move patch stuff into its own package

1 files changed, 158 insertions, 0 deletions

diff --git a/pkg/commands/patch/patch_modifier.go b/pkg/commands/patch/patch_modifier.go
new file mode 100644
index 000000000..c2bbc60f6
--- /dev/null
+++ b/pkg/commands/patch/patch_modifier.go
@@ -0,0 +1,158 @@
+package patch
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/sirupsen/logrus"
+)
+
+var hunkHeaderRegexp = regexp.MustCompile(`(?m)^@@ -(\d+)[^\+]+\+(\d+)[^@]+@@(.*)$`)
+var patchHeaderRegexp = regexp.MustCompile(`(?ms)(^diff.*?)^@@`)
+
+func GetHeaderFromDiff(diff string) string {
+	match := patchHeaderRegexp.FindStringSubmatch(diff)
+	if len(match) <= 1 {
+		return ""
+	}
+	return match[1]
+}
+
+func GetHunksFromDiff(diff string) []*PatchHunk {
+	hunks := []*PatchHunk{}
+	firstLineIdx := -1
+	var hunkLines []string
+	pastDiffHeader := false
+
+	for lineIdx, line := range strings.SplitAfter(diff, "\n") {
+		isHunkHeader := strings.HasPrefix(line, "@@ -")
+
+		if isHunkHeader {
+			if pastDiffHeader { // we need to persist the current hunk
+				hunks = append(hunks, newHunk(hunkLines, firstLineIdx))
+			}
+			pastDiffHeader = true
+			firstLineIdx = lineIdx
+			hunkLines = []string{line}
+			continue
+		}
+
+		if !pastDiffHeader { // skip through the stuff that precedes the first hunk
+			continue
+		}
+
+		hunkLines = append(hunkLines, line)
+	}
+
+	if pastDiffHeader {
+		hunks = append(hunks, newHunk(hunkLines, firstLineIdx))
+	}
+
+	return hunks
+}
+
+type PatchModifier struct {
+	Log      *logrus.Entry
+	filename string
+	hunks    []*PatchHunk
+	header   string
+}
+
+func NewPatchModifier(log *logrus.Entry, filename string, diffText string) *PatchModifier {
+	return &PatchModifier{
+		Log:      log,
+		filename: filename,
+		hunks:    GetHunksFromDiff(diffText),
+		header:   GetHeaderFromDiff(diffText),
+	}
+}
+
+func (d *PatchModifier) ModifiedPatchForLines(lineIndices []int, reverse bool, keepOriginalHeader bool) string {
+	// step one is getting only those hunks which we care about
+	hunksInRange := []*PatchHunk{}
+outer:
+	for _, hunk := range d.hunks {
+		// if there is any line in our lineIndices array that the hunk contains, we append it
+		for _, lineIdx := range lineIndices {
+			if lineIdx >= hunk.FirstLineIdx && lineIdx <= hunk.LastLineIdx() {
+				hunksInRange = append(hunksInRange, hunk)
+				continue outer
+			}
+		}
+	}
+
+	// step 2 is collecting all the hunks with new headers
+	startOffset := 0
+	formattedHunks := ""
+	var formattedHunk string
+	for _, hunk := range hunksInRange {
+		startOffset, formattedHunk = hunk.formatWithChanges(lineIndices, reverse, startOffset)
+		formattedHunks += formattedHunk
+	}
+
+	if formattedHunks == "" {
+		return ""
+	}
+
+	var fileHeader string
+	// for staging/unstaging lines we don't want the original header because
+	// it makes git confused e.g. when dealing with deleted/added files
+	// but with building and applying patches the original header gives git
+	// information it needs to cleanly apply patches
+	if keepOriginalHeader {
+		fileHeader = d.header
+	} else {
+		fileHeader = fmt.Sprintf("--- a/%s\n+++ b/%s\n", d.filename, d.filename)
+	}
+
+	return fileHeader + formattedHunks
+}
+
+func (d *PatchModifier) ModifiedPatchForRange(firstLineIdx int, lastLineIdx int, reverse bool, keepOriginalHeader bool) string {
+	// generate array of consecutive line indices from our range
+	selectedLines := []int{}
+	for i := firstLineIdx; i <= lastLineIdx; i++ {
+		selectedLines = append(selectedLines, i)
+	}
+	return d.ModifiedPatchForLines(selectedLines, reverse, keepOriginalHeader)
+}
+
+func (d *PatchModifier) OriginalPatchLength() int {
+	if len(d.hunks) == 0 {
+		return 0
+	}
+
+	return d.hunks[len(d.hunks)-1].LastLineIdx()
+}
+
+func ModifiedPatchForRange(log *logrus.Entry, filename string, diffText string, firstLineIdx int, lastLineIdx int, reverse bool, keepOriginalHeader bool) string {
+	p := NewPatchModifier(log, filename, diffText)
+	return p.ModifiedPatchForRange(firstLineIdx, lastLineIdx, reverse, keepOriginalHeader)
+}
+
+func ModifiedPatchForLines(log *logrus.Entry, filename string, diffText string, includedLineIndices []int, reverse bool, keepOriginalHeader bool) string {
+	p := NewPatchModifier(log, filename, diffText)
+	return p.ModifiedPatchForLines(includedLineIndices, reverse, keepOriginalHeader)
+}
+
+// I want to know, given a hunk, what line a given index is on
+func (hunk *PatchHunk) LineNumberOfLine(idx int) int {
+	lines := hunk.bodyLines[0 : idx-hunk.FirstLineIdx-1]
+
+	offset := nLinesWithPrefix(lines, []string{"+", " "})
+
+	return hunk.newStart + offset
+}
+
+func nLinesWithPrefix(lines []string, chars []string) int {
+	result := 0
+	for _, line := range lines {
+		for _, char := range chars {
+			if line[:1] == char {
+				result++
+			}
+		}
+	}
+	return result
+}