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/gen/generator.go

@@ -0,0 +1,89 @@
+package gen
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+
+	"github.com/go-faster/errors"
+
+	"github.com/gotd/getdoc"
+	"github.com/gotd/tl"
+)
+
+func definitionType(d tl.Definition) string {
+	if len(d.Namespace) == 0 {
+		return d.Name
+	}
+	return fmt.Sprintf("%s.%s", strings.Join(d.Namespace, "."), d.Name)
+}
+
+// Generator generates go types from tl.Schema.
+type Generator struct {
+	schema *tl.Schema
+
+	// classes type bindings, key is TL type.
+	classes map[string]classBinding
+	// types bindings, key is TL type.
+	types map[string]typeBinding
+
+	// structs definitions.
+	structs []structDef
+	// interfaces definitions.
+	interfaces []interfaceDef
+	// errorChecks definitions.
+	errorChecks []errCheckDef
+
+	// constructor mappings.
+	mappings map[string][]constructorMapping
+
+	// registry of type ids.
+	registry []bindingDef
+
+	// docBase is base url for documentation.
+	docBase      *url.URL
+	doc          *getdoc.Doc
+	docLineLimit int
+
+	generateFlags GenerateFlags
+}
+
+// NewGenerator initializes and returns new Generator from tl.Schema.
+func NewGenerator(s *tl.Schema, genOpt GeneratorOptions) (*Generator, error) {
+	genOpt.setDefaults()
+	g := &Generator{
+		schema:        s,
+		classes:       map[string]classBinding{},
+		types:         map[string]typeBinding{},
+		mappings:      map[string][]constructorMapping{},
+		docLineLimit:  genOpt.DocLineLimit,
+		generateFlags: genOpt.GenerateFlags,
+	}
+	if genOpt.DocBaseURL != "" {
+		u, err := url.Parse(genOpt.DocBaseURL)
+		if err != nil {
+			return nil, errors.Wrap(err, "parse docBase")
+		}
+		g.docBase = u
+
+		if u.Host == "core.telegram.org" {
+			// Using embedded documentation.
+			// TODO(ernado): Get actual layer
+			doc, err := getdoc.Load(getdoc.LayerLatest)
+			if err != nil {
+				return nil, errors.Wrap(err, "get documentation")
+			}
+			g.doc = doc
+		}
+	}
+	if err := g.makeBindings(); err != nil {
+		return nil, errors.Wrap(err, "make type bindings")
+	}
+	if err := g.makeStructures(); err != nil {
+		return nil, errors.Wrap(err, "generate go structures")
+	}
+	g.makeInterfaces()
+	g.makeErrors()
+
+	return g, nil
+}