// Copyright 2020 Douyu
//
// 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 trace

import (
	"strings"
)

// MetadataReaderWriter ...
type MetadataReaderWriter struct {
	MD map[string][]string
}

// Set ...
func (w MetadataReaderWriter) Set(key, val string) {
	key = strings.ToLower(key)
	w.MD[key] = append(w.MD[key], val)
}

// ForeachKey ...
func (w MetadataReaderWriter) ForeachKey(handler func(key, val string) error) error {
	for k, vals := range w.MD {
		for _, v := range vals {
			if err := handler(k, v); err != nil {
				return err
			}
		}
	}

	return nil
}
