import SwiftUI
import AppKit
import UniformTypeIdentifiers

struct PanelView: View {
    @ObservedObject var store: Store

    @State private var composer = ""
    @State private var search = ""
    @State private var showSearch = false
    @State private var showSectionSwitcher = false
    @State private var selection = Set<UUID>()
    @State private var copiedID: UUID?
    @State private var accessibilityGranted = AXIsProcessTrusted()

    private enum Field: Hashable { case composer, search }
    @FocusState private var focusedField: Field?

    var body: some View {
        VStack(spacing: 0) {
            header
            if !accessibilityGranted {
                permissionBanner
            }
            if showSearch {
                searchField
            }
            Divider()
            content
            Divider()
            composerField
        }
        .frame(minWidth: 300)
        .background(shortcutButtons)
        .overlay(sectionSwitcher)
        .onDrop(of: [UTType.image.identifier, UTType.fileURL.identifier], isTargeted: nil, perform: handleDrop)
        .onReceive(NotificationCenter.default.publisher(for: .promptPanelDidShow)) { _ in
            focusedField = .composer
            accessibilityGranted = AXIsProcessTrusted()
        }
        .onAppear { focusedField = .composer }
    }

    // MARK: - Header

    private var header: some View {
        HStack(spacing: 10) {
            Button {
                withAnimation(.easeInOut(duration: 0.15)) { showSectionSwitcher.toggle() }
            } label: {
                HStack(spacing: 4) {
                    Text(store.activeSection.name.uppercased())
                        .font(.system(size: 12, weight: .semibold))
                        .tracking(1)
                    Image(systemName: "chevron.down")
                        .font(.system(size: 9, weight: .bold))
                }
                .foregroundStyle(.secondary)
            }
            .buttonStyle(.plain)
            .help("Switch section (Cmd+K)")

            Spacer()

            Button { toggleSearch() } label: { Image(systemName: "magnifyingglass") }
                .buttonStyle(.plain).foregroundStyle(.secondary).help("Search (Cmd+F)")
            Button { addPhotos() } label: { Image(systemName: "photo.on.rectangle.angled") }
                .buttonStyle(.plain).foregroundStyle(.secondary).help("Add photos")
            Button { PanelController.shared.hide() } label: { Image(systemName: "xmark") }
                .buttonStyle(.plain).foregroundStyle(.secondary).help("Close (Esc)")
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 10)
    }

    private var permissionBanner: some View {
        HStack(spacing: 8) {
            Image(systemName: "exclamationmark.triangle.fill")
                .foregroundStyle(.yellow)
            Text("Shift-tap capture needs Accessibility access.")
                .font(.caption)
            Spacer()
            Button("Grant…") {
                let options = [kAXTrustedCheckOptionPrompt.takeUnretainedValue(): true] as CFDictionary
                _ = AXIsProcessTrustedWithOptions(options)
            }
            .font(.caption)
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 8)
        .background(Color.yellow.opacity(0.1))
    }

    private var searchField: some View {
        HStack(spacing: 8) {
            Image(systemName: "magnifyingglass").foregroundStyle(.secondary)
            TextField("Search all sections", text: $search)
                .textFieldStyle(.plain)
                .focused($focusedField, equals: .search)
                .onExitCommand {
                    search = ""
                    showSearch = false
                    focusedField = .composer
                }
            if !search.isEmpty {
                Button { search = "" } label: { Image(systemName: "xmark.circle.fill") }
                    .buttonStyle(.plain).foregroundStyle(.secondary)
            }
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 8)
    }

    // MARK: - Content

    private var displayedItems: [(section: String, item: PromptItem)] {
        if search.isEmpty {
            return store.activeSection.items.map { ("", $0) }
        }
        let query = search.lowercased()
        return store.sections.flatMap { section in
            section.items.compactMap { item in
                switch item.content {
                case .text(let text) where text.lowercased().contains(query):
                    return (section.name, item)
                default:
                    return nil
                }
            }
        }
    }

    private var content: some View {
        ScrollViewReader { proxy in
            ScrollView {
                LazyVStack(spacing: 6) {
                    if displayedItems.isEmpty {
                        emptyState
                    }
                    ForEach(displayedItems, id: \.item.id) { entry in
                        row(for: entry.item, sectionName: entry.section)
                            .id(entry.item.id)
                    }
                }
                .padding(10)
            }
            .onChange(of: store.activeSection.items.count) { _ in
                if let last = store.activeSection.items.last {
                    withAnimation { proxy.scrollTo(last.id, anchor: .bottom) }
                }
            }
        }
    }

