hercules/burndown.go

package hercules

import (
	"errors"
	"fmt"
	"io"
	"os"
	"sort"
	"unicode/utf8"

	"github.com/gogo/protobuf/proto"
	"github.com/sergi/go-diff/diffmatchpatch"
	"gopkg.in/src-d/go-git.v4"
	"gopkg.in/src-d/go-git.v4/plumbing"
	"gopkg.in/src-d/go-git.v4/plumbing/object"
	"gopkg.in/src-d/go-git.v4/utils/merkletrie"
	"gopkg.in/src-d/hercules.v3/pb"
	"gopkg.in/src-d/hercules.v3/yaml"
)

// BurndownAnalyser allows to gather the line burndown statistics for a Git repository.
type BurndownAnalysis struct {
	// Granularity sets the size of each band - the number of days it spans.
	// Smaller values provide better resolution but require more work and eat more
	// memory. 30 days is usually enough.
	Granularity int
	// Sampling sets how detailed is the statistic - the size of the interval in
	// days between consecutive measurements. It is usually a good idea to set it
	// <= Granularity. Try 15 or 30.
	Sampling int

	// TrackFiles enables or disables the fine-grained per-file burndown analysis.
	// It does not change the top level burndown results.
	TrackFiles bool

	// The number of developers for which to collect the burndown stats. 0 disables it.
	PeopleNumber int

	// Debug activates the debugging mode. Analyse() runs slower in this mode
	// but it accurately checks all the intermediate states for invariant
	// violations.
	Debug bool

	// Repository points to the analysed Git repository struct from go-git.
	repository *git.Repository
	// globalStatus is the current daily alive number of lines; key is the number
	// of days from the beginning of the history.
	globalStatus map[int]int64
	// globalHistory is the weekly snapshots of globalStatus.
	globalHistory [][]int64
	// fileHistories is the weekly snapshots of each file's status.
	fileHistories map[string][][]int64
	// peopleHistories is the weekly snapshots of each person's status.
	peopleHistories [][][]int64
	// files is the mapping <file path> -> *File.
	files map[string]*File
	// matrix is the mutual deletions and self insertions.
	matrix []map[int]int64
	// people is the people's individual time stats.
	people []map[int]int64
	// day is the most recent day index processed.
	day int
	// previousDay is the day from the previous sample period -
	// different from DaysSinceStart.previousDay.
	previousDay int
	// references IdentityDetector.ReversedPeopleDict
	reversedPeopleDict []string
}

type BurndownResult struct {
	GlobalHistory      [][]int64
	FileHistories      map[string][][]int64
	PeopleHistories    [][][]int64
	PeopleMatrix       [][]int64
	reversedPeopleDict []string
	sampling           int
	granularity        int
}

const (
	ConfigBurndownGranularity = "Burndown.Granularity"
	ConfigBurndownSampling    = "Burndown.Sampling"
	ConfigBurndownTrackFiles  = "Burndown.TrackFiles"
	ConfigBurndownTrackPeople = "Burndown.TrackPeople"
	ConfigBurndownDebug       = "Burndown.Debug"
)

func (analyser *BurndownAnalysis) Name() string {
	return "Burndown"
}

func (analyser *BurndownAnalysis) Provides() []string {
	return []string{}
}

func (analyser *BurndownAnalysis) Requires() []string {
	arr := [...]string{"file_diff", "changes", "blob_cache", "day", "author"}
	return arr[:]
}

func (analyser *BurndownAnalysis) ListConfigurationOptions() []ConfigurationOption {
	options := [...]ConfigurationOption{{
		Name:        ConfigBurndownGranularity,
		Description: "How many days there are in a single band.",
		Flag:        "granularity",
		Type:        IntConfigurationOption,
		Default:     30}, {
		Name:        ConfigBurndownSampling,
		Description: "How frequently to record the state in days.",
		Flag:        "sampling",
		Type:        IntConfigurationOption,
		Default:     30}, {
		Name:        ConfigBurndownTrackFiles,
		Description: "Record detailed statistics per each file.",
		Flag:        "burndown-files",
		Type:        BoolConfigurationOption,
		Default:     false}, {
		Name:        ConfigBurndownTrackPeople,
		Description: "Record detailed statistics per each developer.",
		Flag:        "burndown-people",
		Type:        BoolConfigurationOption,
		Default:     false}, {
		Name:        ConfigBurndownDebug,
		Description: "Validate the trees on each step.",
		Flag:        "burndown-debug",
		Type:        BoolConfigurationOption,
		Default:     false},
	}
	return options[:]
}

