<?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       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\Datasource;

use BadMethodCallException;
use Cake\Collection\Iterator\MapReduce;
use Cake\Datasource\Exception\RecordNotFoundException;

/**
 * Contains the characteristics for an object that is attached to a repository and
 * can retrieve results based on any criteria.
 *
 */
trait QueryTrait
{

    /**
     * Instance of a table object this query is bound to
     *
     * @var \Cake\Datasource\RepositoryInterface
     */
    protected $_repository;

    /**
     * A ResultSet.
     *
     * When set, query execution will be bypassed.
     *
     * @var \Cake\Datasource\ResultSetInterface
     * @see setResult()
     */
    protected $_results;

    /**
     * List of map-reduce routines that should be applied over the query
     * result
     *
     * @var array
     */
    protected $_mapReduce = [];

    /**
     * List of formatter classes or callbacks that will post-process the
     * results when fetched
     *
     * @var array
     */
    protected $_formatters = [];

    /**
     * A query cacher instance if this query has caching enabled.
     *
     * @var \Cake\Datasource\QueryCacher
     */
    protected $_cache;

    /**
     * Holds any custom options passed using applyOptions that could not be processed
     * by any method in this class.
     *
     * @var array
     */
    protected $_options = [];

    /**
     * Whether the query is standalone or the product of an eager load operation.
     *
     * @var bool
     */
    protected $_eagerLoaded = false;

    /**
     * Returns the default table object that will be used by this query,
     * that is, the table that will appear in the from clause.
     *
     * When called with a Table argument, the default table object will be set
     * and this query object will be returned for chaining.
     *
     * @param \Cake\Datasource\RepositoryInterface|null $table The default table object to use
     * @return \Cake\Datasource\RepositoryInterface|$this
     */
    public function repository(RepositoryInterface $table = null)
    {
        if ($table === null) {
            return $this->_repository;
        }
        $this->_repository = $table;
        return $this;
    }

    /**
     * Set the result set for a query.
     *
     * Setting the resultset of a query will make execute() a no-op. Instead
     * of executing the SQL query and fetching results, the ResultSet provided to this
     * method will be returned.
     *
     * This method is most useful when combined with results stored in a persistent cache.
     *
     * @param \Cake\Datasource\ResultSetInterface $results The results this query should return.
     * @return $this The query instance.
     */
    public function setResult($results)
    {
        $this->_results = $results;
        return $this;
    }

    /**
     * Executes this query and returns a results iterator. This function is required
     * for implementing the IteratorAggregate interface and allows the query to be
     * iterated without having to call execute() manually, thus making it look like
     * a result set instead of the query itself.
     *
     * @return \Iterator
     */
    public function getIterator()
    {
        return $this->all();
    }

    /**
     * Enable result caching for this query.
     *
     * If a query has caching enabled, it will do the following when executed:
     *
     * - Check the cache for $key. If there are results no SQL will be executed.
     *   Instead the cached results will be returned.
     * - When the cached data is stale/missing the result set will be cached as the query
     *   is executed.
     *
     * ### Usage
     *
     * ```
     * // Simple string key + config
     * $query->cache('my_key', 'db_results');
     *
     * // Function to generate key.
     * $query->cache(function ($q) {
     *   $key = serialize($q->clause('select'));
     *   $key .= serialize($q->clause('where'));
     *   return md5($key);
     * });
     *
     * // Using a pre-built cache engine.
     * $query->cache('my_key', $engine);
     *
     * // Disable caching
     * $query->cache(false);
     * ```
     *
     * @param false|string|\Closure $key Either the cache key or a function to generate the cache key.
     *   When using a function, this query instance will be supplied as an argument.
     * @param string|\Cake\Cache\CacheEngine $config Either the name of the cache config to use, or
     *   a cache config instance.
     * @return $this This instance
     */
    public function cache($key, $config = 'default')
    {
        if ($key === false) {
            $this->_cache = null;
            return $this;
        }
        $this->_cache = new QueryCacher($key, $config);
        return $this;
    }

    /**
     * Sets the query instance to be an eager loaded query. If no argument is
     * passed, the current configured query `_eagerLoaded` value is returned.
     *
     * @param bool|null $value Whether or not to eager load.
     * @return $this|\Cake\ORM\Query
     */
    public function eagerLoaded($value = null)
    {
        if ($value === null) {
            return $this->_eagerLoaded;
        }
        $this->_eagerLoaded = $value;
        return $this;
    }

