package web

import (
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"sort"
	"time"

	"pete/internal/storage"
)

// The realm pages: the world map, the board, and the hall of firsts.
//
// Everything Pete has published so far is either the present moment (the roster,
// the Siege bar) or one thing that happened (a dispatch, a run report). None of
// it says what this place IS. A visitor who reads every dispatch on the site
// still cannot answer "how many zones are there", "is the Drowned Star harder
// than the Sunken Vault", or "has anybody ever actually beaten it" — and those
// are the questions that turn a feed of incidents into a world.
//
// The three pages are one snapshot because they are one question. Every number
// on all three comes off the same scan of the same run history on the game box;
// splitting the wire would mean three ways for the same fact to disagree with
// itself depending on which page you were standing on.
//
// The map is deliberately NOT who_map.go's layout engine, which the plan
// expected it to be. That engine lays out a *graph* — nodes joined by edges, at
// BFS depth from an entrance — and the realm has no edges. Zones are not
// connected to each other; you pick one from town and go. Forcing a graph layout
// onto a set would have produced a picture that implied a topology the game does
// not have. What the realm has instead is an *order*, by difficulty, and that is
// what gets drawn: tier bands, hardest last.

const (
	// realmStaleAfter — how old the snapshot may get before the pages stop
	// claiming the occupant dots are live. gogobee recomputes the realm every ten
	// minutes rather than every two (it is aggregate scans over the whole run
	// history, and a first clear does not move), so the window is proportionally
	// wider: several missed pushes, not one unlucky one.
	realmStaleAfter = 45 * time.Minute

	// Payload bounds. A realm has tens of zones, tens of players, and a first per
	// zone plus a first per treasure; these only stop a malformed or hostile push
	// spooling unbounded rows.
	realmMaxZones     = 500
	realmMaxFirsts    = 5000
	realmMaxStandings = 1000
)

// realmPush is the payload gogobee POSTs to /api/ingest/realm.
type realmPush struct {
	SnapshotAt int64 `json:"snapshot_at"`
	storage.Realm
}

// RealmZoneView is one zone as the map draws it: gogobee's facts plus the few
// presentational calls Pete is allowed to make.
type RealmZoneView struct {
	storage.RealmZone
	Cleared   bool   // anybody, ever
	Unbeaten  bool   // nobody, ever — the ominous state
	FirstWhen string // "Mar 4, 2026", empty when unknown
	Levels    string // "levels 5–8", or "level 5" when the band is one wide
	Busy      bool   // somebody is in there right now
}

// RealmTierView is one difficulty band of the map. The band is the unit the page
// draws in, because difficulty order is the only real structure the realm has.
type RealmTierView struct {
	Tier     int
	Label    string
	Blurb    string
	Postgame bool
	Zones    []RealmZoneView
	Cleared  int // zones in this band somebody has beaten
}

// RealmView is the map page.
type RealmView struct {
	Known        bool // gogobee has pushed at least one snapshot
	Stale        bool
	Tiers        []RealmTierView
	ZoneCount    int
	ClearedZones int
	Unbeaten     int
	OutThere     int // adventurers on expedition right now, across the whole realm
	SnapshotAt   int64
	LastSeenAgo  string
}

// RealmStandingView is one line of the board.
type RealmStandingView struct {
	storage.RealmStanding
	Rank   int
	Deaths int // Pete's own count, from the dispatches he filed — see DeathsBySubject
}

// StandingsView is the board page.
type StandingsView struct {
	Known       bool
	Stale       bool
	Rows        []RealmStandingView
	PeteWins    int
	PeteLosses  int
	PeteFought  bool // he has a record at all; zero-zero renders as "no bouts yet"
	SnapshotAt  int64
	LastSeenAgo string
}

// RealmFirstView is one entry in the hall.
type RealmFirstView struct {
	storage.RealmFirst
	When  string
	Kind  string // the raw kind, kept for the CSS hook
	Label string // "First through" / "First to hold" — reads as a sentence
}

