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/internal/aggregate"
	"github.com/m/projax/store"
)

// dashboardCache TTL — Phase 5b unified the per-cache types into the
// generic internal/cache.TTLCache[V]. Design note (design.md §9): every
// cache entry is keyed by the encoded TreeFilter (so `?tag=work` cache is
// independent of unfiltered).
const dashboardCacheTTL = 60 * time.Second

// 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

	// Projects is the Phase 5h per-project rollup. Populated alongside the
	// other cards from the same aggregator fetches. Consumed by the Tiles
	// view; the Tasks/Events views ignore it. Sorted pinned-first then by
	// primary path ascending.
	Projects []dashboardProject

	// ProjectsCurrent / ProjectsQuiet are the per-request scope-split of
	// Projects — populated by the handler, not the cache, so the scope
	// chip can toggle without recomputing. The Tiles view renders Current
	// in the primary grid and Quiet behind a "Quiet (N) ▾" fold.
	ProjectsCurrent  []dashboardProject `json:"-"`
	ProjectsQuiet    []dashboardProject `json:"-"`
	QuietStaleCount  int                `json:"-"` // subset of ProjectsQuiet flagged stale, for the fold label
	QuietWindowLabel string             `json:"-"` // e.g. "14d" — derived from dashboardActivityWindow

	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"
}

// Dashboard view-switcher (Phase 5h) — three tabs share the same
// aggregated data and filter strip; each renders a different shape.
// Defaults elide from URL so /dashboard means /dashboard?view=tiles.
const (
	dashboardViewTiles  = "tiles"
	dashboardViewTasks  = "tasks"
	dashboardViewEvents = "events"
)

// Dashboard scope (Phase 5h Tiles view) — narrows the tile grid to the
// projects m is plausibly working on (the IsCurrent set), folding the
// rest into a "Quiet (N) ▾" section. Default = current.
const (
	dashboardScopeCurrent = "current"
	dashboardScopeAll     = "all"
)

// parseDashboardView normalizes the ?view= query into one of the three
// known shapes, falling back to Tiles (the default per m's §7 pick).
func parseDashboardView(raw string) string {
	switch strings.ToLower(strings.TrimSpace(raw)) {
	case dashboardViewTasks:
		return dashboardViewTasks
	case dashboardViewEvents:
		return dashboardViewEvents
	default:
		return dashboardViewTiles
	}
}

// parseDashboardScope normalizes the ?scope= query, falling back to
// "current" (the daily-driver default per m's §7 pick).
func parseDashboardScope(raw string) string {
	if strings.EqualFold(strings.TrimSpace(raw), dashboardScopeAll) {
		return dashboardScopeAll
	}
	return dashboardScopeCurrent
}

// 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())
	view := parseDashboardView(r.URL.Query().Get("view"))
	scope := parseDashboardScope(r.URL.Query().Get("scope"))
	// Dashboard treats status=active as the meaningful default — same as tree.
	filterKey := filter.QueryString()
	if filterKey == "" {
		filterKey = "__empty__"
	}
	// Cache key composes filter + view + scope so each surface has its own
	// 60s TTL entry. Scope only changes the Tiles split; we still key it
	// in for every view so the future Activity tab can ride the same path.
	cacheKey := filterKey + "|view=" + view + "|scope=" + scope

	// ?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)

	// Split the rollup into Current vs. Quiet according to the active
	// scope. For scope=all we keep everything Current; for scope=current
	// (default) we use IsCurrent + the Stale set to populate Quiet.
	now := time.Now()
	current, quiet := splitProjectsByScope(displayPayload.Projects, scope, now)
	displayPayload.ProjectsCurrent = current
	displayPayload.ProjectsQuiet = quiet
	staleCount := 0
	for _, p := range quiet {
		if p.Stale {
			staleCount++
		}
	}
	displayPayload.QuietStaleCount = staleCount
	displayPayload.QuietWindowLabel = strconv.Itoa(int(dashboardActivityWindow/(24*time.Hour))) + "d"

