httpsclient.h

/************************************************************************************
 *
 * D++, A Lightweight C++ library for Discord
 *
 * SPDX-License-Identifier: Apache-2.0
 * Copyright 2021 Craig Edwards and D++ contributors 
 * (https://github.com/brainboxdotcc/DPP/graphs/contributors)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 ************************************************************************************/
#pragma once
#include <dpp/export.h>
#include <string>
#include <map>
#include <list>
#include <vector>
#include <variant>
#include <dpp/sslconnection.h>
#include <dpp/version.h>
#include <dpp/stringops.h>

namespace dpp {

static inline const std::string http_version = "DiscordBot (https://github.com/brainboxdotcc/DPP, "
	+ to_hex(DPP_VERSION_MAJOR, false) + "." + to_hex(DPP_VERSION_MINOR, false) + "." + to_hex(DPP_VERSION_PATCH, false) + ")";

static inline constexpr const char* DISCORD_HOST = "https://discord.com";

/**
 * @brief HTTP connection status
 */
enum http_state : uint8_t {
	/**
	 * @brief Sending/receiving HTTP headers and request body
	 */
	HTTPS_HEADERS,

	/**
	 * @brief Receiving body content.
	 */
	HTTPS_CONTENT,

	/**
	 * @brief Completed connection, as it was closed or the body is >= Content-Length
	 * 
	 */
	HTTPS_DONE,

	/**
	 * @brief Received chunk length
	 * 
	 */
	HTTPS_CHUNK_LEN,

	/**
	 * @brief Received chunk trailing CRLF
	 */
	HTTPS_CHUNK_TRAILER,

	/**
	 * @brief The last received chunk is the final chunk
	 */
	HTTPS_CHUNK_LAST,

	/**
	 * @brief Receiving contents of a chunk
	 */
	HTTPS_CHUNK_CONTENT
};

/**
 * @brief Request headers
 */
typedef std::multimap<std::string, std::string> http_headers;

/**
 * @brief Represents a multipart mime body and the correct top-level mime type
 * If a non-multipart request is passed in, this is represented as a plain body
 * and the application/json mime type.
 */
struct multipart_content {
	/**
	 * @brief Multipart body
	 */
	std::string body;

	/**
	 * @brief MIME type
	 */
	std::string mimetype;
};

/**
 * @brief Represents a HTTP scheme, hostname and port
 * split into parts for easy use in https_client.
 */
struct http_connect_info {
	/**
	 * @brief True if the connection should be SSL
	 */
	bool is_ssl{};

	/**
	 * @brief The request scheme, e.g. 'https' or 'http'
	 */
	std::string scheme;

	/**
	 * @brief The request hostname part, e.g. 'discord.com'
	 */
	std::string hostname;

	/**
	 * @brief The port number, either determined from the scheme,
	 * or from the part of the hostname after a colon ":" character
	 */
	uint16_t port{};
};

using https_client_completion_event = std::function<void(class https_client*)>;

/**
 * @brief Implements a HTTPS socket client based on the SSL client.
 * @note plaintext HTTP without SSL is also supported via a "downgrade" setting
 */
class DPP_EXPORT https_client : public ssl_connection {

	/**
	 * @brief The type of the request, e.g. GET, POST
	 */
	std::string request_type;

	/**
	 * @brief Path part of URL for HTTPS connection
	 */
	std::string path;

	/**
	 * @brief The request body, e.g. form data
	 */
	std::string request_body;

	/**
	 * @brief The response body, e.g. file content or JSON
	 */
	std::string body;

	/**
	 * @brief The reported length of the content. If this is
	 * UULONG_MAX, then no length was reported by the server.
	 */
	uint64_t content_length;

	/**
	 * @brief Headers for the request, e.g. Authorization, etc.
	 */
	http_headers request_headers;

	/**
	 * @brief The status of the HTTP request from the server,
	 * e.g. 200 for OK, 404 for not found. A value of 0 means
	 * no request has been completed.
	 */
	uint16_t status;

	/**
	 * @brief The HTTP protocol to use
	 */
	std::string http_protocol;

	/**
	 * @brief Time at which the request should be abandoned
	 */
	time_t timeout;

	/**
	 * @brief If true the content is chunked encoding
	 */
	bool chunked;

	/**
	 * @brief Size of current chunk
	 */
	size_t chunk_size;

	/**
	 * @brief Number of bytes received in current chunk
	 */
	size_t chunk_receive;

	/**
	 * @brief Headers from the server's response, e.g. RateLimit
	 * headers, cookies, etc.
	 */
	std::multimap<std::string, std::string> response_headers;

protected:
	/**
	 * @brief Start the connection
	 */
	virtual void connect() override;

