/**
 * Settings Service — 读写用户级和项目级设置文件
 *
 * 设置文件为 JSON 格式：
 *   - 用户级: ~/.claude/settings.json
 *   - 项目级: {projectRoot}/.claude/settings.json
 *
 * 合并策略：Object.assign({}, userSettings, projectSettings)
 */

import * as fs from 'fs/promises'
import * as path from 'path'
import * as os from 'os'
import { ApiError } from '../middleware/errorHandler.js'

const VALID_PERMISSION_MODES = [
  'default',
  'acceptEdits',
  'plan',
  'bypassPermissions',
  'dontAsk',
] as const

export type PermissionMode = (typeof VALID_PERMISSION_MODES)[number]

export class SettingsService {
  private projectRoot?: string

  constructor(projectRoot?: string) {
    this.projectRoot = projectRoot
  }

  /** 配置目录，支持通过环境变量覆盖（便于测试） */
  private getConfigDir(): string {
    return process.env.CLAUDE_CONFIG_DIR || path.join(os.homedir(), '.claude')
  }

  /** 用户级设置文件路径 */
  private getUserSettingsPath(): string {
    return path.join(this.getConfigDir(), 'settings.json')
  }

  /** 项目级设置文件路径 */
  private getProjectSettingsPath(projectRoot?: string): string {
    const root = projectRoot || this.projectRoot
    if (!root) {
      throw ApiError.badRequest('Project root is required for project settings')
    }
    return path.join(root, '.claude', 'settings.json')
  }

  // ---------------------------------------------------------------------------
  // 读取
  // ---------------------------------------------------------------------------

  /** 安全读取 JSON 文件，文件不存在时返回空对象 */
  private async readJsonFile(filePath: string): Promise<Record<string, unknown>> {
    try {
      const raw = await fs.readFile(filePath, 'utf-8')
      return JSON.parse(raw) as Record<string, unknown>
    } catch (err: unknown) {
      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
        return {}
      }
      throw ApiError.internal(`Failed to read settings from ${filePath}: ${err}`)
    }
  }

  /** 获取合并后的设置（user + project） */
  async getSettings(projectRoot?: string): Promise<Record<string, unknown>> {
    const user = await this.getUserSettings()
    try {
      const project = await this.getProjectSettings(projectRoot)
      return Object.assign({}, user, project)
    } catch {
      // project root 未指定时，仅返回 user settings
      return user
    }
  }

  /** 获取用户级设置 */
  async getUserSettings(): Promise<Record<string, unknown>> {
    return this.readJsonFile(this.getUserSettingsPath())
  }

  /** 获取项目级设置 */
  async getProjectSettings(projectRoot?: string): Promise<Record<string, unknown>> {
    return this.readJsonFile(this.getProjectSettingsPath(projectRoot))
  }

  // ---------------------------------------------------------------------------
  // 写入（原子写入：先写临时文件，再 rename）
  // ---------------------------------------------------------------------------

  /** 原子写入 JSON 文件 */
  private async writeJsonFile(
    filePath: string,
    data: Record<string, unknown>,
  ): Promise<void> {
    const dir = path.dirname(filePath)
    await fs.mkdir(dir, { recursive: true })

    const tmpFile = `${filePath}.tmp.${Date.now()}`
    try {
      await fs.writeFile(tmpFile, JSON.stringify(data, null, 2) + '\n', 'utf-8')
      await fs.rename(tmpFile, filePath)
    } catch (err) {
      // 清理临时文件（best-effort）
      await fs.unlink(tmpFile).catch(() => {})
      throw ApiError.internal(`Failed to write settings to ${filePath}: ${err}`)
    }
  }

  /** 更新用户级设置（浅合并） */
  async updateUserSettings(settings: Record<string, unknown>): Promise<void> {
    const current = await this.getUserSettings()
    const merged = Object.assign({}, current, settings)
    await this.writeJsonFile(this.getUserSettingsPath(), merged)
  }

  /** 更新项目级设置（浅合并） */
  async updateProjectSettings(
    settings: Record<string, unknown>,
    projectRoot?: string,
  ): Promise<void> {
    const filePath = this.getProjectSettingsPath(projectRoot)
    const current = await this.readJsonFile(filePath)
    const merged = Object.assign({}, current, settings)
    await this.writeJsonFile(filePath, merged)
  }

  // ---------------------------------------------------------------------------
  // 权限模式
  // ---------------------------------------------------------------------------

  /** 获取当前权限模式 */
  async getPermissionMode(): Promise<string> {
    const settings = await this.getUserSettings()
    return (settings.defaultMode as string) || 'default'
  }

  /** 设置权限模式 */
  async setPermissionMode(mode: string): Promise<void> {
    if (!VALID_PERMISSION_MODES.includes(mode as PermissionMode)) {
      throw ApiError.badRequest(
        `Invalid permission mode: "${mode}". Valid modes: ${VALID_PERMISSION_MODES.join(', ')}`,
      )
    }
    await this.updateUserSettings({ defaultMode: mode })
  }
}