package app

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"log/slog"
	"net/http"
	"net/url"
	"runtime/debug"
	"sort"
	"strings"
	"time"

	"github.com/b1tsblog/ai-disclosure-standard/internal/background"
	"github.com/b1tsblog/ai-disclosure-standard/internal/badge"
	"github.com/b1tsblog/ai-disclosure-standard/internal/declaration"
	"github.com/b1tsblog/ai-disclosure-standard/internal/i18n"
	"github.com/b1tsblog/ai-disclosure-standard/internal/marketing"
	webassets "github.com/b1tsblog/ai-disclosure-standard/web"
	"github.com/b1tsblog/license-platform/sdk/go/licenseclient"
)

type Server struct {
	cfg       Config
	logger    *slog.Logger
	templates *template.Template
	metrics   *metrics
	licenses  *licenseclient.Client
	mux       *http.ServeMux
}

type option struct{ Value, Label string }
type fact struct{ Label, Value, Link string }
type componentRow struct{ Name, Extent, Activities, Review, Note string }
type languageLink struct {
	Code, Name, URL, AbsoluteURL string
	Current                      bool
}

type pageData struct {
	Name               string
	BaseURL            string
	ContactURL         string
	Lang               string
	Text               map[string]string
	Languages          []i18n.LanguageOption
	Presets            []option
	Components         []option
	Extents            []option
	Reviews            []option
	Assurances         []option
	Declaration        declaration.Declaration
	Title              string
	Description        string
	BadgeURL           string
	ManifestURL        string
	CanonicalURL       string
	JSONLD             template.JS
	AppConfig          template.JS
	Facts              []fact
	ComponentRows      []componentRow
	Summary            []string
	IsArticle          bool
	License            licenseclient.Status
	CustomText         bool
	CustomBadge        bool
	Marketing          marketing.Page
	Background         background.Page
	LanguageLinks      []languageLink
	DefaultLanguageURL string
}

type clientConfig struct {
	BaseURL          string                 `json:"baseURL"`
	SelectedLanguage string                 `json:"selectedLanguage"`
	Locales          map[string]i18n.Locale `json:"locales"`
	Capabilities     map[string]bool        `json:"capabilities"`
}

func New(ctx context.Context, cfg Config, logger *slog.Logger) (http.Handler, error) {
	tmpl, err := template.New("root").ParseFS(webassets.Files, "templates/*.html")
	if err != nil {
		return nil, fmt.Errorf("parse templates: %w", err)
	}
	trustStore, err := productTrustStore()
	if err != nil {
		return nil, err
	}
	licenses := licenseclient.New(ctx, licenseclient.Config{
		Product: ProductID, Token: cfg.LicenseToken, TrustStore: trustStore, BaseURL: cfg.BaseURL,
		InstanceID: cfg.LicenseInstanceID, Mode: cfg.LicenseMode, ServerURL: cfg.LicenseServerURL,
		CacheFile: cfg.LicenseCacheFile, RefreshEvery: cfg.LicenseRefreshEvery,
		RequestTimeout: cfg.LicenseTimeout, ClientVersion: ProductVersion,
	})
	licenses.Start(ctx)
	s := &Server{cfg: cfg, logger: logger, templates: tmpl, metrics: newMetrics(), licenses: licenses, mux: http.NewServeMux()}
	s.routes()
	return s.middleware(s.mux), nil
}

func (s *Server) routes() {
	staticFS, _ := fs.Sub(webassets.Files, "static")
	fileServer := http.FileServer(http.FS(staticFS))
	s.mux.HandleFunc("GET /", s.handleIndex)
	s.mux.HandleFunc("GET /product", s.handleMarketing)
	s.mux.HandleFunc("GET /background", s.handleBackground)
	s.mux.HandleFunc("GET /install", s.handleMarketingAlias)
	s.mux.Handle("GET /static/", http.StripPrefix("/static/", cacheStatic(fileServer)))
	s.mux.HandleFunc("GET /badge/{file}", s.handlePresetBadge)
	s.mux.HandleFunc("GET /v1/badge.svg", s.handleBadge)
	s.mux.HandleFunc("GET /declaration", s.handleDeclaration)
	s.mux.HandleFunc("GET /v1/declaration.json", s.handleManifest)
	s.mux.HandleFunc("POST /v1/validate", s.handleValidate)
	s.mux.HandleFunc("GET /v1/capabilities", s.handleCapabilities)
	s.mux.HandleFunc("GET /schema/v1/declaration.schema.json", s.handleSchema)
	s.mux.HandleFunc("GET /context/v1", s.handleContext)
	s.mux.HandleFunc("GET /healthz", s.handleHealth)
	s.mux.HandleFunc("GET /readyz", s.handleReady)
	s.mux.HandleFunc("GET /metrics", s.metrics.serveHTTP)
}

