cheat/vendor/github.com/sergi/go-diff/diffmatchpatch/patch.go
Christopher Allen Lane 80c91cbdee feat(installer): use go-git to clone
Integrate `go-git` into the application, and use it to `git clone`
cheatsheets when the installer runs.

Previously, the installer required that `git` be installed on the system
`PATH`, so this change has to big advantages:

1. It removes that system dependency on `git`
2. It paves the way for implementing the `--update` command

Additionally, `cheat` now performs a `--depth=1` clone when installing
cheatsheets, which should at least somewhat improve installation times
(especially on slow network connections).
2022-08-27 21:00:46 -04:00

557 lines
17 KiB
Go

// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
// https://github.com/sergi/go-diff
// See the included LICENSE file for license details.
//
// go-diff is a Go implementation of Google's Diff, Match, and Patch library
// Original library is Copyright (c) 2006 Google Inc.
// http://code.google.com/p/google-diff-match-patch/
package diffmatchpatch
import (
"bytes"
"errors"
"math"
"net/url"
"regexp"
"strconv"
"strings"
)
// Patch represents one patch operation.
type Patch struct {
diffs []Diff
Start1 int
Start2 int
Length1 int
Length2 int
}
// String emulates GNU diff's format.
// Header: @@ -382,8 +481,9 @@
// Indices are printed as 1-based, not 0-based.
func (p *Patch) String() string {
var coords1, coords2 string
if p.Length1 == 0 {
coords1 = strconv.Itoa(p.Start1) + ",0"
} else if p.Length1 == 1 {
coords1 = strconv.Itoa(p.Start1 + 1)
} else {
coords1 = strconv.Itoa(p.Start1+1) + "," + strconv.Itoa(p.Length1)
}
if p.Length2 == 0 {
coords2 = strconv.Itoa(p.Start2) + ",0"
} else if p.Length2 == 1 {
coords2 = strconv.Itoa(p.Start2 + 1)
} else {
coords2 = strconv.Itoa(p.Start2+1) + "," + strconv.Itoa(p.Length2)
}
var text bytes.Buffer
_, _ = text.WriteString("@@ -" + coords1 + " +" + coords2 + " @@\n")
// Escape the body of the patch with %xx notation.
for _, aDiff := range p.diffs {
switch aDiff.Type {
case DiffInsert:
_, _ = text.WriteString("+")
case DiffDelete:
_, _ = text.WriteString("-")
case DiffEqual:
_, _ = text.WriteString(" ")
}
_, _ = text.WriteString(strings.Replace(url.QueryEscape(aDiff.Text), "+", " ", -1))
_, _ = text.WriteString("\n")
}
return unescaper.Replace(text.String())
}
// PatchAddContext increases the context until it is unique, but doesn't let the pattern expand beyond MatchMaxBits.
func (dmp *DiffMatchPatch) PatchAddContext(patch Patch, text string) Patch {
if len(text) == 0 {
return patch
}
pattern := text[patch.Start2 : patch.Start2+patch.Length1]
padding := 0
// Look for the first and last matches of pattern in text. If two different matches are found, increase the pattern length.
for strings.Index(text, pattern) != strings.LastIndex(text, pattern) &&
len(pattern) < dmp.MatchMaxBits-2*dmp.PatchMargin {
padding += dmp.PatchMargin
maxStart := max(0, patch.Start2-padding)
minEnd := min(len(text), patch.Start2+patch.Length1+padding)
pattern = text[maxStart:minEnd]
}
// Add one chunk for good luck.
padding += dmp.PatchMargin
// Add the prefix.
prefix := text[max(0, patch.Start2-padding):patch.Start2]
if len(prefix) != 0 {
patch.diffs = append([]Diff{Diff{DiffEqual, prefix}}, patch.diffs...)
