app/frontend/src/components/Flow/deriveEdges.ts

import type { Edge } from "@xyflow/react"

import type { MessageSpec, NodeDef_Input } from "@/client"
import type { Route } from "./layout"

/** Resolve a message name against its flow: bare names belong to this flow. */
export function qualify(flow: string, name: string): string {
  if (!name) return ""
  return name.includes(".") ? name : `${flow}.${name}`
}

/**
 * A message named with its flow, as the server checks it wherever a name has
 * to arrive qualified (`QUALIFIED_PATTERN` in `flow/messages.py`).
 */
const QUALIFIED_MESSAGE = /^[a-z][a-z0-9_]*(\.[A-Za-z0-9_]+)+$/

/** What is wrong with a name that has to be qualified, or null. */
export function qualifiedProblem(name: string): string | null {
  return QUALIFIED_MESSAGE.test(name)
    ? null
    : "Name the message as flow.name: a lowercase flow name, a dot, then letters, digits and underscores"
}

/** The flow a qualified message belongs to. */
export function flowOf(message: string): string {
  return message.split(".", 1)[0]
}

/** How a message reads inside its own flow. */
export function displayName(flow: string, message: string): string {
  return message.startsWith(`${flow}.`)
    ? message.slice(flow.length + 1)
    : message
}

export function portOf(spec: MessageSpec): string {
  return spec.port || spec.name?.split(".").pop() || ""
}

export type FlowEdgeData = {
  message: string
  flow: string
  /** Whose publication this edge represents, so only it pulses. */
  producerId: string
  /** The producing port publishes repeatedly during one run, not once at its end. */
  stream?: boolean
  /** How the layout routed it, once it has. */
  route?: Route
  [key: string]: unknown
}

/**
 * Turn name bindings into canvas edges.
 *
 * Nodes never point at each other: a node declares the messages it consumes,
 * and every node providing that message is upstream of it. Two producers of one
 * message therefore draw two edges converging on the same input.
 */
export function deriveEdges(nodes: NodeDef_Input[], flow: string): Edge[] {
  const producers = new Map<
    string,
    { node: string; port: string; stream?: boolean }[]
  >()

  for (const node of nodes) {
    for (const spec of node.provides ?? []) {
      const message = qualify(flow, spec.name ?? "")
      if (!message) continue
      const list = producers.get(message) ?? []
      list.push({ node: node.id, port: portOf(spec), stream: spec.stream })
      producers.set(message, list)
    }
  }

  const edges: Edge[] = []
  for (const node of nodes) {
    for (const spec of node.requires ?? []) {
      const message = qualify(flow, spec.name ?? "")
      if (!message) continue
      const targetPort = portOf(spec)
      for (const producer of producers.get(message) ?? []) {
        if (producer.node === node.id) continue
        edges.push({
          id: `${producer.node}:${producer.port}->${node.id}:${targetPort}`,
          source: producer.node,
          sourceHandle: producer.port,
          target: node.id,
          targetHandle: targetPort,
          type: "live",
          data: {
            message,
            flow,
            producerId: `${flow}.${producer.node}`,
            stream: producer.stream,
          } satisfies FlowEdgeData,
        })
      }
    }
  }
  return edges
}

/**
 * A cheap fingerprint of the flow's boundary — what it takes from outside and,
 * for a batch flow, what it reports — since those are drawn like wiring too.
 */
export function boundaryKey(doc: {
  mode?: string | null
  inputs?: { spec?: MessageSpec | null; origin?: string }[] | null
  outputs?: string[] | null
}): string {
  const inputs = (doc.inputs ?? [])
    .map(
      (one) =>
        `${one.spec?.name ?? ""}:${one.spec?.dtype ?? ""}:${one.origin ?? ""}`,
    )
    .join(",")
  return `${doc.mode ?? "live"}|${inputs}|${(doc.outputs ?? []).join(",")}`
}

/**
 * A cheap fingerprint of everything edges depend on, so dragging a node (which
 * replaces the array every frame) does not re-derive them.
 */
export function bindingsKey(nodes: NodeDef_Input[]): string {
  return nodes
    .map(
      (node) =>
        `${node.id}|${(node.requires ?? [])
          .map((s) => `${portOf(s)}=${s.name ?? ""}`)
          .join(",")}|${(node.provides ?? [])
          .map((s) => `${portOf(s)}=${s.name ?? ""}${s.stream ? "*" : ""}`)
          .join(",")}`,
    )
    .join(";")
}