import { pool } from '../config/database';
import { CreateConcentratorInput, UpdateConcentratorInput } from '../validators/concentrator.validator';

/**
 * Concentrator types
 */
export type ConcentratorType = 'LORA' | 'LORAWAN' | 'GRANDES';

/**
 * Concentrator entity interface
 */
export interface Concentrator {
  id: string;
  serial_number: string;
  name: string | null;
  project_id: string;
  location: string | null;
  type: ConcentratorType;
  status: 'online' | 'offline' | 'maintenance' | 'unknown';
  ip_address: string | null;
  firmware_version: string | null;
  created_at: Date;
  updated_at: Date;
}

/**
 * Concentrator with gateway count
 */
export interface ConcentratorWithCount extends Concentrator {
  gateway_count: number;
}

/**
 * Filter options for concentrators
 */
export interface ConcentratorFilters {
  project_id?: string;
  status?: string;
  type?: ConcentratorType;
}

/**
 * Pagination options
 */
export interface PaginationOptions {
  page?: number;
  limit?: number;
  sortBy?: string;
  sortOrder?: 'asc' | 'desc';
}

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

/**
 * Get all concentrators with optional filters and pagination
 * @param filters - Optional filter criteria
 * @param pagination - Optional pagination options
 * @returns Paginated list of concentrators
 */
export async function getAll(
  filters?: ConcentratorFilters,
  pagination?: PaginationOptions
): Promise<PaginatedResult<Concentrator>> {
  const page = pagination?.page || 1;
  const limit = pagination?.limit || 10;
  const offset = (page - 1) * limit;
  const sortBy = pagination?.sortBy || 'created_at';
  const sortOrder = pagination?.sortOrder || 'desc';

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

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

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

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

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

  // Validate sort column to prevent SQL injection
  const allowedSortColumns = ['id', 'serial_number', 'name', 'status', 'created_at', 'updated_at'];
  const safeSortBy = allowedSortColumns.includes(sortBy) ? sortBy : 'created_at';
  const safeSortOrder = sortOrder === 'asc' ? 'ASC' : 'DESC';

  // Get total count
  const countQuery = `SELECT COUNT(*) FROM concentrators ${whereClause}`;
  const countResult = await pool.query(countQuery, params);
  const total = parseInt(countResult.rows[0].count, 10);

  // Get data
  const dataQuery = `
    SELECT * FROM concentrators
    ${whereClause}
    ORDER BY ${safeSortBy} ${safeSortOrder}
    LIMIT $${paramIndex} OFFSET $${paramIndex + 1}
  `;
  params.push(limit, offset);

  const dataResult = await pool.query<Concentrator>(dataQuery, params);

  const totalPages = Math.ceil(total / limit);

  return {
    data: dataResult.rows,
    pagination: {
      page,
      limit,
      total,
      totalPages,
      hasNextPage: page < totalPages,
      hasPreviousPage: page > 1,
    },
  };
}

/**
 * Get a single concentrator by ID with gateway count
 * @param id - Concentrator UUID
 * @returns Concentrator with gateway count or null
 */
export async function getById(id: string): Promise<ConcentratorWithCount | null> {
  const query = `
    SELECT
      c.*,
      COALESCE(COUNT(g.id), 0)::int as gateway_count
    FROM concentrators c
    LEFT JOIN gateways g ON g.concentrator_id = c.id
    WHERE c.id = $1
    GROUP BY c.id
  `;

  const result = await pool.query<ConcentratorWithCount>(query, [id]);
  return result.rows[0] || null;
}

/**
 * Create a new concentrator
 * @param data - Concentrator creation data
 * @returns Created concentrator
 */
export async function create(data: CreateConcentratorInput): Promise<Concentrator> {
  const query = `
    INSERT INTO concentrators (serial_number, name, project_id, location, type, status, ip_address, firmware_version)
    VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
    RETURNING *
  `;

  const params = [
    data.serial_number,
    data.name || null,
    data.project_id,
    data.location || null,
    data.type || 'LORA',
    data.status || 'ACTIVE',
    data.ip_address || null,
    data.firmware_version || null,
  ];

  const result = await pool.query<Concentrator>(query, params);
  return result.rows[0];
}

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

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

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

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

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

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

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

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

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

  if (updates.length === 0) {
    // No updates provided, return existing record
    const existing = await getById(id);
    return existing;
  }

  updates.push(`updated_at = NOW()`);

  const query = `
    UPDATE concentrators
    SET ${updates.join(', ')}
    WHERE id = $${paramIndex}
    RETURNING *
  `;
  params.push(id);

  const result = await pool.query<Concentrator>(query, params);
  return result.rows[0] || null;
}

/**
 * Delete a concentrator
 * Checks for dependent gateways before deletion
 * @param id - Concentrator UUID
 * @returns True if deleted, throws error if has dependencies
 */
export async function remove(id: string): Promise<boolean> {
  // Check for dependent gateways
  const gatewayCheck = await pool.query(
    'SELECT COUNT(*) FROM gateways WHERE concentrator_id = $1',
    [id]
  );

  const gatewayCount = parseInt(gatewayCheck.rows[0].count, 10);

  if (gatewayCount > 0) {
    throw new Error(`Cannot delete concentrator: ${gatewayCount} gateway(s) are associated with it`);
  }

  const result = await pool.query(
    'DELETE FROM concentrators WHERE id = $1 RETURNING id',
    [id]
  );

  return result.rowCount !== null && result.rowCount > 0;
}