// Copyright 2017 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package protostruct supports operations on the protocol buffer Struct message.
package protostruct

import (
	pb "github.com/golang/protobuf/ptypes/struct"
)

// DecodeToMap converts a pb.Struct to a map from strings to Go types.
// DecodeToMap panics if s is invalid.
func DecodeToMap(s *pb.Struct) map[string]interface{} {
	if s == nil {
		return nil
	}
	m := map[string]interface{}{}
	for k, v := range s.Fields {
		m[k] = decodeValue(v)
	}
	return m
}

func decodeValue(v *pb.Value) interface{} {
	switch k := v.Kind.(type) {
	case *pb.Value_NullValue:
		return nil
	case *pb.Value_NumberValue:
		return k.NumberValue
	case *pb.Value_StringValue:
		return k.StringValue
	case *pb.Value_BoolValue:
		return k.BoolValue
	case *pb.Value_StructValue:
		return DecodeToMap(k.StructValue)
	case *pb.Value_ListValue:
		s := make([]interface{}, len(k.ListValue.Values))
		for i, e := range k.ListValue.Values {
			s[i] = decodeValue(e)
		}
		return s
	default:
		panic("protostruct: unknown kind")
	}
}