java-diff-utils · wumpz · Nov 28, 2021 · Jun 10, 2021 · Jun 10, 2021 · Jun 10, 2021
diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/AbstractDelta.java b/java-diff-utils/src/main/java/com/github/difflib/patch/AbstractDelta.java
@@ -70,6 +70,19 @@ protected VerifyChunk verifyAntApplyTo(List<T> target) throws PatchFailedExcepti
 
     protected abstract void restore(List<T> target);
 
+    /**
+     * Apply patch fuzzy.
+     *
+     * @param target the list this patch will be applied to
+     * @param fuzz the number of elements to ignore before/after the patched elements
+     * @param position the position this patch will be applied to. ignores {@code source.getPosition()}
+     * @see <a href="https://www.gnu.org/software/diffutils/manual/html_node/Inexact.html">Description of Fuzzy Patch</a> for more information.
+     */
+    @SuppressWarnings("RedundantThrows")
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int position) throws PatchFailedException {
+        throw new UnsupportedOperationException(this.getClass().getSimpleName() + " does not supports applying patch fuzzy");
+    }
+
     /**
      * Create a new delta of the actual instance with customized chunk data.
      */

diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/ChangeDelta.java b/java-diff-utils/src/main/java/com/github/difflib/patch/ChangeDelta.java
@@ -66,6 +66,19 @@ protected void restore(List<T> target) {
         }
     }
 
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int position) throws PatchFailedException {
+        int size = getSource().size();
+        for (int i = fuzz; i < size - fuzz; i++) {
+            target.remove(position + fuzz);
+        }
+
+        int i = fuzz;
+        for (T line : getTarget().getLines().subList(fuzz, getTarget().size() - fuzz)) {
+            target.add(position + i, line);
+            i++;
+        }
+    }
+
     @Override
     public String toString() {
         return "[ChangeDelta, position: " + getSource().getPosition() + ", lines: "

diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/Chunk.java b/java-diff-utils/src/main/java/com/github/difflib/patch/Chunk.java
@@ -95,10 +95,28 @@ public Chunk(int position, T[] lines) {
      * @throws com.github.difflib.patch.PatchFailedException
      */
     public VerifyChunk verifyChunk(List<T> target) throws PatchFailedException {
-        if (position > target.size() || last() > target.size()) {
+        return verifyChunk(target, 0, getPosition());
+    }
+
+    /**
+     * Verifies that this chunk's saved text matches the corresponding text in
+     * the given sequence.
+     *
+     * @param target the sequence to verify against.
+     * @param fuzz the count of ignored prefix/suffix
+     * @param position the position of target
+     * @throws com.github.difflib.patch.PatchFailedException
+     */
+    public VerifyChunk verifyChunk(List<T> target, int fuzz, int position) throws PatchFailedException {
+        //noinspection UnnecessaryLocalVariable
+        int startIndex = fuzz;
+        int lastIndex = size() - fuzz;
+        int last = position + size() - 1;
+
+        if (position + fuzz > target.size() || last - fuzz > target.size()) {
             return VerifyChunk.POSITION_OUT_OF_TARGET;
         }
-        for (int i = 0; i < size(); i++) {
+        for (int i = startIndex; i < lastIndex; i++) {
             if (!target.get(position + i).equals(lines.get(i))) {
                 return VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET;
             }

diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java b/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java
@@ -35,6 +35,14 @@ protected void applyTo(List<T> target) throws PatchFailedException {
     protected void restore(List<T> target) {
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int delta) {
+        // equals so no operations
+    }
+
     @Override
     public String toString() {
         return "[EqualDelta, position: " + getSource().getPosition() + ", lines: "

diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java b/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java
@@ -66,6 +66,117 @@ public List<T> applyTo(List<T> target) throws PatchFailedException {
         return result;
     }
 
