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)
}