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//
// NNArrayDiffCalculator.m
// ArrayDiff
//
// Created by Nick Tymchenko on 07/12/14.
// Copyright (c) 2014 Nick Tymchenko. All rights reserved.
//
#import "NNArrayDiffCalculator.h"
#import "NNArrayDiff.h"
#import "NNArrayDiffChange.h"
@implementation NNArrayDiffCalculator
#pragma mark - Public
- (NNArrayDiff *)calculateDiffForObjectsBefore:(NSArray *)objectsBefore andAfter:(NSArray *)objectsAfter
{
// TODO: docs!
NNMutableArrayDiff *diff = [[NNMutableArrayDiff alloc] init];
NSOrderedSet *before = [self idsOfObjects:objectsBefore withBlock:self.objectIdBlock];
NSOrderedSet *after = [self idsOfObjects:objectsAfter withBlock:self.objectIdBlock];
[before enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if (![after containsObject:obj]) {
[diff.deleted addIndex:idx];
}
}];
[after enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if (![before containsObject:obj]) {
[diff.inserted addIndex:idx];
}
}];
NSMutableOrderedSet *sameBefore = [before mutableCopy];
[sameBefore removeObjectsAtIndexes:diff.deleted];
NSMutableOrderedSet *sameAfter = [after mutableCopy];
[sameAfter removeObjectsAtIndexes:diff.inserted];
// http://en.wikipedia.org/wiki/Longest_increasing_subsequence
NSUInteger n = [sameBefore count];
NSUInteger *X = malloc(sizeof(NSUInteger) * n);
NSUInteger *M = malloc(sizeof(NSUInteger) * n);
NSUInteger *P = malloc(sizeof(NSUInteger) * n);
[sameBefore enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
X[idx] = [after indexOfObject:obj];
}];
NSInteger L = 0;
for (NSUInteger i = 0; i < n; ++i) {
NSInteger j = -1;
// Find the largest j in [0; L-1] such that X[M[j]] < X[i]
if (L > 0 && X[M[L-1]] < X[i]) {
j = L-1;
} else {
NSInteger left = 0;
NSInteger right = L-1;
NSInteger mid;
while (right > left + 1) {
mid = (left + right) / 2;
if (X[M[mid]] < X[i]) {
left = mid;
} else {
right = mid;
}
}
if (L > 0) {
if (right >= 0 && X[M[right]] < X[i]) {
j = right;
} else if (X[M[left]] < X[i]) {
j = left;
}
}
}
P[i] = (j != -1) ? M[j] : -1;
if (j+1 == L || X[i] < X[M[j+1]]) {
M[j+1] = i;
L = MAX(L, j+2);
}
}
NSMutableIndexSet *afterStaticIndexes = [NSMutableIndexSet indexSet];
NSUInteger index = NSNotFound;
for (NSUInteger i = 0; i < L; ++i) {
if (index != NSNotFound) {
index = P[index];
} else {
index = M[L-1];
}
NSUInteger afterIndex = X[index];
[afterStaticIndexes addIndex:afterIndex];
}
free(X);
free(M);
free(P);
[sameAfter enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSUInteger beforeIndex = [before indexOfObject:obj];
NSUInteger afterIndex = [after indexOfObject:obj];
NNDiffChangeType changeType = 0;
if (![afterStaticIndexes containsIndex:afterIndex]) {
changeType |= NNDiffChangeMove;
}
if (self.objectUpdatedBlock(objectsBefore[beforeIndex], objectsAfter[afterIndex])) {
changeType |= NNDiffChangeUpdate;
}
if (changeType != 0) {
NNArrayDiffChange *change = [[NNArrayDiffChange alloc] initWithBefore:beforeIndex after:afterIndex type:changeType];
[diff.changed addObject:change];
}
}];
return [diff copy];
}
#pragma mark - Private
- (NSOrderedSet *)idsOfObjects:(NSArray *)array withBlock:(NNDiffObjectIdBlock)block
{
NSMutableArray *ids = [NSMutableArray arrayWithCapacity:[array count]];
for (id object in array) {
[ids addObject:block(object)];
}
return [NSOrderedSet orderedSetWithArray:ids];
}
@end