Initial commit to new repository

src/AxCopilot/Services/DiffService.cs

@@ -0,0 +1,99 @@
+namespace AxCopilot.Services;
+
+/// <summary>
+/// 라인 기반 텍스트 diff 서비스. 두 텍스트의 변경 사항을 비교합니다.
+/// </summary>
+public static class DiffService
+{
+    public enum DiffType { Equal, Added, Removed }
+
+    public record DiffLine(DiffType Type, int? OldLineNo, int? NewLineNo, string Content);
+
+    /// <summary>두 텍스트를 라인 단위로 비교하여 diff 결과를 반환합니다.</summary>
+    public static List<DiffLine> ComputeDiff(string oldText, string newText)
+    {
+        var oldLines = (oldText ?? "").Split('\n');
+        var newLines = (newText ?? "").Split('\n');
+        var result = new List<DiffLine>();
+
+        // LCS (Longest Common Subsequence) 기반 간단 diff
+        var lcs = ComputeLcs(oldLines, newLines);
+        int oi = 0, ni = 0, li = 0;
+
+        while (oi < oldLines.Length || ni < newLines.Length)
+        {
+            if (li < lcs.Count && oi < oldLines.Length && ni < newLines.Length &&
+                oldLines[oi].TrimEnd('\r') == lcs[li] && newLines[ni].TrimEnd('\r') == lcs[li])
+            {
+                result.Add(new DiffLine(DiffType.Equal, oi + 1, ni + 1, oldLines[oi].TrimEnd('\r')));
+                oi++; ni++; li++;
+            }
+            else if (li < lcs.Count && oi < oldLines.Length &&
+                     oldLines[oi].TrimEnd('\r') != lcs[li])
+            {
+                result.Add(new DiffLine(DiffType.Removed, oi + 1, null, oldLines[oi].TrimEnd('\r')));
+                oi++;
+            }
+            else if (ni < newLines.Length &&
+                     (li >= lcs.Count || newLines[ni].TrimEnd('\r') != lcs[li]))
+            {
+                result.Add(new DiffLine(DiffType.Added, null, ni + 1, newLines[ni].TrimEnd('\r')));
+                ni++;
+            }
+            else
+            {
+                // 나머지 처리
+                if (oi < oldLines.Length)
+                {
+                    result.Add(new DiffLine(DiffType.Removed, oi + 1, null, oldLines[oi].TrimEnd('\r')));
+                    oi++;
+                }
+                if (ni < newLines.Length)
+                {
+                    result.Add(new DiffLine(DiffType.Added, null, ni + 1, newLines[ni].TrimEnd('\r')));
+                    ni++;
+                }
+            }
+        }
+
+        return result;
+    }
+
+    private static List<string> ComputeLcs(string[] a, string[] b)
+    {
+        int m = a.Length, n = b.Length;
+        var dp = new int[m + 1, n + 1];
+
+        for (int i = 1; i <= m; i++)
+            for (int j = 1; j <= n; j++)
+                dp[i, j] = a[i - 1].TrimEnd('\r') == b[j - 1].TrimEnd('\r')
+                    ? dp[i - 1, j - 1] + 1
+                    : Math.Max(dp[i - 1, j], dp[i, j - 1]);
+
+        // 역추적
+        var lcs = new List<string>();
+        int x = m, y = n;
+        while (x > 0 && y > 0)
+        {
+            if (a[x - 1].TrimEnd('\r') == b[y - 1].TrimEnd('\r'))
+            {
+                lcs.Add(a[x - 1].TrimEnd('\r'));
+                x--; y--;
+            }
+            else if (dp[x - 1, y] > dp[x, y - 1])
+                x--;
+            else
+                y--;
+        }
+        lcs.Reverse();
+        return lcs;
+    }
+
+    /// <summary>diff 결과를 통계 요약 문자열로 반환합니다.</summary>
+    public static string GetSummary(List<DiffLine> diff)
+    {
+        int added = diff.Count(d => d.Type == DiffType.Added);
+        int removed = diff.Count(d => d.Type == DiffType.Removed);
+        return $"+{added} -{removed} 라인 변경";
+    }
+}