// Copyright 2013 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 metric

import (
	"sort"
	"time"

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

var (
	// firstSupertime is the smallest valid supertime that may be seeked to.
	firstSupertime = []byte{0, 0, 0, 0, 0, 0, 0, 0}
	// lastSupertime is the largest valid supertime that may be seeked to.
	lastSupertime = []byte{127, 255, 255, 255, 255, 255, 255, 255}
)

// Represents the summation of all datastore queries that shall be performed to
// extract values.  Each operation mutates the state of the builder.
type ViewRequestBuilder interface {
	GetMetricAtTime(fingerprint *clientmodel.Fingerprint, time time.Time)
	GetMetricAtInterval(fingerprint *clientmodel.Fingerprint, from, through time.Time, interval time.Duration)
	GetMetricRange(fingerprint *clientmodel.Fingerprint, from, through time.Time)
	ScanJobs() scanJobs
}

// Contains the various unoptimized requests for data.
type viewRequestBuilder struct {
	operations map[clientmodel.Fingerprint]ops
}

// Furnishes a ViewRequestBuilder for remarking what types of queries to perform.
func NewViewRequestBuilder() *viewRequestBuilder {
	return &viewRequestBuilder{
		operations: make(map[clientmodel.Fingerprint]ops),
	}
}

// Gets for the given Fingerprint either the value at that time if there is an
// match or the one or two values adjacent thereto.
func (v *viewRequestBuilder) GetMetricAtTime(fingerprint *clientmodel.Fingerprint, time time.Time) {
	ops := v.operations[*fingerprint]
	ops = append(ops, &getValuesAtTimeOp{
		time: time,
	})
	v.operations[*fingerprint] = ops
}

// Gets for the given Fingerprint either the value at that interval from From
// through Through  if there is an match or the one or two values adjacent
// for each point.
func (v *viewRequestBuilder) GetMetricAtInterval(fingerprint *clientmodel.Fingerprint, from, through time.Time, interval time.Duration) {
	ops := v.operations[*fingerprint]
	ops = append(ops, &getValuesAtIntervalOp{
		from:     from,
		through:  through,
		interval: interval,
	})
	v.operations[*fingerprint] = ops
}

// Gets for the given Fingerprint the values that occur inclusively from From
// through Through.
func (v *viewRequestBuilder) GetMetricRange(fingerprint *clientmodel.Fingerprint, from, through time.Time) {
	ops := v.operations[*fingerprint]
	ops = append(ops, &getValuesAlongRangeOp{
		from:    from,
		through: through,
	})
	v.operations[*fingerprint] = ops
}

// Gets value ranges at intervals for the given Fingerprint:
//
//   |----|       |----|       |----|       |----|
//   ^    ^            ^       ^    ^            ^
//   |    \------------/       \----/            |
//  from     interval       rangeDuration     through
func (v *viewRequestBuilder) GetMetricRangeAtInterval(fingerprint *clientmodel.Fingerprint, from, through time.Time, interval, rangeDuration time.Duration) {
	ops := v.operations[*fingerprint]
	ops = append(ops, &getValueRangeAtIntervalOp{
		rangeFrom:     from,
		rangeThrough:  from.Add(rangeDuration),
		rangeDuration: rangeDuration,
		interval:      interval,
		through:       through,
	})
	v.operations[*fingerprint] = ops
}

// Emits the optimized scans that will occur in the data store.  This
// effectively resets the ViewRequestBuilder back to a pristine state.
func (v *viewRequestBuilder) ScanJobs() (j scanJobs) {
	for fingerprint, operations := range v.operations {
		sort.Sort(startsAtSort{operations})

		fpCopy := fingerprint
		j = append(j, scanJob{
			fingerprint: &fpCopy,
			// BUG: Evaluate whether we need to implement an optimize() working also
			// for getValueRangeAtIntervalOp and use it here instead of just passing
			// through the list of ops as-is.
			operations: operations,
		})

		delete(v.operations, fingerprint)
	}

	sort.Sort(j)

	return
}

type view struct {
	*memorySeriesStorage
}

func (v view) appendSamples(fingerprint *clientmodel.Fingerprint, samples Values) {
	v.memorySeriesStorage.appendSamplesWithoutIndexing(fingerprint, samples)
}

func newView() view {
	return view{NewMemorySeriesStorage(MemorySeriesOptions{})}
}