add the diffCharacters function

dunosaurs · May 11, 2022 · 199af8f · 199af8f
1 parent 2dc4263
commit 199af8f
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Showing 4 changed files with 127 additions and 3 deletions.
diff --git a/mod.ts b/mod.ts
@@ -1,4 +1,4 @@
-import { diffCharacter } from "./types.ts";
+import { IDiffCharacter } from "./types.ts";
 
 export function longestCommonSubsequence(a: string, b: string): string {
   const arr: {
@@ -48,7 +48,11 @@ export function longestCommonSubsequence(a: string, b: string): string {
         }
       }
       if (a[i] === b[j]) {
-        if (i > 0 && j > 0 && arr[i - 1][j - 1].length + 1 > currentObject.length) {
+        if (
+          i > 0 &&
+          j > 0 &&
+          arr[i - 1][j - 1].length + 1 > currentObject.length
+        ) {
           currentObject.length = arr[i - 1][j - 1].length + 1;
           currentObject.previous = [i - 1, j - 1];
           currentObject.character = a[i];
@@ -71,4 +75,74 @@ export function longestCommonSubsequence(a: string, b: string): string {
     currentObject = arr[currentObject.previous[0]][currentObject.previous[1]];
   }
   return result;
+}
+
+export function diffCharacters(oldString: string, newString: string): IDiffCharacter[] {
+  const commonSubsequence = longestCommonSubsequence(oldString, newString);
+  const result: IDiffCharacter[] = [];
+  let oldStringPointer = 0;
+  let newStringPointer = 0;
+  let commonSubsequencePointer = 0;
+  while (
+    oldStringPointer < oldString.length ||
+    newStringPointer < newString.length ||
+    commonSubsequencePointer < commonSubsequence.length
+  ) {
+    if (
+      oldStringPointer < oldString.length &&
+      oldString[oldStringPointer] !==
+        commonSubsequence[commonSubsequencePointer]
+    ) {
+      result.push({
+        character: oldString[oldStringPointer],
+        wasAdded: false,
+        wasRemoved: true,
+      });
+      oldStringPointer++;
+    } else if (
+      newStringPointer < newString.length &&
+      newString[newStringPointer] !==
+        commonSubsequence[commonSubsequencePointer]
+    ) {
+      result.push({
+        character: newString[newStringPointer],
+        wasAdded: true,
+        wasRemoved: false,
+      });
+      newStringPointer++;
+    } else if (
+      oldStringPointer < oldString.length &&
+      newStringPointer < newString.length &&
+      oldString[oldStringPointer] ===
+        commonSubsequence[commonSubsequencePointer] &&
+      newString[newStringPointer] ===
+        commonSubsequence[commonSubsequencePointer]
+    ) {
+      result.push({
+        character: commonSubsequence[commonSubsequencePointer],
+        wasAdded: false,
+        wasRemoved: false,
+      });
+      oldStringPointer++;
+      newStringPointer++;
+      commonSubsequencePointer++;
+    }
+  }
+  return result;
+}
+
+
+for (const character of diffCharacters("boopa", "boop beep boppy")) {
+  let finalString = "";
+  if (character.wasRemoved) {
+    // print red if removed without newline
+    finalString += `\x1b[31m${character.character}\x1b[0m`;
+  } else if (character.wasAdded) {
+    // print green if added
+    finalString += `\x1b[32m${character.character}\x1b[0m`;
+  } else {
+    // print white if unchanged
+    finalString += `\x1b[37m${character.character}\x1b[0m`;
+  }
+  console.log(finalString);
 }
diff --git a/mod_test.ts b/mod_test.ts
@@ -4,4 +4,7 @@ import {longestCommonSubsequence} from "./mod.ts";
 Deno.test("Longest Common Subsequence", () => {
   assertEquals(longestCommonSubsequence("abc", "abc"), "abc");
   assertEquals(longestCommonSubsequence("abgd", "adh"), "ad");
+  assertEquals(longestCommonSubsequence("xabcd", "xabcf"), "xabc");
+  assertEquals(longestCommonSubsequence("ABCBDAB", "BDCABA"), "BCBA");
+  assertEquals(longestCommonSubsequence("BACDCABAAAADDACADDBBDAABDCDBBBCCDACCCDBDD", "BDACCACCDCCBADACDDACABBDAAABCDBBAADBCCCCB"), "BACDCBAADDACABBDAABCDBBBCCCCB");
 });
diff --git a/readme.md b/readme.md
@@ -0,0 +1,47 @@
+# diff
+
+> Deno library for usage of diff
+> Based on the O(n * m) DP solution to the LCS problem
+
+```typescript
+import { diffCharacters } from "https://deno.land/x/diff/mod.ts";
+
+diffCharacters("ABCBDAB", "BDCABA")
+```
+
+## API
+
+*diffCharacters(oldString: string, newString: string)*
+Compares two strings by character and returns a list `IDiffCharacter` objects (explained below)
+
+*longestCommonSubsequence(a: string, b: string)*
+Compares two strings by character and returns the [longest common subsequence](https://en.wikipedia.org/wiki/Longest_common_subsequence_problem)
+
+## Types
+
+*IDiffCharacter*
+```typescript
+{
+  character: string;
+  wasAdded: boolean;
+  wasRemoved: boolean;
+}
+```
+The object contains the character and whether that character was removed, added, or neither. Here is example usage
+```typescript
+for (const character of diffCharacters("boopa", "boop beep boppy")) {
+  let finalString = "";
+  if (character.wasRemoved) {
+    // print red if removed without newline
+    finalString += `\x1b[31m${character.character}\x1b[0m`;
+  } else if (character.wasAdded) {
+    // print green if added
+    finalString += `\x1b[32m${character.character}\x1b[0m`;
+  } else {
+    // print white if unchanged
+    finalString += `\x1b[37m${character.character}\x1b[0m`;
+  }
+  console.log(finalString);
+}
+```
+
diff --git a/types.ts b/types.ts
@@ -1,4 +1,4 @@
-export type diffCharacter = {
+export type IDiffCharacter = {
   character: string;
   wasAdded: boolean;
   wasRemoved: boolean;