    /**
     * Returns a key => value array representing a single aliased field
     * that can be passed directly to the select() method.
     * The key will contain the alias and the value the actual field name.
     *
     * If the field is already aliased, then it will not be changed.
     * If no $alias is passed, the default table for this query will be used.
     *
     * @param string $field The field to alias
     * @param string $alias the alias used to prefix the field
     * @return array
     */
    public function aliasField($field, $alias = null)
    {
        $namespaced = strpos($field, '.') !== false;
        $aliasedField = $field;

        if ($namespaced) {
            list($alias, $field) = explode('.', $field);
        }

        if (!$alias) {
            $alias = $this->repository()->alias();
        }

        $key = sprintf('%s__%s', $alias, $field);
        if (!$namespaced) {
            $aliasedField = $alias . '.' . $field;
        }

        return [$key => $aliasedField];
    }

    /**
     * Runs `aliasField()` for each field in the provided list and returns
     * the result under a single array.
     *
     * @param array $fields The fields to alias
     * @param string|null $defaultAlias The default alias
     * @return array
     */
    public function aliasFields($fields, $defaultAlias = null)
    {
        $aliased = [];
        foreach ($fields as $alias => $field) {
            if (is_numeric($alias) && is_string($field)) {
                $aliased += $this->aliasField($field, $defaultAlias);
                continue;
            }
            $aliased[$alias] = $field;
        }

        return $aliased;
    }

    /**
     * Fetch the results for this query.
     *
     * Will return either the results set through setResult(), or execute this query
     * and return the ResultSetDecorator object ready for streaming of results.
     *
     * ResultSetDecorator is a traversable object that implements the methods found
     * on Cake\Collection\Collection.
     *
     * @return \Cake\Datasource\ResultSetInterface
     */
    public function all()
    {
        if (isset($this->_results)) {
            return $this->_results;
        }

        if ($this->_cache) {
            $results = $this->_cache->fetch($this);
        }
        if (!isset($results)) {
            $results = $this->_decorateResults($this->_execute());
            if ($this->_cache) {
                $this->_cache->store($this, $results);
            }
        }
        $this->_results = $results;
        return $this->_results;
    }

    /**
     * Returns an array representation of the results after executing the query.
     *
     * @return array
     */
    public function toArray()
    {
        return $this->all()->toArray();
    }

    /**
     * Register a new MapReduce routine to be executed on top of the database results
     * Both the mapper and caller callable should be invokable objects.
     *
     * The MapReduce routing will only be run when the query is executed and the first
     * result is attempted to be fetched.
     *
     * If the first argument is set to null, it will return the list of previously
     * registered map reduce routines.
     *
     * If the third argument is set to true, it will erase previous map reducers
     * and replace it with the arguments passed.
     *
     * @param callable|null $mapper The mapper callable.
     * @param callable|null $reducer The reducing function.
     * @param bool $overwrite Set to true to overwrite existing map + reduce functions.
     * @return $this|array
     * @see \Cake\Collection\Iterator\MapReduce for details on how to use emit data to the map reducer.
     */
    public function mapReduce(callable $mapper = null, callable $reducer = null, $overwrite = false)
    {
        if ($overwrite) {
            $this->_mapReduce = [];
        }
        if ($mapper === null) {
            return $this->_mapReduce;
        }
        $this->_mapReduce[] = compact('mapper', 'reducer');
        return $this;
    }

