use std::sync::Mutex;
use std::time::Duration;
use log::{debug, error, info, trace, warn};
use once_cell::sync::Lazy;
use rocket::{get, post};
use rocket::response::stream::TextStream;
use rocket::serde::json::Json;
use rocket::serde::Serialize;
use serde::Deserialize;
use tauri::updater::UpdateResponse;
use tauri::{FileDropEvent, UpdaterEvent, RunEvent, Manager, PathResolver, Window, WindowEvent};
use tauri::api::dialog::blocking::FileDialogBuilder;
use tokio::sync::broadcast;
use tokio::time;
use crate::api_token::APIToken;
use crate::dotnet::stop_dotnet_server;
use crate::environment::{is_prod, is_dev, CONFIG_DIRECTORY, DATA_DIRECTORY};
use crate::log::switch_to_file_logging;
use crate::pdfium::PDFIUM_LIB_PATH;

/// The Tauri main window.
static MAIN_WINDOW: Lazy<Mutex<Option<Window>>> = Lazy::new(|| Mutex::new(None));

/// The update response coming from the Tauri updater.
static CHECK_UPDATE_RESPONSE: Lazy<Mutex<Option<UpdateResponse<tauri::Wry>>>> = Lazy::new(|| Mutex::new(None));

/// The event broadcast sender for Tauri events.
static EVENT_BROADCAST: Lazy<Mutex<Option<broadcast::Sender<Event>>>> = Lazy::new(|| Mutex::new(None));

/// Starts the Tauri app.
pub fn start_tauri() {
    info!("Starting Tauri app...");

    // Create the event broadcast channel:
    let (event_sender, root_event_receiver) = broadcast::channel(100);

    // Save a copy of the event broadcast sender for later use:
    *EVENT_BROADCAST.lock().unwrap() = Some(event_sender.clone());

    // When the last receiver is dropped, we lose the ability to send events.
    // Therefore, we spawn a task that keeps the root receiver alive:
    tauri::async_runtime::spawn(async move {
        let mut root_receiver = root_event_receiver;
        loop {
            match root_receiver.recv().await {
                Ok(event) => {
                    debug!(Source = "Tauri"; "Tauri event received: location=root receiver       , event={event:?}");
                },

                Err(broadcast::error::RecvError::Lagged(skipped)) => {
                    warn!(Source = "Tauri"; "Root event receiver lagged, skipped {skipped} messages.");
                },

                Err(broadcast::error::RecvError::Closed) => {
                    warn!(Source = "Tauri"; "Root event receiver channel closed.");
                    return;
                },
            }
        }
    });

    let app = tauri::Builder::default()
        .setup(move |app| {

            // Get the main window:
            let window = app.get_window("main").expect("Failed to get main window.");

            // Register a callback for window events, such as file drops. We have to use
            // this handler in addition to the app event handler, because file drop events
            // are only available in the window event handler (is a bug, cf. https://github.com/tauri-apps/tauri/issues/14338):
            window.on_window_event(move |event| {
                debug!(Source = "Tauri"; "Tauri event received: location=window event handler, event={event:?}");
                let event_to_send = Event::from_window_event(event);
                let sender = event_sender.clone();
                tauri::async_runtime::spawn(async move {
                    match sender.send(event_to_send) {
                        Ok(_) => {},
                        Err(error) => error!(Source = "Tauri"; "Failed to channel window event: {error}"),
                    }
                });
            });

            // Save the main window for later access:
            *MAIN_WINDOW.lock().unwrap() = Some(window);

            info!(Source = "Bootloader Tauri"; "Setup is running.");
            let data_path = app.path_resolver().app_local_data_dir().unwrap();
            let data_path = data_path.join("data");

            // Get and store the data and config directories:
            DATA_DIRECTORY.set(data_path.to_str().unwrap().to_string()).map_err(|_| error!("Was not abe to set the data directory.")).unwrap();
            CONFIG_DIRECTORY.set(app.path_resolver().app_config_dir().unwrap().to_str().unwrap().to_string()).map_err(|_| error!("Was not able to set the config directory.")).unwrap();

            info!(Source = "Bootloader Tauri"; "Reconfigure the file logger to use the app data directory {data_path:?}");
            switch_to_file_logging(data_path).map_err(|e| error!("Failed to switch logging to file: {e}")).unwrap();
            set_pdfium_path(app.path_resolver());
            Ok(())
        })
        .plugin(tauri_plugin_window_state::Builder::default().build())
        .build(tauri::generate_context!())
        .expect("Error while running Tauri application");

