/*  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 "uri.hpp"
#include "version.hpp"
#include <boost/locale.hpp>
#include <Poco/Environment.h>
#include <Poco/Exception.h>
#include <Poco/Net/HTTPClientSession.h>
#include <Poco/Net/HTTPRequest.h>
#include <Poco/Net/HTTPResponse.h>
#include <Poco/Net/HTTPSClientSession.h>
#include <Poco/RegularExpression.h>
#include <Poco/StreamCopier.h>
#include <Poco/URI.h>
#include <codecvt>
#include <cstdint>
#include <exception>
#include <iostream>
#include <iterator>
#include <locale>
#include <sstream>
#include <utility>
#include <vector>

namespace remwharead
{
using std::array;
using std::istream;
using std::unique_ptr;
using std::make_unique;
using std::vector;
using std::cerr;
using std::endl;
using std::move;
using std::uint32_t;
using Poco::Net::HTTPClientSession;
using Poco::Net::HTTPSClientSession;
using Poco::Net::HTTPRequest;
using Poco::Net::HTTPResponse;
using Poco::Net::HTTPMessage;
using Poco::StreamCopier;
using Poco::Environment;
using RegEx = Poco::RegularExpression;

html_extract::operator bool()
{
    return successful;
}

archive_answer::operator bool()
{
    return successful;
}

URI::URI(string uri)
    : _uri(move(uri))
{
    Poco::Net::initializeSSL();

    set_proxy();
}

void URI::set_proxy()
{
    try
    {
        HTTPClientSession::ProxyConfig proxy;
        const string env_proxy = Environment::get("http_proxy");
        const RegEx re_proxy("^(?:https?://)?(?:([^:]+):?([^@]*)@)?" // user:pw
                             "([^:/]+)(?::([\\d]{1,5}))?/?$"); // host:port
        vector<string> matches;

        if (re_proxy.split(env_proxy, matches) < 4)
        {
            return;
        }

        proxy.username = matches[1];
        proxy.password = matches[2];
        proxy.host = matches[3];
        if (!matches[4].empty())
        {
            // NOLINTNEXTLINE(google-runtime-int) - Need to use same as stoul.
            const unsigned long port = std::stoul(matches[4]);
            if (port > 65535)
            {
                throw std::invalid_argument("Proxy port number out of range");
            }
            proxy.port = static_cast<uint16_t>(port);
        }
        HTTPClientSession::setGlobalProxyConfig(proxy);
    }
    catch (const Poco::RegularExpressionException &e)
    {
        cerr << "Error: Proxy could not be set (" << e.displayText() << ")\n";
    }
    catch (const std::invalid_argument &e)
    {
        cerr << "Error: " << e.what() << endl;
    }
    catch (const Poco::NotFoundException &)
    {
        // No proxy found, no problem.
    }
    catch (const std::exception &e)
    {
        cerr << "Unexpected exception: " << e.what() << endl;
    }
}

URI::~URI()
{
    Poco::Net::uninitializeSSL();
}

html_extract URI::get()
{
    try
    {
        _document = make_request(_uri);
        _document = to_utf8(_document);
        if (!_document.empty())
        {
            return
                {
                    true,
                    "",
                    extract_title(),
                    extract_description(),
                    strip_html()
                };
        }
    }
    catch (const Poco::Exception &e)
    {
        return { false, e.displayText(), "", "", "" };
    }

    return { false, "Unknown error.", "", "", "" };
}

string URI::make_request(const string &uri, bool archive) const
{
    Poco::URI poco_uri(uri);
    string method = archive ? HTTPRequest::HTTP_HEAD : HTTPRequest::HTTP_GET;
    string path = poco_uri.getPathAndQuery();
    if (path.empty())
    {
        path = "/";
    }

    unique_ptr<HTTPClientSession> session;
    if (poco_uri.getScheme() == "https")
    {
        session = make_unique<HTTPSClientSession>(poco_uri.getHost(),
                                                  poco_uri.getPort());
    }
    else if (poco_uri.getScheme() == "http")
    {
        session = make_unique<HTTPClientSession>(poco_uri.getHost(),
                                                 poco_uri.getPort());
    }
    else
    {
        // NOLINTNEXTLINE(cert-err60-cpp)
        throw Poco::Exception("Protocol not supported.");
    }

