package web

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/url"
	"strings"
	"time"

	"pete/internal/storage"
)

// Adventure alerts: the only channel that reaches a player who isn't looking at
// the site or at Matrix.
//
// This rides entirely on facts gogobee is already sending. Every trigger below
// is a dispatch that already lands in adventure_events, so the whole phase is
// Pete-side and no new wire, event type or deploy ordering is involved.
//
// Two things separate it from the news digest it sits beside:
//
//   - Its own clock. A digest is a summary and six hours late is fine; "the
//     Siege has begun" six hours late is worse than silence, because the bout
//     the alert is asking for may already be over.
//   - Its own watermark (last_adv_notified_at). Sharing the digest's column
//     would let each sender consume the other's backlog.

// advAlertInterval matches the roster tick that delivers the facts. Checking
// faster than they can arrive only burns queries.
const advAlertInterval = 2 * time.Minute

// advAlertScan caps how many dispatches one pass inspects. Generously above the
// realm's real rate (a busy day is tens of dispatches, not hundreds), so hitting
// it means something is wrong rather than something is busy — see the warning in
// sendAdventureAlerts.
const advAlertScan = 200

// advPrefsKey is where the client stores the per-category opt-ins, alongside the
// other synced preferences. Its value is a JSON object of {category: true}.
const advPrefsKey = "pete.advPush.v1"

// The alert categories. Every one is opt-in and defaults OFF: a user who turned
// on notifications did so for news, and quietly enrolling them in game alerts
// they never asked for is how a notification permission gets revoked for good.
//
// advCatSiege is realm-wide — it needs no ownership and reaches everyone who
// asked for it. The other three are owner-scoped and reach exactly one person.
const (
	advCatSiege     = "siege"
	advCatRun       = "run"
	advCatDeparture = "departure"
	advCatContract  = "contract"
)

// advAlert is one notification a pass has decided to send.
type advAlert struct {
	Category string
	Title    string
	Body     string
	URL      string
}

// StartAdventureAlerts launches the alert loop when push and the adventure
// section are both configured. Safe to call unconditionally.
func (s *Server) StartAdventureAlerts(ctx context.Context) {
	if !s.cfg.Push.Enabled || s.auth == nil || !s.adv.Enabled {
		return
	}
	go s.runAdventureAlerts(ctx)
}

func (s *Server) runAdventureAlerts(ctx context.Context) {
	slog.Info("web: adventure alert sender started", "interval", advAlertInterval)
	ticker := time.NewTicker(advAlertInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			s.sendAdventureAlerts()
		}
	}
}

// sendAdventureAlerts runs one pass: read the dispatches nobody has been told
// about yet, and for each subscription decide whether any of them is that
// person's business.
func (s *Server) sendAdventureAlerts() {
	subs, err := storage.ListPushSubscriptions()
	if err != nil {
		slog.Error("adv-push: list subscriptions failed", "err", err)
		return
	}
	if len(subs) == 0 {
		return
	}

	now := time.Now().Unix()

	// A row written before adventure alerts existed carries watermark 0, which
	// read literally means "has never been told about anything" and would page the
	// subscriber for the entire history of the realm on the first tick after
	// deploy. Stamp those to now and let them start from the next dispatch. This
	// is the deploy-safety valve for the whole phase.
	live := subs[:0]
	for _, sub := range subs {
		if sub.LastAdvNotifiedAt == 0 {
			if err := storage.TouchAdvPushSubscription(sub.Endpoint, now); err != nil {
				slog.Error("adv-push: seed watermark failed", "sub", sub.UserSub, "err", err)
			}
			continue
		}
		live = append(live, sub)
	}
	if len(live) == 0 {
		return
	}

	// One scan serves every subscriber: read from the oldest watermark in the set
	// and let each row be filtered per subscription below.
	oldest := live[0].LastAdvNotifiedAt
	for _, sub := range live {
		if sub.LastAdvNotifiedAt < oldest {
			oldest = sub.LastAdvNotifiedAt
		}
	}
	events, err := storage.AdvEventsSince(oldest, advAlertScan)
	if err != nil {
		slog.Error("adv-push: scan dispatches failed", "err", err)
		return
	}
	if len(events) == 0 {
		return
	}
	if len(events) == advAlertScan {
		// The scan was capped, so dispatches older than the window exist and are
		// about to be skipped by the watermark advance below. Alerts are
		// time-sensitive enough that dropping the tail is right; being quiet about
		// it is not.
		slog.Warn("adv-push: scan hit its cap; older dispatches skipped",
			"cap", advAlertScan, "since", oldest)
	}
	// events[0] is the newest in the window (occurred_at DESC) and is where every
	// watermark lands this pass, sent or not.
	newest := events[0].OccurredAt

