<?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;
    }
}