BotanicalModel.swift

import Foundation
import UIKit

protocol BotanicalModelProtocol {
    func botanicalResultsRetrieved(_ results: [ResultsDetail])
}

enum BotanicalError: Error {
    case invalidURL
    case noDataAvailable
    case canNotProcessData
    
}

enum imageLoadingError: Error {
    case purelyNil(Error)
    case invalidData
}

struct BotanicalModel {
    
    var delegate: BotanicalModelProtocol?
    let imageCache = NSCache<NSURL, UIImage>()
    // get data
    func getBotanicalResults(completionHandler: @escaping (Result<[ResultsDetail], BotanicalError>) -> Void) {
//        let urlString = "https://data.taipei/opendata/datalist/apiAccess?scope=resourceAquire&rid=f18de02f-b6c9-47c0-8cda-50efad621c14"
        let urlString = "https://data.taipei/opendata/datalist/apiAccess?scope=resourceAquire&rid=f18de02f-b6c9-47c0-8cda-50efad621c14&limit=20&offset=0"
        
        guard let url = URL(string: urlString) else {
            completionHandler(.failure(.invalidURL))
            return
        }
        let decoder = JSONDecoder()
        URLSession.shared.dataTask(with: url) { data, response, error in
            guard let jsonData = data else {
                completionHandler(.failure(.noDataAvailable))
                return
            }
            do {
                let botanicalResponse = try decoder.decode(BotanicalMain.self, from: jsonData)
                let botanicalResults = botanicalResponse.result.results
                print("success getting results!")
                completionHandler(.success(botanicalResults))
            } catch {
                completionHandler(.failure(.canNotProcessData))
            }
        }.resume()
    }
    
    func loadmore(offset: Int, completionHandler: @escaping (Result<[ResultsDetail], BotanicalError>) -> Void) {
        let urlString = "https://data.taipei/opendata/datalist/apiAccess?scope=resourceAquire&rid=f18de02f-b6c9-47c0-8cda-50efad621c14&limit=20&offset=\(offset)"
        guard let url = URL(string: urlString) else {
            completionHandler(.failure(.invalidURL))
            return
        }
        let decoder = JSONDecoder()
        URLSession.shared.dataTask(with: url) { data, response, error in
            guard let jsonData = data else {
                completionHandler(.failure(.noDataAvailable))
                return
            }
            do {
                let botanicalResponse = try decoder.decode(BotanicalMain.self, from: jsonData)
                let botanicalResults = botanicalResponse.result.results
                print("success getting another 20 results!")
                completionHandler(.success(botanicalResults))
            } catch {
                completionHandler(.failure(.canNotProcessData))
            }
        }.resume()
    }
    // get image
    func getBotanicalImage(pagination: Bool = false, url: URL, completionHandler: @escaping (Result<UIImage, imageLoadingError>) -> Void) {
        if let image = imageCache.object(forKey: url as NSURL) {
            completionHandler(.success(image))
            return
        }
        URLSession.shared.dataTask(with: url) { data, response, error in
            if let error = error {
                completionHandler(.failure(.purelyNil(error)))
            }
            if let jsonData = data,
               let image = UIImage(data: jsonData) {
                imageCache.setObject(image, forKey: url as NSURL)
                completionHandler(.success(image))
            } else {
                completionHandler(.failure(.invalidData))
            }
        }.resume()
    }
}