func (analyser *BurndownAnalysis) Configure(facts map[string]interface{}) {
	if val, exists := facts[ConfigBurndownGranularity].(int); exists {
		analyser.Granularity = val
	}
	if val, exists := facts[ConfigBurndownSampling].(int); exists {
		analyser.Sampling = val
	}
	if val, exists := facts[ConfigBurndownTrackFiles].(bool); exists {
		analyser.TrackFiles = val
	}
	if people, exists := facts[ConfigBurndownTrackPeople].(bool); people {
		if val, exists := facts[FactIdentityDetectorPeopleCount].(int); exists {
			analyser.PeopleNumber = val
			analyser.reversedPeopleDict = facts[FactIdentityDetectorReversedPeopleDict].([]string)
		}
	} else if exists {
		analyser.PeopleNumber = 0
	}
	if val, exists := facts[ConfigBurndownDebug].(bool); exists {
		analyser.Debug = val
	}
}

func (analyser *BurndownAnalysis) Flag() string {
	return "burndown"
}

func (analyser *BurndownAnalysis) Initialize(repository *git.Repository) {
	if analyser.Granularity <= 0 {
		fmt.Fprintln(os.Stderr, "Warning: adjusted the granularity to 30 days")
		analyser.Granularity = 30
	}
	if analyser.Sampling <= 0 {
		fmt.Fprintln(os.Stderr, "Warning: adjusted the sampling to 30 days")
		analyser.Sampling = 30
	}
	analyser.repository = repository
	analyser.globalStatus = map[int]int64{}
	analyser.globalHistory = [][]int64{}
	analyser.fileHistories = map[string][][]int64{}
	analyser.peopleHistories = make([][][]int64, analyser.PeopleNumber)
	analyser.files = map[string]*File{}
	analyser.matrix = make([]map[int]int64, analyser.PeopleNumber)
	analyser.people = make([]map[int]int64, analyser.PeopleNumber)
	analyser.day = 0
	analyser.previousDay = 0
}

func (analyser *BurndownAnalysis) Consume(deps map[string]interface{}) (map[string]interface{}, error) {
	sampling := analyser.Sampling
	if sampling == 0 {
		sampling = 1
	}
	author := deps["author"].(int)
	analyser.day = deps["day"].(int)
	delta := (analyser.day / sampling) - (analyser.previousDay / sampling)
	if delta > 0 {
		analyser.previousDay = analyser.day
		gs, fss, pss := analyser.groupStatus()
		analyser.updateHistories(gs, fss, pss, delta)
	}
	cache := deps["blob_cache"].(map[plumbing.Hash]*object.Blob)
	treeDiffs := deps["changes"].(object.Changes)
	fileDiffs := deps["file_diff"].(map[string]FileDiffData)
	for _, change := range treeDiffs {
		action, err := change.Action()
		if err != nil {
			return nil, err
		}
		switch action {
		case merkletrie.Insert:
			err = analyser.handleInsertion(change, author, cache)
		case merkletrie.Delete:
			err = analyser.handleDeletion(change, author, cache)
		case merkletrie.Modify:
			err = analyser.handleModification(change, author, cache, fileDiffs)
		}
		if err != nil {
			return nil, err
		}
	}
	return nil, nil
}

