From 829f3a9665c18c38ad9f8c73a868e393ebbb2e59 Mon Sep 17 00:00:00 2001
From: wzxjiang <wzxjiang@foxmail.com>
Date: Thu, 24 May 2018 14:43:11 +0800
Subject: [PATCH] modification add base

---
 Sources/Sdifft/Diff.swift           | 14 ++++++++++-
 Tests/SdifftTests/SdifftTests.swift | 37 ++++++++++++++++++++---------
 2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/Sources/Sdifft/Diff.swift b/Sources/Sdifft/Diff.swift
index 85f21a0..4dfa06c 100644
--- a/Sources/Sdifft/Diff.swift
+++ b/Sources/Sdifft/Diff.swift
@@ -134,16 +134,28 @@ extension Array where Element == Int {
 }
 
 public struct Modification {
+    public enum Base {
+        case from
+        case to
+    }
+    
     public let add: [CountableClosedRange<Int>]
     public let delete: [CountableClosedRange<Int>]
     public let same: [CountableClosedRange<Int>]
+    public let base: Base
     
     init(from: String, to: String, matrix: Matrix) {
         let same =
             lcs(from: from, to: to, position: (from.count, to.count), matrix: matrix, same: ([], []))
         add = same.to.getChangeRanges(max: to.count - 1)
         delete = same.from.getChangeRanges(max: from.count - 1)
-        self.same = same.to.getSameRanges()
+        if add.isEmpty {
+            base = .from
+            self.same = same.from.getSameRanges()
+        } else {
+            base = .to
+            self.same = same.to.getSameRanges()
+        }
     }
 }
 
diff --git a/Tests/SdifftTests/SdifftTests.swift b/Tests/SdifftTests/SdifftTests.swift
index 3fa6475..b8c48b5 100644
--- a/Tests/SdifftTests/SdifftTests.swift
+++ b/Tests/SdifftTests/SdifftTests.swift
@@ -1,6 +1,14 @@
 import XCTest
 @testable import Sdifft
 
+extension String {
+    subscript(_ range: CountableClosedRange<Int>) -> String {
+        let start = index(startIndex, offsetBy: range.lowerBound)
+        let end = index(startIndex, offsetBy: range.upperBound)
+        return String(self[start...end])
+    }
+}
+
 class DiffTests: XCTestCase {
     func testMatrix() {
         assert(
@@ -127,6 +135,13 @@ class DiffTests: XCTestCase {
         assert(diff2.modification.add == [0...0, 2...3])
         assert(diff2.modification.delete == [1...1])
         assert(diff2.modification.same == [1...1])
+        
+        let to3 = "A\r\nB\r\nC"
+        let from3 = "A\r\n\r\nB\r\n\r\nC"
+        let diff3 = Diff(from: from3, to: to3)
+        assert(diff3.modification.add == [])
+        assert(diff3.modification.delete == [1...1, 4...4])
+        assert(diff3.modification.same == [0...0, 2...3, 5...6])
     }
     
     func testString1() {
@@ -134,12 +149,12 @@ class DiffTests: XCTestCase {
         let from = "bj"
         let diff = Diff(from: from, to: to)
         assert(
-            (to as NSString).substring(with: NSRange(diff.modification.add[0])) == "a" &&
-            (to as NSString).substring(with: NSRange(diff.modification.add[1])) == "cdhi" &&
-            (to as NSString).substring(with: NSRange(diff.modification.add[2])) == "k" &&
+            to[diff.modification.add[0]] == "a" &&
+            to[diff.modification.add[1]] == "cdhi" &&
+            to[diff.modification.add[2]] == "k" &&
             diff.modification.delete.count == 0 &&
-            (to as NSString).substring(with: NSRange(diff.modification.same[0])) == "b" &&
-            (to as NSString).substring(with: NSRange(diff.modification.same[1])) == "j")
+            to[diff.modification.same[0]] == "b" &&
+            to[diff.modification.same[1]] == "j")
     }
     
     func testString2() {
@@ -147,12 +162,12 @@ class DiffTests: XCTestCase {
         let from = "bexj"
         let diff = Diff(from: from, to: to)
         assert(
-            (to as NSString).substring(with: NSRange(diff.modification.add[0])) == "a" &&
-            (to as NSString).substring(with: NSRange(diff.modification.add[1])) == "cdhi" &&
-            (to as NSString).substring(with: NSRange(diff.modification.add[2])) == "k" &&
-            (from as NSString).substring(with: NSRange(diff.modification.delete[0])) == "ex" &&
-            (to as NSString).substring(with: NSRange(diff.modification.same[0])) == "b" &&
-            (to as NSString).substring(with: NSRange(diff.modification.same[1])) == "j"
+            to[diff.modification.add[0]] == "a" &&
+            to[diff.modification.add[1]] == "cdhi" &&
+            to[diff.modification.add[2]] == "k" &&
+            from[diff.modification.delete[0]] == "ex" &&
+            to[diff.modification.same[0]] == "b" &&
+            to[diff.modification.same[1]] == "j"
         )
     }