JSONParsing

//
//  JSONParsing.swift
//  hplus-sports
//
//  Created by Muhammad Hassan on 9/27/17.
//  Copyright © 2017 Lynda.com. All rights reserved.
//

import Foundation

enum JSONParsingError: Error {
    case missingKey(key: String)
    case typeMismatch(key: String)
}

protocol JSONDecodable {
    init(_ decoder: JSONDecoder) throws
}

typealias JSONObject = [String: Any]

class JSONDecoder {
    let jsonObject: JSONObject
    static let defaultDataFormat = "dd/MM/yyyy HH:mm:ss"
    private lazy var dateFormatter = DateFormatter()
    
    init(_ jsonObject: JSONObject) {
        self.jsonObject = jsonObject
    }
    
    func value<T>(forKey key: String) throws -> T {
        guard let value = jsonObject[key] else {
            throw JSONParsingError.missingKey(key: key)
        }
        guard let finalValue = value as? T else {
            throw JSONParsingError.typeMismatch(key: key)
        }
        return finalValue
    }
    
    func value(forKey key: String, format: String = JSONDecoder.defaultDataFormat) throws -> Date {
        let dateValue: String = try value(forKey: "date")
        dateFormatter.dateFormat = format
        guard let returnValue = dateFormatter.date(from: dateValue) else {
            throw JSONParsingError.typeMismatch(key: key)
        }
        return returnValue
    }
}

func parse<T>(_ data: Data) throws -> [T] where T: JSONDecodable {
    let jsonObjects: [JSONObject] = try deserialize(data)
    return try jsonObjects.map(decode)
}

func deserialize(_ data: Data) throws -> [JSONObject] {
    let json = try JSONSerialization.jsonObject(with: data, options: [])
    guard let objects = json as? [JSONObject] else { return [] }
    return objects
}

func decode<T>(_ jsonObject: JSONObject) throws -> T where T: JSONDecodable {
    return try T.init(JSONDecoder(jsonObject))
}