games: a ladder you climb against the clock

internal/web/games_trivia.go

@@ -0,0 +1,224 @@
+package web
+
+import (
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"math/rand/v2"
+	"net/http"
+	"time"
+
+	"pete/internal/games/blackjack"
+	"pete/internal/games/trivia"
+	"pete/internal/storage"
+)
+
+// Trivia, played for chips.
+//
+// The same shape as the other tables: the browser sends intents, the server
+// holds the state, and the payload carries only what the player is entitled to
+// see. Here that means the four answers *without* which of them is right. The
+// right one is an index in the engine state, which is in game_live_hands, on
+// this side of the wire — and it only ever crosses in the event that reveals it,
+// once the question has been decided and it can't be used to answer.
+//
+// The clock is the other half. The countdown in the browser is decoration: the
+// only clock that scores anything is time.Now() here, measured against the
+// AskedAt the server stamped when it served the question. A player who stops
+// their own countdown, or reloads to restart it, changes nothing.
+
+// triviaView is a game as its player may see it.
+type triviaView struct {
+	Tier  trivia.Tier `json:"tier"`
+	Rung  int         `json:"rung"`  // how many they've answered
+	Rungs int         `json:"rungs"` // how many there are
+
+	Category string   `json:"category,omitempty"`
+	Question string   `json:"question,omitempty"`
+	Answers  []string `json:"answers,omitempty"` // and *not* which one is right
+
+	Limit int     `json:"limit"` // the tier's seconds per question
+	Left  float64 `json:"left"`  // seconds this question has left, by the server's clock
+
+	Multiple float64 `json:"multiple"`
+	Bet      int64   `json:"bet"`
+	Stands   int64   `json:"stands"`   // what taking the money right now actually pays
+	CanWalk  bool    `json:"can_walk"` // false on the first question: see the engine
+
+	Phase   string `json:"phase"`
+	Outcome string `json:"outcome,omitempty"`
+	Payout  int64  `json:"payout,omitempty"`
+	Rake    int64  `json:"rake,omitempty"`
+	Net     int64  `json:"net"`
+}
+
+func viewTrivia(g trivia.State, now time.Time) triviaView {
+	v := triviaView{
+		Tier:  g.Tier,
+		Rung:  g.Rung,
+		Rungs: trivia.Rungs,
+		Limit: g.Tier.Limit,
+		// What the player would actually collect, rake already out of it — quoting
+		// the pre-rake figure would have the felt advertising a payout the house
+		// doesn't hand over.
+		Stands:   g.Pays(),
+		Multiple: g.Multiple,
+		Bet:      g.Bet,
+		CanWalk:  g.Rung > 0,
+		Phase:    string(g.Phase),
+		Outcome:  string(g.Outcome),
+		Payout:   g.Payout,
+		Rake:     g.Rake,
+		Net:      g.Net(),
+	}
+	// A finished game has no live question, and must not ship the next one — the
+	// ladder still has rungs on it that a later game might deal.
+	if g.Phase == trivia.PhasePlaying {
+		q := g.Live()
+		v.Category = q.Category
+		v.Question = q.Text
+		v.Answers = q.Answers
+		v.Left = g.Left(now).Seconds()
+	}
+	return v
+}
+
+// handleTriviaStart takes the bet and builds a ladder. Same order as every other
+// table: the chips are staked first, in the same statement that checks they
+// exist, so two starts fired at once cannot bet the same chip.
+func (s *Server) handleTriviaStart(w http.ResponseWriter, r *http.Request) {
+	user, ok := s.player(w, r)
+	if !ok {
+		return
+	}
+	var req struct {
+		Bet  int64  `json:"bet"`
+		Tier string `json:"tier"`
+	}
+	if err := decodeJSON(r, &req); err != nil || req.Bet <= 0 {
+		writeJSONStatus(w, http.StatusBadRequest, map[string]string{"error": "bet something"})
+		return
+	}
+	tier, err := trivia.TierBySlug(req.Tier)
+	if err != nil {
+		writeJSONStatus(w, http.StatusBadRequest, map[string]string{"error": "pick a difficulty"})
+		return
+	}
+
+	seed1, seed2 := newSeeds()
+	rng := rand.New(rand.NewPCG(seed1, seed2))
+
+	// Draw the ladder *before* taking the money. A bank too thin to deal from is
+	// the one failure here that isn't the player's fault, and they should not have
+	// to be refunded for it.
