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)) {
throw new Error(`Transcript path missing or file does not exist: ${transcriptPath}`);
}
const content = readFileSync(transcriptPath, 'utf-8').trim();
if (!content) {
throw new Error(`Transcript file exists but is empty: ${transcriptPath}`);
}
const lines = content.split('\n');
let foundMatchingRole = false;
for (let i = lines.length - 1; i >= 0; i--) {
const line = JSON.parse(lines[i]);
if (line.type === role) {
foundMatchingRole = true;
if (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');
} else {
// Unknown content format - throw error
throw new Error(`Unknown message content format in transcript. Type: ${typeof msgContent}`);
}
if (stripSystemReminders) {
text = text.replace(/<system-reminder>[\s\S]*?<\/system-reminder>/g, '');
text = text.replace(/\n{3,}/g, '\n\n').trim();
}
// Return text even if empty - caller decides if that's an error
return text;
}
}
}
// If we searched the whole transcript and didn't find any message of this role
if (!foundMatchingRole) {
throw new Error(`No message found for role '${role}' in transcript: ${transcriptPath}`);
}
return '';
}
