// 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.

package container

import (
	"math/big"
	"sync"
	"time"

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

type statsSummaryContainerHandlerWrapper struct {
	handler          ContainerHandler
	currentSummary   *info.ContainerStatsSummary
	totalMemoryUsage *big.Int
	numStats         uint64
	sampler          sampling.Sampler
	lock             sync.Mutex
}

func (self *statsSummaryContainerHandlerWrapper) GetSpec() (*info.ContainerSpec, error) {
	return self.handler.GetSpec()
}

func (self *statsSummaryContainerHandlerWrapper) GetStats() (*info.ContainerStats, error) {
	stats, err := self.handler.GetStats()
	if err != nil {
		return nil, err
	}
	if stats == nil {
		return nil, nil
	}
	stats.Timestamp = time.Now()
	self.lock.Lock()
	defer self.lock.Unlock()

	self.sampler.Update(stats)
	if self.currentSummary == nil {
		self.currentSummary = new(info.ContainerStatsSummary)
	}
	self.numStats++
	if stats.Memory != nil {
		if stats.Memory.Usage > self.currentSummary.MaxMemoryUsage {
			self.currentSummary.MaxMemoryUsage = stats.Memory.Usage
		}

		// XXX(dengnan): Very inefficient!
		if self.totalMemoryUsage == nil {
			self.totalMemoryUsage = new(big.Int)
		}
		usage := (&big.Int{}).SetUint64(stats.Memory.Usage)
		self.totalMemoryUsage = self.totalMemoryUsage.Add(self.totalMemoryUsage, usage)
		n := (&big.Int{}).SetUint64(self.numStats)
		avg := (&big.Int{}).Div(self.totalMemoryUsage, n)
		self.currentSummary.AvgMemoryUsage = avg.Uint64()
	}
	return stats, nil
}

func (self *statsSummaryContainerHandlerWrapper) ListContainers(listType ListType) ([]string, error) {
	return self.handler.ListContainers(listType)
}

func (self *statsSummaryContainerHandlerWrapper) ListThreads(listType ListType) ([]int, error) {
	return self.handler.ListThreads(listType)
}

func (self *statsSummaryContainerHandlerWrapper) ListProcesses(listType ListType) ([]int, error) {
	return self.handler.ListProcesses(listType)
}

func (self *statsSummaryContainerHandlerWrapper) StatsSummary() (*info.ContainerStatsSummary, error) {
	self.lock.Lock()
	defer self.lock.Unlock()
	samples := make([]*info.ContainerStats, 0, self.sampler.Len())
	self.sampler.Map(func(d interface{}) {
		stats := d.(*info.ContainerStats)
		samples = append(samples, stats)
	})
	self.currentSummary.Samples = samples
	// XXX(dengnan): propabily add to StatsParameter?
	self.currentSummary.FillPercentiles(
		[]int{50, 80, 90, 95, 99},
		[]int{50, 80, 90, 95, 99},
	)
	return self.currentSummary, nil
}

type StatsParameter struct {
	Sampler     string
	NumSamples  int
	WindowSize  int
	ResetPeriod time.Duration
}

func AddStatsSummary(handler ContainerHandler, parameter *StatsParameter) (ContainerHandler, error) {
	sampler, err := NewSampler(parameter)
	if err != nil {
		return nil, err
	}
	return &statsSummaryContainerHandlerWrapper{
		handler:        handler,
		currentSummary: &info.ContainerStatsSummary{},
		sampler:        sampler,
	}, nil
}