import { createLogger } from "@/lib/observability/logger";
import { NextResponse } from "next/server";
import { getRequestErrorMessage } from "@/lib/request-error";
import { generateUUID } from "@/lib/utils";

const chatApiLogger = createLogger("chat.errors");


const DEFAULT_CHAT_PRE_RESPONSE_SOFT_TIMEOUT_MS = 55_000;

export class OperationTimeoutError extends Error {
  constructor(operation: string, timeoutMs: number) {
    super(`${operation} timed out after ${timeoutMs}ms`);
    this.name = "OperationTimeoutError";
  }
}

export function getChatStreamErrorMessage(error: unknown): string {
  const rawMessage =
    error instanceof Error ? String(error.message || "").trim() : String(error || "").trim();
  const normalized = rawMessage.toLowerCase();

  if (
    normalized.includes("token quota is not enough") ||
    normalized.includes("pre_consume_token_quota_failed") ||
    normalized.includes("quota is not enough")
  ) {
    return "当前对话模型额度不足，请切换其他模型，或联系管理员补充该模型额度。";
  }

  if (
    normalized.includes("timeout") ||
    normalized.includes("timed out") ||
    normalized.includes("body timeout")
  ) {
    return "当前对话模型响应超时，请重试，或切换到其他可用模型。";
  }

  if (rawMessage) {
    return `当前对话暂时失败：${rawMessage}`;
  }

  return "当前对话暂时失败，请重试或切换其他模型。";
}

function resolveChatApiFailure(error: unknown) {
  const detailMessage = getRequestErrorMessage(error);
  const normalized = String(detailMessage || "").toLowerCase();

  if (
    normalized.includes("payload too large") ||
    normalized.includes("request entity too large") ||
    normalized.includes("body exceeded") ||
    normalized.includes("content length") ||
    normalized.includes("413")
  ) {
    return {
      code: "payload_too_large:chat",
      message: "本次请求内容过大，请减少图片或文字内容后重试。",
      status: 413,
      category: "payload_too_large",
      detailMessage,
    };
  }

  if (
    error instanceof OperationTimeoutError ||
    normalized.includes("timeout") ||
    normalized.includes("timed out") ||
    normalized.includes("body timeout") ||
    normalized.includes("aborterror") ||
    normalized.includes("aborted")
  ) {
    return {
      code: "timeout:chat",
      message: "当前模型响应超时，请重试，或切换到其他可用模型。",
      status: 504,
      category: "timeout",
      detailMessage,
    };
  }

  if (
    normalized.includes("fetch failed") ||
    normalized.includes("econnreset") ||
    normalized.includes("econnrefused") ||
    normalized.includes("enotfound") ||
    normalized.includes("etimedout") ||
    normalized.includes("und_err") ||
    normalized.includes("socket hang up")
  ) {
    return {
      code: "server_error:chat",
      message: "模型服务连接失败，请稍后重试，或切换其他可用模型。",
      status: 502,
      category: "upstream_connection",
      detailMessage,
    };
  }

  if (
    normalized.includes("database") ||
    normalized.includes("postgres") ||
    normalized.includes("drizzle")
  ) {
    return {
      code: "server_error:chat",
      message: "服务数据库暂时繁忙，请稍后重试。",
      status: 503,
      category: "database",
      detailMessage,
    };
  }

  return {
    code: "server_error:chat",
    message: "服务临时繁忙，请稍后重试；如果连续出现，请联系管理员。",
    status: 500,
    category: "unknown",
    detailMessage,
  };
}

export function createChatApiFailureResponse(
  error: unknown,
  vercelId: string | null
) {
  const failure = resolveChatApiFailure(error);
  const traceId = generateUUID();

  chatApiLogger.error("[Chat API] Unhandled request failure:", {
    traceId,
    vercelId,
    category: failure.category,
    status: failure.status,
    detailMessage: failure.detailMessage,
    error,
  });

  return NextResponse.json(
    {
      code: failure.code,
      message: failure.message,
      cause: `trace:${traceId}`,
    },
    { status: failure.status }
  );
}

export async function withOperationTimeout<T>(
  operation: Promise<T>,
  operationName: string,
  timeoutMs: number
): Promise<T> {
  let timer: ReturnType<typeof setTimeout> | null = null;
  try {
    return await Promise.race([
      operation,
      new Promise<never>((_, reject) => {
        timer = setTimeout(
          () => reject(new OperationTimeoutError(operationName, timeoutMs)),
          timeoutMs
        );
      }),
    ]);
  } finally {
    if (timer) {
      clearTimeout(timer);
    }
  }
}

export function getRemainingBudgetMs(startedAt: number, budgetMs: number) {
  return Math.max(0, budgetMs - (Date.now() - startedAt));
}

export function getBudgetedTimeout(params: {
  startedAt: number;
  preferredMs: number;
  minimumMs?: number;
  budgetMs?: number;
}) {
  const minimumMs = params.minimumMs ?? 6_000;
  const remainingMs = getRemainingBudgetMs(
    params.startedAt,
    params.budgetMs ?? DEFAULT_CHAT_PRE_RESPONSE_SOFT_TIMEOUT_MS
  );
  if (remainingMs < minimumMs) {
    return null;
  }
  return Math.min(params.preferredMs, remainingMs);
}