package classes

import (
	"context"
	"errors"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"git.golem15.com/golem15/sm-seo-plugin/models"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// The page registry (D-33): the site's own frontend pages (home, contact,
// offer pages) as a signpost content type of the SEO plugin, so each page
// gets the SEO tab, resolves ok and is listed in the sitemaps.
const (
	// PageTypeKey is the registry's menu item type.
	PageTypeKey = "seo-page"
	// PagesController is the Pages screen's admin controller.
	PagesController = "golem15.seo.pages"
	// PagePattern is the registry type's pattern. A registry page stores
	// its own address per locale, so the pattern only satisfies signpost.
	PagePattern = "/:page"
	// PageLabel is the registry type's label (a content type's label names
	// its tab in the SEO settings, so it is not the plain "Page" another
	// content type may use).
	PageLabel = "golem15.seo::lang.pages.type"
)

// PageModel is the registry page's morph type, the model its SEO entries
// and record events name.
var PageModel = models.Page{}.MorphName()

// The route report's limits (P33-20).
const (
	MaxReportedRoutes = 2000
	MaxRouteBytes     = 2048
)

// RouteReportTokenConfigKey is the bearer token the frontend server sends
// with its route report to POST /_seo/api/v1/registry/routes (P33-20).
// Empty uses golem15.seo.notfound_token; both empty turn the report off.
const RouteReportTokenConfigKey = "golem15.seo.route_report_token"

// RouteReportToken is the route report's token: route_report_token, else
// notfound_token, "" when neither is set.
func (s *Service) RouteReportToken() string {
	if cfg := s.Config(); cfg != nil {
		if t := strings.TrimSpace(cfg.String(RouteReportTokenConfigKey)); t != "" {
			return t
		}
	}
	return s.NotFoundToken()
}

// PageOrigin is the origin of a page created through the management API:
// mcp through MCP, else manual.
func PageOrigin(ctx context.Context) string {
	if ViaOf(ctx) == models.ViaMCP {
		return models.PageOriginMCP
	}
	return models.PageOriginManual
}

// ErrTooManyRoutes refuses a route report of more than MaxReportedRoutes
// paths.
var ErrTooManyRoutes = errors.New("golem15.seo: a route report holds at most 2000 paths")

// The phrase keys of the registry refusals (UI-SPEC C21).
const (
	errPageURLRequired = "golem15.seo::lang.pages.url_required"
	errPageURLInvalid  = "golem15.seo::lang.pages.url_invalid"
	errPageURLTaken    = "golem15.seo::lang.pages.url_taken"
	errPageURLOwned    = "golem15.seo::lang.pages.url_owned"
	errPageParentLoop  = "golem15.seo::lang.pages.parent_loop"
	errValueInvalid    = "golem15.seo::lang.api.value_invalid"
)

// pageGroups are the sitemap file groups of the page kinds (P33-18).
var pageGroups = map[string]string{
	models.PageKindPage:    "pages",
	models.PageKindOffer:   "offers",
	models.PageKindService: "services",
	models.PageKindLanding: "landing-pages",
}

// PageKindLabels are the phrase keys of the page kinds.
var PageKindLabels = map[string]string{
	models.PageKindPage:    "golem15.seo::lang.pages.kind_page",
	models.PageKindOffer:   "golem15.seo::lang.pages.kind_offer",
	models.PageKindService: "golem15.seo::lang.pages.kind_service",
	models.PageKindLanding: "golem15.seo::lang.pages.kind_landing",
}

// PageGroup is the sitemap file group of a page kind; an unknown kind is
// listed with the pages.
func PageGroup(kind string) string {
	if g, ok := pageGroups[kind]; ok {
		return g
	}
	return pageGroups[models.PageKindPage]
}

// LoadPage returns registry page id; ErrNoRecord when there is none.
func LoadPage(db *gorm.DB, id uint) (models.Page, error) {
	var rows []models.Page
	if err := db.Where("id = ?", id).Limit(1).Find(&rows).Error; err != nil {
		return models.Page{}, err
	}
	if len(rows) == 0 {
		return models.Page{}, ErrNoRecord
	}
	return rows[0], nil
}

