything else reads left to right.
  const direction: Direction = isMobile ? "TB" : "LR"

  // Expanding is a desktop affordance, so a window narrowed past `md` gives the
  // room back: the sheet it becomes has no second column to hold, and its body
  // only scrolls while the editor is its normal size.
  useEffect(() => {
    if (isMobile) setEditorExpanded(false)
  }, [isMobile])

  /**
   * Nobody places a node here — the graph lays itself out, endpoints included,
   * so a producer lands upstream of what it feeds without a lane of its own.
   *
   * Keyed on which nodes exist and how they are wired, never on the node
   * objects: React Flow writes measurements back through `onNodesChange`, so
   * their identity changes constantly and the layout would run on every frame.
   */
  const ids = [
    ...canvasNodes.map((node) => node.id),
    ...external.nodes.map((node) => node.id),
  ]
  const shapeKey = `${direction}|${key}|${ids.join(",")}`
  // What each node is, as far as the layout is concerned: the ports it draws,
  // in the order it draws them. A function of the document — the bindings key
  // above already covers every port, so this changes exactly when the layout
  // has to run again, and nothing measured is ever fed back into it.
  const shapes = new Map<string, NodeShape>([
    ...definitions.map(
      (node) =>
        [
          node.id,
          {
            requires: (node.requires ?? []).map(portOf),
            provides: (node.provides ?? []).map(portOf),
          },
        ] as const,
    ),
    ...external.nodes.map((node) => {
      const data = node.data as EndpointNodeData
      return [
        node.id,
        { requires: data.requires, provides: data.provides, endpoint: true },
      ] as const
    }),
  ])
  const layout = useLayout(ids, edges, direction, shapes, shapeKey)
  const positions = layout?.positions ?? null

  /**
   * The endpoints, placed.
   *
   * Memoised rather than mapped at render: React Flow keeps a node's
   * measurement against the object it measured, and an endpoint is not in
   * `canvasNodes`, so handing over a fresh one every render would leave it
   * permanently unmeasured — which React Flow draws as hidden.
   */
  const externalNodes = useMemo(
    () =>
      external.nodes
        // A node the layout has not placed yet — one just added, or the whole
        // graph on the first render — is left out rather than drawn at the
        // origin, which is where every unplaced node would pile up.
        .filter((node) => positions?.has(node.id))
        .map((node) => ({
          ...node,
          selected: node.id === landing,
          position: positions?.get(node.id) ?? node.position,
        })),
    [external, positions, landing],
  )

  // Marked after the layout has had the derived array, so selecting an edge
  // never sends the graph through the layout again. The route rides along
  // the same way.
  const shownEdges = useMemo(
    () =>
      edges.map((edge) => ({
        ...edge,
        data: {
          ...(edge.data as FlowEdgeData),
          route: layout?.routes.get(edge.id),
        },
        selected:
          selectedEdges.has(edge.id) ||
          edge.source === landing ||
          edge.target === landing,
      })),
    [edges, selectedEdges, landing, layout],
  )

  const shownNodes = useMemo(
    () => [
      ...renderedNodes
        .filter((node) => positions?.has(node.id))
        .map((node) => ({
          ...node,
          position: positions?.get(node.id) ?? node.position,
        })),
      ...externalNodes,
    ],
    [renderedNodes, externalNodes, positions],
  )

  // Editing ports adds and removes handles, and flipping direction moves them
  // to the other side. React Flow measures those once, so it has to be told,
  // or an edge to a brand-new handle never gets drawn.
  // biome-ignore lint/correctness/useExhaustiveDependencies: the bindings key is what changes handles.
  useEffect(() => {
    updateNodeInternals([
      ...definitions.map((node) => node.id),
      ...external.nodes.map((node) => node.id),
    ])
  }, [key, direction, external, updateNodeInternals])

  // The canvas is not remounted per node — that would throw the session away
  // on every click in the brain graph — so arriving at a flow already open
  // only changes the address. Seeded above for the first arrival, set here for
  // the ones after it. An endpoint — an input or output found by the search —
  // does what clicking its label does, which also covers one the canvas does
  // not draw because a dashboard already accounts for it. Another flow's label
  // is landed on instead, being where a link from that flow arrives.
  useEffect(() => {
    if (!focus) return
    if (landsOn(focus)) {
      setFlowPanelOpen(false)
      setSelectedId(focus)
    } else {
      openEndpoint(focus)
    }
  }, [focus, openEndpoint])

  const selected = definitions.find((node) => node.id === selectedId) ?? null
  // A panel is the view you are working in, so it takes the room — but never
  // the lanes the bars sit in: publishing is most wanted right after editing.
  const panelOpen = Boolean(selected) || flowPanelOpen

