package app

import (
	"context"
	"errors"
	"time"
)

// GenerationProvider is the port the domain uses to call the underlying model executor.
type GenerationProvider interface {
	ListModels(ctx context.Context) ([]ModelDescriptor, error)
	Generate(ctx context.Context, req GenerationRequest) (GenerationResponse, error)
}

// Service orchestrates requests across providers and enforces domain rules.
type Service struct {
	provider GenerationProvider
}

func NewService(provider GenerationProvider) *Service {
	return &Service{provider: provider}
}

func (s *Service) Models(ctx context.Context) ([]ModelDescriptor, error) {
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	return s.provider.ListModels(ctx)
}

func (s *Service) Generate(ctx context.Context, req GenerationRequest) (GenerationResponse, error) {
	if req.ModelID == "" {
		return GenerationResponse{}, errors.New("model id is required")
	}
	if req.Prompt == "" && len(req.References) == 0 {
		return GenerationResponse{}, errors.New("prompt or references must be provided")
	}

	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	return s.provider.Generate(ctx, req)
}

// ModelDescriptor describes a generative model exposed via the API.
type ModelDescriptor struct {
	ID           string   `json:"id"`
	Label        string   `json:"label"`
	Provider     string   `json:"provider"`
	Modalities   []string `json:"modalities"`
	Capabilities []string `json:"capabilities"`
}

// GenerationRequest carries a generation task requested by the UI.
type GenerationRequest struct {
	ModelID    string   `json:"modelId"`
	Prompt     string   `json:"prompt"`
	Negative   string   `json:"negativePrompt,omitempty"`
	Aspect     string   `json:"aspect,omitempty"`
	References []string `json:"references,omitempty"`
	UserLocale string   `json:"userLocale,omitempty"`
}

// GenerationResponse summarises the async job triggered by the provider.
type GenerationResponse struct {
	ID        string    `json:"id"`
	ModelID   string    `json:"modelId"`
	Status    string    `json:"status"`
	QueuedAt  time.Time `json:"queuedAt"`
	ExpiresAt time.Time `json:"expiresAt"`
}