    private var emptyState: some View {
        VStack(spacing: 10) {
            Image(systemName: "tray")
                .font(.system(size: 28))
                .foregroundStyle(.quaternary)
            Text(search.isEmpty ? "Nothing here yet" : "No matches")
                .font(.callout)
                .foregroundStyle(.secondary)
            if search.isEmpty {
                Text("Select text anywhere and tap Shift twice,\nor drop photos into this panel.")
                    .font(.caption)
                    .foregroundStyle(.tertiary)
                    .multilineTextAlignment(.center)
            }
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 48)
    }

    private func row(for item: PromptItem, sectionName: String) -> some View {
        Button { handleClick(item) } label: {
            VStack(alignment: .leading, spacing: 6) {
                if !sectionName.isEmpty {
                    Text(sectionName.uppercased())
                        .font(.system(size: 9, weight: .semibold))
                        .tracking(1)
                        .foregroundStyle(.tertiary)
                }
                itemContent(item)
                HStack(spacing: 6) {
                    if let sourceApp = item.sourceApp {
                        Text(sourceApp)
                    }
                    Text(item.createdAt, style: .time)
                    if item.done {
                        Image(systemName: "checkmark")
                    }
                }
                .font(.caption2)
                .foregroundStyle(.tertiary)
            }
            .padding(10)
            .frame(maxWidth: .infinity, alignment: .leading)
            .background(rowBackground(item))
            .cornerRadius(8)
            .overlay(alignment: .topTrailing) {
                if copiedID == item.id {
                    Label("Copied", systemImage: "checkmark.circle.fill")
                        .font(.caption2)
                        .foregroundStyle(.green)
                        .padding(6)
                        .transition(.opacity)
                }
            }
        }
        .buttonStyle(.plain)
        .contextMenu { contextMenu(for: item) }
    }

    private func rowBackground(_ item: PromptItem) -> Color {
        if selection.contains(item.id) { return Color.accentColor.opacity(0.25) }
        return Color.primary.opacity(0.05)
    }

    @ViewBuilder
    private func itemContent(_ item: PromptItem) -> some View {
        switch item.content {
        case .text(let text):
            Text(markdown(text))
                .font(.callout)
                .strikethrough(item.done)
                .opacity(item.done ? 0.45 : 1)
                .lineLimit(8)
                .multilineTextAlignment(.leading)
                .frame(maxWidth: .infinity, alignment: .leading)
        case .image(let filename):
            if let image = store.image(for: filename) {
                Image(nsImage: image)
                    .resizable()
                    .scaledToFit()
                    .frame(maxHeight: 160)
                    .cornerRadius(6)
                    .opacity(item.done ? 0.4 : 1)
            } else {
                Label("Missing image", systemImage: "photo")
                    .foregroundStyle(.secondary)
            }
        }
    }

    private func contextMenu(for item: PromptItem) -> some View {
        Group {
            Button("Copy") { copy(item) }
            Button("Copy as List") {
                store.copyAsList(ids: effectiveIDs(for: item))
                flashCopied(item)
            }
            Divider()
            Button(item.done ? "Mark as Not Done" : "Mark as Done") { store.toggleDone(item.id) }
            if case .text(let text) = item.content {
                Button("Edit…") {
                    PanelController.shared.editController.edit(itemID: item.id, text: text)
                }
            }
            if case .image(let filename) = item.content {
                Button("Open") {
                    NSWorkspace.shared.open(store.imageURL(for: filename))
                }
            }
            if selection.count > 1, selection.contains(item.id) {
                Button("Merge Notes") {
                    store.merge(ids: selection)
                    selection.removeAll()
                }
            }
            Menu("Move To") {
                ForEach(store.sections.filter { $0.id != store.sectionID(of: item.id) }) { section in
                    Button(section.name) { store.move(item.id, to: section.id) }
                }
            }
            Divider()
            Button("Delete", role: .destructive) {
                selection.remove(item.id)
                store.delete(item.id)
            }
        }
    }

    // MARK: - Section switcher

    @ViewBuilder
    private var sectionSwitcher: some View {
        if showSectionSwitcher {
            VStack(spacing: 0) {
                Color.black.opacity(0.001)
                    .onTapGesture { showSectionSwitcher = false }
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            VStack(spacing: 0) {
                ForEach(store.sections) { section in
                    Button {
                        store.activeSectionID = section.id
                        showSectionSwitcher = false
                    } label: {
                        HStack {
                            Text(section.name)
                                .font(.callout)
                            Spacer()
                            Text("\(section.items.count)")
                                .font(.caption)
                                .foregroundStyle(.tertiary)
                            if section.id == store.activeSection.id {
                                Image(systemName: "checkmark")
                                    .font(.caption)
                                    .foregroundStyle(Color.accentColor)
                            }
                        }
                        .padding(.horizontal, 14)
                        .padding(.vertical, 8)
                        .contentShape(Rectangle())
                    }
                    .buttonStyle(.plain)
                }
                Divider()
                Button {
                    composer = "# "
                    showSectionSwitcher = false
                    focusedField = .composer
                } label: {
                    HStack {
                        Image(systemName: "plus")
                        Text("New Section")
                        Spacer()
                    }
                    .padding(.horizontal, 14)
                    .padding(.vertical, 8)
                    .contentShape(Rectangle())
                }
                .buttonStyle(.plain)
            }
            .background(.regularMaterial)
            .cornerRadius(10)
            .shadow(radius: 12)
            .padding(.horizontal, 24)
            .frame(maxHeight: .infinity, alignment: .top)
            .padding(.top, 44)
            .transition(.opacity)
        }
    }