// Finalize() returns the list of snapshots of the cumulative line edit times
// and the similar lists for every file which is alive in HEAD.
// The number of snapshots (the first dimension >[]<[]int64) depends on
// Analyser.Sampling (the more Sampling, the less the value); the length of
// each snapshot depends on Analyser.Granularity (the more Granularity,
// the less the value).
func (analyser *BurndownAnalysis) Finalize() interface{} {
	gs, fss, pss := analyser.groupStatus()
	analyser.updateHistories(gs, fss, pss, 1)
	for key, statuses := range analyser.fileHistories {
		if len(statuses) == len(analyser.globalHistory) {
			continue
		}
		padding := make([][]int64, len(analyser.globalHistory)-len(statuses))
		for i := range padding {
			padding[i] = make([]int64, len(analyser.globalStatus))
		}
		analyser.fileHistories[key] = append(padding, statuses...)
	}
	peopleMatrix := make([][]int64, analyser.PeopleNumber)
	for i, row := range analyser.matrix {
		mrow := make([]int64, analyser.PeopleNumber+2)
		peopleMatrix[i] = mrow
		for key, val := range row {
			if key == MISSING_AUTHOR {
				key = -1
			} else if key == SELF_AUTHOR {
				key = -2
			}
			mrow[key+2] = val
		}
	}
	return BurndownResult{
		GlobalHistory:      analyser.globalHistory,
		FileHistories:      analyser.fileHistories,
		PeopleHistories:    analyser.peopleHistories,
		PeopleMatrix:       peopleMatrix,
		reversedPeopleDict: analyser.reversedPeopleDict,
	}
}

func (analyser *BurndownAnalysis) Serialize(result interface{}, binary bool, writer io.Writer) error {
	burndownResult := result.(BurndownResult)
	if binary {
		return analyser.serializeBinary(&burndownResult, writer)
	}
	analyser.serializeText(&burndownResult, writer)
	return nil
}

func (analyser *BurndownAnalysis) Deserialize(pbmessage []byte) (interface{}, error) {
	msg := pb.BurndownAnalysisResults{}
	err := proto.Unmarshal(pbmessage, &msg)
	if err != nil {
		return nil, err
	}
	result := BurndownResult{}
	convertCSR := func(mat *pb.BurndownSparseMatrix) [][]int64 {
		res := make([][]int64, mat.NumberOfRows)
		for i := 0; i < int(mat.NumberOfRows); i++ {
			res[i] = make([]int64, mat.NumberOfColumns)
			for j := 0; j < int(mat.NumberOfColumns); j++ {
				res[i][j] = int64(mat.Rows[i].Columns[j])
			}
		}
		return res
	}
	result.GlobalHistory = convertCSR(msg.Project)
	result.FileHistories = map[string][][]int64{}
	for _, mat := range msg.Files {
		result.FileHistories[mat.Name] = convertCSR(mat)
	}
	result.reversedPeopleDict = make([]string, len(msg.People))
	result.PeopleHistories = make([][][]int64, len(msg.People))
	for i, mat := range msg.People {
		result.PeopleHistories[i] = convertCSR(mat)
		result.reversedPeopleDict[i] = mat.Name
	}
	result.PeopleMatrix = make([][]int64, msg.PeopleInteraction.NumberOfRows)
	for i := 0; i < len(result.PeopleMatrix); i++ {
		result.PeopleMatrix[i] = make([]int64, msg.PeopleInteraction.NumberOfColumns)
		for j := int(msg.PeopleInteraction.Indptr[i]); j < int(msg.PeopleInteraction.Indptr[i+1]); j++ {
			result.PeopleMatrix[i][msg.PeopleInteraction.Indices[j]] = msg.PeopleInteraction.Data[j]
		}
	}
	result.sampling = int(msg.Sampling)
	result.granularity = int(msg.Granularity)
	return result, nil
}

func (analyser *BurndownAnalysis) MergeResults(
	r1, r2 interface{}, c1, c2 *CommonAnalysisResult) interface{} {
	bar1 := r1.(BurndownResult)
	bar2 := r2.(BurndownResult)
	merged := BurndownResult{}
	if bar1.sampling < bar2.sampling {
		merged.sampling = bar1.sampling
	} else {
		merged.sampling = bar2.sampling
	}
	if bar1.granularity < bar2.granularity {
		merged.granularity = bar1.granularity
	} else {
		merged.granularity = bar2.granularity
	}
	people := map[string]int{}
	for _, id := range bar1.reversedPeopleDict {
		people[id] = len(people)
	}
	for _, id := range bar2.reversedPeopleDict {
		if _, exists := people[id]; !exists {
			people[id] = len(people)
		}
	}
	merged.reversedPeopleDict = make([]string, len(people))
	for name, index := range people {
		merged.reversedPeopleDict[index] = name
	}