// pageByID reads a registry page by its id as text, nil when none.
func pageByID(db *gorm.DB, id string) (*models.Page, error) {
	n, err := strconv.ParseUint(strings.TrimSpace(id), 10, 64)
	if err != nil || n == 0 {
		return nil, nil
	}
	p, err := LoadPage(db, uint(n))
	if errors.Is(err, ErrNoRecord) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	return &p, nil
}

// PageAt returns the registry page whose address in any locale is path,
// with that locale; nil when none.
func (s *Service) PageAt(ctx context.Context, db *gorm.DB, path string) (*models.Page, string, error) {
	var rows []models.Page
	if err := db.Where("url = ?", path).Limit(1).Find(&rows).Error; err != nil {
		return nil, "", err
	}
	if len(rows) > 0 {
		return &rows[0], s.DefaultLocale(ctx, db), nil
	}
	var hit []struct {
		ID     uint   `gorm:"column:id"`
		Locale string `gorm:"column:locale"`
	}
	if err := db.Raw(`SELECT p.id, e.key AS locale FROM golem15_seo_pages p, jsonb_each_text(p.urls) e WHERE e.value = ? ORDER BY p.id LIMIT 1`, path).Scan(&hit).Error; err != nil {
		return nil, "", err
	}
	if len(hit) == 0 {
		return nil, "", nil
	}
	p, err := LoadPage(db, hit[0].ID)
	if err != nil {
		return nil, "", err
	}
	if def := s.DefaultLocale(ctx, db); hit[0].Locale == def {
		return nil, "", nil
	}
	return &p, hit[0].Locale, nil
}

// PageRecord describes a registry page as a signpost content record: its
// address and name per locale (the default locale first, then the other
// enabled locales with an address), its content date as lastmod and its
// parent page.
func (s *Service) PageRecord(ctx context.Context, db *gorm.DB, p models.Page) pact.ContentRecord {
	def := s.DefaultLocale(ctx, db)
	urls := p.LocaleURLs(def)
	rec := pact.ContentRecord{ID: p.IDText(), Published: true, LastMod: p.UpdatedAt}
	if p.ContentUpdatedAt != nil && !p.ContentUpdatedAt.IsZero() {
		day := p.ContentUpdatedAt.Time(time.UTC)
		rec.LastMod = &day
	}
	for _, locale := range s.pageLocales(ctx, db, urls) {
		rec.Locales = append(rec.Locales, pact.ContentLocale{Locale: locale, URL: urls[locale], Title: p.TitleIn(locale)})
	}
	if p.ParentID != nil && *p.ParentID != 0 {
		rec.Parents = []pact.ContentRef{{Type: PageTypeKey, ID: strconv.FormatUint(uint64(*p.ParentID), 10)}}
	}
	return rec
}

// pageLocales orders the locales of urls: the site's locales first (the
// default one leading), then any other stored locale by code.
func (s *Service) pageLocales(ctx context.Context, db *gorm.DB, urls map[string]string) []string {
	var out []string
	seen := map[string]bool{}
	for _, l := range s.Locales(ctx, db) {
		if urls[l] != "" && !seen[l] {
			out = append(out, l)
			seen[l] = true
		}
	}
	var rest []string
	for l := range urls {
		if !seen[l] {
			rest = append(rest, l)
		}
	}
	sort.Strings(rest)
	return append(out, rest...)
}

