split src/devices/input into src/devices/input/{raw,wrap}

src/device/input/raw/random.go

@@ -0,0 +1,92 @@
+package raw
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"math/rand"
+	"os"
+	"sort"
+	"time"
+
+	"github.com/go-yaml/yaml"
+)
+
+type Random struct {
+	generator func() byte
+	down      []byte
+}
+
+func NewRandom(generator func() byte) *Random {
+	rand.Seed(time.Now().UnixNano())
+	return &Random{generator: generator}
+}
+
+func (r *Random) Close() {
+}
+
+func (r *Random) Read() []byte {
+	return []byte{r.generator()}
+}
+
+func randomCharFromRange(start, stop byte) func() byte {
+	return func() byte {
+		return start + byte(rand.Int()%int(1+stop-start))
+	}
+}
+
+func randomCharFromWeightFile(p string) func() byte {
+	b, err := os.ReadFile(p)
+	if err != nil {
+		panic(err)
+	}
+	return randomCharFromWeightReader(bytes.NewReader(b))
+}
+
+func randomCharFromWeightReader(r io.Reader) func() byte {
+	var m map[string]int
+	if err := yaml.NewDecoder(r).Decode(&m); err != nil {
+		panic(err)
+	}
+	byted := map[byte]int{}
+	for k, v := range m {
+		if len(k) != 1 {
+			panic(fmt.Sprintf("keys must be 1 character but got %q", k))
+		}
+		byted[k[0]] = v
+	}
+	return randomCharFromWeights(byted)
+}
+
+func randomCharFromWeights(m map[byte]int) func() byte {
+	type pair struct {
+		b byte
+		i int
+	}
+	result := make([]pair, 0, len(m))
+	sum := 0
+	for k, v := range m {
+		result = append(result, pair{b: k, i: v})
+		if v < 0 {
+			panic("each weight must each be natural")
+		}
+		sum += v
+	}
+	sort.Slice(result, func(i, j int) bool {
+		return result[i].i < result[j].i
+	})
+	if sum <= 0 {
+		panic("weights must total nonzero")
+	}
+	return func() byte {
+		r := rand.Int()
+		n := r % (sum + 1)
+		for _, v := range result {
+			n -= v.i
+			if n <= 0 {
+				return v.b
+			}
+		}
+		panic("how")
+	}
+}