	// Both lookups are per-user, and a user can hold several endpoints (phone,
	// desktop). Cache within the pass so a two-device user costs one prefs parse
	// and one ownership join rather than two.
	catsByUser := make(map[string]map[string]bool)
	nameByLocalpart := make(map[string]string)

	sent, pruned := 0, 0
	for _, sub := range live {
		cats, ok := catsByUser[sub.UserSub]
		if !ok {
			cats = advCategoriesFor(sub.UserSub)
			catsByUser[sub.UserSub] = cats
		}
		if len(cats) == 0 {
			// Nothing enabled. Still advance, so turning a category on later starts
			// from that moment rather than replaying the backlog it was off for.
			s.touchAdv(sub.Endpoint, newest)
			continue
		}

		// The ownership join is re-read every pass rather than trusted from the
		// subscription row, and that is deliberate: an opt-out, a removal or a
		// character change has to close the channel immediately, exactly as
		// runReportLinkFor re-resolves rather than trusting a stored id.
		mine := ""
		if sub.Localpart != "" {
			if cached, ok := nameByLocalpart[sub.Localpart]; ok {
				mine = cached
			} else {
				if name, ok := storage.AdvCharacterForOwner(sub.Localpart); ok {
					mine = name
				}
				nameByLocalpart[sub.Localpart] = mine
			}
		}

		var top *advAlert
		extra := 0
		for _, ev := range events {
			if ev.OccurredAt <= sub.LastAdvNotifiedAt {
				continue // this endpoint has already been told
			}
			alert, ok := advAlertFor(ev, mine)
			if !ok || !cats[alert.Category] {
				continue
			}
			if top == nil {
				// events are newest-first, so the first match is the newest match.
				a := alert
				top = &a
				continue
			}
			extra++
		}
		if top == nil {
			s.touchAdv(sub.Endpoint, newest)
			continue
		}

		gone, err := s.sendPush(sub, buildAdvPayload(*top, extra))
		if gone {
			if derr := storage.RemovePushSubscription(sub.Endpoint); derr != nil {
				slog.Error("adv-push: prune gone subscription failed", "err", derr)
			} else {
				pruned++
			}
			continue
		}
		if err != nil {
			// Leave the watermark alone: a transient push-service failure should be
			// retried on the next tick, not swallowed. The alert is at most
			// advAlertInterval late, and the events are still in the window.
			slog.Warn("adv-push: send failed", "sub", sub.UserSub, "err", err)
			continue
		}
		s.touchAdv(sub.Endpoint, newest)
		sent++
	}
	if sent > 0 || pruned > 0 {
		slog.Info("adv-push: pass complete", "sent", sent, "pruned", pruned, "subscriptions", len(live))
	}
}

func (s *Server) touchAdv(endpoint string, ts int64) {
	if err := storage.TouchAdvPushSubscription(endpoint, ts); err != nil {
		slog.Error("adv-push: advance watermark failed", "endpoint", endpoint, "err", err)
	}
}

// advAlertFor decides whether one dispatch is worth waking somebody for, and in
// what words. mine is the character name belonging to the subscriber, or "" when
// Pete cannot establish one — in which case only realm-wide alerts can match.
//
// Every owner-scoped branch compares against mine and nothing else. There is no
// path here where an unresolved owner falls through to a broadcast: a game alert
// naming somebody's adventurer, delivered to the wrong phone, is a privacy leak
// dressed as a feature.
func advAlertFor(ev storage.AdvEvent, mine string) (advAlert, bool) {
	switch ev.EventType {
	case "siege_start":
		boss := ev.Boss
		if boss == "" {
			boss = "Something"
		}
		return advAlert{
			Category: advCatSiege,
			Title:    "The Siege has begun",
			Body:     fmt.Sprintf("%s is camped outside the town. Everyone gets one bout a day.", boss),
			URL:      "/adventure/siege",
		}, true
	case "siege_win":
		return advAlert{
			Category: advCatSiege,
			Title:    "The town holds",
			Body:     siegeOutcomeBody(ev, "went down"),
			URL:      "/adventure/siege",
		}, true
	case "siege_loss":
		return advAlert{
			Category: advCatSiege,
			Title:    "The Siege is over",
			Body:     siegeOutcomeBody(ev, "walked away still standing"),
			URL:      "/adventure/siege",
		}, true
	}

