import { create } from 'zustand'
import { persist } from 'zustand/middleware'
import type { BookingImportPreviewItem, BookingImportMode, ReceiptRead } from '@trek/shared'

/**
 * Tracks booking-import parses that run in the BACKGROUND (the async endpoint).
 * The upload modal closes the moment a parse starts and adds a task here; the
 * server pushes import:progress / import:done / import:error over the user's
 * WebSocket (which reaches every page), and the global BackgroundTasksWidget
 * renders the list. The trip page turns a finished task into the review flow.
 *
 * Persisted (minimal): the server keeps the job for ~10 min and exposes a status
 * endpoint, so a reload mid-parse must NOT drop the widget — we persist the running
 * (and finished-but-unreviewed) tasks by id and the widget re-fetches their status
 * on mount. We deliberately persist neither the parsed `items` (re-fetched) nor the
 * transient review flags (so a reload never auto-reopens the review flow).
 */
export type BackgroundTaskKind = 'transports' | 'bookings' | 'costs'

export interface BackgroundImportTask {
  id: string                 // server job id
  tripId: string
  label: string              // file name(s) being parsed
  status: 'running' | 'done' | 'error'
  done: number
  total: number
  items?: BookingImportPreviewItem[]
  /** A receipt scanned from Costs (`kind: 'costs'`): what the model read, or null when it read nothing. */
  receipt?: ReceiptRead | null
  warnings?: string[]
  error?: string
  reviewRequested?: boolean  // user clicked "review" — the trip page consumes it
  consumed?: boolean         // review has been handed to the trip page
  /** The uploaded files this parse ran on — kept in memory so the review can attach the
   *  source document to each created booking. Not persisted (a File can't survive a reload). */
  sourceFiles?: File[]
  /** Mode this run used — the widget only offers an AI retry if it wasn't already one. Not persisted. */
  mode?: BookingImportMode
  /**
   * Which tab the import was started from. It decides which form an item opens
   * when its type is guessed (#2076), and unlike the other transient flags it IS
   * persisted: the parse deliberately outlives navigation and reload, and the
   * review is triggered by the global widget on any page, so a component-local
   * value is gone by the time it is needed. `costs` is a receipt scan, reviewed
   * in the expense editor instead of the booking forms.
   */
  kind?: BackgroundTaskKind
}

interface BackgroundTasksState {
  tasks: BackgroundImportTask[]
  addTask: (task: { id: string; tripId: string; label: string; total: number; files?: File[]; mode?: BookingImportMode; kind?: BackgroundTaskKind }) => void
  setProgress: (id: string, tripId: string, done: number, total: number) => void
  setDone: (id: string, tripId: string, items: BookingImportPreviewItem[], warnings: string[], receipt?: ReceiptRead | null) => void
  setError: (id: string, tripId: string, error: string) => void
  requestReview: (id: string) => void
  markConsumed: (id: string) => void
  dismiss: (id: string) => void
}

export const useBackgroundTasksStore = create<BackgroundTasksState>()(
  persist(
    (set) => {
      /** Update an existing task by id, or insert a fresh one (events can arrive before addTask). */
      const upsert = (id: string, tripId: string, patch: Partial<BackgroundImportTask>) =>
        set((state) => {
          const idx = state.tasks.findIndex((t) => t.id === id)
          if (idx === -1) {
            const base: BackgroundImportTask = { id, tripId, label: 'Import', status: 'running', done: 0, total: 1 }
            return { tasks: [...state.tasks, { ...base, ...patch }] }
          }
          const tasks = state.tasks.slice()
          tasks[idx] = { ...tasks[idx], ...patch }
          return { tasks }
        })

      return {
        tasks: [],
        addTask: ({ id, tripId, label, total, files, mode, kind }) => upsert(id, tripId, { label, total, status: 'running', done: 0, sourceFiles: files, mode, kind }),
        setProgress: (id, tripId, done, total) => upsert(id, tripId, { done, total, status: 'running' }),
        setDone: (id, tripId, items, warnings, receipt) => upsert(id, tripId, { status: 'done', items, warnings, receipt, done: items?.length ?? 0 }),
        setError: (id, tripId, error) => upsert(id, tripId, { status: 'error', error }),
        requestReview: (id) => set((s) => ({ tasks: s.tasks.map((t) => (t.id === id ? { ...t, reviewRequested: true } : t)) })),
        markConsumed: (id) => set((s) => ({ tasks: s.tasks.map((t) => (t.id === id ? { ...t, consumed: true, reviewRequested: false } : t)) })),
        dismiss: (id) => set((s) => ({ tasks: s.tasks.filter((t) => t.id !== id) })),
      }
    },
    {
      name: 'trek.bg-import-tasks',
      // Persist only what survives a reload usefully: the job id/trip/label and a coarse
      // status. The widget re-fetches each job's real status (and parsed items) on mount,
      // so we keep neither the heavy `items`/`warnings` nor the transient review flags —
      // that also guarantees a reload never re-opens the review flow on its own.
      partialize: (state) => ({
        tasks: state.tasks
          .filter((t) => !t.consumed && t.status !== 'error')
          // `kind` rides along: it is not a review flag but the context the review
          // needs, and without it a reload silently falls back to 'bookings'.
          .map((t) => ({ id: t.id, tripId: t.tripId, label: t.label, status: t.status, done: t.done, total: t.total, kind: t.kind })),
      }),
    },
  ),
)

/** Whether a finished task has something to review: a read receipt, or at least one booking. */
export function taskFoundSomething(task: BackgroundImportTask): boolean {
  return task.kind === 'costs' ? Boolean(task.receipt) : (task.items?.length ?? 0) > 0
}