Merge pull request #3 from michaelibrd/feature/candle-support

Adding support for candles (ohlc)

Author: michaelibrd

Sources/CoinGecko/Models/Candle.swift

@@ -0,0 +1,34 @@
+//
+//  Candle.swift
+//  
+//
+//  Created by stringcode on 05/04/2021.
+//
+
+import Foundation
+
+public typealias CandleList = [Candle]
+
+public struct Candle: Codable {
+    public let date: Date
+    public let open: Double
+    public let high: Double
+    public let low: Double
+    public let close: Double
+
+    public init(arrayData: [Double]) {
+        date = Date(timeIntervalSince1970: Double(arrayData[0]) / 1000)
+        open = arrayData[1]
+        high = arrayData[2]
+        low = arrayData[3]
+        close = arrayData[4]
+    }
+    
+    public init(date: Date, open: Double, high: Double, low: Double, close: Double) {
+        self.date = date
+        self.open = open
+        self.high = high
+        self.low = low
+        self.close = close
+    }
+}

Sources/CoinGecko/Resources.swift

@@ -15,7 +15,8 @@ public enum Endpoint: String {
 
     case coinsList = "/coins/list"
     case coinsMarketChart = "/coins/%@/market_chart"
-    case coin = "/coins/%@"
+    case coin = "/coins/%@" 
+    case ohlc = "/coins/%@/ohlc"
 }
 
 public enum Resources {}
@@ -81,4 +82,23 @@ extension Resources {
                       URLQueryItem(name: "days", value: "\(days)")]
         return Resource(.coinsMarketChart, method: .GET, pathParam: currencyId, params: params, completion: callback)
     }
+    
+    // Coin Gecko API returns candles of diffrent duration based on `days` parameter
+    // ```
+    //    1 - 2 days: 30 minutes
+    //    3 - 30 days: 4 hours
+    //    31 and before: 4 days
+    // ```
+    public static func candles<CandleList>(currencyId: String, vs: String, days: Int, callback: @escaping Callback<CandleList>) -> Resource<CandleList> {
+        let params = [URLQueryItem(name: "vs_currency", value: vs),
+                      URLQueryItem(name: "days", value: "\(days)")]
+        
+        let parse: (Data) -> CandleList = { data in
+            let decoder = JSONDecoder()
+            let arrayData = try? decoder.decode([[Double]].self, from: data)
+            return (arrayData ?? []).map { Candle(arrayData: $0) } as! CandleList
+        }
+                
+        return Resource(.ohlc, method: .GET, pathParam: currencyId, params: params, parse: parse, completion: callback)
+    }
 }

Tests/CoinGeckoTests/CandleTest.swift

@@ -0,0 +1,25 @@
+import XCTest
+@testable import CoinGecko
+
+final class CandleTests: XCTestCase {
+
+    private let client = CoinGeckoClient()
+
+    func testCandles() {
+        let exp = XCTestExpectation()
+        let id = "bitcoin"
+        let vs = "usd"
+        let candles = Resources.candles(currencyId: id, vs: vs, days: 180) { (result: Result<CandleList, CoinGeckoError>) in
+            switch result {
+            case let .success(candleList):
+                XCTAssertTrue(candleList.count > 44 && candleList.count < 49,
+                              "Unexpected candle count")
+            case let .failure(error):
+                XCTFail(error.localizedDescription)
+            }
+            exp.fulfill()
+        }
+        client.load(candles)
+        wait(for: [exp], timeout: 10.0)
+    }
+}