//
//  MarketAPI.swift
//
//  Created by Marcos Rodriguez on 11/2/19.

//

import Foundation

var numberFormatter: NumberFormatter {
  let formatter = NumberFormatter()
  formatter.numberStyle = .decimal
  formatter.maximumFractionDigits = 0
  formatter.locale = Locale.current
  return formatter
}

class MarketAPI {
  
  private static func buildURLString(source: String, endPointKey: String) -> String {
       switch source {
       case "Yadio":
           return "https://api.yadio.io/json/\(endPointKey)"
       case "YadioConvert":
           return "https://api.yadio.io/convert/1/BTC/\(endPointKey)"
       case "Exir":
           return "https://api.exir.io/v1/ticker?symbol=btc-irt"
       case "wazirx":
           return "https://api.wazirx.com/api/v2/tickers/btcinr"
       case "Bitstamp":
           return "https://www.bitstamp.net/api/v2/ticker/btc\(endPointKey.lowercased())"
       case "Coinbase":
           return "https://api.coinbase.com/v2/prices/BTC-\(endPointKey.uppercased())/buy"
       case "CoinGecko":
           return "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=\(endPointKey.lowercased())"
       case "BNR":
           return "https://www.bnr.ro/nbrfxrates.xml"
       case "Kraken":
           return "https://api.kraken.com/0/public/Ticker?pair=XXBTZ\(endPointKey.uppercased())"
       default:
           return "https://api.coindesk.com/v1/bpi/currentprice/\(endPointKey).json"
       }
   }
  
  private static func handleDefaultData(data: Data, source: String, endPointKey: String, completion: @escaping ((WidgetDataStore?, Error?) -> Void)) {
          guard let json = (try? JSONSerialization.jsonObject(with: data, options: [])) as? Dictionary<String, Any> else {
              completion(nil, CurrencyError(errorDescription: "JSON parsing error."))
              return
          }

          parseJSONBasedOnSource(json: json, source: source, endPointKey: endPointKey, completion: completion)
    }
  
  private static func parseJSONBasedOnSource(json: Dictionary<String, Any>, source: String, endPointKey: String, completion: @escaping ((WidgetDataStore?, Error?) -> Void)) {
      var latestRateDataStore: WidgetDataStore?
      
      switch source {
      case "Yadio":
          if let rateDict = json[endPointKey] as? [String: Any],
             let rateDouble = rateDict["price"] as? Double,
             let lastUpdated = rateDict["timestamp"] as? Int {
              let unix = Double(lastUpdated / 1_000)
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date(timeIntervalSince1970: unix))
              latestRateDataStore = WidgetDataStore(rate: String(rateDouble), lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }
      case "YadioConvert":
               guard let rateDouble = json["rate"] as? Double,
                     let lastUpdated = json["timestamp"] as? Int
               else { break }
               let unix = Double(lastUpdated / 1_000)
               let lastUpdatedString = ISO8601DateFormatter().string(from: Date(timeIntervalSince1970: unix))
               latestRateDataStore = WidgetDataStore(rate: String(rateDouble), lastUpdate: lastUpdatedString, rateDouble: rateDouble)
        completion(latestRateDataStore, nil)
      case "CoinGecko":
          if let bitcoinDict = json["bitcoin"] as? [String: Any],
             let rateDouble = bitcoinDict[endPointKey.lowercased()] as? Double {
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
              latestRateDataStore = WidgetDataStore(rate: String(rateDouble), lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }
          
      case "Exir":
          if let rateDouble = json["last"] as? Double {
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
              latestRateDataStore = WidgetDataStore(rate: String(rateDouble), lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }
          
      case "Bitstamp":
          if let rateString = json["last"] as? String, let rateDouble = Double(rateString) {
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
              latestRateDataStore = WidgetDataStore(rate: rateString, lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }
          
      case "wazirx":
          if let tickerDict = json["ticker"] as? [String: Any],
             let rateString = tickerDict["buy"] as? String,
             let rateDouble = Double(rateString) {
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
              latestRateDataStore = WidgetDataStore(rate: rateString, lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }

