import SwiftUI

struct SidebarView: View {
    @ObservedObject var state: AppState
    @State private var lastClickedID: UUID?

    private let dateFormatter: DateFormatter = {
        let f = DateFormatter()
        f.dateStyle = .short
        f.timeStyle = .short
        return f
    }()

    var body: some View {
        VStack(spacing: 0) {
            HStack {
                Text("Notes")
                    .font(.headline)
                    .foregroundColor(Color(ns: Theme.current.text))
                Spacer()
                Button(action: { state.newNote() }) {
                    Image(systemName: "plus")
                        .foregroundColor(Color(ns: Theme.current.text))
                }
                .buttonStyle(.plain)
                .help("New Note")
            }
            .padding(.horizontal, 12)
            .padding(.vertical, 8)

            Divider()

            if state.noteList.isEmpty {
                VStack {
                    Spacer()
                    Text("No notes yet")
                        .foregroundColor(Color(ns: Theme.current.overlay1))
                        .font(Font(Theme.sidebarFont as CTFont))
                    Spacer()
                }
            } else {
                ScrollView {
                    LazyVStack(spacing: 0) {
                        ForEach(Array(state.noteList.enumerated()), id: \.element.id) { index, note in
                            NoteRow(
                                note: note,
                                isSelected: state.selectedNoteIDs.contains(note.id),
                                isActive: note.id == state.currentNoteID,
                                dateFormatter: dateFormatter
                            )
                            .contentShape(Rectangle())
                            .onTapGesture(count: 2) {
                                state.openNote(note.id)
                            }
                            .onTapGesture(count: 1) {
                                handleClick(note: note, index: index)
                            }
                            .contextMenu {
                                if state.selectedNoteIDs.count > 1 && state.selectedNoteIDs.contains(note.id) {
                                    Button("Delete \(state.selectedNoteIDs.count) Notes") {
                                        state.deleteNotes(state.selectedNoteIDs)
                                        lastClickedID = nil
                                    }
                                } else {
                                    Button("Delete") { state.deleteNote(note.id) }
                                }
                            }
                        }
                    }
                }
                .onDeleteCommand {
                    guard !state.selectedNoteIDs.isEmpty else { return }
                    state.deleteNotes(state.selectedNoteIDs)
                    lastClickedID = nil
                }
            }
        }
        .background(Color(ns: Theme.current.base))
        .onAppear { state.refreshNoteList() }
    }

    private func handleClick(note: NoteInfo, index: Int) {
        let flags = NSEvent.modifierFlags
        if flags.contains(.command) {
            state.selectNote(note.id, extend: true)
            lastClickedID = note.id
        } else if flags.contains(.shift), let lastID = lastClickedID {
            if let lastIndex = state.noteList.firstIndex(where: { $0.id == lastID }) {
                let range = min(lastIndex, index)...max(lastIndex, index)
                var ids = Set<UUID>()
                for i in range {
                    ids.insert(state.noteList[i].id)
                }
                state.selectedNoteIDs = ids
            }
        } else {
            state.selectNote(note.id)
            lastClickedID = note.id
        }
    }
}

struct NoteRow: View {
    let note: NoteInfo
    let isSelected: Bool
    var isActive: Bool = false
    let dateFormatter: DateFormatter

    var body: some View {
        VStack(alignment: .leading, spacing: 2) {
            Text(note.title)
                .font(Font(isActive
                    ? NSFontManager.shared.convert(Theme.sidebarFont, toHaveTrait: .boldFontMask) as CTFont
                    : Theme.sidebarFont as CTFont))
                .foregroundColor(Color(ns: Theme.current.text))
                .lineLimit(1)
            Text(dateFormatter.string(from: note.lastModified))
                .font(Font(Theme.sidebarDateFont as CTFont))
                .foregroundColor(Color(ns: Theme.current.subtext0))
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(.vertical, 4)
        .padding(.horizontal, 12)
        .background(
            isActive
                ? Color(ns: Theme.current.surface1)
                : isSelected
                    ? Color(ns: Theme.current.surface0)
                    : Color.clear
        )
    }
}