// FirstsView is the hall of firsts page, grouped by year so a long ledger reads
// as a history rather than as a list.
type FirstsView struct {
	Known       bool
	Stale       bool
	Years       []RealmFirstYear
	Total       int
	Zones       int
	Others      int
	SnapshotAt  int64
	LastSeenAgo string
}

// RealmFirstYear is one year's worth of firsts, newest year first.
type RealmFirstYear struct {
	Year   int
	Firsts []RealmFirstView
}

type realmPage struct {
	pageData
	Realm RealmView
}

type standingsPage struct {
	pageData
	Standings StandingsView
}

type firstsPage struct {
	pageData
	Firsts FirstsView
}

// realmTierLabels names the difficulty bands. gogobee's zone tiers are 1–6 and
// the sixth is the postgame; the labels are the game's own words for them.
var realmTierLabels = map[int]struct{ label, blurb string }{
	1: {"Tier I · The Outskirts", "Where everybody starts. Close enough to town to walk back from."},
	2: {"Tier II · The Reaches", "Further out, and the road stops being a road."},
	3: {"Tier III · The Deep Country", "Long enough that you camp. Bring supplies you don't think you'll need."},
	4: {"Tier IV · The Far Places", "Multi-region crossings. People come back from these different."},
	5: {"Tier V · The Last Doors", "The end of the map as it was drawn. Very few have seen all of these."},
	6: {"Mythic · The Postgame", "Sealed until you're level 18 and have put down both Tier V bosses. It does not get easier past here."},
}

// handleRealmIngest replaces the realm with gogobee's latest snapshot.
func (s *Server) handleRealmIngest(w http.ResponseWriter, r *http.Request) {
	if !s.adv.Enabled {
		http.NotFound(w, r)
		return
	}
	if !s.bearerOK(r) {
		http.Error(w, "unauthorized", http.StatusUnauthorized)
		return
	}

	var push realmPush
	if err := json.NewDecoder(io.LimitReader(r.Body, 4<<20)).Decode(&push); err != nil {
		http.Error(w, "bad json", http.StatusBadRequest)
		return
	}
	if len(push.Zones) > realmMaxZones {
		http.Error(w, "zone list too large", http.StatusBadRequest)
		return
	}
	if len(push.Firsts) > realmMaxFirsts {
		http.Error(w, "firsts ledger too large", http.StatusBadRequest)
		return
	}
	if len(push.Standings) > realmMaxStandings {
		http.Error(w, "standings too large", http.StatusBadRequest)
		return
	}
	if push.SnapshotAt <= 0 {
		push.SnapshotAt = time.Now().Unix()
	}

	// Never trust the channel with a name. A nameless row renders as a blank line
	// on a public page, so it is rejected rather than drawn — the same rule the
	// siege muster applies to its defenders.
	for i, z := range push.Zones {
		if z.ID == "" || z.Display == "" {
			http.Error(w, fmt.Sprintf("zone %d: id and display are required", i), http.StatusBadRequest)
			return
		}
		for j, o := range z.Occupants {
			if o.Name == "" {
				http.Error(w, fmt.Sprintf("zone %d occupant %d: name is required", i, j), http.StatusBadRequest)
				return
			}
		}
	}
	for i, st := range push.Standings {
		if st.Name == "" {
			http.Error(w, fmt.Sprintf("standing %d: name is required", i), http.StatusBadRequest)
			return
		}
	}
	// A first with no display would render as an empty row in the history book.
	// Unlike a name this one Pete can repair himself — gogobee already falls back
	// to the raw target for a kind it has no words for, and doing the same here
	// means a future first kind can never blank a row.
	for i := range push.Firsts {
		if push.Firsts[i].Display == "" {
			push.Firsts[i].Display = push.Firsts[i].Target
		}
		if push.Firsts[i].Display == "" {
			http.Error(w, fmt.Sprintf("first %d: target is required", i), http.StatusBadRequest)
			return
		}
	}

	if err := storage.ReplaceRealm(push.Realm, push.SnapshotAt); err != nil {
		slog.Error("realm ingest: replace failed", "err", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	slog.Info("realm ingest: realm replaced",
		"zones", len(push.Zones), "firsts", len(push.Firsts), "standings", len(push.Standings))
	w.WriteHeader(http.StatusOK)
}