  // One effect owns the viewport, so nothing fights over it. Selecting a node
  // brings that node into the lane the panel leaves; every other change to the
  // graph — new wiring, a new endpoint, a panel opening — re-fits the whole flow
  // into the same lane. Which of the two runs is decided by what changed, not by
  // what is true: a selection centres once, and the port edits that follow it
  // re-fit around it, because a new edge's far end is what wants to be seen.
  // The first fit is instant: an animated one travels from React Flow's
  // default viewport to the content, which is the whole flow visibly sliding
  // in from the corner every time one is opened. Later fits move from
  // somewhere the user was already looking, so those stay animated.
  const fitted = useRef(false)
  const centred = useRef<string | null>(null)
  // biome-ignore lint/correctness/useExhaustiveDependencies: refit when the shape or the panel changes, not on every render.
  useEffect(() => {
    // Recorded as centred only once the fit below has run: arriving from
    // another screen selects before the layout has answered, and spending the
    // selection on the early returns is what fitted the whole flow instead.
    // Another flow's label is centred once it has been found on this canvas.
    const target = selectedId?.startsWith("flow:") ? landing : selectedId
    const focus = target && selectedId !== centred.current ? target : null
    // A phone's sheet covers the canvas outright, and so does the expanded
    // editor: there is no viewport to aim.
    if (editorExpanded) return
    // Nothing is on the canvas until the layout has answered, and fitting an
    // empty one would spend the single instant fit on nothing.
    if (!positions) return
    const frame = requestAnimationFrame(() => {
      const view = panelOpen && !isMobile ? FIT_VIEW_PANEL : FIT_VIEW
      const duration = fitted.current ? 300 : 0
      fitView(
        focus
          ? { ...view, nodes: [{ id: focus }], duration }
          : { ...view, duration },
      )
      fitted.current = true
      centred.current = selectedId
    })
    return () => cancelAnimationFrame(frame)
  }, [
    direction,
    definitions.length,
    external.nodes.length,
    edges.length,
    positions,
    selectedId,
    landing,
    panelOpen,
    editorExpanded,
    isMobile,
    fitView,
  ])

  const runMutation = useMutation({
    mutationFn: (inputs: Record<string, unknown> = {}) =>
      FlowsService.runFlow({ name: flowName, requestBody: { inputs } }),
    onSuccess: (state) => {
      liveStore.setValues(
        Object.fromEntries(
          Object.entries(state.values ?? {}).map(([name, value]) => [
            name,
            { value: value.value, ts: value.ts ?? null },
          ]),
        ),
      )
    },
    onError: () =>
      showErrorToast("The flow could not run. Check the node errors."),
  })

  /**
   * Pressing Run.
   *
   * A batch flow is submitted as a run, and a run is identified by its
   * parameters — so it asks for them rather than quietly using the defaults.
   */
  const startRun = useCallback(async () => {
    // Running executes what is stored, so the queued edit goes first.
    await flush()
    if (latest.current.mode === "batch") setRunOpen(true)
    else runMutation.mutate({})
  }, [flush, runMutation])

  const enableMutation = useMutation({
    mutationFn: (next: boolean) =>
      next
        ? FlowsService.startFlow({ name: flowName })
        : FlowsService.stopFlow({ name: flowName }),
    onSuccess: (detail) => {
      queryClient.setQueryData(flowKeys.detail(flowName), detail)
      queryClient.invalidateQueries({ queryKey: flowKeys.all, exact: true })
    },
    onError: () => showErrorToast("The flow could not be started or stopped."),
  })

  const pauseMutation = useMutation({
    mutationFn: (next: boolean) =>
      next
        ? FlowsService.pauseFlow({ name: flowName })
        : FlowsService.resumeFlow({ name: flowName }),
    // The engine answers with a flow_paused event, which is what the dock reads.
    onError: () => showErrorToast("The flow could not be paused."),
  })

  const stepMutation = useMutation({
    mutationFn: () => FlowsService.stepFlow({ name: flowName }),
    // Says which node ran, or that nothing was held back — both are answers.
    onSuccess: (result) => showSuccessToast(result.message),
    onError: () => showErrorToast("The flow could not be stepped."),
  })

