package grubenv

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// createTestGrubenv writes a properly formatted grubenv file for testing.
// GRUB requires the file to be exactly 1024 bytes, padded with '#'.
func createTestGrubenv(t *testing.T, dir string, vars map[string]string) string {
	t.Helper()
	path := filepath.Join(dir, "grubenv")

	var sb strings.Builder
	sb.WriteString("# GRUB Environment Block\n")
	for k, v := range vars {
		sb.WriteString(k + "=" + v + "\n")
	}

	content := sb.String()
	padding := 1024 - len(content)
	if padding > 0 {
		content += strings.Repeat("#", padding)
	}

	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
		t.Fatal(err)
	}
	return path
}

func TestNew(t *testing.T) {
	env := New("")
	if env.path != DefaultGrubenvPath {
		t.Errorf("expected default path %s, got %s", DefaultGrubenvPath, env.path)
	}

	env = New("/custom/path/grubenv")
	if env.path != "/custom/path/grubenv" {
		t.Errorf("expected custom path, got %s", env.path)
	}
}

func TestReadAll(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
		"boot_success": "1",
	})

	env := New(path)
	vars, err := env.ReadAll()
	if err != nil {
		t.Fatal(err)
	}

	if vars["active_slot"] != "A" {
		t.Errorf("active_slot: expected A, got %s", vars["active_slot"])
	}
	if vars["boot_counter"] != "3" {
		t.Errorf("boot_counter: expected 3, got %s", vars["boot_counter"])
	}
	if vars["boot_success"] != "1" {
		t.Errorf("boot_success: expected 1, got %s", vars["boot_success"])
	}
}

func TestGet(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot": "B",
	})

	env := New(path)

	val, err := env.Get("active_slot")
	if err != nil {
		t.Fatal(err)
	}
	if val != "B" {
		t.Errorf("expected B, got %s", val)
	}

	_, err = env.Get("nonexistent")
	if err == nil {
		t.Fatal("expected error for nonexistent key")
	}
}

func TestSet(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
	})

	env := New(path)

	if err := env.Set("boot_counter", "2"); err != nil {
		t.Fatal(err)
	}

	val, err := env.Get("boot_counter")
	if err != nil {
		t.Fatal(err)
	}
	if val != "2" {
		t.Errorf("expected 2 after set, got %s", val)
	}

	// Verify file is still 1024 bytes
	data, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	if len(data) != 1024 {
		t.Errorf("grubenv should be 1024 bytes, got %d", len(data))
	}
}

func TestActiveSlot(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
		"boot_success": "1",
	})

	env := New(path)
	slot, err := env.ActiveSlot()
	if err != nil {
		t.Fatal(err)
	}
	if slot != "A" {
		t.Errorf("expected A, got %s", slot)
	}
}

func TestPassiveSlot(t *testing.T) {
	tests := []struct {
		active  string
		passive string
	}{
		{"A", "B"},
		{"B", "A"},
	}

	for _, tt := range tests {
		t.Run("active_"+tt.active, func(t *testing.T) {
			dir := t.TempDir()
			path := createTestGrubenv(t, dir, map[string]string{
				"active_slot": tt.active,
			})

			env := New(path)
			passive, err := env.PassiveSlot()
			if err != nil {
				t.Fatal(err)
			}
			if passive != tt.passive {
				t.Errorf("expected passive %s, got %s", tt.passive, passive)
			}
		})
	}
}

func TestBootCounter(t *testing.T) {
	tests := []struct {
		value   string
		expect  int
		wantErr bool
	}{
		{"0", 0, false},
		{"1", 1, false},
		{"2", 2, false},
		{"3", 3, false},
		{"invalid", -1, true},
		{"99", -1, true},
	}

	for _, tt := range tests {
		t.Run("counter_"+tt.value, func(t *testing.T) {
			dir := t.TempDir()
			path := createTestGrubenv(t, dir, map[string]string{
				"boot_counter": tt.value,
			})

			env := New(path)
			counter, err := env.BootCounter()
			if tt.wantErr {
				if err == nil {
					t.Fatal("expected error")
				}
				return
			}
			if err != nil {
				t.Fatal(err)
			}
			if counter != tt.expect {
				t.Errorf("expected %d, got %d", tt.expect, counter)
			}
		})
	}
}

func TestBootSuccess(t *testing.T) {
	tests := []struct {
		value  string
		expect bool
	}{
		{"0", false},
		{"1", true},
	}

	for _, tt := range tests {
		t.Run("success_"+tt.value, func(t *testing.T) {
			dir := t.TempDir()
			path := createTestGrubenv(t, dir, map[string]string{
				"boot_success": tt.value,
			})