}
// Add the suffix.
suffix := text[patch.Start2+patch.Length1 : min(len(text), patch.Start2+patch.Length1+padding)]
if len(suffix) != 0 {
patch.diffs = append(patch.diffs, Diff{DiffEqual, suffix})
}
// Roll back the start points.
patch.Start1 -= len(prefix)
patch.Start2 -= len(prefix)
// Extend the lengths.
patch.Length1 += len(prefix) + len(suffix)
patch.Length2 += len(prefix) + len(suffix)
return patch
}
// PatchMake computes a list of patches.
func (dmp *DiffMatchPatch) PatchMake(opt ...interface{}) []Patch {
if len(opt) == 1 {
diffs, _ := opt[0].([]Diff)
text1 := dmp.DiffText1(diffs)
return dmp.PatchMake(text1, diffs)
} else if len(opt) == 2 {
text1 := opt[0].(string)
switch t := opt[1].(type) {
case string:
diffs := dmp.DiffMain(text1, t, true)
if len(diffs) > 2 {
diffs = dmp.DiffCleanupSemantic(diffs)
diffs = dmp.DiffCleanupEfficiency(diffs)
}
return dmp.PatchMake(text1, diffs)
case []Diff:
return dmp.patchMake2(text1, t)
}
} else if len(opt) == 3 {
return dmp.PatchMake(opt[0], opt[2])
}
return []Patch{}
}
// patchMake2 computes a list of patches to turn text1 into text2.
// text2 is not provided, diffs are the delta between text1 and text2.
func (dmp *DiffMatchPatch) patchMake2(text1 string, diffs []Diff) []Patch {
// Check for null inputs not needed since null can't be passed in C#.
patches := []Patch{}
if len(diffs) == 0 {
return patches // Get rid of the null case.
}
patch := Patch{}
charCount1 := 0 // Number of characters into the text1 string.
charCount2 := 0 // Number of characters into the text2 string.
// Start with text1 (prepatchText) and apply the diffs until we arrive at text2 (postpatchText). We recreate the patches one by one to determine context info.
prepatchText := text1
postpatchText := text1
for i, aDiff := range diffs {
if len(patch.diffs) == 0 && aDiff.Type != DiffEqual {
// A new patch starts here.
patch.Start1 = charCount1
patch.Start2 = charCount2
}
switch aDiff.Type {
case DiffInsert:
patch.diffs = append(patch.diffs, aDiff)
patch.Length2 += len(aDiff.Text)
postpatchText = postpatchText[:charCount2] +
aDiff.Text + postpatchText[charCount2:]
case DiffDelete:
patch.Length1 += len(aDiff.Text)
patch.diffs = append(patch.diffs, aDiff)
postpatchText = postpatchText[:charCount2] + postpatchText[charCount2+len(aDiff.Text):]
case DiffEqual:
if len(aDiff.Text) <= 2*dmp.PatchMargin &&
len(patch.diffs) != 0 && i != len(diffs)-1 {
// Small equality inside a patch.
patch.diffs = append(patch.diffs, aDiff)
patch.Length1 += len(aDiff.Text)
patch.Length2 += len(aDiff.Text)
}
if len(aDiff.Text) >= 2*dmp.PatchMargin {
// Time for a new patch.
if len(patch.diffs) != 0 {
patch = dmp.PatchAddContext(patch, prepatchText)
patches = append(patches, patch)
patch = Patch{}
// Unlike Unidiff, our patch lists have a rolling context. http://code.google.com/p/google-diff-match-patch/wiki/Unidiff Update prepatch text & pos to reflect the application of the just completed patch.
prepatchText = postpatchText
charCount1 = charCount2
}
}
}
// Update the current character count.
if aDiff.Type != DiffInsert {
charCount1 += len(aDiff.Text)
}
if aDiff.Type != DiffDelete {
charCount2 += len(aDiff.Text)
}
}
// Pick up the leftover patch if not empty.
if len(patch.diffs) != 0 {
patch = dmp.PatchAddContext(patch, prepatchText)
patches = append(patches, patch)
}
return patches
}
// PatchDeepCopy returns an array that is identical to a given an array of patches.