  const deleteMutation = useMutation({
    mutationFn: async (withRuns: boolean) => {
      await FlowsService.deleteFlow({ name: flowName })
      // After the flow, which is refused while a run is live, so a refusal
      // leaves both standing.
      if (withRuns)
        await RunsService.deleteRuns({ flow: flowName, history: true })
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: flowKeys.all })
      setFlowPanelOpen(false)
      navigate({ to: "/flows", replace: true })
    },
    onError: () => showErrorToast("The flow could not be deleted."),
  })

  const sourceMutation = useMutation({
    mutationFn: async ({
      nodeId,
      code,
      drop,
    }: {
      nodeId: string
      code: string
      drop?: boolean
    }) => {
      // The server reads the ports off the header and compares them with its
      // draft, so the ports on the canvas have to be there first.
      await flush()
      return FlowsService.saveNodeSource({
        name: flowName,
        nodeId,
        requestBody: { code },
        drop,
      })
    },
    // One at a time: the save that drops a port must not land before the
    // autosave that kept it.
    scope: { id: `source:${flowName}` },
    onSuccess: (saved) => {
      const followed = saved.node
      if (followed && saved.version) {
        // The header changed the ports in the draft: take them, and the
        // version they moved it to, so the next save is not a conflict.
        adopt(saved.version)
        commit(
          (latest.current.nodes ?? []).map((node) =>
            node.id === followed.id
              ? {
                  ...node,
                  requires: followed.requires,
                  params: followed.params,
                }
              : node,
          ),
        )
      }
      queryClient.invalidateQueries({ queryKey: ["flows", flowName] })
    },
  })

  const addNode = useCallback(
    (type: string, sourceRef?: string) => {
      const id = uniqueNodeId(definitions, sourceRef ?? type)
      const node: NodeDef_Input = {
        id,
        type,
        params: {},
        requires: [],
        provides: [],
        // A shared node brings the code; the ports and settings are this
        // flow's own.
        ...(sourceRef ? { source_ref: sourceRef } : {}),
      }
      // Unwired, so the layout puts it in a rank of its own until it is bound.
      setCanvasNodes([
        ...canvasNodes,
        { id, type: "flow", position: { x: 0, y: 0 }, data: {} },
      ])
      commit([...definitions, node])
      setSelectedId(id)
    },
    [canvasNodes, commit, definitions, setCanvasNodes],
  )

  const updateNode = useCallback(
    (next: NodeDef_Input) => {
      commit(definitions.map((node) => (node.id === next.id ? next : node)))
    },
    [commit, definitions],
  )

  /**
   * A port a device reports, on this flow's node for that device. One node per
   * device keeps its ports together, so it is made only when there is none.
   */
  const addDevicePort = useCallback(
    (device: DevicePublic, port: ReportedPort) => {
      const existing = deviceNodeOf(definitions, device.id)
      if (existing) {
        updateNode(withPort(existing, port))
        setSelectedId(existing.id)
        return
      }
      const id = uniqueNodeId(definitions, device.id)
      const node = withPort(
        {
          id,
          type: DEVICE_TYPE,
          title: device.title || device.id,
          params: { device: device.id, config: {} },
          requires: [],
          provides: [],
        },
        port,
      )
      setCanvasNodes([
        ...canvasNodes,
        { id, type: "flow", position: { x: 0, y: 0 }, data: {} },
      ])
      commit([...definitions, node])
      setSelectedId(id)
    },
    [canvasNodes, commit, definitions, setCanvasNodes, updateNode],
  )

  const deleteNodes = useCallback(
    (ids: string[]) => {
      const remaining = definitions.filter((node) => !ids.includes(node.id))
      setCanvasNodes(canvasNodes.filter((node) => !ids.includes(node.id)))
      commit(remaining)
      if (selectedId && ids.includes(selectedId)) setSelectedId(null)
    },
    [canvasNodes, commit, definitions, selectedId, setCanvasNodes],
  )

  const applyBinding = useCallback(
    (nodeId: string, port: string, message: string) => {
      commit(
        definitions.map((node) =>
          node.id === nodeId
            ? {
                ...node,
                requires: (node.requires ?? []).map((spec) =>
                  portOf(spec) === port
                    ? { ...spec, name: message, port }
                    : spec,
                ),
              }
            : node,
        ),
      )
    },
    [commit, definitions],
  )

  /**
   * Dragging output to input is shorthand for "consume what that node
   * publishes": it points the input at the producer's message name.
   */
  const onConnect = useCallback(
    (connection: Connection) => {
      const producer = definitions.find((node) => node.id === connection.source)
      const consumer = definitions.find((node) => node.id === connection.target)
      if (!producer || !consumer) return

      const outSpec = (producer.provides ?? []).find(
        (spec) => portOf(spec) === connection.sourceHandle,
      )
      const inSpec = (consumer.requires ?? []).find(
        (spec) => portOf(spec) === connection.targetHandle,
      )
      if (!outSpec?.name || !inSpec) return

