<?php

namespace App\Support;

use App\Models\Application;
use App\Models\SignupChannel;
use InvalidArgumentException;

class ChannelCallbackUrlBuilder
{
    /**
     * 回跳签名原文固定为以下字段顺序，使用 trim 后的原始值，不做 URL 编码：
     * state={state}&channel_code={channel_code}&application_id={application_id}&status={status}&submitted_at={submitted_at}&secret={shared_secret}
     */
    public static function build(Application $application, SignupChannel $channel): string
    {
        $callbackUrl = trim((string) $channel->success_callback_url);
        if ($callbackUrl === '') {
            throw new InvalidArgumentException('Callback URL is missing.');
        }

        if (! filter_var($callbackUrl, FILTER_VALIDATE_URL)) {
            throw new InvalidArgumentException('Callback URL is invalid.');
        }

        $parts = parse_url($callbackUrl);
        if (! is_array($parts)
            || ! in_array(strtolower((string) ($parts['scheme'] ?? '')), ['http', 'https'], true)
            || trim((string) ($parts['host'] ?? '')) === '') {
            throw new InvalidArgumentException('Callback URL must use HTTP or HTTPS.');
        }

        if ($application->submitted_at === null) {
            throw new InvalidArgumentException('Application submission timestamp is missing.');
        }

        $parameters = self::parameters($application, $channel);

        $query = self::mergeQuery((string) ($parts['query'] ?? ''), $parameters);
        unset($parts['query']);
        $fragment = isset($parts['fragment']) ? '#'.$parts['fragment'] : '';
        unset($parts['fragment']);

        return self::assembleUrl($parts).'?'.$query.$fragment;
    }

    public static function buildMiniProgramPath(
        Application $application,
        SignupChannel $channel,
        bool $appendParameters = true
    ): string
    {
        $path = trim((string) $channel->mini_program_callback_path);
        if ($path === '' || ! preg_match('/^\/(?!\/)[^#]*$/', $path)) {
            throw new InvalidArgumentException('Mini program callback path is invalid.');
        }

        [$basePath, $existingQuery] = array_pad(explode('?', $path, 2), 2, '');
        if (! $appendParameters) {
            return $basePath;
        }

        $query = self::mergeQuery($existingQuery, self::parameters($application, $channel));

        return $basePath.'?'.$query;
    }

    /**
     * @return array{state: string, channel_code: string, application_id: string, status: string, submitted_at: string, hash: string}
     */
    private static function parameters(Application $application, SignupChannel $channel): array
    {
        if ($application->submitted_at === null) {
            throw new InvalidArgumentException('Application submission timestamp is missing.');
        }

        $parameters = [
            'state' => trim((string) $application->signup_channel_state),
            'channel_code' => trim((string) $channel->channel_code),
            'application_id' => (string) $application->getKey(),
            'status' => 'submitted',
            'submitted_at' => $application->submitted_at->toIso8601String(),
        ];
        $parameters['hash'] = self::signature($parameters, $channel->shared_secret);

        return $parameters;
    }

    /**
     * @param  array{state: string, channel_code: string, application_id: string, status: string, submitted_at: string}  $parameters
     */
    private static function signature(array $parameters, string $sharedSecret): string
    {
        return hash('sha256', implode('&', [
            'state='.trim($parameters['state']),
            'channel_code='.trim($parameters['channel_code']),
            'application_id='.trim($parameters['application_id']),
            'status='.trim($parameters['status']),
            'submitted_at='.trim($parameters['submitted_at']),
            'secret='.trim($sharedSecret),
        ]));
    }

    /**
     * @param  array<string, string>  $parameters
     */
    private static function mergeQuery(string $existingQuery, array $parameters): string
    {
        $reservedKeys = array_fill_keys(array_keys($parameters), true);
        $keptParts = [];

        foreach (explode('&', $existingQuery) as $part) {
            if ($part === '') {
                continue;
            }

            $key = rawurldecode(explode('=', $part, 2)[0]);
            if (! isset($reservedKeys[$key])) {
                $keptParts[] = $part;
            }
        }

        $keptParts[] = http_build_query($parameters, '', '&', PHP_QUERY_RFC3986);

        return implode('&', $keptParts);
    }

    /**
     * @param  array<string, mixed>  $parts
     */
    private static function assembleUrl(array $parts): string
    {
        $authority = '';
        if (isset($parts['user'])) {
            $authority .= $parts['user'];
            if (isset($parts['pass'])) {
                $authority .= ':'.$parts['pass'];
            }
            $authority .= '@';
        }
        $authority .= $parts['host'];
        if (isset($parts['port'])) {
            $authority .= ':'.$parts['port'];
        }

        return $parts['scheme'].'://'.$authority.($parts['path'] ?? '');
    }
}