//
//  EKAttributes+Precedence.swift
//  SwiftEntryKit
//
//  Created by Daniel Huri on 4/29/18.
//

import Foundation

fileprivate extension Int {
    var isValidDisplayPriority: Bool {
        return self >= EKAttributes.Precedence.Priority.minRawValue && self <= EKAttributes.Precedence.Priority.maxRawValue
    }
}

public extension EKAttributes {
    
    /**
     Describes the manner on which the entry is pushed and displayed.
     See the various values of more explanation.
     */
    enum Precedence {
        
        /**
         The display priority of the entry - Determines whether is can be overriden by other entries.
         Must be in range [0...1000]
         */
        public struct Priority: Hashable, Equatable, RawRepresentable, Comparable {
            public var rawValue: Int
            
            public var hashValue: Int {
                return rawValue
            }
            
            public init(_ rawValue: Int) {
                assert(rawValue.isValidDisplayPriority, "Display Priority must be in range [\(Priority.minRawValue)...\(Priority.maxRawValue)]")
                self.rawValue = rawValue
            }
            
            public init(rawValue: Int) {
                assert(rawValue.isValidDisplayPriority, "Display Priority must be in range [\(Priority.minRawValue)...\(Priority.maxRawValue)]")
                self.rawValue = rawValue
            }
            
            public static func == (lhs: Priority, rhs: Priority) -> Bool {
                return lhs.rawValue == rhs.rawValue
            }
            
            public static func < (lhs: Priority, rhs: Priority) -> Bool {
                return lhs.rawValue < rhs.rawValue
            }
        }
        
        /**
         Describes the queueing heoristic of entries.
         */
        public enum QueueingHeuristic {
            
            /** Determines the heuristic which the entry-queue is based on */
            public static var value = QueueingHeuristic.priority
            
            /** Chronological - FIFO */
            case chronological
            
            /** Ordered by priority */
            case priority
            
            /** Returns the caching heuristics mechanism that determines the priority in queue */
            var heuristic: EntryCachingHeuristic {
                switch self {
                case .chronological:
                    return EKEntryChronologicalQueue()
                case .priority:
                    return EKEntryPriorityQueue()
                }
            }
        }
        
        /**
         Describes an *overriding* behavior for a new entry.
         - In case no previous entry is currently presented, display the new entry.
         - In case there is an entry that is currently presented - override it using the new entry. Also optionally drop all previously enqueued entries.
         */
        case override(priority: Priority, dropEnqueuedEntries: Bool)
        
        /**
         Describes a FIFO behavior for an entry presentation.
         - In case no previous entry is currently presented, display the new entry.
         - In case there is an entry that is currently presented - enqueue the new entry, an present it just after the previous one is dismissed.
         */
        case enqueue(priority: Priority)
        
        var isEnqueue: Bool {
            switch self {
            case .enqueue:
                return true
            default:
                return false
            }
        }
        
        /** Setter / Getter for the display priority */
        public var priority: Priority {
            set {
                switch self {
                case .enqueue(priority: _):
                    self = .enqueue(priority: newValue)
                case .override(priority: _, dropEnqueuedEntries: let dropEnqueuedEntries):
                    self = .override(priority: newValue, dropEnqueuedEntries: dropEnqueuedEntries)
                }
            }
            get {
                switch self {
                case .enqueue(priority: let priority):
                    return priority
                case .override(priority: let priority, dropEnqueuedEntries: _):
                    return priority
                }
            }
        }
    }
}

/** High priority entries can be overriden by other equal or higher priority entries only.
 Entries are ignored as a higher priority entry is being displayed.
 High priority entry overrides any other entry including another equal priority one.
 You can you on of the values (.max, high, normal, low, min) and also set your own values. */
public extension EKAttributes.Precedence.Priority {
    static let maxRawValue = 1000
    static let highRawValue = 750
    static let normalRawValue = 500
    static let lowRawValue = 250
    static let minRawValue = 0

    /** Max - the highest possible priority of an entry. Can override only entries with *max* priority */
    static let max = EKAttributes.Precedence.Priority(rawValue: maxRawValue)
    static let high = EKAttributes.Precedence.Priority(rawValue: highRawValue)
    static let normal = EKAttributes.Precedence.Priority(rawValue: normalRawValue)
    static let low = EKAttributes.Precedence.Priority(rawValue: lowRawValue)
    static let min = EKAttributes.Precedence.Priority(rawValue: minRawValue)
}