package processing

import (
	"strings"

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

func resolveProductPromptTemplates(in ProductInput) (systemTpl, userTpl string) {
	systemTpl = strings.TrimSpace(in.EnhanceSystemTemplate)
	userTpl = strings.TrimSpace(in.EnhanceUserTemplate)
	// Per-category prompt wins for the user message (company system keeps JSON schema / brand).
	if cat := strings.TrimSpace(in.CategoryEnhancePrompt); cat != "" {
		userTpl = ensureCategoryEnhanceUserContext(cat)
	}
	def, ok := aiprompts.DefaultFor(aiprompts.KeyProductEnhance)
	if ok {
		if systemTpl == "" {
			systemTpl = def.SystemTemplate
		}
		if userTpl == "" {
			userTpl = def.UserTemplate
		}
	}
	// Category formulas are language-agnostic; inject once into the shared user skeleton.
	userTpl = AppendFormulaConstraints(userTpl, in.TitleTemplate, in.DescriptionTemplate)
	// Company/built-in system prompts often say "1-2 sentences"; when a category
	// description formula exists, override that so process matches A1 category defs.
	systemTpl = AppendDescriptionFormulaSystemOverride(systemTpl, in.DescriptionTemplate)
	return systemTpl, userTpl
}

// thinEnhanceUserInstruction is prepended when Desc is empty or ≈ Name so the model
// builds copy from Attrs+Category instead of echoing the title.
const thinEnhanceUserInstruction = "Build the description from Attrs and Category only; never copy Name."

// templateHasVar reports whether tpl contains {{name}} (via aiprompts.ExtractVariables).
func templateHasVar(tpl, name string) bool {
	for _, v := range aiprompts.ExtractVariables(tpl) {
		if v == name {
			return true
		}
	}
	return false
}

// ensureCategoryEnhanceUserContext appends standard product context placeholders when a
// category override omits {{attrs}} (common in DB category prompts). Does not rewrite
// category copy that already includes attrs.
func ensureCategoryEnhanceUserContext(userTpl string) string {
	userTpl = strings.TrimSpace(userTpl)
	if userTpl == "" || templateHasVar(userTpl, "attrs") {
		return userTpl
	}
	var b strings.Builder
	b.WriteString(userTpl)
	b.WriteString("\n\n")
	first := true
	appendLine := func(line string) {
		if !first {
			b.WriteByte('\n')
		}
		first = false
		b.WriteString(line)
	}
	if !templateHasVar(userTpl, "category") {
		appendLine("Category: {{category}}")
	}
	if !templateHasVar(userTpl, "name") {
		appendLine("Name: {{name}}")
	}
	if !templateHasVar(userTpl, "description") {
		appendLine("Desc: {{description}}")
	}
	appendLine("Attrs: {{attrs}}")
	return b.String()
}

func isThinEnhanceDescription(desc, name string) bool {
	desc = strings.TrimSpace(desc)
	if desc == "" || desc == "<nil>" {
		return true
	}
	return descriptionEchoesTitle(desc, name)
}

// RenderProductEnhancePrompts fills company/built-in templates with product variables.
func RenderProductEnhancePrompts(systemTpl, userTpl, category, name, description, gtin, brandPrompt, language string, attrs map[string]any) (system, user string) {
	attrsJSON := ""
	compact := CompactAttrs(attrs, MaxAttrKeys)
	if len(compact) > 0 {
		attrsJSON = sanitizeJSON(compact)
	}
	vars := aiprompts.Vars{
		"name":        SanitizeText(truncateRunes(name, 200)),
		"description": SanitizeText(truncateRunes(description, MaxProductDescRunes)),
		"category":    SanitizeText(category),
		"attrs":       attrsJSON,
		"gtin":        SanitizeText(gtin),
		"brand_voice": CompactBrandPrompt(brandPrompt),
		"language":    company.LanguageLabel(language),
	}
	system = strings.TrimSpace(aiprompts.Render(systemTpl, vars))
	user = strings.TrimSpace(aiprompts.Render(userTpl, vars))
	if user == "" {
		// Safety net if a custom user template renders empty.
		user = ProductEnhanceUser(category, name, description, attrs)
	}
	if isThinEnhanceDescription(description, name) {
		user = thinEnhanceUserInstruction + "\n\n" + user
	}
	return system, user
}