//
//  FuelLogListView.swift
//  Gas Man
//
//  Created by Kameron Kenny on 3/17/25.
//


import SwiftUI
import CoreData

struct FuelLogListView: View {
    @Environment(\.managedObjectContext) private var viewContext
    @FetchRequest(
        sortDescriptors: [NSSortDescriptor(keyPath: \FuelLog.date, ascending: false)],
        animation: .default)
    private var fuelLogs: FetchedResults<FuelLog>
    
    @State private var showingAddFuelLog = false  // Controls sheet presentation
    
    var body: some View {
        NavigationView {
            List {
                ForEach(Array(fuelLogs.enumerated()), id: \.element) { index, log in
                    // Compute distance since the previous record:
                    let distance: Double? = {
                        if index < fuelLogs.count - 1 {
                            let previousLog = fuelLogs[index + 1]
                            let milesDriven = log.odometer - previousLog.odometer
                            return milesDriven > 0 ? milesDriven : nil
                        }
                        return nil
                    }()
                    
                    // Compute MPG (if possible)
                    let mpg: Double? = {
                        if index < fuelLogs.count - 1 {
                            let previousLog = fuelLogs[index + 1]
                            let milesDriven = log.odometer - previousLog.odometer
                            if log.fuelVolume > 0 && milesDriven > 0 {
                                return milesDriven / log.fuelVolume
                            }
                        }
                        return nil
                    }()
                    
                    NavigationLink(destination: FuelLogDetailView(fuelLog: log)) {
                        FuelLogSummaryView(log: log, mpg: mpg, distanceSincePrevious: distance)
                    }
                }
                .onDelete(perform: deleteFuelLogs)
            }
            .listStyle(InsetGroupedListStyle())
            .navigationTitle("Fuel Logs")
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        showingAddFuelLog = true  // Present AddFuelLogView
                    }) {
                        Label("Add Fuel Log", systemImage: "plus")
                    }
                }
                ToolbarItem(placement: .navigationBarLeading) {
                    EditButton()
                }
            }
            // Sheet presentation for AddFuelLogView
            .sheet(isPresented: $showingAddFuelLog) {
                AddFuelLogView().environment(\.managedObjectContext, viewContext)
            }
        }
    }
    
    private func deleteFuelLogs(offsets: IndexSet) {
        withAnimation {
            offsets.map { fuelLogs[$0] }.forEach(viewContext.delete)
            do {
                try viewContext.save()
            } catch {
                let nsError = error as NSError
                fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
            }
        }
    }
}