import type { FastifyError, FastifyReply, FastifyRequest } from 'fastify'

export type ErrorCode =
  | 'VALIDATION_ERROR'
  | 'NOT_FOUND'
  | 'CONFLICT'
  | 'AI_NOT_CONFIGURED'
  | 'INTERNAL_ERROR'

/** 业务错误：handlers / services 抛出，统一转换为约定的错误响应格式 */
export class ApiError extends Error {
  constructor(
    readonly statusCode: number,
    readonly code: ErrorCode,
    message: string,
    readonly details: { path: string; message: string }[] = []
  ) {
    super(message)
    this.name = 'ApiError'
  }

  static notFound(message: string, details?: { path: string; message: string }[]) {
    return new ApiError(404, 'NOT_FOUND', message, details)
  }

  static conflict(message: string, details?: { path: string; message: string }[]) {
    return new ApiError(409, 'CONFLICT', message, details)
  }

  static aiNotConfigured(message: string) {
    return new ApiError(503, 'AI_NOT_CONFIGURED', message)
  }
}

function sendError(reply: FastifyReply, statusCode: number, code: ErrorCode, message: string, details: { path: string; message: string }[] = []) {
  return reply.status(statusCode).send({ error: { code, message, details } })
}

/** 将 AJV 校验信息翻译为可读中文 */
function translateAjvMessage(message: string): string {
  if (/must have required property/.test(message)) {
    const prop = message.match(/'([^']+)'/)?.[1] ?? ''
    return `缺少必填字段 ${prop}`
  }
  if (message === 'must be equal to one of the allowed values') return '取值必须是允许的枚举值之一'
  if (message === 'must be string') return '类型应为字符串'
  if (message === 'must be number') return '类型应为数字'
  if (message === 'must be integer') return '应为整数'
  if (message === 'must be boolean') return '应为布尔值'
  if (message === 'must be array') return '应为数组'
  if (message === 'must be object') return '应为对象'
  if (message === 'must match a schema in anyOf') return '取值不符合预设选项'
  return message
}

/**
 * 聚合同一路径下的多条校验信息：
 * Zod union（如 duration: 5|10|15）经 AJV anyOf 校验失败时会产生
 * 多条 "must be equal to constant" + 一条 "must match a schema in anyOf"，
 * 按路径合并为一条可读信息。
 */
function consolidateDetails(items: { path: string; message: string }[]): { path: string; message: string }[] {
  const byPath = new Map<string, { path: string; message: string }[]>()
  for (const item of items) {
    const list = byPath.get(item.path) ?? []
    list.push(item)
    byPath.set(item.path, list)
  }
  const result: { path: string; message: string }[] = []
  for (const [path, list] of byPath) {
    const constFailures = list.filter((i) => i.message === 'must be equal to constant')
    const anyOfFailure = list.some((i) => i.message === 'must match a schema in anyOf')
    if (anyOfFailure) {
      result.push({ path, message: '取值不符合预设选项' })
      continue
    }
    if (constFailures.length > 0 && list.length === constFailures.length) {
      result.push({ path, message: '取值不符合预设选项' })
      continue
    }
    const seen = new Set<string>()
    for (const item of list) {
      const msg = translateAjvMessage(item.message)
      if (!seen.has(msg)) {
        seen.add(msg)
        result.push({ path, message: msg })
      }
    }
  }
  return result
}
export function errorHandler(error: FastifyError | ApiError | Error, request: FastifyRequest, reply: FastifyReply) {
  if (error instanceof ApiError) {
    return sendError(reply, error.statusCode, error.code, error.message, error.details)
  }

  const fastifyError = error as FastifyError
  if (fastifyError.validation || fastifyError.statusCode === 400) {
    if (!fastifyError.validation) {
      // 非 AJV 的 400（如 JSON body 解析失败），直接透出可理解的原因
      return sendError(reply, 400, 'VALIDATION_ERROR', fastifyError.message || '请求参数不合法', [])
    }
    const details = consolidateDetails(
      fastifyError.validation.map((item) => ({
        path: item.instancePath.replace(/^\//, '') || (item.params as { missingProperty?: string })?.missingProperty || '',
        message: item.message ?? '参数不合法'
      }))
    )
    return sendError(reply, 400, 'VALIDATION_ERROR', '请求参数不合法', details)
  }

  request.log.error({ err: error }, '未处理异常')
  return sendError(reply, 500, 'INTERNAL_ERROR', '服务器内部错误')
}

export function notFoundHandler(request: FastifyRequest, reply: FastifyReply) {
  return sendError(reply, 404, 'NOT_FOUND', `接口不存在：${request.method} ${request.url}`)
}