Implementation of Secret Santa sort

SecretSantaSort.swift

/*
Small program written to automate the sorting of Secret Santas as initially brought to my attention by Brent Simmons (http://inessential.com/2015/09/25/a_secret_santa_solution).
*/

import Foundation

let DEBUG = false

class Person: Equatable {
	var first: String
	var last: String
	var email: String
	var match: Person?
	var matched = false

	init(first: String, last: String, email: String, match: Person?) {
		self.first = first
		self.last = last
		self.email = email
		self.match = match
	}

	func canBeSantaOf(p: Person) -> Bool {
		return self.match == nil && self.last != p.last && !p.matched
	}
}

func ==(lhs: Person, rhs: Person) -> Bool {
	return lhs.first == rhs.first && lhs.last == rhs.last
}

var people = [Person]()

let standardInput = NSFileHandle.fileHandleWithStandardInput()
let input = standardInput.availableData

let str = NSString(data: input, encoding: NSUTF8StringEncoding) as! String
let linesArr = str.characters.split{$0 == "\n"}.map(String.init)
for line in linesArr {
	let details = line.characters.split{$0 == " "}.map(String.init)
	let p = Person(first: details[0], last: details[1], email: details[2], match: nil)
	people.append(p)
}

var validInput = true

if people.count > 1 {
	var currIdx = 0
	var pos = 1
	var curr = people[currIdx]
	var possible = people[pos]

	// Effectively we're treating our array of people as a circular list
	// that we navigate "top" to "bottom" until we can find a valid match
	// or until we run back into ourselves at which point we exit with
	// no match. This no match will then be confirmed by our validation
	// at the end of the program.
	while curr.match == nil && curr != possible {
		if DEBUG {
			print("curr: \(curr.first)")
			print("possible: \(possible.first)")
			print("pos: \(pos)")
			print("currIdx: \(currIdx)")
			print("*****")
		}

		if curr.canBeSantaOf(possible) {
			if DEBUG {
				print("Matching \(curr.first) with \(possible.first)")
			}
			curr.match = possible
			possible.matched = true

			currIdx++
			if currIdx >= people.count {
				currIdx = 0
			}
			curr = people[currIdx]
			pos = currIdx + 1

			if pos >= people.count {
				pos = 0
			}
			possible = people[pos]
		} else {
			pos++
			if pos >= people.count {
				pos = 0
			}
			possible = people[pos]
		}
	}
} else {
	validInput = false
}

// Finally, validate our results by doing a once-over on the array of people
for p in people {
	if p.match == nil || p.matched == false {
		validInput = false
	}
}

print("************* RESULTS **************")

if !validInput {
	print("Invalid input according to rules of Secret Santa matching")
} else {
	for p in people {
		print("\(p.first) \(p.last) matched \(p.match!.first) \(p.match!.last)")
	}
}