move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/tdp/tdp.go

@@ -0,0 +1,123 @@
+// Package tdp is td pretty-printing and formatting facilities for types from
+// MTProto.
+package tdp
+
+import (
+	"encoding/base64"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// options for formatting.
+type options struct {
+	writeTypeID bool
+}
+
+// Option of formatting.
+type Option func(o *options)
+
+// WithTypeID adds type id tp type name.
+func WithTypeID(o *options) {
+	o.writeTypeID = true
+}
+
+const (
+	defaultIdent = "  "
+	noIdent      = ""
+)
+
+func formatValue(b *strings.Builder, prefix, fieldName string, opt options, v reflect.Value) {
+	switch v.Kind() {
+	case reflect.Struct, reflect.Ptr, reflect.Interface:
+		i, ok := v.Interface().(Object)
+		if ok {
+			format(b, prefix+defaultIdent, opt, i)
+		} else if v.CanAddr() {
+			formatValue(b, prefix, fieldName, opt, v.Addr())
+		}
+	case reflect.Slice:
+		if buf, ok := v.Interface().([]byte); ok {
+			b.WriteString(base64.RawURLEncoding.EncodeToString(buf))
+			return
+		}
+
+		b.WriteRune('\n')
+		for i := 0; i < v.Len(); i++ {
+			vi := v.Index(i)
+			b.WriteString(prefix)
+			b.WriteString(defaultIdent)
+			b.WriteString("- ")
+			formatValue(b, prefix+defaultIdent, fieldName, opt, vi)
+			b.WriteRune('\n')
+		}
+	case reflect.Int:
+		// Special case for date.
+		var (
+			now = time.Now()
+			max = now.AddDate(0, 0, 7).Unix()
+			min = now.AddDate(-2, 0, 0).Unix()
+		)
+		i := v.Int()
+		if i > min && i < max && strings.Contains(fieldName, "date") {
+			b.WriteString(time.Unix(i, 0).UTC().Format(time.RFC3339))
+		} else {
+			b.WriteString(strconv.FormatInt(i, 10))
+		}
+	default:
+		b.WriteString(fmt.Sprint(v.Interface()))
+	}
+}
+
+func format(b *strings.Builder, prefix string, opt options, obj Object) {
+	if obj == nil {
+		// No type information is available. it is like Format(nil).
+		b.WriteString("<nil>")
+		return
+	}
+
+	info := obj.TypeInfo()
+	b.WriteString(info.Name)
+	if opt.writeTypeID {
+		b.WriteRune('#')
+		b.WriteString(strconv.FormatInt(int64(info.ID), 16))
+	}
+	if info.Null {
+		b.WriteString("(nil)")
+		return
+	}
+
+	v := reflect.ValueOf(obj).Elem()
+	for i, f := range info.Fields {
+		if i == 0 && f.SchemaName == "flags" {
+			// Flag field, skipping.
+			continue
+		}
+		if f.Null {
+			// Optional field not set, skipping.
+			continue
+		}
+		b.WriteRune('\n')
+		b.WriteString(prefix)
+		b.WriteString(defaultIdent)
+		b.WriteString(f.SchemaName)
+		b.WriteString(": ")
+
+		formatValue(b, prefix, f.SchemaName, opt, v.FieldByName(f.Name))
+	}
+}
+
+// Format pretty-prints v into string.
+func Format(object Object, opts ...Option) string {
+	var opt options
+	for _, o := range opts {
+		o(&opt)
+	}
+
+	var b strings.Builder
+	format(&b, noIdent, opt, object)
+
+	return b.String()
+}