package vision

// Assessment is the model's own confidence in reading an image.
type Assessment string

const (
	// AssessmentUnknown means the model reported no self-assessment.
	AssessmentUnknown Assessment = "unknown"
	// AssessmentGood means the model is confident in its read.
	AssessmentGood Assessment = "good"
	// AssessmentPoor means the model judged its recognition as poor.
	AssessmentPoor Assessment = "poor"
)

// ModelInfo describes the main model's vision capability.
type ModelInfo struct {
	// Name identifies the model.
	Name string
	// SupportsVision reports whether the model accepts image input.
	SupportsVision bool
	// SelfAssessment is the model's own confidence for the current image.
	// It drives the layer-2 tool route when SupportsVision is true.
	SelfAssessment Assessment
}

// DecisionKind is the chosen layered route.
type DecisionKind string

const (
	// KindMain routes the image to the main model with the image in context.
	KindMain DecisionKind = "main"
	// KindVisionTool routes to a dedicated vision tool, returning only the tool
	// result so the image never occupies main-model context.
	KindVisionTool DecisionKind = "vision_tool"
	// KindOCRTool routes to an OCR tool, returning only the extracted text.
	KindOCRTool DecisionKind = "ocr_tool"
	// KindUnsupported means no route can process the image.
	KindUnsupported DecisionKind = "unsupported"
)

// Decision is the outcome of a routing call.
type Decision struct {
	// Kind is the chosen route.
	Kind DecisionKind
	// Tool names the vision or OCR tool to invoke, set when Kind is a tool route.
	Tool string
	// Reason is a human-readable explanation for observability and logs.
	Reason string
}

// RouteRequest carries routing hints from the caller on top of the model info.
type RouteRequest struct {
	// TextPrimary reports that the user indicated the image is mainly text, so
	// an OCR tool is preferred over a general vision model.
	TextPrimary bool
	// MainSelfAssessedPoor is set when the main model has already judged its own
	// read of the image as poor, requesting a vision/OCR tool route.
	MainSelfAssessedPoor bool
}

// RouterOption configures a Router.
type RouterOption func(*Router)

// WithVisionTool binds the name of the registered vision-understanding tool.
func WithVisionTool(name string) RouterOption {
	return func(r *Router) {
		if name != "" {
			r.visionTool = name
		}
	}
}

// WithOCRTool binds the name of the registered OCR tool.
func WithOCRTool(name string) RouterOption {
	return func(r *Router) {
		if name != "" {
			r.ocrTool = name
		}
	}
}

// Router implements the layered vision routing policy. It does no I/O; the
// caller uses the returned Decision to dispatch the request.
type Router struct {
	visionTool string
	ocrTool    string
}

// NewRouter builds a Router. Unknown (empty) tool names leave the corresponding
// route unavailable, so the router degrades to KindMain or KindUnsupported.
func NewRouter(opts ...RouterOption) *Router {
	r := &Router{}
	for _, o := range opts {
		o(r)
	}
	return r
}

// Route picks a layered route for an image request given the target model info
// and caller hints. The order is: the main model directly when it can see and
// has not self-assessed poorly (layer 1); otherwise a vision or OCR tool whose
// result replaces the image in context (layers 2 and 3); otherwise
// KindUnsupported when nothing can process the image.
func (r *Router) Route(target ModelInfo, req RouteRequest) Decision {
	poor := target.SelfAssessment == AssessmentPoor || req.MainSelfAssessedPoor
	// Layer 1: the main model accepts images and is confident, so use it first.
	if target.SupportsVision && !poor {
		return Decision{
			Kind:   KindMain,
			Reason: "main model supports vision and is confident; use it directly",
		}
	}
	// OCR is preferred when the user says the image is mostly text.
	if req.TextPrimary && r.ocrTool != "" {
		return Decision{Kind: KindOCRTool, Tool: r.ocrTool, Reason: "image is mainly text; route to OCR"}
	}
	if r.visionTool != "" {
		return Decision{Kind: KindVisionTool, Tool: r.visionTool, Reason: "route to dedicated vision tool"}
	}
	if r.ocrTool != "" {
		return Decision{Kind: KindOCRTool, Tool: r.ocrTool, Reason: "route to OCR tool"}
	}
	// No tool is bound. A sighted main model remains the only option.
	if target.SupportsVision {
		return Decision{Kind: KindMain, Reason: "no vision/OCR tool bound; keep image with main model"}
	}
	return Decision{Kind: KindUnsupported, Reason: "main model cannot see and no vision/OCR tool is bound"}
}