feat: support timestamp reformatting (#129)

Author: hedhyw

assets/example.log

@@ -53,4 +53,6 @@ plain text log
 {"time":883612800.45,"level":"WARN","message": "If a man knows not to which port he sails, no wind is favorable","author": "Seneca"}
 {"time":"915148800000.45","level":"VERBOSE","message": "Begin at once to live, and count each separate day as a separate life","author": "Seneca"}
 {"time":946684800.45,"level":"VERBOSE","message": "Begin at once to live, and count each separate day as a separate life","author": "Seneca"}
-{"@timestamp":"2025-03-06T11:55:53.723682+01:00","@version":1,"host":"bad21ee895cd","message":"Message ..","level":"INFO"}
+{"@timestamp":"2025-03-06T11:55:53.723682+01:00","@version":1,"host":"bad21ee895cd","message":"Symphony format","level":"INFO"}
+{"time": "02 Jan 06 15:04 MST","level":"VERBOSE","message": "RFC822 time","author": "Seneca"}
+{"time": "Mon, 02 Jan 2006 15:04:05 MST","level":"VERBOSE","message": "RFC1123 time","author": "Seneca"}

example.jlv.jsonc

@@ -65,6 +65,31 @@
             "width": 0
         }
     ],
+    // Time layouts to reformat.
+    //
+    // If the time field has been parsed to any of the specified layouts,
+    // it will be formatted according to "time_format" configuration.
+    //
+    // See: https://pkg.go.dev/time#pkg-constants.
+    "time_layouts": [
+	    "01/02 03:04:05PM '06 -0700",
+	    "Mon Jan _2 15:04:05 2006",
+	    "Mon Jan _2 15:04:05 MST 2006",
+	    "Mon Jan 02 15:04:05 -0700 2006",
+	    "02 Jan 06 15:04 MST",
+	    "02 Jan 06 15:04 -0700",
+	    "Monday, 02-Jan-06 15:04:05 MST",
+	    "Mon, 02 Jan 2006 15:04:05 MST",
+	    "Mon, 02 Jan 2006 15:04:05 -0700",
+	    "2006-01-02T15:04:05Z07:00",
+	    "2006-01-02T15:04:05.999999999Z07:00",
+	    "Jan _2 15:04:05",
+	    "Jan _2 15:04:05.000",
+	    "Jan _2 15:04:05.000000",
+	    "Jan _2 15:04:05.000000000",
+	    "2006-01-02 15:04:05",
+	    "2006-01-02"
+	],
     // Mapping of log level.
     // Possible values: none, trace, debug, info, warn, error, panic, fatal.
     "customLevelMapping": {

internal/pkg/config/config.go

@@ -25,6 +25,8 @@ type Config struct {
 	Path string `json:"-"`
 
 	Fields []Field `json:"fields" validate:"min=1"`
+	// TimeLayouts to reformat.
+	TimeLayouts []string `json:"time_layouts"`
 
 	CustomLevelMapping map[string]string `json:"customLevelMapping"`
 
@@ -65,6 +67,25 @@ func GetDefaultConfig() *Config {
 		Path:               "default",
 		CustomLevelMapping: GetDefaultCustomLevelMapping(),
 		MaxFileSizeBytes:   2 * units.GB,
+		TimeLayouts: []string{
+			time.Layout,
+			time.ANSIC,
+			time.UnixDate,
+			time.RubyDate,
+			time.RFC822,
+			time.RFC822Z,
+			time.RFC850,
+			time.RFC1123,
+			time.RFC1123Z,
+			time.RFC3339,
+			time.RFC3339Nano,
+			time.Stamp,
+			time.StampMilli,
+			time.StampMicro,
+			time.StampNano,
+			time.DateTime,
+			time.DateOnly,
+		},
 		Fields: []Field{{
 			Title:      "Time",
 			Kind:       FieldKindNumericTime,

internal/pkg/config/config_test.go

@@ -138,6 +138,25 @@ func ExampleGetDefaultConfig() {
 	//       "width": 0
 	//     }
 	//   ],
+	//   "time_layouts": [
+	//     "01/02 03:04:05PM '06 -0700",
+	//     "Mon Jan _2 15:04:05 2006",
+	//     "Mon Jan _2 15:04:05 MST 2006",
+	//     "Mon Jan 02 15:04:05 -0700 2006",
+	//     "02 Jan 06 15:04 MST",
+	//     "02 Jan 06 15:04 -0700",
+	//     "Monday, 02-Jan-06 15:04:05 MST",
+	//     "Mon, 02 Jan 2006 15:04:05 MST",
+	//     "Mon, 02 Jan 2006 15:04:05 -0700",
+	//     "2006-01-02T15:04:05Z07:00",
+	//     "2006-01-02T15:04:05.999999999Z07:00",
+	//     "Jan _2 15:04:05",
+	//     "Jan _2 15:04:05.000",
+	//     "Jan _2 15:04:05.000000",
+	//     "Jan _2 15:04:05.000000000",
+	//     "2006-01-02 15:04:05",
+	//     "2006-01-02"
+	//   ],
 	//   "customLevelMapping": {
 	//     "10": "trace",
 	//     "20": "debug",

internal/pkg/source/entry.go

@@ -173,7 +173,7 @@ func formatField(
 	case config.FieldKindLevel:
 		return string(ParseLevel(formatMessage(value), cfg.CustomLevelMapping))
 	case config.FieldKindTime:
-		return formatMessage(value)
+		return formatMessage(reformatTime(value, cfg.TimeLayouts, timeFormat))
 	case config.FieldKindSecondTime:
 		return formatMessage(formatTimeValue(value, unitSeconds, timeFormat))
 	case config.FieldKindMilliTime:
@@ -187,6 +187,17 @@ func formatField(
 	}
 }
 
+func reformatTime(value string, layoutsToReformat []string, timeFormat string) string {
+	for _, laoyout := range layoutsToReformat {
+		parsed, err := time.Parse(laoyout, value)
+		if err == nil {
+			return parsed.Format(timeFormat)
+		}
+	}
+
+	return value
+}
+
 // parseLogEntry parses a single log entry from the json line.
 func parseLogEntry(
 	line json.RawMessage,

internal/pkg/source/entry_test.go

@@ -469,7 +469,11 @@ func TestNumericKindTimeFormatting(t *testing.T) {
 	numericKindCases := [...]timeFormattingTestCase{{
 		TestName:       "Date passthru",
 		JSON:           `{"timestamp":"2023-10-08 20:00:00"}`,
-		ExpectedOutput: "2023-10-08 20:00:00",
+		ExpectedOutput: "2023-10-08T20:00:00Z",
+	}, {
+		TestName:       "RFC1123 passthru",
+		JSON:           `{"@timestamp":"Mon, 02 Jan 2006 15:04:05 MST"}`,
+		ExpectedOutput: "2006-01-02T15:04:05Z",
 	}, {
 		TestName:       "Non-date string",
 		JSON:           `{"timestamp":"-"}`,