package web

import (
	"context"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/m/projax/caldav"
	"github.com/m/projax/gitea"
	"github.com/m/projax/store"
)

// dashboardCache holds the aggregated dashboard payload for up to TTL. Per
// design.md §9 every cache entry is keyed by the encoded TreeFilter (so
// `?tag=work` cache is independent of unfiltered), and the TTL is 60s.
type dashboardCache struct {
	ttl  time.Duration
	mu   sync.Mutex
	rows map[string]cachedDashboard
}

type cachedDashboard struct {
	at      time.Time
	payload *dashboardPayload
}

func newDashboardCache(ttl time.Duration) *dashboardCache {
	return &dashboardCache{ttl: ttl, rows: map[string]cachedDashboard{}}
}

func (c *dashboardCache) get(key string) (*dashboardPayload, bool) {
	if c == nil {
		return nil, false
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	v, ok := c.rows[key]
	if !ok {
		return nil, false
	}
	if time.Since(v.at) > c.ttl {
		delete(c.rows, key)
		return nil, false
	}
	return v.payload, true
}

func (c *dashboardCache) invalidate(key string) {
	if c == nil {
		return
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	delete(c.rows, key)
}

// invalidateAll wipes every cached payload. Used by writeback paths (Gitea
// close/comment/create, CalDAV completion) that can change content under any
// filter.
func (c *dashboardCache) invalidateAll() {
	if c == nil {
		return
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	c.rows = map[string]cachedDashboard{}
}

func (c *dashboardCache) set(key string, p *dashboardPayload) {
	if c == nil {
		return
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	c.rows[key] = cachedDashboard{at: time.Now(), payload: p}
}

// dashboardPayload is the full aggregated view rendered into the page. Each
// slice is already sorted and capped at the per-card limit.
type dashboardPayload struct {
	Tasks      []dashboardTask
	TaskGroups dashboardTaskGroups
	TaskTotal  int

	Issues     []dashboardIssue
	IssueTotal int

	RecentDocs    []dashboardDoc
	RecentDocsTotal int

	Stale      []dashboardStale
	StaleTotal int

	Events       []dashboardEventGroup // grouped by day, each group already sorted by start asc
	EventsFlat   []dashboardEvent      // flat list (template helper for "next event" sentinel)
	EventsTotal  int

	BuiltAt time.Time
	Cached  bool
}

// dashboardTask is one open VTODO from one linked calendar, with the project
// it belongs to already resolved for the row link.
type dashboardTask struct {
	Item        *store.Item
	CalendarURL string
	Todo        caldav.Todo
	DueRel      string // "today" / "tomorrow" / "in 3d" / "overdue 2d" / ""
	Bucket      string // today | tomorrow | week | overdue | no-due
}

// dashboardTaskGroups holds per-bucket counts for the section header.
type dashboardTaskGroups struct {
	Today    int
	Tomorrow int
	Week     int
	Overdue  int
	NoDue    int
}

type dashboardIssue struct {
	Item     *store.Item
	Repo     string
	Issue    gitea.Issue
	UpdRel   string
}

type dashboardDoc struct {
	Item       *store.Item
	Link       store.ItemLink
	PER        string
	ItemPath   string
}

// dashboardEvent is one VEVENT surfaced on the dashboard Events card. The
// Item it belongs to is resolved (it's the projax item the calendar is linked
// to), so a click on the row navigates to /i/{path}/.
type dashboardEvent struct {
	Item        *store.Item
	Event       caldav.Event
	CalendarRef string // calendar URL — kept for cache-bust / debug, not shown
	DayKey      string // YYYY-MM-DD for grouping
	StartLabel  string // "10:00" / "ganztägig" / ""
	DayLabel    string // "Today", "Tomorrow", "Wed 21 May", "Fri 23 May"
}

