74 lines
2.1 KiB
Go
74 lines
2.1 KiB
Go
package gamedata
|
|
|
|
import (
|
|
"errors"
|
|
"math/big"
|
|
)
|
|
|
|
// gradePool conditions the actual nested weighted distribution on one grade.
|
|
// Exact rational path weights preserve branches with different child totals.
|
|
func (g RegularGacha) gradePool(grade uint64) ([]WeightedCostume, error) {
|
|
weights := map[uint64]*big.Rat{}
|
|
var walk func([]WeightedCostume, *big.Rat) error
|
|
walk = func(pool []WeightedCostume, path *big.Rat) error {
|
|
total := new(big.Int)
|
|
for _, item := range pool {
|
|
if item.Weight == 0 {
|
|
return errors.New("gamedata: zero costume weight")
|
|
}
|
|
total.Add(total, new(big.Int).SetUint64(item.Weight))
|
|
}
|
|
if total.Sign() == 0 {
|
|
return errors.New("gamedata: empty costume pool")
|
|
}
|
|
for _, item := range pool {
|
|
prob := new(big.Rat).Mul(path, new(big.Rat).SetFrac(new(big.Int).SetUint64(item.Weight), total))
|
|
if item.ID == 0 {
|
|
if err := walk(item.Children, prob); err != nil {
|
|
return err
|
|
}
|
|
continue
|
|
}
|
|
actual, ok := g.Grades[item.ID]
|
|
if !ok || actual < 3 || actual > 5 {
|
|
return errors.New("gamedata: costume grade unavailable")
|
|
}
|
|
if actual == grade {
|
|
if weights[item.ID] == nil {
|
|
weights[item.ID] = new(big.Rat)
|
|
}
|
|
weights[item.ID].Add(weights[item.ID], prob)
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
if err := walk(g.Pool, new(big.Rat).SetInt64(1)); err != nil {
|
|
return nil, err
|
|
}
|
|
denom := big.NewInt(1)
|
|
for _, weight := range weights {
|
|
gcd := new(big.Int).GCD(nil, nil, denom, weight.Denom())
|
|
denom.Mul(new(big.Int).Quo(denom, gcd), weight.Denom())
|
|
}
|
|
var ids []uint64
|
|
for id := range weights {
|
|
ids = append(ids, id)
|
|
}
|
|
// Stable table-independent ordering makes deterministic draw sources reproducible.
|
|
for i := 1; i < len(ids); i++ {
|
|
for j := i; j > 0 && ids[j] < ids[j-1]; j-- {
|
|
ids[j], ids[j-1] = ids[j-1], ids[j]
|
|
}
|
|
}
|
|
var out []WeightedCostume
|
|
for _, id := range ids {
|
|
w := weights[id]
|
|
count := new(big.Int).Mul(w.Num(), new(big.Int).Quo(new(big.Int).Set(denom), w.Denom()))
|
|
if !count.IsUint64() {
|
|
return nil, errors.New("gamedata: conditioned costume weight overflow")
|
|
}
|
|
out = append(out, WeightedCostume{ID: id, Weight: count.Uint64()})
|
|
}
|
|
return out, nil
|
|
}
|