func (s *Server) handleIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	lang := s.language(r)
	locale := i18n.Get(lang)
	cfg := clientConfig{
		BaseURL: s.cfg.BaseURL, SelectedLanguage: lang, Locales: i18n.ClientCatalogs(),
		Capabilities: map[string]bool{
			FeatureCustomText:  s.licenses.Has(FeatureCustomText),
			FeatureCustomBadge: s.licenses.Has(FeatureCustomBadge),
		},
	}
	appJSON, _ := json.Marshal(cfg)
	data := pageData{
		Name: s.cfg.PublicName, BaseURL: s.cfg.BaseURL, ContactURL: s.cfg.ContactURL, Lang: lang, Text: locale.Text,
		Languages: i18n.Languages(), Presets: presetOptions(locale), Components: orderedOptions(locale.Components, []string{"text", "coverImage", "image", "audio", "video", "code", "other"}),
		Extents: orderedOptions(locale.Extents, []string{"assisted", "none", "partial", "mostly", "full"}), Reviews: orderedOptions(locale.Reviews, []string{"editorial", "expert", "basic", "none"}),
		Assurances: orderedOptions(locale.Assurances, []string{"selfDeclared", "technicallyRecorded", "signed", "verified"}),
		AppConfig:  template.JS(appJSON), License: s.licenses.Status(), CustomText: s.licenses.Has(FeatureCustomText), CustomBadge: s.licenses.Has(FeatureCustomBadge),
	}
	s.renderHTML(w, "index.html", data)
}

func (s *Server) handleBackground(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/background" {
		http.NotFound(w, r)
		return
	}
	lang := s.language(r)
	languageLinks, defaultLanguageURL := s.staticLanguageLinks("/background", lang)
	data := pageData{
		Name: s.cfg.PublicName, BaseURL: s.cfg.BaseURL, ContactURL: s.cfg.ContactURL,
		Lang: lang, Languages: i18n.Languages(), Background: background.Build(lang),
		License: s.licenses.Status(), LanguageLinks: languageLinks, DefaultLanguageURL: defaultLanguageURL,
	}
	s.renderHTML(w, "background.html", data)
}

func (s *Server) staticLanguageLinks(path, current string) ([]languageLink, string) {
	links := make([]languageLink, 0, len(i18n.Languages()))
	for _, language := range i18n.Languages() {
		values := url.Values{"lang": []string{language.Code}}
		relative := path + "?" + values.Encode()
		links = append(links, languageLink{
			Code: language.Code, Name: language.Name, URL: relative,
			AbsoluteURL: s.cfg.BaseURL + relative, Current: language.Code == current,
		})
	}
	return links, s.cfg.BaseURL + path
}

func (s *Server) handleMarketing(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/product" {
		http.NotFound(w, r)
		return
	}
	lang := s.language(r)
	page := marketing.Build(lang, s.cfg.PublicName, s.cfg.BaseURL, s.cfg.SalesURL, s.cfg.ContactURL, marketing.Prices{
		Community: s.cfg.CommunityPrice,
		Pro:       s.cfg.ProPrice,
		Publisher: s.cfg.PublisherPrice,
		Agency:    s.cfg.AgencyPrice,
	})
	data := pageData{
		Name: s.cfg.PublicName, BaseURL: s.cfg.BaseURL, ContactURL: s.cfg.ContactURL,
		Lang: lang, Languages: i18n.Languages(), Marketing: page, License: s.licenses.Status(),
	}
	s.renderHTML(w, "marketing.html", data)
}

func (s *Server) handleMarketingAlias(w http.ResponseWriter, r *http.Request) {
	target := "/product"
	if raw := r.URL.Query().Encode(); raw != "" {
		target += "?" + raw
	}
	if r.URL.Path == "/install" {
		target += "#install"
	}
	http.Redirect(w, r, target, http.StatusTemporaryRedirect)
}

func (s *Server) handlePresetBadge(w http.ResponseWriter, r *http.Request) {
	file := r.PathValue("file")
	if !strings.HasSuffix(file, ".svg") {
		http.NotFound(w, r)
		return
	}
	presetID := strings.TrimSuffix(file, ".svg")
	if _, ok := declaration.Presets[presetID]; !ok {
		s.problem(w, http.StatusNotFound, "unknown_preset", "Unknown badge preset.")
		return
	}
	q := cloneValues(r.URL.Query())
	q.Set("preset", presetID)
	q.Set("lang", s.languageFromValues(r, q))
	s.renderBadge(w, r, q)
}

func (s *Server) handleBadge(w http.ResponseWriter, r *http.Request) {
	q := cloneValues(r.URL.Query())
	q.Set("lang", s.languageFromValues(r, q))
	s.renderBadge(w, r, q)
}

