import { readFileSync, existsSync } from 'fs';
import { logger } from '../utils/logger.js';

/**
 * Extract last message of specified role from transcript JSONL file
 * @param transcriptPath Path to transcript file
 * @param role 'user' or 'assistant'
 * @param stripSystemReminders Whether to remove <system-reminder> tags (for assistant)
 */
export function extractLastMessage(
  transcriptPath: string,
  role: 'user' | 'assistant',
  stripSystemReminders: boolean = false
): string {
  if (!transcriptPath || !existsSync(transcriptPath)) {
    return '';
  }

  try {
    const content = readFileSync(transcriptPath, 'utf-8').trim();
    if (!content) return '';

    const lines = content.split('\n');

    for (let i = lines.length - 1; i >= 0; i--) {
      try {
        const line = JSON.parse(lines[i]);
        if (line.type === role && line.message?.content) {
          let text = '';
          const msgContent = line.message.content;

          if (typeof msgContent === 'string') {
            text = msgContent;
          } else if (Array.isArray(msgContent)) {
            text = msgContent
              .filter((c: any) => c.type === 'text')
              .map((c: any) => c.text)
              .join('\n');
          }

          if (stripSystemReminders) {
            text = text.replace(/<system-reminder>[\s\S]*?<\/system-reminder>/g, '');
            text = text.replace(/\n{3,}/g, '\n\n').trim();
          }

          return text;
        }
      } catch {
        continue;
      }
    }
  } catch (error) {
    logger.error('HOOK', 'Failed to read transcript', { transcriptPath }, error as Error);
  }

  return '';
}