<?php
/**
 * Provides the model class, an abstract interface to a database table
 *
 * @author Camil Staps
 *
 * BusinessAdmin: administrative software for small companies
 * Copyright (C) 2015 Camil Staps (ViviSoft)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * Thrown in Model when a table row could not be found
 */
class ModelNotFoundException extends Exception {
}

/**
 * Thrown in Model when a column cannot be edited
 */
class ModelIllegalAccessException extends Exception {
}

/**
 * Thrown in Model when a call to __set() fails
 */
class ModelSetFailedException extends Exception {
}

/**
 * An abstract interface to a database table
 */
abstract class Model {
	/**
	 * @var string   $table              The database table
	 * @var string   $primary_key        The table's primary key
	 * @var string[] $protected_columns  Columns that cannot be edited
	 * @var string[] $fillable_columns   Columns that can be edited
	 * @var string[] $timestamps         Columns that are TIMESTAMPs (special treatment in accessor and mutator)
	 * @var string[] $dates              Columns that are DATEs (special treatment in accessor and mutator)
	 * @var string[] $booleans           Columns that are BOOLEANs (special treatment in accessor and mutator)
	 */
	public static
		$table             = '',
		$primary_key       = 'id',
		$protected_columns = ['id'],
		$fillable_columns  = [],
		$timestamps        = [],
		$dates             = [],
		$booleans          = [];

	/**
	 * @var PDO $pdo              A PDO instance for database communication
	 * @var mixed[] $data         The column values
	 */
	protected $pdo, $data;

	/**
	 * Create a new instance
	 *
	 * @param PDO $pdo              The PDO class, to access the database
	 * @param int $id               The id of the row to fetch
	 *
	 * @throws PDOException         If something went wrong with the database
	 * @throws ModelNotFoundException If the id could not be found
	 */
	public function __construct($pdo, $id) {
		$this->pdo = $pdo;

		$stmt = $this->pdo->prepare("SELECT * FROM `".self::table()."` WHERE `".static::$primary_key."`=?");
		$stmt->execute([$id]);
		if ($stmt->rowCount() == 0) {
			throw new ModelNotFoundException("The ".static::$table." with id '$id' could not be found.");
		}
		$this->data = $stmt->fetch(PDO::FETCH_ASSOC);
	}

	/**
	 * Set a column value
	 *
	 * @param string $key         The column
	 * @param mixed $value        The value
	 *
	 * @throws PDOException       Database error
	 */
	public function __set($key, $value) {
		if (!in_array($key, static::$fillable_columns)) {
			throw new ModelIllegalAccessException("Column `".self::table()."`.`$key` cannot be edited.");
		}
		if ($this->data[$key] == $value) {
			return;
		}
		$stmt = $this->pdo->prepare("UPDATE `".self::table()."` SET `$key`=? WHERE `".static::$primary_key."`=?");
		$stmt->execute([
			$this->mutator($key, $value),
			$this->data[static::$primary_key]
		]);
		if ($stmt->rowCount() != 1) {
			throw new ModelEditFailedException("Failed to update `".self::table()."`.`$key` to '$value'.");
		}
		$this->data[$key] = $value;
	}

	/**
	 * Get a column value
	 *
	 * @param string $key         The column
	 *
	 * @return mixed              The value
	 */
	public function __get($key) {
		return $this->accessor($key, $this->data[$key]);
	}

	/**
	 * Create a new row
	 *
	 * @param PDO $pdo            Database connection
	 * @param mixed[] $values     The column values, in the order of $fillable_columns
	 *
	 * @throws PDOException       Database error
	 *
	 * @return self               The new item
	 */
	public static function create($pdo, $values) {
		$class = get_called_class();

		$columns = array_combine(static::$fillable_columns, $values);
		$questions = [];

		foreach ($columns as $column => $value) {
			$columns[$column] = $class::mutator($column, $value);
			$questions[] = '?';
		}