	// Refresh URL preserves the active view + scope + filter.
	refreshQuery := filterKey
	if refreshQuery == "__empty__" {
		refreshQuery = ""
	}
	if view != dashboardViewTiles {
		if refreshQuery != "" {
			refreshQuery += "&"
		}
		refreshQuery += "view=" + view
	}
	if scope != dashboardScopeCurrent {
		if refreshQuery != "" {
			refreshQuery += "&"
		}
		refreshQuery += "scope=" + scope
	}
	refreshURL := "/views/dashboard?"
	if refreshQuery != "" {
		refreshURL += refreshQuery + "&"
	}
	refreshURL += "refresh=1"

	projects, err := s.parentOptions(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	data := map[string]any{
		"Title":             "dashboard",
		"P":                 displayPayload,
		"Filter":            filter,
		"View":              view,
		"Scope":             scope,
		"Tabs":              dashboardTabs(view, filterKey, scope),
		"ScopeURL":          dashboardScopeToggleURL(view, scope, filterKey),
		"UpdatedRel":        updatedRel,
		"RefreshURL":        refreshURL,
		"FilterActive":      filter.Active(),
		"Projects":          projects,
		"BasePath":          "/views/dashboard",
		"ProjectChipTarget": "#dashboard-section",
	}
	if r.Header.Get("HX-Request") == "true" {
		s.render(w, r, "dashboard_section", data)
		return
	}
	s.render(w, r, "dashboard", data)
}

// splitProjectsByScope partitions the rollup into the primary grid
// (ProjectsCurrent) and the Quiet fold (ProjectsQuiet) per m's §7 pick.
//   scope=all     → everything counts as Current; Quiet is empty.
//   scope=current → IsCurrent(now) selects Current; the rest (including
//                   stale candidates) move to Quiet.
func splitProjectsByScope(projects []dashboardProject, scope string, now time.Time) (current, quiet []dashboardProject) {
	if scope == dashboardScopeAll {
		return projects, nil
	}
	for _, p := range projects {
		if p.IsCurrent(now) {
			current = append(current, p)
		} else {
			quiet = append(quiet, p)
		}
	}
	return current, quiet
}

// dashboardScopeToggleURL builds the URL that flips the scope chip —
// /dashboard with the alternate scope and the current view + filter
// preserved.
func dashboardScopeToggleURL(view, scope, filterKey string) string {
	next := dashboardScopeAll
	if scope == dashboardScopeAll {
		next = dashboardScopeCurrent
	}
	parts := []string{}
	if filterKey != "__empty__" && filterKey != "" {
		parts = append(parts, filterKey)
	}
	if view != dashboardViewTiles {
		parts = append(parts, "view="+view)
	}
	if next != dashboardScopeCurrent {
		parts = append(parts, "scope="+next)
	}
	if len(parts) == 0 {
		return "/views/dashboard"
	}
	return "/views/dashboard?" + strings.Join(parts, "&")
}

// dashboardTab is a single entry in the view-switcher strip.
type dashboardTab struct {
	View   string // tiles | tasks | events
	Label  string
	URL    string
	Active bool
}

// dashboardTabs builds the three-entry tab strip with each tab's URL
// preserving the active filter + scope. The default view (tiles) and
// scope (current) elide from the URL so the address bar stays clean
// on the daily-driver path.
func dashboardTabs(active, filterKey, scope string) []dashboardTab {
	prefix := "/views/dashboard"
	filterQuery := ""
	if filterKey != "__empty__" && filterKey != "" {
		filterQuery = filterKey
	}
	tabURL := func(view string) string {
		parts := []string{}
		if filterQuery != "" {
			parts = append(parts, filterQuery)
		}
		if view != dashboardViewTiles {
			parts = append(parts, "view="+view)
		}
		if scope != dashboardScopeCurrent {
			parts = append(parts, "scope="+scope)
		}
		if len(parts) == 0 {
			return prefix
		}
		return prefix + "?" + strings.Join(parts, "&")
	}
	return []dashboardTab{
		{View: dashboardViewTiles, Label: "Tiles", URL: tabURL(dashboardViewTiles), Active: active == dashboardViewTiles},
		{View: dashboardViewTasks, Label: "Tasks", URL: tabURL(dashboardViewTasks), Active: active == dashboardViewTasks},
		{View: dashboardViewEvents, Label: "Events", URL: tabURL(dashboardViewEvents), Active: active == dashboardViewEvents},
	}
}

// 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. Phase 5h: aggregator rows are
// fetched once at the top, then projected into both the legacy card
// shapes AND the new per-project rollup so the rollup costs zero extra
// DAV/Gitea calls.
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}

