regex_utils.cpp

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/*
 * SNode.C - A Slim Toolkit for Network Communication
 * Copyright (C) Volker Christian <me@vchrist.at>
 *               2020, 2021, 2022, 2023, 2024, 2025
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
/*
 * MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
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 * The above copyright notice and this permission notice shall be included in
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#include "express/dispatcher/regex_utils.h"
 
#include "express/Request.h"
 
#ifndef DOXYGEN_SHOULD_SKIP_THIS
 
#include <cstddef>
 
#endif /* DOXYGEN_SHOULD_SKIP_THIS */
 
namespace express::dispatcher {
 
    std::vector<std::string> explode(const std::string& input, char delim) {
        std::vector<std::string> result;
        std::string current;
        int parenDepth = 0;
 
        for (const char ch : input) {
            if (ch == '(') {
                parenDepth++;
                current += ch;
            } else if (ch == ')') {
                parenDepth--;
                current += ch;
            } else if (ch == delim && parenDepth == 0) {
                result.push_back(current);
                current.clear();
            } else {
                current += ch;
            }
        }
 
        if (!current.empty()) {
            result.push_back(current);
        }
 
        return result;
    }
 
#define PATH_REGEX ":[a-zA-Z0-9]+(\\‍(.+\\‍))?"
    const std::regex& pathRegex() {
        static const std::regex pathregex(PATH_REGEX);
 
        return pathregex;
    }
 
    std::smatch matchResult(const std::string& cpath) {
        std::smatch smatch;
 
        std::regex_search(cpath, smatch, pathRegex());
 
        return smatch;
    }
 
    bool hasResult(const std::string& cpath) {
        std::smatch smatch;
 
        return std::regex_search(cpath, smatch, pathRegex());
    }
 
    void setParams(const std::string& cpath, Request& req) {
        std::vector<std::string> explodedString = explode(cpath, '/');
        std::vector<std::string> explodedReqString = explode(req.url, '/');
 
        for (std::vector<std::string>::size_type i = 0; i < explodedString.size() && i < explodedReqString.size(); i++) {
            if (!explodedString[i].empty() && explodedString[i].front() == ':') {
                const std::smatch smatch = matchResult(explodedString[i]);
                std::string regex = "(.*)";
 
                if (smatch.size() > 1) {
                    if (smatch[1] != "") {
                        regex = smatch[1];
                    }
                }
 
                if (std::regex_match(explodedReqString[i], std::regex(regex))) {
                    std::string attributeName = smatch[0];
                    attributeName.erase(0, 1);
                    attributeName.erase((attributeName.length() - static_cast<std::size_t>(smatch[1].length())),
                                        static_cast<std::size_t>(smatch[1].length()));
 
                    req.params[attributeName] = explodedReqString[i];
                }
            }
        }
    }
 
    std::unordered_map<std::string, std::string> parseQuery(std::string_view qs) {
        std::unordered_map<std::string, std::string> m;
        std::size_t i = 0;
        while (i < qs.size()) {
            const std::size_t amp = qs.find('&', i);
            const std::string_view pair = (amp == std::string_view::npos) ? qs.substr(i) : qs.substr(i, amp - i);
            const std::size_t eq = pair.find('=');
            std::string key;
            std::string val;
            if (eq == std::string_view::npos) {
                key.assign(pair);
            } else {
                key.assign(pair.substr(0, eq));
                val.assign(pair.substr(eq + 1));
            }
            if (!key.empty()) {
                m.emplace(std::move(key), std::move(val));
            }
            if (amp == std::string_view::npos) {
                break;
            }
            i = amp + 1;
        }
        return m;
    }
 
    std::pair<std::regex, std::vector<std::string>>
    compileParamRegex(std::string_view mountPath, bool isPrefix, bool strictRouting, bool caseInsensitive) {
        std::string pat;
        pat.reserve(mountPath.size() * 2);
        std::vector<std::string> names;
        pat += '^';
 
