#include "kappa/fetch/recipe.hpp"

#include "kappa/dsl/parser.hpp"
#include "kappa/dsl/system.hpp"
#include "kappa/paths.hpp"

#include <sys/wait.h>
#include <unistd.h>
#include <filesystem>
#include <format>
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>

namespace kappa::fetch {

namespace {
int exec_curl(const std::string& output_path, const std::string& url) {
    pid_t pid = fork();
    if (pid == 0) {
        execlp("curl", "curl", "-Lsf", "-o", output_path.c_str(), url.c_str(), nullptr);
        _exit(127);
    }
    if (pid < 0) return -1;
    int status = 0;
    while (waitpid(pid, &status, 0) == -1 && errno == EINTR) {}
    return WIFEXITED(status) ? WEXITSTATUS(status) : -1;
}
} // namespace

RecipeResult fetch_recipe(const std::string& name,
                          const std::vector<std::string>& remotes) {
    RecipeResult result;

    // Check cached version first
    auto cache_path = paths::packages_dir() / (name + ".kap");
    std::string cached_version;
    if (std::filesystem::exists(cache_path)) {
        std::ifstream in(cache_path);
        if (in) {
            std::ostringstream buf;
            buf << in.rdbuf();
            try {
                auto pkg = dsl::parse(buf.str());
                cached_version = pkg.version;
            } catch (...) {
                // Corrupt cache — will re-download
            }
        }
    }

    // Try each remote
    std::string best_content;
    std::string best_version;
    std::string best_url;

    for (auto& remote : remotes) {
        auto url = remote;
        if (!url.empty() && url.back() != '/') url += '/';
        url += name + ".kap";

        // Download to temp
        auto temp_path = paths::temp_dir() / (name + ".kap.tmp");
        int rc = exec_curl(temp_path.string(), url);
        if (rc != 0) continue;

        // Parse downloaded file
        std::ifstream in(temp_path);
        if (!in) { std::filesystem::remove(temp_path); continue; }
        std::ostringstream buf;
        buf << in.rdbuf();
        in.close();

        std::string remote_version;
        try {
            auto pkg = dsl::parse(buf.str());
            remote_version = pkg.version;
        } catch (...) {
            std::filesystem::remove(temp_path);
            continue;
        }

        // Compare versions — keep the best (highest)
        // Simple string comparison for now; semver later
        if (remote_version > best_version) {
            best_version = remote_version;
            best_content = buf.str();
            best_url = url;
        }

        std::filesystem::remove(temp_path);
    }

    if (best_content.empty()) {
        if (!cached_version.empty()) {
            // No remote available but have cache
            result.ok = true;
            result.path = cache_path.string();
            result.version = cached_version;
            result.updated = false;
            return result;
        }
        result.error = "package '" + name + "' not found in any remote";
        return result;
    }

    // Update cache if remote is newer
    if (best_version > cached_version || cached_version.empty()) {
        std::error_code ec;
        std::filesystem::create_directories(paths::packages_dir(), ec);
        std::ofstream out(cache_path);
        if (!out) {
            result.error = "cannot write to cache";
            return result;
        }
        out << best_content;
        result.updated = true;
    }

    result.ok = true;
    result.path = cache_path.string();
    result.version = best_version;
    return result;
}

// ---------------------------------------------------------------------------
// Index-aware recipe fetching
// ---------------------------------------------------------------------------

static std::string sanitize_filename(const std::string& s) {
    std::string out = s;
    for (auto& c : out) {
        if (c == '/' || c == '\\' || c == ':') c = '_';
    }
    return out;
}

static int exec_curl_conditional(const std::string& output_path,
                                 const std::string& url,
                                 const std::string& time_cond_path) {
    std::vector<std::string> argv = {"curl", "-Lsf", "-o", output_path};
    if (!time_cond_path.empty()) {
        argv.push_back("-z");
        argv.push_back(time_cond_path);
    }
    argv.push_back(url);

    std::vector<std::vector<char>> argv_storage(argv.size());
    std::vector<char*> cargs;
    for (size_t i = 0; i < argv.size(); ++i) {
        argv_storage[i].assign(argv[i].begin(), argv[i].end());
        argv_storage[i].push_back('\0');
        cargs.push_back(argv_storage[i].data());
    }
    cargs.push_back(nullptr);

    pid_t pid = fork();
    if (pid == 0) {
        execvp(cargs[0], cargs.data());
        _exit(127);
    }
    if (pid < 0) return -1;
    int status = 0;
    while (waitpid(pid, &status, 0) == -1 && errno == EINTR) {}
    return WIFEXITED(status) ? WEXITSTATUS(status) : -1;
}

static std::optional<dsl::IndexDef> load_cached_index(
    const std::string& repo_name,
    const std::string& channel) {
    auto key = sanitize_filename(repo_name + "-" + channel) + ".kap";
    auto path = paths::cache_dir() / "indexes" / key;
    if (!std::filesystem::exists(path)) return std::nullopt;

    std::ifstream in(path);
    if (!in) return std::nullopt;
    std::ostringstream buf;
    buf << in.rdbuf();
    try {
        return dsl::parse_index(buf.str());
    } catch (...) {
        return std::nullopt;
    }
}

static bool download_index(const dsl::RepoDef& repo,
                           const std::string& channel,
                           const std::filesystem::path& cache_path) {
    auto url = repo.url;
    if (!url.empty() && url.back() != '/') url += '/';
    url += channel + "/index.kap";

    auto temp = cache_path.string() + ".tmp";

