package backends

import (
	"encoding/json"
	"fmt"
	"llamactl/pkg/config"
	"llamactl/pkg/validation"
	"maps"
)

type BackendType string

const (
	BackendTypeLlamaCpp BackendType = "llama_cpp"
	BackendTypeMlxLm    BackendType = "mlx_lm"
	BackendTypeVllm     BackendType = "vllm"
)

type backend interface {
	BuildCommandArgs() []string
	BuildDockerArgs() []string
	GetPort() int
	SetPort(int)
	GetHost() string
	Validate() error
	ParseCommand(string) (any, error)
}

var backendConstructors = map[BackendType]func() backend{
	BackendTypeLlamaCpp: func() backend { return &LlamaServerOptions{} },
	BackendTypeMlxLm:    func() backend { return &MlxServerOptions{} },
	BackendTypeVllm:     func() backend { return &VllmServerOptions{} },
}

type Options struct {
	BackendType    BackendType    `json:"backend_type"`
	BackendOptions map[string]any `json:"backend_options,omitempty"`

	// Backend-specific options
	LlamaServerOptions *LlamaServerOptions `json:"-"`
	MlxServerOptions   *MlxServerOptions   `json:"-"`
	VllmServerOptions  *VllmServerOptions  `json:"-"`
}

func (o *Options) UnmarshalJSON(data []byte) error {
	type Alias Options
	aux := &struct {
		*Alias
	}{
		Alias: (*Alias)(o),
	}

	if err := json.Unmarshal(data, aux); err != nil {
		return err
	}

	// Create backend from constructor map
	if o.BackendOptions != nil {
		constructor, exists := backendConstructors[o.BackendType]
		if !exists {
			return fmt.Errorf("unsupported backend type: %s", o.BackendType)
		}

		backend := constructor()
		optionsData, err := json.Marshal(o.BackendOptions)
		if err != nil {
			return fmt.Errorf("failed to marshal backend options: %w", err)
		}

		if err := json.Unmarshal(optionsData, backend); err != nil {
			return fmt.Errorf("failed to unmarshal backend options: %w", err)
		}

		// Store in the appropriate typed field for backward compatibility
		o.setBackendOptions(backend)
	}

	return nil
}

func (o *Options) MarshalJSON() ([]byte, error) {
	type Alias Options
	aux := &struct {
		*Alias
	}{
		Alias: (*Alias)(o),
	}

	// Get backend and marshal it
	backend := o.getBackend()
	if backend != nil {
		optionsData, err := json.Marshal(backend)
		if err != nil {
			return nil, fmt.Errorf("failed to marshal backend options: %w", err)
		}
		if err := json.Unmarshal(optionsData, &aux.BackendOptions); err != nil {
			return nil, fmt.Errorf("failed to unmarshal backend options to map: %w", err)
		}
	}

	return json.Marshal(aux)
}

// setBackendOptions stores the backend in the appropriate typed field
func (o *Options) setBackendOptions(bcknd backend) {
	switch v := bcknd.(type) {
	case *LlamaServerOptions:
		o.LlamaServerOptions = v
	case *MlxServerOptions:
		o.MlxServerOptions = v
	case *VllmServerOptions:
		o.VllmServerOptions = v
	}
}

func (o *Options) getBackendSettings(backendConfig *config.BackendConfig) *config.BackendSettings {
	switch o.BackendType {
	case BackendTypeLlamaCpp:
		return &backendConfig.LlamaCpp
	case BackendTypeMlxLm:
		return &backendConfig.MLX
	case BackendTypeVllm:
		return &backendConfig.VLLM
	default:
		return nil
	}
}

// getBackend returns the actual backend implementation
func (o *Options) getBackend() backend {
	switch o.BackendType {
	case BackendTypeLlamaCpp:
		return o.LlamaServerOptions
	case BackendTypeMlxLm:
		return o.MlxServerOptions
	case BackendTypeVllm:
		return o.VllmServerOptions
	default:
		return nil
	}
}

func (o *Options) isDockerEnabled(backend *config.BackendSettings) bool {
	if backend.Docker != nil && backend.Docker.Enabled && o.BackendType != BackendTypeMlxLm {
		return true
	}
	return false
}

func (o *Options) IsDockerEnabled(backendConfig *config.BackendConfig) bool {
	backendSettings := o.getBackendSettings(backendConfig)
	return o.isDockerEnabled(backendSettings)
}

// GetCommand builds the command to run the backend
func (o *Options) GetCommand(backendConfig *config.BackendConfig) string {

	backendSettings := o.getBackendSettings(backendConfig)

	if o.isDockerEnabled(backendSettings) {
		return "docker"
	}

	return backendSettings.Command
}

// buildCommandArgs builds command line arguments for the backend
func (o *Options) BuildCommandArgs(backendConfig *config.BackendConfig) []string {

	var args []string

	backendSettings := o.getBackendSettings(backendConfig)
	backend := o.getBackend()
	if backend == nil {
		return args
	}

	if o.isDockerEnabled(backendSettings) {
		// For Docker, start with Docker args
		args = append(args, backendSettings.Docker.Args...)
		args = append(args, backendSettings.Docker.Image)
		args = append(args, backend.BuildDockerArgs()...)

	} else {
		// For native execution, start with backend args
		args = append(args, backendSettings.Args...)
		args = append(args, backend.BuildCommandArgs()...)
	}

	return args
}

// BuildEnvironment builds the environment variables for the backend process
func (o *Options) BuildEnvironment(backendConfig *config.BackendConfig, environment map[string]string) map[string]string {

	backendSettings := o.getBackendSettings(backendConfig)
	env := map[string]string{}

	if backendSettings.Environment != nil {
		maps.Copy(env, backendSettings.Environment)
	}

	if o.isDockerEnabled(backendSettings) {
		if backendSettings.Docker.Environment != nil {
			maps.Copy(env, backendSettings.Docker.Environment)
		}
	}

	if environment != nil {
		maps.Copy(env, environment)
	}

	return env
}

func (o *Options) GetPort() int {
	backend := o.getBackend()
	if backend != nil {
		return backend.GetPort()
	}
	return 0
}

func (o *Options) SetPort(port int) {
	backend := o.getBackend()
	if backend != nil {
		backend.SetPort(port)
	}
}

func (o *Options) GetHost() string {
	backend := o.getBackend()
	if backend != nil {
		return backend.GetHost()
	}
	return "localhost"
}

func (o *Options) GetResponseHeaders(backendConfig *config.BackendConfig) map[string]string {
	backendSettings := o.getBackendSettings(backendConfig)
	return backendSettings.ResponseHeaders
}

// ValidateInstanceOptions performs validation based on backend type
func (o *Options) ValidateInstanceOptions() error {
	backend := o.getBackend()
	if backend == nil {
		return validation.ValidationError(fmt.Errorf("backend options cannot be nil for backend type %s", o.BackendType))
	}

	return backend.Validate()
}