/*
Crafter® Build
Copyright (C) 2026 Catcrafts®
Catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

module Crafter.Build:External_impl;
import std;
import :External;
import :Platform;
namespace fs = std::filesystem;
using namespace Crafter;

namespace {

std::string DeriveName(const GitSource& source) {
    std::string url = source.url;
    while (!url.empty() && (url.back() == '/' || url.back() == '\\')) url.pop_back();
    if (url.ends_with(".git")) url.resize(url.size() - 4);
    auto slash = url.find_last_of("/\\");
    return slash == std::string::npos ? url : url.substr(slash + 1);
}

std::string ShellQuote(std::string_view s) {
    std::string out = "'";
    for (char c : s) {
        if (c == '\'') out += "'\\''";
        else out += c;
    }
    out += "'";
    return out;
}

std::string JoinOptions(std::span<const std::string> options) {
    std::string out;
    for (const std::string& opt : options) {
        if (!out.empty()) out += ' ';
        out += ShellQuote(opt);
    }
    return out;
}

std::string FetchGit(const GitSource& source, const fs::path& cloneDir) {
    auto runGit = [](std::string_view cmd) -> std::optional<std::string> {
        CommandResult r = RunCommandChecked(cmd);
        if (r.exitCode != 0) return std::format("`{}` failed (exit {}): {}", cmd, r.exitCode, r.output);
        return std::nullopt;
    };

    if (fs::exists(cloneDir)) {
        CommandResult remote = RunCommandChecked(std::format("git -C {} remote get-url origin", ShellQuote(cloneDir.string())));
        std::string currentUrl = remote.output;
        while (!currentUrl.empty() && (currentUrl.back() == '\n' || currentUrl.back() == '\r')) currentUrl.pop_back();
        if (remote.exitCode != 0 || currentUrl != source.url) {
            fs::remove_all(cloneDir);
        } else if (!source.commit.empty()) {
            CommandResult head = RunCommandChecked(std::format("git -C {} rev-parse HEAD", ShellQuote(cloneDir.string())));
            std::string currentHead = head.output;
            while (!currentHead.empty() && (currentHead.back() == '\n' || currentHead.back() == '\r')) currentHead.pop_back();
            if (head.exitCode == 0 && currentHead != source.commit) {
                if (auto err = runGit(std::format("git -C {} fetch origin", ShellQuote(cloneDir.string())))) return *err;
                if (auto err = runGit(std::format("git -C {} checkout {}", ShellQuote(cloneDir.string()), ShellQuote(source.commit)))) return *err;
            }
            return "";
        } else {
            return "";
        }
    }

    fs::path tmpDir = cloneDir;
    tmpDir += ".tmp";
    if (fs::exists(tmpDir)) fs::remove_all(tmpDir);

    if (auto err = runGit(std::format("git clone --recursive {} {}", ShellQuote(source.url), ShellQuote(tmpDir.string())))) {
        if (fs::exists(tmpDir)) fs::remove_all(tmpDir);
        return *err;
    }
    if (!source.branch.empty()) {
        if (auto err = runGit(std::format("git -C {} switch {}", ShellQuote(tmpDir.string()), ShellQuote(source.branch)))) {
            fs::remove_all(tmpDir);
            return *err;
        }
    }
    if (!source.commit.empty()) {
        if (auto err = runGit(std::format("git -C {} checkout {}", ShellQuote(tmpDir.string()), ShellQuote(source.commit)))) {
            fs::remove_all(tmpDir);
            return *err;
        }
    }

    std::error_code ec;
    fs::rename(tmpDir, cloneDir, ec);
    if (ec) {
        fs::remove_all(tmpDir);
        return std::format("rename {} -> {} failed: {}", tmpDir.string(), cloneDir.string(), ec.message());
    }
    return "";
}

std::string BuildInjectedCMakeFlags(const fs::path& cmakeBuildDir) {
    std::string out;
    out += " -DCMAKE_C_COMPILER=clang";
    out += " -DCMAKE_CXX_COMPILER=clang++";
    #ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_linux_gnu
    out += " -DCMAKE_CXX_FLAGS=-stdlib=libc++";
    out += " -DCMAKE_EXE_LINKER_FLAGS=-stdlib=libc++";
    out += " -DCMAKE_SHARED_LINKER_FLAGS=-stdlib=libc++";
    #endif
    fs::path absBuildDir = fs::absolute(cmakeBuildDir);
    out += std::format(" -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY={}", ShellQuote(absBuildDir.string()));
    out += std::format(" -DCMAKE_LIBRARY_OUTPUT_DIRECTORY={}", ShellQuote(absBuildDir.string()));
    return out;
}

