package prompt

import (
	"embed"
	"strings"
	"sync"
)

//go:embed files
var files embed.FS

const (
	fileOverlay       = "files/overlay.md"
	fileStyle8DSystem = "files/style8d.system.md"
	fileStyle8DSchema = "files/style8d.schema.md"
	fileAIChatSystem    = "files/ai.chat.system.md"
	fileIslanderSystem  = "files/ai.islander.system.md"
)

// Keys identify prompt slots loaded from internal/library/prompt/files/*.md.
const (
	KeyStyle8DSystem = "style8d.system"
	KeyStyle8DSchema = "style8d.schema"
	KeyAIChatSystem    = "ai.chat.system"
	KeyIslanderSystem  = "ai.islander.system"
)

var slotFiles = map[string]string{
	KeyStyle8DSystem:  fileStyle8DSystem,
	KeyStyle8DSchema:  fileStyle8DSchema,
	KeyAIChatSystem:   fileAIChatSystem,
	KeyIslanderSystem: fileIslanderSystem,
}

var (
	loadOnce  sync.Once
	loadErr   error
	overlay   string
	slotTexts map[string]string
)

func initRegistry() {
	overlay, loadErr = readFile(fileOverlay)
	if loadErr != nil {
		return
	}
	slotTexts = make(map[string]string, len(slotFiles))
	for key, path := range slotFiles {
		text, err := readFile(path)
		if err != nil {
			loadErr = err
			return
		}
		slotTexts[key] = text
	}
}

func readFile(path string) (string, error) {
	raw, err := files.ReadFile(path)
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(string(raw)), nil
}

func ensureLoaded() error {
	loadOnce.Do(initRegistry)
	return loadErr
}

// Overlay returns the global prepend text (Agents.md style).
func Overlay() (string, error) {
	if err := ensureLoaded(); err != nil {
		return "", err
	}
	return overlay, nil
}

// Slot returns one configured prompt body.
func Slot(key string) (string, error) {
	if err := ensureLoaded(); err != nil {
		return "", err
	}
	text, ok := slotTexts[key]
	if !ok {
		return "", ErrUnknownKey(key)
	}
	return text, nil
}

// KnownKey reports whether key is registered.
func KnownKey(key string) bool {
	_, ok := slotFiles[key]
	return ok
}