	// interpolate to daily and sum
	_ = bar1
	_ = bar2
	panic("not implemented")
	// return merged
}

func mergeMatrices(m1, m2 [][]int64, granularity1, sampling1, granularity2, sampling2 int,
	c1, c2 *CommonAnalysisResult) {
	commonMerged := CommonAnalysisResult{}
	commonMerged.Merge(c1)
	commonMerged.Merge(c2)
	size := (commonMerged.EndTime - commonMerged.BeginTime) / (3600 * 24)
	daily := make([][]float32, size)
	for i := range daily {
		daily[i] = make([]float32, size)
	}
	addMatrix(m1, granularity1, sampling1, daily,
		int(c1.BeginTime-commonMerged.BeginTime)/(3600*24))
	addMatrix(m2, granularity2, sampling2, daily,
		int(c2.BeginTime-commonMerged.BeginTime)/(3600*24))
	// convert daily to [][]int64
}

func addMatrix(matrix [][]int64, granularity, sampling int, daily [][]float32, offset int) {
	/*
	 daily_matrix = numpy.zeros(
	            (matrix.shape[0] * granularity, matrix.shape[1] * sampling),
	            dtype=numpy.float32)
	*/
	// Determine the maximum number of bands; the actual one may be larger but we do not care
	maxCols := 0
	for _, row := range matrix {
		if maxCols < len(row) {
			maxCols = len(row)
		}
	}
	// Ported from labours.py load_burndown()
	for y := 0; y < maxCols; y++ {
		for x := 0; x < len(matrix); x++ {
			if (y+1)*granularity <= x*sampling {
				// interpolate
				var previous int64
				if x > 0 && y < len(matrix[x-1]) {
					previous = matrix[x-1][y]
				}
				for i := 0; i < sampling; i++ {
					var value float32
					if y < len(matrix[x]) {
						value = (float32(previous) +
							float32((matrix[x][y]-previous)*int64(i))/float32(sampling)) / float32(granularity)
					} else {
						value = float32(previous) *
							(float32(1) - float32(i)/float32(sampling)) / float32(granularity)
					}
					for j := y * granularity; j < (y+1)*granularity; j++ {
						daily[j+offset][x*sampling+i+offset] += value
					}
				}
			} else if y*granularity <= (x+1)*sampling && y < len(matrix[x]) {
				// fill constant
				for suby := y*granularity + offset; suby < (y+1)*granularity+offset; suby++ {
					for subx := suby; subx < (x+1)*sampling+offset; subx++ {
						daily[suby][subx] += float32(matrix[x][y]) / float32(granularity)
					}
				}
			}
		}
	}
}

func (analyser *BurndownAnalysis) serializeText(result *BurndownResult, writer io.Writer) {
	fmt.Fprintln(writer, "  granularity:", analyser.Granularity)
	fmt.Fprintln(writer, "  sampling:", analyser.Sampling)
	yaml.PrintMatrix(writer, result.GlobalHistory, 2, "project", true)
	if len(result.FileHistories) > 0 {
		fmt.Fprintln(writer, "  files:")
		keys := sortedKeys(result.FileHistories)
		for _, key := range keys {
			yaml.PrintMatrix(writer, result.FileHistories[key], 4, key, true)
		}
	}

	if len(result.PeopleHistories) > 0 {
		fmt.Fprintln(writer, "  people_sequence:")
		for key := range result.PeopleHistories {
			fmt.Fprintln(writer, "    - "+yaml.SafeString(result.reversedPeopleDict[key]))
		}
		fmt.Fprintln(writer, "  people:")
		for key, val := range result.PeopleHistories {
			yaml.PrintMatrix(writer, val, 4, result.reversedPeopleDict[key], true)
		}
		fmt.Fprintln(writer, "  people_interaction: |-")
		yaml.PrintMatrix(writer, result.PeopleMatrix, 4, "", false)
	}
}