      // Already reading something else: the user may want either message, so
      // offer the extra port rather than assuming a replacement.
      if (inSpec.name && inSpec.name !== outSpec.name) {
        setRebind({
          nodeId: consumer.id,
          nodeLabel: consumer.title || consumer.id,
          port: portOf(inSpec),
          from: inSpec.name,
          to: outSpec.name,
          dtype: outSpec.dtype,
        })
        return
      }

      applyBinding(consumer.id, portOf(inSpec), outSpec.name)
    },
    [definitions, applyBinding],
  )

  /** Give the consumer a second input, bound to the producer's message. */
  const addInputPort = useCallback(
    (nodeId: string, message: string, dtype: MessageSpec["dtype"]) => {
      commit(
        definitions.map((node) =>
          node.id === nodeId
            ? {
                ...node,
                requires: [
                  ...(node.requires ?? []),
                  { name: message, port: "", dtype },
                ],
              }
            : node,
        ),
      )
    },
    [commit, definitions],
  )

  const unbind = useCallback(
    (message: string) => {
      const qualified = qualify(flowName, message)
      commit(
        definitions.map((node) => ({
          ...node,
          requires: (node.requires ?? []).map((spec) =>
            qualify(flowName, spec.name ?? "") === qualified
              ? { ...spec, name: "", port: portOf(spec) }
              : spec,
          ),
        })),
      )
      setInspected(null)
    },
    [commit, definitions, flowName],
  )

  /**
   * A message name is shared, not owned: renaming it where it is published
   * strands every node still reading the old one. Offer to bring them along
   * rather than deciding for the user.
   */
  const proposeRename = useCallback(
    (from: string, to: string) => {
      if (!from || !to) return
      const message = qualify(flowName, from)
      const bound = definitions.filter((node) =>
        [...(node.requires ?? []), ...(node.provides ?? [])].some(
          (spec) => qualify(flowName, spec.name ?? "") === message,
        ),
      )
      if (bound.length) setRenamed({ from, to, count: bound.length })
    },
    [definitions, flowName],
  )

  /** Carry a rename to everything bound to the old name, as one edit. */
  const applyRename = useCallback(
    ({ from, to }: MessageRename) => {
      const message = qualify(flowName, from)
      const follow = (specs: MessageSpec[] | undefined) =>
        (specs ?? []).map((spec) =>
          qualify(flowName, spec.name ?? "") === message
            ? { ...spec, name: to, port: "" }
            : spec,
        )
      commit(
        definitions.map((node) => ({
          ...node,
          requires: follow(node.requires),
          provides: follow(node.provides),
        })),
      )
      setRenamed(null)
    },
    [commit, definitions, flowName],
  )

  const focusNode = useCallback(
    (qualifiedId: string) => {
      const id = qualifiedId.startsWith(`${flowName}.`)
        ? qualifiedId.slice(flowName.length + 1)
        : qualifiedId
      setSelectedId(id)
    },
    [flowName],
  )

  /** Put the stored draft live. Publishing what is queued means saving first. */
  const publishFlow = useCallback(async () => {
    await flush()
    // Publish what was actually stored: the version only advances once the
    // queued save has landed.
    const current = queryClient.getQueryData<FlowDetail>(
      flowKeys.detail(flowName),
    )
    publish.mutate(current?.definition.version ?? 1)
  }, [flowName, flush, publish.mutate, queryClient])

  /** Copy the selected nodes, with the code of the ones carrying their own. */
  const copyNodes = useCallback(async () => {
    const ids = new Set(
      canvasNodes.filter((node) => node.selected).map((node) => node.id),
    )
    if (selectedId) ids.add(selectedId)
    const picked = definitions.filter((node) => ids.has(node.id))
    if (!picked.length) return

    const sources: Record<string, string> = {}
    await Promise.all(
      picked
        // A shared node already points at the library copy; only a private
        // one has code that has to travel with it.
        .filter((node) => !node.source_ref && sourceTypes.has(node.type ?? ""))
        .map(async (node) => {
          const { code } = await FlowsService.readNodeSource({
            name: flowName,
            nodeId: node.id,
          })
          sources[node.id] = code
        }),
    ).catch(() => undefined)