func (s *Server) renderBadge(w http.ResponseWriter, r *http.Request, q url.Values) {
	if customTextRequested(q, "label", "badgeLabel", "message", "badgeMessage") && !s.licenses.Has(FeatureCustomBadge) {
		s.problem(w, http.StatusForbidden, "pro_feature_required", "Custom badge labels require the Pro feature custom_badge.")
		return
	}
	if customTextRequested(q, "leftColor", "rightColor") && !s.licenses.Has(FeatureCustomBadge) {
		s.problem(w, http.StatusForbidden, "pro_feature_required", "Custom badge colours require the Pro feature custom_badge.")
		return
	}
	leftColor, rightColor := strings.TrimSpace(q.Get("leftColor")), strings.TrimSpace(q.Get("rightColor"))
	if (leftColor != "" && !validHexColor(leftColor)) || (rightColor != "" && !validHexColor(rightColor)) {
		s.problem(w, http.StatusBadRequest, "invalid_colour", "Badge colours must use the form #RRGGBB.")
		return
	}
	extent := strings.TrimSpace(q.Get("extent"))
	presetID := strings.TrimSpace(q.Get("preset"))
	isArticle := q.Get("mode") == "article"
	if isArticle {
		if d, err := s.declarationFromQuery(q); err == nil {
			extent = overallExtent(d)
		}
	}
	if p, ok := declaration.Presets[presetID]; ok && extent == "" {
		extent = p.Extent
	}
	if extent == "" {
		extent = "assisted"
	}
	if !declaration.IsValidExtent(extent) {
		s.problem(w, http.StatusBadRequest, "invalid_extent", "extent must be one of none, assisted, partial, mostly or full")
		return
	}
	locale := i18n.Get(q.Get("lang"))
	label := locale.Text["ai_label"]
	message := locale.Extents[extent]
	if preset, ok := locale.Presets[presetID]; ok {
		message = preset.Title
	}
	if isArticle {
		message = locale.Text["badge_article"]
		// Article-level declarations combine several AI-use states. Use a calm
		// violet as the neutral default instead of inheriting the strongest
		// component colour (which may be red). Explicit Pro colours still win.
		if rightColor == "" {
			rightColor = "#7c3aed"
		}
	}
	if v := firstNonEmpty(q.Get("badgeLabel"), q.Get("label")); v != "" {
		label = v
	}
	if v := firstNonEmpty(q.Get("badgeMessage"), q.Get("message")); v != "" {
		message = v
	}
	link := strings.TrimSpace(q.Get("link"))
	if link == "auto" {
		copy := cloneValues(q)
		for _, key := range []string{"link", "label", "message", "style", "theme", "leftColor", "rightColor"} {
			copy.Del(key)
		}
		link = s.cfg.BaseURL + "/declaration?" + copy.Encode()
	}
	data, etag := badge.Render(badge.Options{Label: label, Message: message, Extent: extent, Style: q.Get("style"), Theme: q.Get("theme"), Link: link, LeftColor: leftColor, RightColor: rightColor})
	if r.Header.Get("If-None-Match") == etag {
		w.WriteHeader(http.StatusNotModified)
		return
	}
	s.metrics.badgeRenders.Add(1)
	w.Header().Set("Content-Type", "image/svg+xml; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=300, stale-while-revalidate=86400")
	w.Header().Set("ETag", etag)
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'; sandbox")
	_, _ = w.Write(data)
}

func (s *Server) handleDeclaration(w http.ResponseWriter, r *http.Request) {
	q := cloneValues(r.URL.Query())
	q.Set("lang", s.languageFromValues(r, q))
	d, err := s.declarationFromQuery(q)
	if err != nil {
		s.declarationError(w, err)
		return
	}
	locale := i18n.Get(d.Language)
	presetText := locale.Presets[q.Get("preset")]
	title, description := presetText.Title, presetText.Description
	if title == "" {
		for _, c := range d.Components {
			title = locale.Extents[c.AIExtent]
			break
		}
		description = locale.Text["transparency_text"]
	}
	if d.Presentation != nil {
		if d.Presentation.Title != "" {
			title = d.Presentation.Title
		}
		if d.Presentation.Description != "" {
			description = d.Presentation.Description
		}
	}
	canonicalURL := s.cfg.BaseURL + "/declaration?" + q.Encode()
	manifestURL := s.cfg.BaseURL + "/v1/declaration.json?" + q.Encode()
	badgeQ := cloneValues(q)
	badgeQ.Set("link", canonicalURL)
	badgeURL := s.cfg.BaseURL + "/v1/badge.svg?" + badgeQ.Encode()
	jsonLD, _ := json.Marshal(d)
	isArticle := q.Get("mode") == "article" || len(d.Components) > 1
	if isArticle && (d.Presentation == nil || d.Presentation.Title == "") {
		title = locale.Text["article_title"]
		description = articleShortDescription(d, locale)
	}
	languageLinks, defaultLanguageURL := s.declarationLanguageLinks(q, d.Language)
	data := pageData{
		Name: s.cfg.PublicName, BaseURL: s.cfg.BaseURL, ContactURL: s.cfg.ContactURL, Lang: d.Language, Text: locale.Text, Languages: i18n.Languages(),
		Declaration: d, Title: title, Description: description, BadgeURL: badgeURL, ManifestURL: manifestURL, CanonicalURL: canonicalURL, JSONLD: template.JS(jsonLD),
		Facts: declarationFacts(d, locale), ComponentRows: declarationComponentRows(d, locale), Summary: declarationSummary(d, locale), IsArticle: isArticle, License: s.licenses.Status(),
		LanguageLinks: languageLinks, DefaultLanguageURL: defaultLanguageURL,
	}
	w.Header().Set("Link", "<"+manifestURL+">; rel=describedby; type=application/ld+json")
	s.renderHTML(w, "declaration.html", data)
}

func (s *Server) declarationLanguageLinks(q url.Values, current string) ([]languageLink, string) {
	links := make([]languageLink, 0, len(i18n.Languages()))
	for _, language := range i18n.Languages() {
		values := cloneValues(q)
		values.Set("lang", language.Code)
		relative := "/declaration?" + values.Encode()
		links = append(links, languageLink{
			Code: language.Code, Name: language.Name, URL: relative,
			AbsoluteURL: s.cfg.BaseURL + relative, Current: language.Code == current,
		})
	}
	defaultValues := cloneValues(q)
	defaultValues.Del("lang")
	defaultURL := s.cfg.BaseURL + "/declaration"
	if encoded := defaultValues.Encode(); encoded != "" {
		defaultURL += "?" + encoded
	}
	return links, defaultURL
}

func (s *Server) handleManifest(w http.ResponseWriter, r *http.Request) {
	q := cloneValues(r.URL.Query())
	q.Set("lang", s.languageFromValues(r, q))
	d, err := s.declarationFromQuery(q)
	if err != nil {
		s.declarationError(w, err)
		return
	}
	w.Header().Set("Content-Type", "application/ld+json; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=300, stale-while-revalidate=86400")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	_ = json.NewEncoder(w).Encode(d)
}

