module;

#include <toml.hpp>

module cargoxx.lockfile;

import std;
import cargoxx.util;

namespace cargoxx::lockfile {

auto Lockfile::nixpkgs_rev() const -> std::optional<std::string> {
    for (const auto& p : packages) {
        if (p.nixpkgs_rev && !p.nixpkgs_rev->empty()) {
            return p.nixpkgs_rev;
        }
    }
    return std::nullopt;
}

namespace {

using util::Error;
using util::ErrorCode;

auto err(ErrorCode code, std::string msg, std::filesystem::path path) -> Error {
    return Error{code, std::move(msg), "", std::move(path), std::nullopt};
}

auto extract_string_array(const toml::array& arr, std::string_view field,
                          const std::filesystem::path& path)
    -> util::Result<std::vector<std::string>> {
    std::vector<std::string> out;
    out.reserve(arr.size());
    for (const auto& el : arr) {
        if (auto s = el.value<std::string>()) {
            out.push_back(*s);
        } else {
            return std::unexpected(err(ErrorCode::ManifestInvalidField,
                                       std::format("'{}' must be an array of strings", field),
                                       path));
        }
    }
    return out;
}

auto parse_package(const toml::table& tbl, const std::filesystem::path& path)
    -> util::Result<LockfilePackage> {
    LockfilePackage pkg;

    if (auto v = tbl["name"].value<std::string>()) {
        pkg.name = *v;
    } else {
        return std::unexpected(
            err(ErrorCode::ManifestInvalidField, "lockfile package missing 'name'", path));
    }

    if (auto v = tbl["version"].value<std::string>()) {
        pkg.version = *v;
    } else {
        return std::unexpected(
            err(ErrorCode::ManifestInvalidField, "lockfile package missing 'version'", path));
    }

    if (const auto* deps = tbl["dependencies"].as_array()) {
        auto r = extract_string_array(*deps, "dependencies", path);
        if (!r) {
            return std::unexpected(r.error());
        }
        pkg.dependencies = std::move(*r);
    }

    if (auto v = tbl["nixpkgs_attr"].value<std::string>()) {
        pkg.nixpkgs_attr = *v;
    }
    if (auto v = tbl["nixpkgs_rev"].value<std::string>()) {
        pkg.nixpkgs_rev = *v;
    }
    if (auto v = tbl["linkdb_source"].value<std::string>()) {
        pkg.linkdb_source = *v;
    }

    return pkg;
}

} // namespace

auto parse(const std::filesystem::path& path) -> util::Result<Lockfile> {
    std::error_code ec;
    if (!std::filesystem::exists(path, ec) || ec) {
        return std::unexpected(err(ErrorCode::ManifestNotFound,
                                   std::format("lockfile not found: {}", path.string()), path));
    }

    toml::table root;
    try {
        root = toml::parse_file(path.string());
    } catch (const toml::parse_error& e) {
        return std::unexpected(err(ErrorCode::ManifestParseError,
                                   std::format("toml parse error: {}", e.description()), path));
    }

    Lockfile lock;
    if (auto v = root["version"].value<int>()) {
        lock.version = *v;
    }

    if (const auto* arr = root["package"].as_array()) {
        lock.packages.reserve(arr->size());
        for (const auto& el : *arr) {
            const auto* tbl = el.as_table();
            if (!tbl) {
                return std::unexpected(err(ErrorCode::ManifestInvalidField,
                                           "[[package]] entries must be tables", path));
            }
            auto p = parse_package(*tbl, path);
            if (!p) {
                return std::unexpected(p.error());
            }
            lock.packages.push_back(std::move(*p));
        }
    }

    return lock;
}

auto write(const Lockfile& lock, const std::filesystem::path& path) -> util::Result<void> {
    toml::table root;
    root.insert_or_assign("version", lock.version);

    toml::array packages;
    for (const auto& p : lock.packages) {
        toml::table tbl;
        tbl.insert_or_assign("name", p.name);
        tbl.insert_or_assign("version", p.version);
        if (!p.dependencies.empty()) {
            toml::array deps;
            for (const auto& d : p.dependencies) {
                deps.push_back(d);
            }
            tbl.insert_or_assign("dependencies", std::move(deps));
        }
        if (p.nixpkgs_attr) {
            tbl.insert_or_assign("nixpkgs_attr", *p.nixpkgs_attr);
        }
        if (p.nixpkgs_rev) {
            tbl.insert_or_assign("nixpkgs_rev", *p.nixpkgs_rev);
        }
        if (p.linkdb_source) {
            tbl.insert_or_assign("linkdb_source", *p.linkdb_source);
        }
        packages.push_back(std::move(tbl));
    }
    root.insert_or_assign("package", std::move(packages));

    std::ofstream out{path};
    if (!out) {
        return std::unexpected(util::Error{
            util::ErrorCode::Internal,
            std::format("cannot open lockfile for writing: {}", path.string()),
            "", path, std::nullopt,
        });
    }
    out << root << '\n';
    if (!out) {
        return std::unexpected(util::Error{
            util::ErrorCode::Internal,
            std::format("write failed: {}", path.string()),
            "", path, std::nullopt,
        });
    }
    return {};
}

} // namespace cargoxx::lockfile