move patch stuff into its own package

pkg/commands/patch/hunk.go

@@ -0,0 +1,142 @@
+package patch
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/utils"
+)
+
+type PatchHunk struct {
+	FirstLineIdx int
+	oldStart     int
+	newStart     int
+	heading      string
+	bodyLines    []string
+}
+
+func (hunk *PatchHunk) LastLineIdx() int {
+	return hunk.FirstLineIdx + len(hunk.bodyLines)
+}
+
+func newHunk(lines []string, firstLineIdx int) *PatchHunk {
+	header := lines[0]
+	bodyLines := lines[1:]
+
+	oldStart, newStart, heading := headerInfo(header)
+
+	return &PatchHunk{
+		oldStart:     oldStart,
+		newStart:     newStart,
+		heading:      heading,
+		FirstLineIdx: firstLineIdx,
+		bodyLines:    bodyLines,
+	}
+}
+
+func headerInfo(header string) (int, int, string) {
+	match := hunkHeaderRegexp.FindStringSubmatch(header)
+
+	oldStart := utils.MustConvertToInt(match[1])
+	newStart := utils.MustConvertToInt(match[2])
+	heading := match[3]
+
+	return oldStart, newStart, heading
+}
+
+func (hunk *PatchHunk) updatedLines(lineIndices []int, reverse bool) []string {
+	skippedNewlineMessageIndex := -1
+	newLines := []string{}
+
+	lineIdx := hunk.FirstLineIdx
+	for _, line := range hunk.bodyLines {
+		lineIdx++ // incrementing at the start to skip the header line
+		if line == "" {
+			break
+		}
+		isLineSelected := utils.IncludesInt(lineIndices, lineIdx)
+
+		firstChar, content := line[:1], line[1:]
+		transformedFirstChar := transformedFirstChar(firstChar, reverse, isLineSelected)
+
+		if isLineSelected || (transformedFirstChar == "\\" && skippedNewlineMessageIndex != lineIdx) || transformedFirstChar == " " {
+			newLines = append(newLines, transformedFirstChar+content)
+			continue
+		}
+
+		if transformedFirstChar == "+" {
+			// we don't want to include the 'newline at end of file' line if it involves an addition we're not including
+			skippedNewlineMessageIndex = lineIdx + 1
+		}
+	}
+
+	return newLines
+}
+
+func transformedFirstChar(firstChar string, reverse bool, isLineSelected bool) string {
+	if reverse {
+		if !isLineSelected && firstChar == "+" {
+			return " "
+		} else if firstChar == "-" {
+			return "+"
+		} else if firstChar == "+" {
+			return "-"
+		} else {
+			return firstChar
+		}
+	}
+
+	if !isLineSelected && firstChar == "-" {
+		return " "
+	}
+
+	return firstChar
+}
+
+func (hunk *PatchHunk) formatHeader(oldStart int, oldLength int, newStart int, newLength int, heading string) string {
+	return fmt.Sprintf("@@ -%d,%d +%d,%d @@%s\n", oldStart, oldLength, newStart, newLength, heading)
+}
+
+func (hunk *PatchHunk) formatWithChanges(lineIndices []int, reverse bool, startOffset int) (int, string) {
+	bodyLines := hunk.updatedLines(lineIndices, reverse)
+	startOffset, header, ok := hunk.updatedHeader(bodyLines, startOffset, reverse)
+	if !ok {
+		return startOffset, ""
+	}
+	return startOffset, header + strings.Join(bodyLines, "")
+}
+
+func (hunk *PatchHunk) updatedHeader(newBodyLines []string, startOffset int, reverse bool) (int, string, bool) {
+	changeCount := nLinesWithPrefix(newBodyLines, []string{"+", "-"})
+	oldLength := nLinesWithPrefix(newBodyLines, []string{" ", "-"})
+	newLength := nLinesWithPrefix(newBodyLines, []string{"+", " "})
+
+	if changeCount == 0 {
+		// if nothing has changed we just return nothing
+		return startOffset, "", false
+	}
+
+	var oldStart int
+	if reverse {
+		oldStart = hunk.newStart
+	} else {
+		oldStart = hunk.oldStart
+	}
+
+	var newStartOffset int
+	// if the hunk went from zero to positive length, we need to increment the starting point by one
+	// if the hunk went from positive to zero length, we need to decrement the starting point by one
+	if oldLength == 0 {
+		newStartOffset = 1
+	} else if newLength == 0 {
+		newStartOffset = -1
+	} else {
+		newStartOffset = 0
+	}
+
+	newStart := oldStart + startOffset + newStartOffset
+
+	newStartOffset = startOffset + newLength - oldLength
+	formattedHeader := hunk.formatHeader(oldStart, oldLength, newStart, newLength, hunk.heading)
+	return newStartOffset, formattedHeader, true
+}