func (analyser *BurndownAnalysis) serializeBinary(result *BurndownResult, writer io.Writer) error {
	message := pb.BurndownAnalysisResults{
		Granularity: int32(analyser.Granularity),
		Sampling:    int32(analyser.Sampling),
		Project:     pb.ToBurndownSparseMatrix(result.GlobalHistory, "project"),
	}
	if len(result.FileHistories) > 0 {
		message.Files = make([]*pb.BurndownSparseMatrix, len(result.FileHistories))
		keys := sortedKeys(result.FileHistories)
		i := 0
		for _, key := range keys {
			message.Files[i] = pb.ToBurndownSparseMatrix(
				result.FileHistories[key], key)
			i++
		}
	}

	if len(result.PeopleHistories) > 0 {
		message.People = make(
			[]*pb.BurndownSparseMatrix, len(result.PeopleHistories))
		for key, val := range result.PeopleHistories {
			message.People[key] = pb.ToBurndownSparseMatrix(val, result.reversedPeopleDict[key])
		}
		message.PeopleInteraction = pb.DenseToCompressedSparseRowMatrix(result.PeopleMatrix)
	}
	serialized, err := proto.Marshal(&message)
	if err != nil {
		return err
	}
	writer.Write(serialized)
	return nil
}

func sortedKeys(m map[string][][]int64) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}

func checkClose(c io.Closer) {
	if err := c.Close(); err != nil {
		panic(err)
	}
}

func (analyser *BurndownAnalysis) packPersonWithDay(person int, day int) int {
	if analyser.PeopleNumber == 0 {
		return day
	}
	result := day
	result |= person << 14
	// This effectively means max 16384 days (>44 years) and (131072 - 2) devs
	return result
}

func (analyser *BurndownAnalysis) unpackPersonWithDay(value int) (int, int) {
	if analyser.PeopleNumber == 0 {
		return MISSING_AUTHOR, value
	}
	return value >> 14, value & 0x3FFF
}

func (analyser *BurndownAnalysis) updateStatus(
	status interface{}, _ int, previous_time_ int, delta int) {

	_, previous_time := analyser.unpackPersonWithDay(previous_time_)
	status.(map[int]int64)[previous_time] += int64(delta)
}

func (analyser *BurndownAnalysis) updatePeople(people interface{}, _ int, previous_time_ int, delta int) {
	old_author, previous_time := analyser.unpackPersonWithDay(previous_time_)
	if old_author == MISSING_AUTHOR {
		return
	}
	casted := people.([]map[int]int64)
	stats := casted[old_author]
	if stats == nil {
		stats = map[int]int64{}
		casted[old_author] = stats
	}
	stats[previous_time] += int64(delta)
}

func (analyser *BurndownAnalysis) updateMatrix(
	matrix_ interface{}, current_time int, previous_time int, delta int) {

	matrix := matrix_.([]map[int]int64)
	new_author, _ := analyser.unpackPersonWithDay(current_time)
	old_author, _ := analyser.unpackPersonWithDay(previous_time)
	if old_author == MISSING_AUTHOR {
		return
	}
	if new_author == old_author && delta > 0 {
		new_author = SELF_AUTHOR
	}
	row := matrix[old_author]
	if row == nil {
		row = map[int]int64{}
		matrix[old_author] = row
	}
	cell, exists := row[new_author]
	if !exists {
		row[new_author] = 0
		cell = 0
	}
	row[new_author] = cell + int64(delta)
}

func (analyser *BurndownAnalysis) newFile(
	author int, day int, size int, global map[int]int64, people []map[int]int64,
	matrix []map[int]int64) *File {
	statuses := make([]Status, 1)
	statuses[0] = NewStatus(global, analyser.updateStatus)
	if analyser.TrackFiles {
		statuses = append(statuses, NewStatus(map[int]int64{}, analyser.updateStatus))
	}
	if analyser.PeopleNumber > 0 {
		statuses = append(statuses, NewStatus(people, analyser.updatePeople))
		statuses = append(statuses, NewStatus(matrix, analyser.updateMatrix))
		day = analyser.packPersonWithDay(author, day)
	}
	return NewFile(day, size, statuses...)
}

