Improve performance of status map parser

asstatusparse.go

@@ -1,63 +1,72 @@
 package checkers
 
-import (
-	"fmt"
-	"strings"
+import "strings"
 
-	"golang.org/x/exp/slices"
-)
+type invalidStatusMapError string
 
-var keywords = []string{"OK", "WARNING", "CRITICAL", "UNKNOWN"}
+func (err invalidStatusMapError) Error() string {
+	return "invalid status map: " + string(err)
+}
+
+type duplicateStatusMapError Status
+
+func (err duplicateStatusMapError) Error() string {
+	return "duplicate status in map: " + Status(err).String()
+}
 
-func strToStatus(s string) Status {
-	switch s {
-	case "OK":
-		return OK
-	case "WARNING":
-		return WARNING
-	case "CRITICAL":
-		return CRITICAL
-	case "UNKNOWN":
-		return UNKNOWN
+func parseStatus(src string) (Status, string, bool) {
+	switch {
+	case strings.HasPrefix(src, "OK"):
+		return OK, src[len("OK"):], true
+	case strings.HasPrefix(src, "WARNING"):
+		return WARNING, src[len("WARNING"):], true
+	case strings.HasPrefix(src, "CRITICAL"):
+		return CRITICAL, src[len("CRITICAL"):], true
+	case strings.HasPrefix(src, "UNKNOWN"):
+		return UNKNOWN, src[len("UNKNOWN"):], true
+	default:
+		return OK, src, false
 	}
-	panic("invalid inputs.")
 }
 
-// Parse parses <status>=<status> notation string. <status> is one of:
+// Parse parses a string of the form <status>=<status>. <status> is one of:
+//
 //   - ok
 //   - warning
 //   - critical
 //   - unknown
 //
-// It can have multiple key-value pairs by comma.
-func Parse(arg string) (map[Status]Status, error) {
-	if arg == "" {
-		return nil, nil
-	}
-
-	maps := make(map[Status]Status, 0)
-	args := strings.Split(arg, ",")
-
-	for _, s := range args {
-		if s == "" {
-			continue
+// You can specify multiple key-value pairs separated by commas.
+func Parse(src string) (map[Status]Status, error) {
+	orig := src
+	stm := map[Status]Status{}
+	for src = strings.ToUpper(src); src != ""; {
+		var (
+			from, to Status
+			ok       bool
+		)
+		from, src, ok = parseStatus(src)
+		if !ok {
+			return nil, invalidStatusMapError(orig)
 		}
-		rawFrom, rawTo, found := strings.Cut(s, "=")
-		if !found {
-			return nil, fmt.Errorf("arguments is invalid : %v", s)
+		src, ok = strings.CutPrefix(src, "=")
+		if !ok {
+			return nil, invalidStatusMapError(orig)
 		}
-		from := strings.ToUpper(rawFrom)
-		to := strings.ToUpper(rawTo)
-		if !slices.Contains(keywords, from) {
-			return nil, fmt.Errorf("from argument is invalid : %s", rawFrom)
+		to, src, ok = parseStatus(src)
+		if !ok {
+			return nil, invalidStatusMapError(orig)
 		}
-		if !slices.Contains(keywords, to) {
-			return nil, fmt.Errorf("to argument is invalid : %s", rawTo)
+		if _, ok = stm[from]; ok {
+			return nil, duplicateStatusMapError(from)
 		}
-		if _, ok := maps[strToStatus(from)]; ok {
-			return nil, fmt.Errorf("arguments is duplicate : %v", from)
+		stm[from] = to
+		if src != "" {
+			src, ok = strings.CutPrefix(src, ",")
+			if !ok || src == "" {
+				return nil, invalidStatusMapError(orig)
+			}
 		}
-		maps[strToStatus(from)] = strToStatus(to)
 	}
-	return maps, nil
+	return stm, nil
 }

asstatusparse_test.go

@@ -20,10 +20,17 @@ func TestParse(t *testing.T) {
 			},
 		},
 		{
-			name:   "multi",
-			source: "unknown=critical,warning=critical",
+			name:   "uppercase",
+			source: "UNKNOWN=CRITICAL",
 			expected: map[Status]Status{
 				UNKNOWN: CRITICAL,
+			},
+		},
+		{
+			name:   "multi",
+			source: "unknown=ok,warning=critical",
+			expected: map[Status]Status{
+				UNKNOWN: OK,
 				WARNING: CRITICAL,
 			},
 		},
@@ -32,14 +39,24 @@ func TestParse(t *testing.T) {
 			source:  "invalid=critical",
 			wantErr: true,
 		},
+		{
+			name:    "= error",
+			source:  "unknown critical",
+			wantErr: true,
+		},
 		{
 			name:    "to error",
 			source:  "critical=invalid",
 			wantErr: true,
 		},
 		{
 			name:    "argument error",
-			source:  "invalid=critical=invalid",
+			source:  "unknown=critical=invalid",
+			wantErr: true,
+		},
+		{
+			name:    "trailing comma error",
+			source:  "unknown=ok,",
 			wantErr: true,
 		},
 		{

checkers.go

@@ -19,11 +19,11 @@ const (
 
 func (st Status) String() string {
 	switch st {
-	case 0:
+	case OK:
 		return "OK"
-	case 1:
+	case WARNING:
 		return "WARNING"
-	case 2:
+	case CRITICAL:
 		return "CRITICAL"
 	default:
 		return "UNKNOWN"

go.mod

@@ -1,5 +1,3 @@
 module github.com/mackerelio/checkers
 
-go 1.18
-
-require golang.org/x/exp v0.0.0-20230905200255-921286631fa9
+go 1.20