<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         3.0.0
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */
namespace Cake\Database\Expression;

use Cake\Database\ExpressionInterface;
use Cake\Database\Query;
use Cake\Database\TypeMap;
use Cake\Database\TypeMapTrait;
use Cake\Database\ValueBinder;
use \Countable;

/**
 * Represents a SQL Query expression. Internally it stores a tree of
 * expressions that can be compiled by converting this object to string
 * and will contain a correctly parenthesized and nested expression.
 *
 */
class QueryExpression implements ExpressionInterface, Countable {

	use TypeMapTrait;

/**
 * String to be used for joining each of the internal expressions
 * this object internally stores for example "AND", "OR", etc.
 *
 * @var string
 */
	protected $_conjunction;

/**
 * A list of strings or other expression objects that represent the "branches" of
 * the expression tree. For example one key of the array might look like "sum > :value"
 *
 * @var array
 */
	protected $_conditions = [];

/**
 * Constructor. A new expression object can be created without any params and
 * be built dynamically. Otherwise it is possible to pass an array of conditions
 * containing either a tree-like array structure to be parsed and/or other
 * expression objects. Optionally, you can set the conjunction keyword to be used
 * for joining each part of this level of the expression tree.
 *
 * @param array $conditions tree-like array structure containing all the conditions
 * to be added or nested inside this expression object.
 * @param array|TypeMap $types associative array of types to be associated with the values
 * passed in $conditions.
 * @param string $conjunction the glue that will join all the string conditions at this
 * level of the expression tree. For example "AND", "OR", "XOR"...
 * @param TypeMap $typeMap contains default and call specific type mapping
 * @see QueryExpression::add() for more details on $conditions and $types
 */
	public function __construct($conditions = [], $types = [], $conjunction = 'AND') {
		$this->typeMap($types);
		$this->type(strtoupper($conjunction));
		if (!empty($conditions)) {
			$this->add($conditions, $this->typeMap()->types());
		}
	}

/**
 * Changes the conjunction for the conditions at this level of the expression tree.
 * If called with no arguments it will return the currently configured value.
 *
 * @param string $conjunction value to be used for joining conditions. If null it
 * will not set any value, but return the currently stored one
 * @return string|QueryExpression
 */
	public function type($conjunction = null) {
		if ($conjunction === null) {
			return $this->_conjunction;
		}

		$this->_conjunction = strtoupper($conjunction);
		return $this;
	}

/**
 * Adds one or more conditions to this expression object. Conditions can be
 * expressed in a one dimensional array, that will cause all conditions to
 * be added directly at this level of the tree or they can be nested arbitrarily
 * making it create more expression objects that will be nested inside and
 * configured to use the specified conjunction.
 *
 * If the type passed for any of the fields is expressed "type[]" (note braces)
 * then it will cause the placeholder to be re-written dynamically so if the
 * value is an array, it will create as many placeholders as values are in it.
 *
 * @param string|array|QueryExpression $conditions single or multiple conditions to
 * be added. When using and array and the key is 'OR' or 'AND' a new expression
 * object will be created with that conjunction and internal array value passed
 * as conditions.
 * @param array $types associative array of fields pointing to the type of the
 * values that are being passed. Used for correctly binding values to statements.
 * @see \Cake\Database\Query::where() for examples on conditions
 * @return QueryExpression
 */
	public function add($conditions, $types = []) {
		if (is_string($conditions)) {
			$this->_conditions[] = $conditions;
			return $this;
		}

		if ($conditions instanceof ExpressionInterface) {
			$this->_conditions[] = $conditions;
			return $this;
		}

		$this->_addConditions($conditions, $types);
		return $this;
	}

/**
 * Adds a new condition to the expression object in the form "field = value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * If it is suffixed with "[]" and the value is an array then multiple placeholders
 * will be created, one per each value in the array.
 * @return QueryExpression
 */
	public function eq($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '='));
	}

/**
 * Adds a new condition to the expression object in the form "field != value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * If it is suffixed with "[]" and the value is an array then multiple placeholders
 * will be created, one per each value in the array.
 * @return QueryExpression
 */
	public function notEq($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '!='));
	}

/**
 * Adds a new condition to the expression object in the form "field > value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function gt($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '>'));
	}

/**
 * Adds a new condition to the expression object in the form "field < value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function lt($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '<'));
	}

/**
 * Adds a new condition to the expression object in the form "field >= value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function gte($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '>='));
	}

/**
 * Adds a new condition to the expression object in the form "field <= value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function lte($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, '<='));
	}

