Chapter 11 - Chat App/ChatAppFinished/Pods/FirebaseDatabase/Firebase/Database/Snapshot/FChildrenNode.m
/*
 * Copyright 2017 Google
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#import "FChildrenNode.h"
#import "FEmptyNode.h"
#import "FConstants.h"
#import "FStringUtilities.h"
#import "FUtilities.h"
#import "FNamedNode.h"
#import "FMaxNode.h"
#import "FTransformedEnumerator.h"
#import "FSnapshotUtilities.h"
#import "FTransformedEnumerator.h"
#import "FPriorityIndex.h"
#import "FUtilities.h"

@interface FChildrenNode ()
@property (nonatomic, strong) NSString *lazyHash;
@end

@implementation FChildrenNode

// Note: The only reason we allow nil priority is to for EmptyNode, since we can't use
// EmptyNode as the priority of EmptyNode.  We might want to consider making EmptyNode its own
// class instead of an empty ChildrenNode.

- (id)init {
    return [self initWithPriority:nil children:[FImmutableSortedDictionary dictionaryWithComparator:[FUtilities keyComparator]]];
}

- (id)initWithChildren:(FImmutableSortedDictionary *)someChildren {
    return [self initWithPriority:nil children:someChildren];
}

- (id)initWithPriority:(id<FNode>)aPriority children:(FImmutableSortedDictionary *)someChildren {
    if (someChildren.isEmpty && aPriority != nil && ![aPriority isEmpty]) {
        [NSException raise:NSInvalidArgumentException format:@"Can't create empty node with priority!"];
    }
    self = [super init];
    if(self) {
        self.children = someChildren;
        self.priorityNode = aPriority;
    }
    return self;
}

- (NSString *) description {
    return [[self valForExport:YES] description];
}

#pragma mark -
#pragma mark FNode methods


- (BOOL) isLeafNode {
    return NO;
}

- (id<FNode>) getPriority {
    if (self.priorityNode) {
        return self.priorityNode;
    } else {
        return [FEmptyNode emptyNode];
    }

}

- (id<FNode>) updatePriority:(id<FNode>)aPriority {
    if ([self.children isEmpty]) {
        return [FEmptyNode emptyNode];
    } else {
        return [[FChildrenNode alloc] initWithPriority:aPriority children:self.children];
    }
}

- (id<FNode>) getImmediateChild:(NSString *) childName {
    if ([childName isEqualToString:@".priority"]) {
        return [self getPriority];
    } else {
        id <FNode> child = [self.children objectForKey:childName];
        return (child == nil) ? [FEmptyNode emptyNode] : child;
    }
}

- (id<FNode>) getChild:(FPath *)path {
    NSString* front = [path getFront];
    if(front == nil) {
        return self;
    }
    else {
        return [[self getImmediateChild:front] getChild:[path popFront]];
    }
}

- (BOOL)hasChild:(NSString *)childName {
    return ![self getImmediateChild:childName].isEmpty;
}


- (id<FNode>) updateImmediateChild:(NSString *)childName withNewChild:(id<FNode>)newChildNode {
    NSAssert(newChildNode != nil, @"Should always be passing nodes.");

    if ([childName isEqualToString:@".priority"]) {
        return [self updatePriority:newChildNode];
    } else {
        FImmutableSortedDictionary *newChildren;
        if (newChildNode.isEmpty) {
            newChildren = [self.children removeObjectForKey:childName];
        } else {
            newChildren = [self.children setObject:newChildNode forKey:childName];
        }
        if (newChildren.isEmpty) {
            return [FEmptyNode emptyNode];
        } else {
            return [[FChildrenNode alloc] initWithPriority:self.getPriority children:newChildren];
        }
    }
}

- (id<FNode>) updateChild:(FPath *)path withNewChild:(id<FNode>)newChildNode {
    NSString* front = [path getFront];
    if(front == nil) {
        return newChildNode;
    } else {
        NSAssert(![front isEqualToString:@".priority"] || path.length == 1, @".priority must be the last token in a path.");
        id<FNode> newImmediateChild = [[self getImmediateChild:front] updateChild:[path popFront] withNewChild:newChildNode];
        return [self updateImmediateChild:front withNewChild:newImmediateChild];
    }
}