    // MARK: - Composer

    private var composerField: some View {
        HStack(spacing: 8) {
            TextField("Add a note or prompt (\(store.activeSection.name))", text: $composer)
                .textFieldStyle(.plain)
                .focused($focusedField, equals: .composer)
                .onSubmit(submit)
                .onExitCommand { PanelController.shared.hide() }
            if !composer.isEmpty {
                Button(action: submit) { Image(systemName: "arrow.up.circle.fill") }
                    .buttonStyle(.plain)
                    .foregroundStyle(Color.accentColor)
            }
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 10)
    }

    private func submit() {
        let text = composer.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !text.isEmpty else { return }
        if text.hasPrefix("#") {
            let name = String(text.dropFirst()).trimmingCharacters(in: .whitespaces)
            if !name.isEmpty { store.createSection(named: name) }
        } else {
            store.addText(text)
        }
        composer = ""
    }

    // MARK: - Shortcuts

    // Only Cmd-modified shortcuts live here: bare keys (Space, Delete, Cmd+C)
    // would be swallowed as key equivalents and break typing in the composer.
    private var shortcutButtons: some View {
        VStack {
            Button("") { toggleSearch() }
                .keyboardShortcut("f", modifiers: .command)
            Button("") {
                withAnimation(.easeInOut(duration: 0.15)) { showSectionSwitcher.toggle() }
            }
            .keyboardShortcut("k", modifiers: .command)
            Button("") { focusedField = .composer }
                .keyboardShortcut("n", modifiers: .command)
            Button("") {
                guard !selection.isEmpty else { return }
                store.copyAsList(ids: selection)
                if let id = selection.first { flashCopied(PromptItem(id: id, content: .text(""))) }
            }
            .keyboardShortcut("c", modifiers: [.command, .shift])
        }
        .opacity(0)
        .frame(width: 0, height: 0)
        .allowsHitTesting(false)
    }

    // MARK: - Actions

    private func handleClick(_ item: PromptItem) {
        if NSApp.currentEvent?.modifierFlags.contains(.command) == true {
            if selection.contains(item.id) {
                selection.remove(item.id)
            } else {
                selection.insert(item.id)
            }
            return
        }
        copy(item)
    }

    private func copy(_ item: PromptItem) {
        store.copy(item)
        flashCopied(item)
    }

    private func flashCopied(_ item: PromptItem) {
        withAnimation { copiedID = item.id }
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.2) {
            if copiedID == item.id {
                withAnimation { copiedID = nil }
            }
        }
    }

    private func effectiveIDs(for item: PromptItem) -> Set<UUID> {
        if selection.contains(item.id), selection.count > 1 { return selection }
        return [item.id]
    }

    private func toggleSearch() {
        showSearch.toggle()
        if showSearch {
            focusedField = .search
        } else {
            search = ""
            focusedField = .composer
        }
    }

    private func addPhotos() {
        let panel = NSOpenPanel()
        panel.allowedContentTypes = [.image]
        panel.allowsMultipleSelection = true
        guard panel.runModal() == .OK else { return }
        for url in panel.urls {
            if let image = NSImage(contentsOf: url) {
                store.addImage(image)
            }
        }
    }

    private func handleDrop(_ providers: [NSItemProvider]) -> Bool {
        var handled = false
        for provider in providers {
            if provider.canLoadObject(ofClass: NSImage.self) {
                handled = true
                _ = provider.loadObject(ofClass: NSImage.self) { object, _ in
                    if let image = object as? NSImage {
                        Task { @MainActor in Store.shared.addImage(image) }
                    }
                }
            } else if provider.hasItemConformingToTypeIdentifier(UTType.fileURL.identifier) {
                handled = true
                provider.loadItem(forTypeIdentifier: UTType.fileURL.identifier, options: nil) { item, _ in
                    guard let data = item as? Data,
                          let url = URL(dataRepresentation: data, relativeTo: nil),
                          let image = NSImage(contentsOf: url) else { return }
                    Task { @MainActor in Store.shared.addImage(image) }
                }
            }
        }
        return handled
    }

    private func markdown(_ string: String) -> AttributedString {
        let options = AttributedString.MarkdownParsingOptions(interpretedSyntax: .inlineOnlyPreservingWhitespace)
        return (try? AttributedString(markdown: string, options: options)) ?? AttributedString(string)
    }
}