hugo/hugolib/scratch.go

// Copyright © 2013-14 Steve Francia <spf@spf13.com>.
//
// Licensed under the Simple Public 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://opensource.org/licenses/Simple-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 hugolib

import (
	"github.com/spf13/hugo/helpers"
)

// Scratch is a writable context used for stateful operations in Page/Node rendering.
type Scratch struct {
	values map[string]interface{}
}

// Add will add (using the + operator) the addend to the existing addend (if found).
// Supports numeric values and strings.
func (c *Scratch) Add(key string, newAddend interface{}) (string, error) {
	var newVal interface{}
	existingAddend, found := c.values[key]
	if found {
		var err error
		newVal, err = helpers.DoArithmetic(existingAddend, newAddend, '+')
		if err != nil {
			return "", err
		}
	} else {
		newVal = newAddend
	}
	c.values[key] = newVal
	return "", nil // have to return something to make it work with the Go templates
}

// Set stores a value with the given key in the Node context.
// This value can later be retrieved with Get.
func (c *Scratch) Set(key string, value interface{}) string {
	c.values[key] = value
	return ""
}

// Get returns a value previously set by Add or Set
func (c *Scratch) Get(key string) interface{} {
	return c.values[key]
}

func newScratch() *Scratch {
	return &Scratch{values: make(map[string]interface{})}
}