// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// Four configurations:
//   Crafter.Debug.Core  what the app and the client share (values, codecs,
//                       the protocol, discovery, build info)
//   Crafter.Debug.Cli   the client's code, a library so tests can run it
//   crafter.debug-cli   the client, crafter-debug
//   Crafter.Debug       what an app links (returned), depending on the core
//                       and the client
// The client is one of the library's dependencies only so that a consumer's
// debug build compiles it in the same pass as the app; an executable adds no
// link flags to what depends on it. Consumers load this file through
// Debug::Use (tooling/), which also writes their launcher.
//
// The library and the client talk QUIC through Crafter.Network, which comes
// from forgejo, with --local from the checkout beside this one, or from the
// project.cpp $CRAFTER_DEBUG_NETWORK names (a Network worktree).
import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

namespace {
    // The configurations this file makes besides the one it returns, at
    // stable addresses for the pointers in `dependencies`. One set per load,
    // not statics: a static would keep the first load's args for every load.
    std::deque<Configuration> owned;

    // This file's directory. A configuration a project file makes for itself
    // keeps the path it is given, and "./" would later resolve against the
    // consumer's directory instead of this one.
    fs::path Root() {
        return fs::path(std::source_location::current().file_name()).parent_path();
    }

    // Crafter.Network, with the args unchanged: a consumer that also uses
    // it passes the same ones, so both resolve to one configuration rather
    // than one module built twice.
    Configuration* Network(std::span<const std::string_view> args) {
        const std::vector<std::string> forwarded(args.begin(), args.end());
        if (const char* local = std::getenv("CRAFTER_DEBUG_NETWORK"); local != nullptr && *local != '\0') {
            return LocalProject({ .projectFile = local, .args = forwarded });
        }
        if (std::ranges::find(args, std::string_view("--local")) != args.end()) {
            return LocalProject({ .projectFile = Root().parent_path() / "Crafter.Network" / "project.cpp", .args = forwarded });
        }
        return GitProject({
            .source = { .url = "https://forgejo.catcrafts.net/Catcrafts/Crafter.Network.git" },
            .args = forwarded,
        });
    }

    // Tests of the core, linked against it alone.
    constexpr std::array<std::string_view, 5> coreTests = {
        "ShouldRoundTripJson",
        "ShouldRoundTripAggregates",
        "ShouldReportDecodeErrorsWithPaths",
        "ShouldDescribeDefaultsAndRequired",
        "ShouldDiscoverLiveInstances",
    };

    // Tests of the app library.
    constexpr std::array<std::string_view, 7> libraryTests = {
        "ShouldInvokeCommands",
        "ShouldResolveWatchPaths",
        "ShouldRecordTimeline",
        "ShouldEvaluateConditions",
        "ShouldAnswerRequests",
        "ShouldPauseAndStep",
        "ShouldWaitTraceAndFollow",
    };

    std::string ReadFile(const fs::path& path) {
        std::ifstream in(path, std::ios::binary);
        return std::string((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
    }

    // FNV-1a over the path and bytes of every source, in a fixed order: what
    // the app and the client compare to tell they came from the same code.
    std::string SourceId() {
        std::vector<fs::path> files;
        for (const std::string_view dir : { "interfaces", "implementations" }) {
            std::error_code ec;
            for (const fs::directory_entry& entry : fs::recursive_directory_iterator(Root() / dir, ec)) {
                if (entry.is_regular_file() && (entry.path().extension() == ".cppm" || entry.path().extension() == ".cpp")) files.push_back(entry.path());
            }
        }
        std::ranges::sort(files);
        std::uint64_t hash = 14695981039346656037ULL;
        const auto mix = [&](std::string_view bytes) {
            for (const char c : bytes) {
                hash ^= static_cast<std::uint8_t>(c);
                hash *= 1099511628211ULL;
            }
        };
        for (const fs::path& file : files) {
            mix(file.lexically_relative(Root()).generic_string());
            mix(ReadFile(file));
        }
        return std::format("{:016x}", hash);
    }

    void WriteIfChanged(const fs::path& file, const std::string& text) {
        if (fs::exists(file) && ReadFile(file) == text) return;
        fs::create_directories(file.parent_path());
        std::ofstream(file, std::ios::binary | std::ios::trunc) << text;
    }

