// Source: https://github.com/distribution/distribution

// Copyright 2014 https://github.com/distribution/distribution Authors
//
// 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 dcontext

import (
	"context"
	"time"
)

// Since looks up key, which should be a time.Time, and returns the duration
// since that time. If the key is not found, the value returned will be zero.
// This is helpful when inferring metrics related to context execution times.
func Since(ctx context.Context, key interface{}) time.Duration {
	if startedAt, ok := ctx.Value(key).(time.Time); ok {
		return time.Since(startedAt)
	}
	return 0
}

// GetStringValue returns a string value from the context. The empty string
// will be returned if not found.
func GetStringValue(ctx context.Context, key interface{}) (value string) {
	if valuev, ok := ctx.Value(key).(string); ok {
		value = valuev
	}
	return value
}