/*
Copyright 2014 Google Inc. All rights reserved.

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.
*/

// Reads the configuration from the file. Example file for two services [nodejs & mysql]
//{"Services": [
//   {
//      "Name":"nodejs",
//      "Port":10000,
//      "Endpoints":["10.240.180.168:8000", "10.240.254.199:8000", "10.240.62.150:8000"]
//   },
//   {
//      "Name":"mysql",
//      "Port":10001,
//      "Endpoints":["10.240.180.168:9000", "10.240.254.199:9000", "10.240.62.150:9000"]
//   }
//]
//}
package config

import (
	"bytes"
	"encoding/json"
	"io/ioutil"
	"log"
	"reflect"
	"time"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
)

// TODO: kill this struct.
type ServiceJSON struct {
	Name      string
	Port      int
	Endpoints []string
}
type ConfigFile struct {
	Services []ServiceJSON
}

type ConfigSourceFile struct {
	serviceChannel   chan ServiceUpdate
	endpointsChannel chan EndpointsUpdate
	filename         string
}

func NewConfigSourceFile(filename string, serviceChannel chan ServiceUpdate, endpointsChannel chan EndpointsUpdate) ConfigSourceFile {
	config := ConfigSourceFile{
		filename:         filename,
		serviceChannel:   serviceChannel,
		endpointsChannel: endpointsChannel,
	}
	go config.Run()
	return config
}

func (impl ConfigSourceFile) Run() {
	log.Printf("Watching file %s", impl.filename)
	var lastData []byte
	var lastServices []api.Service
	var lastEndpoints []api.Endpoints

	for {
		data, err := ioutil.ReadFile(impl.filename)
		if err != nil {
			log.Printf("Couldn't read file: %s : %v", impl.filename, err)
		} else {
			var config ConfigFile
			err = json.Unmarshal(data, &config)
			if err != nil {
				log.Printf("Couldn't unmarshal configuration from file : %s %v", data, err)
			} else {
				if !bytes.Equal(lastData, data) {
					lastData = data
					// Ok, we have a valid configuration, send to channel for
					// rejiggering.
					newServices := make([]api.Service, len(config.Services))
					newEndpoints := make([]api.Endpoints, len(config.Services))
					for i, service := range config.Services {
						newServices[i] = api.Service{JSONBase: api.JSONBase{ID: service.Name}, Port: service.Port}
						newEndpoints[i] = api.Endpoints{Name: service.Name, Endpoints: service.Endpoints}
					}
					if !reflect.DeepEqual(lastServices, newServices) {
						serviceUpdate := ServiceUpdate{Op: SET, Services: newServices}
						impl.serviceChannel <- serviceUpdate
						lastServices = newServices
					}
					if !reflect.DeepEqual(lastEndpoints, newEndpoints) {
						endpointsUpdate := EndpointsUpdate{Op: SET, Endpoints: newEndpoints}
						impl.endpointsChannel <- endpointsUpdate
						lastEndpoints = newEndpoints
					}
				}
			}
		}
		time.Sleep(5 * time.Second)
	}
}