import {
  LoggerProvider,
  SimpleLogRecordProcessor,
} from "@opentelemetry/sdk-logs";
import { resourceFromAttributes } from "@opentelemetry/resources";
import {
  ATTR_SERVICE_NAME,
  ATTR_SERVICE_VERSION,
} from "@opentelemetry/semantic-conventions";
import { StructuredLogExporter } from "./exporter.js";
import { AppLogger, resolveLogLevel } from "./logger.js";
import type { CreateLoggerOptions, Logger } from "./types.js";

/**
 * Create a structured logger backed by the OpenTelemetry Logs SDK.
 *
 * Sets up a LoggerProvider with a Resource describing the service,
 * and a StructuredLogExporter that writes NDJSON to stdout.
 *
 * When traces and metrics are added later, the same Resource
 * can be shared across all signal providers.
 *
 * @example
 * ```ts
 * const logger = createLogger({
 *   service: "atbb-appview",
 *   version: "0.1.0",
 *   environment: "development",
 *   level: "debug",
 * });
 *
 * logger.info("Server started", { port: 3000 });
 * logger.error("Query failed", { error: err.message, table: "posts" });
 *
 * const reqLog = logger.child({ requestId: "abc-123" });
 * reqLog.info("Handling request");
 * ```
 */
export function createLogger(options: CreateLoggerOptions): Logger {
  const resourceAttrs: Record<string, string> = {
    [ATTR_SERVICE_NAME]: options.service,
  };
  if (options.version) {
    resourceAttrs[ATTR_SERVICE_VERSION] = options.version;
  }
  if (options.environment) {
    resourceAttrs["deployment.environment.name"] = options.environment;
  }

  const resource = resourceFromAttributes(resourceAttrs);
  const exporter = new StructuredLogExporter();
  const processor = new SimpleLogRecordProcessor(exporter);

  const provider = new LoggerProvider({ resource });
  provider.addLogRecordProcessor(processor);

  const otelLogger = provider.getLogger(options.service);
  const minSeverity = resolveLogLevel(options.level ?? "info");

  return new AppLogger(otelLogger, provider, {}, minSeverity);
}