package gotool

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"testing"
	"time"
)

type goPreparationRecord struct {
	Arguments   []string
	Directory   string
	Workspace   string
	Toolchain   string
	Proxy       string
	Private     string
	NoSumDB     string
	ModuleCache string
}

func TestMain(m *testing.M) {
	if os.Getenv("RELEASEKIT_GO_FIXTURE") == "1" {
		os.Exit(runGoPreparationFixture())
	}
	os.Exit(m.Run())
}

func runGoPreparationFixture() int {
	record := goPreparationRecord{
		Arguments: os.Args[1:], Directory: mustGetwd(),
		Workspace: os.Getenv("GOWORK"), Toolchain: os.Getenv("GOTOOLCHAIN"),
		Proxy: os.Getenv("GOPROXY"), Private: os.Getenv("GOPRIVATE"),
		NoSumDB: os.Getenv("GONOSUMDB"), ModuleCache: os.Getenv("GOMODCACHE"),
	}
	contents, err := json.Marshal(record)
	if err != nil {
		return 10
	}
	if err := os.WriteFile(os.Getenv("RELEASEKIT_GO_FIXTURE_RECORD"), contents, 0o600); err != nil {
		return 11
	}
	switch os.Getenv("RELEASEKIT_GO_FIXTURE_MODE") {
	case "discovery":
		settings := make(map[string]string)
		for _, key := range os.Args[3:] {
			settings[key] = os.Getenv(key)
		}
		settings["GOHOSTOS"] = runtime.GOOS
		settings["GOHOSTARCH"] = runtime.GOARCH
		fmt.Fprintln(os.Stderr, "fixture discovery diagnostic")
		if err := json.NewEncoder(os.Stdout).Encode(settings); err != nil {
			return 12
		}
		return 0
	case "fail":
		fmt.Fprintln(os.Stderr, "fixture dependency failure")
		return 23
	case "output":
		fmt.Fprintln(os.Stdout, "fixture stdout")
		fmt.Fprintln(os.Stderr, "fixture stderr")
		return 0
	case "large-fail":
		_, _ = fmt.Fprint(os.Stdout, strings.Repeat("x", 8<<20))
		fmt.Fprintln(os.Stderr, "fixture large failure")
		return 23
	case "wait":
		for {
			time.Sleep(time.Second)
		}
	default:
		return 0
	}
}

func TestDiscoveryAcceptsDiagnosticsWithValidConfiguration(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "discovery")
	cache := filepath.Join(t.TempDir(), "cache")
	t.Setenv("GOCACHE", cache)
	tool, err := New(context.Background(), repository)
	if err != nil {
		t.Fatalf("New() rejected successful discovery: %v", err)
	}
	if tool.HostTarget() != (Target{OS: runtime.GOOS, Arch: runtime.GOARCH}) || tool.settings["GOCACHE"] != cache {
		t.Fatalf("discovered host=%v cache=%q", tool.HostTarget(), tool.settings["GOCACHE"])
	}
}

func TestDiscoveryPreservesFailureDiagnosticsAndCause(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "fail")
	_, err := New(context.Background(), repository)
	var exitError *exec.ExitError
	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture dependency failure") {
		t.Fatalf("New() error = %v", err)
	}
}

func mustGetwd() string {
	directory, err := os.Getwd()
	if err != nil {
		return ""
	}
	return directory
}

func installGoPreparationFixture(t *testing.T) (repository, recordPath string) {
	t.Helper()
	directory := t.TempDir()
	repository = t.TempDir()
	executable, err := os.Executable()
	if err != nil {
		t.Fatal(err)
	}
	contents, err := os.ReadFile(executable)
	if err != nil {
		t.Fatal(err)
	}
	name := "go"
	if runtime.GOOS == "windows" {
		name += ".exe"
	}
	if err := os.WriteFile(filepath.Join(directory, name), contents, 0o755); err != nil {
		t.Fatal(err)
	}
	recordPath = filepath.Join(t.TempDir(), "go-command.json")
	t.Setenv("PATH", directory+string(os.PathListSeparator)+os.Getenv("PATH"))
	t.Setenv("RELEASEKIT_GO_FIXTURE", "1")
	t.Setenv("RELEASEKIT_GO_FIXTURE_RECORD", recordPath)
	return repository, recordPath
}

