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// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package proto
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import (
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	"google.golang.org/protobuf/reflect/protoreflect"
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)
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// HasExtension reports whether an extension field is populated.
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// It returns false if m is invalid or if xt does not extend m.
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func HasExtension(m Message, xt protoreflect.ExtensionType) bool {
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	// Treat nil message interface as an empty message; no populated fields.
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	if m == nil {
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		return false
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	}
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	// As a special-case, we reports invalid or mismatching descriptors
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	// as always not being populated (since they aren't).
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	if xt == nil || m.ProtoReflect().Descriptor() != xt.TypeDescriptor().ContainingMessage() {
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		return false
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	}
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	return m.ProtoReflect().Has(xt.TypeDescriptor())
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}
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// ClearExtension clears an extension field such that subsequent
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// HasExtension calls return false.
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// It panics if m is invalid or if xt does not extend m.
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func ClearExtension(m Message, xt protoreflect.ExtensionType) {
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	m.ProtoReflect().Clear(xt.TypeDescriptor())
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}
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// GetExtension retrieves the value for an extension field.
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// If the field is unpopulated, it returns the default value for
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// scalars and an immutable, empty value for lists or messages.
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// It panics if xt does not extend m.
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func GetExtension(m Message, xt protoreflect.ExtensionType) interface{} {
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	// Treat nil message interface as an empty message; return the default.
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	if m == nil {
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		return xt.InterfaceOf(xt.Zero())
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	}
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	return xt.InterfaceOf(m.ProtoReflect().Get(xt.TypeDescriptor()))
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}
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// SetExtension stores the value of an extension field.
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// It panics if m is invalid, xt does not extend m, or if type of v
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// is invalid for the specified extension field.
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func SetExtension(m Message, xt protoreflect.ExtensionType, v interface{}) {
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	xd := xt.TypeDescriptor()
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	pv := xt.ValueOf(v)
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	// Specially treat an invalid list, map, or message as clear.
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	isValid := true
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	switch {
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	case xd.IsList():
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		isValid = pv.List().IsValid()
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	case xd.IsMap():
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		isValid = pv.Map().IsValid()
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	case xd.Message() != nil:
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		isValid = pv.Message().IsValid()
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	}
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	if !isValid {
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		m.ProtoReflect().Clear(xd)
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		return
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	}
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	m.ProtoReflect().Set(xd, pv)
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}
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// RangeExtensions iterates over every populated extension field in m in an
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// undefined order, calling f for each extension type and value encountered.
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// It returns immediately if f returns false.
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// While iterating, mutating operations may only be performed
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// on the current extension field.
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func RangeExtensions(m Message, f func(protoreflect.ExtensionType, interface{}) bool) {
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	// Treat nil message interface as an empty message; nothing to range over.
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	if m == nil {
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		return
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	}
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	m.ProtoReflect().Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
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		if fd.IsExtension() {
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			xt := fd.(protoreflect.ExtensionTypeDescriptor).Type()
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			vi := xt.InterfaceOf(v)
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			return f(xt, vi)
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		}
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		return true
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	})
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}
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