package config

import (
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/spf13/viper"
)

func TestNewViperConfig(t *testing.T) {
	t.Parallel()

	v := viper.New()
	v.Set("test.key", "test.value")

	cfg := NewViperConfig(v)

	if cfg == nil {
		t.Fatal("NewViperConfig returned nil")
	}

	// Verify it implements the interface (compile-time check)
	_ = cfg
}

func TestViperConfig_Get(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue any
		want     any
	}{
		{
			name:     "string value",
			key:      "test.string",
			setValue: "test",
			want:     "test",
		},
		{
			name:     "int value",
			key:      "test.int",
			setValue: 42,
			want:     42,
		},
		{
			name:     "bool value",
			key:      "test.bool",
			setValue: true,
			want:     true,
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: nil,
			want:     nil,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			if tt.setValue != nil {
				v.Set(tt.key, tt.setValue)
			}

			cfg := NewViperConfig(v)
			got := cfg.Get(tt.key)

			if got != tt.want {
				t.Errorf("Get(%q) = %v, want %v", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_GetString(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue string
		want     string
	}{
		{
			name:     "valid string",
			key:      "test.string",
			setValue: "hello",
			want:     "hello",
		},
		{
			name:     "empty string",
			key:      "test.empty",
			setValue: "",
			want:     "",
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: "",
			want:     "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			v.Set(tt.key, tt.setValue)

			cfg := NewViperConfig(v)
			got := cfg.GetString(tt.key)

			if got != tt.want {
				t.Errorf("GetString(%q) = %q, want %q", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_GetInt(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue int
		want     int
	}{
		{
			name:     "valid int",
			key:      "test.int",
			setValue: 42,
			want:     42,
		},
		{
			name:     "zero value",
			key:      "test.zero",
			setValue: 0,
			want:     0,
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: 0,
			want:     0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			v.Set(tt.key, tt.setValue)

			cfg := NewViperConfig(v)
			got := cfg.GetInt(tt.key)

			if got != tt.want {
				t.Errorf("GetInt(%q) = %d, want %d", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_GetBool(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue bool
		want     bool
	}{
		{
			name:     "true value",
			key:      "test.bool",
			setValue: true,
			want:     true,
		},
		{
			name:     "false value",
			key:      "test.bool",
			setValue: false,
			want:     false,
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: false,
			want:     false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			v.Set(tt.key, tt.setValue)

			cfg := NewViperConfig(v)
			got := cfg.GetBool(tt.key)

			if got != tt.want {
				t.Errorf("GetBool(%q) = %v, want %v", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_GetStringSlice(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue []string
		want     []string
	}{
		{
			name:     "valid slice",
			key:      "test.slice",
			setValue: []string{"a", "b", "c"},
			want:     []string{"a", "b", "c"},
		},
		{
			name:     "empty slice",
			key:      "test.empty",
			setValue: []string{},
			want:     []string{},
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: nil,
			want:     nil,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			v.Set(tt.key, tt.setValue)

			cfg := NewViperConfig(v)
			got := cfg.GetStringSlice(tt.key)

			if len(got) != len(tt.want) {
				t.Errorf("GetStringSlice(%q) length = %d, want %d", tt.key, len(got), len(tt.want))
				return
			}

			for i := range got {
				if got[i] != tt.want[i] {
					t.Errorf("GetStringSlice(%q)[%d] = %q, want %q", tt.key, i, got[i], tt.want[i])
				}
			}
		})
	}
}

func TestViperConfig_GetDuration(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue time.Duration
		want     time.Duration
	}{
		{
			name:     "valid duration",
			key:      "test.duration",
			setValue: 30 * time.Second,
			want:     30 * time.Second,
		},
		{
			name:     "zero duration",
			key:      "test.zero",
			setValue: 0,
			want:     0,
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: 0,
			want:     0,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			v.Set(tt.key, tt.setValue)

			cfg := NewViperConfig(v)
			got := cfg.GetDuration(tt.key)

			if got != tt.want {
				t.Errorf("GetDuration(%q) = %v, want %v", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_IsSet(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		key      string
		setValue any
		want     bool
	}{
		{
			name:     "set key",
			key:      "test.key",
			setValue: "value",
			want:     true,
		},
		{
			name:     "non-existent key",
			key:      "test.missing",
			setValue: nil,
			want:     false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			v := viper.New()
			if tt.setValue != nil {
				v.Set(tt.key, tt.setValue)
			}

			cfg := NewViperConfig(v)
			got := cfg.IsSet(tt.key)

			if got != tt.want {
				t.Errorf("IsSet(%q) = %v, want %v", tt.key, got, tt.want)
			}
		})
	}
}

func TestViperConfig_Unmarshal(t *testing.T) {
	t.Parallel()

	type Config struct {
		Server struct {
			Port int    `mapstructure:"port"`
			Host string `mapstructure:"host"`
		} `mapstructure:"server"`
		Logging struct {
			Level  string `mapstructure:"level"`
			Format string `mapstructure:"format"`
		} `mapstructure:"logging"`
	}

	v := viper.New()
	v.Set("server.port", 8080)
	v.Set("server.host", "localhost")
	v.Set("logging.level", "debug")
	v.Set("logging.format", "json")

	cfg := NewViperConfig(v)

	var result Config
	err := cfg.Unmarshal(&result)
	if err != nil {
		t.Fatalf("Unmarshal failed: %v", err)
	}

	if result.Server.Port != 8080 {
		t.Errorf("Server.Port = %d, want 8080", result.Server.Port)
	}

	if result.Server.Host != "localhost" {
		t.Errorf("Server.Host = %q, want %q", result.Server.Host, "localhost")
	}

	if result.Logging.Level != "debug" {
		t.Errorf("Logging.Level = %q, want %q", result.Logging.Level, "debug")
	}
}

func TestLoadConfig_Default(t *testing.T) {
	// Note: Cannot run in parallel due to os.Chdir() being process-global

