foray/Fetchers/ForayFetcher.swift


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//
//  ForayNetworkManager.swift
//  foray
//
//  Created by Nicholas Tay on 20/3/2022.
//

import Foundation

class ForayFetcher {
    var basicUsername: String? = nil
    var basicPassword: String? = nil
    
    // Reuse JSON decoder, allows for customisation of things like date decode if required
    var jsonDecoder: JSONDecoder = {
        let jd = JSONDecoder()
        // Defaults to year-month-date format
        jd.dateDecodingStrategy = .custom({ (decoder) -> Date in
            let container = try decoder.singleValueContainer()
            let dateStr = try container.decode(String.self)
            
            let dateFormat = DateFormatter()
            dateFormat.dateFormat = "yyyy-MM-dd"
            
            return dateFormat.date(from: dateStr)!
        })
        return jd
    }()
    
    func fetch<T: Decodable>(url: String,
                             receiver: @escaping (T) -> ()) {
        // Fetch on a background thread
        DispatchQueue.global(qos: .background).async {
            var request = URLRequest(url: URL(string: url)!)
            request.cachePolicy = .reloadRevalidatingCacheData // Needed otherwise default caching policy seems not to check properly
            
            // Basic auth if required
            if (self.basicUsername != nil && self.basicPassword != nil) {
                let authData = (self.basicUsername! + ":" + self.basicPassword!).data(using: .utf8)!.base64EncodedString()
                request.addValue("Basic \(authData)", forHTTPHeaderField: "Authorization")
            }

            URLSession.shared.dataTask(with: request, completionHandler: { data, response, error -> Void in
                let items = try! self.jsonDecoder.decode(T.self, from: data!)
                receiver(items)
            }).resume()
        }
    }
}