/*  This file is part of remwharead.
 *  Copyright © 2019 tastytea <tastytea@tastytea.de>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <regex>
#include <algorithm>
#include <locale>
#include <unicode/unistr.h>
#include "search.hpp"

using std::regex;
using std::regex_search;
using std::smatch;
using std::find;
using std::find_if;

const vector<vector<string>> parse_expression(string expression)
{
    vector<vector<string>> searchlist;
    const regex re_or("(.+?) (OR|\\|\\|) ");
    const regex re_and("(.+?) (AND|&&) ");
    smatch match;

    vector<string> subexpressions;
    {                           // Split expression at OR.
        while (regex_search(expression, match, re_or))
        {
            subexpressions.push_back(match[1].str());
            expression = match.suffix().str();
        }
        subexpressions.push_back(expression);
    }

    {
        for (string sub : subexpressions)
        {                       // Split each OR-slice at AND.
            vector<string> terms;
            while (regex_search(sub, match, re_and))
            {
                terms.push_back(to_lowercase(match[1].str()));
                sub = match.suffix().str();
            }
            terms.push_back(to_lowercase(sub));
            searchlist.push_back(terms);
        }
    }

    return searchlist;
}

const string to_lowercase(const string &str)
{
    icu::UnicodeString uni(str.c_str());
    string out;
    uni.toLower().toUTF8String(out);
    return out;
}

const vector<Database::entry>
search_tags(const vector<Database::entry> &entries, string expression,
            const bool is_re)
{
    vector<vector<string>> searchlist = parse_expression(expression);
    vector<Database::entry> result;

    for (const vector<string> &tags_or : searchlist)
    {
        for (const Database::entry &entry : entries)
        {               // Add entry to result if all tags in an OR-slice match.
            bool matched = true;

            for (const string &tag : tags_or)
            {
                const auto it = find_if(entry.tags.begin(), entry.tags.end(),
                                        [&tag, is_re](string s)
                                        {
                                            s = to_lowercase(s);
                                            if (is_re)
                                            {
                                                const regex re("^" + tag + "$");
                                                return regex_search(s, re);
                                            }
                                            else
                                            {
                                                return (s == tag);
                                            }
                                        });
                if (it == entry.tags.end())
                {
                    matched = false;
                }
            }
            if (matched == true)
            {
                result.push_back(entry);
            }
        }
    }

    return result;
}

const vector<Database::entry>
search_all(const vector<Database::entry> &entries, string expression,
           const bool is_re)
{
    vector<vector<string>> searchlist = parse_expression(expression);
    vector<Database::entry> result = search_tags(entries, expression, is_re);

    for (const vector<string> &terms_or : searchlist)
    {
        for (const Database::entry &entry : entries)
        {
            // Add entry to result if all terms in an OR-slice match title,
            // description or full text.
            bool matched_title = true;
            bool matched_description = true;
            bool matched_fulltext = true;

            const auto it = find(result.begin(), result.end(), entry);
            if (it != result.end())
            {                   // Skip if already in result list.
                continue;
            }

            for (const string &term : terms_or)
            {
                const string title = to_lowercase(entry.title);
                const string description = to_lowercase(entry.description);
                const string fulltext = to_lowercase(entry.fulltext);

                // Set matched_* to false if term is not found.
                if (is_re)
                {
                    const regex re(term);

                    if(!regex_search(title, re))
                    {
                        matched_title = false;
                    }

                    if(!regex_search(description, re))
                    {
                        matched_description = false;
                    }

                    if(!regex_search(fulltext, re))
                    {
                        matched_fulltext = false;
                    }
                }
                else
                {
                    if (title.find(term) == string::npos)
                    {
                        matched_title = false;
                    }

                    if (description.find(term) == string::npos)
                    {
                        matched_description = false;
                    }

                    if (fulltext.find(term) == string::npos)
                    {
                        matched_fulltext = false;
                    }
                }
            }
            if (matched_title == true
                || matched_description == true
                || matched_fulltext == true)
            {
                result.push_back(entry);
            }
        }
    }

    return result;
}