	// --- Fetch raw rows once (Phase 5h refactor) ---
	// The projection helpers cap + sort for the card shapes; the rollup
	// uses the uncapped rows so OpenTasks/OpenIssues counts are accurate.
	var todoRows []aggregate.TodoRow
	var eventRows []aggregate.EventRow
	if s.CalDAV != nil {
		todoRows = s.Aggregator().Todos(ctx, dashItems, aggregate.Window{})
		eventWindow := aggregate.Window{From: startOfDay(now), To: startOfDay(now).AddDate(0, 0, 7)}
		eventRows = s.Aggregator().Events(ctx, dashItems, eventWindow)
	}
	var issueRows []aggregate.IssueRow
	if s.Gitea != nil {
		issueRows = s.Aggregator().Issues(ctx, dashItems)
	}

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

	// --- Events card (Phase 3l) ---
	if s.CalDAV != nil {
		events, flat, total := projectEvents(eventRows, now)
		p.Events = events
		p.EventsFlat = flat
		p.EventsTotal = total
	}

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

	// --- Recent documents card ---
	since := now.AddDate(0, 0, -30)
	docRows, err := s.Store.RecentDocuments(ctx, since, 200)
	if err != nil {
		s.Logger.Warn("dashboard docs", "err", err)
	}
	docs, docTotal := projectDocs(docRows, byID)
	p.RecentDocs = docs
	p.RecentDocsTotal = docTotal

	// --- 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, repoActivity := s.collectStale(ctx, dashItems, openTasksByItem, openIssuesByItem, now)
	p.Stale = stale
	p.StaleTotal = staleTotal

	// --- Per-project rollup (Phase 5h) ---
	staleByItem := make(map[string]bool, len(stale))
	for _, st := range stale {
		staleByItem[st.Item.ID] = true
	}
	p.Projects = collectProjectRollups(dashItems, todoRows, issueRows, eventRows, docRows, repoActivity, staleByItem, now)

	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), the total
// count, and a per-item map of the newest repo updated_at seen across all
// probed repos. The map covers every item that had at least one probed
// repo regardless of staleness — Phase 5h's rollup uses it as a
// LastActivity signal without doing a second Gitea round-trip.
func (s *Server) collectStale(ctx context.Context, items []*store.Item, openTasks, openIssues map[string]int, now time.Time) ([]dashboardStale, int, map[string]time.Time) {
	if s.Gitea == nil {
		return nil, 0, nil
	}
	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, nil
	}

	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]
	}
	// Build the repo-activity map: every item with at least one successful
	// probe contributes its newest repo updated_at, regardless of staleness.
	// The rollup uses this as a LastActivity signal.
	repoActivity := make(map[string]time.Time, len(byItem))
	for id, a := range byItem {
		if a.anyErr || a.newest.IsZero() {
			continue
		}
		repoActivity[id] = a.newest
	}
	return out, total, repoActivity
}

// projectTasks projects raw TodoRows fetched by the aggregator into the
// dashboard's view shape (due-status bucket + relative label + group
// counts + 30-row cap). Pure function: no I/O.
func projectTasks(rows []aggregate.TodoRow, now time.Time) ([]dashboardTask, dashboardTaskGroups, int) {
	out := []dashboardTask{}
	groups := dashboardTaskGroups{}
	for _, r := range rows {
		td := r.Todo
		if td.Status == "COMPLETED" || td.Status == "CANCELLED" {
			continue
		}
		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]
		if (a.Bucket == "overdue") != (b.Bucket == "overdue") {
			return a.Bucket == "overdue"
		}
		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" }

// projectIssues projects raw IssueRows into the dashboard's view shape,
// sorted updated_at desc and capped at 30.
func projectIssues(rows []aggregate.IssueRow, now time.Time) ([]dashboardIssue, int) {
	out := make([]dashboardIssue, 0, len(rows))
	for _, r := range rows {
		out = append(out, dashboardIssue{
			Item:   r.Item,
			Repo:   r.Repo,
			Issue:  r.Issue,
			UpdRel: relativeTime(now, r.Issue.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
}

// projectDocs joins pre-fetched dated item_links to the filtered item set
// (rows whose owning item is not in scope are dropped) and projects them
// into the Recent Documents card shape, capped at 30.
func projectDocs(rows []*store.ItemLinkWithItem, byID map[string]*store.Item) ([]dashboardDoc, int) {
	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
}

// 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) {
	s.dashboardTaskWrite(w, r, "complete")
}

