import type { Logger as IOTelLogger } from "@opentelemetry/api-logs";
import { SeverityNumber } from "@opentelemetry/api-logs";
import type { LoggerProvider } from "@opentelemetry/sdk-logs";
import type { Attributes } from "@opentelemetry/api";
import type { Logger, LogAttributes, LogLevel } from "./types.js";
import { SEVERITY_MAP } from "./types.js";

/**
 * Structured logger wrapping the OpenTelemetry Logs API.
 *
 * Provides an ergonomic interface (info/warn/error/etc.) over the
 * lower-level OTel LogRecord emit API, with child logger support
 * for adding persistent context (request ID, component name, etc.).
 */
export class AppLogger implements Logger {
  private otelLogger: IOTelLogger;
  private provider: LoggerProvider;
  private baseAttributes: LogAttributes;
  private minSeverity: SeverityNumber;

  constructor(
    otelLogger: IOTelLogger,
    provider: LoggerProvider,
    baseAttributes: LogAttributes = {},
    minSeverity: SeverityNumber = SeverityNumber.INFO
  ) {
    this.otelLogger = otelLogger;
    this.provider = provider;
    this.baseAttributes = baseAttributes;
    this.minSeverity = minSeverity;
  }

  debug(message: string, attributes?: LogAttributes): void {
    this.emit(SeverityNumber.DEBUG, "debug", message, attributes);
  }

  info(message: string, attributes?: LogAttributes): void {
    this.emit(SeverityNumber.INFO, "info", message, attributes);
  }

  warn(message: string, attributes?: LogAttributes): void {
    this.emit(SeverityNumber.WARN, "warn", message, attributes);
  }

  error(message: string, attributes?: LogAttributes): void {
    this.emit(SeverityNumber.ERROR, "error", message, attributes);
  }

  fatal(message: string, attributes?: LogAttributes): void {
    this.emit(SeverityNumber.FATAL, "fatal", message, attributes);
  }

  child(attributes: LogAttributes): Logger {
    return new AppLogger(
      this.otelLogger,
      this.provider,
      { ...this.baseAttributes, ...attributes },
      this.minSeverity
    );
  }

  async shutdown(): Promise<void> {
    await this.provider.shutdown();
  }

  private emit(
    severityNumber: SeverityNumber,
    severityText: string,
    message: string,
    attributes?: LogAttributes
  ): void {
    if (severityNumber < this.minSeverity) {
      return;
    }

    this.otelLogger.emit({
      severityNumber,
      severityText,
      body: message,
      attributes: {
        ...this.baseAttributes,
        ...attributes,
      } as Attributes,
    });
  }
}

/** Resolve a LogLevel string to its OTel SeverityNumber. */
export function resolveLogLevel(level: LogLevel): SeverityNumber {
  return SEVERITY_MAP[level];
}