func (dmp *DiffMatchPatch) PatchDeepCopy(patches []Patch) []Patch {
patchesCopy := []Patch{}
for _, aPatch := range patches {
patchCopy := Patch{}
for _, aDiff := range aPatch.diffs {
patchCopy.diffs = append(patchCopy.diffs, Diff{
aDiff.Type,
aDiff.Text,
})
}
patchCopy.Start1 = aPatch.Start1
patchCopy.Start2 = aPatch.Start2
patchCopy.Length1 = aPatch.Length1
patchCopy.Length2 = aPatch.Length2
patchesCopy = append(patchesCopy, patchCopy)
}
return patchesCopy
}
// PatchApply merges a set of patches onto the text. Returns a patched text, as well as an array of true/false values indicating which patches were applied.
func (dmp *DiffMatchPatch) PatchApply(patches []Patch, text string) (string, []bool) {
if len(patches) == 0 {
return text, []bool{}
}
// Deep copy the patches so that no changes are made to originals.
patches = dmp.PatchDeepCopy(patches)
nullPadding := dmp.PatchAddPadding(patches)
text = nullPadding + text + nullPadding
patches = dmp.PatchSplitMax(patches)
x := 0
// delta keeps track of the offset between the expected and actual location of the previous patch. If there are patches expected at positions 10 and 20, but the first patch was found at 12, delta is 2 and the second patch has an effective expected position of 22.
delta := 0
results := make([]bool, len(patches))
for _, aPatch := range patches {
expectedLoc := aPatch.Start2 + delta
text1 := dmp.DiffText1(aPatch.diffs)
var startLoc int
endLoc := -1
if len(text1) > dmp.MatchMaxBits {
// PatchSplitMax will only provide an oversized pattern in the case of a monster delete.
startLoc = dmp.MatchMain(text, text1[:dmp.MatchMaxBits], expectedLoc)
if startLoc != -1 {
endLoc = dmp.MatchMain(text,
text1[len(text1)-dmp.MatchMaxBits:], expectedLoc+len(text1)-dmp.MatchMaxBits)
if endLoc == -1 || startLoc >= endLoc {
// Can't find valid trailing context. Drop this patch.
startLoc = -1
}
}
} else {
startLoc = dmp.MatchMain(text, text1, expectedLoc)
}
if startLoc == -1 {
// No match found. :(
results[x] = false
// Subtract the delta for this failed patch from subsequent patches.
delta -= aPatch.Length2 - aPatch.Length1
} else {
// Found a match. :)
results[x] = true
delta = startLoc - expectedLoc
var text2 string
if endLoc == -1 {
text2 = text[startLoc:int(math.Min(float64(startLoc+len(text1)), float64(len(text))))]
} else {
text2 = text[startLoc:int(math.Min(float64(endLoc+dmp.MatchMaxBits), float64(len(text))))]
}
if text1 == text2 {
// Perfect match, just shove the Replacement text in.
text = text[:startLoc] + dmp.DiffText2(aPatch.diffs) + text[startLoc+len(text1):]
} else {
// Imperfect match. Run a diff to get a framework of equivalent indices.
diffs := dmp.DiffMain(text1, text2, false)
if len(text1) > dmp.MatchMaxBits && float64(dmp.DiffLevenshtein(diffs))/float64(len(text1)) > dmp.PatchDeleteThreshold {
// The end points match, but the content is unacceptably bad.
results[x] = false
} else {
diffs = dmp.DiffCleanupSemanticLossless(diffs)
index1 := 0
for _, aDiff := range aPatch.diffs {
if aDiff.Type != DiffEqual {
index2 := dmp.DiffXIndex(diffs, index1)
if aDiff.Type == DiffInsert {
// Insertion
text = text[:startLoc+index2] + aDiff.Text + text[startLoc+index2:]
} else if aDiff.Type == DiffDelete {
// Deletion
startIndex := startLoc + index2
text = text[:startIndex] +
text[startIndex+dmp.DiffXIndex(diffs, index1+len(aDiff.Text))-index2:]
}
}
if aDiff.Type != DiffDelete {
index1 += len(aDiff.Text)
}
}
}
}
}
x++
}
// Strip the padding off.
text = text[len(nullPadding) : len(nullPadding)+(len(text)-2*len(nullPadding))]
return text, results
}
// PatchAddPadding adds some padding on text start and end so that edges can match something.