    /**
     * Registers a new formatter callback function that is to be executed when trying
     * to fetch the results from the database.
     *
     * Formatting callbacks will get a first parameter, a `ResultSetDecorator`, that
     * can be traversed and modified at will.
     *
     * Callbacks are required to return an iterator object, which will be used as
     * the return value for this query's result. Formatter functions are applied
     * after all the `MapReduce` routines for this query have been executed.
     *
     * If the first argument is set to null, it will return the list of previously
     * registered map reduce routines.
     *
     * If the second argument is set to true, it will erase previous formatters
     * and replace them with the passed first argument.
     *
     * ### Example:
     *
     * ```
     * // Return all results from the table indexed by id
     * $query->select(['id', 'name'])->formatResults(function ($results) {
     *   return $results->indexBy('id');
     * });
     *
     * // Add a new column to the ResultSet
     * $query->select(['name', 'birth_date'])->formatResults(function ($results) {
     *   return $results->map(function ($row) {
     *     $row['age'] = $row['birth_date']->diff(new DateTime)->y;
     *     return $row;
     *   });
     * });
     * ```
     *
     * @param callable|null $formatter The formatting callable.
     * @param bool|int $mode Whether or not to overwrite, append or prepend the formatter.
     * @return $this|array
     */
    public function formatResults(callable $formatter = null, $mode = 0)
    {
        if ($mode === self::OVERWRITE) {
            $this->_formatters = [];
        }
        if ($formatter === null) {
            return $this->_formatters;
        }

        if ($mode === self::PREPEND) {
            array_unshift($this->_formatters, $formatter);
            return $this;
        }

        $this->_formatters[] = $formatter;
        return $this;
    }

    /**
     * Returns the first result out of executing this query, if the query has not been
     * executed before, it will set the limit clause to 1 for performance reasons.
     *
     * ### Example:
     *
     * ```
     * $singleUser = $query->select(['id', 'username'])->first();
     * ```
     *
     * @return mixed the first result from the ResultSet
     */
    public function first()
    {
        if ($this->_dirty) {
            $this->limit(1);
        }
        return $this->all()->first();
    }

    /**
     * Get the first result from the executing query or raise an exception.
     *
     * @throws \Cake\Datasource\Exception\RecordNotFoundException When there is no first record.
     * @return mixed The first result from the ResultSet.
     */
    public function firstOrFail()
    {
        $entity = $this->first();
        if ($entity) {
            return $entity;
        }
        throw new RecordNotFoundException(sprintf(
            'Record not found in table "%s"',
            $this->repository()->table()
        ));
    }

    /**
     * Returns an array with the custom options that were applied to this query
     * and that were not already processed by another method in this class.
     *
     * ### Example:
     *
     * ```
     *  $query->applyOptions(['doABarrelRoll' => true, 'fields' => ['id', 'name']);
     *  $query->getOptions(); // Returns ['doABarrelRoll' => true]
     * ```
     *
     * @see \Cake\ORM\Query::applyOptions() to read about the options that will
     * be processed by this class and not returned by this function
     * @return array
     */
    public function getOptions()
    {
        return $this->_options;
    }

    /**
     * Enables calling methods from the result set as if they were from this class
     *
     * @param string $method the method to call
     * @param array $arguments list of arguments for the method to call
     * @return mixed
     * @throws \BadMethodCallException if no such method exists in result set
     */
    public function __call($method, $arguments)
    {
        $resultSetClass = $this->_decoratorClass();
        if (in_array($method, get_class_methods($resultSetClass))) {
            $results = $this->all();
            return call_user_func_array([$results, $method], $arguments);
        }
        throw new BadMethodCallException(
            sprintf('Unknown method "%s"', $method)
        );
    }

    /**
     * Populates or adds parts to current query clauses using an array.
     * This is handy for passing all query clauses at once.
     *
     * @param array $options the options to be applied
     * @return $this This object
     */
    abstract public function applyOptions(array $options);

    /**
     * Executes this query and returns a traversable object containing the results
     *
     * @return \Traversable
     */
    abstract protected function _execute();

    /**
     * Decorates the results iterator with MapReduce routines and formatters
     *
     * @param \Traversable $result Original results
     * @return \Cake\Datasource\ResultSetInterface
     */
    protected function _decorateResults($result)
    {
        $decorator = $this->_decoratorClass();
        foreach ($this->_mapReduce as $functions) {
            $result = new MapReduce($result, $functions['mapper'], $functions['reducer']);
        }

        if (!empty($this->_mapReduce)) {
            $result = new $decorator($result);
        }

        foreach ($this->_formatters as $formatter) {
            $result = $formatter($result);
        }

        if (!empty($this->_formatters) && !($result instanceof $decorator)) {
            $result = new $decorator($result);
        }

        return $result;
    }

    /**
     * Returns the name of the class to be used for decorating results
     *
     * @return string
     */
    protected function _decoratorClass()
    {
        return 'Cake\Datasource\ResultSetDecorator';
    }
}
