/**
 * Calendar Routes - Scheduled Tasks API
 *
 * RESTful API for multi-project calendar and reminder system
 *
 * Copyright 2025 Tractatus Project
 * Licensed under Apache License 2.0
 */

const express = require('express');
const router = express.Router();
const ScheduledTask = require('../models/ScheduledTask.model');
const { authenticateToken } = require('../middleware/auth.middleware');

// Apply authentication to all calendar routes
router.use(authenticateToken);

/**
 * GET /api/calendar/tasks - Get all scheduled tasks with filters
 */
router.get('/tasks', async (req, res) => {
  try {
    const {
      status,
      category,
      priority,
      projectId,
      includeCompleted,
      limit = 100,
      skip = 0
    } = req.query;

    const query = {};

    // Filter by status
    if (status) {
      query.status = status;
    } else if (includeCompleted !== 'true') {
      query.status = { $in: ['pending', 'in_progress', 'overdue'] };
    }

    // Filter by category
    if (category) {
      query.category = category;
    }

    // Filter by priority
    if (priority) {
      query.priority = priority;
    }

    // Filter by project
    if (projectId) {
      query.projectId = projectId;
    }

    const tasks = await ScheduledTask.find(query)
      .sort({ priority: -1, dueDate: 1 })
      .limit(parseInt(limit))
      .skip(parseInt(skip))
      .populate('projectId', 'name active');

    const total = await ScheduledTask.countDocuments(query);

    res.json({
      success: true,
      tasks,
      pagination: {
        total,
        limit: parseInt(limit),
        skip: parseInt(skip),
        hasMore: total > (parseInt(skip) + parseInt(limit))
      }
    });

  } catch (error) {
    console.error('Error fetching scheduled tasks:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to fetch scheduled tasks'
    });
  }
});

/**
 * GET /api/calendar/tasks/due-soon - Get tasks due within N days (for session-init)
 */
router.get('/tasks/due-soon', async (req, res) => {
  try {
    const { days = 7 } = req.query;

    const tasks = await ScheduledTask.getDueSoon(parseInt(days));

    res.json({
      success: true,
      tasks,
      count: tasks.length
    });

  } catch (error) {
    console.error('Error fetching due-soon tasks:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to fetch due-soon tasks'
    });
  }
});

/**
 * GET /api/calendar/tasks/overdue - Get overdue tasks
 */
router.get('/tasks/overdue', async (req, res) => {
  try {
    const tasks = await ScheduledTask.getOverdue();

    res.json({
      success: true,
      tasks,
      count: tasks.length
    });

  } catch (error) {
    console.error('Error fetching overdue tasks:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to fetch overdue tasks'
    });
  }
});

/**
 * GET /api/calendar/tasks/:id - Get single task
 */
router.get('/tasks/:id', async (req, res) => {
  try {
    const task = await ScheduledTask.findById(req.params.id)
      .populate('projectId', 'name active');

    if (!task) {
      return res.status(404).json({
        success: false,
        error: 'Task not found'
      });
    }

    res.json({
      success: true,
      task
    });

  } catch (error) {
    console.error('Error fetching task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to fetch task'
    });
  }
});

/**
 * POST /api/calendar/tasks - Create new scheduled task
 */
router.post('/tasks', async (req, res) => {
  try {
    const {
      title,
      description,
      dueDate,
      priority,
      category,
      projectId,
      projectName,
      recurrence,
      documentRef,
      links,
      assignedTo,
      metadata,
      tags,
      showInSessionInit,
      reminderDaysBefore
    } = req.body;

    // Validation
    if (!title || !description || !dueDate) {
      return res.status(400).json({
        success: false,
        error: 'Title, description, and dueDate are required'
      });
    }

    const task = new ScheduledTask({
      title,
      description,
      dueDate: new Date(dueDate),
      priority: priority || 'MEDIUM',
      category: category || 'other',
      projectId: projectId || null,
      projectName: projectName || null,
      recurrence: recurrence || 'once',
      documentRef: documentRef || null,
      links: links || [],
      createdBy: 'user',
      assignedTo: assignedTo || 'PM',
      metadata: metadata || {},
      tags: tags || [],
      showInSessionInit: showInSessionInit !== false,
      reminderDaysBefore: reminderDaysBefore || 7
    });

    await task.save();

    res.status(201).json({
      success: true,
      task,
      message: 'Scheduled task created successfully'
    });

