import AppKit
import MarkdownUI
import SwiftUI

private let r: Double = 8

struct ChatPanel: View {
    let chat: ChatProvider
    @Namespace var inputAreaNamespace
    @State var typedMessage = ""

    var body: some View {
        VStack(spacing: 0) {
            ChatPanelToolbar(chat: chat)
            Divider()
            ChatPanelMessages(
                chat: chat
            )
            Divider()
            ChatPanelInputArea(
                chat: chat,
                typedMessage: $typedMessage
            )
        }
        .background(.regularMaterial)
        .xcodeStyleFrame()
    }
}

struct ChatPanelToolbar: View {
    @ObservedObject var chat: ChatProvider
    @AppStorage(\.useGlobalChat) var useGlobalChat

    var body: some View {
        HStack {
            Button(action: {
                chat.close()
            }) {
                Image(systemName: "xmark")
                    .padding(4)
                    .foregroundStyle(.secondary)
            }
            .buttonStyle(.plain)
            .keyboardShortcut("w", modifiers: [.command])

            Spacer()

            Toggle(isOn: .init(get: {
                useGlobalChat
            }, set: { _ in
                chat.switchContext()
            })) { EmptyView() }
                .toggleStyle(GlobalChatSwitchToggleStyle())
        }
        .padding(.leading, 4)
        .padding(.trailing, 8)
        .padding(.vertical, 4)
        .background(.regularMaterial)
    }
}

struct ChatPanelMessages: View {
    @ObservedObject var chat: ChatProvider

    var body: some View {
        List {
            Group {
                Spacer()

                if chat.isReceivingMessage {
                    StopRespondingButton(chat: chat)
                        .padding(.vertical, 4)
                        .listRowInsets(EdgeInsets(top: 0, leading: -8, bottom: 0, trailing: -8))
                }

                ForEach(chat.history.reversed(), id: \.id) { message in
                    let text = message.text.isEmpty && !message.isUser ? "..." : message
                        .text

                    if message.isUser {
                        UserMessage(id: message.id, text: text, chat: chat)
                            .listRowInsets(EdgeInsets(top: 0, leading: -8, bottom: 0, trailing: -8))
                            .padding(.vertical, 4)
                    } else {
                        BotMessage(id: message.id, text: text, chat: chat)
                            .listRowInsets(EdgeInsets(top: 0, leading: -8, bottom: 0, trailing: -8))
                            .padding(.vertical, 4)
                    }
                }
                .listItemTint(.clear)

                Instruction()

                Spacer()
            }
            .scaleEffect(x: -1, y: 1, anchor: .center)
        }
        .id("\(chat.history.count), \(chat.isReceivingMessage)")
        .listStyle(.plain)
        .scaleEffect(x: 1, y: -1, anchor: .center)
    }
}

private struct StopRespondingButton: View {
    let chat: ChatProvider

    var body: some View {
        Button(action: {
            chat.stop()
        }) {
            HStack(spacing: 4) {
                Image(systemName: "stop.fill")
                Text("Stop Responding")
            }
            .padding(8)
            .background(
                .regularMaterial,
                in: RoundedRectangle(cornerRadius: r, style: .continuous)
            )
            .overlay {
                RoundedRectangle(cornerRadius: r, style: .continuous)
                    .stroke(Color(nsColor: .separatorColor), lineWidth: 1)
            }
        }
        .buttonStyle(.borderless)
        .scaleEffect(x: -1, y: -1, anchor: .center)
        .frame(maxWidth: .infinity, alignment: .center)
    }
}

private struct Instruction: View {
    @AppStorage(\.useSelectionScopeByDefaultInChatContext)
    var useSelectionScopeByDefaultInChatContext
    @AppStorage(\.chatFontSize) var chatFontSize

    var body: some View {
        Group {
            if useSelectionScopeByDefaultInChatContext {
                Markdown(
                    """
                    Hello, I am your AI programming assistant. I can identify issues, explain and even improve code.