+    private static class PatchApplyingContext<T> {
+        public final List<T> result;
+        public final int maxFuzz;
+
+        // the position last patch applied to.
+        public int lastPatchEnd = -1;
+
+        ///// passing values from find to apply
+        public int currentFuzz = 0;
+
+        public int defaultPosition;
+        public boolean beforeOutRange = false;
+        public boolean afterOutRange = false;
+
+        private PatchApplyingContext(List<T> result, int maxFuzz) {
+            this.result = result;
+            this.maxFuzz = maxFuzz;
+        }
+    }
+
+    public List<T> applyFuzzy(List<T> target, int maxFuzz) throws PatchFailedException {
+        PatchApplyingContext<T> ctx = new PatchApplyingContext<>(new ArrayList<>(target), maxFuzz);
+
+        // the difference between patch's position and actually applied position
+        int lastPatchDelta = 0;
+
+        for (AbstractDelta<T> delta : getDeltas()) {
+            ctx.defaultPosition = delta.getSource().getPosition() + lastPatchDelta;
+            int patchPosition = findPositionFuzzy(ctx, delta);
+            if (0 <= patchPosition) {
+                delta.applyFuzzyToAt(ctx.result, ctx.currentFuzz, patchPosition);
+                lastPatchDelta = patchPosition - delta.getSource().getPosition();
+                ctx.lastPatchEnd = delta.getSource().last() + lastPatchDelta;
+            } else {
+                conflictOutput.processConflict(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET, delta, ctx.result);
+            }
+        }
+
+        return ctx.result;
+    }
+
+    // negative for not found
+    private int findPositionFuzzy(PatchApplyingContext<T> ctx, AbstractDelta<T> delta) throws PatchFailedException {
+        for (int fuzz = 0; fuzz <= ctx.maxFuzz; fuzz++) {
+            ctx.currentFuzz = fuzz;
+            int foundPosition = findPositionWithFuzz(ctx, delta, fuzz);
+            if (foundPosition >= 0) {
+                return foundPosition;
+            }
+        }
+        return -1;
+    }
+
+    // negative for not found
+    private int findPositionWithFuzz(PatchApplyingContext<T> ctx, AbstractDelta<T> delta, int fuzz) throws PatchFailedException {
+        if (delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition) == VerifyChunk.OK) {
+            return ctx.defaultPosition;
+        }
+
+        ctx.beforeOutRange = false;
+        ctx.afterOutRange = false;
+
+        // moreDelta >= 0: just for overflow guard, not a normal condition
+        //noinspection OverflowingLoopIndex
+        for (int moreDelta = 0; moreDelta >= 0; moreDelta++) {
+            int pos = findPositionWithFuzzAndMoreDelta(ctx, delta, fuzz, moreDelta);
+            if (pos >= 0) {
+                return pos;
+            }
+            if (ctx.beforeOutRange && ctx.afterOutRange) {
+                break;
+            }
+        }
+
+        return -1;
+    }
+
+    // negative for not found
+    private int findPositionWithFuzzAndMoreDelta(PatchApplyingContext<T> ctx, AbstractDelta<T> delta, int fuzz, int moreDelta) throws PatchFailedException {
+        // range check: can't apply before end of last patch
+        if (!ctx.beforeOutRange) {
+            int beginAt = ctx.defaultPosition - moreDelta + fuzz;
+            // We can't apply patch before end of last patch.
+            if (beginAt <= ctx.lastPatchEnd) {
+                ctx.beforeOutRange = true;
+            }
+        }
+        // range check: can't apply after end of result
+        if (!ctx.afterOutRange) {
+            int beginAt = ctx.defaultPosition + moreDelta + delta.getSource().size() - fuzz;
+            // We can't apply patch before end of last patch.
+            if (ctx.result.size() < beginAt) {
+                ctx.afterOutRange = true;
+            }
+        }
+
+        if (!ctx.beforeOutRange) {
+            VerifyChunk before = delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition - moreDelta);
+            if (before == VerifyChunk.OK) {
+                return ctx.defaultPosition - moreDelta;
+            }
+        }
+        if (!ctx.afterOutRange) {
+            VerifyChunk after = delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition + moreDelta);
+            if (after == VerifyChunk.OK) {
+                return ctx.defaultPosition + moreDelta;
+            }
+        }
+        return -1;
+    }
+
     /**
      * Standard Patch behaviour to throw an exception for pathching conflicts.
      */