func (s *Server) declarationFromQuery(q url.Values) (declaration.Declaration, error) {
	return declaration.NewFromQueryWithOptions(q, s.cfg.BaseURL+"/context/v1", declaration.ParseOptions{
		AllowCustomText: s.licenses.Has(FeatureCustomText), AllowCustomBadge: s.licenses.Has(FeatureCustomBadge), DefaultLanguage: s.cfg.DefaultLanguage,
	})
}

func (s *Server) declarationError(w http.ResponseWriter, err error) {
	if errors.Is(err, declaration.ErrCustomTextRequiresPro) || errors.Is(err, declaration.ErrCustomBadgeRequiresPro) {
		s.problem(w, http.StatusForbidden, "pro_feature_required", err.Error())
		return
	}
	s.problem(w, http.StatusBadRequest, "invalid_declaration", err.Error())
}

func (s *Server) handleValidate(w http.ResponseWriter, r *http.Request) {
	s.metrics.validationRequests.Add(1)
	body := http.MaxBytesReader(w, r.Body, 1<<20)
	defer body.Close()
	dec := json.NewDecoder(body)
	dec.DisallowUnknownFields()
	var d declaration.Declaration
	if err := dec.Decode(&d); err != nil {
		s.metrics.validationFailures.Add(1)
		s.problem(w, http.StatusBadRequest, "invalid_json", err.Error())
		return
	}
	if err := ensureEOF(dec); err != nil {
		s.metrics.validationFailures.Add(1)
		s.problem(w, http.StatusBadRequest, "invalid_json", err.Error())
		return
	}
	if err := declaration.Validate(d); err != nil {
		s.metrics.validationFailures.Add(1)
		s.problem(w, http.StatusUnprocessableEntity, "validation_failed", err.Error())
		return
	}
	s.writeJSON(w, http.StatusOK, map[string]any{"valid": true, "schemaVersion": d.SchemaVersion})
}

func (s *Server) handleCapabilities(w http.ResponseWriter, _ *http.Request) {
	s.writeJSON(w, http.StatusOK, map[string]any{"license": s.licenses.Status(), "supportedLanguages": languageCodes()})
}

func (s *Server) handleSchema(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "application/schema+json; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=3600")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	_, _ = w.Write([]byte(strings.ReplaceAll(declarationSchema, "__BASE_URL__", s.cfg.BaseURL)))
}

func (s *Server) handleContext(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "application/ld+json; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=3600")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	_, _ = w.Write([]byte(strings.ReplaceAll(jsonLDContext, "__BASE_URL__", s.cfg.BaseURL)))
}

func (s *Server) handleHealth(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_, _ = io.WriteString(w, "ok\n")
}
func (s *Server) handleReady(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_, _ = io.WriteString(w, "ready\n")
}

func (s *Server) renderHTML(w http.ResponseWriter, name string, data pageData) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	if err := s.templates.ExecuteTemplate(w, name, data); err != nil {
		s.logger.Error("template render failed", "template", name, "error", err)
	}
}

func (s *Server) language(r *http.Request) string {
	return i18n.Resolve(r.URL.Query().Get("lang"), r.Header.Get("Accept-Language"), s.cfg.DefaultLanguage)
}
func (s *Server) languageFromValues(r *http.Request, values url.Values) string {
	return i18n.Resolve(values.Get("lang"), r.Header.Get("Accept-Language"), s.cfg.DefaultLanguage)
}

func (s *Server) middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		started := time.Now()
		s.metrics.requests.Add(1)
		requestID := r.Header.Get("X-Request-ID")
		if requestID == "" {
			requestID = randomID()
		}
		w.Header().Set("X-Request-ID", requestID)
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=()")
		w.Header().Set("Cross-Origin-Resource-Policy", "cross-origin")
		if strings.HasPrefix(r.URL.Path, "/v1/") || strings.HasPrefix(r.URL.Path, "/schema/") || strings.HasPrefix(r.URL.Path, "/context/") {
			w.Header().Set("Access-Control-Allow-Origin", "*")
			w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
			if r.Method == http.MethodOptions {
				w.WriteHeader(http.StatusNoContent)
				return
			}
		}
		rw := &responseWriter{ResponseWriter: w, status: http.StatusOK}
		defer func() {
			if recovered := recover(); recovered != nil {
				s.metrics.panics.Add(1)
				s.logger.Error("handler panic", "request_id", requestID, "panic", recovered, "stack", string(debug.Stack()))
				http.Error(rw, "internal server error", http.StatusInternalServerError)
			}
			s.logger.Info("request", "request_id", requestID, "method", r.Method, "path", r.URL.Path, "status", rw.status, "bytes", rw.bytes, "duration_ms", time.Since(started).Milliseconds(), "remote", clientIP(r, s.cfg.TrustProxy))
		}()
		next.ServeHTTP(rw, r)
	})
}

func (s *Server) problem(w http.ResponseWriter, status int, code, detail string) {
	w.Header().Set("Content-Type", "application/problem+json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(map[string]any{"type": s.cfg.BaseURL + "/problems/" + code, "title": http.StatusText(status), "status": status, "code": code, "detail": detail})
}

func (s *Server) writeJSON(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

type responseWriter struct {
	http.ResponseWriter
	status, bytes int
}

func (w *responseWriter) WriteHeader(status int) {
	w.status = status
	w.ResponseWriter.WriteHeader(status)
}
func (w *responseWriter) Write(b []byte) (int, error) {
	n, err := w.ResponseWriter.Write(b)
	w.bytes += n
	return n, err
}