		$stmt = $pdo->prepare(
			"INSERT INTO `".self::table()."` " .
			"(`" . implode('`, `', array_keys($columns)) . "`) " .
			"VALUES (" . implode(',', $questions) . ")");
		$stmt->execute(array_values($columns));
		
		return new $class($pdo, $pdo->lastInsertId());
	}

	/**
	 * Search for rows, return only ids
	 *
	 * @param PDO $pdo            Database connection
	 * @param string[] $where     Where clauses, to be ANDed
	 * @param mixed[] $values     Variables to bind to the where clauses
	 *
	 * @throws PDOException       Database error
	 * 
	 * @return int[]              Array of ids
	 */
	public static function searchIds($pdo, $where = [], $values = []) {
		$stmt = $pdo->prepare("SELECT `id` FROM `".static::table()."`" . ((count($where) > 0) ? (" WHERE (" . implode(') AND (', $where) . ")") : ""));
		$stmt->execute($values);

		$ids = [];
		foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
			$ids[] = $row['id'];
		}
		return $ids;
	}

	/**
	 * Search for rows
	 *
	 * @param PDO $pdo            Database connection
	 * @param string[] $where     Where clauses, to be ANDed
	 * @param mixed[] $values     Variables to bind to the where clauses
	 *
	 * @throws PDOException       Database error
	 * 
	 * @return self[]             Array of rows
	 */
	public static function search($pdo, $where = [], $values = []) {
		$class = get_called_class();

		$items = [];
		foreach (self::searchIds($pdo, $where, $values) as $id) {
			$items[] = new $class($pdo, $id);
		}
		return $items;
	}

	/**
	 * Number of matching rows
	 *
	 * @param PDO $pdo            Database connection
	 * @param string[] $where     Where clauses, to be ANDed
	 * @param mixed[] $values     Variables to bind to the where clauses
	 *
	 * @throws PDOException       Database error
	 * 
	 * @return int                The number of matching rows
	 */
	public static function count($pdo, $where = [], $values = []) {
		$class = get_called_class();

		$stmt = $pdo->prepare("SELECT COUNT(*) FROM `".static::table()."`" . ((count($where) > 0) ? (" WHERE (" . implode(') AND (', $where) . ")") : ""));
		$stmt->execute($values);

		return $stmt->fetchColumn();
	}

	/**
	 * Post-__get() hook to modify the value
	 *
	 * @param string $key         The column
	 * @param string $value       The value
	 *
	 * @return mixed              The modified value
	 */
	protected static function accessor($key, $value) {
		if (is_null($value)) {
			return null;
		} elseif (in_array($key, static::$booleans)) {
			return (bool) $value;
		} elseif (in_array($key, static::$dates) || in_array($key, static::$timestamps)) {
			return strtotime($value);
		} else {
			return $value;
		}
	}

	/**
	 * Pre-__set() hook to modify a value
	 *
	 * @param string $key         The column
	 * @param mixed $value        The value
	 *
	 * @return string             The modified value
	 */
	protected static function mutator($key, $value) {
		if (in_array($key, static::$dates) && is_int($value)) {
			return date('Y-m-d', $value);
		} elseif (in_array($key, static::$timestamps) && is_int($value)) {
			return date('Y-m-d H:i:s', $value);
		} else {
			return (string) $value;
		}
	}

	/**
	 * Delete the row
	 *
	 * @throws PDOException       Database error
	 *
	 * @return bool               True iff the row was really deleted
	 */
	public function delete() {
		$stmt = $this->pdo->prepare("DELETE FROM `".self::table()."` WHERE `".static::$primary_key."`=?");
		$stmt->execute([$this->data[static::$primary_key]]);
		return $stmt->rowCount() != 0;
	}

	/**
	 * The actual table, after adding prefixes and the like
	 *
	 * @return string The database table
	 */
	private static function table() {
		return Constants::db_prefix . static::$table;
	}
}