// Copyright 2018 The Prometheus Authors
// 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 tsdbutil

import (
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/tsdb/chunks"
)

type Samples interface {
	Get(i int) Sample
	Len() int
}

type Sample interface {
	T() int64
	V() float64
}

type SampleSlice []Sample

func (s SampleSlice) Get(i int) Sample { return s[i] }
func (s SampleSlice) Len() int         { return len(s) }

func ChunkFromSamples(s []Sample) chunks.Meta {
	return ChunkFromSamplesGeneric(SampleSlice(s))
}

func ChunkFromSamplesGeneric(s Samples) chunks.Meta {
	mint, maxt := int64(0), int64(0)

	if s.Len() > 0 {
		mint, maxt = s.Get(0).T(), s.Get(s.Len()-1).T()
	}

	c := chunkenc.NewXORChunk()
	ca, _ := c.Appender()

	for i := 0; i < s.Len(); i++ {
		ca.Append(s.Get(i).T(), s.Get(i).V())
	}
	return chunks.Meta{
		MinTime: mint,
		MaxTime: maxt,
		Chunk:   c,
	}
}

type sample struct {
	t int64
	v float64
}

func (s sample) T() int64 {
	return s.t
}

func (s sample) V() float64 {
	return s.v
}

// PopulatedChunk creates a chunk populated with samples every second starting at minTime
func PopulatedChunk(numSamples int, minTime int64) chunks.Meta {
	samples := make([]Sample, numSamples)
	for i := 0; i < numSamples; i++ {
		samples[i] = sample{minTime + int64(i*1000), 1.0}
	}
	return ChunkFromSamples(samples)
}

// GenerateSamples starting at start and counting up numSamples.
func GenerateSamples(start, numSamples int) []Sample {
	samples := make([]Sample, 0, numSamples)
	for i := start; i < start+numSamples; i++ {
		samples = append(samples, sample{
			t: int64(i),
			v: float64(i),
		})
	}
	return samples
}