package process

import (
	"bufio"
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

func TestRunPassesArgumentsDirectoryAndEnvironment(t *testing.T) {
	workdir := filepath.Join(t.TempDir(), "directory with spaces")
	if err := os.Mkdir(workdir, 0o700); err != nil {
		t.Fatal(err)
	}
	t.Setenv("RELEASEKIT_PROCESS_OVERLAY", "parent")
	t.Setenv("RELEASEKIT_PROCESS_INHERITED", "inherited")

	var stdout, stderr bytes.Buffer
	err := Run(context.Background(), Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "argument with spaces", "success"},
		Dir:  workdir,
		Env: map[string]string{
			"RELEASEKIT_PROCESS_HELPER":  "1",
			"RELEASEKIT_PROCESS_OVERLAY": "child",
		},
		Stdout: &stdout,
		Stderr: &stderr,
	})
	if err != nil {
		t.Fatal(err)
	}
	want := fmt.Sprintf("%s|argument with spaces|child|inherited", workdir)
	if stdout.String() != want {
		t.Fatalf("stdout = %q, want %q", stdout.String(), want)
	}
	if stderr.String() != "child stderr\n" {
		t.Fatalf("stderr = %q, want %q", stderr.String(), "child stderr\n")
	}
	if got := os.Getenv("RELEASEKIT_PROCESS_OVERLAY"); got != "parent" {
		t.Fatalf("parent environment changed: got %q, want %q", got, "parent")
	}
}

func TestRunPreservesExitError(t *testing.T) {
	err := Run(context.Background(), Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "exit"},
		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
	})
	var exitErr *exec.ExitError
	if !errors.As(err, &exitErr) || exitErr.ExitCode() != 7 {
		t.Fatalf("Run() error = %v, want exit code 7", err)
	}
}

func TestRunCanRemoveInheritedEnvironment(t *testing.T) {
	t.Setenv("RELEASEKIT_PROCESS_INHERITED", "inherited")
	var stdout bytes.Buffer
	err := Run(context.Background(), Invocation{
		Args:     []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "argument", "success"},
		Env:      map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
		UnsetEnv: []string{"RELEASEKIT_PROCESS_INHERITED"},
		Stdout:   &stdout,
	})
	if err != nil {
		t.Fatal(err)
	}
	want := fmt.Sprintf("%s|argument||", mustGetwd(t))
	if stdout.String() != want {
		t.Fatalf("stdout = %q, want %q", stdout.String(), want)
	}
}

func TestRunReportsMissingExecutable(t *testing.T) {
	err := Run(context.Background(), Invocation{Args: []string{"releasekit-command-that-does-not-exist"}})
	if err == nil || !strings.Contains(err.Error(), "releasekit-command-that-does-not-exist") {
		t.Fatalf("Run() error = %v, want missing executable diagnostic", err)
	}
}

func TestRunReturnsCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	started := make(chan struct{}, 1)
	invocation := Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "wait"},
		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
		Stdout: writerFunc(func([]byte) (int, error) {
			select {
			case started <- struct{}{}:
			default:
			}
			return len("started\n"), nil
		}),
	}

	result := make(chan error, 1)
	go func() { result <- Run(ctx, invocation) }()
	select {
	case <-started:
		cancel()
	case <-time.After(5 * time.Second):
		t.Fatal("child did not start")
	}
	select {
	case err := <-result:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("Run() error = %v, want context cancellation", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("Run() did not return after cancellation")
	}
}

func TestStartPipedExchangesBeforeInputEOFAndPreservesSettings(t *testing.T) {
	workdir := filepath.Join(t.TempDir(), "piped directory")
	if err := os.Mkdir(workdir, 0o700); err != nil {
		t.Fatal(err)
	}
	t.Setenv("RELEASEKIT_PROCESS_OVERLAY", "parent")
	t.Setenv("RELEASEKIT_PROCESS_INHERITED", "inherited")
	var stderr bytes.Buffer
	child, err := StartPiped(context.Background(), Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "argument with spaces", "exchange"},
		Dir:  workdir,
		Env: map[string]string{
			"RELEASEKIT_PROCESS_HELPER":  "1",
			"RELEASEKIT_PROCESS_OVERLAY": "child",
		},
		Stderr: &stderr,
	})
	if err != nil {
		t.Fatal(err)
	}
	if _, err := io.WriteString(child.Stdin(), "request\n"); err != nil {
		t.Fatal(err)
	}
	response, err := bufio.NewReader(child.Stdout()).ReadString('\n')
	if err != nil {
		t.Fatalf("read response before closing input: %v", err)
	}
	want := fmt.Sprintf("request|%s|argument with spaces|child|inherited\n", workdir)
	if response != want {
		t.Fatalf("piped response = %q, want %q", response, want)
	}
	if err := child.Stdin().Close(); err != nil {
		t.Fatal(err)
	}
	if _, err := io.Copy(io.Discard, child.Stdout()); err != nil {
		t.Fatal(err)
	}
	if err := child.Wait(); err != nil {
		t.Fatal(err)
	}
	if got := stderr.String(); got != "child stderr\n" {
		t.Fatalf("child stderr = %q, want %q", got, "child stderr\n")
	}
	if got := os.Getenv("RELEASEKIT_PROCESS_OVERLAY"); got != "parent" {
		t.Fatalf("parent environment changed: got %q, want %q", got, "parent")
	}
}