func cacheStatic(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "public, max-age=3600")
		next.ServeHTTP(w, r)
	})
}

func presetOptions(locale i18n.Locale) []option {
	ids := []string{"research", "no-ai", "summary", "full"}
	out := make([]option, 0, len(ids))
	for _, id := range ids {
		out = append(out, option{Value: id, Label: locale.Presets[id].Title})
	}
	return out
}

func orderedOptions(values map[string]string, order []string) []option {
	out := make([]option, 0, len(order))
	for _, key := range order {
		out = append(out, option{Value: key, Label: values[key]})
	}
	return out
}

func declarationFacts(d declaration.Declaration, locale i18n.Locale) []fact {
	facts := []fact{{Label: locale.Text["fact_assurance"], Value: locale.Assurances[d.Assurance]}}
	if d.Subject != "" {
		facts = append(facts, fact{Label: locale.Text["fact_subject"], Value: d.Subject, Link: d.Subject})
	}
	if d.EditorialResponsibility != nil && d.EditorialResponsibility.Name != "" {
		facts = append(facts, fact{Label: locale.Text["fact_responsibility"], Value: d.EditorialResponsibility.Name, Link: d.EditorialResponsibility.URL})
	}
	if d.DeclaredAt != "" {
		facts = append(facts, fact{Label: locale.Text["fact_declared_at"], Value: d.DeclaredAt})
	}
	return facts
}

func declarationComponentRows(d declaration.Declaration, locale i18n.Locale) []componentRow {
	order := []string{"text", "coverImage", "image", "research", "translation", "audio", "video", "code", "other"}
	rows := make([]componentRow, 0, len(d.Components))
	for _, name := range order {
		component, ok := d.Components[name]
		if !ok {
			continue
		}
		activities := make([]string, 0, len(component.Activities))
		for _, activity := range component.Activities {
			if translated := locale.Activities[activity]; translated != "" {
				activities = append(activities, translated)
			} else {
				activities = append(activities, activity)
			}
		}
		activityText := locale.Text["not_specified"]
		if component.AIExtent == "none" {
			activityText = locale.Text["not_applicable"]
		}
		if activityText == "" {
			activityText = locale.Text["none_value"]
		}
		if len(activities) > 0 {
			activityText = strings.Join(activities, ", ")
		}
		rows = append(rows, componentRow{Name: locale.Components[name], Extent: locale.Extents[component.AIExtent], Activities: activityText, Review: locale.Reviews[component.HumanReview], Note: component.Note})
	}
	return rows
}

func overallExtent(d declaration.Declaration) string {
	rank := map[string]int{"none": 0, "assisted": 1, "partial": 2, "mostly": 3, "full": 4}
	best, bestRank := "none", 0
	for _, c := range d.Components {
		if rank[c.AIExtent] > bestRank {
			best, bestRank = c.AIExtent, rank[c.AIExtent]
		}
	}
	return best
}

func articleShortDescription(d declaration.Declaration, locale i18n.Locale) string {
	rows := declarationComponentRows(d, locale)
	parts := make([]string, 0, len(rows))
	for _, row := range rows {
		parts = append(parts, row.Name+": "+row.Extent)
	}
	return strings.Join(parts, " · ")
}

