cog/Playlist/DNDArrayController.m

#import "DNDArrayController.h"

#import "Logging.h"

NSString *CogDNDIndexType = @"org.cogx.cog.dnd-index";
NSString *CogUrlsPboardType = @"org.cogx.cog.url";
NSString *iTunesDropType = @"com.apple.tv.metadata";

@implementation DNDArrayController

- (void)awakeFromNib {
    [super awakeFromNib];
    // register for drag and drop
    NSPasteboardType fileType;
    if (@available(macOS 10.13, *)) {
        fileType = NSPasteboardTypeFileURL;
    }
    else {
        fileType = NSFilenamesPboardType;
    }
    [self.tableView registerForDraggedTypes:@[CogDNDIndexType,
            CogUrlsPboardType,
            fileType,
            iTunesDropType]];
}


- (id <NSPasteboardWriting>)tableView:(NSTableView *)tableView
               pasteboardWriterForRow:(NSInteger)row {
    NSPasteboardItem *item = [[NSPasteboardItem alloc] init];
    [item setString:[@(row) stringValue] forType:CogDNDIndexType];

    return item;
}


- (void)tableView:(NSTableView *)tableView
  draggingSession:(NSDraggingSession *)session
 willBeginAtPoint:(NSPoint)screenPoint
    forRowIndexes:(NSIndexSet *)rowIndexes {
    DLog(@"Drag session started with indexes: %@", rowIndexes);
}


- (NSDragOperation)tableView:(NSTableView *)tableView
                validateDrop:(id <NSDraggingInfo>)info
                 proposedRow:(NSInteger)row
       proposedDropOperation:(NSTableViewDropOperation)dropOperation {
    NSDragOperation dragOp = NSDragOperationCopy;

    if ([info draggingSource] == tableView)
        dragOp = NSDragOperationMove;

    DLog(@"VALIDATING DROP!");
    // we want to put the object at, not over,
    // the current row (contrast NSTableViewDropOn)
    [tableView setDropRow:row dropOperation:NSTableViewDropAbove];

    return dragOp;
}


- (BOOL)tableView:(NSTableView *)tableView
       acceptDrop:(id <NSDraggingInfo>)info
              row:(NSInteger)row
    dropOperation:(NSTableViewDropOperation)dropOperation {
    if (row < 0) {
        row = 0;
    }

    NSArray<NSPasteboardItem *> *items = info.draggingPasteboard.pasteboardItems;
    // if drag source is self, it's a move
    if ([info draggingSource] == tableView || items == nil) {
        NSMutableIndexSet *indexSet = [NSMutableIndexSet indexSet];
        for (NSPasteboardItem *item in items) {
            [indexSet addIndex:(NSUInteger) [[item stringForType:CogDNDIndexType] intValue]];
        }
        if ([indexSet count] > 0) {
            DLog(@"INDEX SET ON DROP: %@", indexSet);
            NSArray *selected = [[self arrangedObjects] objectsAtIndexes:indexSet];
            [self moveObjectsInArrangedObjectsFromIndexes:indexSet toIndex:(unsigned int) row];

            [self setSelectedObjects:selected];

            DLog(@"ACCEPTING DROP!");
            return YES;
        }
    }
    DLog(@"REJECTING DROP!");
    return NO;
}


- (void)moveObjectsInArrangedObjectsFromIndexes:(NSIndexSet *)indexSet
                                        toIndex:(NSUInteger)insertIndex {
    __block NSUInteger rangeCount = 0;
    __block NSUInteger firstIndex = 0;
    [indexSet enumerateRangesUsingBlock:^(NSRange range, BOOL * _Nonnull stop) {
        if (++rangeCount == 1)
            firstIndex = range.location;
    }];
    
    if (rangeCount == 1 &&
        (insertIndex >= firstIndex &&
         insertIndex < firstIndex + [indexSet count])) // Null operation
        return;
    
    NSArray *objects = [self arrangedObjects];
    NSUInteger index = [indexSet lastIndex];

    NSUInteger aboveInsertIndexCount = 0;
    id object;
    NSUInteger removeIndex;

    while (NSNotFound != index) {
        if (index >= insertIndex) {
            removeIndex = index + aboveInsertIndexCount;
            aboveInsertIndexCount += 1;
        } else {
            removeIndex = index;
            insertIndex -= 1;
        }

        object = objects[removeIndex];

        [self removeObjectAtArrangedObjectIndex:removeIndex];
        [self insertObject:object atArrangedObjectIndex:insertIndex];

        index = [indexSet indexLessThanIndex:index];
    }
}

- (void)moveObjectsFromIndex:(NSUInteger)fromIndex
     toArrangedObjectIndexes:(NSIndexSet *)indexSet {
    __block NSUInteger rangeCount = 0;
    __block NSUInteger firstIndex = 0;
    __block NSUInteger _fromIndex = fromIndex;
    [indexSet enumerateRangesUsingBlock:^(NSRange range, BOOL * _Nonnull stop) {
        if (++rangeCount == 1)
            firstIndex = range.location;
        if (_fromIndex >= range.location) {
            if (_fromIndex < range.location + range.length)
                _fromIndex = range.location;
            else
                _fromIndex -= range.length;
        }
    }];
    
    if (rangeCount == 1 &&
        (fromIndex >= firstIndex &&
         fromIndex < firstIndex + [indexSet count])) // Null operation
        return;

    fromIndex = _fromIndex;
    
    NSArray *objects = [[self arrangedObjects] subarrayWithRange:NSMakeRange(fromIndex, [indexSet count])];
    NSUInteger index = [indexSet firstIndex];

    NSUInteger itemIndex = 0;
    id object;
    
    fromIndex += [objects count];
    for (NSUInteger i = 0; i < [objects count]; i++) {
        [self removeObjectAtArrangedObjectIndex:--fromIndex];
    }

    while (NSNotFound != index) {
        object = objects[itemIndex++];

        [self insertObject:object atArrangedObjectIndex:index];

        index = [indexSet indexGreaterThanIndex:index];
    }
}


@end