/***** BEGIN LICENSE BLOCK *****
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.
#
# The Initial Developer of the Original Code is the Mozilla Foundation.
# Portions created by the Initial Developer are Copyright (C) 2012
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
#   Ben Bangert (bbangert@mozilla.com)
#
# ***** END LICENSE BLOCK *****/

package cloudwatch

import (
	"encoding/xml"
	"errors"
	"fmt"
	"github.com/AdRoll/goamz/aws"
	"github.com/feyeleanor/sets"
	"strconv"
	"time"
)

// The CloudWatch type encapsulates all the CloudWatch operations in a region.
type CloudWatch struct {
	Service aws.AWSService
}

type Dimension struct {
	Name  string
	Value string
}

type StatisticSet struct {
	Maximum     float64
	Minimum     float64
	SampleCount float64
	Sum         float64
}

type MetricDatum struct {
	Dimensions      []Dimension
	MetricName      string
	StatisticValues *StatisticSet
	Timestamp       time.Time
	Unit            string
	Value           float64
}

type Datapoint struct {
	Average     float64
	Maximum     float64
	Minimum     float64
	SampleCount float64
	Sum         float64
	Timestamp   time.Time
	Unit        string
}

type GetMetricStatisticsRequest struct {
	Dimensions []Dimension
	EndTime    time.Time
	StartTime  time.Time
	MetricName string
	Unit       string
	Period     int
	Statistics []string
	Namespace  string
}

type GetMetricStatisticsResult struct {
	Datapoints []Datapoint `xml:"Datapoints>member"`
	NextToken  string      `xml:"NextToken"`
}

type GetMetricStatisticsResponse struct {
	GetMetricStatisticsResult GetMetricStatisticsResult
	ResponseMetadata          aws.ResponseMetadata
}

type Metric struct {
	Dimensions []Dimension `xml:"Dimensions>member"`
	MetricName string
	Namespace  string
}

type ListMetricsResult struct {
	Metrics   []Metric `xml:"Metrics>member"`
	NextToken string
}

type ListMetricsResponse struct {
	ListMetricsResult ListMetricsResult
	ResponseMetadata  aws.ResponseMetadata
}

type ListMetricsRequest struct {
	Dimensions []Dimension
	MetricName string
	Namespace  string
	NextToken  string
}

type AlarmAction struct {
	ARN string
}

type MetricAlarm struct {
	AlarmActions            []AlarmAction
	AlarmDescription        string
	AlarmName               string
	ComparisonOperator      string
	Dimensions              []Dimension
	EvaluationPeriods       int
	InsufficientDataActions []AlarmAction
	MetricName              string
	Namespace               string
	OKActions               []AlarmAction
	Period                  int
	Statistic               string
	Threshold               float64
	Unit                    string
}

var attempts = aws.AttemptStrategy{
	Min:   5,
	Total: 5 * time.Second,
	Delay: 200 * time.Millisecond,
}

const (
	UnitSeconds            string = "Seconds"
	UnitMicroseconds       string = "Microseconds"
	UnitMilliseconds       string = "Milliseconds"
	UnitBytes              string = "Bytes"
	UnitKilobytes          string = "Kilobytes"
	UnitMegabytes          string = "Megabytes"
	UnitGigabytes          string = "Gigabytes"
	UnitTerabytes          string = "Terabytes"
	UnitBits               string = "Bits"
	UnitKilobits           string = "Kilobits"
	UnitMegabits           string = "Megabits"
	UnitGigabits           string = "Gigabits"
	UnitTerabits           string = "Terabits"
	UnitPercent            string = "Percent"
	UnitCount              string = "Count"
	UnitBytesPerSecond     string = "Bytes/Second"
	UnitKilobytesPerSecond string = "Kilobytes/Second"
	UnitMegabytesPerSecond string = "Megabytes/Second"
	UnitGigabytesPerSecond string = "Gigabytes/Second"
	UnitTerabytesPerSecond string = "Terabytes/Second"
	UnitBitsPerSecond      string = "Bits/Second"
	UnitKilobitsPerSecond  string = "Kilobits/Second"
	UnitMegabitsPerSecond  string = "Megabits/Second"
	UnitGigabitsPerSecond  string = "Gigabits/Second"
	UnitTerabitsPerSecond  string = "Terabits/Second"
	UnitCountPerSecond     string = "Count/Second"
	UnitNone               string = "None"
)