// Intended to be called only from within patchApply.
func (dmp *DiffMatchPatch) PatchAddPadding(patches []Patch) string {
paddingLength := dmp.PatchMargin
nullPadding := ""
for x := 1; x <= paddingLength; x++ {
nullPadding += string(rune(x))
}
// Bump all the patches forward.
for i := range patches {
patches[i].Start1 += paddingLength
patches[i].Start2 += paddingLength
}
// Add some padding on start of first diff.
if len(patches[0].diffs) == 0 || patches[0].diffs[0].Type != DiffEqual {
// Add nullPadding equality.
patches[0].diffs = append([]Diff{Diff{DiffEqual, nullPadding}}, patches[0].diffs...)
patches[0].Start1 -= paddingLength // Should be 0.
patches[0].Start2 -= paddingLength // Should be 0.
patches[0].Length1 += paddingLength
patches[0].Length2 += paddingLength
} else if paddingLength > len(patches[0].diffs[0].Text) {
// Grow first equality.
extraLength := paddingLength - len(patches[0].diffs[0].Text)
patches[0].diffs[0].Text = nullPadding[len(patches[0].diffs[0].Text):] + patches[0].diffs[0].Text
patches[0].Start1 -= extraLength
patches[0].Start2 -= extraLength
patches[0].Length1 += extraLength
patches[0].Length2 += extraLength
}
// Add some padding on end of last diff.
last := len(patches) - 1
if len(patches[last].diffs) == 0 || patches[last].diffs[len(patches[last].diffs)-1].Type != DiffEqual {
// Add nullPadding equality.
patches[last].diffs = append(patches[last].diffs, Diff{DiffEqual, nullPadding})
patches[last].Length1 += paddingLength
patches[last].Length2 += paddingLength
} else if paddingLength > len(patches[last].diffs[len(patches[last].diffs)-1].Text) {
// Grow last equality.
lastDiff := patches[last].diffs[len(patches[last].diffs)-1]
extraLength := paddingLength - len(lastDiff.Text)
patches[last].diffs[len(patches[last].diffs)-1].Text += nullPadding[:extraLength]
patches[last].Length1 += extraLength
patches[last].Length2 += extraLength
}
return nullPadding
}
// PatchSplitMax looks through the patches and breaks up any which are longer than the maximum limit of the match algorithm.
// Intended to be called only from within patchApply.
func (dmp *DiffMatchPatch) PatchSplitMax(patches []Patch) []Patch {
patchSize := dmp.MatchMaxBits
for x := 0; x < len(patches); x++ {
if patches[x].Length1 <= patchSize {
continue
}
bigpatch := patches[x]
// Remove the big old patch.
patches = append(patches[:x], patches[x+1:]...)
x--
Start1 := bigpatch.Start1
Start2 := bigpatch.Start2
precontext := ""
for len(bigpatch.diffs) != 0 {
// Create one of several smaller patches.
patch := Patch{}
empty := true
patch.Start1 = Start1 - len(precontext)
patch.Start2 = Start2 - len(precontext)
if len(precontext) != 0 {
patch.Length1 = len(precontext)
patch.Length2 = len(precontext)
patch.diffs = append(patch.diffs, Diff{DiffEqual, precontext})
}
for len(bigpatch.diffs) != 0 && patch.Length1 < patchSize-dmp.PatchMargin {
diffType := bigpatch.diffs[0].Type
diffText := bigpatch.diffs[0].Text
if diffType == DiffInsert {
// Insertions are harmless.
patch.Length2 += len(diffText)
Start2 += len(diffText)
patch.diffs = append(patch.diffs, bigpatch.diffs[0])
bigpatch.diffs = bigpatch.diffs[1:]
empty = false
} else if diffType == DiffDelete && len(patch.diffs) == 1 && patch.diffs[0].Type == DiffEqual && len(diffText) > 2*patchSize {
// This is a large deletion. Let it pass in one chunk.
patch.Length1 += len(diffText)
Start1 += len(diffText)
empty = false
patch.diffs = append(patch.diffs, Diff{diffType, diffText})
bigpatch.diffs = bigpatch.diffs[1:]
} else {
// Deletion or equality. Only take as much as we can stomach.
