adapter/products.go

/*
Copyright 2017 Google 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 adapter

import (
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/apid/istioApigeeAdapter/common"
)

const (
	defaultProductsFetch = time.Minute
)

type productManager struct {
	fetchURL   string
	products   map[string]*common.APIProduct
	refresh    time.Duration
	expiration time.Time
	latch      *sync.Mutex
}

func newProductManager(fetchURL string, refreshTime time.Duration) *productManager {
	return &productManager{
		fetchURL: fetchURL,
		refresh:  refreshTime,
		latch:    &sync.Mutex{},
	}
}

/*
getProducts returns the products that match a list of names. For now it is simple -- we will
use a mutex and update the list when it's expired. In the future we can be fancier with
periodic refresh.
*/
func (m *productManager) getProducts(names []string) ([]common.APIProduct, error) {
	m.latch.Lock()
	defer m.latch.Unlock()

	if m.products == nil || m.expiration.Before(time.Now()) {
		err := m.fetchProductList()
		if err != nil {
			return nil, err
		}
	}

	var products []common.APIProduct
	for _, name := range names {
		p := m.products[name]
		if p != nil {
			products = append(products, *p)
		}
	}
	return products, nil
}

func (m *productManager) fetchProductList() error {
	resp, err := http.Get(m.fetchURL)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return fmt.Errorf("HTTP error %d fetching API product list", resp.StatusCode)
	}

	var pl common.APIProductResponse
	jr := json.NewDecoder(resp.Body)
	err = jr.Decode(&pl)
	if err != nil {
		return err
	}

	m.products = make(map[string]*common.APIProduct)
	for _, p := range pl.Products {
		m.products[p.Name] = &p
	}
	m.expiration = time.Now().Add(m.refresh)
	return nil
}