// Copyright 2014 Prometheus Team
// 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 local

import (
	"time"

	clientmodel "github.com/prometheus/client_golang/model"
)

// memorySeriesPreloader is a Preloader for the memorySeriesStorage.
type memorySeriesPreloader struct {
	storage          *memorySeriesStorage
	pinnedChunkDescs []*chunkDesc
}

// PreloadRange implements Preloader.
func (p *memorySeriesPreloader) PreloadRange(
	fp clientmodel.Fingerprint,
	from clientmodel.Timestamp, through clientmodel.Timestamp,
	stalenessDelta time.Duration,
) error {
	cds, err := p.storage.preloadChunksForRange(fp, from, through, stalenessDelta)
	if err != nil {
		return err
	}
	p.pinnedChunkDescs = append(p.pinnedChunkDescs, cds...)
	return nil
}

/*
// GetMetricAtTime implements Preloader.
func (p *memorySeriesPreloader) GetMetricAtTime(fp clientmodel.Fingerprint, t clientmodel.Timestamp) error {
	cds, err := p.storage.preloadChunks(fp, &timeSelector{
		from:    t,
		through: t,
	})
	if err != nil {
		return err
	}
	p.pinnedChunkDescs = append(p.pinnedChunkDescs, cds...)
	return nil
}

// GetMetricAtInterval implements Preloader.
func (p *memorySeriesPreloader) GetMetricAtInterval(fp clientmodel.Fingerprint, from, through clientmodel.Timestamp, interval time.Duration) error {
	cds, err := p.storage.preloadChunks(fp, &timeSelector{
		from:     from,
		through:  through,
		interval: interval,
	})
	if err != nil {
		return err
	}
	p.pinnedChunkDescs = append(p.pinnedChunkDescs, cds...)
	return
}

// GetMetricRange implements Preloader.
func (p *memorySeriesPreloader) GetMetricRange(fp clientmodel.Fingerprint, t clientmodel.Timestamp, rangeDuration time.Duration) error {
	cds, err := p.storage.preloadChunks(fp, &timeSelector{
		from:          t,
		through:       t,
		rangeDuration: through.Sub(from),
	})
	if err != nil {
		return err
	}
	p.pinnedChunkDescs = append(p.pinnedChunkDescs, cds...)
	return
}

// GetMetricRangeAtInterval implements Preloader.
func (p *memorySeriesPreloader) GetMetricRangeAtInterval(fp clientmodel.Fingerprint, from, through clientmodel.Timestamp, interval, rangeDuration time.Duration) error {
	cds, err := p.storage.preloadChunks(fp, &timeSelector{
		from:          from,
		through:       through,
		interval:      interval,
		rangeDuration: rangeDuration,
	})
	if err != nil {
		return err
	}
	p.pinnedChunkDescs = append(p.pinnedChunkDescs, cds...)
	return
}
*/

// Close implements Preloader.
func (p *memorySeriesPreloader) Close() {
	// TODO: Idea about a primitive but almost free heuristic to not evict
	// "recently used" chunks: Do not unpin the chunks right here, but hand
	// over the pinnedChunkDescs to a manager that will delay the unpinning
	// based on time and memory pressure.
	for _, cd := range p.pinnedChunkDescs {
		cd.unpin()
	}
}