func TestPrepareBuildDependenciesPreservesPreparationEnvironment(t *testing.T) {
	repository, recordPath := installGoPreparationFixture(t)
	moduleCache := filepath.Join(t.TempDir(), "module-cache")
	t.Setenv("GOWORK", filepath.Join(t.TempDir(), "go.work"))
	t.Setenv("GOTOOLCHAIN", "auto")
	t.Setenv("GOPROXY", "https://proxy.example.invalid")
	t.Setenv("GOPRIVATE", "example.invalid/private")
	t.Setenv("GONOSUMDB", "example.invalid/private")
	t.Setenv("GOMODCACHE", moduleCache)

	if err := PrepareBuildDependencies(context.Background(), repository); err != nil {
		t.Fatal(err)
	}
	contents, err := os.ReadFile(recordPath)
	if err != nil {
		t.Fatal(err)
	}
	var record goPreparationRecord
	if err := json.Unmarshal(contents, &record); err != nil {
		t.Fatal(err)
	}
	if strings.Join(record.Arguments, " ") != "mod download" || record.Directory != repository {
		t.Fatalf("Go invocation = %#v", record)
	}
	if record.Workspace != "off" || record.Toolchain != "local" {
		t.Fatalf("preparation Go settings = %#v", record)
	}
	if record.Proxy != "https://proxy.example.invalid" || record.Private != "example.invalid/private" || record.NoSumDB != "example.invalid/private" || record.ModuleCache != moduleCache {
		t.Fatalf("caller dependency settings were not preserved: %#v", record)
	}
}

func TestPrepareBuildDependenciesPropagatesCommandFailure(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "fail")
	err := PrepareBuildDependencies(context.Background(), repository)
	var exitError *exec.ExitError
	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture dependency failure") {
		t.Fatalf("PrepareBuildDependencies() error = %v", err)
	}
}

func TestPrepareBuildDependenciesPropagatesCancellation(t *testing.T) {
	repository, recordPath := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "wait")
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	done := make(chan error, 1)
	go func() { done <- PrepareBuildDependencies(ctx, repository) }()

	deadline := time.Now().Add(5 * time.Second)
	for {
		if _, err := os.Stat(recordPath); err == nil {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("Go fixture did not start")
		}
		time.Sleep(10 * time.Millisecond)
	}
	cancel()
	select {
	case err := <-done:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("PrepareBuildDependencies() error = %v; want cancellation", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("Go fixture did not stop after cancellation")
	}
}

func TestNativeAndStaticCommandsUseOwnedBaseline(t *testing.T) {
	clearGoSettings(t)
	t.Setenv("GOENV", "off")
	t.Setenv("GOFLAGS", "-run=^$")
	t.Setenv("GOOS", "windows")
	t.Setenv("GOARCH", "arm64")
	t.Setenv("GOAMD64", "v2")
	t.Setenv("GOEXPERIMENT", "loopvar")

	tool, err := New(context.Background(), t.TempDir())
	if err != nil {
		t.Fatal(err)
	}
	if tool.HostTarget() != (Target{OS: runtime.GOOS, Arch: runtime.GOARCH}) {
		t.Fatalf("Go host = %#v, want runtime host %s/%s", tool.HostTarget(), runtime.GOOS, runtime.GOARCH)
	}

	native := readSettings(t, tool, Native, Target{}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "GOAMD64", "GOEXPERIMENT", "CGO_ENABLED")
	if native["GOENV"] != "" || native["GOOS"] != runtime.GOOS || native["GOARCH"] != runtime.GOARCH {
		t.Fatalf("native environment = %#v", native)
	}
	if native["GOFLAGS"] != "-mod=readonly" || native["GOAMD64"] == "v2" || native["GOEXPERIMENT"] != "" {
		t.Fatalf("native Go settings = %#v", native)
	}
	if native["CGO_ENABLED"] == "" {
		t.Fatalf("native cgo setting was not resolved: %#v", native)
	}