// PageMenuItemType is the registry's menu item type seo-page: a menu item
// may point at a registry page, and its content descriptor lists, describes
// and matches the pages for signpost's consumers (the SEO tab, the
// resolver, the sitemaps). service is asked on every call.
func PageMenuItemType(service func() *Service) pact.MenuItemType {
	svc := func() (*Service, error) {
		if service == nil {
			return nil, ErrNotBooted
		}
		s := service()
		if s == nil {
			return nil, ErrNotBooted
		}
		return s, nil
	}
	return pact.MenuItemType{
		Key:            PageTypeKey,
		Label:          PageLabel,
		DefaultPattern: PagePattern,
		References: func(ctx context.Context) ([]pact.MenuItemReference, error) {
			s, err := svc()
			if err != nil {
				return nil, err
			}
			return s.pageReferences(ctx)
		},
		Resolve: func(ctx context.Context, in pact.MenuItemResolve) (*pact.ResolvedMenuItem, error) {
			s, err := svc()
			if err != nil {
				return nil, err
			}
			return s.resolvePageItem(ctx, in.Reference)
		},
		Content: &pact.ContentDescriptor{
			Controller: PagesController,
			Model:      PageModel,
			Kind:       pact.ContentKindPage,
			Records: func(ctx context.Context, in pact.ContentList) (pact.ContentPage, error) {
				s, err := svc()
				if err != nil {
					return pact.ContentPage{}, err
				}
				return s.pageRecords(ctx, in)
			},
			Describe: func(ctx context.Context, in pact.ContentDescribe) (*pact.ContentRecord, error) {
				s, err := svc()
				if err != nil {
					return nil, err
				}
				db, err := s.DB(ctx)
				if err != nil {
					return nil, err
				}
				p, err := pageByID(db, in.ID)
				if err != nil || p == nil {
					return nil, err
				}
				rec := s.PageRecord(ctx, db, *p)
				return &rec, nil
			},
			Match: func(ctx context.Context, in pact.ContentMatch) (*pact.ContentMatchResult, error) {
				s, err := svc()
				if err != nil {
					return nil, err
				}
				db, err := s.DB(ctx)
				if err != nil {
					return nil, err
				}
				p, locale, err := s.PageAt(ctx, db, in.Path)
				if err != nil || p == nil {
					return nil, err
				}
				return &pact.ContentMatchResult{ID: p.IDText(), Locale: locale, Exact: true}, nil
			},
		},
	}
}

// pageRecords is one page of registry records by id.
func (s *Service) pageRecords(ctx context.Context, in pact.ContentList) (pact.ContentPage, error) {
	db, err := s.DB(ctx)
	if err != nil {
		return pact.ContentPage{}, err
	}
	limit := in.Limit
	if limit <= 0 || limit > 1000 {
		limit = 1000
	}
	after, _ := strconv.ParseUint(strings.TrimSpace(in.After), 10, 64)
	var rows []models.Page
	if err := db.Where("id > ? AND url <> ''", after).Order("id ASC").Limit(limit).Find(&rows).Error; err != nil {
		return pact.ContentPage{}, err
	}
	out := pact.ContentPage{}
	for _, p := range rows {
		out.Records = append(out.Records, s.PageRecord(ctx, db, p))
	}
	if len(rows) == limit {
		out.Next = rows[len(rows)-1].IDText()
	}
	return out, nil
}

// pageReferences lists the registry pages a menu item can point at, as a
// tree by parent, each level by address.
func (s *Service) pageReferences(ctx context.Context) ([]pact.MenuItemReference, error) {
	db, err := s.DB(ctx)
	if err != nil {
		return nil, err
	}
	var rows []models.Page
	if err := db.Where("url <> ''").Order("url ASC").Limit(5000).Find(&rows).Error; err != nil {
		return nil, err
	}
	children := map[uint][]models.Page{}
	known := map[uint]bool{}
	for _, p := range rows {
		known[p.ID] = true
	}
	for _, p := range rows {
		parent := p.Parent()
		if !known[parent] {
			parent = 0
		}
		children[parent] = append(children[parent], p)
	}
	visited := map[uint]bool{}
	var build func(parent uint, depth int) []pact.MenuItemReference
	build = func(parent uint, depth int) []pact.MenuItemReference {
		var out []pact.MenuItemReference
		for _, p := range children[parent] {
			if visited[p.ID] || depth > 50 {
				continue
			}
			visited[p.ID] = true
			label := p.Title
			if strings.TrimSpace(label) == "" {
				label = p.URL
			}
			out = append(out, pact.MenuItemReference{Value: p.IDText(), Label: label, Items: build(p.ID, depth+1)})
		}
		return out
	}
	return build(0, 0), nil
}

// resolvePageItem resolves a menu item pointing at registry page id: its
// default-locale address and name, and one alternate per locale.
func (s *Service) resolvePageItem(ctx context.Context, id string) (*pact.ResolvedMenuItem, error) {
	db, err := s.DB(ctx)
	if err != nil {
		return nil, err
	}
	p, err := pageByID(db, id)
	if err != nil || p == nil {
		return nil, err
	}
	rec := s.PageRecord(ctx, db, *p)
	item := &pact.ResolvedMenuItem{Title: p.Title, URL: p.URL, MTime: rec.LastMod}
	for _, l := range rec.Locales {
		item.Alternates = append(item.Alternates, pact.MenuItemAlternate{Locale: l.Locale, URL: l.URL, Title: l.Title})
	}
	return item, nil
}

