// Copyright 2015 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.

package collector

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"regexp"
	"time"

	"github.com/google/cadvisor/info/v2"
)

type GenericCollector struct {
	//name of the collector
	name string

	//holds information extracted from the config file for a collector
	configFile Config

	//holds information necessary to extract metrics
	info *collectorInfo
}

type collectorInfo struct {
	//minimum polling frequency among all metrics
	minPollingFrequency time.Duration

	//regular expresssions for all metrics
	regexps []*regexp.Regexp
}

//Returns a new collector using the information extracted from the configfile
func NewCollector(collectorName string, configfile string) (*GenericCollector, error) {
	configFile, err := ioutil.ReadFile(configfile)
	if err != nil {
		return nil, err
	}

	var configInJSON Config
	err = json.Unmarshal(configFile, &configInJSON)
	if err != nil {
		return nil, err
	}

	//TODO : Add checks for validity of config file (eg : Accurate JSON fields)

	if len(configInJSON.MetricsConfig) == 0 {
		return nil, fmt.Errorf("No metrics provided in config")
	}

	minPollFrequency := configInJSON.MetricsConfig[0].PollingFrequency
	regexprs := make([]*regexp.Regexp, len(configInJSON.MetricsConfig))

	for ind, metricConfig := range configInJSON.MetricsConfig {
		if metricConfig.PollingFrequency < minPollFrequency {
			minPollFrequency = metricConfig.PollingFrequency
		}

		regexprs[ind], err = regexp.Compile(metricConfig.Regex)
		if err != nil {
			return nil, fmt.Errorf("Invalid regexp %v for metric %v", metricConfig.Regex, metricConfig.Name)
		}
	}

	return &GenericCollector{
		name:       collectorName,
		configFile: configInJSON,
		info: &collectorInfo{
			minPollingFrequency: minPollFrequency,
			regexps:             regexprs},
	}, nil
}

//Returns name of the collector
func (collector *GenericCollector) Name() string {
	return collector.name
}

//Returns collected metrics and the next collection time of the collector
func (collector *GenericCollector) Collect() (time.Time, []v2.Metric, error) {
	//TO BE IMPLEMENTED
	return time.Now(), nil, nil
}