/**
 * Adds a new condition to the expression object in the form "field IS NULL".
 *
 * @param string $field database field to be tested for null
 * @return QueryExpression
 */
	public function isNull($field) {
		return $this->add($field . ' IS NULL');
	}

/**
 * Adds a new condition to the expression object in the form "field IS NOT NULL".
 *
 * @param string $field database field to be tested for not null
 * @return QueryExpression
 */
	public function isNotNull($field) {
		return $this->add($field . ' IS NOT NULL');
	}

/**
 * Adds a new condition to the expression object in the form "field LIKE value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function like($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, 'LIKE'));
	}

/**
 * Adds a new condition to the expression object in the form "field NOT LIKE value".
 *
 * @param string $field database field to be compared against value
 * @param mixed $value the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function notLike($field, $value, $type = null) {
		return $this->add(new Comparison($field, $value, $type, 'NOT LIKE'));
	}

/**
 * Adds a new condition to the expression object in the form
 * "field IN (value1, value2)".
 *
 * @param string $field database field to be compared against value
 * @param array $values the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function in($field, $values, $type = null) {
		$type = $type ?: 'string';
		$type .= '[]';
		$values = $values instanceof ExpressionInterface ? $values : (array)$values;
		return $this->add(new Comparison($field, $values, $type, 'IN'));
	}

/**
 * Adds a new condition to the expression object in the form
 * "field NOT IN (value1, value2)".
 *
 * @param string $field database field to be compared against value
 * @param array $values the value to be bound to $field for comparison
 * @param string $type the type name for $value as configured using the Type map.
 * @return QueryExpression
 */
	public function notIn($field, $values, $type = null) {
		$type = $type ?: 'string';
		$type .= '[]';
		$values = $values instanceof ExpressionInterface ? $values : (array)$values;
		return $this->add(new Comparison($field, $values, $type, 'NOT IN'));
	}

// @codingStandardsIgnoreStart
/**
 * Returns a new QueryExpresion object containing all the conditions passed
 * and set up the conjunction to be "AND"
 *
 * @param string|array|QueryExpression $conditions to be joined with AND
 * @param array $types associative array of fields pointing to the type of the
 * values that are being passed. Used for correctly binding values to statements.
 * @return \Cake\Database\Expression\QueryExpression
 */
	public function and_($conditions, $types = []) {
		if (is_callable($conditions)) {
			return $conditions(new self([], $this->typeMap()->types($types)));
		}
		return new self($conditions, $this->typeMap()->types($types));
	}

/**
 * Returns a new QueryExpresion object containing all the conditions passed
 * and set up the conjunction to be "OR"
 *
 * @param string|array|QueryExpression $conditions to be joined with OR
 * @param array $types associative array of fields pointing to the type of the
 * values that are being passed. Used for correctly binding values to statements.
 * @return \Cake\Database\Expression\QueryExpression
 */
	public function or_($conditions, $types = []) {
		if (is_callable($conditions)) {
			return $conditions(new self([], $this->typeMap()->types($types), 'OR'));
		}
		return new self($conditions, $this->typeMap()->types($types), 'OR');
	}
// @codingStandardsIgnoreEnd

/**
 * Adds a new set of conditions to this level of the tree and negates
 * the final result by prepending a NOT, it will look like
 * "NOT ( (condition1) AND (conditions2) )" conjunction depends on the one
 * currently configured for this object.
 *
 * @param string|array|QueryExpression $conditions to be added and negated
 * @param array $types associative array of fields pointing to the type of the
 * values that are being passed. Used for correctly binding values to statements.
 * @return QueryExpression
 */
	public function not($conditions, $types = []) {
		return $this->add(['NOT' => $conditions], $types);
	}

/**
 * Returns the number of internal conditions that are stored in this expression.
 * Useful to determine if this expression object is void or it will generate
 * a non-empty string when compiled
 *
 * @return integer
 */
	public function count() {
		return count($this->_conditions);
	}

/**
 * Returns the string representation of this object so that it can be used in a
 * SQL query. Note that values condition values are not included in the string,
 * in their place placeholders are put and can be replaced by the quoted values
 * accordingly.
 *
 * @param \Cake\Database\ValueBinder $generator Placeholder generator object
 * @return string
 */
	public function sql(ValueBinder $generator) {
		$conjunction = $this->_conjunction;
		$template = ($this->count() === 1) ? '%s' : '(%s)';
		$parts = [];
		foreach ($this->_conditions as $part) {
			if ($part instanceof ExpressionInterface) {
				$part = $part->sql($generator);
			}
			$parts[] = $part;
		}
		return sprintf($template, implode(" $conjunction ", $parts));
	}

