✨ Add Meta with TextMarshaler

models/meta.go

@@ -1 +1,53 @@
 package models
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"strconv"
+	"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 now 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 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
+}

models/meta_test.go

@@ -0,0 +1,54 @@
+package models
+
+import (
+	"encoding"
+	"encoding/json"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Type assertions
+var _ encoding.TextMarshaler = Meta{}
+
+func TestMeta(t *testing.T) {
+	when := time.Now()
+	tests := []struct {
+		name  string
+		key   string
+		value any
+		out   string
+		err   error
+	}{
+		{"int", "num", 42, "@num 42", nil},
+		{"float", "num", 42.13, "@num 42.13", nil},
+		{"string", "word", "hello", "@word hello", nil},
+		{"json number", "num", json.Number("42.13"), "@num 42.13", nil},
+		{"true", "b", true, "@b true", nil},
+		{"false", "b", false, "@b false", nil},
+		{"nil", "n", nil, "", nil},
+		{"time", "when", when, "@when " + when.Format(time.RFC3339), nil},
+		{"rune", "char", '@', "@char @", nil},
+		{"bytes", "byteme", []byte("yo"), "@byteme yo", nil},
+		{"byte", "byteme", byte(67), "@byteme C", nil},
+		{"json-obj", "obj", json.RawMessage(`{"foo":"bar","baz":"quux"}`), `@obj {"foo":"bar","baz":"quux"}`, nil},
+		{"json-arr", "arr", json.RawMessage(`["foo",42,"bar", null,"quux", true]`), `@arr ["foo",42,"bar", null,"quux", true]`, nil},
+		{"chan", "nope", make(chan bool), "", errors.New("Unknown type chan bool")},
+		{"whitespace", "no space", "hi", "", errors.New("whitespace is now allowed in key: no space")},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, getMetaTestRunner(tt.key, tt.value, tt.out, tt.err))
+	}
+}
+
+func getMetaTestRunner(key string, value any, out string, err error) func(*testing.T) {
+	return func(t *testing.T) {
+		st := Meta{key, value}
+		o, e := st.MarshalText()
+		assert.Equal(t, out, string(o))
+		assert.Equal(t, err, e)
+	}
+}