import type { MiddlewareHandler } from "hono";
import { createMiddleware } from "hono/factory";
import type { Logger } from "./types.js";

/**
 * Hono middleware that logs structured HTTP request/response data.
 *
 * Replaces Hono's built-in `logger()` middleware with OpenTelemetry-backed
 * structured logging. Each request gets a child logger with request context
 * that is available to downstream handlers via `c.get("logger")`.
 *
 * Log output:
 * - Incoming request: method, path (at debug level)
 * - Completed response: method, path, status, duration_ms
 *   (info for 2xx, warn for 4xx, error for 5xx — including errors handled by onError)
 *
 * @example
 * ```ts
 * import { createLogger } from "@atbb/logger";
 * import { requestLogger } from "@atbb/logger/middleware";
 *
 * const logger = createLogger({ service: "atbb-appview" });
 * app.use("*", requestLogger(logger));
 *
 * // In route handlers:
 * app.get("/api/forum", (c) => {
 *   const log = c.get("logger");
 *   log.info("Fetching forum metadata");
 *   // ...
 * });
 * ```
 */
export function requestLogger(logger: Logger): MiddlewareHandler {
  return createMiddleware(async (c, next) => {
    const start = performance.now();
    const method = c.req.method;
    const path = c.req.path;

    // Create a child logger scoped to this request
    const reqLogger = logger.child({
      method,
      path,
    });

    // Make the logger available to downstream handlers
    c.set("logger", reqLogger);

    reqLogger.debug("Request received");

    await next();

    const duration = Math.round(performance.now() - start);
    const status = c.res.status;
    const level = status >= 500 ? "error" : status >= 400 ? "warn" : "info";

    reqLogger[level]("Request completed", {
      status,
      duration_ms: duration,
    });
  });
}