                    Currently, I have the ability to read the following details from the active editor:
                    - The **selected code**.
                    - The **relative path** of the file.
                    - The **error and warning** labels.
                    - The text cursor location.

                    If you'd like me to examine the entire file, simply add `@file` to the beginning of your message.
                    """
                )
            } else {
                Markdown(
                    """
                    Hello, I am your AI programming assistant. I can identify issues, explain and even improve code.

                    Currently, I have the ability to read the following details from the active editor:
                    - The **relative path** of the file.
                    - The **error and warning** labels.
                    - The text cursor location.

                    If you would like me to examine the selected code, please prefix your message with `@selection`. If you would like me to examine the entire file, please prefix your message with `@file`.
                    """
                )
            }
        }
        .textSelection(.enabled)
        .markdownTheme(.custom(fontSize: chatFontSize))
        .opacity(0.8)
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding()
        .overlay {
            RoundedRectangle(cornerRadius: 8)
                .stroke(Color(nsColor: .separatorColor), lineWidth: 1)
        }
        .scaleEffect(x: -1, y: -1, anchor: .center)
    }
}

private struct UserMessage: View {
    let id: String
    let text: String
    let chat: ChatProvider
    @Environment(\.colorScheme) var colorScheme
    @AppStorage(\.chatFontSize) var chatFontSize
    @AppStorage(\.chatCodeFontSize) var chatCodeFontSize

    var body: some View {
        Markdown(text)
            .textSelection(.enabled)
            .markdownTheme(.custom(fontSize: chatFontSize))
            .markdownCodeSyntaxHighlighter(
                ChatCodeSyntaxHighlighter(
                    brightMode: colorScheme != .dark,
                    fontSize: chatCodeFontSize
                )
            )
            .frame(alignment: .leading)
            .padding()
            .background {
                RoundedCorners(tl: r, tr: r, bl: r, br: 0)
                    .fill(Color.userChatContentBackground)
            }
            .overlay {
                RoundedCorners(tl: r, tr: r, bl: r, br: 0)
                    .stroke(Color(nsColor: .separatorColor), lineWidth: 1)
            }
            .padding(.leading)
            .padding(.trailing, 8)
            .scaleEffect(x: -1, y: -1, anchor: .center)
            .shadow(color: .black.opacity(0.1), radius: 2)
            .frame(maxWidth: .infinity, alignment: .leading)
            .contextMenu {
                Button("Copy") {
                    NSPasteboard.general.clearContents()
                    NSPasteboard.general.setString(text, forType: .string)
                }

                Button("Send Again") {
                    chat.resendMessage(id: id)
                }

                Button("Set as Extra System Prompt") {
                    chat.setAsExtraPrompt(id: id)
                }

                Divider()

                Button("Delete") {
                    chat.deleteMessage(id: id)
                }
            }
    }
}

private struct BotMessage: View {
    let id: String
    let text: String
    let chat: ChatProvider
    @Environment(\.colorScheme) var colorScheme
    @AppStorage(\.chatFontSize) var chatFontSize
    @AppStorage(\.chatCodeFontSize) var chatCodeFontSize

    var body: some View {
        HStack(alignment: .bottom, spacing: 2) {
            CopyButton {
                NSPasteboard.general.clearContents()
                NSPasteboard.general.setString(text, forType: .string)
            }
            .scaleEffect(x: -1, y: -1, anchor: .center)

            Markdown(text)
                .textSelection(.enabled)
                .markdownTheme(.custom(fontSize: chatFontSize))
                .markdownCodeSyntaxHighlighter(
                    ChatCodeSyntaxHighlighter(
                        brightMode: colorScheme != .dark,
                        fontSize: chatCodeFontSize
                    )
                )
                .frame(alignment: .trailing)
                .padding()
                .background {
                    RoundedCorners(tl: r, tr: r, bl: 0, br: r)
                        .fill(Color.contentBackground)
                }
                .overlay {
                    RoundedCorners(tl: r, tr: r, bl: 0, br: r)
                        .stroke(Color(nsColor: .separatorColor), lineWidth: 1)
                }
                .padding(.leading, 8)
                .scaleEffect(x: -1, y: -1, anchor: .center)
                .shadow(color: .black.opacity(0.1), radius: 2)
                .contextMenu {
                    Button("Copy") {
                        NSPasteboard.general.clearContents()
                        NSPasteboard.general.setString(text, forType: .string)
                    }