      case "Coinbase":
          if let data = json["data"] as? [String: Any],
             let rateString = data["amount"] as? String,
             let rateDouble = Double(rateString) {
              let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
              latestRateDataStore = WidgetDataStore(rate: rateString, lastUpdate: lastUpdatedString, rateDouble: rateDouble)
              completion(latestRateDataStore, nil)
          } else {
              completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
          }

      case "BNR":
          completion(nil, CurrencyError(errorDescription: "BNR data source is not yet implemented"))
          
      case "Kraken":
           if let result = json["result"] as? [String: Any],
              let tickerData = result["XXBTZ\(endPointKey.uppercased())"] as? [String: Any],
              let c = tickerData["c"] as? [String],
              let rateString = c.first,
              let rateDouble = Double(rateString) {
               let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
               latestRateDataStore = WidgetDataStore(rate: rateString, lastUpdate: lastUpdatedString, rateDouble: rateDouble)
               completion(latestRateDataStore, nil)
           } else {
               if let errorMessage = json["error"] as? [String] {
                   completion(nil, CurrencyError(errorDescription: "Kraken API error: \(errorMessage.joined(separator: ", "))"))
               } else {
                   completion(nil, CurrencyError(errorDescription: "Data formatting error for source: \(source)"))
               }
           }


      default:
          completion(nil, CurrencyError(errorDescription: "Unsupported data source \(source)"))
      }
  }
  
  private static func handleBNRData(data: Data, completion: @escaping ((WidgetDataStore?, Error?) -> Void)) {
      let parser = XMLParser(data: data)
      let delegate = BNRXMLParserDelegate()
      parser.delegate = delegate
      if parser.parse(), let usdToRonRate = delegate.usdRate {
          let coinGeckoUrl = URL(string: "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd")!
          URLSession.shared.dataTask(with: coinGeckoUrl) { data, _, error in
              guard let data = data, error == nil else {
                  completion(nil, error ?? CurrencyError())
                  return
              }

              do {
                  if let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any],
                     let bitcoinDict = json["bitcoin"] as? [String: Double],
                     let btcToUsdRate = bitcoinDict["usd"] {
                      let btcToRonRate = btcToUsdRate * usdToRonRate
                      let lastUpdatedString = ISO8601DateFormatter().string(from: Date())
                      let latestRateDataStore = WidgetDataStore(rate: String(btcToRonRate), lastUpdate: lastUpdatedString, rateDouble: btcToRonRate)
                      completion(latestRateDataStore, nil)
                  } else {
                      completion(nil, CurrencyError())
                  }
              } catch {
                  completion(nil, error)
              }
          }.resume()
      } else {
          completion(nil, CurrencyError(errorDescription: "XML parsing error."))
      }
  }
  
  static func fetchPrice(currency: String, completion: @escaping ((WidgetDataStore?, Error?) -> Void)) {
      let currencyToFiatUnit = fiatUnit(currency: currency)
      guard let source = currencyToFiatUnit?.source, let endPointKey = currencyToFiatUnit?.endPointKey else {
          completion(nil, CurrencyError(errorDescription: "Invalid currency unit or endpoint."))
          return
      }

      let urlString = buildURLString(source: source, endPointKey: endPointKey)
      guard let url = URL(string: urlString) else {
          completion(nil, CurrencyError(errorDescription: "Invalid URL."))
          return
      }

      fetchData(url: url, source: source, endPointKey: endPointKey, completion: completion)
  }

  private static func fetchData(url: URL, source: String, endPointKey: String, retries: Int = 3, completion: @escaping ((WidgetDataStore?, Error?) -> Void)) {
      URLSession.shared.dataTask(with: url) { data, response, error in
          if let error = error {
              if retries > 0 {
                  fetchData(url: url, source: source, endPointKey: endPointKey, retries: retries - 1, completion: completion)
              } else {
                  completion(nil, error)
              }
              return
          }

          guard let data = data else {
              if retries > 0 {
                  fetchData(url: url, source: source, endPointKey: endPointKey, retries: retries - 1, completion: completion)
              } else {
                  completion(nil, CurrencyError(errorDescription: "Data not found."))
              }
              return
          }

          if source == "BNR" {
              handleBNRData(data: data, completion: completion)
          } else {
              handleDefaultData(data: data, source: source, endPointKey: endPointKey, completion: completion)
          }
      }.resume()
  }
  
}