// dashboardEventGroup bundles a day's events for template-friendly rendering.
type dashboardEventGroup struct {
	DayKey   string // YYYY-MM-DD
	DayLabel string // "Today (3)" — count substituted at render time
	Events   []dashboardEvent
}

// dashboardStale is one mai-managed item whose linked repo is quiet, has no
// open issues, and whose linked CalDAV lists hold no open VTODOs. The
// "consider archiving?" candidate.
type dashboardStale struct {
	Item        *store.Item
	Repo        string // owner/repo of the quiet linked repo (first one wins)
	LastActive  time.Time
	StaleDays   int    // floor(days since LastActive)
	StaleRel    string // "62d", "120d", "no recent activity"
}

// handleDashboard renders the cross-project landing page. Filters reuse the
// tree-page TreeFilter; the per-card aggregation runs sequentially with a
// small worker pool to avoid hammering DAV / Gitea.
func (s *Server) handleDashboard(w http.ResponseWriter, r *http.Request) {
	filter := ParseTreeFilter(r.URL.Query())
	// Dashboard treats status=active as the meaningful default — same as tree.
	cacheKey := filter.QueryString()
	if cacheKey == "" {
		cacheKey = "__empty__"
	}

	// ?refresh=1 busts this filter's cache entry so the next aggregation
	// runs fresh — used by the ↻ button on the dashboard chrome.
	if r.URL.Query().Get("refresh") == "1" {
		s.dashboard.invalidate(cacheKey)
	}

	payload, hit := s.dashboard.get(cacheKey)
	if !hit {
		built, err := s.buildDashboard(r.Context(), filter)
		if err != nil {
			s.fail(w, r, err)
			return
		}
		s.dashboard.set(cacheKey, built)
		payload = built
	}
	displayPayload := *payload
	displayPayload.Cached = hit
	// Updated-relative label: how long since the cached payload was built.
	updatedRel := relativeTime(time.Now(), payload.BuiltAt)

	// Refresh URL: clone the current query, drop ?refresh, prepend it back.
	refreshURL := "/dashboard?refresh=1"
	if cacheKey != "__empty__" {
		refreshURL = "/dashboard?" + cacheKey + "&refresh=1"
	}

	data := map[string]any{
		"Title":      "dashboard",
		"P":          displayPayload,
		"Filter":     filter,
		"UpdatedRel": updatedRel,
		"RefreshURL": refreshURL,
		"FilterActive": filter.Active(),
	}
	if r.Header.Get("HX-Request") == "true" {
		s.render(w, "dashboard_section", data)
		return
	}
	s.render(w, "dashboard", data)
}

// buildDashboard does the actual aggregation work. Items are filtered first
// (by the same TreeFilter as /), then each linked calendar / repo / dated
// link is fanned out to a worker pool.
func (s *Server) buildDashboard(ctx context.Context, filter TreeFilter) (*dashboardPayload, error) {
	items, err := s.Store.ListAll(ctx)
	if err != nil {
		return nil, err
	}
	linkKinds, err := s.linkKindsByItem(ctx)
	if err != nil {
		return nil, err
	}
	// Filter items by the same rules as the tree (direct match only, no
	// branch-keep — dashboard cards never look at ancestors).
	dashItems := []*store.Item{}
	byID := map[string]*store.Item{}
	for _, it := range items {
		// Reuse TreeFilter.Matches with one tweak: when no filter is active we
		// include every item regardless of status so a "done" project's
		// recently-dated docs still surface.
		if !filter.Active() || filter.Matches(it, linkKinds[it.ID]) {
			dashItems = append(dashItems, it)
			byID[it.ID] = it
		}
	}

	now := time.Now()
	p := &dashboardPayload{BuiltAt: now}

	// --- Tasks card ---
	if s.CalDAV != nil {
		tasks, groups, total := s.collectTasks(ctx, dashItems, now)
		p.Tasks = tasks
		p.TaskGroups = groups
		p.TaskTotal = total
	}