                    Button("Set as Extra System Prompt") {
                        chat.setAsExtraPrompt(id: id)
                    }

                    Divider()

                    Button("Delete") {
                        chat.deleteMessage(id: id)
                    }
                }
        }
        .frame(maxWidth: .infinity, alignment: .trailing)
        .padding(.trailing, 2)
    }
}

struct ChatPanelInputArea: View {
    @ObservedObject var chat: ChatProvider
    @Binding var typedMessage: String
    @FocusState var isInputAreaFocused: Bool

    var body: some View {
        HStack {
            clearButton
            textEditor
        }
        .onAppear {
            isInputAreaFocused = true
        }
        .padding(8)
        .background(.ultraThickMaterial)
        .contextMenu {
            ChatContextMenu(chat: chat)
        }
    }

    var clearButton: some View {
        Button(action: {
            chat.clear()
        }) {
            Group {
                if #available(macOS 13.0, *) {
                    Image(systemName: "eraser.line.dashed.fill")
                } else {
                    Image(systemName: "trash.fill")
                }
            }
            .padding(6)
            .background {
                Circle().fill(Color(nsColor: .controlBackgroundColor))
            }
            .overlay {
                Circle()
                    .stroke(Color(nsColor: .controlColor), lineWidth: 1)
            }
        }
        .buttonStyle(.plain)
    }

    var textEditor: some View {
        HStack(spacing: 0) {
            ZStack(alignment: .center) {
                // a hack to support dynamic height of TextEditor
                Text(typedMessage.isEmpty ? "Hi" : typedMessage).opacity(0)
                    .font(.system(size: 14))
                    .frame(maxWidth: .infinity, maxHeight: 400)
                    .padding(.top, 1)
                    .padding(.bottom, 2)
                    .padding(.horizontal, 4)

                CustomTextEditor(
                    text: $typedMessage,
                    font: .systemFont(ofSize: 14),
                    onSubmit: { submitText() },
                    completions: { text, _, range in
                        if text.isEmpty { return [] }
                        let availableFeatures = [
                            "/run",
                            "/airun",
                            "/math",
                            "/search",
                            "@selection",
                            "@file",
                        ]
                        return availableFeatures
                            .filter { $0.hasPrefix(text) && $0 != text }
                            .compactMap {
                                guard let index = $0.index(
                                    $0.startIndex,
                                    offsetBy: range.location,
                                    limitedBy: $0.endIndex
                                ) else { return nil }
                                return String($0[index...])
                            }
                    }
                )
                .padding(.top, 1)
                .padding(.bottom, -1)
            }
            .focused($isInputAreaFocused)
            .padding(8)
            .fixedSize(horizontal: false, vertical: true)

            Button(action: {
                submitText()
            }) {
                Image(systemName: "paperplane.fill")
                    .padding(8)
            }
            .buttonStyle(.plain)
            .disabled(chat.isReceivingMessage)
            .keyboardShortcut(KeyEquivalent.return, modifiers: [])
        }
        .frame(maxWidth: .infinity)
        .background {
            RoundedRectangle(cornerRadius: 6)
                .fill(Color(nsColor: .controlBackgroundColor))
        }
        .overlay {
            RoundedRectangle(cornerRadius: 6)
                .stroke(Color(nsColor: .controlColor), lineWidth: 1)
        }
        .background {
            Button(action: {
                typedMessage += "\n"
            }) {
                EmptyView()
            }
            .keyboardShortcut(KeyEquivalent.return, modifiers: [.shift])
        }
    }

    func submitText() {
        if typedMessage.isEmpty { return }
        chat.send(typedMessage)
        typedMessage = ""
    }
}

struct ChatContextMenu: View {
    let chat: ChatProvider
    @AppStorage(\.customCommands) var customCommands

    var body: some View {
        Group {
            currentSystemPrompt
            currentExtraSystemPrompt
            resetPrompt

