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package casino
import (
"fmt"
"math"
"math/rand"
)
type SlotSymbol struct {
ID string `yaml:"id"`
Weight int `yaml:"weight"`
Payout map[int]float64 `yaml:"payout"`
}
type SlotProfile struct {
Symbols []SlotSymbol `yaml:"symbols"`
Rows int `yaml:"rows"`
Reels int `yaml:"reels"`
FreeSpinTrigger string `yaml:"free_spin_trigger"`
FreeSpinCount int `yaml:"free_spin_count"`
Ways int `yaml:"ways"`
TargetRTP float64 `yaml:"payout"`
}
type SlotSpin struct {
Grid [3][5]string
Payout float64
ScatterCount int
Wins []SlotWin
}
type SlotWin struct {
Symbol string
Length int
Ways int
Multiplier float64
Payout float64
}
func DefaultHuffAndPuffProfile() SlotProfile {
return SlotProfile{
Rows: 3, Reels: 5, Ways: 243,
FreeSpinTrigger: "scatter", FreeSpinCount: 8,
Symbols: []SlotSymbol{
{ID: "straw", Weight: 22, Payout: map[int]float64{3: .5, 4: 1, 5: 2}},
{ID: "stick", Weight: 12, Payout: map[int]float64{3: 1, 4: 2, 5: 5}},
{ID: "brick", Weight: 7, Payout: map[int]float64{3: 2, 4: 5, 5: 15}},
{ID: "hat", Weight: 4, Payout: map[int]float64{3: 5, 4: 15, 5: 50}},
{ID: "wolf", Weight: 2, Payout: map[int]float64{3: 10, 4: 50, 5: 250}},
{ID: "scatter", Weight: 3},
},
}
}
func (p SlotProfile) Normalize() SlotProfile {
if p.Rows <= 0 {
p.Rows = 3
}
if p.Reels <= 0 {
p.Reels = 5
}
if p.Ways <= 0 {
p.Ways = 243
}
if p.FreeSpinCount <= 0 {
p.FreeSpinCount = 8
}
if len(p.Symbols) == 0 {
return DefaultHuffAndPuffProfile()
}
return p
}
func (p SlotProfile) symbol(id string) *SlotSymbol {
for i := range p.Symbols {
if p.Symbols[i].ID == id {
return &p.Symbols[i]
}
}
return nil
}
func generateSlotSpinWithProfile(rng *rand.Rand, bet int, profile SlotProfile) *SlotSpin {
p := profile.Normalize()
spin := &SlotSpin{}
for reel := 0; reel < p.Reels && reel < 5; reel++ {
for row := 0; row < p.Rows && row < 3; row++ {
symbol := weightedSymbol(rng, p.Symbols)
spin.Grid[row][reel] = symbol
if symbol == p.FreeSpinTrigger {
spin.ScatterCount++
}
}
}
spin.Payout, spin.Wins = evaluateSlot(spin.Grid, bet, p)
return spin
}
func weightedSymbol(rng *rand.Rand, symbols []SlotSymbol) string {
total := 0
for _, symbol := range symbols {
if symbol.Weight > 0 {
total += symbol.Weight
}
}
if total <= 0 {
return ""
}
n := rng.Intn(total)
for _, symbol := range symbols {
if symbol.Weight <= 0 {
continue
}
if n < symbol.Weight {
return symbol.ID
}
n -= symbol.Weight
}
return symbols[len(symbols)-1].ID
}
func evaluateSlot(grid [3][5]string, bet int, profile SlotProfile) (float64, []SlotWin) {
p := profile.Normalize()
if bet <= 0 {
return 0, nil
}
total := 0.0
var wins []SlotWin
for _, symbol := range p.Symbols {
length, ways := matchingLength(grid, symbol.ID)
if length >= 3 && symbol.Payout[length] > 0 {
payout := float64(bet) * symbol.Payout[length] * float64(ways) / float64(p.Ways)
total += payout
wins = append(wins, SlotWin{Symbol: symbol.ID, Length: length, Ways: ways, Multiplier: symbol.Payout[length], Payout: payout})
}
}
return total, wins
}
func matchingLength(grid [3][5]string, symbol string) (int, int) {
ways := 1
length := 0
for reel := 0; reel < 5; reel++ {
count := 0
for row := 0; row < 3; row++ {
if grid[row][reel] == symbol {
count++
}
}
if count == 0 {
break
}
ways *= count
length = reel + 1
}
if length < 3 {
return length, 0
}
return length, ways
}
// CalculateRTP returns the exact mathematical RTP for the independent-cell
// model used by the baseline machine, before integer-credit rounding.
func CalculateRTP(profile SlotProfile) float64 {
p := profile.Normalize()
totalWeight := 0
for _, symbol := range p.Symbols {
if symbol.Weight > 0 {
totalWeight += symbol.Weight
}
}
if totalWeight == 0 {
return 0
}
baseRTP := 0.0
scatterProbability := 0.0
for _, symbol := range p.Symbols {
probability := float64(symbol.Weight) / float64(totalWeight)
if symbol.ID == p.FreeSpinTrigger {
scatterProbability = probability
}
if symbol.ID == p.FreeSpinTrigger {
continue
}
for length := 3; length <= 5; length++ {
ways := math.Pow(float64(p.Rows), float64(length))
nextReelNoMatch := 1.0
if length < 5 {
nextReelNoMatch = math.Pow(1-probability, float64(p.Rows))
}
baseRTP += symbol.Payout[length] * ways * math.Pow(probability, float64(length)) * nextReelNoMatch / float64(p.Ways)
}
}
// The baseline feature awards a fixed number of automatic spins and does
// not retrigger during those spins. Its expected value is therefore the
// trigger probability multiplied by the free-spin count and base RTP.
triggerProbability := 0.0
for scatters := 3; scatters <= p.Rows*p.Reels; scatters++ {
triggerProbability += binomial(p.Rows*p.Reels, scatters) * math.Pow(scatterProbability, float64(scatters)) * math.Pow(1-scatterProbability, float64(p.Rows*p.Reels-scatters))
}
return baseRTP * (1 + triggerProbability*float64(p.FreeSpinCount))
}
func binomial(n, k int) float64 {
if k < 0 || k > n {
return 0
}
result := 1.0
for i := 1; i <= k; i++ {
result *= float64(n-k+i) / float64(i)
}
return result
}
func ValidateRTP(profile SlotProfile, tolerance float64) error {
if profile.TargetRTP <= 0 {
return nil
}
actual := CalculateRTP(profile)
if math.Abs(actual-profile.TargetRTP) > tolerance {
return fmt.Errorf("slot profile RTP %.6f does not match target %.6f", actual, profile.TargetRTP)
}
return nil
}
// ScaleToRTP adjusts the configured paytable, without changing reel weights or
// feature probabilities, so the profile's exact mathematical RTP reaches the
// requested target. Runtime payouts retain fractional credits internally until
// they can be paid as whole credits.
func ScaleToRTP(profile SlotProfile, target float64) SlotProfile {
profile = profile.Normalize()
actual := CalculateRTP(profile)
if actual <= 0 || target <= 0 {
return profile
}
scale := target / actual
for i := range profile.Symbols {
for length, payout := range profile.Symbols[i].Payout {
profile.Symbols[i].Payout[length] = payout * scale
}
}
profile.TargetRTP = target
return profile
}
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