			env := New(path)
			success, err := env.BootSuccess()
			if err != nil {
				t.Fatal(err)
			}
			if success != tt.expect {
				t.Errorf("expected %v, got %v", tt.expect, success)
			}
		})
	}
}

func TestMarkBootSuccess(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "B",
		"boot_counter": "1",
		"boot_success": "0",
	})

	env := New(path)
	if err := env.MarkBootSuccess(); err != nil {
		t.Fatal(err)
	}

	success, err := env.BootSuccess()
	if err != nil {
		t.Fatal(err)
	}
	if !success {
		t.Error("expected boot_success=1 after MarkBootSuccess")
	}

	counter, err := env.BootCounter()
	if err != nil {
		t.Fatal(err)
	}
	if counter != 3 {
		t.Errorf("expected boot_counter=3 after MarkBootSuccess, got %d", counter)
	}
}

func TestActivateSlot(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
		"boot_success": "1",
	})

	env := New(path)
	if err := env.ActivateSlot("B"); err != nil {
		t.Fatal(err)
	}

	slot, _ := env.ActiveSlot()
	if slot != "B" {
		t.Errorf("expected active_slot=B, got %s", slot)
	}

	counter, _ := env.BootCounter()
	if counter != 3 {
		t.Errorf("expected boot_counter=3, got %d", counter)
	}

	success, _ := env.BootSuccess()
	if success {
		t.Error("expected boot_success=0 after ActivateSlot")
	}
}

func TestActivateSlotInvalid(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot": "A",
	})

	env := New(path)
	err := env.ActivateSlot("C")
	if err == nil {
		t.Fatal("expected error for invalid slot")
	}
}

func TestForceRollback(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
		"boot_success": "1",
	})

	env := New(path)
	if err := env.ForceRollback(); err != nil {
		t.Fatal(err)
	}

	slot, _ := env.ActiveSlot()
	if slot != "B" {
		t.Errorf("expected active_slot=B after rollback from A, got %s", slot)
	}
}

func TestParseEnvOutput(t *testing.T) {
	input := `# GRUB Environment Block
active_slot=A
boot_counter=3
boot_success=1

`
	vars := parseEnvOutput(input)

	if len(vars) != 3 {
		t.Errorf("expected 3 variables, got %d", len(vars))
	}
	if vars["active_slot"] != "A" {
		t.Errorf("active_slot: expected A, got %s", vars["active_slot"])
	}
	if vars["boot_counter"] != "3" {
		t.Errorf("boot_counter: expected 3, got %s", vars["boot_counter"])
	}
}

func TestWriteManualFormat(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "grubenv")

	env := New(path)
	// Use setManual directly since grub-editenv may not be available
	err := env.setManual("test_key", "test_value")
	if err != nil {
		t.Fatal(err)
	}

	data, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}

	if len(data) != 1024 {
		t.Errorf("grubenv should be exactly 1024 bytes, got %d", len(data))
	}

	if !strings.HasPrefix(string(data), "# GRUB Environment Block\n") {
		t.Error("grubenv should start with '# GRUB Environment Block'")
	}

	if !strings.Contains(string(data), "test_key=test_value\n") {
		t.Error("grubenv should contain test_key=test_value")
	}
}

func TestReadNonexistentFile(t *testing.T) {
	env := New("/nonexistent/path/grubenv")
	_, err := env.ReadAll()
	if err == nil {
		t.Fatal("expected error reading nonexistent file")
	}
}

func TestMultipleSetOperations(t *testing.T) {
	dir := t.TempDir()
	path := createTestGrubenv(t, dir, map[string]string{
		"active_slot":  "A",
		"boot_counter": "3",
		"boot_success": "1",
	})

	env := New(path)

	// Simulate a boot cycle: decrement counter, then mark success
	if err := env.Set("boot_counter", "2"); err != nil {
		t.Fatal(err)
	}
	if err := env.Set("boot_success", "0"); err != nil {
		t.Fatal(err)
	}

	// Now mark boot success
	if err := env.MarkBootSuccess(); err != nil {
		t.Fatal(err)
	}

	// Verify final state
	vars, err := env.ReadAll()
	if err != nil {
		t.Fatal(err)
	}

	if vars["active_slot"] != "A" {
		t.Errorf("active_slot should still be A, got %s", vars["active_slot"])
	}
	if vars["boot_counter"] != "3" {
		t.Errorf("boot_counter should be 3 after mark success, got %s", vars["boot_counter"])
	}
	if vars["boot_success"] != "1" {
		t.Errorf("boot_success should be 1, got %s", vars["boot_success"])
	}
}