        const char* s = mountPath.data();
        const char* e = s + mountPath.size();
        while (s < e) {
            if (*s == ':') {
                ++s;
                const char* nstart = s;
                while (s < e && (std::isalnum(static_cast<unsigned char>(*s)) > 0 || *s == '_' || *s == '-')) {
                    ++s;
                }
                std::string name(nstart, s);
                std::string custom;
                if (s < e && *s == '(') {
                    int depth = 0;
                    const char* rstart = s + 1;
                    ++s;
                    while (s < e) {
                        if (*s == '(') {
                            ++depth;
                        } else if (*s == ')' && depth-- == 0) {
                            break;
                        }
                        ++s;
                    }
                    custom.assign(rstart, s);
                    if (s < e && *s == ')') {
                        ++s;
                    }
                }
                names.push_back(std::move(name));
                if (!custom.empty()) {
                    pat += '(';
                    pat += custom;
                    pat += ')';
                } else {
                    pat += "([^/]+)";
                } // default: single segment
            } else {
                static const std::string meta = R"(\.^$|()[]{}*+?!)";
                if (meta.find(*s) != std::string::npos) {
                    pat += '\\';
                }
                pat += *s;
                ++s;
            }
        }
 
        if (isPrefix) {
            pat += "(?:/|$)"; // boundary
        } else {
            if (!strictRouting) {
                pat += "/?"; // allow single trailing slash
            }
            pat += '$';
        }
 
        auto flags = std::regex::ECMAScript | (!caseInsensitive ? std::regex::flag_type{} : std::regex::icase);
 
        return {std::regex(pat, flags), std::move(names)};
    }
 
    bool querySupersetMatches(const std::unordered_map<std::string, std::string>& rq,
                              const std::unordered_map<std::string, std::string>& need) {
        for (const auto& kv : need) {
            auto it = rq.find(kv.first);
            if (it == rq.end() || it->second != kv.second) {
                return false;
            }
        }
        return true;
    }
 
    bool boundaryPrefix(std::string_view path, std::string_view base, bool caseInsensitive) {
        // Normalize: an empty base is equivalent to "/"
        if (base.empty()) {
            base = "/";
        }
 
        // Special case: base "/" matches any absolute path
        if (base.size() == 1 && base[0] == '/') {
            return !path.empty() && path.front() == '/';
        }
 
        // Base longer than path cannot match
        if (base.size() > path.size()) {
            return false;
        }
 
        auto eq = [&](char a, char b) {
            return !caseInsensitive ? (a == b)
                                    : (std::tolower(static_cast<unsigned char>(a)) == std::tolower(static_cast<unsigned char>(b)));
        };
 
        // Check prefix characters
        for (size_t i = 0; i < base.size(); ++i) {
            if (!eq(path[i], base[i])) {
                return false;
            }
        }
 
        // Boundary: either exact match, or next char is a '/'
        return (path.size() == base.size()) || (path[base.size()] == '/');
    }
 
    bool equalPath(std::string_view a, std::string_view b, bool caseInsensitive) {
        if (a.size() != b.size()) {
            return false;
        }
        for (size_t i = 0; i < a.size(); ++i) {
            if (!caseInsensitive ? (a[i] != b[i]) : !ieq(a[i], b[i])) {
                return false;
            }
        }
        return true;
    }
 
    std::string_view trimOneTrailingSlash(std::string_view s) {
        if (s.size() > 1 && s.back() == '/') {
            return std::string_view(s.data(), s.size() - 1);
        }
        return s;
    }
 
    void splitPathAndQuery(std::string_view url, std::string_view& path, std::string_view& query) {
        const std::size_t qpos = url.find('?');
        if (qpos == std::string_view::npos) {
            path = url;
            query = {};
        } else {
            path = url.substr(0, qpos);
            query = url.substr(qpos + 1);
        }
    }
 
} // namespace express::dispatcher