func (analyser *BurndownAnalysis) handleInsertion(
	change *object.Change, author int, cache map[plumbing.Hash]*object.Blob) error {
	blob := cache[change.To.TreeEntry.Hash]
	lines, err := CountLines(blob)
	if err != nil {
		if err.Error() == "binary" {
			return nil
		}
		return err
	}
	name := change.To.Name
	file, exists := analyser.files[name]
	if exists {
		return errors.New(fmt.Sprintf("file %s already exists", name))
	}
	file = analyser.newFile(
		author, analyser.day, lines, analyser.globalStatus, analyser.people, analyser.matrix)
	analyser.files[name] = file
	return nil
}

func (analyser *BurndownAnalysis) handleDeletion(
	change *object.Change, author int, cache map[plumbing.Hash]*object.Blob) error {

	blob := cache[change.From.TreeEntry.Hash]
	lines, err := CountLines(blob)
	if err != nil {
		if err.Error() == "binary" {
			return nil
		}
		return err
	}
	name := change.From.Name
	file := analyser.files[name]
	file.Update(analyser.packPersonWithDay(author, analyser.day), 0, 0, lines)
	delete(analyser.files, name)
	return nil
}

func (analyser *BurndownAnalysis) handleModification(
	change *object.Change, author int, cache map[plumbing.Hash]*object.Blob,
	diffs map[string]FileDiffData) error {

	file, exists := analyser.files[change.From.Name]
	if !exists {
		// this indeed may happen
		return analyser.handleInsertion(change, author, cache)
	}

	// possible rename
	if change.To.Name != change.From.Name {
		err := analyser.handleRename(change.From.Name, change.To.Name)
		if err != nil {
			return err
		}
	}

	thisDiffs := diffs[change.To.Name]
	if file.Len() != thisDiffs.OldLinesOfCode {
		fmt.Fprintf(os.Stderr, "====TREE====\n%s", file.Dump())
		return errors.New(fmt.Sprintf("%s: internal integrity error src %d != %d %s -> %s",
			change.To.Name, thisDiffs.OldLinesOfCode, file.Len(),
			change.From.TreeEntry.Hash.String(), change.To.TreeEntry.Hash.String()))
	}

	// we do not call RunesToDiffLines so the number of lines equals
	// to the rune count
	position := 0
	pending := diffmatchpatch.Diff{Text: ""}

	apply := func(edit diffmatchpatch.Diff) {
		length := utf8.RuneCountInString(edit.Text)
		if edit.Type == diffmatchpatch.DiffInsert {
			file.Update(analyser.packPersonWithDay(author, analyser.day), position, length, 0)
			position += length
		} else {
			file.Update(analyser.packPersonWithDay(author, analyser.day), position, 0, length)
		}
		if analyser.Debug {
			file.Validate()
		}
	}

	for _, edit := range thisDiffs.Diffs {
		dump_before := ""
		if analyser.Debug {
			dump_before = file.Dump()
		}
		length := utf8.RuneCountInString(edit.Text)
		debug_error := func() {
			fmt.Fprintf(os.Stderr, "%s: internal diff error\n", change.To.Name)
			fmt.Fprintf(os.Stderr, "Update(%d, %d, %d (0), %d (0))\n", analyser.day, position,
				length, utf8.RuneCountInString(pending.Text))
			if dump_before != "" {
				fmt.Fprintf(os.Stderr, "====TREE BEFORE====\n%s====END====\n", dump_before)
			}
			fmt.Fprintf(os.Stderr, "====TREE AFTER====\n%s====END====\n", file.Dump())
		}
		switch edit.Type {
		case diffmatchpatch.DiffEqual:
			if pending.Text != "" {
				apply(pending)
				pending.Text = ""
			}
			position += length
		case diffmatchpatch.DiffInsert:
			if pending.Text != "" {
				if pending.Type == diffmatchpatch.DiffInsert {
					debug_error()
					return errors.New("DiffInsert may not appear after DiffInsert")
				}
				file.Update(analyser.packPersonWithDay(author, analyser.day), position, length,
					utf8.RuneCountInString(pending.Text))
				if analyser.Debug {
					file.Validate()
				}
				position += length
				pending.Text = ""
			} else {
				pending = edit
			}
		case diffmatchpatch.DiffDelete:
			if pending.Text != "" {
				debug_error()
				return errors.New("DiffDelete may not appear after DiffInsert/DiffDelete")
			}
			pending = edit
		default:
			debug_error()
			return errors.New(fmt.Sprintf("diff operation is not supported: %d", edit.Type))
		}
	}
	if pending.Text != "" {
		apply(pending)
		pending.Text = ""
	}
	if file.Len() != thisDiffs.NewLinesOfCode {
		return errors.New(fmt.Sprintf("%s: internal integrity error dst %d != %d",
			change.To.Name, thisDiffs.NewLinesOfCode, file.Len()))
	}
	return nil
}

