package aiprompts

import (
	"regexp"
	"strings"

	"github.com/descrybe/descrybe-v2/apps/api/internal/security"
)

// varToken matches {{name}} with optional whitespace. Only [a-z0-9_]+ names.
var varToken = regexp.MustCompile(`\{\{\s*([a-z][a-z0-9_]*)\s*\}\}`)

// Vars is the substitution map for Render (keys without braces).
type Vars map[string]string

// Render replaces {{var}} tokens. Unknown variables become empty string (safe, deterministic).
// Templates are sanitized before render; values should already be sanitized by callers.
func Render(template string, vars Vars) string {
	template = strings.TrimSpace(template)
	if template == "" {
		return ""
	}
	return varToken.ReplaceAllStringFunc(template, func(match string) string {
		sub := varToken.FindStringSubmatch(match)
		if len(sub) < 2 {
			return ""
		}
		name := sub[1]
		if vars == nil {
			return ""
		}
		return vars[name]
	})
}

// SanitizeTemplate cleans and bounds a stored prompt template.
func SanitizeTemplate(s string, maxRunes int) string {
	return security.SanitizePrompt(s, maxRunes)
}

// ExtractVariables returns unique variable names found in template (sorted order of first appearance).
func ExtractVariables(template string) []string {
	matches := varToken.FindAllStringSubmatch(template, -1)
	if len(matches) == 0 {
		return nil
	}
	seen := map[string]struct{}{}
	out := make([]string, 0, len(matches))
	for _, m := range matches {
		if len(m) < 2 {
			continue
		}
		name := m[1]
		if _, ok := seen[name]; ok {
			continue
		}
		seen[name] = struct{}{}
		out = append(out, name)
	}
	return out
}