import type { Clock, Fs } from './io'
import { readJson, writeJson } from './io'

export interface Todo {
  id: number
  title: string
  done: boolean
  /** 承諾事項：助理答應記住的事 */
  promise: boolean
  dueAt?: number
  createdAt: number
  doneAt?: number
  /** 已提醒過，避免重複 */
  reminded?: boolean
}

export interface TodoList {
  add(title: string, opts?: { promise?: boolean; dueAt?: number }): Promise<Todo>
  complete(id: number): Promise<Todo | null>
  list(opts?: { all?: boolean }): Promise<Todo[]>
  /** 角色行顯示的待辦數（未完成） */
  open(): Promise<number>
  /** 取出到期且尚未提醒的項目，並標記為已提醒 */
  due(): Promise<Todo[]>
}

export function createTodos(fs: Fs, clock: Clock, path: string): TodoList {
  const load = () => readJson<Todo[]>(fs, path, [])
  const save = (t: Todo[]) => writeJson(fs, path, t)
  return {
    async add(title, opts = {}) {
      const all = await load()
      const t: Todo = {
        id: all.reduce((m, x) => Math.max(m, x.id), 0) + 1,
        title: title.trim(),
        done: false,
        promise: !!opts.promise,
        dueAt: opts.dueAt,
        createdAt: clock(),
      }
      all.push(t)
      await save(all)
      return t
    },
    async complete(id) {
      const all = await load()
      const t = all.find(x => x.id === id)
      if (!t || t.done) return t ?? null
      t.done = true
      t.doneAt = clock()
      await save(all)
      return t
    },
    async list(opts = {}) {
      const all = await load()
      return opts.all ? all : all.filter(t => !t.done)
    },
    async open() {
      return (await load()).filter(t => !t.done).length
    },
    async due() {
      const all = await load()
      const now = clock()
      const hit = all.filter(t => !t.done && !t.reminded && t.dueAt !== undefined && t.dueAt <= now)
      if (hit.length) {
        for (const t of hit) t.reminded = true
        await save(all)
      }
      return hit
    },
  }
}