	// --- Events card (Phase 3l) ---
	// Same caldav-list link source as Tasks, time-range filtered to the next
	// 7 days. Re-uses the 4-worker pool pattern; no extra DAV calls when the
	// dashboard cache hits.
	if s.CalDAV != nil {
		events, flat, total := s.collectEvents(ctx, dashItems, now)
		p.Events = events
		p.EventsFlat = flat
		p.EventsTotal = total
	}

	// --- Issues card ---
	if s.Gitea != nil {
		issues, total := s.collectIssues(ctx, dashItems, now)
		p.Issues = issues
		p.IssueTotal = total
	}

	// --- Recent documents card ---
	docs, total, err := s.collectRecentDocs(ctx, byID, dashItems, filter, now)
	if err != nil {
		s.Logger.Warn("dashboard docs", "err", err)
	}
	p.RecentDocs = docs
	p.RecentDocsTotal = total

	// --- Stale projects card ---
	// "Stale" = mai-managed AND linked-repo quiet 60d+ AND 0 open tasks AND
	// 0 open issues. Reuses what the task/issue cards already aggregated so
	// we don't refetch CalDAV/Gitea per item.
	openTasksByItem := map[string]int{}
	for _, t := range p.Tasks {
		openTasksByItem[t.Item.ID]++
	}
	openIssuesByItem := map[string]int{}
	for _, i := range p.Issues {
		openIssuesByItem[i.Item.ID]++
	}
	// Note: the 30-row cap on Tasks/Issues lists may hide entries for the
	// count above. We deliberately use the trimmed view: an item that has so
	// many open tasks/issues that it pushes past the 30 cap is clearly NOT
	// stale, and the per-item count is only used as "is this zero?".
	stale, staleTotal := s.collectStale(ctx, dashItems, openTasksByItem, openIssuesByItem, now)
	p.Stale = stale
	p.StaleTotal = staleTotal

	return p, nil
}

// collectStale walks every mai-managed item whose only signals are quiet:
// no open tasks (in the aggregated map), no open issues (in the aggregated
// map), AND the linked Gitea repo's updated_at is older than 60d. Items
// with NO linked repo at all are skipped — we can't judge staleness without
// a signal. Returns at most 20 rows, longest-stale first.
func (s *Server) collectStale(ctx context.Context, items []*store.Item, openTasks, openIssues map[string]int, now time.Time) ([]dashboardStale, int) {
	if s.Gitea == nil {
		return nil, 0
	}
	const staleCutoffDays = 60
	type job struct {
		item *store.Item
		link *store.ItemLink
	}
	jobs := []job{}
	for _, it := range items {
		if !it.HasManagement("mai") {
			continue
		}
		if openTasks[it.ID] > 0 || openIssues[it.ID] > 0 {
			continue
		}
		links, err := s.Store.LinksByType(ctx, it.ID, refTypeGiteaRepo)
		if err != nil || len(links) == 0 {
			continue
		}
		// First linked repo wins for the staleness probe — if an item has
		// multiple linked repos and ANY is recent we treat the item as not
		// stale, so the candidate-list pass is conservative on the "stale"
		// side. Implemented by emitting jobs for every link + filtering on
		// "every link is stale" in the result reduce.
		for _, l := range links {
			jobs = append(jobs, job{item: it, link: l})
		}
	}
	if len(jobs) == 0 {
		return nil, 0
	}

	type res struct {
		itemID  string
		repo    string
		updated time.Time
		err     bool
	}
	results := make(chan res, len(jobs))
	in := make(chan job, len(jobs))
	const workers = 4
	var wg sync.WaitGroup
	for i := 0; i < workers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := range in {
				owner, repo := gitea.ParseRepoRef(j.link.RefID)
				if owner == "" || repo == "" {
					results <- res{itemID: j.item.ID, repo: j.link.RefID, err: true}
					continue
				}
				r, err := s.Gitea.Client.GetRepo(ctx, owner, repo)
				if err != nil {
					s.Logger.Warn("dashboard stale get repo", "repo", j.link.RefID, "err", err)
					results <- res{itemID: j.item.ID, repo: j.link.RefID, err: true}
					continue
				}
				results <- res{itemID: j.item.ID, repo: j.link.RefID, updated: r.UpdatedAt}
			}
		}()
	}
	for _, j := range jobs {
		in <- j
	}
	close(in)
	wg.Wait()
	close(results)

