package chat

import (
	"fmt"
	"strings"
	"sync"
)

// Renderer renders messages into a single prompt string.
//
//nolint:revive // exported API
type Renderer interface {
	Render(messages []Message, opts Options) (string, error)
}

var (
	mu        sync.RWMutex
	renderers = map[string]Renderer{}
)

// Register registers a renderer for a model architecture (e.g. "qwen3", "llama").
func Register(architecture string, r Renderer) {
	mu.Lock()
	defer mu.Unlock()
	renderers[strings.ToLower(architecture)] = r
}

// RendererForArchitecture returns the renderer for the given architecture.
func RendererForArchitecture(architecture string) (Renderer, bool) {
	mu.RLock()
	defer mu.RUnlock()
	r, ok := renderers[strings.ToLower(architecture)]
	return r, ok
}

// RenderForArchitecture renders chat messages for the given architecture.
func RenderForArchitecture(architecture string, messages []Message, opts Options) (string, error) {
	if r, ok := RendererForArchitecture(architecture); ok {
		return r.Render(messages, opts)
	}
	return (&Qwen3Renderer{}).Render(messages, opts)
}

// MustRenderForArchitecture is a convenience helper.
func MustRenderForArchitecture(architecture string, messages []Message, opts Options) string {
	out, err := RenderForArchitecture(architecture, messages, opts)
	if err != nil {
		panic(fmt.Errorf("render chat template: %w", err))
	}
	return out
}