<?php

namespace WP_CLI\Iterators;

/**
 * @source https://gist.github.com/4060005
 */
class Table extends Query {

	/**
	 * Creates an iterator over a database table.
	 *
	 * <code>
	 * foreach( new Iterators\Table( array( 'table' => $wpdb->posts, 'fields' => array( 'ID', 'post_content' ) ) ) as $post ) {
	 *     count_words_for( $post->ID, $post->post_content );
	 * }
	 * </code>
	 *
	 * <code>
	 * foreach( new Iterators\Table( array( 'table' => $wpdb->posts, 'where' => 'ID = 8 OR post_status = "publish"' ) ) as $post ) {
	 *     …
	 * }
	 * </code>
	 *
	 * <code>
	 * foreach( new PostIterator( array( 'table' => $wpdb->posts, 'where' => array( 'post_status' => 'publish', 'post_date_gmt BETWEEN x AND y' ) ) ) as $post ) {
	 *     …
	 * }
	 * </code>
	 *
	 * @param array $args Supported arguments:
	 *      table – the name of the database table
	 *      fields – an array of columns to get from the table, '*' is a valid value and the default
	 *      where – conditions for filtering rows. Supports two formats:
	 *              = string – this will be the where clause
	 *              = array – each element is treated as a condition if it's positional, or as column => value if
	 *                it's a key/value pair. In the latter case the value is automatically quoted and escaped
	 *      append - add arbitrary extra SQL
	 */
	public function __construct( $args = [] ) {
		$defaults = [
			'fields'     => '*',
			'where'      => [],
			'append'     => '',
			'table'      => null,
			'chunk_size' => 500,
		];
		$table    = $args['table'];
		$args     = array_merge( $defaults, $args );

		$fields     = self::build_fields( $args['fields'] );
		$conditions = self::build_where_conditions( $args['where'] );
		$where_sql  = $conditions ? " WHERE $conditions" : '';
		$query      = "SELECT $fields FROM `$table` $where_sql {$args['append']}";

		parent::__construct( $query, $args['chunk_size'] );
	}

	private static function build_fields( $fields ) {
		if ( '*' === $fields ) {
			return $fields;
		}

		return implode(
			', ',
			array_map(
				function ( $v ) {
					return "`$v`";
				},
				$fields
			)
		);
	}

	private static function build_where_conditions( $where ) {
		global $wpdb;
		if ( is_array( $where ) ) {
			$conditions = [];
			foreach ( $where as $key => $value ) {
				if ( is_array( $value ) ) {
					$conditions[] = $key . ' IN (' . esc_sql( implode( ',', $value ) ) . ')';
				} elseif ( is_numeric( $key ) ) {
					$conditions[] = $value;
				} else {
					$conditions[] = $key . $wpdb->prepare( ' = %s', $value );
				}
			}
			$where = implode( ' AND ', $conditions );
		}
		return $where;
	}
}