Moving mlog to corelibs (#16915)

* Moving mlog to corelibs

* Regenerating app layers

* Fix golangci-lint problem

* Fixing golangci-lint errors

* Renaming from corelibs to shared

* Renaming from corelibs to shared

* Fixing import

* Fixing merge problems

* Fixing build

shared/mlog/human/parser.go

@@ -0,0 +1,181 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v5/shared/mlog"
+)
+
+func ParseLogMessage(msg string) LogEntry {
+	result, err := parseLogMessage(msg)
+	if err != nil {
+		// If failed to parse, just output a LogEntry where all fields are blank, but Message is the original string
+		var result2 LogEntry
+		result2.Message = msg
+		return result2
+	}
+	return result
+}
+
+func parseLogMessage(msg string) (result LogEntry, err error) {
+
+	// Note: This implementation uses a custom json decoding loop.
+	// The primary advantage of this versus decoding directly into a map is to
+	// preserve the order of the fields. This can be simplified if we end up
+	// having the formatter sort fields alphabetically (logrus does by default)
+
+	dec := json.NewDecoder(strings.NewReader(msg))
+
+	// look for an initial "{"
+	token, err := dec.Token()
+	if err != nil {
+		return result, err
+	}
+	d, ok := token.(json.Delim)
+	if !ok || d != '{' {
+		return result, fmt.Errorf("input is not a JSON object, found: %v", token)
+	}
+
+	// read all key-value pairs
+	for dec.More() {
+		key, err2 := dec.Token()
+		if err2 != nil {
+			return result, err2
+		}
+		skey, ok2 := key.(string)
+		if !ok2 {
+			return result, errors.New("key is not a value string")
+		}
+		if !dec.More() {
+			return result, errors.New("missing value pair")
+		}
+
+		switch skey {
+		case "ts":
+			var ts json.Number
+			if err2 := dec.Decode(&ts); err2 != nil {
+				return result, err2
+			}
+			timeVal, err2 := numberToTime(ts)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Time = timeVal
+
+		case "level":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Level = s
+
+		case "msg":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Message = s
+
+		case "caller":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Caller = s
+
+		default:
+			var p interface{}
+			if err2 := dec.Decode(&p); err2 != nil {
+				return result, err2
+			}
+			var f mlog.Field
+			f.Key = skey
+			f.Interface = p
+			result.Fields = append(result.Fields, f)
+		}
+	}
+
+	// read the "}"
+	token, err = dec.Token()
+	if err != nil {
+		return result, err
+	}
+	d, ok = token.(json.Delim)
+	if !ok || d != '}' {
+		return result, fmt.Errorf("failed to read '}', read: %v", token)
+	}
+
+	// make sure nothing else trailing
+	if token, err := dec.Token(); err != io.EOF {
+		return result, err
+	} else if token != nil {
+		return result, errors.New("found trailing data")
+	}
+
+	return result, nil
+}
+
+// Translate a number into a time
+func numberToTime(v json.Number) (time.Time, error) {
+	// Using floating point math to extract the nanoseconds leads to a time that doesn't exactly match the input
+	// Instead, parse out the components from the string representation
+
+	var t time.Time
+
+	// First make sure it is a number...
+	flt, err := v.Float64()
+	if err != nil {
+		return t, err
+	}
+
+	s := v.String()
+
+	if strings.ContainsAny(s, "eE") {
+		// input is in scientific notation. Convert to standard decimal notation
+		s = strconv.FormatFloat(flt, 'f', -1, 64)
+	}
+
+	// extract the seconds and nanoseconds separately
+	var nanos, sec int64
+
+	parts := strings.SplitN(s, ".", 2)
+	sec, err = strconv.ParseInt(parts[0], 10, 64)
+	if err != nil {
+		return t, err
+	}
+
+	if len(parts) == 2 {
+		nanosText := parts[1] + "000000000"
+		nanosText = nanosText[:9]
+		nanos, err = strconv.ParseInt(nanosText, 10, 64)
+		if err != nil {
+			return t, err
+		}
+	}
+
+	t = time.Unix(sec, nanos)
+	return t, nil
+}
+
+// Decodes a value from JSON, coercing it to a string value as necessary
+func decodeAsString(dec *json.Decoder) (s string, err error) {
+	var v interface{}
+	if err = dec.Decode(&v); err != nil {
+		return s, err
+	}
+	var ok bool
+	if s, ok = v.(string); ok {
+		return s, err
+	}
+	s = fmt.Sprint(v)
+	return s, err
+}