	// Reduce by item: track the most-recent updated_at across the item's
	// repos. Stale only if ALL probed repos are older than the cutoff.
	type acc struct {
		newest time.Time
		repo   string // newest-updated repo wins the display slot
		anyErr bool
	}
	byItem := map[string]*acc{}
	for r := range results {
		a, ok := byItem[r.itemID]
		if !ok {
			a = &acc{}
			byItem[r.itemID] = a
		}
		if r.err {
			a.anyErr = true
			continue
		}
		if r.updated.After(a.newest) {
			a.newest = r.updated
			a.repo = r.repo
		}
	}

	byID := map[string]*store.Item{}
	for _, it := range items {
		byID[it.ID] = it
	}
	cutoff := now.AddDate(0, 0, -staleCutoffDays)
	out := []dashboardStale{}
	for id, a := range byItem {
		if a.anyErr || a.newest.IsZero() {
			continue
		}
		if a.newest.After(cutoff) {
			continue
		}
		it := byID[id]
		if it == nil {
			continue
		}
		days := int(now.Sub(a.newest).Hours() / 24)
		out = append(out, dashboardStale{
			Item:       it,
			Repo:       a.repo,
			LastActive: a.newest,
			StaleDays:  days,
			StaleRel:   relDays(days),
		})
	}
	sort.Slice(out, func(i, j int) bool {
		return out[i].StaleDays > out[j].StaleDays
	})
	total := len(out)
	if len(out) > 20 {
		out = out[:20]
	}
	return out, total
}

// collectTasks fans out across every (item, caldav-list link) pair using a
// small worker pool. Per-calendar errors are logged and skipped so one down
// calendar doesn't blank the whole card.
func (s *Server) collectTasks(ctx context.Context, items []*store.Item, now time.Time) ([]dashboardTask, dashboardTaskGroups, int) {
	type job struct {
		item *store.Item
		link *store.ItemLink
	}
	jobs := []job{}
	for _, it := range items {
		links, err := s.Store.LinksByType(ctx, it.ID, refTypeCalDAV)
		if err != nil {
			s.Logger.Warn("dashboard caldav links", "item", it.PrimaryPath(), "err", err)
			continue
		}
		for _, l := range links {
			jobs = append(jobs, job{item: it, link: l})
		}
	}
	type result struct {
		item        *store.Item
		calendarURL string
		todos       []caldav.Todo
	}
	results := make(chan result, len(jobs))
	in := make(chan job, len(jobs))
	const workers = 4
	var wg sync.WaitGroup
	for i := 0; i < workers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := range in {
				todos, err := s.CalDAV.Client.ListTodos(ctx, j.link.RefID)
				if err != nil {
					s.Logger.Warn("dashboard list todos", "calendar", j.link.RefID, "err", err)
					continue
				}
				open := []caldav.Todo{}
				for _, t := range todos {
					if t.Status == "COMPLETED" || t.Status == "CANCELLED" {
						continue
					}
					open = append(open, t)
				}
				results <- result{item: j.item, calendarURL: j.link.RefID, todos: open}
			}
		}()
	}
	for _, j := range jobs {
		in <- j
	}
	close(in)
	wg.Wait()
	close(results)

