//  _____         _  _____
// |_   _|____  _| ||_   _|_   __
//   | |/ _ \ \/ / __|| | \ \ / /
//   | |  __/>  <| |_ | |  \ V /
//   |_|\___/_/\_\\__||_|   \_/
// Author: Love Billenius <lovebillenius@disroot.org>
// License: GPL-3

#include "Page.hpp"

#include <iostream>

#include "stringutil.hpp"
#include "cpr/cpr.h"
#include "libxml/HTMLparser.h"
#include "libxml/xpath.h"


Page::Page(const uint_fast8_t number): number(number), subpages(fetchSubpages()) {
}

Page Page::operator--(int) const {
    return Page(number - 1);
}

Page Page::operator++(int) const {
    return Page(number + 1);
}

Page &Page::operator-=(int) {
    number--;
    refresh();
    return *this;
}

std::string Page::str() const {
    std::string ret;

    for (const std::string &pageText: subpages) {
        std::istringstream stream(pageText);
        std::string line;
        while (std::getline(stream, line))
            ret += line + "\n";

        string_utils::removeTabs(ret);
        string_utils::limitConsecutiveWhitespace(ret, MAX_WHITESPACE);
        string_utils::removeTrailingWhitespace(ret);
    }
    return ret;
}

Page &Page::operator+=(int) {
    number++;
    refresh();
    return *this;
}

bool Page::refresh() {
    std::vector<std::string> newSubpages = fetchSubpages();
    const bool replace = !contentEquals(newSubpages);
    if (replace)
        subpages = newSubpages;

    return replace;
}

std::string Page::url() const {
    return std::format("https://www.svt.se/svttext/web/pages/{}.html", number);
}

std::vector<std::string> Page::fetchSubpages() const {
    const cpr::Response response = cpr::Get(cpr::Url{url()});
    if (response.status_code / 100 != 2)
        throw std::runtime_error("Page not found");
    const htmlDocPtr doc = htmlReadMemory(response.text.c_str(), response.text.size(), nullptr, nullptr,
                                          HTML_PARSE_RECOVER | HTML_PARSE_NOERROR | HTML_PARSE_NOWARNING);
    if (doc == nullptr)
        throw std::runtime_error("Could not parse HTML.");

    const auto xpathCtx = xmlXPathNewContext(doc);
    if (!xpathCtx) {
        xmlFreeDoc(doc);
        throw std::runtime_error("Could not create XPath context.");
    }
    const auto xpathObj = xmlXPathEvalExpression(
        reinterpret_cast<const xmlChar *>("//div[contains(@class,'Content_screenreaderOnly')]"), xpathCtx);

    if (!xpathObj) {
        xmlXPathFreeContext(xpathCtx);
        xmlFreeDoc(doc);
        throw std::runtime_error("Could not evaluate XPath expression.");
    }

    std::vector<std::string> pages;
    if (const xmlNodeSetPtr nodes = xpathObj->nodesetval) {
        for (int i = 0; i < nodes->nodeNr; ++i) {
            xmlChar *content = xmlNodeGetContent(nodes->nodeTab[i]);
            if (!content)
                continue;
            pages.emplace_back(reinterpret_cast<const char *>(content));
            xmlFree(content);
        }
    }

    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    xmlFreeDoc(doc);

    return pages;
}

bool Page::contentEquals(const std::vector<std::string> &subpagesOther) const {
    if (subpagesOther.size() != subpages.size())
        return false;

    for (std::size_t i = 0; i < subpages.size(); i++)
        if (subpages[i] != subpagesOther[i])
            return false;

    return true;
}