    // A multi-node copy carries whole Python sources, which can genuinely
    // reach the origin's quota — and a throw from a key handler would take
    // the app down rather than the copy.
    const stored = safeStorage.set(
      CLIPBOARD_KEY,
      JSON.stringify({ nodes: picked, sources } satisfies NodeClipboard),
    )
    if (!stored) {
      notify("That is too much to copy. The browser store is full.", "error")
    }
  }, [canvasNodes, definitions, flowName, selectedId, sourceTypes])

  /**
   * Paste them here, renamed around whatever this flow already holds. The
   * document only names a node's code, so the copy is written per node once
   * the definition is on its way.
   */
  const pasteNodes = useCallback(() => {
    const stored = safeStorage.get(CLIPBOARD_KEY)
    if (!stored) return
    let clipboard: NodeClipboard
    try {
      clipboard = JSON.parse(stored)
    } catch {
      return
    }

    // A node that runs code is a superuser's to add, so anyone else pastes
    // the rest without it.
    const nodes = (clipboard.nodes ?? []).filter(
      (node) => !lockedTypes.has(node.type ?? "python"),
    )
    if (nodes.length < (clipboard.nodes ?? []).length) {
      notify("Only a superuser can add nodes that run code.", "error")
    }

    let pool = definitions
    const pasted: NodeDef_Input[] = []
    for (const node of nodes) {
      const copy = { ...node, id: uniqueNodeId(pool, node.id) }
      pool = [...pool, copy]
      pasted.push(copy)
    }
    if (!pasted.length) return

    setCanvasNodes([
      ...canvasNodes,
      ...pasted.map((node) => ({
        id: node.id,
        type: "flow",
        position: { x: 0, y: 0 },
        data: {},
      })),
    ])
    commit(pool)
    setSelectedId(pasted[pasted.length - 1].id)

    nodes.forEach((node, index) => {
      const code = clipboard.sources?.[node.id]
      if (code !== undefined) {
        sourceMutation.mutate({ nodeId: pasted[index].id, code })
      }
    })
  }, [
    canvasNodes,
    commit,
    definitions,
    lockedTypes,
    setCanvasNodes,
    sourceMutation.mutate,
  ])

  useShortcuts(
    {
      "mod+z": () => step(true),
      "mod+shift+z": () => step(false),
      // Both decline the key unless the node clipboard has something to do
      // with it, so the native copy and paste still work on the canvas. A
      // text selection wins outright: that is what the user asked to copy.
      "mod+c": () => {
        const selection = document.getSelection()
        if (selection && !selection.isCollapsed) return false
        if (!canvasNodes.some((node) => node.selected) && !selectedId) {
          return false
        }
        void copyNodes()
      },
      "mod+v": () => {
        if (!safeStorage.get(CLIPBOARD_KEY)) return false
        pasteNodes()
      },
      // ⌘P, not ⌘K: the sidebar's global search owns that everywhere, and this
      // palette is the canvas's own, narrower thing.
      "mod+p": () => setPaletteOpen((open) => !open),
      // Inside the code editor ⌘S applies that code, which the node panel
      // owns; anywhere else on the canvas it puts the flow live.
      "mod+s": (event) => {
        if (!inCodeEditor(event.target)) void publishFlow()
      },
    },
    // Both stay reachable while typing: one is the editor's own save, the
    // other is how you reach anything at all.
    ["mod+s", "mod+p"],
  )

