<?php
namespace Aws\Api\Serializer;

use Aws\Api\MapShape;
use Aws\Api\Service;
use Aws\Api\Operation;
use Aws\Api\Shape;
use Aws\Api\StructureShape;
use Aws\Api\TimestampShape;
use Aws\CommandInterface;
use GuzzleHttp\Psr7;
use Psr\Http\Message\RequestInterface;

/**
 * Serializes HTTP locations like header, uri, payload, etc...
 * @internal
 */
abstract class RestSerializer
{
    /** @var Service */
    private $api;

    /** @var Psr7\Uri */
    private $endpoint;

    /**
     * @param Service $api      Service API description
     * @param string  $endpoint Endpoint to connect to
     */
    public function __construct(Service $api, $endpoint)
    {
        $this->api = $api;
        $this->endpoint = Psr7\uri_for($endpoint);
    }

    /**
     * @param CommandInterface $command Command to serialized
     *
     * @return RequestInterface
     */
    public function __invoke(CommandInterface $command)
    {
        $operation = $this->api->getOperation($command->getName());
        $args = $command->toArray();
        $opts = $this->serialize($operation, $args);
        $uri = $this->buildEndpoint($operation, $args, $opts);

        return new Psr7\Request(
            $operation['http']['method'],
            $uri,
            isset($opts['headers']) ? $opts['headers'] : [],
            isset($opts['body']) ? $opts['body'] : null
        );
    }

    /**
     * Modifies a hash of request options for a payload body.
     *
     * @param StructureShape   $member  Member to serialize
     * @param array            $value   Value to serialize
     * @param array            $opts    Request options to modify.
     */
    abstract protected function payload(
        StructureShape $member,
        array $value,
        array &$opts
    );

    private function serialize(Operation $operation, array $args)
    {
        $opts = [];
        $input = $operation->getInput();

        // Apply the payload trait if present
        if ($payload = $input['payload']) {
            $this->applyPayload($input, $payload, $args, $opts);
        }

        foreach ($args as $name => $value) {
            if ($input->hasMember($name)) {
                $member = $input->getMember($name);
                $location = $member['location'];
                if (!$payload && !$location) {
                    $bodyMembers[$name] = $value;
                } elseif ($location == 'header') {
                    $this->applyHeader($name, $member, $value, $opts);
                } elseif ($location == 'querystring') {
                    $this->applyQuery($name, $member, $value, $opts);
                } elseif ($location == 'headers') {
                    $this->applyHeaderMap($name, $member, $value, $opts);
                }
            }
        }

        if (isset($bodyMembers)) {
            $this->payload($operation->getInput(), $bodyMembers, $opts);
        }

        return $opts;
    }

    private function applyPayload(StructureShape $input, $name, array $args, array &$opts)
    {
        if (!isset($args[$name])) {
            return;
        }

        $m = $input->getMember($name);

        if ($m['streaming'] ||
           ($m['type'] == 'string' || $m['type'] == 'blob')
        ) {
            // Streaming bodies or payloads that are strings are
            // always just a stream of data.
            $opts['body'] = Psr7\stream_for($args[$name]);
            return;
        }

        $this->payload($m, $args[$name], $opts);
    }

    private function applyHeader($name, Shape $member, $value, array &$opts)
    {
        if ($member->getType() == 'timestamp') {
            $value = TimestampShape::format($value, 'rfc822');
        }

        $opts['headers'][$member['locationName'] ?: $name] = $value;
    }

    /**
     * Note: This is currently only present in the Amazon S3 model.
     */
    private function applyHeaderMap($name, Shape $member, array $value, array &$opts)
    {
        $prefix = $member['locationName'];
        foreach ($value as $k => $v) {
            $opts['headers'][$prefix . $k] = $v;
        }
    }

    private function applyQuery($name, Shape $member, $value, array &$opts)
    {
        if ($member instanceof MapShape) {
            $opts['query'] = isset($opts['query']) && is_array($opts['query'])
                ? $opts['query'] + $value
                : $value;
        } elseif ($value !== null) {
            $opts['query'][$member['locationName'] ?: $name] = $value;
        }
    }

    private function buildEndpoint(Operation $operation, array $args, array $opts)
    {
        $varspecs = [];

        // Create an associative array of varspecs used in expansions
        foreach ($operation->getInput()->getMembers() as $name => $member) {
            if ($member['location'] == 'uri') {
                $varspecs[$member['locationName'] ?: $name] =
                    isset($args[$name])
                        ? $args[$name]
                        : null;
            }
        }

        $relative = preg_replace_callback(
            '/\{([^\}]+)\}/',
            function (array $matches) use ($varspecs) {
                $isGreedy = substr($matches[1], -1, 1) == '+';
                $k = $isGreedy ? substr($matches[1], 0, -1) : $matches[1];
                if (!isset($varspecs[$k])) {
                    return '';
                } elseif ($isGreedy) {
                    return str_replace('%2F', '/', rawurlencode($varspecs[$k]));
                } else {
                    return rawurlencode($varspecs[$k]);
                }
            },
            $operation['http']['requestUri']
        );

        // Add the query string variables or appending to one if needed.
        if (!empty($opts['query'])) {
            $append = Psr7\build_query($opts['query']);
            $relative .= strpos($relative, '?') ? "&{$append}" : "?$append";
        }

        // Expand path place holders using Amazon's slightly different URI
        // template syntax.
        return Psr7\Uri::resolve($this->endpoint, $relative);
    }
}