	// Create a temporary config directory
	tmpDir := t.TempDir()
	configDir := filepath.Join(tmpDir, "config")
	if err := os.MkdirAll(configDir, 0750); err != nil {
		t.Fatalf("Failed to create config dir: %v", err)
	}

	// Create a default.yaml file
	defaultYAML := `server:
  port: 8080
  host: "localhost"
logging:
  level: "info"
  format: "json"
`
	if err := os.WriteFile(filepath.Join(configDir, "default.yaml"), []byte(defaultYAML), 0600); err != nil {
		t.Fatalf("Failed to write default.yaml: %v", err)
	}

	// Change to temp directory temporarily
	originalDir, err := os.Getwd()
	if err != nil {
		t.Fatalf("Failed to get current directory: %v", err)
	}
	defer func() {
		if err := os.Chdir(originalDir); err != nil {
			t.Logf("Failed to restore directory: %v", err)
		}
	}()

	if err := os.Chdir(tmpDir); err != nil {
		t.Fatalf("Failed to change directory: %v", err)
	}

	cfg, err := LoadConfig("")
	if err != nil {
		t.Fatalf("LoadConfig failed: %v", err)
	}

	if cfg == nil {
		t.Fatal("LoadConfig returned nil")
	}

	// Verify config values
	if cfg.GetString("server.host") != "localhost" {
		t.Errorf("server.host = %q, want %q", cfg.GetString("server.host"), "localhost")
	}

	if cfg.GetInt("server.port") != 8080 {
		t.Errorf("server.port = %d, want 8080", cfg.GetInt("server.port"))
	}
}

func TestLoadConfig_WithEnvironment(t *testing.T) {
	// Note: Cannot run in parallel due to os.Chdir() being process-global

	// Create a temporary config directory
	tmpDir := t.TempDir()
	configDir := filepath.Join(tmpDir, "config")
	if err := os.MkdirAll(configDir, 0750); err != nil {
		t.Fatalf("Failed to create config dir: %v", err)
	}

	// Create default.yaml
	defaultYAML := `server:
  port: 8080
  host: "localhost"
logging:
  level: "info"
`
	if err := os.WriteFile(filepath.Join(configDir, "default.yaml"), []byte(defaultYAML), 0600); err != nil {
		t.Fatalf("Failed to write default.yaml: %v", err)
	}

	// Create development.yaml
	devYAML := `server:
  port: 3000
logging:
  level: "debug"
`
	if err := os.WriteFile(filepath.Join(configDir, "development.yaml"), []byte(devYAML), 0600); err != nil {
		t.Fatalf("Failed to write development.yaml: %v", err)
	}

	// Change to temp directory temporarily
	originalDir, err := os.Getwd()
	if err != nil {
		t.Fatalf("Failed to get current directory: %v", err)
	}
	defer func() {
		if err := os.Chdir(originalDir); err != nil {
			t.Logf("Failed to restore directory: %v", err)
		}
	}()

	if err := os.Chdir(tmpDir); err != nil {
		t.Fatalf("Failed to change directory: %v", err)
	}

	cfg, err := LoadConfig("development")
	if err != nil {
		t.Fatalf("LoadConfig failed: %v", err)
	}

	if cfg == nil {
		t.Fatal("LoadConfig returned nil")
	}

	// Development config should override port
	if cfg.GetInt("server.port") != 3000 {
		t.Errorf("server.port = %d, want 3000", cfg.GetInt("server.port"))
	}

	// Development config should override logging level
	if cfg.GetString("logging.level") != "debug" {
		t.Errorf("logging.level = %q, want %q", cfg.GetString("logging.level"), "debug")
	}

	// Default host should still be present
	if cfg.GetString("server.host") != "localhost" {
		t.Errorf("server.host = %q, want %q", cfg.GetString("server.host"), "localhost")
	}
}

func TestLoadConfig_MissingDefaultFile(t *testing.T) {
	// Note: Cannot run in parallel due to os.Chdir() being process-global

	// Create a temporary directory without config files
	tmpDir := t.TempDir()

	// Change to temp directory temporarily
	originalDir, err := os.Getwd()
	if err != nil {
		t.Fatalf("Failed to get current directory: %v", err)
	}
	defer func() {
		if err := os.Chdir(originalDir); err != nil {
			t.Logf("Failed to restore directory: %v", err)
		}
	}()

	if err := os.Chdir(tmpDir); err != nil {
		t.Fatalf("Failed to change directory: %v", err)
	}

	_, err = LoadConfig("")
	if err == nil {
		t.Fatal("LoadConfig should fail when default.yaml is missing")
	}
}