/**
 * Traverses the tree structure of this query expression by executing a callback
 * function for each of the conditions that are included in this object.
 * Useful for compiling the final expression, or doing
 * introspection in the structure.
 *
 * Callback function receives as only argument an instance of a QueryExpression
 *
 * @param callable $callable
 * @return void
 */
	public function traverse(callable $callable) {
		foreach ($this->_conditions as $c) {
			if ($c instanceof ExpressionInterface) {
				$callable($c);
				$c->traverse($callable);
			}
		}
	}

/**
 * Executes a callable function for each of the parts that form this expression
 * Callable function is required to return a value, which will the one with
 * which the currently visited part will be replaced. If the callable function
 * returns null then the part will be discarded completely from this expression
 *
 * The callback function will receive each of the conditions as first param and
 * the key as second param. It is possible to declare the second parameter as
 * passed by reference, this will enable you to change the key under which the
 * modified part is stored.
 *
 * @param callable $callable
 * @return QueryExpression
 */
	public function iterateParts(callable $callable) {
		$parts = [];
		foreach ($this->_conditions as $k => $c) {
			$key =& $k;
			$part = $callable($c, $key);
			if ($part !== null) {
				$parts[$key] = $part;
			}
		}
		$this->_conditions = $parts;

		return $this;
	}

/**
 * Auxiliary function used for decomposing a nested array of conditions and build
 * a tree structure inside this object to represent the full SQL expression.
 * String conditions are stored directly in the conditions, while any other
 * representation is wrapped around an adequate instance or of this class.
 *
 * @param array $conditions list of conditions to be stored in this object
 * @param array $types list of types associated on fields referenced in $conditions
 * @return void
 */
	protected function _addConditions(array $conditions, array $types) {
		$operators = ['and', 'or', 'xor'];

		$typeMap = $this->typeMap()->types($types);

		foreach ($conditions as $k => $c) {
			$numericKey = is_numeric($k);

			if ($numericKey && empty($c)) {
				continue;
			}

			if ($numericKey && is_string($c)) {
				$this->_conditions[] = $c;
				continue;
			}

			if ($numericKey && is_array($c) || in_array(strtolower($k), $operators)) {
				$this->_conditions[] = new self($c, $typeMap, $numericKey ? 'AND' : $k);
				continue;
			}

			if (strtolower($k) === 'not') {
				$this->_conditions[] = new UnaryExpression(new self($c, $typeMap), [], 'NOT');
				continue;
			}

			if ($c instanceof self && count($c) > 0) {
				$this->_conditions[] = $c;
				continue;
			}

			if (!$numericKey) {
				$this->_conditions[] = $this->_parseCondition($k, $c);
			}
		}
	}

/**
 * Parses a string conditions by trying to extract the operator inside it if any
 * and finally returning either an adequate QueryExpression object or a plain
 * string representation of the condition. This function is responsible for
 * generating the placeholders and replacing the values by them, while storing
 * the value elsewhere for future binding.
 *
 * @param string $field The value from with the actual field and operator will
 * be extracted.
 * @param mixed $value The value to be bound to a placeholder for the field
 * @return string|QueryExpression
 */
	protected function _parseCondition($field, $value) {
		$operator = '=';
		$expression = $field;
		$parts = explode(' ', trim($field), 2);

		if (count($parts) > 1) {
			list($expression, $operator) = $parts;
		}

		$type = $this->typeMap()->type($expression);
		$multi = false;

		$typeMultiple = strpos($type, '[]') !== false;
		if (in_array(strtolower(trim($operator)), ['in', 'not in']) || $typeMultiple) {
			$type = $type ?: 'string';
			$type .= $typeMultiple ? null : '[]';
			$operator = $operator == '=' ? 'IN' : $operator;
			$operator = $operator == '!=' ? 'NOT IN' : $operator;
			$typeMultiple = true;
		}

		if ($typeMultiple) {
			$value = $value instanceof ExpressionInterface ? $value : (array)$value;
		}

		return new Comparison($expression, $value, $type, $operator);
	}

/**
 * Returns an array of placeholders that will have a bound value corresponding
 * to each value in the first argument.
 *
 * @param string $field database field to be used to bind values
 * @param array $values
 * @param string $type the type to be used to bind the values
 * @return array
 */
	protected function _bindMultiplePlaceholders($field, $values, $type) {
		$type = str_replace('[]', '', $type);
		$params = [];
		foreach ($values as $value) {
			$params[] = $this->_bindValue($field, $value, $type);
		}
		return implode(', ', $params);
	}

}