var validUnits = sets.SSet(
	UnitSeconds,
	UnitMicroseconds,
	UnitMilliseconds,
	UnitBytes,
	UnitKilobytes,
	UnitMegabytes,
	UnitGigabytes,
	UnitTerabytes,
	UnitBits,
	UnitKilobits,
	UnitMegabits,
	UnitGigabits,
	UnitTerabits,
	UnitPercent,
	UnitCount,
	UnitBytesPerSecond,
	UnitKilobytesPerSecond,
	UnitMegabytesPerSecond,
	UnitGigabytesPerSecond,
	UnitTerabytesPerSecond,
	UnitBitsPerSecond,
	UnitKilobitsPerSecond,
	UnitMegabitsPerSecond,
	UnitGigabitsPerSecond,
	UnitTerabitsPerSecond,
	UnitCountPerSecond,
	UnitNone,
)

const (
	StatisticDatapointAverage     string = "Average"
	StatisticDatapointSum         string = "Sum"
	StatisticDatapointSampleCount string = "SampleCount"
	StatisticDatapointMaximum     string = "Maximum"
	StatisticDatapointMinimum     string = "Minimum"
)

var validMetricStatistics = sets.SSet(
	StatisticDatapointAverage,
	StatisticDatapointSum,
	StatisticDatapointSampleCount,
	StatisticDatapointMaximum,
	StatisticDatapointMinimum,
)

const (
	ComparisonOperatorLessThanThreshold             string = "LessThanThreshold"
	ComparisonOperatorLessThanOrEqualToThreshold    string = "LessThanOrEqualToThreshold"
	ComparisonOperatorGreaterThanThreshold          string = "GreaterThanThreshold"
	ComparisonOperatorGreaterThanOrEqualToThreshold string = "GreaterThanOrEqualToThreshold"
)

var validComparisonOperators = sets.SSet(
	ComparisonOperatorLessThanThreshold,
	ComparisonOperatorLessThanOrEqualToThreshold,
	ComparisonOperatorGreaterThanThreshold,
	ComparisonOperatorGreaterThanOrEqualToThreshold,
)

const (
	MetricNameCPUUtilization = "CPUUtilization"
)

// Create a new CloudWatch object for a given namespace
func NewCloudWatch(auth aws.Auth, region aws.ServiceInfo) (*CloudWatch, error) {
	service, err := aws.NewService(auth, region)
	if err != nil {
		return nil, err
	}
	return &CloudWatch{
		Service: service,
	}, nil
}

func (c *CloudWatch) query(method, path string, params map[string]string, resp interface{}) error {
	// Add basic Cloudwatch param
	params["Version"] = "2010-08-01"

	r, err := c.Service.Query(method, path, params)
	if err != nil {
		return err
	}
	defer r.Body.Close()

	if r.StatusCode != 200 {
		return c.Service.BuildError(r)
	}
	err = xml.NewDecoder(r.Body).Decode(resp)
	return err
}

// Get statistics for specified metric
//
// If the arguments are invalid or the server returns an error, the error will
// be set and the other values undefined.
func (c *CloudWatch) GetMetricStatistics(req *GetMetricStatisticsRequest) (result *GetMetricStatisticsResponse, err error) {
	statisticsSet := sets.SSet(req.Statistics...)
	// Kick out argument errors
	switch {
	case req.EndTime.IsZero():
		err = errors.New("No endTime specified")
	case req.StartTime.IsZero():
		err = errors.New("No startTime specified")
	case req.MetricName == "":
		err = errors.New("No metricName specified")
	case req.Namespace == "":
		err = errors.New("No Namespace specified")
	case req.Period < 60 || req.Period%60 != 0:
		err = errors.New("Period not 60 seconds or a multiple of 60 seconds")
	case len(req.Statistics) < 1:
		err = errors.New("No statistics supplied")
	case validMetricStatistics.Union(statisticsSet).Len() != validMetricStatistics.Len():
		err = errors.New("Invalid statistic values supplied")
	case req.Unit != "" && !validUnits.Member(req.Unit):
		err = errors.New("Unit is not a valid value")
	}
	if err != nil {
		return
	}

