/*  This file is part of epubgrep.
 *  Copyright © 2021 tastytea <tastytea@tastytea.de>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, version 3.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "search.hpp"

#include "fs-compat.hpp"
#include "zip.hpp"

#include <boost/regex.hpp>

#include <algorithm>
#include <array>
#include <string>
#include <string_view>
#include <vector>

namespace epubgrep::search
{

using std::string;

std::vector<match> search(const fs::path &filepath,
                          const std::string_view regex, const settings &opts)
{
    boost::regex::flag_type flags{};

    switch (opts.regex)
    {
    case options::regex_kind::basic:
    {
        flags = opts.grep_like ? boost::regex::grep : boost::regex::basic;
        break;
    }
    case options::regex_kind::extended:
    {
        flags = opts.grep_like ? boost::regex::egrep : boost::regex::extended;
        break;
    }
    case options::regex_kind::perl:
    {
        flags = boost::regex::perl;
        break;
    }
    }

    if (opts.ignore_case)
    {
        flags |= boost::regex::icase;
    }

    const boost::regex re(regex.data(), flags);
    std::vector<match> matches;
    std::vector<string> epub_filepaths{[&opts, &filepath]
                                       {
                                           if (!opts.raw)
                                           {
                                               return zip::list_spine(filepath);
                                           }
                                           return zip::list(filepath);
                                       }()};

    for (const auto &entry : epub_filepaths)
    {
        auto document{zip::read_file(filepath, entry)};
        if (!opts.raw)
        {
            cleanup_text(document);
        }

        string::const_iterator begin{document.begin()};
        string::const_iterator end{document.end()};
        boost::match_results<string::const_iterator> match_result;
        string last_headline;
        string last_page;

        while (boost::regex_search(begin, end, match_result, re,
                                   boost::match_default))
        {
            match match; // FIXME: Rename variable or struct.
            match.epub_filepath = filepath;
            match.filepath = entry;
            match.text = match_result[0];
            match.context = context(match_result, opts.context);
            const auto current_headline{headline(match_result.prefix().str())};
            if (!current_headline.empty())
            {
                last_headline = current_headline;
            }
            match.headline = last_headline;
            const auto current_page{page(match_result.prefix().str())};
            if (!current_page.empty())
            {
                last_page = current_page;
            }
            match.page = last_page;

            matches.emplace_back(match);
            begin = match_result[0].second;
        }
    }

    return matches;
}

void cleanup_text(string &text)
{
    static const boost::regex re_header_start{"<[hH][1-6]"};
    static const boost::regex re_header_end{"</[hH][1-6]"};
    static const boost::regex re_pagebreak{".+pagebreak.+(title|aria-label)"
                                           "=\"([[:alnum:]]+)\".*"};

    size_t pos{};
    while ((pos = text.find('<', pos)) != string::npos)
    {
        // Mark headlines. We need them later on.
        string replacement;
        if (boost::regex_match(text.substr(pos, 3), re_header_start))
        {
            replacement = "<H>";
        }
        else if (boost::regex_match(text.substr(pos, 4), re_header_end))
        {
            replacement = "</H>";
        }
        else if (text.substr(pos, 6) == "<span ")
        {
            auto endpos{text.find('>')};
            boost::match_results<const char *> match;
            if (boost::regex_search(text.substr(pos, endpos).data(), match,
                                    re_pagebreak))
            {
                replacement = "<PAGE " + match[2] + ">";
            }
        }
        else if (text.substr(pos, 7) == "<style "
                 || text.substr(pos, 8) == "<script ")
        {
            pos = text.find('>', pos) + 1;
        }

        text.replace(pos, text.find('>', pos) + 1 - pos, replacement);
        pos += replacement.length();
    }

    pos = 0;
    while ((pos = text.find('\r', pos)) != string::npos)
    {
        text.erase(pos, 1);
    }

    pos = 0;
    while ((pos = text.find_first_of("\n\t", pos)) != string::npos)
    {
        text.replace(pos, 1, " ");
    }

    pos = 0;
    while ((pos = text.find("  ", pos)) != string::npos)
    {
        text.replace(pos, 2, " ");
    }
}

match_context context(const boost::match_results<string::const_iterator> &match,
                      std::uint64_t words)
{
    if (words == 0)
    {
        return {};
    }

    ++words;

    const auto &rbegin_before{std::reverse_iterator(match.prefix().end())};
    const auto &rend_before{std::reverse_iterator(match.prefix().begin())};

    const auto &begin_after{match.suffix().begin()};
    const auto &end_after{match.suffix().end()};

    auto pos_before{rbegin_before};
    auto pos_after{begin_after};

    const std::array<char, 4> whitespace{' ', '\n', '\r', '\t'};

    while (words != 0)
    {
        if (pos_before != rend_before)
        {
            pos_before = std::find_first_of(pos_before, rend_before,
                                            whitespace.begin(),
                                            whitespace.end());
            if (pos_before != rend_before)
            {
                while (is_whitespace(*pos_before))
                {
                    ++pos_before;
                }
            }
        }

        if (pos_after != end_after)
        {
            pos_after = std::find_first_of(pos_after, end_after,
                                           whitespace.begin(),
                                           whitespace.end());
            if (pos_after != end_after)
            {
                while (is_whitespace(*pos_after))
                {
                    ++pos_after;
                }
            }
        }
        words -= 1;
    }

    const std::string before_reversed(rbegin_before, pos_before);
    string before(before_reversed.rbegin(), before_reversed.rend());
    std::string after(begin_after, pos_after);
    while (is_whitespace(*before.begin()))
    {
        before.erase(0, 1);
    }
    while (is_whitespace(*after.rbegin()))
    {
        after.erase(after.size() - 1);
    }

    return {before, after};
}

string headline(const std::string_view prefix)
{
    size_t pos{prefix.length()};
    if ((pos = prefix.rfind("<H>", pos)) != std::string_view::npos)
    {
        pos += 3;
        string result{prefix.substr(pos, prefix.find('<', pos) - pos)};

        while (is_whitespace(*result.begin()))
        {
            result.erase(0, 1);
        }
        while (is_whitespace(*result.rbegin()))
        {
            result.erase(result.size() - 1);
        }

        return result;
    }

    return {};
}

string page(const std::string_view prefix)
{
    size_t pos{prefix.length()};
    while ((pos = prefix.rfind("<PAGE ", pos)) != std::string_view::npos)
    {
        pos += 6;
        return string{prefix.substr(pos, prefix.find('>', pos) - pos)};
    }

    return {};
}

bool is_whitespace(const char check)
{
    const std::array<char, 4> whitespace{' ', '\n', '\r', '\t'};
    return std::any_of(whitespace.begin(), whitespace.end(),
                       [&check](const char ws) { return check == ws; });
}

} // namespace epubgrep::search