memory.js

import { readFile, writeFile, appendFile, readdir, mkdir } from 'fs/promises';
import { join, basename } from 'path';
import config from './config.js';

const DIR = config.dataDir;

async function ensureDir() {
  await mkdir(DIR, { recursive: true });
}

function safe(name) {
  return basename(name).replace(/[^a-zA-Z0-9._-]/g, '_');
}

export async function readMemory(file) {
  try {
    return await readFile(join(DIR, safe(file)), 'utf-8');
  } catch {
    return null;
  }
}

export async function writeMemory(file, content) {
  await ensureDir();
  await writeFile(join(DIR, safe(file)), content, 'utf-8');
}

// Keep journal files under this character limit (~1.25M tokens).
// When exceeded, trim the oldest ~40% of content.
const MAX_JOURNAL_CHARS = 5_000_000;

export async function appendMemory(file, content) {
  await ensureDir();
  const filePath = join(DIR, safe(file));
  const existing = await readMemory(file);
  const sep = existing ? '\n\n' : '';
  await appendFile(filePath, sep + content, 'utf-8');

  if (file.endsWith('.md')) {
    try {
      const full = await readFile(filePath, 'utf-8');
      if (full.length > MAX_JOURNAL_CHARS) {
        const lines = full.split('\n');
        const cutAt = Math.floor(lines.length * 0.4);
        const trimmed = [
          `[journal trimmed — oldest ${cutAt} lines archived at ${new Date().toISOString()}]`,
          '',
          ...lines.slice(cutAt),
        ].join('\n');
        await writeFile(filePath, trimmed, 'utf-8');
      }
    } catch {}
  }
}

export async function listMemories() {
  try {
    return (await readdir(DIR)).filter(
      (f) => f.endsWith('.md') || f.endsWith('.json'),
    );
  } catch {
    return [];
  }
}