import { redactLogArgs, redactValue } from "@/lib/observability/redaction";

type LogLevel = "debug" | "info" | "warn" | "error" | "silent";

const LEVEL_ORDER: Record<LogLevel, number> = {
  debug: 10,
  info: 20,
  warn: 30,
  error: 40,
  silent: 50,
};
const SENSITIVE_EVENT_PATTERN =
  /(authorization|body|cookie|header|image url|messages received|password|prompt|request body|session|token)/i;

function resolveLogLevel(): LogLevel {
  const configured = String(process.env.LOG_LEVEL || "").toLowerCase();
  if (configured in LEVEL_ORDER) return configured as LogLevel;
  return process.env.NODE_ENV === "production" ? "info" : "debug";
}

function shouldLog(level: Exclude<LogLevel, "silent">) {
  return LEVEL_ORDER[level] >= LEVEL_ORDER[resolveLogLevel()];
}

function normalizeEvent(event: string) {
  return event
    .trim()
    .replace(/^\[[^\]]+\]\s*/, "")
    .replace(/[^a-zA-Z0-9]+/g, "_")
    .replace(/^_+|_+$/g, "")
    .toLowerCase()
    .slice(0, 80) || "event";
}

function writeLog(level: Exclude<LogLevel, "silent">, scope: string, event: string, args: unknown[]) {
  if (!shouldLog(level)) return;

  const payload = {
    level,
    scope,
    event: normalizeEvent(event),
    message: event,
    timestamp: new Date().toISOString(),
    ...(args.length > 0
      ? {
          meta: SENSITIVE_EVENT_PATTERN.test(event)
            ? { omitted: true, argCount: args.length }
            : redactLogArgs(args),
        }
      : {}),
  };

  const serialized = JSON.stringify(redactValue(payload));
  if (level === "error") {
    console.error(serialized);
    return;
  }
  if (level === "warn") {
    console.warn(serialized);
    return;
  }
  console.log(serialized);
}

export function createLogger(scope: string) {
  return {
    debug(event: string, ...args: unknown[]) {
      writeLog("debug", scope, event, args);
    },
    info(event: string, ...args: unknown[]) {
      writeLog("info", scope, event, args);
    },
    warn(event: string, ...args: unknown[]) {
      writeLog("warn", scope, event, args);
    },
    error(event: string, ...args: unknown[]) {
      writeLog("error", scope, event, args);
    },
  };
}