export type LogLevel = 'debug' | 'info' | 'warn' | 'error';

const LOG_LEVEL_ORDER: Record<LogLevel, number> = {
  debug: 0,
  info: 1,
  warn: 2,
  error: 3
};

const LOG_LEVELS = new Set<LogLevel>(['debug', 'info', 'warn', 'error']);

function normalizeLogLevel(value: unknown, fallback: LogLevel): LogLevel {
  const normalized = typeof value === 'string' ? value.trim().toLowerCase() : '';
  if (LOG_LEVELS.has(normalized as LogLevel)) {
    return normalized as LogLevel;
  }

  return fallback;
}

export class Logger {
  private level: LogLevel;

  constructor(private scope: string, level: LogLevel = 'info') {
    this.level = normalizeLogLevel(process.env.LOG_LEVEL ?? process.env.LOGLEVEL, level);
  }

  private shouldLog(level: LogLevel) {
    return LOG_LEVEL_ORDER[level] >= LOG_LEVEL_ORDER[this.level];
  }

  isEnabled(level: LogLevel): boolean {
    return this.shouldLog(level);
  }

  debug(...args: unknown[]) {
    if (!this.shouldLog('debug')) return;
    // Write to stderr to avoid corrupting MCP stdout stream
    console.error(`[${this.scope}]`, ...args);
  }
  info(...args: unknown[]) {
    if (!this.shouldLog('info')) return;
    // Write to stderr to avoid corrupting MCP stdout stream
    console.error(`[${this.scope}]`, ...args);
  }
  warn(...args: unknown[]) {
    if (!this.shouldLog('warn')) return;
    console.error(`[${this.scope}]`, ...args);
  }
  error(...args: unknown[]) {
    if (this.shouldLog('error')) console.error(`[${this.scope}]`, ...args);
  }
}