diffText = diffText[:min(len(diffText), patchSize-patch.Length1-dmp.PatchMargin)]
patch.Length1 += len(diffText)
Start1 += len(diffText)
if diffType == DiffEqual {
patch.Length2 += len(diffText)
Start2 += len(diffText)
} else {
empty = false
}
patch.diffs = append(patch.diffs, Diff{diffType, diffText})
if diffText == bigpatch.diffs[0].Text {
bigpatch.diffs = bigpatch.diffs[1:]
} else {
bigpatch.diffs[0].Text =
bigpatch.diffs[0].Text[len(diffText):]
}
}
}
// Compute the head context for the next patch.
precontext = dmp.DiffText2(patch.diffs)
precontext = precontext[max(0, len(precontext)-dmp.PatchMargin):]
postcontext := ""
// Append the end context for this patch.
if len(dmp.DiffText1(bigpatch.diffs)) > dmp.PatchMargin {
postcontext = dmp.DiffText1(bigpatch.diffs)[:dmp.PatchMargin]
} else {
postcontext = dmp.DiffText1(bigpatch.diffs)
}
if len(postcontext) != 0 {
patch.Length1 += len(postcontext)
patch.Length2 += len(postcontext)
if len(patch.diffs) != 0 && patch.diffs[len(patch.diffs)-1].Type == DiffEqual {
patch.diffs[len(patch.diffs)-1].Text += postcontext
} else {
patch.diffs = append(patch.diffs, Diff{DiffEqual, postcontext})
}
}
if !empty {
x++
patches = append(patches[:x], append([]Patch{patch}, patches[x:]...)...)
}
}
}
return patches
}
// PatchToText takes a list of patches and returns a textual representation.
func (dmp *DiffMatchPatch) PatchToText(patches []Patch) string {
var text bytes.Buffer
for _, aPatch := range patches {
_, _ = text.WriteString(aPatch.String())
}
return text.String()
}
// PatchFromText parses a textual representation of patches and returns a List of Patch objects.
func (dmp *DiffMatchPatch) PatchFromText(textline string) ([]Patch, error) {
patches := []Patch{}
if len(textline) == 0 {
return patches, nil
}
text := strings.Split(textline, "\n")
textPointer := 0
patchHeader := regexp.MustCompile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$")
var patch Patch
var sign uint8
var line string
for textPointer < len(text) {
if !patchHeader.MatchString(text[textPointer]) {
return patches, errors.New("Invalid patch string: " + text[textPointer])
}
patch = Patch{}
m := patchHeader.FindStringSubmatch(text[textPointer])
patch.Start1, _ = strconv.Atoi(m[1])
if len(m[2]) == 0 {
patch.Start1--
patch.Length1 = 1
} else if m[2] == "0" {
patch.Length1 = 0
} else {
patch.Start1--
patch.Length1, _ = strconv.Atoi(m[2])
}
patch.Start2, _ = strconv.Atoi(m[3])
if len(m[4]) == 0 {
patch.Start2--
patch.Length2 = 1
} else if m[4] == "0" {
patch.Length2 = 0
} else {
patch.Start2--
patch.Length2, _ = strconv.Atoi(m[4])
}
textPointer++
for textPointer < len(text) {
if len(text[textPointer]) > 0 {
sign = text[textPointer][0]
} else {
textPointer++
continue
}
line = text[textPointer][1:]
line = strings.Replace(line, "+", "%2b", -1)
line, _ = url.QueryUnescape(line)
if sign == '-' {
// Deletion.
patch.diffs = append(patch.diffs, Diff{DiffDelete, line})
} else if sign == '+' {
// Insertion.
patch.diffs = append(patch.diffs, Diff{DiffInsert, line})
} else if sign == ' ' {
// Minor equality.
patch.diffs = append(patch.diffs, Diff{DiffEqual, line})
} else if sign == '@' {
// Start of next patch.
break
} else {
// WTF?
return patches, errors.New("Invalid patch mode '" + string(sign) + "' in: " + string(line))
}
textPointer++
}
patches = append(patches, patch)
}
return patches, nil
}