Split logic for fit candidates on an iterator

Author: piranna

src/patch/apply.js

@@ -51,50 +51,69 @@ export function applyPatch(source, uniDiff, options = {}) {
     return true;
   }
 
-  // Search best fit offsets for each hunk based on the previous ones
-  for (let i = 0; i < hunks.length; i++) {
-    let hunk = hunks[i],
+  function distanceIterator(toPos, minLine, maxLine) {
+    let wantForward = true,
         backwardExhausted = false,
         forwardExhausted = false,
-        localOffset = 0,
-        toPos = offset + hunk.oldStart - 1,
-        maxLine = lines.length - hunk.oldLines,
-        toCheck;
+        localOffset = 1;
+
+    return function iterator() {
+      if (wantForward && !forwardExhausted) {
+        if (backwardExhausted) {
+          localOffset++;
+        } else {
+          wantForward = false;
+        }
+
+        // Check if trying to fit beyond text length, and if not, check it fits
+        // after offset location (or desired location on first iteration)
+        if (toPos + localOffset <= maxLine) {
+          return localOffset;
+        }
 
-    for (;;) {
-      // Check if trying to fit beyond text length, and if not, check it fits
-      // after offset location (or desired location on first iteration)
-      toCheck = toPos + localOffset;
-      if (maxLine < toCheck) {
         forwardExhausted = true;
-      } else if (hunkFits(hunk, toCheck)) {
-        hunk.offset = offset += localOffset;
-        break;
       }
 
-      // If we tried to fit hunk before text beginning and beyond text lenght,
-      // then hunk can't be fit on the text so we raise an error
-      if (backwardExhausted && forwardExhausted) {
-        return false;
-      }
+      if (!backwardExhausted) {
+        if (!forwardExhausted) {
+          wantForward = true;
+        }
 
-      // Reset checks of trying to fit outside text limits and increase offset
-      // of the current hunk relative to its desired location
-      backwardExhausted = false;
-      forwardExhausted = false;
-      localOffset++;
+        // Check if trying to fit before text beginning, and if not, check it fits
+        // before offset location
+        if (minLine <= toPos - localOffset) {
+          return -localOffset++;
+        }
 
-      // Check if trying to fit before text beginning, and if not, check it fits
-      // before offset location
-      toCheck = toPos - localOffset;
-      if (toCheck < minLine) {
         backwardExhausted = true;
-      } else if (hunkFits(hunk, toCheck)) {
-        hunk.offset = offset -= localOffset;
+        return iterator();
+      }
+
+      // We tried to fit hunk before text beginning and beyond text lenght, then
+      // hunk can't fit on the text. Return undefined
+    };
+  }
+
+  // Search best fit offsets for each hunk based on the previous ones
+  for (let i = 0; i < hunks.length; i++) {
+    let hunk = hunks[i],
+        maxLine = lines.length - hunk.oldLines,
+        localOffset = 0,
+        toPos = offset + hunk.oldStart - 1;
+
+    let iterator = distanceIterator(toPos, minLine, maxLine);
+
+    for (; localOffset != undefined; localOffset = iterator()) {
+      if (hunkFits(hunk, toPos + localOffset)) {
+        hunk.offset = offset += localOffset;
         break;
       }
     }
 
+    if (localOffset == undefined) {
+      return false;
+    }
+
     // Set lower text limit to end of the current hunk, so next ones don't try
     // to fit over already patched text
     minLine = hunk.offset + hunk.oldStart + hunk.oldLines;

test/patch/apply.js

@@ -374,7 +374,7 @@ describe('patch/apply', function() {
           + 'line5\n');
     });
 
-    it('should succeed when hunk has an offset', function() {
+    it('should succeed when hunk needs a negative offset', function() {
       expect(applyPatch(
           'line1\n'
           + 'line3\n'
@@ -395,6 +395,27 @@ describe('patch/apply', function() {
           + 'line5\n');
     });
 
+    it('should succeed when hunk needs a positive offset', function() {
+      expect(applyPatch(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n'
+          + 'line5\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -1,2 +1,3 @@\n'
+          + ' line3\n'
+          + '+line4\n'
+          + ' line5\n'))
+        .to.equal(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n'
+          + 'line4\n'
+          + 'line5\n');
+    });
+
     it('should allow custom line comparison', function() {
       expect(applyPatch(
           'line2\n'