func (analyser *BurndownAnalysis) handleRename(from, to string) error {
	file, exists := analyser.files[from]
	if !exists {
		return errors.New(fmt.Sprintf("file %s does not exist", from))
	}
	analyser.files[to] = file
	delete(analyser.files, from)
	return nil
}

func (analyser *BurndownAnalysis) groupStatus() ([]int64, map[string][]int64, [][]int64) {
	granularity := analyser.Granularity
	if granularity == 0 {
		granularity = 1
	}
	day := analyser.day
	day++
	adjust := 0
	if day%granularity != 0 {
		adjust = 1
	}
	global := make([]int64, day/granularity+adjust)
	var group int64
	for i := 0; i < day; i++ {
		group += analyser.globalStatus[i]
		if (i % granularity) == (granularity - 1) {
			global[i/granularity] = group
			group = 0
		}
	}
	if day%granularity != 0 {
		global[len(global)-1] = group
	}
	locals := make(map[string][]int64)
	if analyser.TrackFiles {
		for key, file := range analyser.files {
			status := make([]int64, day/granularity+adjust)
			var group int64
			for i := 0; i < day; i++ {
				group += file.Status(1).(map[int]int64)[i]
				if (i % granularity) == (granularity - 1) {
					status[i/granularity] = group
					group = 0
				}
			}
			if day%granularity != 0 {
				status[len(status)-1] = group
			}
			locals[key] = status
		}
	}
	peoples := make([][]int64, len(analyser.people))
	for key, person := range analyser.people {
		status := make([]int64, day/granularity+adjust)
		var group int64
		for i := 0; i < day; i++ {
			group += person[i]
			if (i % granularity) == (granularity - 1) {
				status[i/granularity] = group
				group = 0
			}
		}
		if day%granularity != 0 {
			status[len(status)-1] = group
		}
		peoples[key] = status
	}
	return global, locals, peoples
}

func (analyser *BurndownAnalysis) updateHistories(
	globalStatus []int64, file_statuses map[string][]int64, people_statuses [][]int64, delta int) {
	for i := 0; i < delta; i++ {
		analyser.globalHistory = append(analyser.globalHistory, globalStatus)
	}
	to_delete := make([]string, 0)
	for key, fh := range analyser.fileHistories {
		ls, exists := file_statuses[key]
		if !exists {
			to_delete = append(to_delete, key)
		} else {
			for i := 0; i < delta; i++ {
				fh = append(fh, ls)
			}
			analyser.fileHistories[key] = fh
		}
	}
	for _, key := range to_delete {
		delete(analyser.fileHistories, key)
	}
	for key, ls := range file_statuses {
		fh, exists := analyser.fileHistories[key]
		if exists {
			continue
		}
		for i := 0; i < delta; i++ {
			fh = append(fh, ls)
		}
		analyser.fileHistories[key] = fh
	}

	for key, ph := range analyser.peopleHistories {
		ls := people_statuses[key]
		for i := 0; i < delta; i++ {
			ph = append(ph, ls)
		}
		analyser.peopleHistories[key] = ph
	}
}

func init() {
	Registry.Register(&BurndownAnalysis{})
}