// PageWrite is one change of a registry page through the API or MCP: a
// nil field is left as it is. URL and Title map locales to text; a locale
// sent empty removes that locale's address or name, and the "" key stands
// for the default locale. ParentSet with a nil ParentID moves the page to
// the top level.
type PageWrite struct {
	URL              map[string]string
	Title            map[string]string
	Kind             *string
	ParentSet        bool
	ParentID         *uint
	ContentUpdatedAt *string
	Note             *string
}

// ApplyPageTexts merges submitted addresses and names into p: def is the
// default locale, whose values go to the url and title columns. Every
// address is trimmed and normalised with the site's address rules, so it
// is stored in the form the resolver matches.
func (s *Service) ApplyPageTexts(ctx context.Context, db *gorm.DB, p *models.Page, urls, titles map[string]string) error {
	def := s.DefaultLocale(ctx, db)
	settings, err := LoadSettings(db)
	if err != nil {
		return err
	}
	opts := NormalizeOptionsOf(settings)
	if urls != nil {
		others := map[string]string{}
		for l, v := range p.URLs.Get() {
			others[l] = v
		}
		for locale, path := range urls {
			if locale == "" {
				locale = def
			}
			path = normalPagePath(path, opts)
			if locale == def {
				p.URL = path
				continue
			}
			if path == "" {
				delete(others, locale)
			} else {
				others[locale] = path
			}
		}
		p.URLs = lagoon.Jsonable[map[string]string]{Data: others, Valid: true}
	}
	if titles != nil {
		others := map[string]string{}
		for l, v := range p.Titles.Get() {
			others[l] = v
		}
		for locale, title := range titles {
			title = strings.TrimSpace(title)
			if locale == "" {
				locale = def
			}
			if locale == def {
				p.Title = title
				continue
			}
			if title == "" {
				delete(others, locale)
			} else {
				others[locale] = title
			}
		}
		p.Titles = lagoon.Jsonable[map[string]string]{Data: others, Valid: true}
	}
	if !p.URLs.Valid {
		p.URLs = lagoon.Jsonable[map[string]string]{Data: map[string]string{}, Valid: true}
	}
	if !p.Titles.Valid {
		p.Titles = lagoon.Jsonable[map[string]string]{Data: map[string]string{}, Valid: true}
	}
	return nil
}

// normalPagePath trims an address and, when it is a valid path, applies
// the site's address rules (lowercase, trailing slash) to it.
func normalPagePath(path string, opts NormalizeOptions) string {
	path = strings.TrimSpace(path)
	if !ValidPagePath(path) {
		return path
	}
	norm, _ := Normalize(&url.URL{Path: path}, opts)
	if norm.Path == "" {
		return path
	}
	return norm.Path
}

// ValidPagePath reports whether path is a registry address: a path
// starting with a single "/", without a domain, query or fragment, of at
// most MaxRouteBytes bytes of valid UTF-8 without control characters.
func ValidPagePath(path string) bool {
	if path == "" || len(path) > MaxRouteBytes || !strings.HasPrefix(path, "/") || strings.HasPrefix(path, "//") {
		return false
	}
	if !utf8.ValidString(path) || strings.ContainsAny(path, "?#\\ ") {
		return false
	}
	for _, r := range path {
		if unicode.IsControl(r) {
			return false
		}
	}
	u, err := url.Parse(path)
	return err == nil && !u.IsAbs() && u.Host == ""
}

// ApplyPageFields sets the scalar fields of w on p; an invalid kind or
// date is a problem.
func ApplyPageFields(p *models.Page, w PageWrite) map[string][]models.Problem {
	problems := map[string][]models.Problem{}
	if w.Kind != nil {
		p.Kind = strings.TrimSpace(*w.Kind)
	}
	if w.ParentSet {
		p.ParentID = nil
		if w.ParentID != nil && *w.ParentID != 0 {
			ref := models.PageRef(*w.ParentID)
			p.ParentID = &ref
		}
	}
	if w.ContentUpdatedAt != nil {
		v := strings.TrimSpace(*w.ContentUpdatedAt)
		if v == "" {
			p.ContentUpdatedAt = nil
		} else if d, err := lagoon.ParseDate(v); err == nil {
			p.ContentUpdatedAt = &d
		} else {
			problems["content_updated_at"] = append(problems["content_updated_at"], models.Problem{Key: errValueInvalid})
		}
	}
	if w.Note != nil {
		p.Note = strings.TrimSpace(*w.Note)
	}
	return problems
}