    HTTPRequest request(method, path, HTTPMessage::HTTP_1_1);
    request.set("User-Agent", string("remwharead/") + global::version);

    HTTPResponse response;

    session->sendRequest(request);
    istream &rs = session->receiveResponse(response);

    // Not using the constants because some are too new for Debian stretch.
    switch (response.getStatus())
    {
    case 301:                   // HTTPResponse::HTTP_MOVED_PERMANENTLY
    case 308:                   // HTTPResponse::HTTP_PERMANENT_REDIRECT
    case 302:                   // HTTPResponse::HTTP_FOUND
    case 303:                   // HTTPResponse::HTTP_SEE_OTHER
    case 307:                   // HTTPResponse::HTTP_TEMPORARY_REDIRECT
    {
        string location = response.get("Location");
        if (location.substr(0, 4) != "http")
        {
            location = poco_uri.getScheme() + "://" + poco_uri.getHost()
                + location;
        }
        return make_request(location, archive);
    }
    case HTTPResponse::HTTP_OK:
    {
        string answer;
        if (archive)
        {
            answer = response.get("Content-Location");
        }
        else
        {
            StreamCopier::copyToString(rs, answer);
        }
        return answer;
    }
    default:
    {
        throw Poco::Exception(response.getReason()); // NOLINT(cert-err60-cpp)
        return "";
    }
    }
}

string URI::extract_title() const
{
    if (is_html())
    {
        const RegEx re_title("<title(?: [^>]+)?>([^<]+)", RegEx::RE_CASELESS);
        vector<string> matches;
        re_title.split(_document, matches);
        if (matches.size() >= 2)
        {
            return remove_newlines(unescape_html(matches[1]));
        }
    }

    return "";
}

string URI::extract_description() const
{
    if (is_html())
    {
        const RegEx re_desc(R"(description"[^>]+content="([^"]+))",
                            RegEx::RE_CASELESS);
        vector<string> matches;
        re_desc.split(_document, matches);
        if (matches.size() >= 2)
        {
            return cut_text(remove_newlines(unescape_html(matches[1])), 500);
        }
    }

    return "";
}

string URI::strip_html() const
{
    string out;

    out = remove_html_tags(_document, "script"); // Remove JavaScript.
    out = remove_html_tags(out, "style");   // Remove CSS.
    out = remove_html_tags(out);            // Remove tags.

    size_t pos = 0;
    while ((pos = out.find('\r', pos)) != std::string::npos) // Remove CR.
    {
        out.replace(pos, 1, "");
    }

    // Remove whitespace at eol.
    RegEx("\\s+\n").subst(out, "\n", RegEx::RE_GLOBAL);
    RegEx("\n{2,}").subst(out, "\n", RegEx::RE_GLOBAL); // Reduce newlines.

    return unescape_html(out);
}

string URI::remove_html_tags(const string &html, const string &tag) const
{
    // NOTE: I did this with regex_replace before, but libstdc++ segfaulted.
    string out;
    if (tag.empty())
    {
        size_t pos = 0;
        while (pos != std::string::npos)
        {
            size_t startpos = html.find('<', pos);
            size_t endpos = html.find('>', startpos);
            out += html.substr(pos, startpos - pos);
            pos = endpos;
            if (pos != std::string::npos)
            {
                ++pos;
            }
        }
    }
    else
    {
        size_t pos = 0;
        out = html;
        while ((pos = out.find("<" + tag)) != std::string::npos)
        {
            size_t endpos = out.find("</" + tag, pos);
            if (endpos == std::string::npos)
            {
                break;
            }
            endpos += 3 + tag.length(); // tag + </ + >
            out.replace(pos, endpos - pos, "");
        }
    }

    return out;
}

string URI::unescape_html(string html) const
{
    // Used to convert int to utf-8 char.
    std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> u8c;
    const RegEx re_entity("&#(x)?([[:alnum:]]{1,8});");
    RegEx::MatchVec matches;
    string::size_type pos = 0;

    while (re_entity.match(html, pos, matches) != 0)
    {
        char32_t codepoint = 0;
        const string number = html.substr(matches[2].offset, matches[2].length);
        // 'x' in front of the number means it's hexadecimal, else decimal.
        if (matches[1].length != 0)
        {
            codepoint = static_cast<char32_t>(std::stoul(number, nullptr, 16));
        }
        else
        {
            codepoint = static_cast<char32_t>(std::stoi(number, nullptr, 10));
        }
        const string unicode = u8c.to_bytes(codepoint);
        html.replace(matches[0].offset, matches[0].length, unicode);
        pos = matches[0].offset + unicode.length();
    }

