From 7c9bc46a3506d5722da7b0062b9b493f709fbb97 Mon Sep 17 00:00:00 2001
From: kercylan98 <kercylan@gmail.com>
Date: Fri, 15 Sep 2023 14:11:30 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20random=20=E5=8C=85=E6=96=B0=E5=A2=9E=20?=
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---
 utils/random/probability.go       | 59 +++++++++++++++++++++++++++++++
 utils/random/probabillity_test.go | 17 +++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 utils/random/probabillity_test.go

diff --git a/utils/random/probability.go b/utils/random/probability.go
index a9763ab..6740ecf 100644
--- a/utils/random/probability.go
+++ b/utils/random/probability.go
@@ -1,5 +1,64 @@
 package random
 
+import (
+	"math/rand"
+	"time"
+)
+
+// ProbabilitySlice 按概率随机从切片中产生一个数据并返回命中的对象及是否未命中
+//   - 当总概率小于 1 将会发生未命中的情况
+func ProbabilitySlice[T any](getProbabilityHandle func(data T) float64, data ...T) (hit T, miss bool) {
+	rd := rand.New(rand.NewSource(time.Now().UnixNano()))
+
+	var total float64
+	for _, d := range data {
+		total += getProbabilityHandle(d)
+	}
+
+	scaleFactor := 1.0
+	var indexLimit = len(data)
+	var limitP = 0.0
+	if total > 1.0 {
+		scaleFactor = 1.0 / total
+	} else if total < 1.0 {
+		indexLimit++
+		limitP = 1.0 - total
+	}
+
+	var overlayProbability []float64
+	cumulativeProbability := 0.0
+	for i := 0; i < indexLimit; i++ {
+		if i < len(data) {
+			cumulativeProbability += getProbabilityHandle(data[i]) * scaleFactor
+			overlayProbability = append(overlayProbability, cumulativeProbability)
+		} else {
+			cumulativeProbability += limitP * scaleFactor
+			overlayProbability = append(overlayProbability, cumulativeProbability)
+		}
+
+	}
+
+	if total < 1.0 {
+		overlayProbability[len(overlayProbability)-1] = 1.0
+	}
+
+	var r = rd.Float64()
+	var i, count = 0, len(overlayProbability)
+	for i < count {
+		h := int(uint(i+count) >> 1)
+		if overlayProbability[h] <= r {
+			i = h + 1
+		} else {
+			count = h
+		}
+	}
+	if i >= len(data) {
+		return hit, true
+	}
+	hit = data[i]
+	return hit, false
+}
+
 // Probability 输入一个概率，返回是否命中
 //   - 当 full 不为空时，将以 full 为基数，p 为分子，计算命中概率
 func Probability(p int, full ...int) bool {
diff --git a/utils/random/probabillity_test.go b/utils/random/probabillity_test.go
new file mode 100644
index 0000000..243c100
--- /dev/null
+++ b/utils/random/probabillity_test.go
@@ -0,0 +1,17 @@
+package random_test
+
+import (
+	"github.com/kercylan98/minotaur/utils/random"
+	"testing"
+)
+
+func TestProbabilitySlice(t *testing.T) {
+	var awards = []int{1, 2, 3, 4, 5, 6, 7}
+	var probability = []float64{0.1, 2, 0.1, 0.1, 0.1, 0.1, 0.1}
+
+	for i := 0; i < 50; i++ {
+		t.Log(random.ProbabilitySlice(func(data int) float64 {
+			return probability[data-1]
+		}, awards...))
+	}
+}