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backend/internal/credentialweight/weight.go

@@ -0,0 +1,100 @@
+// Package credentialweight defines shared credential weight validation and parsing.
+package credentialweight
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+)
+
+const (
+	// Default is used when a credential does not define a weight.
+	Default int64 = 1
+	// Max bounds scheduler arithmetic while allowing practical proportional routing.
+	Max int64 = 1_000_000
+)
+
+// Normalize validates and normalizes an explicit weight. Non-positive values are
+// valid and normalize to zero, which excludes the credential from weighted routing.
+func Normalize(weight int64) (int64, error) {
+	if weight <= 0 {
+		return 0, nil
+	}
+	if weight > Max {
+		return 0, fmt.Errorf("weight must not exceed %d", Max)
+	}
+	return weight, nil
+}
+
+// ParseString parses a scheduler attribute. An empty value uses the default weight.
+func ParseString(raw string) (int64, error) {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return Default, nil
+	}
+	weight, errParse := strconv.ParseInt(raw, 10, 64)
+	if errParse != nil {
+		return 0, fmt.Errorf("weight must be an integer: %w", errParse)
+	}
+	return Normalize(weight)
+}
+
+// ParseValue parses a JSON-compatible auth-file metadata value.
+func ParseValue(value any) (int64, error) {
+	switch typed := value.(type) {
+	case int:
+		return Normalize(int64(typed))
+	case int8:
+		return Normalize(int64(typed))
+	case int16:
+		return Normalize(int64(typed))
+	case int32:
+		return Normalize(int64(typed))
+	case int64:
+		return Normalize(typed)
+	case uint:
+		if uint64(typed) > uint64(Max) {
+			return 0, fmt.Errorf("weight must not exceed %d", Max)
+		}
+		return int64(typed), nil
+	case uint8:
+		return int64(typed), nil
+	case uint16:
+		return int64(typed), nil
+	case uint32:
+		if uint64(typed) > uint64(Max) {
+			return 0, fmt.Errorf("weight must not exceed %d", Max)
+		}
+		return int64(typed), nil
+	case uint64:
+		if typed > uint64(Max) {
+			return 0, fmt.Errorf("weight must not exceed %d", Max)
+		}
+		return int64(typed), nil
+	case float64:
+		if math.IsNaN(typed) || math.IsInf(typed, 0) || math.Trunc(typed) != typed {
+			return 0, fmt.Errorf("weight must be an integer")
+		}
+		if typed <= 0 {
+			return 0, nil
+		}
+		if typed > float64(Max) {
+			return 0, fmt.Errorf("weight must not exceed %d", Max)
+		}
+		return int64(typed), nil
+	case float32:
+		return ParseValue(float64(typed))
+	case json.Number:
+		weight, errParse := typed.Int64()
+		if errParse != nil {
+			return 0, fmt.Errorf("weight must be an integer: %w", errParse)
+		}
+		return Normalize(weight)
+	case string:
+		return ParseString(typed)
+	default:
+		return 0, fmt.Errorf("weight must be an integer")
+	}
+}