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

import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

// Adding a data member to a class in a module interface must rebuild every
// object compiled against the old layout. The dangerous shape (issue #27) is a
// consumer whose sources were scanned *before* its `dependencies` were assigned:
// its `import <DepModule>;` matched nothing, so its object carried no staleness
// edge to the interface, and a layout change rebuilt the library, relinked the
// consumer, and produced a binary mixing both layouts with no error or warning.
//
// `AddTest` is exactly that shape — it scans tests/<name>/main.cpp and only then
// returns a builder whose .Dependencies() supplies the library — which is why
// the original report saw the corruption in test executables specifically.

namespace {
    std::int32_t Failures = 0;

    void Check(bool cond, std::string_view msg) {
        if (!cond) {
            std::println(std::cerr, "FAIL: {}", msg);
            ++Failures;
        }
    }

    // The fixture is mutated during the run, so work on a copy outside the repo.
    fs::path StageFixture() {
        fs::path source = fs::current_path() / "tests" / "IncrementalInterfaceChange" / "fixture";
        fs::path staged = fs::temp_directory_path() / "crafter-build-incremental-interface-change";
        fs::remove_all(staged);
        fs::copy(source, staged, fs::copy_options::recursive);
        return staged;
    }

    // Swap in the variant carrying the extra member. Comes from a file rather
    // than a string literal here: the module scanner reads raw source, so an
    // `export module Widget;` spelled inside this test would make the test look
    // like an implementation unit of Widget.
    void GrowWidget(const fs::path& staged) {
        fs::copy_file(staged / "lib" / "Widget-grown.cppm.in", staged / "lib" / "Widget.cppm", fs::copy_options::overwrite_existing);
        // copy_file carries the source's mtime across, which would leave the
        // rewritten interface looking older than the BMI built from it.
        fs::last_write_time(staged / "lib" / "Widget.cppm", fs::file_time_type::clock::now());
    }

    std::unique_ptr<Configuration> MakeLib(const fs::path& staged) {
        auto lib = std::make_unique<Configuration>();
        lib->path = staged / "lib";
        lib->name = "widget";
        lib->outputName = "widget";
        lib->target = HostTarget();
        lib->type = ConfigurationType::LibraryStatic;
        std::array<fs::path, 1> ifaces = { "Widget" };
        std::array<fs::path, 1> impls = { "Widget" };
        lib->GetInterfacesAndImplementations(ifaces, impls);
        return lib;
    }

    // Scan first, wire the dependency up afterwards — the ordering that used to
    // silently drop the staleness edge.
    Configuration MakeConsumerScannedBeforeDependencies(const fs::path& staged, Configuration* lib) {
        Configuration app;
        app.path = staged;
        app.name = "widget-app";
        app.outputName = "widget-app";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        std::array<fs::path, 0> ifaces = {};
        std::array<fs::path, 1> impls = { "main" };
        app.GetInterfacesAndImplementations(ifaces, impls);
        app.dependencies = { lib };
        return app;
    }

    bool BuildOk(Configuration& app, std::string_view label) {
        // A fresh depResults per pass: the map memoizes each Configuration's
        // build for the duration of one pass, so reusing it would skip the
        // library's second build entirely.
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        BuildResult r = Build(app, depResults, depMutex);
        if (!r.result.empty()) {
            std::println(std::cerr, "FAIL: {} build failed: {}", label, r.result);
            ++Failures;
            return false;
        }
        return true;
    }
}

int main() {
    {
        // The scan leaves the unmatched import recorded rather than forgotten,
        // and ResolvePendingImports places it once the library is reachable.
        fs::path staged = StageFixture();
        std::unique_ptr<Configuration> lib = MakeLib(staged);
        Configuration app;
        app.path = staged;
        app.name = "widget-app";
        app.outputName = "widget-app";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        std::array<fs::path, 0> ifaces = {};
        std::array<fs::path, 1> impls = { "main" };
        app.GetInterfacesAndImplementations(ifaces, impls);

