import { useEffect, useRef, useState } from 'react'
import type { Card, ClientMessage, GameView, PlayerView } from '../types'
import { CardView } from './CardView'

interface Props {
  view: GameView
  you: PlayerView
  send: (msg: ClientMessage) => void
}

// ArrangePhase lets the player order their deck for battle. Rightmost card
// fights first; food cards buff the next pet to their left... i.e. foods
// apply to the next pet later in the play order. Internally `order` stays in
// play order (index 0 fights first) to match the backend; we only reverse for
// display. Drag cards or use the arrow buttons to reorder, then lock in.
export function ArrangePhase({ view, you, send }: Props) {
  const [order, setOrder] = useState<Card[]>(you.deck ?? [])
  const dragIndex = useRef<number | null>(null)
  const [dragging, setDragging] = useState(false)
  const locked = you.ready

  // Resync only if the deck's actual contents changed — every broadcast
  // creates a fresh array, and blindly resetting would wipe an in-progress
  // ordering whenever the opponent acts.
  useEffect(() => {
    setOrder((prev) => {
      const deck = you.deck ?? []
      const ids = new Set(deck.map((c) => c.id))
      if (prev.length === deck.length && prev.every((c) => ids.has(c.id))) {
        return prev
      }
      return deck
    })
  }, [you.deck])

  function move(from: number, to: number) {
    if (to < 0 || to >= order.length) return
    setOrder((o) => {
      const next = [...o]
      const [c] = next.splice(from, 1)
      next.splice(to, 0, c)
      return next
    })
  }

  // Which pets do the foods land on? Compute buff per card for preview.
  const bonuses = new Map<string, number>()
  {
    let pendingApples = 0
    for (const c of order) {
      if (c.kind === 'food') {
        if (c.food === 'apple') pendingApples++
      } else {
        bonuses.set(c.id, pendingApples)
        pendingApples = 0
      }
    }
  }
  const trailingFoods = (() => {
    let n = 0
    for (let i = order.length - 1; i >= 0 && order[i].kind === 'food'; i--) n++
    return n
  })()

  const opponent = view.players.find((p) => p.seat !== view.youSeat)

  if (locked) {
    return (
      <div className="centered">
        <h2>Order locked in ⚔️</h2>
        <p className="muted">
          Waiting for {opponent?.name ?? 'your opponent'} to arrange their deck…
        </p>
      </div>
    )
  }

  return (
    <div className="arrange">
      <div className="shop-status">
        <span className="status-hot">Arrange your battle line</span>
      </div>
      <p className="hint">
        The <strong>rightmost</strong> card fights first. Food cards power up the
        next pet to their <strong>left</strong>.
        {trailingFoods > 0 && (
          <span className="warn-text">
            {' '}
            ⚠️ {trailingFoods} food card{trailingFoods > 1 ? 's' : ''} on the far
            left will be wasted!
          </span>
        )}
      </p>

      <div className="arrange-row">
        {order
          .map((c, i) => ({ c, i }))
          .reverse()
          .map(({ c, i }) => (
            <div
              key={c.id}
              className="arrange-card"
              draggable
              onDragStart={() => {
                dragIndex.current = i
                setDragging(true)
              }}
              onDragOver={(e) => {
                e.preventDefault()
                if (dragIndex.current !== null && dragIndex.current !== i) {
                  move(dragIndex.current, i)
                  dragIndex.current = i
                }
              }}
              onDragEnd={() => {
                dragIndex.current = null
                setDragging(false)
              }}
            >
              <CardView card={c} bonus={bonuses.get(c.id) ?? 0} noMagnify={dragging} />
              <div className="arrange-arrows">
                <button
                  className="btn btn-ghost btn-sm"
                  disabled={i === order.length - 1}
                  onClick={() => move(i, i + 1)}
                  aria-label="move left"
                >
                  ◀
                </button>
                <button
                  className="btn btn-ghost btn-sm"
                  disabled={i === 0}
                  onClick={() => move(i, i - 1)}
                  aria-label="move right"
                >
                  ▶
                </button>
              </div>
            </div>
          ))}
        <div className="arrange-marker">⚔️ first</div>
      </div>

      <div className="actions">
        <button
          className="btn btn-primary btn-big"
          onClick={() => send({ type: 'arrange', order: order.map((c) => c.id) })}
        >
          Lock in & battle ⚔️
        </button>
      </div>
    </div>
  )
}