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/fields.go

@@ -0,0 +1,127 @@
+package gen
+
+import (
+	"strings"
+)
+
+func optionalField(s structDef, f fieldDef) bool {
+	switch {
+	case f.Conditional:
+		return true
+	case f.Type == "string" && f.Name == "ThumbSize":
+		return s.RawName == "inputDocumentFileLocation"
+	}
+
+	return false
+}
+
+func hasField(fields []fieldDef, name, typ string) bool {
+	for _, f := range fields {
+		if f.Name == name && f.Type == typ {
+			return true
+		}
+	}
+
+	return false
+}
+
+func mappableFields(constructor, to structDef) (constructorMapping, bool) {
+	var r []fieldPair
+	mapped := map[string]struct{}{}
+	for _, a := range constructor.Fields {
+		if a.Type == flagsType {
+			continue
+		}
+
+		for _, b := range to.Fields {
+			if b.Type == flagsType {
+				continue
+			}
+
+			if a.SameType(b) && strings.Contains(b.Name, a.Name) {
+				r = append(r, fieldPair{a, b})
+				mapped[b.Name] = struct{}{}
+			}
+		}
+	}
+
+	// Return false if we can't fill all fields.
+	if len(mapped) != len(to.Fields) {
+		for _, field := range to.Fields {
+			if _, ok := mapped[field.Name]; !ok && !optionalField(to, field) {
+				return constructorMapping{}, false
+			}
+		}
+	}
+
+	mapperName := to.Name
+	// Mapping: User => InputUser, so mapperName = "Input"
+	// Mapping: Document => InputDocumentFileLocation, so mapperName = "InputDocumentFileLocation"
+	if strings.HasSuffix(to.Name, constructor.Name) {
+		mapperName = strings.TrimSuffix(to.Name, constructor.Name)
+	}
+
+	mapping := constructorMapping{
+		Name:        to.Name,
+		Constructor: constructor.Name,
+		Concrete:    true,
+		MapperName:  mapperName,
+		Fields:      r,
+	}
+
+	return mapping, true
+}
+
+func intersectFields(a, b []fieldDef) []fieldDef {
+	return intersectFieldsBy(a, b, fieldDef.EqualAsField)
+}
+
+func intersectFieldsBy(a, b []fieldDef, compare func(a, b fieldDef) bool) []fieldDef {
+	// If a is empty, copy all from b to a.
+	if a == nil {
+		a = make([]fieldDef, len(b))
+		copy(a, b)
+	} else { // Otherwise intersect.
+		a = commonFields(a, b, compare)
+	}
+
+	return filterFields(a, func(def fieldDef) bool {
+		// Filter bin.Flags fields.
+		return def.Type != flagsType
+	})
+}
+
+func commonFields(a, b []fieldDef, compare func(a, b fieldDef) bool) []fieldDef {
+	return filterFields(a, func(def fieldDef) bool {
+		for _, x := range b {
+			if compare(x, def) {
+				return true
+			}
+		}
+
+		return false
+	})
+}
+
+func filterFields(a []fieldDef, filter func(def fieldDef) bool) []fieldDef {
+	n := 0
+	for _, f := range a {
+		if filter(f) {
+			a[n] = f
+			n++
+		}
+	}
+	a = a[:n]
+
+	return a
+}
+
+func filterFieldsTo(a, b []fieldDef, filter func(def fieldDef) bool) []fieldDef {
+	for _, f := range a {
+		if filter(f) {
+			b = append(b, f)
+		}
+	}
+
+	return b
+}