#include "services/textureCache.hpp"

#include <algorithm>
#include <chrono>
#include <cstdlib>
#include <curl/curl.h>
#include <filesystem>
#include <fstream>
#include <iomanip>
#include <sstream>
#include <vector>

#include "giomm/file.h"
#include "glibmm/bytes.h"

namespace {
#define CACHE_SIZE 128
#define CACHE_AGE 168

constexpr std::uint64_t kFnvOffsetBasis = 14695981039346656037ull;
constexpr std::uint64_t kFnvPrime = 1099511628211ull;

std::string to_hex(std::uint64_t value) {
    std::ostringstream stream;
    stream << std::hex << std::setw(16) << std::setfill('0') << value;
    return stream.str();
}

std::string hash_url(const std::string &url) {
    std::uint64_t hash = kFnvOffsetBasis;
    for (unsigned char c : url) {
        hash ^= c;
        hash *= kFnvPrime;
    }
    return to_hex(hash);
}

std::filesystem::path get_cache_dir() {
    const char *xdg_cache = std::getenv("XDG_CACHE_HOME");
    if (xdg_cache && *xdg_cache) {
        return std::filesystem::path(xdg_cache) / "bar";
    }

    const char *home = std::getenv("HOME");
    if (home && *home) {
        return std::filesystem::path(home) / ".cache" / "bar";
    }

    return std::filesystem::temp_directory_path() / "bar";
}

std::filesystem::path get_cache_path_for_url(const std::string &url) {
    auto filename = hash_url(url);

    auto last_slash = url.find_last_of('/');
    auto last_dot = url.find_last_of('.');
    if (last_dot != std::string::npos && (last_slash == std::string::npos || last_dot > last_slash)) {
        auto ext = url.substr(last_dot);
        if (ext.size() <= 10) {
            filename += ext;
        }
    }

    return get_cache_dir() / filename;
}

std::chrono::system_clock::time_point to_system_clock(std::filesystem::file_time_type time) {
    return std::chrono::time_point_cast<std::chrono::system_clock::duration>(
        time - std::filesystem::file_time_type::clock::now() + std::chrono::system_clock::now()
    );
}

size_t write_to_buffer(void *contents, size_t size, size_t nmemb, void *userp) {
    auto *buffer = static_cast<std::vector<unsigned char> *>(userp);
    auto total = size * nmemb;
    auto *bytes = static_cast<unsigned char *>(contents);
    buffer->insert(buffer->end(), bytes, bytes + total);
    return total;
}

Glib::RefPtr<Gdk::Texture> load_texture_from_file(const std::filesystem::path &path) {
    if (!std::filesystem::exists(path)) {
        return {};
    }

    auto file = Gio::File::create_for_path(path.string());
    try {
        return Gdk::Texture::create_from_file(file);
    } catch (...) {
        return {};
    }
}

Glib::RefPtr<Gdk::Texture> download_texture_from_url(const std::string &url, const std::filesystem::path &path) {
    if (url.empty()) {
        return {};
    }

    CURL *curl = curl_easy_init();
    if (!curl) {
        return {};
    }

    std::vector<unsigned char> buffer;
    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_to_buffer);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buffer);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "bar/1.0");

    auto res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);

    if (res != CURLE_OK || buffer.empty()) {
        return {};
    }

    std::error_code error;
    std::filesystem::create_directories(path.parent_path(), error);

    std::ofstream output(path, std::ios::binary | std::ios::trunc);
    if (output) {
        output.write(reinterpret_cast<const char *>(buffer.data()), static_cast<std::streamsize>(buffer.size()));
    }

    auto bytes = Glib::Bytes::create(buffer.data(), buffer.size());
    return Gdk::Texture::create_from_bytes(bytes);
}
} // namespace

TextureCacheService *TextureCacheService::getInstance() {
    static TextureCacheService instance;
    return &instance;
}

Glib::RefPtr<Gdk::Texture> TextureCacheService::getTexture(const std::string &url) {
    if (url.empty()) {
        return {};
    }

    auto it = cache.find(url);
    if (it != cache.end()) {
        return it->second;
    }

    auto cache_path = get_cache_path_for_url(url);
    auto texture = load_texture_from_file(cache_path);
    if (!texture) {
        texture = download_texture_from_url(url, cache_path);
    }

    if (texture) {
        cache.emplace(url, texture);
        std::error_code error;
        std::filesystem::last_write_time(cache_path, std::filesystem::file_time_type::clock::now(), error);
    }

    return texture;
}

void TextureCacheService::pruneCache() {
    std::error_code error;
    auto cache_dir = get_cache_dir();
    std::filesystem::create_directories(cache_dir, error);

    std::vector<std::pair<std::filesystem::path, std::uintmax_t>> files;
    std::uintmax_t total_size = 0;

    auto now = std::chrono::system_clock::now();
    auto max_age = std::chrono::hours(CACHE_AGE);

    for (const auto &entry : std::filesystem::directory_iterator(cache_dir, error)) {
        if (error || !entry.is_regular_file()) {
            continue;
        }

        auto path = entry.path();
        auto last_write = entry.last_write_time(error);
        if (!error) {
            auto age = now - to_system_clock(last_write);
            if (age > max_age) {
                std::filesystem::remove(path, error);
                continue;
            }
        }

        auto size = entry.file_size(error);
        if (!error) {
            total_size += size;
            files.emplace_back(path, size);
        }
    }

    auto max_size = static_cast<std::uintmax_t>(CACHE_SIZE) * 1024ull * 1024ull;
    if (total_size <= max_size) {
        return;
    }

    std::sort(files.begin(), files.end(), [&](const auto &left, const auto &right) {
        std::error_code left_error;
        std::error_code right_error;
        auto left_time = std::filesystem::last_write_time(left.first, left_error);
        auto right_time = std::filesystem::last_write_time(right.first, right_error);
        if (left_error || right_error) {
            return left.first.string() < right.first.string();
        }
        return left_time < right_time;
    });

    for (const auto &item : files) {
        if (total_size <= max_size) {
            break;
        }
        std::filesystem::remove(item.first, error);
        if (!error) {
            if (total_size >= item.second) {
                total_size -= item.second;
            } else {
                total_size = 0;
            }
        }
    }
}