#include <memory>
#include <exception>
#include <stdexcept>
#include <FastHash.h>
#include <curl/curl.h>

#include "config.h"
#include "servehelper.h"
#include "routes/routes.h"

class CurlUrlException : public std::exception {
public:
    CurlUrlException(CURLUcode code_) : code(code_) {}

    const char* what() const noexcept {
        return curl_url_strerror(this->code);
    }

    CURLUcode code;
};


void serve(const httplib::Request& req, httplib::Response& res, std::string title, Element element, Nodes extra_head) {
    using namespace std::string_literals;

    std::string css_url = get_origin(req) + "/style.css";
    res.set_header("Content-Security-Policy", "default-src 'none'; img-src https:; media-src: https:; style-src "s + css_url);

    Element head("head", {
        Element("meta", {{"charset", "utf-8"}}, {}),
        Element("title", {std::move(title)}),
        Element("link", {{"rel", "stylesheet"}, {"href", std::move(css_url) + "?v=" + std::to_string(css_hash)}}, {}),
        Element("meta", {{"name", "viewport"}, {"content", "width=device-width,initial-scale=1"}}, {})
    });
    head.nodes.reserve(head.nodes.size() + extra_head.size());
    head.nodes.insert(head.nodes.end(), extra_head.begin(), extra_head.end());
    std::string html = "<!DOCTYPE html>"s + Element("html", {
        std::move(head),
        std::move(element)
    }).serialize();

    uint64_t hash = FastHash(html.data(), html.size(), 0);
    res.set_header("ETag", std::string(1, '"') + std::to_string(hash) + '"');

    if (should_send_304(req, hash)) {
        res.status = 304;
        res.set_header("Content-Length", std::to_string(html.size()));
        res.set_header("Content-Type", "text/html");
    } else {
        res.set_content(std::move(html), "text/html");
    }
}

void serve_error(const httplib::Request& req, httplib::Response& res,
        std::string title, std::optional<std::string> subtitle, std::optional<std::string> info) {

    Element error_div("div", {{"class", "error"}}, {
        Element("h2", {title})
    });
    if (subtitle) {
        error_div.nodes.push_back(Element("p", {
            std::move(*subtitle)
        }));
    }
    if (info) {
        error_div.nodes.push_back(Element("pre", {
            Element("code", {std::move(*info)})
        }));
    }

    Element body("body", {std::move(error_div)});
    serve(req, res, std::move(title), std::move(body));
}

void serve_redirect(const httplib::Request& req, httplib::Response& res, std::string url, bool permanent) {
    using namespace std::string_literals;

    Element body("body", {
        "Redirecting to ",
        Element("a", {{"href", url}}, {url}),
        "…"
    });
    res.set_redirect(url, permanent ? 301 : 302);
    serve(req, res, "Redirecting to "s + std::move(url) + "…", std::move(body));
}


std::string get_origin(const httplib::Request& req) {
    if (req.has_header("X-Canonical-Origin")) {
        return req.get_header_value("X-Canonical-Origin");
    }
    if (config.canonical_origin) {
        return *config.canonical_origin;
    }

    std::string origin = "http://";
    if (req.has_header("Host")) {
        origin += req.get_header_value("Host");
    } else {
        origin += config.bind_host;
        if (config.bind_port != 80) {
            origin += ':' + std::to_string(config.bind_port);
        }
    }
    return origin;
}

std::string proxy_mastodon_url(const httplib::Request& req, const std::string& url_str) {
    using CurlStr = std::unique_ptr<char, decltype(&curl_free)>;

    std::unique_ptr<CURLU, decltype(&curl_url_cleanup)> url(curl_url(), curl_url_cleanup);
    if (!url) {
        throw std::bad_alloc();
    }

    CURLUcode code = curl_url_set(url.get(), CURLUPART_URL, url_str.c_str(), 0);
    if (code) {
        throw CurlUrlException(code);
    }

    auto get_part = [&](CURLUPart part) {
        char* content;
        CURLUcode code = curl_url_get(url.get(), part, &content, 0);
        if (code) {
            throw CurlUrlException(code);
        }
        return CurlStr(content, curl_free);
    };
    CurlStr host = get_part(CURLUPART_HOST);
    CurlStr path = get_part(CURLUPART_PATH);
    CurlStr query = get_part(CURLUPART_QUERY);
    CurlStr fragment = get_part(CURLUPART_FRAGMENT);

    std::string new_url = get_origin(req) + '/' + host.get() + path.get();
    if (query) {
        new_url += '?';
        new_url += query.get();
    }
    if (fragment) {
        new_url += '#';
        new_url += fragment.get();
    }
    return new_url;
}

bool should_send_304(const httplib::Request& req, uint64_t hash) {
    std::string header = req.get_header_value("If-None-Match");
    if (header == "*") {
        return true;
    }

    size_t pos = header.find(std::string(1, '"') + std::to_string(hash) + '"');
    return pos != std::string::npos && (pos == 0 || header[pos - 1] != '/');
}