/**
 * @module cwApiLogger
 *
 * Axios interceptor-based logger that records every ConnectWise API
 * request to a JSONL (newline-delimited JSON) file for post-hoc analysis.
 *
 * Each line in the log file is a self-contained JSON object with:
 *   - timestamp (ISO-8601)
 *   - method, url, baseURL
 *   - status (HTTP status or null on network error)
 *   - durationMs (wall-clock time from request start → response/error)
 *   - error (error code / message, if any)
 *   - timeout (configured timeout in ms)
 *
 * Logging is **opt-in** — set the `LOG_CW_API` environment variable to
 * any truthy value to enable it. When enabled, each process start creates
 * a new timestamped file inside the `cw-api-logs/` directory:
 *
 *   LOG_CW_API=1 bun run dev          # uses cw-api-logs/<timestamp>.jsonl
 *   bun run dev:log                    # shorthand (sets LOG_CW_API=1)
 *
 * Appends are non-blocking (fire-and-forget) to avoid slowing down
 * the actual API flow.
 *
 * Usage:
 *   import { attachCwApiLogger } from "./modules/cw-utils/cwApiLogger";
 *   attachCwApiLogger(connectWiseApi);
 */

import { appendFile, mkdir } from "fs/promises";
import path from "path";
import type { AxiosInstance, InternalAxiosRequestConfig } from "axios";

const LOG_DIR = path.resolve(process.cwd(), "cw-api-logs");

/** Build a timestamped filename like `2026-03-02T14-30-05.123Z.jsonl` */
function buildLogPath(): string {
  const ts = new Date().toISOString().replace(/:/g, "-");
  return path.join(LOG_DIR, `${ts}.jsonl`);
}

let LOG_PATH: string | null = null;

// Symbol used to stash the start time on the request config
const START_TIME = Symbol("cwLogStartTime");

interface TimedConfig extends InternalAxiosRequestConfig {
  [START_TIME]?: number;
}

export interface CwApiLogEntry {
  timestamp: string;
  method: string;
  url: string;
  baseURL: string;
  status: number | null;
  durationMs: number;
  error: string | null;
  timeout: number | undefined;
}

/** Write a single log entry (fire-and-forget). */
function writeEntry(entry: CwApiLogEntry): void {
  if (!LOG_PATH) return;
  appendFile(LOG_PATH, JSON.stringify(entry) + "\n").catch((err) => {
    // Swallow write errors — logging should never crash the app
    console.error("[cw-logger] failed to write log entry:", err.message);
  });
}

/**
 * Attach request/response interceptors to an Axios instance to log
 * every CW API call with timing information.
 */
export function attachCwApiLogger(api: AxiosInstance): void {
  if (!process.env.LOG_CW_API) {
    return;
  }

  // Create the log directory and build a unique file path for this run
  LOG_PATH = buildLogPath();
  mkdir(LOG_DIR, { recursive: true }).catch((err) => {
    console.error("[cw-logger] failed to create log directory:", err.message);
  });

  // ---- Request interceptor: record start time --------------------------
  api.interceptors.request.use((config: TimedConfig) => {
    config[START_TIME] = performance.now();
    return config;
  });

  // ---- Response interceptor: log successful calls ----------------------
  api.interceptors.response.use(
    (response) => {
      const config = response.config as TimedConfig;
      const start = config[START_TIME] ?? performance.now();
      const durationMs = Math.round(performance.now() - start);

      writeEntry({
        timestamp: new Date().toISOString(),
        method: (config.method ?? "GET").toUpperCase(),
        url: config.url ?? "",
        baseURL: config.baseURL ?? "",
        status: response.status,
        durationMs,
        error: null,
        timeout: config.timeout,
      });

      return response;
    },

    // ---- Error interceptor: log failed calls -----------------------------
    (err) => {
      const config = (err.config ?? {}) as TimedConfig;
      const start = config[START_TIME] ?? performance.now();
      const durationMs = Math.round(performance.now() - start);

      writeEntry({
        timestamp: new Date().toISOString(),
        method: (config.method ?? "GET").toUpperCase(),
        url: config.url ?? "",
        baseURL: config.baseURL ?? "",
        status: err.response?.status ?? null,
        durationMs,
        error: err.code
          ? `${err.code}: ${err.message}`
          : (err.message ?? "unknown"),
        timeout: config.timeout,
      });

      return Promise.reject(err);
    },
  );

  console.log(`[cw-logger] logging CW API calls to ${LOG_PATH}`);
}

/** Returns the current log file path (or null if logging is disabled). */
export function getCwLogPath(): string | null {
  return LOG_PATH;
}