// loadRealmSnapshot reads the snapshot once and reports staleness. All three
// pages go through it so they can never disagree about how old the realm is.
func (s *Server) loadRealmSnapshot() (storage.Realm, bool, bool) {
	snap, known, err := storage.LoadRealm()
	if err != nil {
		slog.Error("realm: load failed", "err", err)
		return storage.Realm{}, false, true
	}
	stale := !known || snap.SnapshotAt == 0 ||
		time.Since(time.Unix(snap.SnapshotAt, 0)) > realmStaleAfter
	return snap, known, stale
}

// handleRealmPage serves the world map.
func (s *Server) handleRealmPage(w http.ResponseWriter, r *http.Request) {
	if !s.adv.Enabled {
		http.NotFound(w, r)
		return
	}
	s.track(r, "adventure")
	base := s.base(r)
	base.Active = "adventure"
	s.render(w, "realm", realmPage{pageData: base, Realm: s.realm()})
}

// realm builds the map view.
func (s *Server) realm() RealmView {
	snap, known, stale := s.loadRealmSnapshot()
	v := RealmView{Known: known, Stale: stale, SnapshotAt: snap.SnapshotAt}
	if snap.SnapshotAt > 0 {
		v.LastSeenAgo = shortTimeAgo(time.Unix(snap.SnapshotAt, 0))
	}

	byTier := map[int][]RealmZoneView{}
	for _, z := range snap.Zones {
		zv := RealmZoneView{
			RealmZone: z,
			// Cleared is Clears > 0, NOT "FirstClearBy is set". The two come
			// apart exactly when the first clearer opted out: the zone has been
			// beaten and the claim stands, it just has no name on it. Keying the
			// ominous never-beaten styling off the name would make an
			// anonymisation look like a fact about the world.
			Cleared: z.Clears > 0,
			Busy:    len(z.Occupants) > 0,
			Levels:  levelBand(z.LevelMin, z.LevelMax),
		}
		zv.Unbeaten = !zv.Cleared
		if z.FirstClearAt > 0 {
			zv.FirstWhen = time.Unix(z.FirstClearAt, 0).UTC().Format("Jan 2, 2006")
		}
		byTier[z.Tier] = append(byTier[z.Tier], zv)

		v.ZoneCount++
		if zv.Cleared {
			v.ClearedZones++
		} else {
			v.Unbeaten++
		}
		v.OutThere += len(z.Occupants)
	}

	tiers := make([]int, 0, len(byTier))
	for t := range byTier {
		tiers = append(tiers, t)
	}
	sort.Ints(tiers)
	for _, t := range tiers {
		tv := RealmTierView{Tier: t, Zones: byTier[t], Postgame: t >= 6}
		if lbl, ok := realmTierLabels[t]; ok {
			tv.Label, tv.Blurb = lbl.label, lbl.blurb
		} else {
			// A tier the labels don't know about still draws, with an honest
			// generic heading rather than an empty one. Same degrade-don't-drop
			// rule as an untemplated dispatch.
			tv.Label = fmt.Sprintf("Tier %d", t)
		}
		for _, z := range tv.Zones {
			if z.Cleared {
				tv.Cleared++
			}
		}
		v.Tiers = append(v.Tiers, tv)
	}
	return v
}

// handleStandingsPage serves the board.
func (s *Server) handleStandingsPage(w http.ResponseWriter, r *http.Request) {
	if !s.adv.Enabled {
		http.NotFound(w, r)
		return
	}
	s.track(r, "adventure")
	base := s.base(r)
	base.Active = "adventure"
	s.render(w, "standings", standingsPage{pageData: base, Standings: s.standings()})
}