  } catch (error) {
    console.error('Error creating scheduled task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to create scheduled task'
    });
  }
});

/**
 * PUT /api/calendar/tasks/:id - Update scheduled task
 */
router.put('/tasks/:id', async (req, res) => {
  try {
    const task = await ScheduledTask.findById(req.params.id);

    if (!task) {
      return res.status(404).json({
        success: false,
        error: 'Task not found'
      });
    }

    // Update allowed fields
    const allowedFields = [
      'title', 'description', 'dueDate', 'priority', 'category',
      'projectId', 'projectName', 'recurrence', 'status', 'documentRef',
      'links', 'assignedTo', 'metadata', 'tags', 'showInSessionInit',
      'reminderDaysBefore'
    ];

    allowedFields.forEach(field => {
      if (req.body[field] !== undefined) {
        task[field] = req.body[field];
      }
    });

    await task.save();

    res.json({
      success: true,
      task,
      message: 'Task updated successfully'
    });

  } catch (error) {
    console.error('Error updating task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to update task'
    });
  }
});

/**
 * POST /api/calendar/tasks/:id/complete - Mark task as completed
 */
router.post('/tasks/:id/complete', async (req, res) => {
  try {
    const task = await ScheduledTask.findById(req.params.id);

    if (!task) {
      return res.status(404).json({
        success: false,
        error: 'Task not found'
      });
    }

    await task.complete();

    res.json({
      success: true,
      task,
      message: 'Task marked as completed'
    });

  } catch (error) {
    console.error('Error completing task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to complete task'
    });
  }
});

/**
 * POST /api/calendar/tasks/:id/dismiss - Dismiss task
 */
router.post('/tasks/:id/dismiss', async (req, res) => {
  try {
    const { reason } = req.body;

    const task = await ScheduledTask.findById(req.params.id);

    if (!task) {
      return res.status(404).json({
        success: false,
        error: 'Task not found'
      });
    }

    await task.dismiss(reason);

    res.json({
      success: true,
      task,
      message: 'Task dismissed'
    });

  } catch (error) {
    console.error('Error dismissing task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to dismiss task'
    });
  }
});

/**
 * DELETE /api/calendar/tasks/:id - Delete scheduled task
 */
router.delete('/tasks/:id', async (req, res) => {
  try {
    const task = await ScheduledTask.findByIdAndDelete(req.params.id);

    if (!task) {
      return res.status(404).json({
        success: false,
        error: 'Task not found'
      });
    }

    res.json({
      success: true,
      message: 'Task deleted successfully'
    });

  } catch (error) {
    console.error('Error deleting task:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to delete task'
    });
  }
});

/**
 * GET /api/calendar/stats - Get calendar statistics
 */
router.get('/stats', async (req, res) => {
  try {
    const stats = {
      total: await ScheduledTask.countDocuments(),
      pending: await ScheduledTask.countDocuments({ status: 'pending' }),
      overdue: await ScheduledTask.countDocuments({ status: 'overdue' }),
      completed: await ScheduledTask.countDocuments({ status: 'completed' }),
      byCategory: {},
      byPriority: {},
      dueSoon: await ScheduledTask.countDocuments({
        dueDate: { $lte: new Date(Date.now() + 7 * 24 * 60 * 60 * 1000) },
        status: 'pending'
      })
    };

    // Category breakdown
    const categories = ['framework', 'governance', 'security', 'project', 'research', 'deployment', 'other'];
    for (const cat of categories) {
      stats.byCategory[cat] = await ScheduledTask.countDocuments({
        category: cat,
        status: { $in: ['pending', 'in_progress', 'overdue'] }
      });
    }

    // Priority breakdown
    const priorities = ['LOW', 'MEDIUM', 'HIGH', 'CRITICAL'];
    for (const pri of priorities) {
      stats.byPriority[pri] = await ScheduledTask.countDocuments({
        priority: pri,
        status: { $in: ['pending', 'in_progress', 'overdue'] }
      });
    }

    res.json({
      success: true,
      stats
    });

  } catch (error) {
    console.error('Error fetching calendar stats:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to fetch calendar statistics'
    });
  }
});

module.exports = router;