reports func must be more Swifty.

reports.swift

enum State {
  case Happy
  case Sad
}

struct Day {
  let name: String
  let state: State
}

struct Month {
  let name: String
  let days: [Day]
}

func swiftyReports(months: [Month]) -> (happy: Int, sad: Int, total: Int) {
  let flat = months
    .flatMap { $0.days }
    .map { $0.state }
  
  let sad = flat.filter { $0 == .Sad }.count
  let happy = flat.filter { $0 == .Happy }.count
  
  // happy + sad can be rewritten as `flat.count`
  return (happy, sad, happy + sad)
}

let months = [Month(name: "Month 1", days: [
  Day(name: "Day 1", state: .Happy),
  Day(name: "Day 2", state: .Happy),
  Day(name: "Day 3", state: .Sad)]),
              Month(name: "Month 2", days: [
                Day(name: "Day 1", state: .Happy),
                Day(name: "Day 2", state: .Sad),
                Day(name: "Day 3", state: .Happy),
                Day(name: "Day 4", state: .Happy)])]

let report = swiftyReports(months)

print("\(report.happy) happy days, \(report.sad) sad days, \(report.total) total")