	// Serialize all the params
	params := aws.MakeParams("GetMetricStatistics")
	params["EndTime"] = req.EndTime.UTC().Format(time.RFC3339)
	params["StartTime"] = req.StartTime.UTC().Format(time.RFC3339)
	params["MetricName"] = req.MetricName
	params["Namespace"] = req.Namespace
	params["Period"] = strconv.Itoa(req.Period)
	if req.Unit != "" {
		params["Unit"] = req.Unit
	}

	// Serialize the lists of data
	for i, d := range req.Dimensions {
		prefix := "Dimensions.member." + strconv.Itoa(i+1)
		params[prefix+".Name"] = d.Name
		params[prefix+".Value"] = d.Value
	}
	for i, d := range req.Statistics {
		prefix := "Statistics.member." + strconv.Itoa(i+1)
		params[prefix] = d
	}
	result = new(GetMetricStatisticsResponse)
	err = c.query("GET", "/", params, result)
	return
}

// Returns a list of valid metrics stored for the AWS account owner.
// Returned metrics can be used with GetMetricStatistics to obtain statistical data for a given metric.

func (c *CloudWatch) ListMetrics(req *ListMetricsRequest) (result *ListMetricsResponse, err error) {

	// Serialize all the params
	params := aws.MakeParams("ListMetrics")
	if req.Namespace != "" {
		params["Namespace"] = req.Namespace
	}
	if req.MetricName != "" {
		params["MetricName"] = req.MetricName
	}
	if len(req.Dimensions) > 0 {
		for i, d := range req.Dimensions {
			prefix := "Dimensions.member." + strconv.Itoa(i+1)
			params[prefix+".Name"] = d.Name
			if len(d.Value) > 0 {
				params[prefix+".Value"] = d.Value
			}
		}
	}

	result = new(ListMetricsResponse)
	err = c.query("GET", "/", params, &result)
	metrics := result.ListMetricsResult.Metrics
	if result.ListMetricsResult.NextToken != "" {
		for result.ListMetricsResult.NextToken != "" && err == nil {
			params = aws.MakeParams("ListMetrics")
			params["NextToken"] = result.ListMetricsResult.NextToken
			result = new(ListMetricsResponse)
			err = c.query("GET", "/", params, &result)
			if err == nil {
				newslice := make([]Metric, len(metrics)+len(result.ListMetricsResult.Metrics))
				copy(newslice, metrics)
				copy(newslice[len(metrics):], result.ListMetricsResult.Metrics)
				metrics = newslice
			}
		}
		result.ListMetricsResult.Metrics = metrics
	}
	return
}

func (c *CloudWatch) PutMetricData(metrics []MetricDatum) (result *aws.BaseResponse, err error) {
	return c.PutMetricDataNamespace(metrics, "")
}

