import SwiftUI
import UniformTypeIdentifiers
import CoreData

struct FuelLogImporterView: View {
    @Environment(\.managedObjectContext) private var viewContext
    @Environment(\.dismiss) var dismiss
    
    // Pass in the selected vehicle from FuelLogListView.
    var selectedVehicle: Vehicle?
    
    @State private var isFileImporterPresented = false
    @State private var importError: String? = nil
    
    var body: some View {
        VStack(spacing: 20) {
            Text("Import Fuel Logs from CSV")
                .font(.headline)
            Button("Select CSV File") {
                isFileImporterPresented = true
            }
            .padding()
            .background(Color.blue)
            .foregroundColor(.white)
            .cornerRadius(8)
            
            if let error = importError {
                Text("Error: \(error)")
                    .foregroundColor(.red)
            }
        }
        .fileImporter(
            isPresented: $isFileImporterPresented,
            allowedContentTypes: [UTType.commaSeparatedText],
            allowsMultipleSelection: false
        ) { result in
            switch result {
            case .success(let urls):
                if let url = urls.first {
                    // Request access to the file URL.
                    guard url.startAccessingSecurityScopedResource() else {
                        importError = "Permission error: Unable to access the selected file."
                        return
                    }
                    defer { url.stopAccessingSecurityScopedResource() }
                    importCSV(from: url)
                }
            case .failure(let error):
                importError = error.localizedDescription
            }
        }
        .navigationTitle("Import Fuel Logs")
    }
    
    private func importCSV(from url: URL) {
        do {
            let data = try Data(contentsOf: url)
            guard let csvString = String(data: data, encoding: .utf8) else {
                importError = "Could not decode file."
                return
            }
            // Assume the first line is a header.
            let lines = csvString.components(separatedBy: "\n").filter { !$0.isEmpty }
            guard lines.count > 1 else {
                importError = "CSV file appears empty."
                return
            }
            // For this example, assume the CSV columns are:
            // date,odometer,fuelVolume,cost,locationCoordinates,locationName,octane,pricePerGalon,fullTank
            let header = lines[0].components(separatedBy: ",")
            for line in lines.dropFirst() {
                let fields = line.components(separatedBy: ",")
                if fields.count < header.count {
                    print("Skipping row: \(line) – not enough fields (found \(fields.count), expected \(header.count))")
                    continue
                }
                
                // Trim whitespace for each field
                let dateStr = fields[0].trimmingCharacters(in: .whitespacesAndNewlines)
                let odometerStr = fields[1].trimmingCharacters(in: .whitespacesAndNewlines)
                let fuelVolumeStr = fields[2].trimmingCharacters(in: .whitespacesAndNewlines)
                let costStr = fields[3].trimmingCharacters(in: .whitespacesAndNewlines)
                let locationCoordinates = fields[4].trimmingCharacters(in: .whitespacesAndNewlines)
                let locationName = fields[5].trimmingCharacters(in: .whitespacesAndNewlines)
                let octaneStr = fields[6].trimmingCharacters(in: .whitespacesAndNewlines)
                let pricePerGalonStr = fields[7].trimmingCharacters(in: .whitespacesAndNewlines)
                let fullTankStr = fields[8].trimmingCharacters(in: .whitespacesAndNewlines)
                
                // Debug prints for each field
                print("Row: \(line)")
                print("Date: \(dateStr), Odometer: \(odometerStr), Fuel Volume: \(fuelVolumeStr), Cost: \(costStr), Octane: \(octaneStr), Price/Gal: \(pricePerGalonStr), FullTank: \(fullTankStr)")
                
                // Setup date formatter – adjust format as needed.
                var parsedDate: Date?
                let formats = ["M/d/yyyy", "yyyy-MM-dd HH:mm"]
                for format in formats {
                    let formatter = DateFormatter()
                    formatter.dateFormat = format
                    formatter.locale = Locale(identifier: "en_US_POSIX")
                    if let date = formatter.date(from: dateStr) {
                        parsedDate = date
                        break
                    }
                }
                guard let date = parsedDate else {
                    print("Skipping row – invalid date: \(dateStr)")
                    continue
                }
                
                guard let odometer = Double(odometerStr) else {
                    print("Skipping row – invalid odometer: \(odometerStr)")
                    continue
                }
                
                guard let fuelVolume = Double(fuelVolumeStr) else {
                    print("Skipping row – invalid fuel volume: \(fuelVolumeStr)")
                    continue
                }
                
                guard let cost = Double(costStr) else {
                    print("Skipping row – invalid cost: \(costStr)")
                    continue
                }
                
                guard let octane = Int16(octaneStr) else {
                    print("Skipping row – invalid octane: \(octaneStr)")
                    continue
                }
                
                guard let pricePerGalon = Double(pricePerGalonStr) else {
                    print("Skipping row – invalid price per gallon: \(pricePerGalonStr)")
                    continue
                }
                
                // If all conversions succeed, create the fuel log.
                let fullTank = (fullTankStr.lowercased() == "true" || fullTankStr == "1")
                
                let newLog = FuelLog(context: viewContext)
                newLog.id = UUID()
                newLog.date = date
                newLog.odometer = odometer
                newLog.fuelVolume = fuelVolume
                newLog.cost = cost
                newLog.locationCoordinates = locationCoordinates
                newLog.locationName = locationName
                newLog.octane = octane
                newLog.pricePerGalon = pricePerGalon
                newLog.fullTank = fullTank
                
                // Optionally assign vehicle if needed.
                print("Assigning vehicle: \(selectedVehicle?.make ?? "none")")
                newLog.vehicle = selectedVehicle
                
                print("Imported row successfully.")
            }
            try viewContext.save()
            dismiss()
        } catch {
            importError = error.localizedDescription
        }
    }
}

struct FuelLogImporterView_Previews: PreviewProvider {
    static var previews: some View {
        FuelLogImporterView(selectedVehicle: nil)
    }
}