first commit

internal/generate/id.go

@@ -0,0 +1,86 @@
+package generate
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	mathRand "math/rand"
+	"strconv"
+	"strings"
+)
+
+// ID generates an ID using crypto-random, falling back to math random when that fails
+// to avoid disrupting operation because of a faulty RNG.
+func ID(prefix string, length int) string {
+	var data [32]byte
+
+	result := strings.Builder{}
+	result.Grow(length + 32)
+	result.WriteString(prefix)
+
+	pos := 0
+	for result.Len() < length {
+		if pos == 0 {
+			randRead(data[:])
+		}
+
+		result.WriteString(strconv.FormatUint(binary.BigEndian.Uint64(data[pos:pos+8]), 36))
+
+		pos = (pos + 8) % 32
+	}
+
+	return result.String()[:length]
+}
+
+func randRead(data []byte) {
+	n, err := rand.Read(data)
+	if err != nil {
+		mathRand.Read(data[n:])
+	}
+}
+
+// InternalErrorID generates a long string
+func InternalErrorID() string {
+	return ID("ISE", 32)
+}
+
+// TagID generates a location ID. len=8
+func TagID(longName string) string {
+	return friendlyID('T', longName, 8)
+}
+
+// CharacterID generates a character ID. len=8
+func CharacterID(longName string) string {
+	return friendlyID('C', longName, 8)
+}
+
+func friendlyID(prefix byte, name string, length int) string {
+	b := strings.Builder{}
+	b.Grow(4)
+	b.WriteByte(prefix)
+	for _, ch := range strings.ToLower(name) {
+		if ch >= 'a' && ch <= 'z' {
+			b.WriteRune(ch)
+
+			if b.Len() > 3 {
+				break
+			}
+		}
+	}
+
+	return ID(b.String(), length)
+}
+
+// StoryID generates a story ID: len=8
+func StoryID() string {
+	return ID("S", 12)
+}
+
+// PostID generates a post ID. len=12
+func PostID() string {
+	return ID("P", 16)
+}
+
+// AnnotationID generates an annotation.sql ID. len=12
+func AnnotationID() string {
+	return ID("A", 16)
+}