// handleDashboardTaskEdit lets m rename a task or change its DUE date from the
// Tasks card without leaving the dashboard. Same routing key as Done — POST
// with calendar_url + uid + summary + optional due — but applies a VTodoEdit
// rather than flipping STATUS.
func (s *Server) handleDashboardTaskEdit(w http.ResponseWriter, r *http.Request) {
	s.dashboardTaskWrite(w, r, "edit")
}

// handleDashboardTaskDelete removes a VTODO from the Tasks card with the same
// DAV path as the detail page (DELETE with If-Match).
func (s *Server) handleDashboardTaskDelete(w http.ResponseWriter, r *http.Request) {
	s.dashboardTaskWrite(w, r, "delete")
}

// dashboardTaskWrite is the shared body for the three Tasks-card writeback
// actions. Routing here keeps the calendar-not-linked-to-item guard, ETag
// reload, and dashboard cache invalidation in one place.
func (s *Server) dashboardTaskWrite(w http.ResponseWriter, r *http.Request, action string) {
	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
	}
	// Belt-and-braces: confirm the calendar is actually linked to a projax
	// item before writing — otherwise a crafted form could nuke an arbitrary
	// calendar URL the dashboard didn't surface.
	if ok, err := s.calendarLinked(r.Context(), calURL); err != nil {
		s.fail(w, r, err)
		return
	} else if !ok {
		http.Error(w, "calendar not linked to any projax item", http.StatusForbidden)
		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.InvalidateAll()
		s.handleDashboard(w, r)
		return
	}
	switch action {
	case "complete":
		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
		}
	case "edit":
		edit := caldav.VTodoEdit{}
		if v := r.FormValue("summary"); strings.TrimSpace(v) != "" {
			vv := strings.TrimSpace(v)
			edit.Summary = &vv
		}
		if dueStr := strings.TrimSpace(r.FormValue("due")); dueStr != "" {
			if t, ok := parseDueInput(dueStr); ok {
				edit.Due = &t
			}
		} else if _, present := r.Form["due"]; present {
			edit.ClearDue = true
		}
		updated := caldav.ApplyVTodoEdit(current.Raw, edit)
		if _, err := s.CalDAV.Client.PutTodo(r.Context(), current.URL, updated, current.ETag, ""); err != nil {
			http.Error(w, "edit: "+err.Error(), http.StatusBadGateway)
			return
		}
	case "delete":
		if err := s.CalDAV.Client.DeleteTodo(r.Context(), current.URL, current.ETag); err != nil {
			http.Error(w, "delete: "+err.Error(), http.StatusBadGateway)
			return
		}
	default:
		http.Error(w, "unknown action: "+action, http.StatusBadRequest)
		return
	}
	s.dashboard.InvalidateAll()
	s.timeline.InvalidateAll()
	// Re-render whichever surface the request came from. HTMX sets HX-Target
	// to the swap target's id; the timeline surface uses #timeline-section.
	// Non-HTMX clients fall through to the dashboard re-render.
	if r.Header.Get("HX-Target") == "timeline-section" {
		s.handleTimeline(w, r)
		return
	}
	s.handleDashboard(w, r)
}

// calendarLinked reports whether any projax item carries a caldav-list link
// pointing at the given URL. Used as the dashboard's write-side ownership
// guard.
func (s *Server) calendarLinked(ctx context.Context, calURL string) (bool, error) {
	links, err := s.Store.LinksByRefType(ctx, refTypeCalDAV)
	if err != nil {
		return false, err
	}
	for _, l := range links {
		if l.RefID == calURL {
			return true, nil
		}
	}
	return false, nil
}

// projectEvents projects raw EventRows fetched for the next-7-day window
// into dashboard-flavoured row + group shape. RRULE-bearing events
// surface as a single literal-DTSTART row with Recurring=true; no
// expansion. Returns grouped-by-day, flat, total.
func projectEvents(rows []aggregate.EventRow, now time.Time) ([]dashboardEventGroup, []dashboardEvent, int) {
	flat := make([]dashboardEvent, 0, len(rows))
	for _, r := range rows {
		ev := r.Event
		flat = append(flat, dashboardEvent{
			Item:        r.Item,
			Event:       ev,
			CalendarRef: "", // dashboard never surfaces it; kept for backwards-compat in the struct.
			DayKey:      ev.Start.Format("2006-01-02"),
			StartLabel:  aggregate.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
}

// 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")
}