+	qs, err := storage.DrawTrivia(tier.Difficulty, trivia.Rungs, rng)
+	if errors.Is(err, storage.ErrBankEmpty) {
+		writeJSONStatus(w, http.StatusServiceUnavailable, map[string]string{
+			"error": "the question bank is still filling up — give it a minute",
+		})
+		return
+	}
+	if err != nil {
+		slog.Error("games: trivia draw", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+
+	if err := storage.Stake(user, req.Bet); err != nil {
+		if errors.Is(err, storage.ErrInsufficientChips) || errors.Is(err, storage.ErrBadAmount) {
+			writeJSONStatus(w, http.StatusBadRequest, map[string]string{"error": "not enough chips for that bet"})
+			return
+		}
+		slog.Error("games: trivia stake", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+
+	now := time.Now()
+	g, evs, err := trivia.New(req.Bet, tier, blackjack.DefaultRules().RakePct, qs, now, rng)
+	if err != nil {
+		// The game never happened, so the stake never should have left.
+		_ = storage.Award(user, req.Bet)
+		slog.Error("games: trivia start", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	s.persistTrivia(w, user, g, evs, seed1, seed2, true, now)
+}
+
+// handleTriviaAnswer plays one move: pick an answer, or take the money.
+func (s *Server) handleTriviaAnswer(w http.ResponseWriter, r *http.Request) {
+	user, ok := s.player(w, r)
+	if !ok {
+		return
+	}
+	var move trivia.Move
+	if err := decodeJSON(r, &move); err != nil {
+		http.Error(w, "bad json", http.StatusBadRequest)
+		return
+	}
+
+	live, err := storage.LoadLiveHand(user)
+	if errors.Is(err, storage.ErrNoLiveHand) {
+		writeJSONStatus(w, http.StatusConflict, map[string]string{"error": "no game in progress"})
+		return
+	}
+	if err != nil {
+		slog.Error("games: trivia load", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	if live.Game != gameTrivia {
+		writeJSONStatus(w, http.StatusConflict, map[string]string{"error": "finish the game you're in first"})
+		return
+	}
+	var g trivia.State
+	if err := json.Unmarshal(live.State, &g); err != nil {
+		slog.Error("games: unreadable trivia game", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+
+	// The server's clock, and the only one that counts. Read once, so the answer
+	// and the view that reports it agree about what time it is.
+	now := time.Now()
+
+	next, evs, err := trivia.ApplyMove(g, move, now)
+	if err != nil {
+		msg := "that move isn't legal here"
+		if errors.Is(err, trivia.ErrNothingBanked) {
+			msg = "answer one before you walk"
+		}
+		writeJSONStatus(w, http.StatusBadRequest, map[string]string{"error": msg})
+		return
+	}
+	s.persistTrivia(w, user, next, evs, live.Seed1, live.Seed2, false, now)
+}
+
+// persistTrivia writes the game back and answers the browser.
+func (s *Server) persistTrivia(w http.ResponseWriter, user string, g trivia.State, evs []trivia.Event, seed1, seed2 uint64, fresh bool, now time.Time) {
+	blob, err := json.Marshal(g)
+	if err != nil {
+		slog.Error("games: marshal trivia", "user", user, "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	done := g.Phase == trivia.PhaseDone
+	v, ok := s.commit(w, user, finished{
+		Game: gameTrivia, Blob: blob,
+		Bet: g.Bet, Payout: g.Payout, Rake: g.Rake,
+		Outcome: string(g.Outcome), Done: done,
+		Seed1: seed1, Seed2: seed2, Fresh: fresh,
+	})
+	if !ok {
+		return
+	}
+	// A finished game is gone from storage, so the table has none to show — but the
+	// browser still needs the final board to land the verdict on.
+	if done {
+		tv := viewTrivia(g, now)
+		v.Trivia = &tv
+	}
+	v.TrivEvents = evs
+	writeJSON(w, v)
+}