func TestStartPipedCancellationAfterReadinessReapsChild(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	child, err := StartPiped(ctx, Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "wait"},
		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
	})
	if err != nil {
		cancel()
		t.Fatal(err)
	}
	line, err := bufio.NewReader(child.Stdout()).ReadString('\n')
	if err != nil || line != "started\n" {
		cancel()
		_ = child.Stdin().Close()
		_ = child.Stdout().Close()
		_ = child.Wait()
		t.Fatalf("readiness = %q, %v; want started signal", line, err)
	}
	cancel()
	if err := child.Stdin().Close(); err != nil {
		t.Fatal(err)
	}
	if err := child.Stdout().Close(); err != nil {
		t.Fatal(err)
	}
	if err := child.Wait(); !errors.Is(err, context.Canceled) {
		t.Fatalf("Wait() error = %v, want context cancellation", err)
	}
}

func TestStartPipedCancelDoesNotCancelParentContext(t *testing.T) {
	ctx := context.Background()
	child, err := StartPiped(ctx, Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "wait"},
		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
	})
	if err != nil {
		t.Fatal(err)
	}
	line, err := bufio.NewReader(child.Stdout()).ReadString('\n')
	if err != nil || line != "started\n" {
		child.Cancel()
		_ = child.Stdin().Close()
		_ = child.Stdout().Close()
		_ = child.Wait()
		t.Fatalf("readiness = %q, %v; want started signal", line, err)
	}
	child.Cancel()
	if err := child.Stdin().Close(); err != nil {
		t.Fatal(err)
	}
	if err := child.Stdout().Close(); err != nil {
		t.Fatal(err)
	}
	err = child.Wait()
	var exitErr *exec.ExitError
	if !errors.As(err, &exitErr) {
		t.Fatalf("Wait() error = %v, want interrupted child exit", err)
	}
	if ctx.Err() != nil {
		t.Fatalf("child cancellation changed parent context: %v", ctx.Err())
	}
}

func TestStartPipedReportsStartFailure(t *testing.T) {
	child, err := StartPiped(context.Background(), Invocation{Args: []string{"releasekit-command-that-does-not-exist"}})
	if err == nil || child != nil || !strings.Contains(err.Error(), "releasekit-command-that-does-not-exist") {
		t.Fatalf("StartPiped() = %#v, %v; want a missing executable error", child, err)
	}
}

func TestStartPipedPreservesNonzeroExit(t *testing.T) {
	child, err := StartPiped(context.Background(), Invocation{
		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "exit"},
		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
	})
	if err != nil {
		t.Fatal(err)
	}
	if err := child.Stdin().Close(); err != nil {
		t.Fatal(err)
	}
	if _, err := io.Copy(io.Discard, child.Stdout()); err != nil {
		t.Fatal(err)
	}
	err = child.Wait()
	var exitErr *exec.ExitError
	if !errors.As(err, &exitErr) || exitErr.ExitCode() != 7 {
		t.Fatalf("Wait() error = %v, want exit code 7", err)
	}
}

func TestProcessHelper(t *testing.T) {
	if os.Getenv("RELEASEKIT_PROCESS_HELPER") != "1" {
		return
	}
	args := os.Args
	if len(args) < 2 {
		os.Exit(8)
	}
	mode := args[len(args)-1]
	switch mode {
	case "success":
		workdir, err := os.Getwd()
		if err != nil {
			os.Exit(9)
		}
		fmt.Fprintf(os.Stdout, "%s|%s|%s|%s", workdir, args[len(args)-2], os.Getenv("RELEASEKIT_PROCESS_OVERLAY"), os.Getenv("RELEASEKIT_PROCESS_INHERITED"))
		fmt.Fprintln(os.Stderr, "child stderr")
		os.Exit(0)
	case "exit":
		os.Exit(7)
	case "wait":
		fmt.Fprintln(os.Stdout, "started")
		for {
			time.Sleep(time.Second)
		}
	case "exchange":
		reader := bufio.NewReader(os.Stdin)
		request, err := reader.ReadString('\n')
		if err != nil {
			os.Exit(11)
		}
		workdir, err := os.Getwd()
		if err != nil {
			os.Exit(12)
		}
		fmt.Fprintf(os.Stdout, "%s|%s|%s|%s|%s\n", strings.TrimSuffix(request, "\n"), workdir, args[len(args)-2], os.Getenv("RELEASEKIT_PROCESS_OVERLAY"), os.Getenv("RELEASEKIT_PROCESS_INHERITED"))
		fmt.Fprintln(os.Stderr, "child stderr")
		if _, err := io.Copy(io.Discard, reader); err != nil {
			os.Exit(13)
		}
	default:
		os.Exit(10)
	}
}

type writerFunc func([]byte) (int, error)

func (write writerFunc) Write(p []byte) (int, error) {
	return write(p)
}

func helperExecutable(t *testing.T) string {
	t.Helper()
	executable, err := os.Executable()
	if err != nil {
		t.Fatal(err)
	}
	return executable
}

func mustGetwd(t *testing.T) string {
	t.Helper()
	workdir, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	return workdir
}