my-log/models/meta.go

package models

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"
)

type Meta struct {
	Key   string
	Value any
}

func (m Meta) MarshalText() ([]byte, error) {
	if regexp.MustCompile(`\s`).MatchString(m.Key) {
		return []byte{}, fmt.Errorf("whitespace is not allowed in key: %s", m.Key)
	}
	buff := &bytes.Buffer{}
	buff.WriteRune('@')
	buff.WriteString(m.Key)
	buff.WriteRune(' ')
	switch v := m.Value.(type) {
	default:
		return nil, fmt.Errorf("Unknown type %T", v)
	case nil:
		return []byte{}, nil
	case string:
		buff.WriteString(v)
	case int:
		buff.WriteString(strconv.Itoa(v))
	case int64:
		buff.WriteString(strconv.FormatInt(v, 10))
	case float64:
		buff.WriteString(strconv.FormatFloat(v, 'f', -1, 64))
	case json.Number:
		buff.WriteString(v.String())
	case json.RawMessage:
		buff.Write(v)
	case []byte:
		buff.Write(v)
	case byte:
		buff.WriteByte(v)
	case rune:
		buff.WriteString(string(v))
	case bool:
		buff.WriteString(strconv.FormatBool(v))
	case time.Time:
		buff.WriteString(v.Format(time.RFC3339))
	}

	return buff.Bytes(), nil
}

func (m *Meta) UnmarshalText(in []byte) error {
	if len(in) == 0 {
		return newParsingError(errors.New("Unable to Unmarshal empty string"))
	}
	re := regexp.MustCompile("(?s)^@([^ ]+) (.*)( @end)?$")
	match := re.FindSubmatch(in)
	if len(match) == 0 {
		return newParsingError(fmt.Errorf("Failed to match %s", in))
	}
	m.Key = string(match[1])
	return m.processMeta(match[2])
}

func (m *Meta) processMeta(in []byte) error {
	if len(in) == 0 {
		return newParsingError(errors.New("No value found"))
	}
	s := strings.TrimSpace(string(in))
	if len(s) == 0 {
		return newParsingError(errors.New("No value found"))
	}
	yesno := regexp.MustCompile("^(y|Y|yes|Yes|YES|n|N|no|No|NO|true|True|TRUE|false|False|FALSE|on|On|ON|off|Off|OFF)$")
	yes := regexp.MustCompile("^(y|Y|yes|Yes|YES|true|True|TRUE|on|On|ON)$")
	null := regexp.MustCompile("^(~|null|Null|NULL|none|None|NONE|nil|Nil|NIL)$")
	var j json.RawMessage
	if null.MatchString(s) {
		m.Value = nil
	} else if yesno.MatchString(s) {
		if yes.MatchString(s) {
			m.Value = true
		} else {
			m.Value = false
		}
	} else if i, err := strconv.Atoi(s); err == nil {
		m.Value = i
	} else if f, err := strconv.ParseFloat(s, 64); err == nil {
		m.Value = f
	} else if t, err := time.Parse(time.RFC3339, s); err == nil {
		m.Value = t
	} else if err := json.Unmarshal(in, &j); err == nil {
		m.Value = j
	} else {
		m.Value = s
	}

	return nil
}