  return (
    <>
      {/*
       * Grows in from the centre rather than arriving mid-pan, the same
       * entrance the brain view uses. React Flow reads a node's handle bounds
       * out of the DOM once and never again, and a reading taken mid-scale is
       * stored a few percent short for good — `LiveEdge` draws off the
       * `sourceX`/`targetX` that come from those handles, so every edge would
       * land short of its port forever. Remeasuring once the wrapper is back
       * at `scale: 1` is what makes the entrance safe.
       */}
      <motion.div
        variants={scaleIn}
        initial="hidden"
        animate="visible"
        onAnimationComplete={() =>
          updateNodeInternals([
            ...definitions.map((node) => node.id),
            ...external.nodes.map((node) => node.id),
          ])
        }
        className="h-full w-full"
      >
        <ReactFlow
          nodes={shownNodes}
          edges={shownEdges}
          onNodesChange={trackMeasured}
          onEdgesChange={onEdgesChange}
          onNodesDelete={(deleted) =>
            deleteNodes(deleted.filter(isDocumentNode).map((node) => node.id))
          }
          onNodeClick={(event, node) => {
            // An endpoint is somewhere else's: opening its panel here would
            // offer to edit a node this flow does not contain.
            // An input is read where it sits; editing it is one press on.
            const declared = node.id.startsWith("input:")
              ? (flowDoc.inputs ?? []).find(
                  (one) =>
                    `input:${qualify(flowName, one.spec?.name ?? "")}` ===
                    node.id,
                )
              : undefined
            if (declared) {
              const { left, top, width, height } =
                event.currentTarget.getBoundingClientRect()
              setInspectedInput({
                declared,
                rect: { left, top, width, height },
              })
              return
            }
            if (!isDocumentNode(node)) {
              const wire = edges.find(
                (edge) => edge.source === node.id || edge.target === node.id,
              )
              openEndpoint(
                node.id,
                wire && (wire.source === node.id ? wire.target : wire.source),
              )
              return
            }
            setFlowPanelOpen(false)
            setSelectedId(node.id)
          }}
          onPaneClick={() => {
            // Clicking the canvas is how you put a panel away, whichever one it
            // is: the graph is what you went back to look at.
            setSelectedId(null)
            setFlowPanelOpen(false)
            setEditorExpanded(false)
            setInspected(null)
            setInspectedInput(null)
          }}
          onEdgeClick={(event, edge) => {
            const label = (id: string) => {
              const node = definitions.find((entry) => entry.id === id)
              return node?.title || node?.id || id
            }
            setInspected({
              message: (edge.data as { message: string }).message,
              from: label(edge.source),
              to: label(edge.target),
              sourceId: edge.source,
              x: event.clientX,
              y: event.clientY,
            })
          }}
          onConnect={onConnect}
          nodeTypes={nodeTypes}
          edgeTypes={edgeTypes}
          proOptions={{ hideAttribution: true }}
          // React Flow's own defaults, for whatever flow.css does not route
          // through the tokens, follow the theme too.
          colorMode={resolvedTheme}
          fitView
          fitViewOptions={FIT_VIEW}
          // Low enough that the fit can always show the whole graph. A phone is
          // 390px wide and a rank of several nodes is thousands, so a floor of
          // 0.25 left the fit silently short and the flow running off screen.
          minZoom={0.1}
          maxZoom={2}
          // The graph places itself. Nothing here is arranged by hand, which is
          // what keeps a flow small enough to read at a glance.
          nodesDraggable={false}
          connectionRadius={30}
          connectOnClick
          autoPanOnConnect
          edgesReconnectable={false}
          deleteKeyCode={["Backspace", "Delete"]}
          className="h-full w-full"
        >
          <CanvasBackground />
        </ReactFlow>
      </motion.div>

      {/*
       * The bars keep their own lane rather than making way for a panel: they
       * carry Publish, which is what you reach for the moment a node is done.
       * The floating panel is inset out of that lane instead.
       */}
      <div
        className={cn(
          "pointer-events-none absolute inset-0 transition-[right] duration-200",
          panelOpen && !editorExpanded && "md:right-[27rem]",
        )}
      >
        <CanvasTitle
          className={cn(
            "transition-transform duration-200",
            editorExpanded && "-translate-y-[calc(100%+1rem)]",
          )}
        >
          <span className="truncate px-3 py-1.5 text-sm font-medium">
            {flowDoc.title || flowName}
          </span>
          {/* Declared in code somewhere else, at a commit that names what
              actually ran. A dirty tree says so, because then it does not. */}
          {flowDoc.origin ? (
            <span
              className="shrink-0 rounded-full bg-muted px-2 py-0.5 font-mono text-xs text-muted-foreground"
              title={flowDoc.origin.repo || "a repository"}
              data-testid="flow-origin"
            >
              {flowDoc.origin.commit
                ? flowDoc.origin.commit.slice(0, 7)
                : "no commit"}
              {flowDoc.origin.dirty ? "*" : ""}
            </span>
          ) : null}
        </CanvasTitle>

        <FlowDock
          className={cn(
            "transition-transform duration-200",
            editorExpanded && "translate-y-[calc(100%+1rem)]",
          )}
          flow={flowName}
          issues={issues}
          running={runMutation.isPending}
          enabled={detail.enabled ?? true}
          paused={paused}
          saving={saving.isPending}
          hasDraft={detail.has_draft ?? false}
          publishing={publish.isPending || saving.isPending}
          onEditFlow={() => {
            setSelectedId(null)
            setFlowPanelOpen(true)
          }}
          onPublish={() => void publishFlow()}
          onDiscard={() => setDiscardOpen(true)}
          logs={{
            open: logsOpen,
            node: logsNode,
            onOpenChange: (open) => {
              setLogsOpen(open)
              if (!open) setLogsNode(null)
            },
            onClearNode: () => setLogsNode(null),
          }}
          onAddNode={() => setPaletteOpen(true)}
          onRun={startRun}
          onTogglePause={() => pauseMutation.mutate(!paused)}
          onStep={() => stepMutation.mutate()}
          stepping={stepMutation.isPending}
          onFocusNode={focusNode}
        />
      </div>