// CheckPage lists the refusals of a registry page before a save (UI-SPEC
// C21), keyed by field (url, kind, parent_id): a missing default-locale
// address, an invalid address, an address another registry page uses, an
// address another content type owns (naming the type and the record), an
// unknown kind, and a parent that is unknown or would make a loop.
func (s *Service) CheckPage(ctx context.Context, db *gorm.DB, p models.Page) (map[string][]models.Problem, error) {
	problems := map[string][]models.Problem{}
	add := func(field string, pr models.Problem) {
		for _, have := range problems[field] {
			if have.Key == pr.Key {
				return
			}
		}
		problems[field] = append(problems[field], pr)
	}
	if !models.KnownPageKind(p.Kind) {
		add("kind", models.Problem{Key: errValueInvalid})
	}
	def := s.DefaultLocale(ctx, db)
	if strings.TrimSpace(p.URL) == "" {
		add("url", models.Problem{Key: errPageURLRequired})
	}
	urls := p.LocaleURLs(def)
	var paths []string
	for _, locale := range s.pageLocales(ctx, db, urls) {
		path := urls[locale]
		if !ValidPagePath(path) {
			add("url", models.Problem{Key: errPageURLInvalid})
			continue
		}
		paths = append(paths, path)
	}
	if len(paths) > 0 {
		var taken int64
		q := db.Model(&models.Page{}).Where(`(url IN ? OR EXISTS (SELECT 1 FROM jsonb_each_text(golem15_seo_pages.urls) e WHERE e.value IN ?))`, paths, paths)
		if p.ID != 0 {
			q = q.Where("id <> ?", p.ID)
		}
		if err := q.Count(&taken).Error; err != nil {
			return nil, err
		}
		if taken > 0 {
			add("url", models.Problem{Key: errPageURLTaken})
		}
		for _, path := range paths {
			owner, err := s.ownerOutsideRegistry(ctx, path)
			if err != nil {
				return nil, err
			}
			if owner != nil {
				add("url", *owner)
				break
			}
		}
	}
	if parent := p.Parent(); parent != 0 {
		loop, known, err := parentLoop(db, p.ID, parent)
		if err != nil {
			return nil, err
		}
		switch {
		case !known:
			add("parent_id", models.Problem{Key: errValueInvalid})
		case loop:
			add("parent_id", models.Problem{Key: errPageParentLoop})
		}
	}
	return problems, nil
}

// parentLoop walks up from parent: loop is true when it reaches id (or
// goes round), known false when parent does not exist.
func parentLoop(db *gorm.DB, id, parent uint) (loop, known bool, err error) {
	seen := map[uint]bool{}
	cur := parent
	for depth := 0; cur != 0; depth++ {
		if (id != 0 && cur == id) || seen[cur] || depth > 100 {
			return true, true, nil
		}
		seen[cur] = true
		p, err := LoadPage(db, cur)
		if errors.Is(err, ErrNoRecord) {
			return false, depth > 0, nil
		}
		if err != nil {
			return false, false, err
		}
		if p.Parent() == 0 {
			return false, true, nil
		}
		cur = p.Parent()
	}
	return false, true, nil
}

// ownerOutsideRegistry returns the url_owned refusal when a content type
// other than the registry owns path exactly: the type's label and the
// record's title as params. nil when none does.
func (s *Service) ownerOutsideRegistry(ctx context.Context, path string) (*models.Problem, error) {
	reg := s.Registry()
	if reg == nil {
		return nil, nil
	}
	unprefixed := s.UnprefixedLocale()
	for _, typ := range reg.ContentTypes() {
		if typ.Key == PageTypeKey || typ.Content == nil || typ.Content.Match == nil {
			continue
		}
		got, err := typ.Content.Match(ctx, pact.ContentMatch{Path: trimSlash(path), Pattern: reg.Pattern(typ.Key, ""), UnprefixedLocale: unprefixed})
		if err != nil {
			return nil, err
		}
		if got == nil || !got.Exact {
			continue
		}
		title := path
		if rec, err := reg.Describe(ctx, typ.Key, got.ID, unprefixed); err == nil && rec != nil {
			if l := contentLocale(rec, got.Locale); strings.TrimSpace(l.Title) != "" {
				title = l.Title
			}
		}
		label := typ.Label
		if strings.TrimSpace(label) == "" {
			label = typ.Key
		}
		return &models.Problem{Key: errPageURLOwned, Params: map[string]string{"type": s.Phrase(label, nil), "title": title}}, nil
	}
	return nil, nil
}