	out := []dashboardTask{}
	groups := dashboardTaskGroups{}
	for r := range results {
		for _, td := range r.todos {
			dt := dashboardTask{Item: r.item, CalendarURL: r.calendarURL, Todo: td}
			dt.Bucket, dt.DueRel = classifyDue(td.Due, now)
			switch dt.Bucket {
			case "overdue":
				groups.Overdue++
			case "today":
				groups.Today++
			case "tomorrow":
				groups.Tomorrow++
			case "week":
				groups.Week++
			default:
				groups.NoDue++
			}
			out = append(out, dt)
		}
	}
	// Sort: overdue first, then due asc, no-due last; ties by priority desc, summary asc.
	sort.Slice(out, func(i, j int) bool {
		a, b := out[i], out[j]
		// Overdue precedes everything.
		if (a.Bucket == "overdue") != (b.Bucket == "overdue") {
			return a.Bucket == "overdue"
		}
		// No-due sinks below dated.
		ad := a.Todo.Due != nil
		bd := b.Todo.Due != nil
		if ad != bd {
			return ad
		}
		if ad && bd && !a.Todo.Due.Equal(*b.Todo.Due) {
			return a.Todo.Due.Before(*b.Todo.Due)
		}
		if a.Todo.Priority != b.Todo.Priority {
			return a.Todo.Priority > b.Todo.Priority
		}
		return a.Todo.Summary < b.Todo.Summary
	})
	total := len(out)
	if len(out) > 30 {
		out = out[:30]
	}
	return out, groups, total
}

// classifyDue buckets a VTODO by its DUE date relative to now.
//   overdue:   due strictly before today
//   today:     due == today
//   tomorrow:  due == today+1
//   week:      due in (today+2 ... today+7)
//   no-due:    no due at all
// Returns (bucket, relative-text).
func classifyDue(due *time.Time, now time.Time) (string, string) {
	if due == nil {
		return "no-due", ""
	}
	today := startOfDay(now)
	dueDay := startOfDay(due.Local())
	days := int(dueDay.Sub(today).Hours() / 24)
	switch {
	case days < 0:
		return "overdue", "overdue " + relDays(-days)
	case days == 0:
		return "today", "today"
	case days == 1:
		return "tomorrow", "tomorrow"
	case days <= 7:
		return "week", "in " + relDays(days)
	default:
		return "later", dueDay.Format("2006-01-02")
	}
}

func startOfDay(t time.Time) time.Time {
	return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
}

func relDays(n int) string { return strconv.Itoa(n) + "d" }

// collectIssues fans out across every (item, gitea-repo link) pair, reusing
// the Gitea client's existing TTL cache (set by NewGiteaDeps).
func (s *Server) collectIssues(ctx context.Context, items []*store.Item, now time.Time) ([]dashboardIssue, int) {
	type job struct {
		item *store.Item
		link *store.ItemLink
	}
	jobs := []job{}
	for _, it := range items {
		links, err := s.Store.LinksByType(ctx, it.ID, refTypeGiteaRepo)
		if err != nil {
			s.Logger.Warn("dashboard gitea links", "item", it.PrimaryPath(), "err", err)
			continue
		}
		for _, l := range links {
			jobs = append(jobs, job{item: it, link: l})
		}
	}
	type result struct {
		item *store.Item
		repo string
		open []gitea.Issue
	}
	results := make(chan result, len(jobs))
	in := make(chan job, len(jobs))
	const workers = 4
	var wg sync.WaitGroup
	for i := 0; i < workers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := range in {
				owner, repo := gitea.ParseRepoRef(j.link.RefID)
				if owner == "" || repo == "" {
					continue
				}
				key := j.link.RefID + "|open"
				open, ok := s.Gitea.Cache.get(key)
				if !ok {
					var err error
					open, err = s.Gitea.Client.ListIssues(ctx, owner, repo, gitea.ListOpts{State: "open"})
					if err != nil {
						s.Logger.Warn("dashboard gitea list", "repo", j.link.RefID, "err", err)
						continue
					}
					s.Gitea.Cache.set(key, open)
				}
				results <- result{item: j.item, repo: j.link.RefID, open: open}
			}
		}()
	}
	for _, j := range jobs {
		in <- j
	}
	close(in)
	wg.Wait()
	close(results)

