import { loadEnv } from "../config/env.js";
import type { Request } from "express";
import { otelContext, otelTrace } from "@factory/observability";

export interface Logger {
  child(bindings: Record<string, unknown>): Logger;
  debug(msg: string, extra?: Record<string, unknown>): void;
  info(msg: string, extra?: Record<string, unknown>): void;
  warn(msg: string, extra?: Record<string, unknown>): void;
  error(msg: string, extra?: Record<string, unknown>): void;
}

class ConsoleLogger implements Logger {
  constructor(private readonly base: Record<string, unknown> = {}) {}

  child(bindings: Record<string, unknown>): Logger {
    return new ConsoleLogger({ ...this.base, ...bindings });
  }

  private log(level: string, msg: string, extra?: Record<string, unknown>): void {
    const env = safeEnv();
    if (level === "debug" && env.NODE_ENV === "production") return;
    // TASK-0135: correlate every line with the ACTIVE OTel span (traceId/
    // spanId — the requestId binding already comes from the logger's base /
    // child bindings, or is supplied by the caller via `extra`). Absent when
    // no span is active (or OTel disabled) — keys are omitted, never null.
    const line: Record<string, unknown> = {
      level,
      time: new Date().toISOString(),
      msg,
      ...this.base,
      ...(extra ?? {})
    };
    const sc = otelTrace.getSpanContext(otelContext.active());
    if (sc && sc.traceId && sc.spanId) {
      line.traceId = sc.traceId;
      line.spanId = sc.spanId;
    }
    const out = JSON.stringify(line);
    if (level === "error") process.stderr.write(out + "\n");
    else if (level === "warn") process.stderr.write(out + "\n");
    else process.stdout.write(out + "\n");
  }

  debug(msg: string, extra?: Record<string, unknown>): void {
    this.log("debug", msg, extra);
  }
  info(msg: string, extra?: Record<string, unknown>): void {
    this.log("info", msg, extra);
  }
  warn(msg: string, extra?: Record<string, unknown>): void {
    this.log("warn", msg, extra);
  }
  error(msg: string, extra?: Record<string, unknown>): void {
    this.log("error", msg, extra);
  }
}

function safeEnv() {
  try {
    return loadEnv();
  } catch {
    return { NODE_ENV: "development" };
  }
}

export const logger: Logger = new ConsoleLogger({ service: "factory-api" });

export function requestId(req: Request): string {
  return req.id ?? "unknown";
}