    // Source: https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_
    //         entity_references#Character_entity_references_in_HTML
    const array<const std::pair<const string, const char32_t>, 258> names =
        {{
                { "exclamation", 0x0021 },
                { "quot", 0x0022 },
                { "percent", 0x0025 },
                { "amp", 0x0026 },
                { "apos", 0x0027 },
                { "add", 0x002B },
                { "lt", 0x003C },
                { "equal", 0x003D },
                { "gt", 0x003E },
                { "nbsp", 0x00A0 },
                { "iexcl", 0x00A1 },
                { "cent", 0x00A2 },
                { "pound", 0x00A3 },
                { "curren", 0x00A4 },
                { "yen", 0x00A5 },
                { "brvbar", 0x00A6 },
                { "sect", 0x00A7 },
                { "uml", 0x00A8 },
                { "copy", 0x00A9 },
                { "ordf", 0x00AA },
                { "laquo", 0x00AB },
                { "not", 0x00AC },
                { "shy", 0x00AD },
                { "reg", 0x00AE },
                { "macr", 0x00AF },
                { "deg", 0x00B0 },
                { "plusmn", 0x00B1 },
                { "sup2", 0x00B2 },
                { "sup3", 0x00B3 },
                { "acute", 0x00B4 },
                { "micro", 0x00B5 },
                { "para", 0x00B6 },
                { "middot", 0x00B7 },
                { "cedil", 0x00B8 },
                { "sup1", 0x00B9 },
                { "ordm", 0x00BA },
                { "raquo", 0x00BB },
                { "frac14", 0x00BC },
                { "frac12", 0x00BD },
                { "frac34", 0x00BE },
                { "iquest", 0x00BF },
                { "Agrave", 0x00C0 },
                { "Aacute", 0x00C1 },
                { "Acirc", 0x00C2 },
                { "Atilde", 0x00C3 },
                { "Auml", 0x00C4 },
                { "Aring", 0x00C5 },
                { "AElig", 0x00C6 },
                { "Ccedil", 0x00C7 },
                { "Egrave", 0x00C8 },
                { "Eacute", 0x00C9 },
                { "Ecirc", 0x00CA },
                { "Euml", 0x00CB },
                { "Igrave", 0x00CC },
                { "Iacute", 0x00CD },
                { "Icirc", 0x00CE },
                { "Iuml", 0x00CF },
                { "ETH", 0x00D0 },
                { "Ntilde", 0x00D1 },
                { "Ograve", 0x00D2 },
                { "Oacute", 0x00D3 },
                { "Ocirc", 0x00D4 },
                { "Otilde", 0x00D5 },
                { "Ouml", 0x00D6 },
                { "times", 0x00D7 },
                { "Oslash", 0x00D8 },
                { "Ugrave", 0x00D9 },
                { "Uacute", 0x00DA },
                { "Ucirc", 0x00DB },
                { "Uuml", 0x00DC },
                { "Yacute", 0x00DD },
                { "THORN", 0x00DE },
                { "szlig", 0x00DF },
                { "agrave", 0x00E0 },
                { "aacute", 0x00E1 },
                { "acirc", 0x00E2 },
                { "atilde", 0x00E3 },
                { "auml", 0x00E4 },
                { "aring", 0x00E5 },
                { "aelig", 0x00E6 },
                { "ccedil", 0x00E7 },
                { "egrave", 0x00E8 },
                { "eacute", 0x00E9 },
                { "ecirc", 0x00EA },
                { "euml", 0x00EB },
                { "igrave", 0x00EC },
                { "iacute", 0x00ED },
                { "icirc", 0x00EE },
                { "iuml", 0x00EF },
                { "eth", 0x00F0 },
                { "ntilde", 0x00F1 },
                { "ograve", 0x00F2 },
                { "oacute", 0x00F3 },
                { "ocirc", 0x00F4 },
                { "otilde", 0x00F5 },
                { "ouml", 0x00F6 },
                { "divide", 0x00F7 },
                { "oslash", 0x00F8 },
                { "ugrave", 0x00F9 },
                { "uacute", 0x00FA },
                { "ucirc", 0x00FB },
                { "uuml", 0x00FC },
                { "yacute", 0x00FD },
                { "thorn", 0x00FE },
                { "yuml", 0x00FF },
                { "OElig", 0x0152 },
                { "oelig", 0x0153 },
                { "Scaron", 0x0160 },
                { "scaron", 0x0161 },
                { "Yuml", 0x0178 },
                { "fnof", 0x0192 },
                { "circ", 0x02C6 },
                { "tilde", 0x02DC },
                { "Alpha", 0x0391 },
                { "Beta", 0x0392 },
                { "Gamma", 0x0393 },
                { "Delta", 0x0394 },
                { "Epsilon", 0x0395 },
                { "Zeta", 0x0396 },
                { "Eta", 0x0397 },
                { "Theta", 0x0398 },
                { "Iota", 0x0399 },
                { "Kappa", 0x039A },
                { "Lambda", 0x039B },
                { "Mu", 0x039C },
