/*

File: TreeNode.m

Abstract:

Generic Tree node and data structures (TreeNode, and TreeNodeData).

TreeNode is a node in a doubly linked tree data structure.  TreeNode's 

have weak references to their parent (to avoid retain cycles since 

parents retain their children).  Each node has 0 or more children and

a reference to a piece of TreeNodeData data. The TreeNode provides method 

to manipulate and extract structural information about a tree.  For 

instance, TreeNode implements: insertChild:atIndex:, removeChild:, 

isDescendantOfNode:, and other useful operations on tree nodes. TreeNode 

and TreeNodeData provide the structure and common functionality of trees, 

and are expected to be subclassed.

Version: <1.0>

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*/ 

#import "TreeNode.h"

#import "NSArray_Extensions.h"

@implementation TreeNodeData 

- (NSComparisonResult)compare:(TreeNodeData *)other {

    // Return anything, it is expected this will be overridden by subclasses.

    // For instance, SimpleTreeData compares names!

    return NSOrderedAscending;

}

@end

@implementation TreeNode

+ (id)treeNodeWithData:(TreeNodeData*)data {

    return [[[TreeNode alloc] initWithData: data  parent:nil children:[NSArray array]] autorelease]; 

}

- (id)initWithData:(TreeNodeData*)data parent:(TreeNode*)parent children:(NSArray*)children {

    self = [super init];

    if (self==nil) return nil;

    nodeData = [data retain];

    nodeChildren = [[NSMutableArray arrayWithArray:children] retain];

    nodeParent = parent;

    return self;

}

- (void)dealloc {

    [nodeData release];

    [nodeChildren release];

    nodeData = nil;

    nodeChildren = nil;

    [super dealloc];

}

// ================================================================

// Methods used to manage a node and its children.

// ================================================================

- (void)setNodeData:(TreeNodeData*)data { 

    [nodeData release]; 

    nodeData = [data retain]; 

}

- (TreeNodeData*)nodeData { 

    return nodeData; 

}

- (void)setNodeParent:(TreeNode*)parent {

    nodeParent = parent; 

}

- (TreeNode*)nodeParent { 

    return nodeParent; 

}

- (void)insertChild:(TreeNode*)child atIndex:(int)index {

    [nodeChildren insertObject:child atIndex:index];

    [child setNodeParent: self];

}

- (void)insertChildren:(NSArray*)children atIndex:(int)index {

    [nodeChildren insertObjectsFromArray: children atIndex: index];

    [children makeObjectsPerformSelector:@selector(setNodeParent:) withObject:self];

}

- (void)_removeChildrenIdenticalTo:(NSArray*)children {

    TreeNode *child;

    NSEnumerator *childEnumerator = [children objectEnumerator];

    [children makeObjectsPerformSelector:@selector(setNodeParent:) withObject:nil];

    while ((child=[childEnumerator nextObject])) {

        [nodeChildren removeObjectIdenticalTo:child];

    }

}

- (void)removeChild:(TreeNode*)child {

    int index = [self indexOfChild: child];

    if (index!=NSNotFound) {

        [self _removeChildrenIdenticalTo: [NSArray arrayWithObject: [self childAtIndex:index]]];

    }

}

- (void)removeFromParent {

    [[self nodeParent] removeChild:self];

}

- (int)indexOfChild:(TreeNode*)child {

    return [nodeChildren indexOfObject:child];

}

- (int)indexOfChildIdenticalTo:(TreeNode*)child {

    return [nodeChildren indexOfObjectIdenticalTo:child];

}

- (int)numberOfChildren {

    return [nodeChildren count];

}

- (NSArray*)children {

    return [NSArray arrayWithArray: nodeChildren];

}

- (TreeNode*)firstChild {

    return [nodeChildren objectAtIndex:0];

}

- (TreeNode*)lastChild {

    return [nodeChildren lastObject];

}

- (TreeNode*)childAtIndex:(int)index {

    return [nodeChildren objectAtIndex:index];

}

- (BOOL)isDescendantOfNode:(TreeNode*)node {

    // returns YES if 'node' is an ancestor.

    // Walk up the tree, to see if any of our ancestors is 'node'.

    TreeNode *parent = self;

    while(parent) {

        if(parent==node) return YES;

        parent = [parent nodeParent];

    }

    return NO;

}

- (BOOL)isDescendantOfNodeInArray:(NSArray*)nodes {

    // returns YES if any 'node' in the array 'nodes' is an ancestor of ours.

    // For each node in nodes, if node is an ancestor return YES.  If none is an

    // ancestor, return NO.

    NSEnumerator *nodeEnum = [nodes objectEnumerator];

    TreeNode *node = nil;

    while((node=[nodeEnum nextObject])) {

        if([self isDescendantOfNode:node]) return YES;

    }

    return NO;

}

- (void)recursiveSortChildren {

    [nodeChildren sortUsingSelector:@selector(compare:)];

    [nodeChildren makeObjectsPerformSelector: @selector(recursiveSortChildren)];

}

- (NSString*)description {

    // Return something that will be useful for debugging.

    return [NSString stringWithFormat: @"{%@}", nodeData];

}

// Returns the minimum nodes from 'allNodes' required to cover the nodes in 'allNodes'.

// This methods returns an array containing nodes from 'allNodes' such that no node in

// the returned array has an ancestor in the returned array.

// There are better ways to compute this, but this implementation should be efficient for our app.

+ (NSArray *) minimumNodeCoverFromNodesInArray: (NSArray *)allNodes {

    NSMutableArray *minimumCover = [NSMutableArray array];

    NSMutableArray *nodeQueue = [NSMutableArray arrayWithArray:allNodes];

    TreeNode *node = nil;

    while ([nodeQueue count]) {

        node = [nodeQueue objectAtIndex:0];

        [nodeQueue removeObjectAtIndex:0];

        while ( [node nodeParent] && [nodeQueue containsObjectIdenticalTo:[node nodeParent]] ) {

            [nodeQueue removeObjectIdenticalTo: node];

            node = [node nodeParent];

        }

        if (![node isDescendantOfNodeInArray: minimumCover]) [minimumCover addObject: node];

        [nodeQueue removeObjectIdenticalTo: node];

    }

    return minimumCover;

}

- (NSComparisonResult)compare:(TreeNode*)node {

    // Compare nodes to each other by comparing the data part.

    return [nodeData compare:[node nodeData]];

}

@end