#include "kappa/install/install.hpp"
#include "kappa/paths.hpp"

#include <algorithm>
#include <cstdint>
#include <filesystem>
#include <format>
#include <fstream>
#include <sstream>

namespace kappa::install {

namespace fs = std::filesystem;

std::string compute_config_hash(
    const std::unordered_map<std::string, dsl::FeatureDef>& features,
    const std::unordered_map<std::string, std::string>& config) {
    // Serialize features (sorted by key): "key1=enabled/flag|key2=..."
    std::vector<std::pair<std::string_view, const dsl::FeatureDef*>> feat_sorted;
    for (auto& [k, v] : features) feat_sorted.emplace_back(k, &v);
    std::sort(feat_sorted.begin(), feat_sorted.end());
    std::string serialized;
    for (auto& [k, f] : feat_sorted) {
        if (!serialized.empty()) serialized += '|';
        serialized += k;
        serialized += '=';
        if (f->force) serialized += "force:";
        serialized += f->enabled ? "1:" : "0:";
        serialized += f->flag;
    }
    serialized += '\n';
    // Serialize config (sorted by key): "key1=val1|key2=val2"
    std::vector<std::pair<std::string_view, std::string_view>> cfg_sorted;
    for (auto& [k, v] : config) cfg_sorted.emplace_back(k, v);
    std::sort(cfg_sorted.begin(), cfg_sorted.end());
    for (auto& [k, v] : cfg_sorted) {
        serialized += k;
        serialized += '=';
        serialized += v;
        serialized += '|';
    }
    // FNV-1a 64-bit hash
    std::uint64_t h = 14695981039346656037ULL;
    for (char c : serialized) {
        h ^= static_cast<std::uint64_t>(static_cast<unsigned char>(c));
        h *= 1099511628211ULL;
    }
    return std::format("{:016x}", h);
}

static std::string db_file() {
    return (fs::path(paths::db_dir()) / "installed").string();
}

static std::uint64_t fnv1a(std::string_view s) {
    std::uint64_t h = 14695981039346656037ULL;
    for (char c : s) { h ^= static_cast<std::uint64_t>(static_cast<unsigned char>(c)); h *= 1099511628211ULL; }
    return h;
}

InstallResult install(const resolve::BuildStep& step,
                      const fs::path& work_dir) {
    InstallResult result;

    auto hash = std::format("{:016x}",
        fnv1a(step.name + "\0" + step.resolved.original.version));
    result.hash = hash;

    auto dest = fs::path(paths::bin_dir()) / hash;
    result.store_path = dest;

    std::error_code ec;
    fs::create_directories(dest, ec);
    if (ec) {
        result.error = "cannot create store directory";
        return result;
    }

    auto src = work_dir / "destdir";
    if (fs::exists(src)) {
        for (auto& entry : fs::recursive_directory_iterator(src, ec)) {
            if (ec) { break; }
            auto rel = fs::relative(entry.path(), src);
            auto target = dest / rel;
            if (entry.is_directory()) {
                fs::create_directories(target, ec);
            } else {
                fs::create_directories(target.parent_path(), ec);
                if (!ec) { fs::rename(entry.path(), target, ec); }
            }
            if (ec) { break; }
        }
    }

    auto entries = read_installed();
    std::string ch = "0000000000000000";
    if (!step.resolved.features.empty() || !step.resolved.config.empty()) {
        ch = compute_config_hash(step.resolved.features, step.resolved.config);
    }
    entries.push_back({step.name, step.resolved.original.version,
                       hash, ch, step.resolved.original.provides});
    if (!write_installed(entries)) {
        result.error = "failed to write installed DB";
        return result;
    }

    std::vector<std::string> hashes;
    for (auto& e : entries) { hashes.push_back(e.hash); }
    record_generation(hashes, 5);

    result.ok = true;
    return result;
}

std::vector<DbEntry> read_installed() {
    std::vector<DbEntry> entries;
    std::ifstream in(db_file());
    if (!in) { return entries; }

    std::string line;
    while (std::getline(in, line)) {
        if (line.empty()) { continue; }
        std::istringstream iss(line);
        DbEntry e;
        iss >> e.name >> e.version >> e.hash;
        std::string token;
        auto pos = iss.tellg();
        if (iss >> token && token.size() == 16 
            && std::all_of(token.begin(), token.end(), [](char c) {
                return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f');
            })) {
            e.config_hash = token;
        } else {
            if (pos != std::streampos(-1)) {
                iss.clear();
                iss.seekg(pos);
            }
        }
        std::string prov;
        while (iss >> prov) { e.provides.push_back(prov); }
        entries.push_back(std::move(e));
    }
    return entries;
}

bool write_installed(const std::vector<DbEntry>& entries) {
    std::error_code ec;
    fs::create_directories(paths::db_dir(), ec);
    auto tmp = db_file() + ".tmp";
    {
        std::ofstream out(tmp);
        if (!out) return false;
        for (auto& e : entries) {
            out << e.name << ' ' << e.version << ' ' << e.hash;
            if (!e.config_hash.empty() && e.config_hash != "0000000000000000") {
                out << ' ' << e.config_hash;
            }
            for (auto& p : e.provides) { out << ' ' << p; }
            out << '\n';
        }
        out.close();
        if (out.fail()) {
            std::filesystem::remove(tmp, ec);
            return false;
        }
    }
    std::filesystem::rename(tmp, db_file(), ec);
    return !ec;
}

bool record_generation(const std::vector<std::string>& hashes, int keep) {
    auto gen_dir = fs::path(paths::db_dir()) / "generations";
    std::error_code ec;
    fs::create_directories(gen_dir, ec);

    int gen = 1;
    for (auto& entry : fs::directory_iterator(gen_dir, ec)) {
        auto name = entry.path().filename().string();
        if (name.starts_with("gen-")) { ++gen; }
    }

    auto gen_file = gen_dir / std::format("gen-{:04d}", gen);
    std::ofstream out(gen_file);
    if (!out) { return false; }
    for (auto& h : hashes) { out << h << '\n'; }

    std::vector<fs::path> gens;
    for (auto& entry : fs::directory_iterator(gen_dir, ec)) {
        gens.push_back(entry.path());
    }
    std::sort(gens.begin(), gens.end());

    while (static_cast<int>(gens.size()) > keep && keep > 0) {
        fs::remove_all(gens.front(), ec);
        gens.erase(gens.begin());
    }

    return true;
}

} // namespace kappa::install