import SwiftUI
import Combine
import UniformTypeIdentifiers

class NotepadDocument: ObservableObject {
    @Published var text: String = ""
    @Published var currentFileURL: URL? = nil
    @Published var encoding: String.Encoding = .utf8

    func save(isSaveAs: Bool = false) {
        if isSaveAs || currentFileURL == nil {
            let panel = NSSavePanel()
            panel.allowedContentTypes = [.plainText]
            if panel.runModal() == .OK { currentFileURL = panel.url } else { return }
        }
        
        guard let url = currentFileURL else { return }
        do {
            try text.write(to: url, atomically: true, encoding: encoding)
        } catch {
            DispatchQueue.main.async {
                let alert = NSAlert()
                alert.messageText = "儲存失敗"
                alert.informativeText = error.localizedDescription
                alert.runModal()
            }
        }
    }

    func open() {
        let panel = NSOpenPanel()
        panel.allowedContentTypes = [.plainText]
        if panel.runModal() == .OK, let url = panel.url {
            do {
                if let content = try? String(contentsOf: url, encoding: .utf8) {
                    self.text = content
                    self.encoding = .utf8
                } else {
                    self.text = try String(contentsOf: url, encoding: .windowsCP1252)
                    self.encoding = .windowsCP1252
                }
                self.currentFileURL = url
            } catch { print("讀取失敗") }
        }
    }
}

struct ContentView: View {
    @ObservedObject var doc: NotepadDocument
    @State private var fontSize: CGFloat = 16
    @State private var currentTheme: ColorScheme? = .dark

    var body: some View {
        VStack(spacing: 0) {
            TextEditor(text: $doc.text)
                .font(.system(size: fontSize))
                .scrollContentBackground(.hidden)
                .background(currentTheme == .dark ? Color.black : Color.white)
                .padding(5)
            
            Divider()
            
            HStack {
                Text(doc.currentFileURL?.lastPathComponent ?? "新文件")
                Spacer()
                Text("縮放: \(Int((fontSize/16)*100))%")
            }
            .padding(.horizontal, 10)
            .font(.system(size: 11))
            .frame(height: 22)
            .background(Color.secondary.opacity(0.1))
        }
        .preferredColorScheme(currentTheme)
        .frame(minWidth: 800, minHeight: 600)
        .onAppear {
            NSEvent.addLocalMonitorForEvents(matching: .keyDown) { event in
                if event.modifierFlags.contains(.command) {
                    switch event.characters {
                    case "+", "=": fontSize += 2; return nil
                    case "-": fontSize = max(6, fontSize - 2); return nil
                    case "0": fontSize = 16; return nil
                    default: break
                    }
                }
                return event
            }
        }
    }
}