<?php
/**
 * DatabaseService Class
 * 
 * Provides a centralized database abstraction layer for all database operations.
 * Enforces prepared statements, proper error handling, and type safety.
 * 
 * @package 4WDCSA
 * @version 1.0
 */

class DatabaseService {
    private $conn;
    private $lastError = null;
    private $lastQuery = null;
    
    /**
     * Constructor - Initialize database connection
     * 
     * @param mysqli $connection The MySQLi connection object
     */
    public function __construct($connection) {
        if (!$connection) {
            throw new Exception("Database connection failed");
        }
        $this->conn = $connection;
    }
    
    /**
     * Get the last error message
     * 
     * @return string|null The last error or null if no error
     */
    public function getLastError() {
        return $this->lastError;
    }
    
    /**
     * Get the last executed query
     * 
     * @return string|null The last query or null
     */
    public function getLastQuery() {
        return $this->lastQuery;
    }
    
    /**
     * Execute a SELECT query with parameter binding
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string (e.g., "isi" for int, string, int)
     * @return array|false Array of results or false on error
     */
    public function select($query, $params = [], $types = "") {
        try {
            $this->lastQuery = $query;
            $stmt = $this->conn->prepare($query);
            
            if (!$stmt) {
                $this->lastError = "Prepare failed: " . $this->conn->error;
                return false;
            }
            
            if (!empty($params) && !empty($types)) {
                if (!$stmt->bind_param($types, ...$params)) {
                    $this->lastError = "Bind failed: " . $stmt->error;
                    return false;
                }
            }
            
            if (!$stmt->execute()) {
                $this->lastError = "Execute failed: " . $stmt->error;
                return false;
            }
            
            $result = $stmt->get_result();
            $data = [];
            
            while ($row = $result->fetch_assoc()) {
                $data[] = $row;
            }
            
            $stmt->close();
            return $data;
            
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Execute a SELECT query returning a single row
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return array|false Single row as associative array or false
     */
    public function selectOne($query, $params = [], $types = "") {
        $results = $this->select($query, $params, $types);
        return ($results && count($results) > 0) ? $results[0] : false;
    }
    
    /**
     * Execute an INSERT query
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return int|false Last insert ID or false on error
     */
    public function insert($query, $params = [], $types = "") {
        try {
            $this->lastQuery = $query;
            $stmt = $this->conn->prepare($query);
            
            if (!$stmt) {
                $this->lastError = "Prepare failed: " . $this->conn->error;
                return false;
            }
            
            if (!empty($params) && !empty($types)) {
                if (!$stmt->bind_param($types, ...$params)) {
                    $this->lastError = "Bind failed: " . $stmt->error;
                    return false;
                }
            }
            
            if (!$stmt->execute()) {
                $this->lastError = "Execute failed: " . $stmt->error;
                return false;
            }
            
            $insertId = $stmt->insert_id;
            $stmt->close();
            return $insertId;
            
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Execute an UPDATE query
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return int|false Number of affected rows or false on error
     */
    public function update($query, $params = [], $types = "") {
        try {
            $this->lastQuery = $query;
            $stmt = $this->conn->prepare($query);
            
            if (!$stmt) {
                $this->lastError = "Prepare failed: " . $this->conn->error;
                return false;
            }
            
            if (!empty($params) && !empty($types)) {
                if (!$stmt->bind_param($types, ...$params)) {
                    $this->lastError = "Bind failed: " . $stmt->error;
                    return false;
                }
            }
            
            if (!$stmt->execute()) {
                $this->lastError = "Execute failed: " . $stmt->error;
                return false;
            }
            
            $affectedRows = $stmt->affected_rows;
            $stmt->close();
            return $affectedRows;
            
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Execute a DELETE query
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return int|false Number of affected rows or false on error
     */
    public function delete($query, $params = [], $types = "") {
        return $this->update($query, $params, $types);
    }
    
    /**
     * Execute an arbitrary query (for complex queries)
     * 
     * @param string $query SQL query with ? placeholders
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return mixed Query result or false on error
     */
    public function execute($query, $params = [], $types = "") {
        try {
            $this->lastQuery = $query;
            $stmt = $this->conn->prepare($query);
            
            if (!$stmt) {
                $this->lastError = "Prepare failed: " . $this->conn->error;
                return false;
            }
            
            if (!empty($params) && !empty($types)) {
                if (!$stmt->bind_param($types, ...$params)) {
                    $this->lastError = "Bind failed: " . $stmt->error;
                    return false;
                }
            }
            
            if (!$stmt->execute()) {
                $this->lastError = "Execute failed: " . $stmt->error;
                return false;
            }
            
            $stmt->close();
            return true;
            
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Count rows matching a condition
     * 
     * @param string $table Table name
     * @param string $where WHERE clause (without WHERE keyword)
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return int|false Row count or false on error
     */
    public function count($table, $where = "1=1", $params = [], $types = "") {
        $query = "SELECT COUNT(*) as count FROM {$table} WHERE {$where}";
        $result = $this->selectOne($query, $params, $types);
        return ($result) ? (int)$result['count'] : false;
    }
    
    /**
     * Check if a record exists
     * 
     * @param string $table Table name
     * @param string $where WHERE clause (without WHERE keyword)
     * @param array $params Parameters to bind
     * @param string $types Type specification string
     * @return bool True if record exists, false otherwise
     */
    public function exists($table, $where, $params = [], $types = "") {
        $count = $this->count($table, $where, $params, $types);
        return ($count !== false && $count > 0);
    }
    
    /**
     * Get the MySQLi connection object for advanced operations
     * 
     * @return mysqli The MySQLi connection
     */
    public function getConnection() {
        return $this->conn;
    }
    
    /**
     * Start a transaction
     * 
     * @return bool Success status
     */
    public function beginTransaction() {
        try {
            $this->conn->begin_transaction();
            return true;
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Commit a transaction
     * 
     * @return bool Success status
     */
    public function commit() {
        try {
            $this->conn->commit();
            return true;
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
    
    /**
     * Rollback a transaction
     * 
     * @return bool Success status
     */
    public function rollback() {
        try {
            $this->conn->rollback();
            return true;
        } catch (Exception $e) {
            $this->lastError = $e->getMessage();
            return false;
        }
    }
}
?>