// standings builds the board view.
//
// The rank is gogobee's push order, not anything computed here: the ordering
// ("deepest tier beaten, then how much of the realm you have beaten") is a
// statement about what the game values, and the game is the thing entitled to
// make it. Pete's job is to draw it and to add the two columns the game box
// cannot answer — the death count and Pete's own record.
func (s *Server) standings() StandingsView {
	snap, known, stale := s.loadRealmSnapshot()
	v := StandingsView{Known: known, Stale: stale, SnapshotAt: snap.SnapshotAt}
	if snap.SnapshotAt > 0 {
		v.LastSeenAgo = shortTimeAgo(time.Unix(snap.SnapshotAt, 0))
	}

	deaths, err := storage.DeathsBySubject()
	if err != nil {
		// A missing death column is a missing column. It is not worth failing the
		// whole board over, and a zero would be a lie, so the template renders a
		// dash for anyone not in the map — which is what an absent map produces.
		slog.Error("standings: death counts", "err", err)
		deaths = nil
	}
	for i, st := range snap.Standings {
		v.Rows = append(v.Rows, RealmStandingView{
			RealmStanding: st,
			Rank:          i + 1,
			Deaths:        deaths[st.Name],
		})
	}

	if w, l, err := storage.PeteDuelRecord(); err != nil {
		slog.Error("standings: pete duel record", "err", err)
	} else {
		v.PeteWins, v.PeteLosses = w, l
		v.PeteFought = w+l > 0
	}
	return v
}

// handleFirstsPage serves the hall of firsts.
func (s *Server) handleFirstsPage(w http.ResponseWriter, r *http.Request) {
	if !s.adv.Enabled {
		http.NotFound(w, r)
		return
	}
	s.track(r, "adventure")
	base := s.base(r)
	base.Active = "adventure"
	s.render(w, "firsts", firstsPage{pageData: base, Firsts: s.firsts()})
}

// firsts builds the hall.
//
// gogobee pushes the ledger oldest-first, which is the order it happened in. The
// page reverses it into newest-year-first, because a history book that opens on
// the oldest page is an archive and this is meant to read as "look what has been
// happening" — but within a year it stays chronological, so a year reads forward
// the way a year did.
func (s *Server) firsts() FirstsView {
	snap, known, stale := s.loadRealmSnapshot()
	v := FirstsView{Known: known, Stale: stale, SnapshotAt: snap.SnapshotAt}
	if snap.SnapshotAt > 0 {
		v.LastSeenAgo = shortTimeAgo(time.Unix(snap.SnapshotAt, 0))
	}

	byYear := map[int][]RealmFirstView{}
	for _, f := range snap.Firsts {
		fv := RealmFirstView{RealmFirst: f, Kind: f.Kind}
		switch f.Kind {
		case "zone":
			fv.Label = "First through"
		case "treasure":
			fv.Label = "First to hold"
		default:
			fv.Label = "First"
		}
		year := 0
		if f.AtUnix > 0 {
			t := time.Unix(f.AtUnix, 0).UTC()
			fv.When = t.Format("Jan 2, 2006")
			year = t.Year()
		}
		byYear[year] = append(byYear[year], fv)

		v.Total++
		if f.Kind == "zone" {
			v.Zones++
		} else {
			v.Others++
		}
	}

	years := make([]int, 0, len(byYear))
	for y := range byYear {
		years = append(years, y)
	}
	// Newest year first. Year 0 is "the ledger has no date for this", which
	// sorts last — an undated first is real but it is not news.
	sort.Sort(sort.Reverse(sort.IntSlice(years)))
	for _, y := range years {
		v.Years = append(v.Years, RealmFirstYear{Year: y, Firsts: byYear[y]})
	}
	return v
}

// levelBand renders a zone's level range as words. A one-wide band ("levels
// 5–5") reads as a typo, so it collapses to "level 5"; a band with no numbers at
// all renders as nothing rather than as "levels 0–0".
func levelBand(min, max int) string {
	switch {
	case min <= 0 && max <= 0:
		return ""
	case min == max:
		return fmt.Sprintf("level %d", min)
	case min <= 0:
		return fmt.Sprintf("up to level %d", max)
	case max <= 0:
		return fmt.Sprintf("level %d and up", min)
	default:
		return fmt.Sprintf("levels %d–%d", min, max)
	}
}