	static := readSettings(t, tool, Static, Target{OS: "linux", Arch: "amd64"}, "GOOS", "GOARCH", "GOFLAGS", "CGO_ENABLED", "GOAMD64", "GOEXPERIMENT")
	if static["GOOS"] != "linux" || static["GOARCH"] != "amd64" || static["CGO_ENABLED"] != "0" {
		t.Fatalf("static environment = %#v", static)
	}
	if static["GOFLAGS"] != "-mod=readonly" || static["GOAMD64"] != "v1" || static["GOEXPERIMENT"] != "" {
		t.Fatalf("static baseline settings = %#v", static)
	}
}

func TestPersistentSettingsPreserveCachesAndNativeCTools(t *testing.T) {
	clearGoSettings(t)
	cache := filepath.Join(t.TempDir(), "configured-cache")
	moduleCache := filepath.Join(t.TempDir(), "configured-module-cache")
	temporary := filepath.Join(t.TempDir(), "configured-temporary")
	if err := os.Mkdir(temporary, 0o700); err != nil {
		t.Fatal(err)
	}
	goEnv := filepath.Join(t.TempDir(), "go-env")
	contents := strings.Join([]string{
		"GOFLAGS=-run=^$",
		"GOOS=windows",
		"GOARCH=arm64",
		"GOAMD64=v2",
		"GOEXPERIMENT=loopvar",
		"GOCACHE=" + cache,
		"GOMODCACHE=" + moduleCache,
		"GOTMPDIR=" + temporary,
		"CGO_ENABLED=1",
		"CC=releasekit-test-cc",
		"CXX=releasekit-test-cxx",
		"CGO_CFLAGS=-O0 -g",
		"PKG_CONFIG=releasekit-test-pkg-config",
	}, "\n") + "\n"
	if err := os.WriteFile(goEnv, []byte(contents), 0o600); err != nil {
		t.Fatal(err)
	}
	t.Setenv("GOENV", goEnv)

	tool, err := New(context.Background(), t.TempDir())
	if err != nil {
		t.Fatal(err)
	}
	if tool.HostTarget() != (Target{OS: runtime.GOOS, Arch: runtime.GOARCH}) {
		t.Fatalf("Go host = %#v, want runtime host %s/%s", tool.HostTarget(), runtime.GOOS, runtime.GOARCH)
	}
	native := readSettings(t, tool, Native, Target{}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "GOAMD64", "GOEXPERIMENT", "CGO_ENABLED", "CC", "CXX", "CGO_CFLAGS", "GOCACHE", "GOMODCACHE", "GOTMPDIR", "PKG_CONFIG")
	if native["GOENV"] != "" || native["GOOS"] != runtime.GOOS || native["GOARCH"] != runtime.GOARCH {
		t.Fatalf("native environment = %#v", native)
	}
	if native["GOFLAGS"] != "-mod=readonly" || native["GOAMD64"] == "v2" || native["GOEXPERIMENT"] != "" {
		t.Fatalf("persisted overrides were not cleared: %#v", native)
	}
	if native["CGO_ENABLED"] != "1" || native["CC"] != "releasekit-test-cc" || native["CXX"] != "releasekit-test-cxx" || native["CGO_CFLAGS"] != "-O0 -g" || native["PKG_CONFIG"] != "releasekit-test-pkg-config" {
		t.Fatalf("persistent native C settings = %#v", native)
	}
	if native["GOCACHE"] != cache || native["GOMODCACHE"] != moduleCache || native["GOTMPDIR"] != temporary {
		t.Fatalf("persistent cache settings = %#v", native)
	}
	static := readSettings(t, tool, Static, Target{OS: "linux", Arch: "amd64"}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "CGO_ENABLED", "GOAMD64", "GOEXPERIMENT", "GOCACHE")
	if static["GOENV"] != "" || static["GOOS"] != "linux" || static["GOARCH"] != "amd64" || static["CGO_ENABLED"] != "0" || static["GOAMD64"] != "v1" || static["GOEXPERIMENT"] != "" || static["GOCACHE"] != cache {
		t.Fatalf("persistent static environment = %#v", static)
	}
}