	/**
	 * @brief Get request state
	 * @return request state
	 */
	http_state get_state();

public:
	/**
	 * @brief If true the response timed out while waiting
	 */
	bool timed_out;

	/**
	 * @brief Function to call when HTTP request is completed
	 */
	https_client_completion_event completed;

	/**
	 * @brief Current connection state
	 */
	http_state state;

	/**
	 * @brief Connect to a specific HTTP(S) server and complete a request.
	 * 
	 * The constructor will attempt the connection, and return the content.
	 * By the time the constructor completes, the HTTP request will be stored
	 * in the object.
	 * 
	 * @note This is a blocking call. It starts a loop which runs non-blocking
	 * functions within it, but does not return until the request completes.
	 * See queues.cpp for how to make this asynchronous.
	 * 
	 * @param hostname Hostname to connect to
	 * @param port Port number to connect to, usually 443 for SSL and 80 for plaintext
	 * @param urlpath path part of URL, e.g. "/api"
	 * @param verb Request verb, e.g. GET or POST
	 * @param req_body Request body, use dpp::https_client::build_multipart() to build a multipart MIME body (e.g. for multiple file upload)
	 * @param extra_headers Additional request headers, e.g. user-agent, authorization, etc
	 * @param plaintext_connection Set to true to make the connection plaintext (turns off SSL)
	 * @param request_timeout How many seconds before the connection is considered failed if not finished
	 * @param protocol Request HTTP protocol (default: 1.1)
	 * @param done Function to call when https_client request is completed
	 */
        https_client(cluster* creator, const std::string &hostname, uint16_t port = 443, const std::string &urlpath = "/", const std::string &verb = "GET", const std::string &req_body = "", const http_headers& extra_headers = {}, bool plaintext_connection = false, uint16_t request_timeout = 5, const std::string &protocol = "1.1", https_client_completion_event done = {});

	/**
	 * @brief Destroy the https client object
	 */
        virtual ~https_client() override;

	/**
	 * @brief Build a multipart content from a set of files and some json
	 * 
	 * @param json The json content
	 * @param filenames File names of files to send
	 * @param contents Contents of each of the files to send
	 * @param mimetypes MIME types of each of the files to send
	 * @return multipart mime content and headers
	 */
	static multipart_content build_multipart(const std::string &json, const std::vector<std::string>& filenames = {}, const std::vector<std::string>& contents = {}, const std::vector<std::string>& mimetypes = {});

	/**
	 * @brief Processes incoming data from the SSL socket input buffer.
	 * 
	 * @param buffer The buffer contents. Can modify this value removing the head elements when processed.
	 */
        virtual bool handle_buffer(std::string &buffer) override;

	/**
	 * @brief Close HTTPS socket
	 */
        virtual void close() override;

	/**
	 * @brief Fires every second from the underlying socket I/O loop, used for timeouts
	 */
	virtual void one_second_timer() override;

	/**
	 * @brief Get a HTTP response header
	 * 
	 * @param header_name Header name to find, case insensitive
	 * @return Header content or empty string if not found.
	 * If multiple values have the same header_name, this will return one of them.
	 * @see get_header_count to determine if multiple are present
	 * @see get_header_list to retrieve all entries of the same header_name
	 */
	const std::string get_header(std::string header_name) const;

	/**
	 * @brief Get the number of headers with the same header name
	 *
	 * @param header_name
	 * @return the number of headers with this count
	 */
	size_t get_header_count(std::string header_name) const;


	/**
	 * @brief Get a set of HTTP response headers with a common name
	 *
	 * @param header_name
	 * @return A list of headers with the same name, or an empty list if not found
	 */
	const std::list<std::string> get_header_list(std::string header_name) const;

	/**
	 * @brief Get all HTTP response headers
	 * 
	 * @return headers as a map
	 */
	const std::multimap<std::string, std::string> get_headers() const;
 
	/**
	 * @brief Get the response content
	 * 
	 * @return response content
	 */
	const std::string get_content() const;

	/**
	 * @brief Get the response HTTP status, e.g.
	 * 200 for OK, 404 for not found, 429 for rate limited.
	 * A value of 0 indicates the request was not completed.
	 * 
	 * @return uint16_t HTTP status
	 */
	uint16_t get_status() const;

	/**
	 * @brief Break down a scheme, hostname and port into
	 * a http_connect_info.
	 * 
	 * All but the hostname portion are optional. The path component
	 * should not be passed to this function.
	 * 
	 * @param url URL to break down
	 * @return Split URL
	 */
	static http_connect_info get_host_info(std::string url);
};

}