// PageValues are a registry page's values for history.
func PageValues(p models.Page) map[string]any {
	parent := any(nil)
	if p.Parent() != 0 {
		parent = p.Parent()
	}
	date := ""
	if p.ContentUpdatedAt != nil {
		date = p.ContentUpdatedAt.String()
	}
	return map[string]any{
		"url": p.URL, "urls": plainValue(p.URLs.Get()), "title": p.Title, "titles": plainValue(p.Titles.Get()),
		"kind": p.Kind, "origin": p.Origin, "parent_id": parent, "content_updated_at": date, "note": p.Note,
	}
}

// pageWhat is a registry page's history description.
func (s *Service) pageWhat(p models.Page) string {
	return s.Phrase("golem15.seo::lang.history.what_page", map[string]string{"url": p.URL})
}

// RecordPage records a registry page's change in history.
func (s *Service) RecordPage(ctx context.Context, tx *gorm.DB, before map[string]any, p models.Page, deleted bool) error {
	c := Change{Kind: models.SubjectPage, SubjectID: p.IDText(), What: s.pageWhat(p), Before: before}
	if !deleted {
		c.After = PageValues(p)
	}
	return s.Record(ctx, tx, c)
}

// SavePage checks and writes a registry page inside tx, records it in
// history, and fires the record event after commit, so the SEO tab's
// address tracking and the sitemap follow as they do for an admin save.
func (s *Service) SavePage(ctx context.Context, tx *gorm.DB, p *models.Page, before map[string]any) error {
	problems, err := s.CheckPage(ctx, tx, *p)
	if err != nil {
		return err
	}
	if len(problems) > 0 {
		return &ProblemsError{Problems: problems}
	}
	now := time.Now().UTC()
	created := p.ID == 0
	if created {
		p.CreatedAt = &now
	}
	p.UpdatedAt = &now
	if err := tx.Save(p).Error; err != nil {
		return err
	}
	if err := s.RecordPage(ctx, tx, before, *p, false); err != nil {
		return err
	}
	cabana.EmitRecordSaved(ctx, s.app, tx, pact.RecordSaved{Controller: PagesController, Model: PageModel, ID: p.IDText(), Created: created})
	return nil
}

// DeletePage deletes a registry page inside tx, records it in history and
// fires the record event after commit: the SEO plugin then deletes the
// page's SEO entries and the sitemap drops its addresses.
func (s *Service) DeletePage(ctx context.Context, tx *gorm.DB, p models.Page) error {
	if err := tx.Delete(&models.Page{}, p.ID).Error; err != nil {
		return err
	}
	if err := s.RecordPage(ctx, tx, PageValues(p), p, true); err != nil {
		return err
	}
	cabana.EmitRecordDeleted(ctx, s.app, tx, pact.RecordDeleted{Controller: PagesController, Model: PageModel, ID: p.IDText()})
	return nil
}

// RouteReport is the outcome of a route report: the paths inserted as new
// registry pages, the known pages whose reported_at moved, and the paths
// skipped (invalid, or owned by another content type).
type RouteReport struct {
	Inserted   int       `json:"inserted"`
	Updated    int       `json:"updated"`
	Skipped    int       `json:"skipped"`
	ReportedAt time.Time `json:"reported_at"`
}