                { "Nu", 0x039D },
                { "Xi", 0x039E },
                { "Omicron", 0x039F },
                { "Pi", 0x03A0 },
                { "Rho", 0x03A1 },
                { "Sigma", 0x03A3 },
                { "Tau", 0x03A4 },
                { "Upsilon", 0x03A5 },
                { "Phi", 0x03A6 },
                { "Chi", 0x03A7 },
                { "Psi", 0x03A8 },
                { "Omega", 0x03A9 },
                { "alpha", 0x03B1 },
                { "beta", 0x03B2 },
                { "gamma", 0x03B3 },
                { "delta", 0x03B4 },
                { "epsilon", 0x03B5 },
                { "zeta", 0x03B6 },
                { "eta", 0x03B7 },
                { "theta", 0x03B8 },
                { "iota", 0x03B9 },
                { "kappa", 0x03BA },
                { "lambda", 0x03BB },
                { "mu", 0x03BC },
                { "nu", 0x03BD },
                { "xi", 0x03BE },
                { "omicron", 0x03BF },
                { "pi", 0x03C0 },
                { "rho", 0x03C1 },
                { "sigmaf", 0x03C2 },
                { "sigma", 0x03C3 },
                { "tau", 0x03C4 },
                { "upsilon", 0x03C5 },
                { "phi", 0x03C6 },
                { "chi", 0x03C7 },
                { "psi", 0x03C8 },
                { "omega", 0x03C9 },
                { "thetasym", 0x03D1 },
                { "upsih", 0x03D2 },
                { "piv", 0x03D6 },
                { "ensp", 0x2002 },
                { "emsp", 0x2003 },
                { "thinsp", 0x2009 },
                { "zwnj", 0x200C },
                { "zwj", 0x200D },
                { "lrm", 0x200E },
                { "rlm", 0x200F },
                { "ndash", 0x2013 },
                { "mdash", 0x2014 },
                { "horbar", 0x2015 },
                { "lsquo", 0x2018 },
                { "rsquo", 0x2019 },
                { "sbquo", 0x201A },
                { "ldquo", 0x201C },
                { "rdquo", 0x201D },
                { "bdquo", 0x201E },
                { "dagger", 0x2020 },
                { "Dagger", 0x2021 },
                { "bull", 0x2022 },
                { "hellip", 0x2026 },
                { "permil", 0x2030 },
                { "prime", 0x2032 },
                { "Prime", 0x2033 },
                { "lsaquo", 0x2039 },
                { "rsaquo", 0x203A },
                { "oline", 0x203E },
                { "frasl", 0x2044 },
                { "euro", 0x20AC },
                { "image", 0x2111 },
                { "weierp", 0x2118 },
                { "real", 0x211C },
                { "trade", 0x2122 },
                { "alefsym", 0x2135 },
                { "larr", 0x2190 },
                { "uarr", 0x2191 },
                { "rarr", 0x2192 },
                { "darr", 0x2193 },
                { "harr", 0x2194 },
                { "crarr", 0x21B5 },
                { "lArr", 0x21D0 },
                { "uArr", 0x21D1 },
                { "rArr", 0x21D2 },
                { "dArr", 0x21D3 },
                { "hArr", 0x21D4 },
                { "forall", 0x2200 },
                { "part", 0x2202 },
                { "exist", 0x2203 },
                { "empty", 0x2205 },
                { "nabla", 0x2207 },
                { "isin", 0x2208 },
                { "notin", 0x2209 },
                { "ni", 0x220B },
                { "prod", 0x220F },
                { "sum", 0x2211 },
                { "minus", 0x2212 },
                { "lowast", 0x2217 },
                { "radic", 0x221A },
                { "prop", 0x221D },
                { "infin", 0x221E },
                { "ang", 0x2220 },
                { "and", 0x2227 },
                { "or", 0x2228 },
                { "cap", 0x2229 },
                { "cup", 0x222A },
                { "int", 0x222B },
                { "there4", 0x2234 },
                { "sim", 0x223C },
                { "cong", 0x2245 },
                { "asymp", 0x2248 },
                { "ne", 0x2260 },
                { "equiv", 0x2261 },
                { "le", 0x2264 },
                { "ge", 0x2265 },
                { "sub", 0x2282 },
                { "sup", 0x2283 },
                { "nsub", 0x2284 },
                { "sube", 0x2286 },
                { "supe", 0x2287 },
                { "oplus", 0x2295 },
                { "otimes", 0x2297 },
                { "perp", 0x22A5 },
                { "sdot", 0x22C5 },
                { "lceil", 0x2308 },
                { "rceil", 0x2309 },
                { "lfloor", 0x230A },
                { "rfloor", 0x230B },
                { "lang", 0x2329 },
                { "rang", 0x232A },
                { "loz", 0x25CA },
                { "spades", 0x2660 },
                { "clubs", 0x2663 },
                { "hearts", 0x2665 },
                { "diams", 0x2666 }
            }};

