import { Link, type LinkProps } from "@tanstack/react-router"
import { Check, type LucideIcon } from "lucide-react"
import { type ReactNode, useEffect, useRef, useState } from "react"

import { cn } from "@/lib/utils"

/** How long a press has to last before it means "select this one". */
const LONG_PRESS = 450

/**
 * Which of the listed documents are picked, and what turns picking on.
 *
 * Selection mode is simply "something is selected": a long press picks the
 * first one and clearing the last one puts the list back to normal. So there
 * is no mode to be stuck in, nothing to cancel, and no control on screen that
 * exists only to turn selecting on.
 *
 * @param names everything currently listed. A document that is deleted, or
 *   filtered out by the search, cannot stay picked — deleting therefore clears
 *   the selection on its own, once the list comes back without it.
 */
export function useSelection(names: string[]) {
  const [picked, setPicked] = useState<string[]>([])
  const selected = picked.filter((name) => names.includes(name))

  // Escape is the way out for anyone who started this by accident.
  useEffect(() => {
    if (selected.length === 0) return
    const onKey = (event: KeyboardEvent) => {
      if (event.key === "Escape") setPicked([])
    }
    window.addEventListener("keydown", onKey)
    return () => window.removeEventListener("keydown", onKey)
  }, [selected.length])

  return {
    selected,
    selecting: selected.length > 0,
    toggle: (name: string) =>
      setPicked((current) =>
        current.includes(name)
          ? current.filter((other) => other !== name)
          : [...current, name],
      ),
    clear: () => setPicked([]),
  }
}

/**
 * One entry of the flows or dashboards overview.
 *
 * Stays a link in both modes rather than swapping element: while selecting it
 * carries `role="checkbox"` instead, which is what it now behaves as. Ctrl or
 * Cmd click is the same gesture for a mouse, and reaches the keyboard for
 * free — a focused link answers Ctrl+Enter with a click carrying the modifier.
 */
export function OverviewCard({
  link,
  icon: Icon,
  title,
  detail,
  draft,
  selecting,
  selected,
  onToggle,
  testId,
}: {
  link: LinkProps
  icon: LucideIcon
  title: ReactNode
  detail: ReactNode
  /** Has unpublished changes. */
  draft?: boolean
  selecting: boolean
  selected: boolean
  onToggle: () => void
  testId?: string
}) {
  const timer = useRef<ReturnType<typeof setTimeout> | null>(null)
  const held = useRef(false)

  const stop = () => {
    if (timer.current) clearTimeout(timer.current)
    timer.current = null
  }

  return (
    <Link
      {...link}
      data-testid={testId}
      data-selected={selected || undefined}
      role={selecting ? "checkbox" : undefined}
      aria-checked={selecting ? selected : undefined}
      className={cn(
        "relative grid gap-1 rounded-lg border border-border bg-card p-4 shadow-e1 transition-colors",
        // Both states have to stay tellable apart, so hover is the half tint.
        selected ? "border-primary bg-accent" : "hover:bg-accent/50",
        selecting && "select-none",
      )}
      onPointerDown={(event) => {
        // Right-click is the browser's own gesture; leave it alone.
        if (event.button !== 0) return
        held.current = false
        timer.current = setTimeout(() => {
          held.current = true
          onToggle()
        }, LONG_PRESS)
      }}
      onPointerUp={stop}
      onPointerLeave={stop}
      onPointerCancel={stop}
      onClick={(event) => {
        // The press already picked it; the click that ends the press must not
        // undo it, and must certainly not navigate.
        if (held.current) {
          held.current = false
          event.preventDefault()
          return
        }
        if (selecting || event.ctrlKey || event.metaKey) {
          event.preventDefault()
          onToggle()
        }
      }}
      onContextMenu={(event) => {
        // A touch hold raises this a moment after the press has been taken as
        // a selection; the link preview on top of it would be a second answer
        // to one gesture.
        if (held.current) event.preventDefault()
      }}
    >
      <span className="flex items-center gap-2">
        <Icon className="size-4 shrink-0 text-muted-foreground" />
        <span className="truncate">{title}</span>
        {draft ? (
          <span className="size-1.5 shrink-0 rounded-full bg-primary">
            <span className="sr-only">Unpublished changes</span>
          </span>
        ) : null}
      </span>
      <span className="truncate text-sm text-muted-foreground">{detail}</span>

      {selecting ? (
        <span
          aria-hidden
          className={cn(
            "absolute top-3 right-3 flex size-5 items-center justify-center rounded-sm border",
            selected
              ? "border-primary bg-primary text-primary-foreground"
              : "border-border bg-card",
          )}
        >
          {selected ? <Check className="size-3.5" /> : null}
        </span>
      ) : null}
    </Link>
  )
}