package process

import (
	"bytes"
	"context"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

func TestProcessFixture(t *testing.T) {
	mode := os.Getenv("MPV_PROCESS_FIXTURE")
	if mode == "" {
		return
	}
	root := os.Getenv("MPV_PROCESS_FIXTURE_DIR")
	if mode == "child" {
		require.NoError(t, os.WriteFile(filepath.Join(root, "ready"), []byte("ready"), 0600))
		time.Sleep(600 * time.Millisecond)
		require.NoError(t, os.WriteFile(filepath.Join(root, "late-write"), []byte("child survived"), 0600))
		time.Sleep(4 * time.Second)
		os.Exit(0)
	}
	if mode == "noisy" {
		_, _ = os.Stdout.WriteString(strings.Repeat("x", 2*1024*1024))
		os.Exit(0)
	}
	child := exec.Command(os.Args[0], "-test.run=^TestProcessFixture$")
	child.Env = append(os.Environ(), "MPV_PROCESS_FIXTURE=child")
	child.Stdout, child.Stderr = os.Stdout, os.Stderr
	require.NoError(t, child.Start())
	if mode == "parent-exits" {
		os.Exit(0)
	}
	_ = child.Wait()
	os.Exit(0)
}

func TestCancellationStopsDescendantWithInheritedOutputPipes(t *testing.T) {
	for _, mode := range []string{"parent-waits", "parent-exits"} {
		t.Run(mode, func(t *testing.T) {
			root := t.TempDir()
			ctx, cancel := context.WithCancel(context.Background())
			defer cancel()
			cmd := exec.Command(os.Args[0], "-test.run=^TestProcessFixture$")
			cmd.Env = append(os.Environ(), "MPV_PROCESS_FIXTURE="+mode, "MPV_PROCESS_FIXTURE_DIR="+root)
			var captured bytes.Buffer
			cmd.Stdout, cmd.Stderr = &captured, &captured
			done := make(chan error, 1)
			go func() { done <- Run(ctx, cmd) }()
			require.Eventually(t, func() bool { _, err := os.Stat(filepath.Join(root, "ready")); return err == nil }, 10*time.Second, 5*time.Millisecond)
			cancel()
			select {
			case err := <-done:
				require.Error(t, err)
			case <-time.After(3 * time.Second):
				t.Fatal("command did not join after cancellation")
			}
			time.Sleep(750 * time.Millisecond)
			require.NoFileExists(t, filepath.Join(root, "late-write"), "descendant must stop before worker releases ownership")
		})
	}
}

func TestOutputIsBoundedAndReportsOverflow(t *testing.T) {
	cmd := exec.Command(os.Args[0], "-test.run=^TestProcessFixture$")
	cmd.Env = append(os.Environ(), "MPV_PROCESS_FIXTURE=noisy")
	data, err := Output(context.Background(), cmd)
	require.ErrorContains(t, err, "exceeded 1 MiB")
	require.Len(t, data, 1024*1024)
}