/**
 * Server-side conversation memory. Persists each run's user goal + final
 * assistant answer per session, and recalls the recent turns so a run has
 * context even when the plugin sends little/no history. Independent of the
 * plugin's own carry-forward.
 */

import { getDb } from '../db/pool.js';
import { newId } from '../lib/crypto.js';
import type { RunContextMessage } from './types.js';

const MAX_RECALL = 12;       // turns to prepend
const MAX_CONTENT = 4000;    // clip very long turns

export function saveTurn(session_id: string, role: 'user' | 'assistant', content: string, user_id?: string): void {
  if (!session_id || !content) return;
  getDb().prepare(
    'INSERT INTO conversation_turns (id, session_id, user_id, role, content) VALUES (?,?,?,?,?)',
  ).run(newId(), session_id, user_id ?? null, role, content.slice(0, MAX_CONTENT));
}

export function recallTurns(session_id: string, limit = MAX_RECALL): RunContextMessage[] {
  if (!session_id) return [];
  const rows = getDb().prepare(
    'SELECT role, content FROM conversation_turns WHERE session_id = ? ORDER BY created_at DESC LIMIT ?',
  ).all(session_id, limit) as { role: string; content: string }[];
  return rows
    .reverse()
    .map((r) => ({ role: r.role === 'assistant' ? 'assistant' : 'user', content: r.content }) as RunContextMessage);
}

/**
 * Merge recalled memory with the context the plugin sent, de-duplicating
 * so we don't double-feed turns the plugin already included. Memory is
 * prepended (older), then the plugin's context (newer).
 */
export function mergeContext(session_id: string, pluginContext: RunContextMessage[]): RunContextMessage[] {
  const recalled = recallTurns(session_id);
  if (recalled.length === 0) return pluginContext;
  const seen = new Set(pluginContext.map((m) => `${m.role}:${m.content.slice(0, 80)}`));
  const fromMemory = recalled.filter((m) => !seen.has(`${m.role}:${m.content.slice(0, 80)}`));
  return [...fromMemory, ...pluginContext];
}