func TestOwnerReusesSettingsUntilInheritedEnvironmentChanges(t *testing.T) {
	clearGoSettings(t)
	t.Setenv("GOENV", "off")
	owner := NewOwner(t.TempDir())

	first, err := owner.Acquire(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	second, err := owner.Acquire(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if first != second {
		t.Fatal("unchanged Go inputs caused settings discovery to be repeated")
	}

	cache := filepath.Join(t.TempDir(), "changed-cache")
	t.Setenv("GOCACHE", cache)
	if err := owner.Refresh(context.Background()); err != nil {
		t.Fatal(err)
	}
	third, err := owner.Acquire(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if third == first || third.settings["GOCACHE"] != cache {
		t.Fatalf("changed inherited environment kept stale settings: tool=%p GOCACHE=%q", third, third.settings["GOCACHE"])
	}
}

func TestOwnerRefreshesWhenPersistentSettingsChange(t *testing.T) {
	clearGoSettings(t)
	firstCache := filepath.Join(t.TempDir(), "first-cache")
	secondCache := filepath.Join(t.TempDir(), "second-cache")
	settingsFile := filepath.Join(t.TempDir(), "go-env")
	writeSettings := func(cache string) {
		t.Helper()
		if err := os.WriteFile(settingsFile, []byte("GOCACHE="+cache+"\n"), 0o600); err != nil {
			t.Fatal(err)
		}
	}
	writeSettings(firstCache)
	t.Setenv("GOENV", settingsFile)
	owner := NewOwner(t.TempDir())

	first, err := owner.Acquire(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if first.settings["GOCACHE"] != firstCache {
		t.Fatalf("initial GOCACHE = %q, want %q", first.settings["GOCACHE"], firstCache)
	}
	writeSettings(secondCache)
	if err := owner.Refresh(context.Background()); err != nil {
		t.Fatal(err)
	}
	second, err := owner.Acquire(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if second == first || second.settings["GOCACHE"] != secondCache {
		t.Fatalf("changed persistent settings were not rediscovered: tool=%p GOCACHE=%q", second, second.settings["GOCACHE"])
	}
}

func readSettings(t *testing.T, tool *Tool, mode Mode, target Target, names ...string) map[string]string {
	t.Helper()
	args := append([]string{"env", "-json"}, names...)
	output, err := tool.Output(context.Background(), t.TempDir(), mode, target, nil, args...)
	if err != nil {
		t.Fatal(err)
	}
	var settings map[string]string
	if err := json.Unmarshal(output, &settings); err != nil {
		t.Fatalf("decode Go environment %q: %v", output, err)
	}
	return settings
}

func TestOutputReturnsAndForwardsCombinedOutput(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
	tool := fixtureTool()
	var forwarded bytes.Buffer

	output, err := tool.Output(context.Background(), repository, Native, Target{}, &forwarded, "version")
	if err != nil {
		t.Fatalf("Output() error = %v", err)
	}
	if !bytes.Contains(output, []byte("fixture stdout")) || !bytes.Contains(output, []byte("fixture stderr")) {
		t.Fatalf("combined output = %q", output)
	}
	if !bytes.Equal(forwarded.Bytes(), output) {
		t.Fatalf("forwarded output differs from capture: forwarded %d bytes, captured %d", forwarded.Len(), len(output))
	}
}

func TestRunForwardsOutputWithoutReturningCapture(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
	tool := fixtureTool()
	var forwarded bytes.Buffer

