Add basic backend for showing words

WordAX/WordAX.swift

@@ -6,3 +6,62 @@
 //
 
 import Foundation
+
+struct WordAX {
+    struct Word: Identifiable {
+        var id: Int
+        var name: String
+        var description: String
+        var shown: Bool
+        var nextSpacedRepetitionMilestone: SpacedRepetitionMilestoneEnum?
+        var displayOn: Date?
+    }
+    enum FrequencyEnum: Int {
+        case Daily = 1
+        case Weekly = 7
+        case BiWeekly = 14
+        case Monthly = 30
+    }
+    
+    enum SpacedRepetitionMilestoneEnum: Int, CaseIterable {
+        case OneDay = 1
+        case OneWeek = 7
+        case TwoWeeks = 14
+        case OneMonth = 30
+        case TwoMonths = 60
+        case FiveMonths = 150
+        case OneYear = 365
+        
+        static var allCasesSorted: [SpacedRepetitionMilestoneEnum] {
+            allCases.sorted {$0.rawValue < $1.rawValue }
+        }
+    }
+    
+    struct Settings {
+        var frequency: FrequencyEnum = .Daily
+        var lastShownNew: Date?
+    }
+    
+    private mutating func setNextSpacedRepetitionMilestone(word: Word) {
+        if word.nextSpacedRepetitionMilestone != nil {
+            let current = SpacedRepetitionMilestoneEnum.allCasesSorted.firstIndex(of: word.nextSpacedRepetitionMilestone!) ?? SpacedRepetitionMilestoneEnum.allCases.count
+            let index = words.firstIndex(where:{$0.id == word.id}) ?? nil
+            if current + 1 < SpacedRepetitionMilestoneEnum.allCases.count && index != nil {
+                words[index!].nextSpacedRepetitionMilestone = SpacedRepetitionMilestoneEnum.allCasesSorted[current + 1]
+            } else if index != nil {
+                words[index!].nextSpacedRepetitionMilestone = nil
+            }
+        }
+    }
+    
+    var words: [Word] = []
+    var settings: Settings
+    
+    init() {
+        self.words = []
+        self.settings = Settings()
+        self.words.append(Word(id: 0, name: "Magnificent", description: "When something is awesome", shown: false))
+        self.words.append(Word(id: 1, name: "Mesmerising", description: "When something is beautiful", shown: false))
+    }
+    
+}

WordAX/WordAXModelView.swift

@@ -8,7 +8,62 @@
 import Foundation
 
 class WordAXModelView: ObservableObject {
+    @Published private var model: WordAX
+    typealias Word = WordAX.Word
     init() {
+        model = WordAX()
+    }
+    
+    public func getWordToDisplay() -> Word? {
+        let words = model.words
         
+        if words.count > 0 {
+            // if today is the date they're supposed to be shown
+            let displayToday = words.filter({ $0.displayOn != nil && $0.displayOn!.isToday()})
+            if  displayToday.count > 0 {
+                return displayToday.first!
+            }
+            
+            // first word ever shown
+            let shownWords = words.filter({ $0.shown })
+            if shownWords.count == 0 {
+                return words.first!
+            }
+            // if today is the day to show a new word
+            let settings = model.settings
+            if shownWords.count == 0 ||
+                settings.lastShownNew == nil ||
+                settings.lastShownNew!.addingTimeInterval(TimeInterval(settings.frequency.rawValue * 24 * 60 * 60)).isAfterToday() {
+                return words.first!
+            }
+        }
+        // otherwise show nothing
+        return nil
+    }
+}
+
+
+extension Date {
+    private func getOnlyDate(date: Date) -> DateComponents {
+        Calendar.current.dateComponents([.day, .month, .year], from: date)
+    }
+    func isSameAs(_ date: Date) -> Bool {
+        let selfDate = getOnlyDate(date: self)
+        let paramDate = getOnlyDate(date: date)
+        return selfDate.day == paramDate.day && selfDate.month == paramDate.month && selfDate.year == paramDate.year
+    }
+    
+    func isToday() -> Bool {
+        self.isSameAs(Date())
+    }
+    
+    func isAfter(_ date: Date) -> Bool {
+        let selfDate = getOnlyDate(date: self)
+        let paramDate = getOnlyDate(date: date)
+        return selfDate.year! > paramDate.year! || selfDate.month! > paramDate.month! || selfDate.day! > paramDate.day!
+    }
+    
+    func isAfterToday() -> Bool {
+        self.isAfter(Date())
     }
 }