	out := []dashboardIssue{}
	for r := range results {
		for _, iss := range r.open {
			out = append(out, dashboardIssue{
				Item:   r.item,
				Repo:   r.repo,
				Issue:  iss,
				UpdRel: relativeTime(now, iss.UpdatedAt),
			})
		}
	}
	sort.Slice(out, func(i, j int) bool {
		return out[i].Issue.UpdatedAt.After(out[j].Issue.UpdatedAt)
	})
	total := len(out)
	if len(out) > 30 {
		out = out[:30]
	}
	return out, total
}

// collectRecentDocs reads the last-30-days dated item_links and joins them to
// the filtered items. Items the filter dropped don't contribute docs.
func (s *Server) collectRecentDocs(ctx context.Context, byID map[string]*store.Item, _ []*store.Item, _ TreeFilter, now time.Time) ([]dashboardDoc, int, error) {
	since := now.AddDate(0, 0, -30)
	rows, err := s.Store.RecentDocuments(ctx, since, 200)
	if err != nil {
		return nil, 0, err
	}
	out := []dashboardDoc{}
	for _, r := range rows {
		it := byID[r.Link.ItemID]
		if it == nil {
			continue
		}
		base := it.PrimaryPath()
		per := base
		if r.Link.EventDate != nil {
			per = base + "." + formatPERDate(*r.Link.EventDate)
		}
		out = append(out, dashboardDoc{
			Item:     it,
			Link:     r.Link,
			PER:      per,
			ItemPath: base,
		})
	}
	total := len(out)
	if len(out) > 30 {
		out = out[:30]
	}
	return out, total, nil
}

// handleDashboardTaskDone is the inline ✓-checkbox handler on the Tasks card.
// It POSTs the calendar URL + UID, marks the VTODO COMPLETED via the same
// PutTodo path the detail page uses, then re-renders the dashboard section
// so the row disappears and the count decrements.
func (s *Server) handleDashboardTaskDone(w http.ResponseWriter, r *http.Request) {
	if s.CalDAV == nil {
		http.Error(w, "caldav not configured", http.StatusServiceUnavailable)
		return
	}
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	calURL := strings.TrimSpace(r.FormValue("calendar_url"))
	uid := strings.TrimSpace(r.FormValue("uid"))
	if calURL == "" || uid == "" {
		http.Error(w, "calendar_url and uid required", http.StatusBadRequest)
		return
	}

	todos, err := s.CalDAV.Client.ListTodos(r.Context(), calURL)
	if err != nil {
		http.Error(w, "list todos: "+err.Error(), http.StatusBadGateway)
		return
	}
	var current *caldav.Todo
	for i := range todos {
		if todos[i].UID == uid {
			current = &todos[i]
			break
		}
	}
	if current == nil {
		// Task already gone — drop cache + re-render so the row vanishes.
		s.dashboard = newDashboardCache(s.dashboard.ttl)
		s.handleDashboard(w, r)
		return
	}
	st := "COMPLETED"
	updated := caldav.ApplyVTodoEdit(current.Raw, caldav.VTodoEdit{Status: &st})
	if _, err := s.CalDAV.Client.PutTodo(r.Context(), current.URL, updated, current.ETag, ""); err != nil {
		http.Error(w, "complete: "+err.Error(), http.StatusBadGateway)
		return
	}
	// Bust the dashboard cache so the row disappears on next render.
	s.dashboard = newDashboardCache(s.dashboard.ttl)
	s.handleDashboard(w, r)
}