- (BOOL) isEmpty {
    return [self.children isEmpty];
}

- (int) numChildren {
    return [self.children count];
}

- (id) val {
    return [self valForExport:NO];
}

- (id) valForExport:(BOOL)exp {
    if([self isEmpty]) {
        return [NSNull null];
    }

    __block int numKeys = 0;
    __block NSInteger maxKey = 0;
    __block BOOL allIntegerKeys = YES;

    NSMutableDictionary* obj = [[NSMutableDictionary alloc] initWithCapacity:[self.children count]];
    [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> childNode, BOOL *stop) {
        [obj setObject:[childNode valForExport:exp] forKey:key];

        numKeys++;

        // If we already found a string key, don't bother with any of this
        if (!allIntegerKeys) {
            return;
        }

        // Treat leading zeroes that are not exactly "0" as strings
        NSString* firstChar = [key substringWithRange:NSMakeRange(0, 1)];
        if ([firstChar isEqualToString:@"0"] && [key length] > 1) {
            allIntegerKeys = NO;
        } else {
            NSNumber *keyAsNum = [FUtilities intForString:key];
            if (keyAsNum != nil) {
                NSInteger keyAsInt = [keyAsNum integerValue];
                if (keyAsInt > maxKey) {
                    maxKey = keyAsInt;
                }
            } else {
                allIntegerKeys = NO;
            }
        }
    }];

    if (!exp && allIntegerKeys && maxKey < 2 * numKeys) {
        // convert to an array
        NSMutableArray* array = [[NSMutableArray alloc] initWithCapacity:maxKey + 1];
        for (int i = 0; i <= maxKey; ++i) {
            NSString* keyString = [NSString stringWithFormat:@"%i", i];
            id child = obj[keyString];
            if (child != nil) {
                [array addObject:child];
            } else {
                [array addObject:[NSNull null]];
            }
        }
        return array;
    } else {

        if(exp && [self getPriority] != nil && !self.getPriority.isEmpty) {
            obj[kPayloadPriority] = [self.getPriority val];
        }

        return obj;
    }
}

- (NSString *) dataHash {
    if (self.lazyHash == nil) {
        NSMutableString *toHash = [[NSMutableString alloc] init];

        if (!self.getPriority.isEmpty) {
            [toHash appendString:@"priority:"];
            [FSnapshotUtilities appendHashRepresentationForLeafNode:(FLeafNode *)self.getPriority
                                                           toString:toHash
                                                        hashVersion:FDataHashVersionV1];
            [toHash appendString:@":"];
        }

        __block BOOL sawPriority = NO;
        [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
            sawPriority = sawPriority || [[node getPriority] isEmpty];
            *stop = sawPriority;
        }];
        if (sawPriority) {
            NSMutableArray *array = [NSMutableArray array];
            [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
                FNamedNode *namedNode = [[FNamedNode alloc] initWithName:key andNode:node];
                [array addObject:namedNode];
            }];
            [array sortUsingComparator:^NSComparisonResult(FNamedNode *namedNode1, FNamedNode *namedNode2) {
                return [[FPriorityIndex priorityIndex] compareNamedNode:namedNode1 toNamedNode:namedNode2];
            }];
            [array enumerateObjectsUsingBlock:^(FNamedNode *namedNode, NSUInteger idx, BOOL *stop) {
                NSString *childHash = [namedNode.node dataHash];
                if (![childHash isEqualToString:@""]) {
                    [toHash appendFormat:@":%@:%@", namedNode.name, childHash];
                }
            }];
        } else {
            [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
                NSString *childHash = [node dataHash];
                if (![childHash isEqualToString:@""]) {
                    [toHash appendFormat:@":%@:%@", key, childHash];
                }
            }];
        }
        self.lazyHash = [toHash isEqualToString:@""] ? @"" : [FStringUtilities base64EncodedSha1:toHash];
    }
    return self.lazyHash;
}

