Restaurant.swift

import Foundation
import Decodable

struct Restaurant {
    enum Meal: String {
        case breakfast, lunch, dinner
    }

    enum DecodingError: Error {
        case missing(String)
        case invalid(String, Any)
    }

    fileprivate static var dateFormatter: ISO8601DateFormatter = {
        let dateFormatter = ISO8601DateFormatter()
        dateFormatter.formatOptions = [.withInternetDateTime]
        return dateFormatter
    }()

    static let mockData: [String: Any] = [
        "name": "Mock Restaurant",
        "coordinates": [
            "lat": -33.8684299,
            "lng": 151.19378410000002
        ],
        "meals": [
            "breakfast",
            "lunch",
            "dinner"
        ],
        "opening": "1970-01-01T08:00:00Z",
        "closing": "1970-01-01T22:00:00Z"
    ]

    let name: String
    let location: (latitude: Double, longitude: Double)
    let meals: Set<Meal>
    let openingTime: Date
    let closingTime: Date

}

// Vanilla decoding (0.9s for 10k records)
extension Restaurant {
    init(json: [String : Any]) throws {
        guard let name = json["name"] as? String else {
            throw DecodingError.missing("name")
        }

        guard let coordinatesJSON = json["coordinates"] as? [String: Double],
            let latitude = coordinatesJSON["lat"],
            let longitude = coordinatesJSON["lng"] else {
                throw DecodingError.missing("coordinates")
        }

        guard let mealsJSON = json["meals"] as? [String] else {
            throw DecodingError.missing("meals")
        }

        guard let openingTimeString = json["opening"] as? String else {
            throw DecodingError.missing("opening")
        }

        guard let closingTimeString = json["closing"] as? String else {
            throw DecodingError.missing("closing")
        }

        guard let openingTime = Restaurant.dateFormatter.date(from: openingTimeString) else {
            throw DecodingError.invalid("opening", openingTimeString)
        }

        guard let closingTime = Restaurant.dateFormatter.date(from: closingTimeString) else {
            throw DecodingError.invalid("closing", closingTimeString)
        }

        var meals: Set<Meal> = []
        for string in mealsJSON {
            guard let meal = Meal(rawValue: string) else {
                throw DecodingError.invalid("meals", string)
            }
            
            meals.insert(meal)
        }
        
        self.name = name
        self.location = (latitude, longitude)
        self.meals = meals
        self.openingTime = openingTime
        self.closingTime = closingTime
    }
}

// Decoding with Decodable (1.2s for 10k records)
extension Restaurant: Decodable {
    private static func time(_ value: String, name: String) throws -> Date {
        guard let date = dateFormatter.date(from: value) else {
            throw DecodingError.invalid(name, value)
        }
        return date
    }

    static func decode(_ json: Any) throws -> Restaurant {
        let meals = try Array.decode(json => "meals")
            .flatMap(Meal.init)

        return try Restaurant(name: json => "name",
                              location: (json => "coordinates" => "lat", json => "coordinates"  => "lng"),
                              meals: Set(meals),
                              openingTime: time(json => "opening", name: "opening"),
                              closingTime: time(json => "closing", name: "closing"))
    }
}