From b8c233b1bbc0b097d28fbe20233d6d86a41e1a9c Mon Sep 17 00:00:00 2001
From: Boming Zhang <bomingzh@sjtu.edu.cn>
Date: Sat, 16 Nov 2024 03:07:12 -0500
Subject: [PATCH] test(parser/diff): add myers diff test

---
 internal/parser/diff/diff_test.go | 69 +++++++++++++++++++++++++++++++
 internal/parser/diff/parser.go    | 23 ++++++-----
 2 files changed, 82 insertions(+), 10 deletions(-)
 create mode 100644 internal/parser/diff/diff_test.go

diff --git a/internal/parser/diff/diff_test.go b/internal/parser/diff/diff_test.go
new file mode 100644
index 0000000..09ba6fe
--- /dev/null
+++ b/internal/parser/diff/diff_test.go
@@ -0,0 +1,69 @@
+package diff
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestMyersDiff(t *testing.T) {
+	tests := []struct {
+		name         string
+		src          []string
+		dst          []string
+		compareSpace bool
+		expected     []operation
+	}{
+		{
+			name:         "Insert operation",
+			src:          []string{"a", "b"},
+			dst:          []string{"a", "b", "c"},
+			compareSpace: true,
+			expected:     []operation{MOVE, MOVE, INSERT},
+		},
+		{
+			name:         "Delete operation",
+			src:          []string{"a", "b", "c"},
+			dst:          []string{"a", "b"},
+			compareSpace: true,
+			expected:     []operation{MOVE, MOVE, DELETE},
+		},
+		{
+			name:         "No changes",
+			src:          []string{"a", "b", "c"},
+			dst:          []string{"a", "b", "c"},
+			compareSpace: true,
+			expected:     []operation{MOVE, MOVE, MOVE},
+		},
+		{
+			name:         "Move operation",
+			src:          []string{"a", "b", "c"},
+			dst:          []string{"c", "a", "b"},
+			compareSpace: true,
+			expected:     []operation{INSERT, MOVE, MOVE, DELETE},
+		},
+		{
+			name:         "Ignore whitespace differences",
+			src:          []string{"a ", "b"},
+			dst:          []string{"a", "b"},
+			compareSpace: false,
+			expected:     []operation{MOVE, MOVE},
+		},
+		{
+			name:         "Consider whitespace differences",
+			src:          []string{"a ", "b"},
+			dst:          []string{"a", "b"},
+			compareSpace: true,
+			expected:     []operation{DELETE, INSERT, MOVE},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			result := myersDiff(test.src, test.dst, test.compareSpace)
+			if !reflect.DeepEqual(result, test.expected) {
+				t.Errorf("myersDiff(%v, %v, %v) = %v; want %v",
+					test.src, test.dst, test.compareSpace, result, test.expected)
+			}
+		})
+	}
+}
diff --git a/internal/parser/diff/parser.go b/internal/parser/diff/parser.go
index 14230c4..89a5780 100644
--- a/internal/parser/diff/parser.go
+++ b/internal/parser/diff/parser.go
@@ -64,7 +64,7 @@ func (*Diff) Run(results []stage.ExecutorResult, confAny any) (
 				"actual length", len(result.Files[output.FileName]),
 				"answer length", len(string(answer)))
 			// If no difference, assign score
-			if compareChars(string(answer), result.Files[output.FileName],
+			if compareStrings(string(answer), result.Files[output.FileName],
 				output.CompareSpace) {
 				score += output.Score
 				comment += conf.PassComment
@@ -82,7 +82,8 @@ func (*Diff) Run(results []stage.ExecutorResult, confAny any) (
 						result.Files[output.FileName], "\n")
 
 					// Generate Myers diff
-					diffOps := myersDiff(stdoutLines, resultLines)
+					diffOps := myersDiff(stdoutLines, resultLines,
+						output.CompareSpace)
 					if output.MaxDiffLength == 0 { // real default value
 						output.MaxDiffLength = 2048
 					}
@@ -108,13 +109,13 @@ func (*Diff) Run(results []stage.ExecutorResult, confAny any) (
 	return res, forceQuit, nil
 }
 
-// compareChars compares two strings character by character, optionally ignoring whitespace.
-func compareChars(stdout, result string, compareSpace bool) bool {
+// compareStrings compares two strings character by character, optionally ignoring whitespace.
+func compareStrings(str1, str2 string, compareSpace bool) bool {
 	if !compareSpace {
-		stdout = removeSpace(stdout)
-		result = removeSpace(result)
+		str1 = removeSpace(str1)
+		str2 = removeSpace(str2)
 	}
-	return stdout == result
+	return str1 == str2
 }
 
 // removeSpace removes all whitespace characters from the string.
@@ -130,7 +131,7 @@ func removeSpace(s string) string {
 
 // myersDiff computes the Myers' diff between two slices of strings.
 // src: https://github.com/cj1128/myers-diff/blob/master/main.go
-func myersDiff(src, dst []string) []operation {
+func myersDiff(src, dst []string, compareSpace bool) []operation {
 	n := len(src)
 	m := len(dst)
 	max := n + m
@@ -144,7 +145,9 @@ loop:
 
 		if d == 0 {
 			t := 0
-			for len(src) > t && len(dst) > t && src[t] == dst[t] {
+			for len(src) > t &&
+				len(dst) > t &&
+				compareStrings(src[t], dst[t], compareSpace) {
 				t += 1
 			}
 			v[0] = t
@@ -165,7 +168,7 @@ loop:
 
 			y = x - k
 
-			for x < n && y < m && src[x] == dst[y] {
+			for x < n && y < m && compareStrings(src[x], dst[y], compareSpace) {
 				x, y = x+1, y+1
 			}