// collectEvents fans out across every (item, caldav-list link) pair using a
// 4-worker pool — same pattern as collectTasks. Time window is fixed at the
// next 7 days (RFC 4791 §9.9 server-side time-range filter). RRULE-bearing
// events surface as a single literal-DTSTART row with Recurring=true; no
// expansion. Returns grouped-by-day, flat, and total count.
func (s *Server) collectEvents(ctx context.Context, items []*store.Item, now time.Time) ([]dashboardEventGroup, []dashboardEvent, int) {
	type job struct {
		item *store.Item
		link *store.ItemLink
	}
	jobs := []job{}
	for _, it := range items {
		links, err := s.Store.LinksByType(ctx, it.ID, refTypeCalDAV)
		if err != nil {
			s.Logger.Warn("dashboard caldav-events links", "item", it.PrimaryPath(), "err", err)
			continue
		}
		for _, l := range links {
			jobs = append(jobs, job{item: it, link: l})
		}
	}
	type result struct {
		item   *store.Item
		ref    string
		events []caldav.Event
	}
	results := make(chan result, len(jobs))
	in := make(chan job, len(jobs))
	const workers = 4
	var wg sync.WaitGroup

	opts := caldav.ListEventsOpts{
		TimeMin: startOfDay(now),
		TimeMax: startOfDay(now).AddDate(0, 0, 7),
	}
	for i := 0; i < workers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := range in {
				events, err := s.CalDAV.Client.ListEvents(ctx, j.link.RefID, opts)
				if err != nil {
					s.Logger.Warn("dashboard list events", "calendar", j.link.RefID, "err", err)
					continue
				}
				results <- result{item: j.item, ref: j.link.RefID, events: events}
			}
		}()
	}
	for _, j := range jobs {
		in <- j
	}
	close(in)
	wg.Wait()
	close(results)

	flat := []dashboardEvent{}
	for r := range results {
		for _, ev := range r.events {
			flat = append(flat, dashboardEvent{
				Item:        r.item,
				Event:       ev,
				CalendarRef: r.ref,
				DayKey:      ev.Start.Format("2006-01-02"),
				StartLabel:  eventStartLabel(ev),
				DayLabel:    dayLabelFor(ev.Start, now),
			})
		}
	}
	// Sort flat: start asc, summary asc as tiebreaker for stable rendering.
	sort.Slice(flat, func(i, j int) bool {
		if !flat[i].Event.Start.Equal(flat[j].Event.Start) {
			return flat[i].Event.Start.Before(flat[j].Event.Start)
		}
		return flat[i].Event.Summary < flat[j].Event.Summary
	})
	total := len(flat)
	if len(flat) > 50 {
		flat = flat[:50]
	}

	// Group by DayKey while preserving the start-asc ordering.
	groups := []dashboardEventGroup{}
	var cur *dashboardEventGroup
	for _, e := range flat {
		if cur == nil || cur.DayKey != e.DayKey {
			groups = append(groups, dashboardEventGroup{DayKey: e.DayKey, DayLabel: e.DayLabel})
			cur = &groups[len(groups)-1]
		}
		cur.Events = append(cur.Events, e)
	}
	return groups, flat, total
}

// eventStartLabel renders an event's start time as "10:00", "ganztägig" for
// all-day events, or "" if Start is the zero value.
func eventStartLabel(ev caldav.Event) string {
	if ev.AllDay {
		return "ganztägig"
	}
	if ev.Start.IsZero() {
		return ""
	}
	return ev.Start.Local().Format("15:04")
}

// dayLabelFor returns a short human label for the day containing t, relative
// to now: "Today", "Tomorrow", weekday + dd MMM. German weekday names for
// consistency with the mgmt cockpit it replaces.
func dayLabelFor(t, now time.Time) string {
	today := startOfDay(now)
	day := startOfDay(t.Local())
	switch int(day.Sub(today).Hours() / 24) {
	case 0:
		return "Today"
	case 1:
		return "Tomorrow"
	}
	return day.Format("Mon 02 Jan")
}