        Check(app.implementations.size() == 1, "consumer has one implementation");
        if (app.implementations.size() == 1) {
            const Implementation& impl = app.implementations[0];
            Check(impl.externalModuleDependencies.empty(), "no external dep resolvable before dependencies are assigned");
            Check(std::ranges::find(impl.pendingImports, "Widget") != impl.pendingImports.end(), "unresolved 'import Widget;' is recorded as pending");

            app.dependencies = { lib.get() };
            app.ResolvePendingImports();

            Check(impl.externalModuleDependencies.size() == 1, "ResolvePendingImports adds the external module dep");
            if (impl.externalModuleDependencies.size() == 1) {
                Check(impl.externalModuleDependencies[0].first->name == "Widget", "external dep is the Widget module");
                Check(impl.externalModuleDependencies[0].second == lib->PcmDir() / "Widget.pcm", "external dep points at the library's BMI");
            }
            Check(std::ranges::find(impl.pendingImports, "Widget") == impl.pendingImports.end(), "resolved import is no longer pending");

            // Idempotent: a second sweep must not duplicate the edge (Build
            // runs one unconditionally, on top of whatever callers already did).
            app.ResolvePendingImports();
            Check(impl.externalModuleDependencies.size() == 1, "ResolvePendingImports is idempotent");
        }
    }

    {
        // AddTest is the reported path: it scans the test source, then hands
        // back a builder whose .Dependencies() names the library.
        fs::path staged = StageFixture();
        fs::create_directories(staged / "tests" / "Consumer");
        fs::copy_file(staged / "main.cpp", staged / "tests" / "Consumer" / "main.cpp");
        std::unique_ptr<Configuration> lib = MakeLib(staged);

        Configuration app;
        app.path = staged;
        app.name = "host";
        app.outputName = "host";
        app.target = HostTarget();
        app.type = ConfigurationType::Executable;
        // AddTest resolves tests/<name>/main against the cwd, which for a real
        // run is the directory holding project.cpp. Stand in the staged project
        // for the declaration so the fixture's test source is the one scanned.
        fs::path restore = fs::current_path();
        fs::current_path(staged);
        app.AddTest("Consumer").Dependencies({ lib.get() });
        fs::current_path(restore);

        Check(app.tests.size() == 1, "one test declared");
        if (app.tests.size() == 1 && app.tests[0].config.implementations.size() == 1) {
            const Implementation& impl = app.tests[0].config.implementations[0];
            Check(impl.externalModuleDependencies.size() == 1, "AddTest(...).Dependencies() resolves the test's import of the library module");
            Check(impl.pendingImports.empty() || std::ranges::find(impl.pendingImports, "Widget") == impl.pendingImports.end(), "test's 'import Widget;' is no longer pending");
        }
    }

    {
        // End to end, and deliberately without calling ResolvePendingImports:
        // the guarantee under test is that Build() closes the window on its own,
        // for consumers that never knew they had to ask.
        fs::path staged = StageFixture();
        std::unique_ptr<Configuration> lib = MakeLib(staged);
        Configuration app = MakeConsumerScannedBeforeDependencies(staged, lib.get());
        fs::path binary = app.BinDir() / "widget-app";
        fs::path consumerObject = app.BuildDir() / "main_impl.o";

        if (BuildOk(app, "first pass")) {
            auto first = RunCommandWithTimeout(binary.string(), std::chrono::seconds(30));
            Check(first.exitCode == 0 && !first.crashed && !first.timedOut, std::format("first pass agrees on the layout (exit={} output='{}')", first.exitCode, first.output));

            fs::file_time_type objectBefore = fs::last_write_time(consumerObject);

            // Same edit as the original report: one more member on a class in a
            // module interface. Every signature and mangled name is unchanged,
            // so a missed rebuild produces no diagnostic of any kind.
            GrowWidget(staged);

            if (BuildOk(app, "second pass")) {
                Check(fs::last_write_time(consumerObject) > objectBefore, "consumer object is recompiled after the interface gains a member");

                auto second = RunCommandWithTimeout(binary.string(), std::chrono::seconds(30));
                Check(second.exitCode == 0 && !second.crashed && !second.timedOut, std::format("second pass agrees on the layout (exit={} output='{}')", second.exitCode, second.output));
            }
        }
    }

    if (Failures > 0) {
        std::println(std::cerr, "{} assertions failed", Failures);
        return 1;
    }
    return 0;
}