    // Generates the definitions of :BuildInfo for this variant of the core and
    // returns the source to compile, without its extension.
    fs::path GenerateBuildInfo(const Configuration& core, const Configuration& client) {
        const fs::path source = Root() / "build" / "generated" / core.VariantId() / "Crafter.Debug.Core-BuildInfo";
        const fs::path clientPath = client.BinDir() / client.outputName;
        WriteIfChanged(fs::path(source).concat(".cpp"), std::format(
            "// Generated by Crafter.Debug's project.cpp whenever the sources or the client's\n"
            "// path change. Not to be edited.\n"
            "module Crafter.Debug.Core:BuildInfo_impl;\n"
            "import std;\n"
            "import :BuildInfo;\n"
            "\n"
            "std::string_view Crafter::Debug::Detail::SourceId() {{\n"
            "    return \"{}\";\n"
            "}}\n"
            "\n"
            "std::string_view Crafter::Debug::Detail::ClientPath() {{\n"
            "    return R\"crafter-debug({})crafter-debug\";\n"
            "}}\n",
            SourceId(), clientPath.string()));
        return source;
    }
}

extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> args) {
    Configuration cfg;
    cfg.path = "./";
    cfg.name = "Crafter.Debug";
    cfg.outputName = "Crafter.Debug";
    cfg.type = ConfigurationType::LibraryStatic;
    ApplyStandardArgs(cfg, args);

    Configuration* network = Network(args);

    Configuration& core = owned.emplace_back();
    core.path = Root();
    core.name = "Crafter.Debug.Core";
    core.outputName = "Crafter.Debug.Core";
    core.type = ConfigurationType::LibraryStatic;
    ApplyStandardArgs(core, args);

    // The client, built for the library's target. Not through
    // ApplyStandardArgs: a consumer's --lib would make it a library.
    Configuration& client = owned.emplace_back();
    client.path = Root();
    client.name = "crafter.debug-cli";
    client.outputName = "crafter-debug";
    client.type = ConfigurationType::Executable;
    client.target = cfg.target;
    client.march = cfg.march;
    client.mtune = cfg.mtune;
    client.sysroot = cfg.sysroot;
    client.debug = cfg.debug;

    // The client's code as a library, so tests can run it in process.
    Configuration& cli = owned.emplace_back();
    cli.path = Root();
    cli.name = "Crafter.Debug.Cli";
    cli.outputName = "Crafter.Debug.Cli";
    cli.type = ConfigurationType::LibraryStatic;
    cli.target = cfg.target;
    cli.march = cfg.march;
    cli.mtune = cfg.mtune;
    cli.sysroot = cfg.sysroot;
    cli.debug = cfg.debug;
    cli.dependencies = { &core, network };
    client.dependencies = { &cli };

    {
        std::array<fs::path, 8> interfaces = {
            "interfaces/Crafter.Debug.Core-Value",
            "interfaces/Crafter.Debug.Core-Reflect",
            "interfaces/Crafter.Debug.Core-Codec",
            "interfaces/Crafter.Debug.Core-Result",
            "interfaces/Crafter.Debug.Core-Protocol",
            "interfaces/Crafter.Debug.Core-BuildInfo",
            "interfaces/Crafter.Debug.Core-Discovery",
            "interfaces/Crafter.Debug.Core",
        };
        std::array<fs::path, 5> implementations = {
            "implementations/Crafter.Debug.Core-Value",
            "implementations/Crafter.Debug.Core-Codec",
            "implementations/Crafter.Debug.Core-Protocol",
            "implementations/Crafter.Debug.Core-Discovery",
            GenerateBuildInfo(core, client),
        };
        core.GetInterfacesAndImplementations(interfaces, implementations);
    }
    {
        std::array<fs::path, 3> interfaces = { "interfaces/Crafter.Debug.Cli-Client", "interfaces/Crafter.Debug.Cli-Quic", "interfaces/Crafter.Debug.Cli" };
        std::array<fs::path, 2> implementations = { "implementations/Crafter.Debug.Cli-Client", "implementations/Crafter.Debug.Cli-Quic" };
        cli.GetInterfacesAndImplementations(interfaces, implementations);
    }
    {
        std::array<fs::path, 0> interfaces = {};
        std::array<fs::path, 1> implementations = { "implementations/main" };
        client.GetInterfacesAndImplementations(interfaces, implementations);
    }

    cfg.dependencies = { &core, &client, network };
    {
        std::array<fs::path, 6> interfaces = {
            "interfaces/Crafter.Debug-Registry",
            "interfaces/Crafter.Debug-Timeline",
            "interfaces/Crafter.Debug-Condition",
            "interfaces/Crafter.Debug-Session",
            "interfaces/Crafter.Debug-Transport",
            "interfaces/Crafter.Debug",
        };
        std::array<fs::path, 5> implementations = {
            "implementations/Crafter.Debug-Registry",
            "implementations/Crafter.Debug-Timeline",
            "implementations/Crafter.Debug-Condition",
            "implementations/Crafter.Debug-Session",
            "implementations/Crafter.Debug-Transport",
        };
        cfg.GetInterfacesAndImplementations(interfaces, implementations);
    }

    // Tests only when this is the project being built: a consumer's load of
    // this file has no use for them.
    if (IsTopLevelProject()) {
        for (const std::string_view test : coreTests) cfg.AddTest(test).Dependencies({ &core });
        for (const std::string_view test : libraryTests) cfg.AddTest(test).Dependencies({ &cfg });
        cfg.AddTest("ShouldRunClientCommands").Dependencies({ &cfg, &cli });
    }
    return cfg;
}