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/*!
* @file cgiutil.h
* @brief Simple CGI/HTTP helper functions used by sternenblog.
*/
#include <stdbool.h>
/*!
* @brief Print a HTTP header
*
* Prints a HTTP Header to `stdout` like CGI requires.
*
* @param key Name of the HTTP Header
* @param val Contents of the header to send
*/
void send_header(char key[], char val[]);
/*!
* @brief Print end of HTTP header section
*
* Terminates the header section of a CGI/HTTP Response by printing `\r\n` to `stdout`.
*/
void terminate_headers(void);
/*!
* @brief Value of a HTTP status header for a given status code.
*
* Helper function that returns the status code plus its
* accompanying reason phrase as a string.
*
* The value is statically allocated so do not attempt
* to free it.
*
* Example usage:
*
* ```
* send_header("Status", http_status_line(404);
* // Prints: Status: 404 Not Found
* ```
*
* @param status HTTP status code
* @return status code and reason phrase as a string.
*/
char *http_status_line(int status);
/*!
* @brief Return HTTP error code for given errno
*
* Incomplete mapping of `errno`s to HTTP error codes.
* Defaults to 500.
*
* @param err POSIX errno
* @return HTTP error code
*/
int http_errno(int err);
/*!
* @brief Urlencode a given dynamically allocated string
*
* urlencode_realloc() receives a pointer to a pointer to
* a dynamically allocated string to encode plus its size
* including the null byte at the end.
*
* It then replaces every reserved character in the string
* except `/` with the appropriate percent encoding. If
* the size of the buffer is not enough, it uses `realloc()`
* to increase it.
*
* Note that the implementation of url encoding is not 100%
* correct, but should be good enough in the context of
* sternenblog. `/` is not encoded since on unix
* a slash should always a path delimiter and never part of
* a filename. Another limitation of the url encoding is
* that it only checks for a list of characters to encode
* instead of checking if the characters are unreserved
* and don't need to be encoded which would be more correct.
* The approach taken has the big advantage that we don't
* need to worry about UTF-8, which makes the implementation
* considerably simpler. As a consequence however it will
* be not aggressive enough in terms of encoding in some
* cases.
*
* On error -1 is returned. In such a case the original
* pointer remains intact, so you can either `free()` it
* or continue with the unencoded string.
*
* Otherwise it returns new size of the buffer.
*
* @param **input pointer to input string
* @param size size of input string including null byte
* @return -1 on error, else size of buffer
*/
int urlencode_realloc(char **input, int size);
/*!
* @brief Returns URL of server addressed by the current CGI request
*
* server_url() uses the CGI 1.1 environment variables `SERVER_NAME`
* and `SERVER_PORT` to construct an URL to the server the current
* request is addressed to. Since CGI only reveals the HTTP version
* used and not wether an encrypted version of HTTP is used,
* server_url() will use the parameter `https` to decide which protocol
* identifier to prefix.
*
* The returned `char *` is dynamically allocated and must be cleaned
* up using `free()` before it goes out of scope.
*
* @param https if true, prefix `https://` else `http://`
* @return Pointer to dynamically allocated char buffer containing the URL.
*/
char *server_url(bool https);
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