    // Try primary URL
    int rc = exec_curl_conditional(temp, url, cache_path.string());
    if (rc != 0) {
        // Try mirrors
        for (auto& mirror : repo.mirrors) {
            auto murl = mirror;
            if (!murl.empty() && murl.back() != '/') murl += '/';
            murl += channel + "/index.kap";
            rc = exec_curl_conditional(temp, murl, "");
            if (rc == 0) break;
        }
    }

    if (rc != 0) return false;

    // If curl returned 0 but the file might be empty (304 not modified),
    // move temp to cache only if it has content
    std::error_code ec;
    if (std::filesystem::file_size(temp, ec) > 0 || ec) {
        std::filesystem::rename(temp, cache_path, ec);
        return !ec;
    }

    // 304: no change, remove temp
    std::filesystem::remove(temp, ec);
    return true; // cache is still valid
}

static std::optional<std::string> download_recipe(
    const std::string& name,
    const dsl::RepoDef& repo,
    const std::string& channel) {
    auto remote_path = channel + "/" + name + ".kap";
    auto temp = paths::temp_dir() / (name + ".kap.tmp");

    // Build URL list: primary + mirrors
    std::vector<std::string> urls;
    auto url = repo.url;
    if (!url.empty() && url.back() != '/') url += '/';
    urls.push_back(url + remote_path);
    for (auto& mirror : repo.mirrors) {
        auto murl = mirror;
        if (!murl.empty() && murl.back() != '/') murl += '/';
        urls.push_back(murl + remote_path);
    }

    for (auto& u : urls) {
        int rc = exec_curl_conditional(temp.string(), u, "");
        if (rc == 0) {
            std::ifstream in(temp);
            if (!in) { std::filesystem::remove(temp); continue; }
            std::ostringstream buf;
            buf << in.rdbuf();
            in.close();
            std::filesystem::remove(temp);
            return buf.str();
        }
    }
    return std::nullopt;
}

RecipeResult fetch_recipe_from_repos(
    const std::string& name,
    const std::vector<dsl::RepoDef>& repos) {
    RecipeResult result;

    // Check cached version first
    auto cache_path = paths::packages_dir() / (name + ".kap");
    std::string cached_version;
    if (std::filesystem::exists(cache_path)) {
        std::ifstream in(cache_path);
        if (in) {
            std::ostringstream buf;
            buf << in.rdbuf();
            try {
                auto pkg = dsl::parse(buf.str());
                cached_version = pkg.version;
            } catch (...) {}
        }
    }

    // Ensure indexes cache directory exists
    std::error_code ec;
    std::filesystem::create_directories(paths::cache_dir() / "indexes", ec);

    // Sort repos by priority (descending)
    std::vector<const dsl::RepoDef*> sorted;
    for (auto& r : repos) sorted.push_back(&r);
    std::sort(sorted.begin(), sorted.end(),
              [](auto* a, auto* b) { return a->priority > b->priority; });

    std::string best_content;
    std::string best_version;

    for (auto* repo : sorted) {
        for (auto& channel : repo->channels) {
            // Check/update the index for this repo+channel
            auto idx_key = sanitize_filename(repo->name + "-" + channel);
            auto idx_cache = paths::cache_dir() / "indexes" / (idx_key + ".kap");

            // Download fresh index (conditional on cache)
            if (!download_index(*repo, channel, idx_cache)) continue;

            // Load and search the index
            auto idx = load_cached_index(repo->name, channel);
            if (!idx) continue;

            bool found = false;
            for (auto& entry : idx->packages) {
                if (entry.name != name) continue;
                found = true;
                break;
            }
            if (!found) continue;

            // Download the recipe
            auto content = download_recipe(name, *repo, channel);
            if (!content) continue;

            // Parse the downloaded recipe to get version
            std::string remote_version;
            try {
                auto pkg = dsl::parse(*content);
                remote_version = pkg.version;
            } catch (...) {
                continue;
            }

            if (remote_version > best_version) {
                best_version = remote_version;
                best_content = std::move(*content);
            }
        }
    }

    if (best_content.empty()) {
        if (!cached_version.empty()) {
            result.ok = true;
            result.path = cache_path.string();
            result.version = cached_version;
            return result;
        }
        result.error = "package '" + name + "' not found in any repo";
        return result;
    }

    // Update cache if remote is newer
    if (best_version > cached_version || cached_version.empty()) {
        std::ofstream out(cache_path);
        if (!out) {
            result.error = "cannot write to cache";
            return result;
        }
        out << best_content;
        result.updated = true;
    }

    result.ok = true;
    result.path = cache_path.string();
    result.version = best_version;
    return result;
}

} // namespace kappa::fetch