      {definitions.length === 0 ? (
        <div
          className="pointer-events-none absolute inset-0 flex items-center justify-center"
          data-testid="flow-empty"
        >
          <div className="flex flex-col items-center gap-3 text-center">
            <span className="flex size-14 items-center justify-center rounded-full bg-muted text-muted-foreground">
              <Workflow className="size-6" />
            </span>
            <p className="text-lg font-medium">This flow is empty</p>
            <p className="max-w-xs text-sm text-muted-foreground">
              Add a node to get started. Press ⌘P, or use the plus in the bar
              below.
            </p>
          </div>
        </div>
      ) : null}

      <FlowPanel
        open={flowPanelOpen && !selected}
        definition={flowDoc}
        nodeCount={definitions.length}
        // Confirmed, so it is a finished edit rather than a run of keystrokes.
        onChange={(next) => commitDoc({ ...next, nodes: definitions }, true)}
        onDelete={(withRuns) => deleteMutation.mutate(withRuns)}
        enabled={detail.enabled ?? true}
        toggling={enableMutation.isPending}
        onToggleEnabled={(next) => enableMutation.mutate(next)}
        hasDraft={detail.has_draft ?? false}
        onClose={() => setFlowPanelOpen(false)}
      />

      <NodePanel
        node={selected}
        flow={flowName}
        nodeTypes={nodeTypeInfo ?? []}
        origin={flowDoc.origin}
        suggestions={suggestions}
        expanded={editorExpanded}
        onToggleExpand={() => setEditorExpanded((wide) => !wide)}
        onChange={updateNode}
        onRenameMessage={proposeRename}
        onSaveSource={(code, drop) => {
          if (selected)
            sourceMutation.mutate({ nodeId: selected.id, code, drop })
        }}
        // Sharing rewrites the stored document, so the canvas takes the
        // server's copy rather than keeping its own.
        onShared={onReload}
        onClose={() => {
          flush()
          setEditorExpanded(false)
          setSelectedId(null)
        }}
        onDelete={() => selected && deleteNodes([selected.id])}
      />

      <EdgeInspector
        edge={inspected}
        flow={flowName}
        onClose={() => setInspected(null)}
        onUnbind={unbind}
      />

      <InputInspector
        input={inspectedInput}
        flow={flowName}
        onClose={() => setInspectedInput(null)}
        onEdit={() => {
          setInspectedInput(null)
          setSelectedId(null)
          setFlowPanelOpen(true)
        }}
      />

      <CommandPalette
        open={paletteOpen}
        onOpenChange={setPaletteOpen}
        nodeTypes={(nodeTypeInfo ?? []).filter(
          (info) => !lockedTypes.has(info.type),
        )}
        flows={flows.data}
        onAddNode={addNode}
        onAddSharedNode={
          mayEditCode ? (libName) => addNode("python", libName) : undefined
        }
        onAddDevicePort={addDevicePort}
        onRun={startRun}
      />

      <RunDialog
        open={runOpen}
        definition={flowDoc}
        pending={runMutation.isPending}
        onOpenChange={setRunOpen}
        onRun={(params) => {
          setRunOpen(false)
          runMutation.mutate(params)
        }}
      />

      <Dialog
        open={Boolean(rebind)}
        onOpenChange={(open) => !open && setRebind(null)}
      >
        <DialogContent>
          <DialogHeader>
            <DialogTitle>How should {rebind?.nodeLabel} read this?</DialogTitle>
            <DialogDescription>
              Its "{rebind?.port}" input already reads{" "}
              <span className="font-mono">{rebind?.from}</span>. It can take{" "}
              <span className="font-mono">{rebind?.to}</span> as well, or
              instead.
            </DialogDescription>
          </DialogHeader>
          <DialogFooter className="sm:justify-between">
            <Button variant="ghost" onClick={() => setRebind(null)}>
              Cancel
            </Button>
            <div className="flex gap-2">
              <Button
                variant="outline"
                onClick={() => {
                  if (rebind) {
                    applyBinding(rebind.nodeId, rebind.port, rebind.to)
                  }
                  setRebind(null)
                }}
              >
                Replace
              </Button>
              <Button
                onClick={() => {
                  if (rebind) {
                    addInputPort(rebind.nodeId, rebind.to, rebind.dtype)
                  }
                  setRebind(null)
                }}
              >
                Add as another input
              </Button>
            </div>
          </DialogFooter>
        </DialogContent>
      </Dialog>

