// Copyright 2019 Dolthub, Inc.
//
// 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 events

import (
	"context"
	"fmt"
)

type contextKeyT struct {
}

// contextEventKey key used for storing and retrieving an event from the context.
var contextEventKey = contextKeyT{}

// NewContextForEvent creates a new context with the event provided
func NewContextForEvent(ctx context.Context, evt *Event) context.Context {
	return context.WithValue(ctx, contextEventKey, evt)
}

// GetEventFromContext retrieves the event from the context if one exists.
func GetEventFromContext(ctx context.Context) *Event {
	val := ctx.Value(contextEventKey)

	if val == nil {
		return nil
	}

	evt, ok := val.(*Event)

	if !ok {
		panic(fmt.Errorf("value stored in context with key '%s' is not an event", contextEventKey))
	}

	return evt
}
