HTTP_Message.h

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// Modified from CSE422 FS09
// Modified from CSE422 FS12
// Modified again for CSE422 FS20

#ifndef _HTTP_MESSAGE_H_
#define _HTTP_MESSAGE_H_

#include <map>
#include <string>
#include <vector>

namespace {
    // The exact string of characters used to represent HTTP line endings.
    const std::string line_ending = "\r\n";

    // The character used to separate the name of a header from its value.
    const char header_delimiter = ':';
}


/**
 * Structure used to associate header names and values, whenever necessary.
 */
struct HTTP_Header_Field {
    std::string name;
    std::string value;
};

/**
 * Base class for HTTP requests and responses.  Defines the
 * methods for accessing the various headers on a request/response.  Also
 * defines some internal things that are shared by the request/response classes.
 */
class HTTP_Message {
    private:
        std::map<std::string, std::string> headers;

    protected:
        HTTP_Message();

        bool parse_fields(const char* data, unsigned length);

        virtual void print(std::string& output_string) const;
        virtual void print(char* output_buffer, unsigned buffer_length) const;

        virtual void copy_if_room(char*& output_buffer, const char* data_string,
            unsigned& remaining_length) const;

        const char* find_next_line(const char* data, unsigned length) const;

    public:
        virtual ~HTTP_Message();

        /**
         * Indicates how many headers this message has.
         *
         * @return the number of headers stored in the message
         */
        unsigned get_num_header_fields() const;

        /**
         * Copies all of the message's headers into the given vector.  Use this
         * if you need to iterate through the headers.  If you know the name of
         * the header you want, get_header_value() is far more useful.
         *
         * @param[out] out_set Will be set to a collection of
         *      HTTP_Header_Fields representing all of the headers stored in
         *      the message.
         */
        void get_header_set(std::vector<HTTP_Header_Field>& out_set) const;

        /**
         * Retrieves the value of the header with the given name.
         * 
         * @param[in] name The name of the header to look up.
         * @param[out] out_value Will be set to that header's value, if it is
         *      found. If no header with that name is found, value will be
         *      undefined.
         * @return True if the requested header was found in the message (in
         *      which case, out_value is valid); false if it was not found.
         */
        bool get_header_value(const std::string& name,
            std::string& out_value) const;

        /**
         * Removes the corresponding header field from the request, if it exists.
         *
         * @param name The name of the field to remove
         */
        void remove_header_field(const std::string& name);

        /**
         * Updates the message to have the given header field.  Overwrites the
         * old value of the specified header if the message already had it.
         *
         * @param field The name/value of the header to set.
         */
        void set_header_field(const HTTP_Header_Field& field);

        /**
         * Updates the given header field in the message. If the header is not
         * already present, it will be added to the message.  If the header
         * *is* already present, its previous value will be overwritten.
         *
         * @param name The name of the header to set.
         * @param value The new value to set.
         */
        void set_header_field(const std::string& name,
            const std::string& value);
};

#endif //ndef _HTTP_MESSAGE_H_