// This is free software: you can redistribute and/or modify it
// under the terms of the GNU General Public License 3.0
// as published by the Free Software Foundation https://fsf.org

import Combine
import SwiftUI

public struct ContentView: View {
    @ObservedObject private var satsViewModel = SatsViewModel()

    @State private var priceSource: PriceSource

    private let dateFormatter: DateFormatter

    private let priceFetcherDelegator: PriceFetcherDelegator

    init(_ priceSource: PriceSource) {
        dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .short
        dateFormatter.timeStyle = .short

        self.priceSource = priceSource
        priceFetcherDelegator = PriceFetcherDelegator(priceSource)
    }

    @MainActor
    func updatePrice() async {
        do {
            guard let price = try await priceFetcherDelegator.convertBTC(toCurrency: satsViewModel.selectedCurrency) else {
                satsViewModel.btcToCurrencyString = ""
                return
            }

            satsViewModel.btcToCurrencyString = "\(price)"
        } catch {
            satsViewModel.btcToCurrencyString = ""
        }
        satsViewModel.lastUpdated = Date.now
    }

    public var body: some View {
        NavigationStack {
            Form {
                Section {
                    Picker("Price Source", selection: $priceSource) {
                        ForEach(PriceSource.allCases, id: \.self) {
                            Text($0.description)
                        }
                    }

                    Picker("Currency", selection: $satsViewModel.selectedCurrency) {
                        ForEach(satsViewModel.currencies, id: \.self) {
                            if let localizedCurrency = Locale.current.localizedString(forCurrencyCode: $0.identifier) {
                                Text("\($0.identifier) - \(localizedCurrency)")
                            } else {
                                Text($0.identifier)
                            }
                        }
                    }
#if os(iOS) || SKIP
                    .pickerStyle(.navigationLink)
#endif

                    HStack {
                        TextField("", text: $satsViewModel.btcToCurrencyString)
                            .disabled(priceSource != .manual)
#if os(iOS) || SKIP
                            .keyboardType(.decimalPad)
#endif
                        if priceSource != .manual {
                            Button(action: {
                                Task {
                                    await updatePrice()
                                }
                            }) {
                                Image(systemName: "arrow.clockwise.circle")
                            }
                        }
                    }
                } header: {
                    Text("1 BTC to \(satsViewModel.selectedCurrency.identifier)")
                } footer: {
                    if priceSource != .manual, let lastUpdated = satsViewModel.lastUpdated {
                        Text("Last updated: \(dateFormatter.string(from: lastUpdated))")
                    }
                }

                Section {
                    TextField("", text: $satsViewModel.satsString)
#if os(iOS) || SKIP
                        .keyboardType(.numberPad)
#endif
                } header: {
                    Text("Sats")
                } footer: {
                    if satsViewModel.exceedsMaximum {
                        Text("2100000000000000 sats is the maximum.")
                    }
                }

                Section {
                    TextField("", text: $satsViewModel.btcString)
#if os(iOS) || SKIP
                        .keyboardType(.decimalPad)
#endif
                } header: {
                    Text("BTC")
                } footer: {
                    if satsViewModel.exceedsMaximum {
                        Text("21000000 BTC is the maximum.")
                    }
                }

                Section {
                    TextField("", text: $satsViewModel.currencyValueString)
#if os(iOS) || SKIP
                        .keyboardType(.decimalPad)
#endif
                } header: {
                    Text(satsViewModel.selectedCurrency.identifier)
                }
            }
            .task {
                await updatePrice()
            }
            .onChange(of: satsViewModel.selectedCurrency) { newCurrency in
                satsViewModel.lastUpdated = nil
                Task {
                    await updatePrice()
                }
            }
            .onChange(of: priceSource) { newPriceSource in
                satsViewModel.lastUpdated = nil
                priceFetcherDelegator.priceSource = newPriceSource
                Task {
                    await updatePrice()
                }
            }
#if os(macOS)
            .formStyle(.grouped)
#endif
        }
    }
}

#Preview {
#if DEBUG
    ContentView(.fake)
#else
    ContentView(.coinbase)
#endif
}