import { query } from '../config/database';
import { CreateProjectInput, UpdateProjectInput, ProjectStatusType } from '../validators/project.validator';

/**
 * Project interface matching database schema
 */
export interface Project {
  id: string;
  name: string;
  description: string | null;
  area_name: string | null;
  location: string | null;
  status: ProjectStatusType;
  created_by: string | null;
  created_at: Date;
  updated_at: Date;
}

/**
 * Project statistics interface
 */
export interface ProjectStats {
  meter_count: number;
  device_count: number;
  concentrator_count: number;
  active_meters: number;
  inactive_meters: number;
}

/**
 * Pagination parameters interface
 */
export interface PaginationParams {
  page: number;
  pageSize: number;
}

/**
 * Filter parameters for projects
 */
export interface ProjectFilters {
  status?: ProjectStatusType;
  area_name?: string;
  search?: string;
}

/**
 * Paginated result interface
 */
export interface PaginatedResult<T> {
  data: T[];
  pagination: {
    page: number;
    pageSize: number;
    total: number;
    totalPages: number;
  };
}

/**
 * Get all projects with optional filtering and pagination
 * @param filters - Optional filters for status and area_name
 * @param pagination - Optional pagination parameters
 * @returns Paginated list of projects
 */
export async function getAll(
  filters?: ProjectFilters,
  pagination?: PaginationParams
): Promise<PaginatedResult<Project>> {
  const page = pagination?.page || 1;
  const pageSize = pagination?.pageSize || 10;
  const offset = (page - 1) * pageSize;

  // Build WHERE clause dynamically
  const conditions: string[] = [];
  const params: unknown[] = [];
  let paramIndex = 1;

  if (filters?.status) {
    conditions.push(`status = $${paramIndex}`);
    params.push(filters.status);
    paramIndex++;
  }

  if (filters?.area_name) {
    conditions.push(`area_name ILIKE $${paramIndex}`);
    params.push(`%${filters.area_name}%`);
    paramIndex++;
  }

  if (filters?.search) {
    conditions.push(`(name ILIKE $${paramIndex} OR description ILIKE $${paramIndex})`);
    params.push(`%${filters.search}%`);
    paramIndex++;
  }

  const whereClause = conditions.length > 0 ? `WHERE ${conditions.join(' AND ')}` : '';

  // Get total count
  const countQuery = `SELECT COUNT(*) as total FROM projects ${whereClause}`;
  const countResult = await query<{ total: string }>(countQuery, params);
  const total = parseInt(countResult.rows[0]?.total || '0', 10);

  // Get paginated data
  const dataQuery = `
    SELECT id, name, description, area_name, location, status, created_by, created_at, updated_at
    FROM projects
    ${whereClause}
    ORDER BY created_at DESC
    LIMIT $${paramIndex} OFFSET $${paramIndex + 1}
  `;
  params.push(pageSize, offset);

  const result = await query<Project>(dataQuery, params);

  return {
    data: result.rows,
    pagination: {
      page,
      pageSize,
      total,
      totalPages: Math.ceil(total / pageSize),
    },
  };
}

/**
 * Get a single project by ID
 * @param id - Project UUID
 * @returns Project or null if not found
 */
export async function getById(id: string): Promise<Project | null> {
  const result = await query<Project>(
    `SELECT id, name, description, area_name, location, status, created_by, created_at, updated_at
     FROM projects
     WHERE id = $1`,
    [id]
  );

  return result.rows[0] || null;
}

/**
 * Create a new project
 * @param data - Project data
 * @param userId - ID of the user creating the project
 * @returns Created project
 */
export async function create(data: CreateProjectInput, userId: string): Promise<Project> {
  const result = await query<Project>(
    `INSERT INTO projects (name, description, area_name, location, status, created_by)
     VALUES ($1, $2, $3, $4, $5, $6)
     RETURNING id, name, description, area_name, location, status, created_by, created_at, updated_at`,
    [
      data.name,
      data.description || null,
      data.area_name || null,
      data.location || null,
      data.status || 'ACTIVE',
      userId,
    ]
  );