- (NSComparisonResult)compare:(id <FNode>)other {
    // children nodes come last, unless this is actually an empty node, then we come first.
    if (self.isEmpty) {
        if (other.isEmpty) {
            return NSOrderedSame;
        } else {
            return NSOrderedAscending;
        }
    } else if (other.isLeafNode || other.isEmpty) {
        return NSOrderedDescending;
    } else if (other == [FMaxNode maxNode]) {
        return NSOrderedAscending;
    } else {
        // Must be another node with children.
        return NSOrderedSame;
    }
}

- (BOOL)isEqual:(id <FNode>)other {
    if (other == self) {
        return YES;
    } else if (other == nil) {
        return NO;
    } else if (other.isLeafNode) {
        return NO;
    } else if (self.isEmpty && [other isEmpty]) {
        // Empty nodes do not have priority
        return YES;
    } else {
        FChildrenNode *otherChildrenNode = other;
        if (![self.getPriority isEqual:other.getPriority]) {
            return NO;
        } else if (self.children.count == otherChildrenNode.children.count) {
            __block BOOL equal = YES;
            [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
                id<FNode> child = [otherChildrenNode getImmediateChild:key];
                if (![child isEqual:node]) {
                    equal = NO;
                    *stop = YES;
                }
            }];
            return equal;
        } else {
            return NO;
        }
    }
}

- (NSUInteger)hash {
    __block NSUInteger hashCode = 0;
    [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
        hashCode = 31 * hashCode + key.hash;
        hashCode = 17 * hashCode + node.hash;
    }];
    return 17 * hashCode + self.priorityNode.hash;
}

- (void) enumerateChildrenAndPriorityUsingBlock:(void (^)(NSString *, id<FNode>, BOOL *))block
{
    if ([self.getPriority isEmpty]) {
        [self enumerateChildrenUsingBlock:block];
    } else {
        __block BOOL passedPriorityKey = NO;
        [self enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
            if (!passedPriorityKey && [FUtilities compareKey:key toKey:@".priority"] == NSOrderedDescending) {
                passedPriorityKey = YES;
                BOOL stopAfterPriority = NO;
                block(@".priority", [self getPriority], &stopAfterPriority);
                if (stopAfterPriority) return;
            }
            block(key, node, stop);
        }];
    }
}

- (void) enumerateChildrenUsingBlock:(void (^)(NSString *, id<FNode>, BOOL *))block
{
    [self.children enumerateKeysAndObjectsUsingBlock:block];
}

- (void) enumerateChildrenReverse:(BOOL)reverse usingBlock:(void (^)(NSString *, id<FNode>, BOOL *))block
{
    [self.children enumerateKeysAndObjectsReverse:reverse usingBlock:block];
}

- (NSEnumerator *)childEnumerator
{
    return [[FTransformedEnumerator alloc] initWithEnumerator:self.children.keyEnumerator andTransform:^id(NSString *key) {
        return [FNamedNode nodeWithName:key node:[self getImmediateChild:key]];
    }];
}

- (NSString *) predecessorChildKey:(NSString *)childKey
{
    return [self.children getPredecessorKey:childKey];
}

#pragma mark -
#pragma mark FChildrenNode specific methods

- (id) childrenGetter:(id)key {
    return [self.children objectForKey:key];
}

- (FNamedNode *)firstChild
{
    NSString *childKey = self.children.minKey;
    if (childKey) {
        return [[FNamedNode alloc] initWithName:childKey andNode:[self getImmediateChild:childKey]];
    } else {
        return nil;
    }
}

- (FNamedNode *)lastChild
{
    NSString *childKey = self.children.maxKey;
    if (childKey) {
        return [[FNamedNode alloc] initWithName:childKey andNode:[self getImmediateChild:childKey]];
    } else {
        return nil;
    }
}

@end