            Divider()

            customCommandMenu
        }
    }

    @ViewBuilder
    var currentSystemPrompt: some View {
        Text("System Prompt:")
        Text({
            var text = chat.systemPrompt
            if text.isEmpty { text = "N/A" }
            if text.count > 30 { text = String(text.prefix(30)) + "..." }
            return text
        }() as String)
    }

    @ViewBuilder
    var currentExtraSystemPrompt: some View {
        Text("Extra Prompt:")
        Text({
            var text = chat.extraSystemPrompt
            if text.isEmpty { text = "N/A" }
            if text.count > 30 { text = String(text.prefix(30)) + "..." }
            return text
        }() as String)
    }

    var resetPrompt: some View {
        Button("Reset System Prompt") {
            chat.resetPrompt()
        }
    }

    var customCommandMenu: some View {
        Menu("Custom Commands") {
            ForEach(
                customCommands.filter {
                    switch $0.feature {
                    case .chatWithSelection, .customChat: return true
                    case .promptToCode: return false
                    }
                },
                id: \.name
            ) { command in
                Button(action: {
                    chat.triggerCustomCommand(command)
                }) {
                    Text(command.name)
                }
            }
        }
    }
}

struct RoundedCorners: Shape {
    var tl: CGFloat = 0.0
    var tr: CGFloat = 0.0
    var bl: CGFloat = 0.0
    var br: CGFloat = 0.0

    func path(in rect: CGRect) -> Path {
        Path { path in

            let w = rect.size.width
            let h = rect.size.height

            // Make sure we do not exceed the size of the rectangle
            let tr = min(min(self.tr, h / 2), w / 2)
            let tl = min(min(self.tl, h / 2), w / 2)
            let bl = min(min(self.bl, h / 2), w / 2)
            let br = min(min(self.br, h / 2), w / 2)

            path.move(to: CGPoint(x: w / 2.0, y: 0))
            path.addLine(to: CGPoint(x: w - tr, y: 0))
            path.addArc(
                center: CGPoint(x: w - tr, y: tr),
                radius: tr,
                startAngle: Angle(degrees: -90),
                endAngle: Angle(degrees: 0),
                clockwise: false
            )
            path.addLine(to: CGPoint(x: w, y: h - br))
            path.addArc(
                center: CGPoint(x: w - br, y: h - br),
                radius: br,
                startAngle: Angle(degrees: 0),
                endAngle: Angle(degrees: 90),
                clockwise: false
            )
            path.addLine(to: CGPoint(x: bl, y: h))
            path.addArc(
                center: CGPoint(x: bl, y: h - bl),
                radius: bl,
                startAngle: Angle(degrees: 90),
                endAngle: Angle(degrees: 180),
                clockwise: false
            )
            path.addLine(to: CGPoint(x: 0, y: tl))
            path.addArc(
                center: CGPoint(x: tl, y: tl),
                radius: tl,
                startAngle: Angle(degrees: 180),
                endAngle: Angle(degrees: 270),
                clockwise: false
            )
            path.closeSubpath()
        }
    }
}

struct GlobalChatSwitchToggleStyle: ToggleStyle {
    func makeBody(configuration: Configuration) -> some View {
        HStack(spacing: 4) {
            Text(configuration.isOn ? "Shared Conversation" : "Local Conversation")
                .foregroundStyle(.tertiary)