	if err := tool.Run(context.Background(), repository, Native, Target{}, &forwarded, "version"); err != nil {
		t.Fatalf("Run() error = %v", err)
	}
	if !bytes.Contains(forwarded.Bytes(), []byte("fixture stdout")) || !bytes.Contains(forwarded.Bytes(), []byte("fixture stderr")) {
		t.Fatalf("forwarded output = %q", forwarded.String())
	}
}

func TestRunPreservesFailureDiagnosticsAndCause(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "fail")
	tool := fixtureTool()

	err := tool.Run(context.Background(), repository, Native, Target{}, nil, "version")
	var exitError *exec.ExitError
	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture dependency failure") {
		t.Fatalf("Run() error = %v", err)
	}
}

func TestOutputReturnsLargeFailureDiagnosticsAndCause(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "large-fail")
	tool := fixtureTool()

	output, err := tool.Output(context.Background(), repository, Native, Target{}, nil, "version")
	var exitError *exec.ExitError
	wantSize := (8 << 20) + len("fixture large failure\n")
	if len(output) != wantSize {
		t.Fatalf("captured output = %d bytes, want %d", len(output), wantSize)
	}
	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture large failure") {
		t.Fatalf("Output() error = %v", err)
	}
}

func TestOutputReturnsCancellation(t *testing.T) {
	repository, recordPath := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "wait")
	tool := fixtureTool()
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	done := make(chan error, 1)
	go func() {
		_, err := tool.Output(ctx, repository, Native, Target{}, nil, "version")
		done <- err
	}()

	deadline := time.Now().Add(5 * time.Second)
	for {
		if _, err := os.Stat(recordPath); err == nil {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("Go fixture did not start")
		}
		time.Sleep(10 * time.Millisecond)
	}
	cancel()
	select {
	case err := <-done:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("Output() error = %v; want cancellation", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("Go fixture did not stop after cancellation")
	}
}

func TestOutputPreservesForwardingWriterFailure(t *testing.T) {
	repository, _ := installGoPreparationFixture(t)
	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
	tool := fixtureTool()
	writerErr := errors.New("fixture output writer failed")

	output, err := tool.Output(context.Background(), repository, Native, Target{}, failingOutputWriter{err: writerErr}, "version")
	if !errors.Is(err, writerErr) || !strings.Contains(err.Error(), "go version") {
		t.Fatalf("Output() error = %v; want wrapped writer error and command", err)
	}
	if len(output) == 0 {
		t.Fatal("Output() returned no captured bytes after forwarding failed")
	}
}

type failingOutputWriter struct{ err error }

func (writer failingOutputWriter) Write([]byte) (int, error) { return 0, writer.err }

func fixtureTool() *Tool {
	return &Tool{host: Target{OS: runtime.GOOS, Arch: runtime.GOARCH}, settings: map[string]string{}}
}

func clearGoSettings(t *testing.T) {
	t.Helper()
	for _, key := range []string{
		"GOENV", "GOFLAGS", "GOWORK", "GOTOOLCHAIN", "GOPROXY", "GONOPROXY", "GOSUMDB",
		"GOOS", "GOARCH", "GOEXPERIMENT", "GOAMD64", "GOARM", "GOARM64", "GO386", "GOMIPS", "GOMIPS64", "GOPPC64", "GORISCV64", "GOWASM",
		"CGO_ENABLED", "CC", "CXX", "CGO_CFLAGS", "CGO_CPPFLAGS", "CGO_CXXFLAGS", "CGO_LDFLAGS", "GOCACHE", "GOCACHEPROG", "GOMODCACHE", "GOPATH", "GOROOT", "GOTMPDIR", "PKG_CONFIG",
	} {
		value, exists := os.LookupEnv(key)
		if err := os.Unsetenv(key); err != nil {
			t.Fatal(err)
		}
		t.Cleanup(func() {
			if exists {
				_ = os.Setenv(key, value)
			} else {
				_ = os.Unsetenv(key)
			}
		})
	}
}