<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Helper;

use Kant\Exception\InvalidParamException;
use Kant\Foundation\Arrayable;
use Kant\Helper\JsExpression;

/**
 * BaseJson provides concrete implementation for [[Json]].
 *
 * Do not use BaseJson. Use [[Json]] instead.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class BaseJson
{

    /**
     * List of JSON Error messages assigned to constant names for better handling of version differences
     * 
     * @var array
     * @since 2.0.7
     */
    public static $jsonErrorMessages = [
        'JSON_ERROR_DEPTH' => 'The maximum stack depth has been exceeded.',
        'JSON_ERROR_STATE_MISMATCH' => 'Invalid or malformed JSON.',
        'JSON_ERROR_CTRL_CHAR' => 'Control character error, possibly incorrectly encoded.',
        'JSON_ERROR_SYNTAX' => 'Syntax error.',
        'JSON_ERROR_UTF8' => 'Malformed UTF-8 characters, possibly incorrectly encoded.', // PHP 5.3.3
        'JSON_ERROR_RECURSION' => 'One or more recursive references in the value to be encoded.', // PHP 5.5.0
        'JSON_ERROR_INF_OR_NAN' => 'One or more NAN or INF values in the value to be encoded', // PHP 5.5.0
        'JSON_ERROR_UNSUPPORTED_TYPE' => 'A value of a type that cannot be encoded was given'
    ] // PHP 5.5.0
;

    /**
     * Encodes the given value into a JSON string.
     * The method enhances `json_encode()` by supporting JavaScript expressions.
     * In particular, the method will not encode a JavaScript expression that is
     * represented in terms of a [[JsExpression]] object.
     * 
     * @param mixed $value
     *            the data to be encoded.
     * @param integer $options
     *            the encoding options. For more details please refer to
     *            <http://www.php.net/manual/en/function.json-encode.php>. Default is `JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE`.
     * @return string the encoding result.
     * @throws InvalidParamException if there is any encoding error.
     */
    public static function encode($value, $options = 320)
    {
        $expressions = [];
        $value = static::processData($value, $expressions, uniqid('', true));
        set_error_handler(function () {
            static::handleJsonError(JSON_ERROR_SYNTAX);
        }, E_WARNING);
        $json = json_encode($value, $options);
        restore_error_handler();
        static::handleJsonError(json_last_error());
        
        return $expressions === [] ? $json : strtr($json, $expressions);
    }

    /**
     * Encodes the given value into a JSON string HTML-escaping entities so it is safe to be embedded in HTML code.
     * The method enhances `json_encode()` by supporting JavaScript expressions.
     * In particular, the method will not encode a JavaScript expression that is
     * represented in terms of a [[JsExpression]] object.
     *
     * @param mixed $value
     *            the data to be encoded
     * @return string the encoding result
     * @since 2.0.4
     * @throws InvalidParamException if there is any encoding error
     */
    public static function htmlEncode($value)
    {
        return static::encode($value, JSON_UNESCAPED_UNICODE | JSON_HEX_QUOT | JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS);
    }

    /**
     * Decodes the given JSON string into a PHP data structure.
     * 
     * @param string $json
     *            the JSON string to be decoded
     * @param boolean $asArray
     *            whether to return objects in terms of associative arrays.
     * @return mixed the PHP data
     * @throws InvalidParamException if there is any decoding error
     */
    public static function decode($json, $asArray = true)
    {
        if (is_array($json)) {
            throw new InvalidParamException('Invalid JSON data.');
        } elseif ($json === null || $json === '') {
            return null;
        }
        $decode = json_decode((string) $json, $asArray);
        static::handleJsonError(json_last_error());
        
        return $decode;
    }

    /**
     * Handles [[encode()]] and [[decode()]] errors by throwing exceptions with the respective error message.
     *
     * @param integer $lastError
     *            error code from [json_last_error()](http://php.net/manual/en/function.json-last-error.php).
     * @throws \Kant\Exception\InvalidParamException if there is any encoding/decoding error.
     * @since 2.0.6
     */
    protected static function handleJsonError($lastError)
    {
        if ($lastError === JSON_ERROR_NONE) {
            return;
        }
        
        $availableErrors = [];
        foreach (static::$jsonErrorMessages as $const => $message) {
            if (defined($const)) {
                $availableErrors[constant($const)] = $message;
            }
        }
        
        if (isset($availableErrors[$lastError])) {
            throw new InvalidParamException($availableErrors[$lastError], $lastError);
        }
        
        throw new InvalidParamException('Unknown JSON encoding/decoding error.');
    }

    /**
     * Pre-processes the data before sending it to `json_encode()`.
     * 
     * @param mixed $data
     *            the data to be processed
     * @param array $expressions
     *            collection of JavaScript expressions
     * @param string $expPrefix
     *            a prefix internally used to handle JS expressions
     * @return mixed the processed data
     */
    protected static function processData($data, &$expressions, $expPrefix)
    {
        if (is_object($data)) {
            if ($data instanceof JsExpression) {
                $token = "!{[$expPrefix=" . count($expressions) . ']}!';
                $expressions['"' . $token . '"'] = $data->expression;
                
                return $token;
            } elseif ($data instanceof \JsonSerializable) {
                $data = $data->jsonSerialize();
            } elseif ($data instanceof Arrayable) {
                $data = $data->toArray();
            } elseif ($data instanceof \SimpleXMLElement) {
                $data = (array) $data;
            } else {
                $result = [];
                foreach ($data as $name => $value) {
                    $result[$name] = $value;
                }
                $data = $result;
            }
            
            if ($data === []) {
                return new \stdClass();
            }
        }
        
        if (is_array($data)) {
            foreach ($data as $key => $value) {
                if (is_array($value) || is_object($value)) {
                    $data[$key] = static::processData($value, $expressions, $expPrefix);
                }
            }
        }
        
        return $data;
    }
}