  return result.rows[0];
}

/**
 * Update an existing project
 * @param id - Project UUID
 * @param data - Updated project data
 * @returns Updated project or null if not found
 */
export async function update(id: string, data: UpdateProjectInput): Promise<Project | null> {
  // Build SET clause dynamically based on provided fields
  const updates: string[] = [];
  const params: unknown[] = [];
  let paramIndex = 1;

  if (data.name !== undefined) {
    updates.push(`name = $${paramIndex}`);
    params.push(data.name);
    paramIndex++;
  }

  if (data.description !== undefined) {
    updates.push(`description = $${paramIndex}`);
    params.push(data.description);
    paramIndex++;
  }

  if (data.area_name !== undefined) {
    updates.push(`area_name = $${paramIndex}`);
    params.push(data.area_name);
    paramIndex++;
  }

  if (data.location !== undefined) {
    updates.push(`location = $${paramIndex}`);
    params.push(data.location);
    paramIndex++;
  }

  if (data.status !== undefined) {
    updates.push(`status = $${paramIndex}`);
    params.push(data.status);
    paramIndex++;
  }

  // Always update the updated_at timestamp
  updates.push(`updated_at = NOW()`);

  if (updates.length === 1) {
    // Only updated_at was added, no actual data to update
    return getById(id);
  }

  params.push(id);

  const result = await query<Project>(
    `UPDATE projects
     SET ${updates.join(', ')}
     WHERE id = $${paramIndex}
     RETURNING id, name, description, area_name, location, status, created_by, created_at, updated_at`,
    params
  );

  return result.rows[0] || null;
}

/**
 * Delete a project by ID
 * Checks for dependent meters/concentrators before deletion
 * @param id - Project UUID
 * @returns True if deleted, throws error if has dependencies
 */
export async function deleteProject(id: string): Promise<boolean> {
  // Check for dependent meters
  const meterCheck = await query<{ count: string }>(
    'SELECT COUNT(*) as count FROM meters WHERE project_id = $1',
    [id]
  );
  const meterCount = parseInt(meterCheck.rows[0]?.count || '0', 10);

  if (meterCount > 0) {
    throw new Error(`Cannot delete project: ${meterCount} meter(s) are associated with this project`);
  }

  // Check for dependent concentrators
  const concentratorCheck = await query<{ count: string }>(
    'SELECT COUNT(*) as count FROM concentrators WHERE project_id = $1',
    [id]
  );
  const concentratorCount = parseInt(concentratorCheck.rows[0]?.count || '0', 10);

  if (concentratorCount > 0) {
    throw new Error(`Cannot delete project: ${concentratorCount} concentrator(s) are associated with this project`);
  }

  const result = await query('DELETE FROM projects WHERE id = $1', [id]);

  return (result.rowCount || 0) > 0;
}

/**
 * Get project statistics
 * @param id - Project UUID
 * @returns Project statistics including meter count, device count, etc.
 */
export async function getStats(id: string): Promise<ProjectStats | null> {
  // Verify project exists
  const project = await getById(id);
  if (!project) {
    return null;
  }

  // Get meter counts
  const meterStats = await query<{ total: string; active: string; inactive: string }>(
    `SELECT
       COUNT(*) as total,
       COUNT(*) FILTER (WHERE status = 'ACTIVE' OR status = 'active') as active,
       COUNT(*) FILTER (WHERE status = 'INACTIVE' OR status = 'inactive') as inactive
     FROM meters
     WHERE project_id = $1`,
    [id]
  );

  // Get device count (devices linked to meters in this project)
  const deviceStats = await query<{ count: string }>(
    `SELECT COUNT(DISTINCT device_id) as count
     FROM meters
     WHERE project_id = $1 AND device_id IS NOT NULL`,
    [id]
  );

  // Get concentrator count
  const concentratorStats = await query<{ count: string }>(
    'SELECT COUNT(*) as count FROM concentrators WHERE project_id = $1',
    [id]
  );

  return {
    meter_count: parseInt(meterStats.rows[0]?.total || '0', 10),
    active_meters: parseInt(meterStats.rows[0]?.active || '0', 10),
    inactive_meters: parseInt(meterStats.rows[0]?.inactive || '0', 10),
    device_count: parseInt(deviceStats.rows[0]?.count || '0', 10),
    concentrator_count: parseInt(concentratorStats.rows[0]?.count || '0', 10),
  };
}