func declarationSummary(d declaration.Declaration, locale i18n.Locale) []string {
	if len(d.Components) == 0 {
		return nil
	}
	intro := map[string]string{
		"de": "Diese Erklärung dokumentiert nachvollziehbar, in welchen Bereichen künstliche Intelligenz bei der Erstellung und Veröffentlichung des gekennzeichneten Inhalts eingesetzt wurde.",
		"en": "This declaration documents, in a transparent and traceable form, where artificial intelligence was used in creating and publishing the labelled content.",
		"fr": "Cette déclaration documente de manière transparente et traçable les domaines dans lesquels l’intelligence artificielle a été utilisée pour créer et publier le contenu identifié.",
		"es": "Esta declaración documenta de forma transparente y trazable en qué áreas se utilizó inteligencia artificial para crear y publicar el contenido identificado.",
		"it": "La presente dichiarazione documenta in modo trasparente e tracciabile gli ambiti in cui l’intelligenza artificiale è stata utilizzata per creare e pubblicare il contenuto indicato.",
		"nl": "Deze verklaring documenteert op transparante en navolgbare wijze op welke onderdelen kunstmatige intelligentie is gebruikt bij het maken en publiceren van de aangeduide inhoud.",
		"pt": "Esta declaração documenta, de forma transparente e rastreável, as áreas em que a inteligência artificial foi utilizada na criação e publicação do conteúdo identificado.",
		"pl": "Niniejsza deklaracja w przejrzysty i możliwy do prześledzenia sposób dokumentuje obszary, w których wykorzystano sztuczną inteligencję podczas tworzenia i publikacji oznaczonej treści.",
	}
	lang := locale.Code
	if intro[lang] == "" {
		lang = "en"
	}
	statements := []string{intro[lang]}
	for _, name := range []string{"text", "coverImage", "image", "research", "translation", "audio", "video", "code", "other"} {
		component, ok := d.Components[name]
		if !ok {
			continue
		}
		statements = append(statements, componentSummaryStatement(locale, name, component))
	}
	closing := map[string][]string{
		"de": {
			"Sämtliche Angaben werden unter einem gemeinsamen Link veröffentlicht und stehen zusätzlich als maschinenlesbares JSON-LD zur Verfügung.",
			"Die inhaltliche und redaktionelle Verantwortung verbleibt unabhängig vom ausgewiesenen KI-Anteil bei der veröffentlichenden Person oder Organisation.",
		},
		"en": {
			"All information is published under a single link and is also available as machine-readable JSON-LD.",
			"Responsibility for the content and its editorial publication remains with the publishing person or organisation, irrespective of the stated level of AI involvement.",
		},
		"fr": {
			"Toutes les informations sont publiées sous un lien unique et sont également disponibles au format JSON-LD lisible par machine.",
			"La responsabilité du contenu et de sa publication éditoriale demeure celle de la personne ou de l’organisation éditrice, indépendamment du niveau d’intervention de l’IA indiqué.",
		},
		"es": {
			"Toda la información se publica mediante un único enlace y también está disponible como JSON-LD legible por máquina.",
			"La responsabilidad sobre el contenido y su publicación editorial permanece en la persona u organización editora, con independencia del nivel de intervención de la IA indicado.",
		},
		"it": {
			"Tutte le informazioni sono pubblicate tramite un unico collegamento e sono disponibili anche come JSON-LD leggibile automaticamente.",
			"La responsabilità del contenuto e della sua pubblicazione editoriale resta in capo alla persona o all’organizzazione che lo pubblica, indipendentemente dal livello dichiarato di intervento dell’IA.",
		},
		"nl": {
			"Alle gegevens worden via één gezamenlijke link gepubliceerd en zijn daarnaast beschikbaar als machineleesbare JSON-LD.",
			"De inhoudelijke en redactionele verantwoordelijkheid blijft, ongeacht de vermelde mate van AI-gebruik, bij de publicerende persoon of organisatie.",
		},
		"pt": {
			"Todas as informações são publicadas através de uma única ligação e estão igualmente disponíveis como JSON-LD legível por máquina.",
			"A responsabilidade pelo conteúdo e pela sua publicação editorial permanece com a pessoa ou organização responsável pela publicação, independentemente do grau de utilização de IA indicado.",
		},
		"pl": {
			"Wszystkie informacje są publikowane pod jednym wspólnym odsyłaczem i są również dostępne jako maszynowo czytelny JSON-LD.",
			"Odpowiedzialność za treść i jej redakcyjną publikację pozostaje po stronie publikującej osoby lub organizacji, niezależnie od wskazanego zakresu użycia AI.",
		},
	}
	end := closing[lang]
	end = append(end, assuranceStatement(d.Assurance, locale))
	return []string{strings.Join(statements, " "), strings.Join(end, " ")}
}

func componentSummaryStatement(locale i18n.Locale, name string, component declaration.Component) string {
	componentName := locale.Components[name]
	if componentName == "" {
		componentName = name
	}
	extent := locale.Extents[component.AIExtent]
	activities := make([]string, 0, len(component.Activities))
	for _, activity := range component.Activities {
		if value := locale.Activities[activity]; value != "" {
			activities = append(activities, value)
		} else {
			activities = append(activities, activity)
		}
	}
	activityText := strings.Join(activities, ", ")
	review := locale.Reviews[component.HumanReview]

	switch locale.Code {
	case "de":
		if component.AIExtent == "none" {
			if component.HumanReview == "none" {
				return fmt.Sprintf("Für den Bereich „%s“ wurde nach den vorliegenden Angaben keine KI eingesetzt.", componentName)
			}
			return fmt.Sprintf("Für den Bereich „%s“ wurde nach den vorliegenden Angaben keine KI eingesetzt; ergänzend ist eine %s menschliche Prüfung dokumentiert.", componentName, germanReviewAdjective(component.HumanReview))
		}
		purpose := ""
		if activityText != "" {
			purpose = " für " + activityText
		}
		if component.HumanReview == "none" {
			return fmt.Sprintf("Für den Bereich „%s“ ist %s%s dokumentiert; eine menschliche Prüfung der KI-bezogenen Ergebnisse ist nicht angegeben.", componentName, germanExtentPhrase(component.AIExtent), purpose)
		}
		return fmt.Sprintf("Für den Bereich „%s“ ist %s%s dokumentiert; die KI-bezogenen Ergebnisse wurden %s geprüft.", componentName, germanExtentPhrase(component.AIExtent), purpose, germanReviewAdverb(component.HumanReview))
	case "en":
		if component.AIExtent == "none" {
			if component.HumanReview == "none" {
				return fmt.Sprintf("According to the information provided, no AI was used for “%s”.", componentName)
			}
			return fmt.Sprintf("According to the information provided, no AI was used for “%s”; a %s human review is nevertheless recorded.", componentName, strings.ToLower(review))
		}
		purpose := ""
		if activityText != "" {
			purpose = " for " + activityText
		}
		if component.HumanReview == "none" {
			return fmt.Sprintf("For “%s”, %s%s is recorded; no human review of the AI-related output is specified.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("For “%s”, %s%s is recorded; the AI-related output underwent %s human review.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	default:
		if component.AIExtent == "none" {
			return genericNoAIStatement(locale.Code, componentName, component.HumanReview, review)
		}
		return genericAIStatement(locale.Code, componentName, extent, activityText, component.HumanReview, review)
	}
}

func germanExtentPhrase(extent string) string {
	switch extent {
	case "assisted":
		return "eine KI-unterstützte Nutzung"
	case "partial":
		return "eine teilweise KI-generierte Erstellung"
	case "mostly":
		return "eine überwiegend KI-generierte Erstellung"
	case "full":
		return "eine vollständig KI-generierte Erstellung"
	default:
		return "eine KI-Nutzung"
	}
}

