libcruft-util/cruft/util/uri.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2015, 2017, 2021 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "debug/assert.hpp"
#include "view.hpp"

#include <fmt/core.h>

#include <array>
#include <iosfwd>
#include <map>
#include <stdexcept>
#include <string>
#include <string_view>


namespace cruft {
    // parsing of rfc3986 uniform resource identifiers
    //
    // does not currently perform normalisation (scheme or protocol),
    // comparison, or other associated operations. though these should be
    // added in the future.
    //
    // note that the parsed results may not always conform to expectations
    // for some protocols. eg, mailto identifiers are complex to parse
    // reliably and would require a specialised parser to be reliable.
    //
    // not all fields will be present for all protocols (or all instances of
    // any given protocol). eg, the "tel" is unlikely to have port numbers.
    class uri {
    public:
        explicit uri (std::string &&);

        uri (uri &&) noexcept = default;
        uri& operator= (uri &&) noexcept = default;

        uri (uri const&) = default;
        uri& operator= (uri const&) = default;

        explicit uri (const std::string&);
        explicit uri (const char *);
        explicit uri (view<const char *>);

        uri (
            std::string_view scheme,
            std::string_view authority,
            std::string_view path,
            std::string_view query,
            std::string_view fragment
        );


        class parse_error : public std::runtime_error
        { using runtime_error::runtime_error; };


        // URI:     'https://user:password@example.com:80/path/to?foo=bar#fragment'
        //
        // SCHEME:          'https'
        // HIERARCHICAL:    'user:password@example.com:80/path/to'
        // AUTHORITY:       'user:password@example.com:80'
        // USER:            'user:password'
        // HOST:            'example.com'
        // PORT:            '80'
        // PATH:            '/path/to'
        // QUERY:           'foo=bar'
        // FRAGMENT:        'fragment'
        enum component {
            /* 0 */ SCHEME,
            /* 1 */ USER,
            /* 2 */ HOST,
            /* 3 */ PORT,
            /* 4 */ PATH,
            /* 5 */ QUERY,
            /* 6 */ FRAGMENT,

            NUM_COMPONENTS
        };

        std::string_view
        get (component c) const&;

        std::string_view all (void) const& { return m_value; }
        std::string const& value (void) const& { return m_value; }

        std::string_view scheme (void) const& { return get (SCHEME); }
        std::string_view user (void) const& { return get (USER); }
        std::string_view host (void) const& { return get (HOST); }
        std::string_view port (void) const& { return get (PORT); }
        std::string_view path (void) const& { return get (PATH); }
        std::string_view query (void) const& { return get (QUERY); }
        std::string_view fragment (void) const& { return get (FRAGMENT); }

        std::string_view heirarchical (void) const&; //{ return { user ().begin (), path ().end () }; }
        std::string_view authority (void) const&; //{ return { user ().begin (), port ().end () }; }

        /// Returns a view over the path and query components
        std::string_view
        pq (void) const&
        {
            return {
                m_value.data () + m_offsets[PATH].first,
                m_value.data () + m_offsets[QUERY].second
            };
        }

        /// Returns a view over the path, query, and fragment components
        std::string_view
        pqf (void) const& {
            return {
                m_value.data () + m_offsets[PATH].first,
                m_value.data () + m_offsets[FRAGMENT].second
            };
        }

        void set (component c, std::string_view val);

        // void clear (component);
        void clear_fragment (void);

        std::array<std::string_view, NUM_COMPONENTS>
        components (void) const& noexcept;

        static std::string percent_decode (view<const char*>);

    private:
        void parse (void);

        std::array<std::pair<int, int>, NUM_COMPONENTS> m_offsets;
        std::string m_value;
    };

    /// Break a query string into a sequence of key-value pairs.
    /// Duplicates are possible.
    /// vector is used to that order can be preserved
    /// The is the inverse of vector_to_query
    std::vector<std::pair<std::string, std::string>>
    query_to_vector (std::string_view);

    /// Convert a sequence of key-value pairs into a query string
    /// All pairs, including duplicates, are serialised in the provided order.
    /// This is the inverse of query_to_vector
    std::string
    vector_to_query (std::vector<std::pair<std::string, std::string>> const&);

    bool operator== (uri const&, uri const&) noexcept;

    cruft::uri resolve (cruft::uri const &base, cruft::uri const &child);
    cruft::uri normalise (cruft::uri const &);

    std::ostream& operator<< (std::ostream&, uri const&);
    std::ostream& operator<< (std::ostream&, uri::component);
}


// Don't use std::string_view here, fmtlib reimplements it as fmt::string_view.
template <>
struct fmt::formatter<cruft::uri> : public fmt::formatter<string_view> {
    format_context::iterator
    format (cruft::uri const&, format_context &ctx) const;
};


// Don't use std::string_view here, fmtlib reimplements it as fmt::string_view.
template <> struct fmt::formatter<cruft::uri::component>: formatter<string_view> {
    // parse is inherited from formatter<string_view>.
    fmt::format_context::iterator
    format(cruft::uri::component c, format_context& ctx) const;
};