tableModifications.swift

//
//  TableModifications.swift
//  mn_ios
//
//  Created by Alex Bosworth on 4/8/15.
//  Copyright (c) 2015 adylitica. All rights reserved.
//

import UIKit

/** Modifications to a table view
*/
struct TableModifications<T: Equatable where T: Hashable> {
    // MARK: - Init Properties
    
    let previousSections: [T]
    
    // MARK: - Mutable Properties
    
    private var _finalSections = [T]()

    var sectionsToInsert: Set<T> = Set()
    var sectionsToRemove: Set<T> = Set()
    var pathsToConfigure: Set<NSIndexPath> = Set()
    var pathsToInsert: Set<NSIndexPath> = Set()
    var pathsToMove: [(from: NSIndexPath, to: NSIndexPath)] = []
    var pathsToRemove: Set<NSIndexPath> = Set()
    
    // MARK: - Generated Properties
    
    var sectionsToInsertAsNSIndexSet: NSIndexSet {
        return _indexSetFromSections(sectionsToInsert, referencing: _finalSections)
    }
    
    var sectionsToRemoveAsNSIndexSet: NSIndexSet {
        return _indexSetFromSections(sectionsToRemove, referencing: previousSections)
    }
    
    // MARK: - Init
    
    init(previousSections: [T]) {
        self.previousSections = previousSections
    }
    
    // MARK: - UITableView Modifications
    
    /** Combine these modifications with another set of modifications
    */
    mutating func importModifications(modifications: TableModifications) {
        sectionsToInsert.unionInPlace(modifications.sectionsToInsert)
        sectionsToRemove.unionInPlace(modifications.sectionsToRemove)
        pathsToConfigure.unionInPlace(modifications.pathsToConfigure)
        pathsToInsert.unionInPlace(modifications.pathsToInsert)
        pathsToMove += modifications.pathsToMove
        pathsToRemove.unionInPlace(modifications.pathsToRemove)
    }
    
    /** Get an NSIndex set from an array of sections
    */
    private func _indexSetFromSections(sections: Set<T>, referencing: [T]) -> NSIndexSet {
        var set = NSMutableIndexSet()
        
        for sec in sections { if let s = find(referencing, sec) { set.addIndex(s) } }
        
        return set
    }
    
    /** Modify table sections and cells
    
        Note: be sure to call this inside of a beginupdates/endupdates block
    */
    mutating func makeModificationsInTableView(tableView: UITableView, finalSections: [T]) {
        _finalSections = finalSections
        
        tableView.deleteRowsAtIndexPaths(Array(pathsToRemove), withRowAnimation: .Automatic)
        tableView.deleteSections(sectionsToRemoveAsNSIndexSet, withRowAnimation: .Automatic)
        tableView.insertSections(sectionsToInsertAsNSIndexSet, withRowAnimation: .Automatic)
        tableView.insertRowsAtIndexPaths(Array(pathsToInsert), withRowAnimation: .Automatic)
        
        for path in pathsToMove { tableView.moveRowAtIndexPath(path.from, toIndexPath: path.to) }
        
        let cells = Array(pathsToConfigure).map { tableView.cellForRowAtIndexPath($0) as? Configurable }
        
        for c in cells { c?.configure() }
    }
}