// Package backend defines the model-agnostic contract every image-generation
// adapter must satisfy. The framework speaks only through Backend; concrete
// adapters (ComfyUI, Replicate, OpenAI, …) translate Request into whatever
// the upstream API expects and return a Result.
package backend

import (
	"context"
	"io"
)

// Request is the cross-backend request shape. Adapters translate it
// to whatever their target API expects. Zero values mean "use backend default"
// unless documented otherwise.
type Request struct {
	Prompt         string
	NegativePrompt string
	Width, Height  int
	Steps          int
	Seed           int64
	Style          string
	BackendOpts    map[string]any
}

// Result is what the backend produces. The caller is responsible for closing
// ImageReader.
type Result struct {
	ImageReader io.ReadCloser
	MimeType    string
	Metadata    map[string]any
}

// Backend is the interface every adapter satisfies.
type Backend interface {
	Name() string
	Generate(ctx context.Context, req Request) (*Result, error)
}