func germanReviewAdverb(review string) string {
	switch review {
	case "basic":
		return "grundlegend"
	case "editorial":
		return "redaktionell"
	case "expert":
		return "fachlich"
	default:
		return "menschlich"
	}
}

func germanReviewAdjective(review string) string {
	switch review {
	case "basic":
		return "grundlegende"
	case "editorial":
		return "redaktionelle"
	case "expert":
		return "fachliche"
	default:
		return "menschliche"
	}
}

func genericNoAIStatement(lang, componentName, reviewCode, review string) string {
	withReview := reviewCode != "none"
	switch lang {
	case "fr":
		if withReview {
			return fmt.Sprintf("Selon les informations fournies, aucune IA n’a été utilisée pour « %s » ; une vérification humaine %s est néanmoins documentée.", componentName, strings.ToLower(review))
		}
		return fmt.Sprintf("Selon les informations fournies, aucune IA n’a été utilisée pour « %s ».", componentName)
	case "es":
		if withReview {
			return fmt.Sprintf("Según la información proporcionada, no se utilizó IA en «%s»; no obstante, se documenta una revisión humana %s.", componentName, strings.ToLower(review))
		}
		return fmt.Sprintf("Según la información proporcionada, no se utilizó IA en «%s».", componentName)
	case "it":
		if withReview {
			return fmt.Sprintf("Secondo le informazioni fornite, per «%s» non è stata utilizzata l’IA; è comunque documentata una revisione umana %s.", componentName, strings.ToLower(review))
		}
		return fmt.Sprintf("Secondo le informazioni fornite, per «%s» non è stata utilizzata l’IA.", componentName)
	case "nl":
		if withReview {
			return fmt.Sprintf("Volgens de verstrekte informatie is voor ‘%s’ geen AI gebruikt; er is wel een %s menselijke controle vastgelegd.", componentName, strings.ToLower(review))
		}
		return fmt.Sprintf("Volgens de verstrekte informatie is voor ‘%s’ geen AI gebruikt.", componentName)
	case "pt":
		if withReview {
			return fmt.Sprintf("De acordo com as informações fornecidas, não foi utilizada IA em «%s»; está, ainda assim, documentada uma revisão humana %s.", componentName, strings.ToLower(review))
		}
		return fmt.Sprintf("De acordo com as informações fornecidas, não foi utilizada IA em «%s».", componentName)
	case "pl":
		if withReview {
			return fmt.Sprintf("Zgodnie z podanymi informacjami w obszarze „%s” nie użyto AI; udokumentowano jednak weryfikację człowieka na poziomie %s.", componentName, review)
		}
		return fmt.Sprintf("Zgodnie z podanymi informacjami w obszarze „%s” nie użyto AI.", componentName)
	default:
		return fmt.Sprintf("According to the information provided, no AI was used for “%s”.", componentName)
	}
}

func genericAIStatement(lang, componentName, extent, activities string, reviewCode, review string) string {
	purpose := activities
	if purpose == "" {
		purpose = "—"
	}
	switch lang {
	case "fr":
		if reviewCode == "none" {
			return fmt.Sprintf("Pour « %s », l’utilisation déclarée est %s, avec pour finalité %s ; aucune vérification humaine des résultats liés à l’IA n’est indiquée.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("Pour « %s », l’utilisation déclarée est %s, avec pour finalité %s ; les résultats liés à l’IA ont fait l’objet d’une vérification humaine %s.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	case "es":
		if reviewCode == "none" {
			return fmt.Sprintf("Para «%s» se declara %s, con la finalidad %s; no se indica una revisión humana de los resultados relacionados con la IA.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("Para «%s» se declara %s, con la finalidad %s; los resultados relacionados con la IA fueron objeto de una revisión humana %s.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	case "it":
		if reviewCode == "none" {
			return fmt.Sprintf("Per «%s» è dichiarato %s, con finalità %s; non è indicata una revisione umana dei risultati legati all’IA.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("Per «%s» è dichiarato %s, con finalità %s; i risultati legati all’IA sono stati sottoposti a revisione umana %s.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	case "nl":
		if reviewCode == "none" {
			return fmt.Sprintf("Voor ‘%s’ is %s vastgelegd, met als doel %s; er is geen menselijke controle van de AI-gerelateerde resultaten aangegeven.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("Voor ‘%s’ is %s vastgelegd, met als doel %s; de AI-gerelateerde resultaten hebben een %s menselijke controle ondergaan.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	case "pt":
		if reviewCode == "none" {
			return fmt.Sprintf("Para «%s» está documentado %s, com a finalidade %s; não é indicada uma revisão humana dos resultados relacionados com IA.", componentName, strings.ToLower(extent), purpose)
		}
		return fmt.Sprintf("Para «%s» está documentado %s, com a finalidade %s; os resultados relacionados com IA foram sujeitos a uma revisão humana %s.", componentName, strings.ToLower(extent), purpose, strings.ToLower(review))
	case "pl":
		if reviewCode == "none" {
			return fmt.Sprintf("Dla obszaru „%s” udokumentowano %s w celu %s; nie wskazano weryfikacji człowieka dla wyników związanych z AI.", componentName, extent, purpose)
		}
		return fmt.Sprintf("Dla obszaru „%s” udokumentowano %s w celu %s; wyniki związane z AI poddano weryfikacji człowieka na poziomie %s.", componentName, extent, purpose, review)
	default:
		return fmt.Sprintf("For “%s”, %s is recorded.", componentName, strings.ToLower(extent))
	}
}

