refactor patch code

pkg/commands/patch/parse.go

@@ -0,0 +1,85 @@
+package patch
+
+import (
+	"regexp"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/utils"
+)
+
+var hunkHeaderRegexp = regexp.MustCompile(`(?m)^@@ -(\d+)[^\+]+\+(\d+)[^@]+@@(.*)$`)
+
+func Parse(patchStr string) *Patch {
+	// ignore trailing newline.
+	lines := strings.Split(strings.TrimSuffix(patchStr, "\n"), "\n")
+
+	hunks := []*Hunk{}
+	patchHeader := []string{}
+
+	var currentHunk *Hunk
+	for _, line := range lines {
+		if strings.HasPrefix(line, "@@") {
+			oldStart, newStart, headerContext := headerInfo(line)
+
+			currentHunk = &Hunk{
+				oldStart:      oldStart,
+				newStart:      newStart,
+				headerContext: headerContext,
+				bodyLines:     []*PatchLine{},
+			}
+			hunks = append(hunks, currentHunk)
+		} else if currentHunk != nil {
+			currentHunk.bodyLines = append(currentHunk.bodyLines, newHunkLine(line))
+		} else {
+			patchHeader = append(patchHeader, line)
+		}
+	}
+
+	return &Patch{
+		hunks:  hunks,
+		header: patchHeader,
+	}
+}
+
+func headerInfo(header string) (int, int, string) {
+	match := hunkHeaderRegexp.FindStringSubmatch(header)
+
+	oldStart := utils.MustConvertToInt(match[1])
+	newStart := utils.MustConvertToInt(match[2])
+	headerContext := match[3]
+
+	return oldStart, newStart, headerContext
+}
+
+func newHunkLine(line string) *PatchLine {
+	if line == "" {
+		return &PatchLine{
+			Kind:    CONTEXT,
+			Content: "",
+		}
+	}
+
+	firstChar := line[:1]
+
+	kind := parseFirstChar(firstChar)
+
+	return &PatchLine{
+		Kind:    kind,
+		Content: line,
+	}
+}
+
+func parseFirstChar(firstChar string) PatchLineKind {
+	switch firstChar {
+	case " ":
+		return CONTEXT
+	case "+":
+		return ADDITION
+	case "-":
+		return DELETION
+	case "\\":
+		return NEWLINE_MESSAGE
+	}
+
+	return CONTEXT
+}