import fs from 'fs/promises'
import path from 'path'
import { resolveNotebookPath } from '../../utils/pathSafety.js'
import { NotFoundError } from '../../../shared/errors/index.js'
import { parseTodoContent, generateTodoContent } from './parser.js'
import type { DayTodo, TodoFilePath, ParsedTodoFile, GetTodoResult } from './types.js'

export interface TodoServiceDependencies {
}

export class TodoService {
  constructor(private deps: TodoServiceDependencies = {}) {}

  getTodoFilePath(year: number, month: number): TodoFilePath {
    const yearStr = year.toString()
    const monthStr = month.toString().padStart(2, '0')
    const relPath = `TODO/${yearStr}/${yearStr}${monthStr}TODO.md`
    const { fullPath } = resolveNotebookPath(relPath)
    return { relPath, fullPath }
  }

  async ensureTodoFileExists(fullPath: string): Promise<void> {
    const dir = path.dirname(fullPath)
    await fs.mkdir(dir, { recursive: true })
    try {
      await fs.access(fullPath)
    } catch {
      await fs.writeFile(fullPath, '', 'utf-8')
    }
  }

  async loadAndParseTodoFile(year: number, month: number): Promise<ParsedTodoFile> {
    const { fullPath } = this.getTodoFilePath(year, month)
    try {
      await fs.access(fullPath)
    } catch {
      throw new NotFoundError('TODO file not found')
    }
    const content = await fs.readFile(fullPath, 'utf-8')
    return { fullPath, dayTodos: parseTodoContent(content) }
  }

  async saveTodoFile(fullPath: string, dayTodos: DayTodo[]): Promise<void> {
    const content = generateTodoContent(dayTodos)
    await fs.writeFile(fullPath, content, 'utf-8')
  }

  async getTodo(year: number, month: number): Promise<GetTodoResult> {
    const { fullPath } = this.getTodoFilePath(year, month)

    let dayTodos: DayTodo[] = []
    try {
      await fs.access(fullPath)
      const content = await fs.readFile(fullPath, 'utf-8')
      dayTodos = parseTodoContent(content)
    } catch {
      // 文件不存在
    }

    const now = new Date()
    const todayStr = `${now.getFullYear()}-${(now.getMonth() + 1).toString().padStart(2, '0')}-${now.getDate().toString().padStart(2, '0')}`

    const yesterday = new Date(now)
    yesterday.setDate(yesterday.getDate() - 1)
    const yesterdayStr = `${yesterday.getFullYear()}-${(yesterday.getMonth() + 1).toString().padStart(2, '0')}-${yesterday.getDate().toString().padStart(2, '0')}`

    if (year === now.getFullYear() && month === now.getMonth() + 1) {
      const migrated = this.migrateIncompleteItems(dayTodos, todayStr, yesterdayStr)

      if (migrated) {
        const newContent = generateTodoContent(dayTodos)
        await this.ensureTodoFileExists(fullPath)
        await fs.writeFile(fullPath, newContent, 'utf-8')
      }
    }

    return { dayTodos, year, month }
  }

  private migrateIncompleteItems(dayTodos: DayTodo[], todayStr: string, yesterdayStr: string): boolean {
    let migrated = false

    const yesterdayTodo = dayTodos.find(d => d.date === yesterdayStr)
    if (yesterdayTodo) {
      const incompleteItems = yesterdayTodo.items.filter(item => !item.completed)
      if (incompleteItems.length > 0) {
        const todayTodo = dayTodos.find(d => d.date === todayStr)
        if (todayTodo) {
          const existingIds = new Set(todayTodo.items.map(i => i.id))
          const itemsToAdd = incompleteItems.map((item, idx) => ({
            ...item,
            id: existingIds.has(item.id) ? `${todayStr}-migrated-${idx}` : item.id
          }))
          todayTodo.items = [...itemsToAdd, ...todayTodo.items]
        } else {
          dayTodos.push({
            date: todayStr,
            items: incompleteItems.map((item, idx) => ({
              ...item,
              id: `${todayStr}-migrated-${idx}`
            }))
          })
        }

        yesterdayTodo.items = yesterdayTodo.items.filter(item => item.completed)
        if (yesterdayTodo.items.length === 0) {
          const index = dayTodos.findIndex(d => d.date === yesterdayStr)
          if (index !== -1) {
            dayTodos.splice(index, 1)
          }
        }

        migrated = true
      }
    }

    return migrated
  }

  async saveTodo(year: number, month: number, dayTodos: DayTodo[]): Promise<void> {
    const { fullPath } = this.getTodoFilePath(year, month)
    await this.ensureTodoFileExists(fullPath)
    const content = generateTodoContent(dayTodos)
    await fs.writeFile(fullPath, content, 'utf-8')
  }

  async addTodo(year: number, month: number, date: string, todoContent: string): Promise<DayTodo[]> {
    const { fullPath } = this.getTodoFilePath(year, month)
    await this.ensureTodoFileExists(fullPath)

    let fileContent = await fs.readFile(fullPath, 'utf-8')
    const dayTodos = parseTodoContent(fileContent)

    const existingDay = dayTodos.find(d => d.date === date)
    if (existingDay) {
      const newId = `${date}-${existingDay.items.length}`
      existingDay.items.push({
        id: newId,
        content: todoContent,
        completed: false
      })
    } else {
      dayTodos.push({
        date,
        items: [{
          id: `${date}-0`,
          content: todoContent,
          completed: false
        }]
      })
    }

    fileContent = generateTodoContent(dayTodos)
    await fs.writeFile(fullPath, fileContent, 'utf-8')

    return dayTodos
  }

  async toggleTodo(year: number, month: number, date: string, itemIndex: number, completed: boolean): Promise<DayTodo[]> {
    const { fullPath, dayTodos } = await this.loadAndParseTodoFile(year, month)

    const day = dayTodos.find(d => d.date === date)
    if (!day || itemIndex >= day.items.length) {
      throw new NotFoundError('TODO item not found')
    }

    day.items[itemIndex].completed = completed

    await this.saveTodoFile(fullPath, dayTodos)

    return dayTodos
  }

  async updateTodo(year: number, month: number, date: string, itemIndex: number, newContent: string): Promise<DayTodo[]> {
    const { fullPath, dayTodos } = await this.loadAndParseTodoFile(year, month)

    const day = dayTodos.find(d => d.date === date)
    if (!day || itemIndex >= day.items.length) {
      throw new NotFoundError('TODO item not found')
    }

    day.items[itemIndex].content = newContent

    await this.saveTodoFile(fullPath, dayTodos)

    return dayTodos
  }

  async deleteTodo(year: number, month: number, date: string, itemIndex: number): Promise<DayTodo[]> {
    const { fullPath, dayTodos } = await this.loadAndParseTodoFile(year, month)

    const dayIndex = dayTodos.findIndex(d => d.date === date)
    if (dayIndex === -1) {
      throw new NotFoundError('Day not found')
    }

    const day = dayTodos[dayIndex]
    if (itemIndex >= day.items.length) {
      throw new NotFoundError('TODO item not found')
    }

    day.items.splice(itemIndex, 1)

    if (day.items.length === 0) {
      dayTodos.splice(dayIndex, 1)
    }

    await this.saveTodoFile(fullPath, dayTodos)

    return dayTodos
  }
}

export const createTodoService = (deps?: TodoServiceDependencies): TodoService => {
  return new TodoService(deps)
}