// ReportRoutes takes the frontend server's static routes (D-33, P33-20)
// inside tx: a path no registry page has is inserted with origin reported,
// kind page and a name from its last segment; a known page gets
// reported_at; a path another content type owns, or that is no valid
// address, is skipped. Nothing is ever deleted, and no value an editor set
// is overwritten. The settings' routes_reported_at becomes the report's
// time, so a reported page missing from it shows as missing. More than
// MaxReportedRoutes paths is ErrTooManyRoutes.
func (s *Service) ReportRoutes(ctx context.Context, tx *gorm.DB, paths []string) (RouteReport, error) {
	now := time.Now().UTC()
	out := RouteReport{ReportedAt: now}
	if len(paths) > MaxReportedRoutes {
		return out, ErrTooManyRoutes
	}
	settings, err := SettingsRow(tx)
	if err != nil {
		return out, err
	}
	opts := NormalizeOptionsOf(settings)
	ctx = WithVia(ctx, models.ViaAuto)
	seen := map[string]bool{}
	for _, raw := range paths {
		path := strings.TrimSpace(raw)
		if len(path) > MaxRouteBytes || !ValidPagePath(path) {
			out.Skipped++
			continue
		}
		path = normalPagePath(path, opts)
		if seen[path] {
			continue
		}
		seen[path] = true
		page, _, err := s.PageAt(ctx, tx, path)
		if err != nil {
			return out, err
		}
		if page != nil {
			if err := tx.Model(&models.Page{}).Where("id = ?", page.ID).UpdateColumn("reported_at", now).Error; err != nil {
				return out, err
			}
			out.Updated++
			continue
		}
		owned, err := s.ownerOutsideRegistry(ctx, path)
		if err != nil {
			return out, err
		}
		if owned != nil {
			out.Skipped++
			continue
		}
		p := models.Page{
			URL:        path,
			URLs:       lagoon.Jsonable[map[string]string]{Data: map[string]string{}, Valid: true},
			Title:      s.routeTitle(path),
			Titles:     lagoon.Jsonable[map[string]string]{Data: map[string]string{}, Valid: true},
			Kind:       models.PageKindPage,
			Origin:     models.PageOriginReported,
			ReportedAt: &now,
			CreatedAt:  &now,
			UpdatedAt:  &now,
		}
		res := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&p)
		if res.Error != nil {
			return out, res.Error
		}
		if res.RowsAffected == 0 || p.ID == 0 {
			// A concurrent report inserted it first.
			continue
		}
		out.Inserted++
		if err := s.RecordPage(ctx, tx, nil, p, false); err != nil {
			return out, err
		}
		cabana.EmitRecordSaved(ctx, s.app, tx, pact.RecordSaved{Controller: PagesController, Model: PageModel, ID: p.IDText(), Created: true})
	}
	if err := tx.Model(&models.Settings{}).Where("id = ?", 1).UpdateColumn("routes_reported_at", now).Error; err != nil {
		return out, err
	}
	return out, nil
}

// routeTitle is a reported page's name: its last path segment with
// hyphens and underscores as spaces and the first letter capitalised; the
// home page is named pages.home_title.
func (s *Service) routeTitle(path string) string {
	seg := strings.Trim(path, "/")
	if i := strings.LastIndex(seg, "/"); i >= 0 {
		seg = seg[i+1:]
	}
	if decoded, err := url.PathUnescape(seg); err == nil {
		seg = decoded
	}
	seg = strings.TrimSpace(strings.NewReplacer("-", " ", "_", " ").Replace(seg))
	if seg == "" {
		return s.Phrase("golem15.seo::lang.pages.home_title", nil)
	}
	r, size := utf8.DecodeRuneInString(seg)
	return string(unicode.ToUpper(r)) + seg[size:]
}

// PageMissing reports whether p is a reported page that the newest route
// report (at reported) did not name.
func PageMissing(p models.Page, reported *time.Time) bool {
	if p.Origin != models.PageOriginReported || reported == nil {
		return false
	}
	return p.ReportedAt == nil || p.ReportedAt.Before(*reported)
}

// pageKinds reads the kind of each registry page id (as text).
func pageKinds(db *gorm.DB, ids []string) (map[string]string, error) {
	var nums []uint64
	for _, id := range ids {
		if n, err := strconv.ParseUint(id, 10, 64); err == nil {
			nums = append(nums, n)
		}
	}
	out := map[string]string{}
	if len(nums) == 0 {
		return out, nil
	}
	var rows []struct {
		ID   uint64 `gorm:"column:id"`
		Kind string `gorm:"column:kind"`
	}
	if err := db.Raw(`SELECT id, kind FROM golem15_seo_pages WHERE id IN ?`, nums).Scan(&rows).Error; err != nil {
		return nil, err
	}
	for _, r := range rows {
		out[strconv.FormatUint(r.ID, 10)] = r.Kind
	}
	return out, nil
}