    for (auto &pair : names)
    {
        const RegEx re('&' + pair.first + ';');
        re.subst(html, u8c.to_bytes(pair.second), RegEx::RE_GLOBAL);
    }

    return html;
}

archive_answer URI::archive() const
{
    if (_uri.substr(0, 4) != "http")
    {
        return { false, "Only HTTP(S) is archivable.", "" };
    }

    try
    {
        const string answer = make_request("https://web.archive.org/save/"
                                           + _uri, true);

        if (!answer.empty())
        {
            return { true, "", "https://web.archive.org" + answer };
        }
    }
    catch (const Poco::Exception &e)
    {
        return { false, e.displayText(), "" };
    }

    return { false, "Unknown error.", "" };
}

string URI::remove_newlines(string text) const
{
    size_t posn = 0;
    while ((posn = text.find('\n', posn)) != std::string::npos)
    {
        text.replace(posn, 1, " ");

        size_t posr = posn - 1;
        if (text[posr] == '\r')
        {
            text.replace(posr, 1, " ");
        }
        ++posn;
    }

    return text;
}

string URI::cut_text(const string &text, const uint16_t n_chars) const
{
    if (text.size() > n_chars)
    {
        constexpr char suffix[] = " […]";
        constexpr auto suffix_len = std::end(suffix) - std::begin(suffix) - 1;
        if (n_chars <= suffix_len)
        {
            throw std::invalid_argument("n_chars has to be greater than "
                                        + std::to_string(suffix_len));
        }

        const size_t pos =
            text.rfind(' ', static_cast<size_t>(n_chars - suffix_len));

        return text.substr(0, pos) + suffix;
    }

    return text;
}

string URI::to_utf8(const string &str)
{
    if (_encoding.empty())
    {
        detect_encoding();
    }

    return boost::locale::conv::to_utf<char>(str, _encoding);
}

void URI::detect_encoding()
{
    const RegEx re_encoding(R"(<meta.+charset=(.+)[";])", RegEx::RE_CASELESS);
    vector<string> matches;
    re_encoding.split(_document, matches);
    if (matches.size() >= 2)
    {
        _encoding = matches[1];
    }
}

bool URI::is_html() const
{
    const RegEx re_htmlfile(".*\\.(.?html?|xml|rss)$", RegEx::RE_CASELESS);
    if (_uri.substr(0, 4) == "http" || re_htmlfile.match(_uri))
    {
        return true;
    }

    return false;
}

} // namespace remwharead