func assuranceStatement(assurance string, locale i18n.Locale) string {
	key := "assurance_" + assurance + "_statement"
	if value := locale.Text[key]; value != "" {
		if assurance == "signed" {
			switch locale.Code {
			case "de":
				return value + " Die Signatur bestätigt nicht automatisch die inhaltliche Richtigkeit der Angaben."
			case "en":
				return value + " The signature does not by itself confirm the substantive accuracy of the information."
			}
		}
		return value
	}
	if value := locale.Text["assurance_"+assurance+"_description"]; value != "" {
		return value
	}
	return locale.Assurances[assurance]
}

func customTextRequested(q url.Values, keys ...string) bool {
	for _, key := range keys {
		if strings.TrimSpace(q.Get(key)) != "" {
			return true
		}
	}
	return false
}
func firstNonEmpty(values ...string) string {
	for _, value := range values {
		if value = strings.TrimSpace(value); value != "" {
			return value
		}
	}
	return ""
}
func validHexColor(value string) bool {
	if len(value) != 7 || value[0] != '#' {
		return false
	}
	for _, r := range value[1:] {
		if !((r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')) {
			return false
		}
	}
	return true
}
func languageCodes() []string {
	languages := i18n.Languages()
	out := make([]string, 0, len(languages))
	for _, l := range languages {
		out = append(out, l.Code)
	}
	sort.Strings(out)
	return out
}
func cloneValues(in url.Values) url.Values {
	out := url.Values{}
	for k, v := range in {
		out[k] = append([]string(nil), v...)
	}
	return out
}
func randomID() string {
	b := make([]byte, 8)
	if _, err := rand.Read(b); err != nil {
		return fmt.Sprintf("%d", time.Now().UnixNano())
	}
	return hex.EncodeToString(b)
}
func clientIP(r *http.Request, trustProxy bool) string {
	if trustProxy {
		if x := strings.TrimSpace(strings.Split(r.Header.Get("X-Forwarded-For"), ",")[0]); x != "" {
			return x
		}
	}
	return r.RemoteAddr
}
func ensureEOF(dec *json.Decoder) error {
	var extra any
	err := dec.Decode(&extra)
	if errors.Is(err, io.EOF) {
		return nil
	}
	if err == nil {
		return errors.New("request body must contain exactly one JSON value")
	}
	return err
}

const declarationSchema = `{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "__BASE_URL__/schema/v1/declaration.schema.json",
  "title": "AI Usage Declaration",
  "type": "object",
  "additionalProperties": false,
  "required": ["@context", "@type", "schemaVersion", "language", "components", "assurance"],
  "properties": {
    "@context": {"type": "string"},
    "@type": {"const": "AIUsageDeclaration"},
    "schemaVersion": {"const": "1.1"},
    "subject": {"type": "string", "format": "uri"},
    "declaredAt": {"type": "string", "format": "date-time"},
    "language": {"enum": ["de", "en", "fr", "es", "it", "nl", "pt", "pl"]},
    "assurance": {"enum": ["selfDeclared", "technicallyRecorded", "signed", "verified"]},
    "editorialResponsibility": {
      "type": "object", "additionalProperties": false,
      "properties": {"name": {"type": "string"}, "url": {"type": "string", "format": "uri"}}
    },
    "presentation": {
      "type": "object", "additionalProperties": false,
      "properties": {
        "title": {"type": "string", "maxLength": 120},
        "description": {"type": "string", "maxLength": 500},
        "badgeLabel": {"type": "string", "maxLength": 40},
        "badgeMessage": {"type": "string", "maxLength": 80},
        "leftColor": {"type": "string", "pattern": "^#[0-9A-Fa-f]{6}$"},
        "rightColor": {"type": "string", "pattern": "^#[0-9A-Fa-f]{6}$"}
      }
    },
    "components": {"type": "object", "minProperties": 1, "additionalProperties": {"$ref": "#/$defs/component"}}
  },
  "$defs": {
    "component": {
      "type": "object", "additionalProperties": false,
      "required": ["aiExtent", "humanReview"],
      "properties": {
        "aiExtent": {"enum": ["none", "assisted", "partial", "mostly", "full"]},
        "activities": {"type": "array", "uniqueItems": true, "items": {"enum": ["research", "summarisation", "drafting", "generation", "translation", "editing", "imageGeneration", "codeGeneration", "transcription", "classification"]}},
        "humanReview": {"enum": ["none", "basic", "editorial", "expert"]},
        "note": {"type": "string", "maxLength": 500}
      }
    }
  }
}`

const jsonLDContext = `{
  "@context": {
    "@version": 1.1,
    "AIUsageDeclaration": "__BASE_URL__/vocab/AIUsageDeclaration",
    "schemaVersion": "__BASE_URL__/vocab/schemaVersion",
    "subject": {"@id": "https://schema.org/about", "@type": "@id"},
    "declaredAt": {"@id": "https://schema.org/dateCreated", "@type": "https://www.w3.org/2001/XMLSchema#dateTime"},
    "language": "https://schema.org/inLanguage",
    "components": "__BASE_URL__/vocab/components",
    "aiExtent": "__BASE_URL__/vocab/aiExtent",
    "activities": "__BASE_URL__/vocab/activities",
    "humanReview": "__BASE_URL__/vocab/humanReview",
    "assurance": "__BASE_URL__/vocab/assurance",
    "presentation": "__BASE_URL__/vocab/presentation",
    "editorialResponsibility": "https://schema.org/accountablePerson"
  }
}`