import SwiftUI
import Charts

struct SalesData: Codable, Identifiable {
    let id = UUID()
    let month: String
    let revenue: Double
}

struct ContentView: View {
    @State private var salesData: [SalesData] = []
    
    var body: some View {
        Chart(salesData) { data in
            BarMark(
                x: .value("Month", data.month),
                y: .value("Revenue", data.revenue)
            )
        }
        .task {
            await fetchData()
        }
    }
    
    func fetchData() async {
        guard let url = URL(string: "https://api.example.com/sales") else { return }
        
        do {
            let (data, _) = try await URLSession.shared.data(from: url)
            let decodedData = try JSONDecoder().decode([SalesData].self, from: data)
            salesData = decodedData
        } catch {
            print("Error fetching data: \(error)")
        }
    }
}

import UIKit
import Charts

class ViewController: UIViewController {
    @IBOutlet weak var barChartView: BarChartView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        fetchChartData()
    }
    
    func fetchChartData() {
        guard let url = URL(string: "https://api.example.com/data") else { return }
        
        URLSession.shared.dataTask(with: url) { data, response, error in
            if let data = data {
                do {
                    let json = try JSONSerialization.jsonObject(with: data) as? [[String: Any]]
                    let entries = json?.compactMap { item -> BarChartDataEntry? in
                        guard let x = item["x"] as? Double,
                              let y = item["y"] as? Double else { return nil }
                        return BarChartDataEntry(x: x, y: y)
                    }
                    
                    DispatchQueue.main.async {
                        let dataSet = BarChartDataSet(entries: entries, label: "Data")
                        dataSet.colors = [.systemBlue]
                        self.barChartView.data = BarChartData(dataSet: dataSet)
                    }
                } catch {
                    print("JSON error: \(error.localizedDescription)")
                }
            }
        }.resume()
    }
}

// 确保在主线程更新
DispatchQueue.main.async {
    self.updateChart(with: data)
}

// 在Charts库中设置性能优化
chartView.dragEnabled = true
chartView.setScaleEnabled(true)
chartView.pinchZoomEnabled = true
chartView.maxVisibleCount = 100 // 限制可见数据点

struct APIResponse: Codable {
    let dataPoints: [DataPoint]
    
    struct DataPoint: Codable {
        let timestamp: String
        let value: Double
    }
}

// 解析时
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let response = try decoder.decode(APIResponse.self, from: data)