      <Dialog
        open={Boolean(renamed)}
        onOpenChange={(open) => !open && setRenamed(null)}
      >
        <DialogContent data-testid="rename-message">
          <DialogHeader>
            <DialogTitle>Rename this message everywhere?</DialogTitle>
            <DialogDescription>
              {renamed?.count === 1
                ? "One other node is"
                : `${renamed?.count} other nodes are`}{" "}
              still bound to <span className="font-mono">{renamed?.from}</span>.
              They keep the old name unless they follow it to{" "}
              <span className="font-mono">{renamed?.to}</span>.
            </DialogDescription>
          </DialogHeader>
          <DialogFooter className="sm:justify-between">
            <Button variant="ghost" onClick={() => setRenamed(null)}>
              Leave them
            </Button>
            <Button onClick={() => renamed && applyRename(renamed)}>
              Rename everywhere
            </Button>
          </DialogFooter>
        </DialogContent>
      </Dialog>

      <DiscardDraftDialog
        open={discardOpen}
        onOpenChange={setDiscardOpen}
        pending={discard.isPending}
        testId="confirm-discard-draft"
        onConfirm={() =>
          discard.mutate(undefined, {
            // The published document replaces what is on the canvas, and
            // the version counter goes back with it.
            onSuccess: () => {
              setFlowPanelOpen(false)
              onReload()
            },
          })
        }
      >
        The canvas goes back to the version the engine is running. What you
        edited since is dropped, though the flow store's git history keeps it.
      </DiscardDraftDialog>

      {/*
       * Not dismissable: until one version wins, every further save fails, so
       * there is nothing useful to go back to.
       */}
      <Dialog open={conflict}>
        <DialogContent
          data-testid="save-conflict"
          showCloseButton={false}
          onEscapeKeyDown={(event) => event.preventDefault()}
          onPointerDownOutside={(event) => event.preventDefault()}
        >
          <DialogHeader>
            <DialogTitle>Someone else changed this flow</DialogTitle>
            <DialogDescription>
              Another editor saved <span className="font-mono">{flowName}</span>{" "}
              while you were working on it. Load their version, or keep yours
              and write over theirs.
            </DialogDescription>
          </DialogHeader>
          <DialogFooter className="sm:justify-between">
            <Button
              variant="ghost"
              onClick={() => {
                void resolveConflict("theirs")
                onReload()
              }}
            >
              Load theirs
            </Button>
            <Button onClick={() => void resolveConflict("mine")}>
              Keep mine
            </Button>
          </DialogFooter>
        </DialogContent>
      </Dialog>
    </>
  )
}

/**
 * Seed xyflow's own node state once. It tracks which nodes exist and which are
 * selected; the positions on it are placeholders the layout replaces at render.
 */
function useUnpositionedNodes(definitions: NodeDef_Input[]) {
  return useNodesState<FlowCanvasNode>(toCanvasNodes(definitions))
}

export function FlowEditor({
  flowName,
  focus,
}: {
  flowName: string
  /** A node or endpoint to arrive on — see `FlowEditorInner`. */
  focus?: string
}) {
  const navigate = useNavigate()
  const onAuthFailure = useCallback(() => {
    navigate({ to: "/login" })
  }, [navigate])
  // Bumped when the canvas has to take the server's document over its own:
  // local edits live in state seeded on mount, so a remount is the reset.
  const [epoch, setEpoch] = useState(0)
  const reload = useCallback(() => setEpoch((n) => n + 1), [])

  useFlowSocket(onAuthFailure)

  return (
    <ReactFlowProvider>
      {/*
       * Remounting per flow keeps canvas state from leaking between them, and
       * it is what makes `fitView` run once per flow: xyflow queues the fit on
       * mount and resolves it as soon as the nodes have been measured.
       * Deliberately not per focused node — that is a selection, not another
       * document, and remounting the canvas on every click in the brain graph
       * would throw an unsaved edit away with it.
       */}
      <FlowEditorInner
        key={`${flowName}:${epoch}`}
        flowName={flowName}
        focus={focus}
        onReload={reload}
      />
    </ReactFlowProvider>
  )
}