            RoundedRectangle(cornerRadius: 10, style: .circular)
                .foregroundColor(configuration.isOn ? Color.indigo : .gray.opacity(0.5))
                .frame(width: 30, height: 20, alignment: .center)
                .overlay(
                    Circle()
                        .fill(.regularMaterial)
                        .padding(.all, 2)
                        .overlay(
                            Image(
                                systemName: configuration
                                    .isOn ? "globe" : "doc.circle"
                            )
                            .resizable()
                            .aspectRatio(contentMode: .fit)
                            .frame(width: 12, height: 12, alignment: .center)
                            .foregroundStyle(.secondary)
                        )
                        .offset(x: configuration.isOn ? 5 : -5, y: 0)
                        .animation(.linear(duration: 0.1), value: configuration.isOn)
                )
                .onTapGesture { configuration.isOn.toggle() }
                .overlay {
                    RoundedRectangle(cornerRadius: 10, style: .circular)
                        .stroke(.black.opacity(0.2), lineWidth: 1)
                }
        }
    }
}

// MARK: - Previews

struct ChatPanel_Preview: PreviewProvider {
    static let history: [ChatMessage] = [
        .init(
            id: "1",
            isUser: true,
            text: "**Hello**"
        ),
        .init(
            id: "2",
            isUser: false,
            text: """
            ```swift
            func foo() {}
            ```
            **Hey**! What can I do for you?**Hey**! What can I do for you?**Hey**! What can I do for you?**Hey**! What can I do for you?
            """
        ),
        .init(id: "5", isUser: false, text: "Yooo"),
        .init(id: "4", isUser: true, text: "Yeeeehh"),
        .init(
            id: "3",
            isUser: true,
            text: #"""
            Please buy me a coffee!
            | Coffee | Milk |
            |--------|------|
            | Espresso | No |
            | Latte | Yes |

            ```swift
            func foo() {}
            ```
            ```objectivec
            - (void)bar {}
            ```
            """#
        ),
    ]

    static var previews: some View {
        ChatPanel(chat: .init(
            history: ChatPanel_Preview.history,
            isReceivingMessage: true
        ))
        .frame(width: 450, height: 700)
        .colorScheme(.dark)
    }
}

struct ChatPanel_EmptyChat_Preview: PreviewProvider {
    static var previews: some View {
        ChatPanel(chat: .init(
            history: [],
            isReceivingMessage: false
        ))
        .padding()
        .frame(width: 450, height: 600)
        .colorScheme(.dark)
    }
}

struct ChatCodeSyntaxHighlighter: CodeSyntaxHighlighter {
    let brightMode: Bool
    let fontSize: Double

    init(brightMode: Bool, fontSize: Double) {
        self.brightMode = brightMode
        self.fontSize = fontSize
    }

    func highlightCode(_ content: String, language: String?) -> Text {
        let content = highlightedCodeBlock(
            code: content,
            language: language ?? "",
            brightMode: brightMode,
            fontSize: fontSize
        )
        return Text(AttributedString(content))
    }
}

struct ChatPanel_InputText_Preview: PreviewProvider {
    static var previews: some View {
        ChatPanel(chat: .init(
            history: ChatPanel_Preview.history,
            isReceivingMessage: false
        ))
        .padding()
        .frame(width: 450, height: 600)
        .colorScheme(.dark)
    }
}

struct ChatPanel_InputMultilineText_Preview: PreviewProvider {
    static var previews: some View {
        ChatPanel(
            chat: .init(
                history: ChatPanel_Preview.history,
                isReceivingMessage: false
            ),
            typedMessage: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce turpis dolor, malesuada quis fringilla sit amet, placerat at nunc. Suspendisse orci tortor, tempor nec blandit a, malesuada vel tellus. Nunc sed leo ligula. Ut at ligula eget turpis pharetra tristique. Integer luctus leo non elit rhoncus fermentum."
        )
        .padding()
        .frame(width: 450, height: 600)
        .colorScheme(.dark)
    }
}

struct ChatPanel_Light_Preview: PreviewProvider {
    static var previews: some View {
        ChatPanel(chat: .init(
            history: ChatPanel_Preview.history,
            isReceivingMessage: true
        ))
        .padding()
        .frame(width: 450, height: 600)
        .colorScheme(.light)
    }
}