feat(logparser): add generic json parser

Updates: #243

internal/logparser/_golden/genericjson_01.json

@@ -0,0 +1,21 @@
+{
+  "severity_number_str": "Info",
+  "severity_text": "info",
+  "body": "Events",
+  "timestamp": "2023-12-04T09:11:59.1613184Z",
+  "logger": "poll",
+  "caller": "gh-archived/main.go:197",
+  "duration": 0.437301455,
+  "integers": [
+    1,
+    2,
+    3
+  ],
+  "new_count": 100,
+  "remaining": 1040,
+  "used": 3960,
+  "reset": 660.838704106,
+  "reset_human": "in 12 minutes",
+  "sleep": 0.198120375,
+  "target_rate": 0.63542183
+}

internal/logparser/_testdata/genericjson/zap.jsonl

@@ -0,0 +1 @@
+{"level":"info","ts":1701681119.1613183,"logger":"poll","caller":"gh-archived/main.go:197","msg":"Events","duration":0.437301455,"integers":[1, 2, 3],"new_count":100,"remaining":1040,"used":3960,"reset":660.838704106,"reset_human":"in 12 minutes","sleep":0.198120375,"target_rate":0.63542183}

internal/logparser/deduct.go

@@ -0,0 +1,26 @@
+package logparser
+
+import "time"
+
+// ISO8601Millis time format with millisecond precision.
+const ISO8601Millis = "2006-01-02T15:04:05.000Z0700"
+
+// we are not expecting logs from past.
+var deductStart = time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
+
+// deductNanos returns unix nano from arbitrary time integer, deducting resolution by range.
+func deductNanos(n int64) (int64, bool) {
+	if n > deductStart.UnixNano() {
+		return n, true
+	}
+	if n > deductStart.UnixMicro() {
+		return n * 1e3, true
+	}
+	if n > deductStart.UnixMilli() {
+		return n * 1e6, true
+	}
+	if n > deductStart.Unix() {
+		return n * 1e9, true
+	}
+	return 0, false
+}

internal/logparser/deduct_test.go

@@ -0,0 +1,33 @@
+package logparser
+
+import (
+	"math"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestDeductNanos(t *testing.T) {
+	var (
+		start = time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
+		end   = time.Date(2200, 1, 1, 0, 0, 0, 0, time.UTC)
+	)
+	truncate := func(nanos int64, zeroes int) int64 {
+		d := int64(math.Pow10(zeroes))
+		return nanos - nanos%d
+	}
+	assert := func(a, b int64, msgAndArgs ...interface{}) {
+		t.Helper()
+		v, ok := deductNanos(a)
+		require.True(t, ok, msgAndArgs...)
+		require.Equal(t, b, v, msgAndArgs...)
+	}
+	for v := start; v.Before(end); v = v.Add(time.Second*44 + time.Nanosecond*1337123 + time.Hour*6) {
+		expected := v.UnixNano()
+		assert(v.Unix(), truncate(expected, 9), "v=%v", v)
+		assert(v.UnixMilli(), truncate(expected, 6), "v=%v", v)
+		assert(v.UnixMicro(), truncate(expected, 3), "v=%v", v)
+		assert(v.UnixNano(), expected, "v=%v", v)
+	}
+}

internal/logparser/gold_test.go

@@ -0,0 +1,15 @@
+package logparser
+
+import (
+	"os"
+	"testing"
+
+	"github.com/go-faster/sdk/gold"
+)
+
+func TestMain(m *testing.M) {
+	// Explicitly registering flags for golden files.
+	gold.Init()
+
+	os.Exit(m.Run())
+}