feat: update ConversionOutcome to output as string in JSON

vulnfeeds/models/metrics.go

@@ -1,13 +1,15 @@
 package models
 
 import (
+	"encoding/json"
 	"fmt"
 	"log/slog"
 
 	"github.com/google/osv/vulnfeeds/utility/logger"
 	"github.com/ossf/osv-schema/bindings/go/osvschema"
 )
 
+//nolint:recvcheck
 type ConversionOutcome int
 
 const (
@@ -36,8 +38,36 @@ var RefTagDenyList = []string{
 	"Broken Link", // Actively ignore these.
 }
 
+var conversionOutcomeStrings = [...]string{
+	"ConversionUnknown", "Successful", "Rejected", "NoSoftware", "NoRepos", "NoCommitRanges", "NoRanges", "FixUnresolvable", "Error",
+}
+
 func (c ConversionOutcome) String() string {
-	return [...]string{"ConversionUnknown", "Successful", "Rejected", "NoSoftware", "NoRepos", "NoCommitRanges", "NoRanges", "FixUnresolvable", "Error"}[c]
+	if int(c) >= 0 && int(c) < len(conversionOutcomeStrings) {
+		return conversionOutcomeStrings[c]
+	}
+
+	return conversionOutcomeStrings[ConversionUnknown]
+}
+
+func (c ConversionOutcome) MarshalJSON() ([]byte, error) {
+	return json.Marshal(c.String())
+}
+
+func (c *ConversionOutcome) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	for i, val := range conversionOutcomeStrings {
+		if val == s {
+			*c = ConversionOutcome(i)
+
+			return nil
+		}
+	}
+
+	return fmt.Errorf("invalid ConversionOutcome %q", s)
 }
 
 // ConversionMetrics holds the collected data about the conversion process for a single CVE.