import SwiftUI

struct MessageListView: View {
	private let messageComposer = "MESSAGE_COMPOSER_ID"
	
	@Dependency private var database: Database
	@Dependency private var messagesLoader: MessagesLoading
	@Dependency private var messageSender: MessageSending
	
	private let formatter: RoomFormatter
	private let server: Server
	private let room: Room
	
	@State private var lastOpen: Date?
	
	@Environment(\.scenePhase) private var scenePhase
	
	@FetchRequest<Message> private var messages: FetchedResults<Message>
	
	init(room: Room, server: Server) {
		self.formatter = RoomFormatter(room: room, server: server)
		self.room = room
		self.server = server
		_messages = FetchRequest(fetchRequest: room.messagesRequest, animation: .none)
		_lastOpen = State(wrappedValue: room.updatedSince)
	}
	
	var body: some View {
		ChatScrollView {
			VStack(alignment: .leading, spacing: 8) {
				if room.hasMoreMessages {
					Button("Load More...") {
						guard let oldestMessage = room.firstMessage?.ts else { return }
						
						messagesLoader.loadMore(from: oldestMessage)
					}
				}
				
				ForEach(messages.indices, id: \.self) { index in
					let message = messages[index]
					let previousMessage = messages.indices.contains(index - 1) ? messages[index - 1] : nil
					
					MessageView(
						viewModel: .init(
							message: message,
							previousMessage: previousMessage,
							server: server,
							lastOpen: lastOpen
						)
					) { action in
						switch action {
						case .resend(let id, let msg):
							messageSender.resendMessage(messageID: id, msg: msg, in: room)
							
							lastOpen = nil
						case .delete(let message):
							database.remove(message)
						}
					}
				}
				
				MessageComposerView(room: room) {
					messageSender.sendMessage($0, in: room)
					
					lastOpen = nil
				}
				.id(messageComposer)
			}
		}
		.padding([.leading, .trailing])
		.navigationTitle(formatter.title ?? "")
		.navigationBarTitleDisplayMode(.inline)
		.onAppear {
			guard let roomID = room.id else { return }
			
			messagesLoader.start(on: roomID)
		}
		.onDisappear {
			messagesLoader.stop()
		}
		.onChange(of: scenePhase) { phase in
			switch phase {
			case .active:
				guard let roomID = room.id else { return }
				
				messagesLoader.start(on: roomID)
			case .background, .inactive:
				messagesLoader.stop()
			@unknown default:
				break
			}
		}
	}
}