std::string ConfigureCMake(const fs::path& cloneDir, const fs::path& cmakeBuildDir, std::span<const std::string> options) {
    fs::path optionsFile = cmakeBuildDir / ".crafter-options";
    std::string optionsKey = JoinOptions(options);

    bool needsConfigure = !fs::exists(cmakeBuildDir / "CMakeCache.txt");
    if (!needsConfigure) {
        std::ifstream existing(optionsFile);
        if (!existing) {
            needsConfigure = true;
        } else {
            std::stringstream buf;
            buf << existing.rdbuf();
            if (buf.str() != optionsKey) needsConfigure = true;
        }
    }

    if (!needsConfigure) return "";

    if (!fs::exists(cmakeBuildDir)) fs::create_directories(cmakeBuildDir);

    std::string cmd = std::format("cmake -S {} -B {}{}",
        ShellQuote(fs::absolute(cloneDir).string()),
        ShellQuote(fs::absolute(cmakeBuildDir).string()),
        BuildInjectedCMakeFlags(cmakeBuildDir));
    if (!options.empty()) {
        cmd += " ";
        cmd += optionsKey;
    }

    CommandResult r = RunCommandChecked(cmd);
    if (r.exitCode != 0) {
        return std::format("cmake configure failed (exit {}): {}", r.exitCode, r.output);
    }

    std::ofstream(optionsFile) << optionsKey;
    return "";
}

std::string BuildCMake(const fs::path& cmakeBuildDir) {
    std::string cmd = std::format("cmake --build {}", ShellQuote(fs::absolute(cmakeBuildDir).string()));
    CommandResult r = RunCommandChecked(cmd);
    if (r.exitCode != 0) {
        return std::format("cmake --build failed (exit {}): {}", r.exitCode, r.output);
    }
    return "";
}

}  // namespace

ExternalBuildResult Crafter::BuildExternal(
        const ExternalDependency& dep,
        std::atomic<bool>& cancelled) {
    ExternalBuildResult result;

    if (cancelled.load(std::memory_order_relaxed)) return result;

    std::string name = dep.name.empty() ? DeriveName(dep.source) : dep.name;
    if (name.empty()) {
        result.error = std::format("Could not derive name for external dependency from URL '{}'", dep.source.url);
        return result;
    }

    fs::path externalRoot = GetCacheDir() / "external";
    if (!fs::exists(externalRoot)) {
        std::error_code ec;
        fs::create_directories(externalRoot, ec);
        if (ec) {
            result.error = std::format("Failed to create {}: {}", externalRoot.string(), ec.message());
            return result;
        }
    }

    std::string keyMaterial = std::format("{}|{}|{}|{}",
        dep.source.url, dep.source.branch, dep.source.commit, JoinOptions(dep.options));
    std::size_t key = std::hash<std::string>{}(keyMaterial);
    fs::path cloneDir = externalRoot / std::format("{}-{:016x}", name, key);

    std::string fetchErr = FetchGit(dep.source, cloneDir);
    if (!fetchErr.empty()) {
        result.error = std::format("git fetch for '{}': {}", name, fetchErr);
        return result;
    }

    if (cancelled.load(std::memory_order_relaxed)) return result;

    fs::path cmakeBuildDir;
    if (dep.builder == ExternalBuilder::CMake) {
        cmakeBuildDir = cloneDir / "build";
        if (std::string err = ConfigureCMake(cloneDir, cmakeBuildDir, dep.options); !err.empty()) {
            result.error = std::format("cmake configure for '{}': {}", name, err);
            return result;
        }
        if (cancelled.load(std::memory_order_relaxed)) return result;
        if (std::string err = BuildCMake(cmakeBuildDir); !err.empty()) {
            result.error = std::format("cmake build for '{}': {}", name, err);
            return result;
        }
    }

    for (const fs::path& include : dep.includeDirs) {
        fs::path full = include.empty() ? cloneDir : cloneDir / include;
        result.compileFlags.push_back(std::format("-I{}", fs::absolute(full).string()));
    }

    if (dep.builder == ExternalBuilder::CMake) {
        result.linkFlags.push_back(std::format("-L{}", fs::absolute(cmakeBuildDir).string()));
        for (const std::string& lib : dep.libs) {
            result.linkFlags.push_back(std::format("-l{}", lib));
        }

        if (fs::exists(cmakeBuildDir)) {
            for (const auto& entry : fs::directory_iterator(cmakeBuildDir)) {
                if (!entry.is_regular_file()) continue;
                const fs::path& p = entry.path();
                if (p.extension() != ".a" && p.extension() != ".so") continue;
                std::error_code ec;
                fs::file_time_type t = entry.last_write_time(ec);
                if (!ec && t > result.latestArtifact) result.latestArtifact = t;
            }
        }
    }

    return result;
}