	// Everything below is about one person, so an unmatched subject ends it here.
	if mine == "" || ev.Subject != mine {
		return advAlert{}, false
	}

	switch ev.EventType {
	case "death":
		return advAlert{
			Category: advCatRun,
			Title:    fmt.Sprintf("%s fell in %s", mine, orPlace(ev.Zone)),
			Body:     "The expedition is over. They'll need picking up.",
			URL:      advRunOrStoryURL(ev),
		}, true
	case "zone_clear":
		return advAlert{
			Category: advCatRun,
			Title:    fmt.Sprintf("%s cleared %s", mine, orPlace(ev.Zone)),
			Body:     "They're through it and on the way home. Read how it went.",
			URL:      advRunOrStoryURL(ev),
		}, true
	case "retreat":
		return advAlert{
			Category: advCatRun,
			Title:    fmt.Sprintf("%s backed out of %s", mine, orPlace(ev.Zone)),
			Body:     "Everyone came home breathing. The run's finished either way.",
			URL:      advRunOrStoryURL(ev),
		}, true
	case "departure":
		return advAlert{
			Category: advCatDeparture,
			Title:    fmt.Sprintf("%s got bored and left", mine),
			Body: fmt.Sprintf("No orders, no escort. They packed the cheap kit and set off into %s on their own.",
				orPlace(ev.Zone)),
			URL: advStoryURL(ev.GUID),
		}, true
	case "mischief_contract":
		body := "Somebody paid to have something sent after them, and isn't saying who. Survive it and the money's theirs."
		if ev.Opponent != "" {
			body = fmt.Sprintf("%s paid for it and signed the thing. It's out there looking right now.", ev.Opponent)
		}
		return advAlert{
			Category: advCatContract,
			Title:    fmt.Sprintf("There's a contract out on %s", mine),
			Body:     body,
			URL:      advStoryURL(ev.GUID),
		}, true
	}
	return advAlert{}, false
}

// siegeOutcomeBody names the boss when the fact carried one. The verb differs by
// outcome, so it is the caller's.
func siegeOutcomeBody(ev storage.AdvEvent, verb string) string {
	if ev.Boss == "" {
		return fmt.Sprintf("It %s. See how the town did.", verb)
	}
	return fmt.Sprintf("%s %s. See how the town did.", ev.Boss, verb)
}

func orPlace(zone string) string {
	if zone == "" {
		return "the dark"
	}
	return zone
}

// advRunOrStoryURL prefers the run report, which is the richer landing place for
// an expedition that has just ended, and falls back to the dispatch permalink.
// Runs that predate the liveblog carry no run id and land on the story, which is
// what they have always done.
func advRunOrStoryURL(ev storage.AdvEvent) string {
	if ev.RunID != "" {
		return runReportPath(ev.RunID)
	}
	return advStoryURL(ev.GUID)
}

// advStoryURL is advPermalink's relative half, and it escapes for the same
// reason: the guid arrives over a wire, and one that grew a slash would send the
// notification somewhere else entirely.
func advStoryURL(guid string) string {
	return "/adventure/" + url.PathEscape(guid)
}

// buildAdvPayload renders the notification JSON the service worker expects. The
// tag is per-category so a Siege alert can't silently replace an unread alert
// about somebody's own adventurer on the lock screen.
func buildAdvPayload(a advAlert, extra int) []byte {
	body := a.Body
	if extra == 1 {
		body += " Plus 1 other update."
	} else if extra > 1 {
		body += fmt.Sprintf(" Plus %d other updates.", extra)
	}
	b, _ := json.Marshal(map[string]string{
		"title": a.Title,
		"body":  body,
		"url":   a.URL,
		"tag":   "pete-adv-" + a.Category,
	})
	return b
}

// advCategoriesFor returns the alert categories a user has switched on. An
// absent key, an unparseable blob or a user who has never opened the settings
// drawer all yield an empty set, which sends nothing — the safe direction for a
// channel that interrupts people.
func advCategoriesFor(sub string) map[string]bool {
	return userPrefBoolSet(sub, advPrefsKey)
}

// userPrefBoolSet reads one {name: bool} map out of a user's stored preferences
// blob, keeping only the true entries.
//
// The blob mirrors localStorage: a JSON object whose values are themselves JSON
// *strings*. That double encoding is the client's doing, not ours, so unwrap it
// — while tolerating a bare object, since a hand-written or migrated blob may
// carry one. Any parse failure yields an empty set, and every caller treats an
// empty set as "no", so a corrupt blob costs a feature rather than misfiring it.
func userPrefBoolSet(sub, key string) map[string]bool {
	out := map[string]bool{}
	blob, err := storage.GetUserPrefs(sub)
	if err != nil || blob == "" {
		return out
	}
	var prefs map[string]json.RawMessage
	if err := json.Unmarshal([]byte(blob), &prefs); err != nil {
		return out
	}
	raw, ok := prefs[key]
	if !ok {
		return out
	}
	inner := []byte(raw)
	var asStr string
	if err := json.Unmarshal(raw, &asStr); err == nil {
		inner = []byte(asStr)
	}
	var set map[string]bool
	if err := json.Unmarshal(inner, &set); err != nil {
		return out
	}
	for name, on := range set {
		if on {
			out[strings.TrimSpace(name)] = true
		}
	}
	return out
}