func (c *CloudWatch) PutMetricDataNamespace(metrics []MetricDatum, namespace string) (result *aws.BaseResponse, err error) {
	// Serialize the params
	params := aws.MakeParams("PutMetricData")
	if namespace != "" {
		params["Namespace"] = namespace
	}
	for i, metric := range metrics {
		prefix := "MetricData.member." + strconv.Itoa(i+1)
		if metric.MetricName == "" {
			err = fmt.Errorf("No metric name supplied for metric: %d", i)
			return
		}
		params[prefix+".MetricName"] = metric.MetricName
		if metric.Unit != "" {
			params[prefix+".Unit"] = metric.Unit
		}
		if metric.Value != 0 {
			params[prefix+".Value"] = strconv.FormatFloat(metric.Value, 'E', 10, 64)
		} else if metric.StatisticValues == nil {
			params[prefix+".Value"] = "0"
		}
		if !metric.Timestamp.IsZero() {
			params[prefix+".Timestamp"] = metric.Timestamp.UTC().Format(time.RFC3339)
		}
		for j, dim := range metric.Dimensions {
			dimprefix := prefix + ".Dimensions.member." + strconv.Itoa(j+1)
			params[dimprefix+".Name"] = dim.Name
			params[dimprefix+".Value"] = dim.Value
		}
		if metric.StatisticValues != nil {
			statprefix := prefix + ".StatisticValues"
			params[statprefix+".Maximum"] = strconv.FormatFloat(metric.StatisticValues.Maximum, 'E', 10, 64)
			params[statprefix+".Minimum"] = strconv.FormatFloat(metric.StatisticValues.Minimum, 'E', 10, 64)
			params[statprefix+".SampleCount"] = strconv.FormatFloat(metric.StatisticValues.SampleCount, 'E', 10, 64)
			params[statprefix+".Sum"] = strconv.FormatFloat(metric.StatisticValues.Sum, 'E', 10, 64)
		}
	}
	result = new(aws.BaseResponse)
	err = c.query("POST", "/", params, result)
	return
}

func (c *CloudWatch) PutMetricAlarm(alarm *MetricAlarm) (result *aws.BaseResponse, err error) {
	// Serialize the params
	params := aws.MakeParams("PutMetricAlarm")

	switch {
	case alarm.AlarmName == "":
		err = errors.New("No AlarmName supplied")
	case !validComparisonOperators.Member(alarm.ComparisonOperator):
		err = errors.New("ComparisonOperator is not valid")
	case alarm.EvaluationPeriods == 0:
		err = errors.New("No number of EvaluationPeriods specified")
	case alarm.MetricName == "":
		err = errors.New("No MetricName specified")
	case alarm.Namespace == "":
		err = errors.New("No Namespace specified")
	case alarm.Period == 0:
		err = errors.New("No Period over which statistic should apply was specified")
	case !validMetricStatistics.Member(alarm.Statistic):
		err = errors.New("Invalid statistic value supplied")
	case alarm.Threshold == 0:
		err = errors.New("No Threshold value specified")
	case alarm.Unit != "" && !validUnits.Member(alarm.Unit):
		err = errors.New("Unit is not a valid value")
	}
	if err != nil {
		return
	}

	for i, action := range alarm.AlarmActions {
		params["AlarmActions.member."+strconv.Itoa(i+1)] = action.ARN
	}
	for i, action := range alarm.InsufficientDataActions {
		params["InsufficientDataActions.member."+strconv.Itoa(i+1)] = action.ARN
	}
	for i, action := range alarm.OKActions {
		params["OKActions.member."+strconv.Itoa(i+1)] = action.ARN
	}
	if alarm.AlarmDescription != "" {
		params["AlarmDescription"] = alarm.AlarmDescription
	}
	params["AlarmName"] = alarm.AlarmName
	params["ComparisonOperator"] = alarm.ComparisonOperator
	for i, dim := range alarm.Dimensions {
		dimprefix := "Dimensions.member." + strconv.Itoa(i+1)
		params[dimprefix+".Name"] = dim.Name
		params[dimprefix+".Value"] = dim.Value
	}
	params["EvaluationPeriods"] = strconv.Itoa(alarm.EvaluationPeriods)
	params["MetricName"] = alarm.MetricName
	params["Namespace"] = alarm.Namespace
	params["Period"] = strconv.Itoa(alarm.Period)
	params["Statistic"] = alarm.Statistic
	params["Threshold"] = strconv.FormatFloat(alarm.Threshold, 'E', 10, 64)
	if alarm.Unit != "" {
		params["Unit"] = alarm.Unit
	}

	result = new(aws.BaseResponse)
	err = c.query("POST", "/", params, result)
	return
}