'use strict';

const fs = require('fs');
const path = require('path');
const { randomUUID } = require('crypto');
const auth = require('./auth');
const identity = require('./identity');

const CHECKPOINTS_DIR = path.join(auth.getAgentIndexDir('dummy'), '..', '..', 'checkpoints');

function getAgentCheckpointsDir(agentId) {
  const dir = path.join(CHECKPOINTS_DIR, agentId);
  fs.mkdirSync(dir, { recursive: true });
  return dir;
}

// Create a checkpoint at session end
function createCheckpoint(agentId, sessionData) {
  const agentDir = getAgentCheckpointsDir(agentId);
  const sessionId = randomUUID();
  const now = new Date().toISOString();

  const checkpoint = {
    metadata: {
      agent_id: agentId,
      session_id: sessionId,
      started_at: sessionData.started_at || now,
      ended_at: now,
      duration_seconds: sessionData.duration_seconds || 0,
      checkpoint_version: '1.0'
    },
    context: {
      current_focus: sessionData.current_focus || null,
      active_project_ids: sessionData.active_project_ids || [],
      conversation_summary: sessionData.conversation_summary || '',
      pending_items: sessionData.pending_items || []
    },
    recent_memories: {
      memory_ids: sessionData.memory_ids || [],
      last_recall_query: sessionData.last_recall_query || null
    },
    identity_updates: {
      new_beliefs: sessionData.new_beliefs || [],
      new_skills: sessionData.new_skills || [],
      new_relationships: sessionData.new_relationships || [],
      drift_checks: sessionData.drift_checks || { passed: 0, failed: 0 }
    },
    working_memory: {
      scratchpad: sessionData.scratchpad || '',
      open_files: sessionData.open_files || [],
      context_stack: sessionData.context_stack || []
    }
  };

  const filename = `checkpoint-${checkpoint.metadata.ended_at.replace(/:/g, '-')}.json`;
  const filepath = path.join(agentDir, filename);

  fs.writeFileSync(filepath, JSON.stringify(checkpoint, null, 2), 'utf8');

  return checkpoint;
}

// Get the most recent checkpoint for an agent
function getLatestCheckpoint(agentId) {
  const agentDir = getAgentCheckpointsDir(agentId);

  try {
    const files = fs.readdirSync(agentDir)
      .filter(f => f.startsWith('checkpoint-') && f.endsWith('.json'))
      .sort()
      .reverse();

    if (files.length === 0) {
      return null;
    }

    const latestFile = path.join(agentDir, files[0]);
    const content = fs.readFileSync(latestFile, 'utf8');
    return JSON.parse(content);
  } catch (err) {
    return null;
  }
}

// List all checkpoints for an agent
function listCheckpoints(agentId) {
  const agentDir = getAgentCheckpointsDir(agentId);

  try {
    const files = fs.readdirSync(agentDir)
      .filter(f => f.startsWith('checkpoint-') && f.endsWith('.json'))
      .sort()
      .reverse();

    return files.map(f => {
      const content = fs.readFileSync(path.join(agentDir, f), 'utf8');
      const cp = JSON.parse(content);
      return {
        session_id: cp.metadata.session_id,
        ended_at: cp.metadata.ended_at,
        duration_seconds: cp.metadata.duration_seconds,
        summary: cp.context.conversation_summary?.substring(0, 100) || 'No summary'
      };
    });
  } catch (err) {
    return [];
  }
}

// Restore session (mark as session start)
function restoreSession(agentId) {
  const id = identity.loadIdentity(agentId);
  if (!id) {
    throw new Error(`Identity not found for agent: ${agentId}`);
  }

  const checkpoint = getLatestCheckpoint(agentId);

  // Update identity state
  const now = new Date().toISOString();
  identity.updateMutableState(agentId, {
    state: {
      last_session_at: now,
      accumulated_experience: (id.mutable.state?.accumulated_experience || 0) + 1
    }
  });

  return {
    restored: !!checkpoint,
    checkpoint,
    identity_updated: true
  };
}

// Get session statistics for an agent
function getSessionStats(agentId) {
  const checkpoints = listCheckpoints(agentId);
  const id = identity.loadIdentity(agentId);

  const totalSessions = checkpoints.length;
  const totalDuration = checkpoints.reduce((sum, cp) => sum + (cp.duration_seconds || 0), 0);
  const avgDuration = totalSessions > 0 ? totalDuration / totalSessions : 0;

  return {
    agent_id: agentId,
    total_sessions: totalSessions,
    total_duration_seconds: totalDuration,
    avg_session_duration_seconds: Math.round(avgDuration),
    accumulated_experience: id?.mutable.state?.accumulated_experience || 0,
    last_session_at: id?.mutable.state?.last_session_at || null,
    drift_checks: {
      passed: id?.mutable.state?.drift_checks_passed || 0,
      failed: id?.mutable.state?.drift_checks_failed || 0
    }
  };
}

module.exports = {
  createCheckpoint,
  getLatestCheckpoint,
  listCheckpoints,
  restoreSession,
  getSessionStats
};