<?php

class DataBase {
    public $pdo;
    protected $prepared_statements = [];

    public function __construct($dsn, $usr=null, $pwd=null, $args=null) {
        try {
            $pdo = new PDO($dsn, $usr, $pwd, $args);
        }
        catch (PDOException $e) {
            throw new RuntimeException('Connection failed: ' . $e->getMessage());
        }
        $this->pdo = $pdo;
    }

    public function quote_name($name) {
        return '`' . str_replace('`', '``', $name) .  '`';
    }

    public function execute($query, array $bindings=[]) {
        $t = $this;
        $h = md5($query);
        if (isset($t->prepared_statements[$h])) {
            $stm = $t->prepared_statements[$h];
        }
        else {
            $stm = $t->pdo->prepare($query);
            $t->prepared_statements[$h] = $stm;
        }
        $stm->execute($bindings);
        preg_match('/^\s*(\w+)/', $query, $m);
        $action = strtolower($m[1]);
        if ($action == 'update' or $action == 'delete') {
            return $stm->rowCount();
        }
        if ($action == 'insert') {
            return $t->last_insert_id();
        }
        return $stm;
    }

    public function row($query, array $bindings=[]) {
        $stm = $this->execute($query, $bindings);
        return $stm->fetch(PDO::FETCH_ASSOC);
    }

    public function rows($query, array $bindings=[]) {
        $stm = $this->execute($query, $bindings);
        return $stm->fetchAll(PDO::FETCH_ASSOC);
    }

    public function column($query, array $bindings=[]) {
        $stm = $this->execute($query, $bindings);
        return $stm->fetchColumn();
    }

    public function find($table, $id, $field='id') {
        $t = $this;
        $table = $t->quote_name($table);
        $field = $t->quote_name($field);
        return $t->row("SELECT * FROM $table WHERE $field=? LIMIT 1", [$id]);
    }

    public function count($table, $where=1, array $bindings=[]) {
        $t = $this;
        $table = $t->quote_name($table);
        list($where, $bindings) = $t->get_where($where, $bindings);
        $q = "SELECT COUNT(*) FROM $table WHERE $where";
        return (int) $t->column($q, $bindings);
    }

    public function contains($table, $field, $value) {
        return $this->count($table, [$field => $value]) > 0;
    }

    public function add($table, array $data) {
        $t = $this;
        $table = $t->quote_name($table);
        $q = "INSERT INTO $table ";
        if (is_list($data)) {
            $q .= 'VALUES (' . implode(',', array_fill(0, count($data), '?')) . ')';
        }
        else {
            $columns = [];
            $values = [];
            $keys = array_keys($data);
            foreach ($keys as $v) {
                $columns[] = $t->quote_name($v);
                $values[] = ":$v";
            }
            $columns = implode(',', $columns);
            $values = implode(',', $values);
            $q .= "($columns) VALUES ($values)";
        }
        return $t->execute($q, $data);
    }

    public function update($table, array $data, $where=1, array $bindings=[]) {
        $t = $this;
        $set = [];
        list($where, $bindings) = $t->get_where($where, $bindings);
        $is_list = is_list($bindings);
        $bindings = array_merge($is_list ? array_values($data) : $data, $bindings);
        $keys = array_keys($data);
        foreach ($keys as $v) {
            // подстраитваемся под стиль плейсхолдеров
            $set[] = $t->quote_name($v) . '=' . ($is_list ? '?' : ":$v");
        }
        $set = implode(',', $set);
        $table = $t->quote_name($table);
        return $t->execute("UPDATE $table SET $set WHERE $where", $bindings);
    }

    public function delete($table, $where=1, array $bindings=[]) {
        $t = $this;
        $table = $t->quote_name($table);
        list($where, $bindings) = $t->get_where($where, $bindings);
        return $t->execute("DELETE FROM $table WHERE $where", $bindings);
    }

    protected function get_where($criteria, $bindings) {
        if (is_array($criteria)) {
            $bindings = [];
            $parts = [];
            foreach ($criteria as $k => $v) {
                $parts[] = $this->quote_name($k) . '=?';
                $bindings[] = $v;
            }
            $criteria = implode($parts, ' AND ');
        }
        return [$criteria, $bindings];
    }

    public function query($query) {
        return $this->pdo->query($query);
    }

    public function exec($query) {
        return $this->pdo->exec($query);
    }

    public function quote($s) {
        return $this->pdo->quote($s);
    }

    public function commit() {
        return $this->pdo->commit();
    }

    public function rollback() {
        return $this->pdo->rollback();
    }

    public function last_insert_id() {
        return $this->pdo->lastInsertId();
    }

    public function clear_cache() {
        $this->prepared_statements = [];
    }
}

if (!function_exists('is_list')) {
    function is_list($arr) {
        return $arr === array_values($arr);
    }
}