<?php

/**
 * Stream-write arrays onto a file on disk as JSON format, to avoid memory leaks.
 * Written expressly for /u/devourment77 of reddit.
 *
 * Copyright (C) 2021 by Vynatu Cyberlabs, Inc. and Felix Lebel
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright
 * notice and this permission notice shall be included in all copies or substantial portions of the Software. THE
 * SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * @author     Felix Lebel <felix@vynatu.io>
 * @copyright  2019-2021 Vynatu Cyberlabs, Inc.
 * @license    https://opensource.org/licenses/MIT  MIT License
 */

namespace App\Services;

class JsonModelStreamWriter
{
    const ARR_OPEN = "[";
    const ARR_CLOSE = "]";
    const OBJ_OPEN = "{";
    const OBJ_CLOSE = "}";
    const COLON = ":";
    const COMMA = ",";

    /**
     * The open file resource.
     *
     * @var resource
     */
    private $resource;

    /**
     * Whether the resource was closed. Prevents redundant is_resource() calls.
     *
     * @var bool
     */
    private $is_closed;

    private $wrote_at_least_once = false;

    public function __construct(string $filename)
    {
        $this->resource = fopen($filename, 'w+');
        fwrite($this->resource, self::ARR_OPEN);
        $this->is_closed = false;
    }

    /**
     * Write an array to the disk without buffering.
     *
     * @param array $array The key => value array to stream-write to the disk
     */
    public function writeArray(array $array)
    {
        if ($this->is_closed) {
            return;
        }

        $temp_string = "";

        if ($this->wrote_at_least_once) {
            $temp_string .= self::COMMA;
        }

        $temp_string .= self::OBJ_OPEN;

        $wrote_first_key = false;

        foreach ($array as $key => $value) {
            $json_key = json_encode((string)$key); // JSON Keys can only be strings.
            $json_value = $this->getValidJsonValue($value);

            if ($json_value === null) {
                continue;
            }

            if ($wrote_first_key) {
                $temp_string .= self::COMMA;
            }

            $temp_string .= $json_key . self::COLON . $json_value;

            $wrote_first_key = true;
        }

        if ($wrote_first_key) {
            $temp_string .= self::OBJ_CLOSE;
            fwrite($this->resource, $temp_string);
            $this->wrote_at_least_once = true;
        }
    }

    public function close()
    {
        fwrite($this->resource, self::ARR_CLOSE);
        fclose($this->resource);
        $this->is_closed = true;
    }

    private function getValidJsonValue($value)
    {
        if (is_object($value) || is_array($value)) {
            return null;
        }

        return json_encode($value);
    }
}