    // The app event handler:
    app.run(|app_handle, event| {
        if !matches!(event, RunEvent::MainEventsCleared) {
            debug!(Source = "Tauri"; "Tauri event received: location=app event handler   , event={event:?}");
        }
        
        match event {
            RunEvent::WindowEvent { event, label, .. } => {
                match event {
                    WindowEvent::CloseRequested { .. } => {
                        warn!(Source = "Tauri"; "Window '{label}': close was requested.");
                    }

                    WindowEvent::Destroyed => {
                        warn!(Source = "Tauri"; "Window '{label}': was destroyed.");
                    }

                    _ => (),
                }
            }

            RunEvent::Updater(updater_event) => {
                match updater_event {
                    UpdaterEvent::UpdateAvailable { body, date, version } => {
                        let body_len = body.len();
                        info!(Source = "Tauri"; "Updater: update available: body size={body_len} time={date:?} version={version}");
                    }

                    UpdaterEvent::Pending => {
                        info!(Source = "Tauri"; "Updater: update is pending!");
                    }

                    UpdaterEvent::DownloadProgress { chunk_length, content_length: _ } => {
                        trace!(Source = "Tauri"; "Updater: downloading chunk of {chunk_length} bytes");
                    }

                    UpdaterEvent::Downloaded => {
                        info!(Source = "Tauri"; "Updater: update has been downloaded!");
                        warn!(Source = "Tauri"; "Try to stop the .NET server now...");

                        if is_prod() {
                            stop_dotnet_server();
                        } else {
                            warn!(Source = "Tauri"; "Development environment detected; do not stop the .NET server.");
                        }
                    }

                    UpdaterEvent::Updated => {
                        info!(Source = "Tauri"; "Updater: app has been updated");
                        warn!(Source = "Tauri"; "Try to restart the app now...");

                        if is_prod() {
                            app_handle.restart();
                        } else {
                            warn!(Source = "Tauri"; "Development environment detected; do not restart the app.");
                        }
                    }

                    UpdaterEvent::AlreadyUpToDate => {
                        info!(Source = "Tauri"; "Updater: app is already up to date");
                    }

                    UpdaterEvent::Error(error) => {
                        warn!(Source = "Tauri"; "Updater: failed to update: {error}");
                    }
                }
            }

            RunEvent::ExitRequested { .. } => {
                warn!(Source = "Tauri"; "Run event: exit was requested.");
            }

            RunEvent::Ready => {
                info!(Source = "Tauri"; "Run event: Tauri app is ready.");
            }

            _ => {}
        }
    });

    warn!(Source = "Tauri"; "Tauri app was stopped.");
    if is_prod() {
        warn!("Try to stop the .NET server as well...");
        stop_dotnet_server();
    }
}

/// Our event API endpoint for Tauri events. We try to send an endless stream of events to the client.
/// If no events are available for a certain time, we send a ping event to keep the connection alive.
/// When the client disconnects, the stream is closed. But we try to not lose events in between.
/// The client is expected to reconnect automatically when the connection is closed and continue
/// listening for events.
#[get("/events")]
pub async fn get_event_stream(_token: APIToken) -> TextStream![String] {
    // Get the lock to the event broadcast sender:
    let event_broadcast_lock = EVENT_BROADCAST.lock().unwrap();

    // Get and subscribe to the event receiver:
    let mut event_receiver = event_broadcast_lock.as_ref()
        .expect("Event sender not initialized.")
        .subscribe();

    // Drop the lock to allow other access to the sender:
    drop(event_broadcast_lock);

    // Create the event stream:
    TextStream! {
        loop {
            // Wait at most 3 seconds for an event:
            match time::timeout(Duration::from_secs(3), event_receiver.recv()).await {

                // Case: we received an event
                Ok(Ok(event)) => {
                    // Serialize the event to JSON. Important is that the entire event
                    // is serialized as a single line so that the client can parse it
                    // correctly:
                    let event_json = serde_json::to_string(&event).unwrap();
                    yield event_json;

                    // The client expects a newline after each event because we are using
                    // a method to read the stream line-by-line:
                    yield "\n".to_string();
                },

                // Case: we lagged behind and missed some events
                Ok(Err(broadcast::error::RecvError::Lagged(skipped))) => {
                    warn!(Source = "Tauri"; "Event receiver lagged, skipped {skipped} messages.");
                },

                // Case: the event channel was closed
                Ok(Err(broadcast::error::RecvError::Closed)) => {
                    warn!(Source = "Tauri"; "Event receiver channel closed.");
                    return;
                },

                // Case: timeout. We will send a ping event to keep the connection alive.
                Err(_) => {
                    let ping_event = Event::new(TauriEventType::Ping, Vec::new());

                    // Again, we have to serialize the event as a single line:
                    let event_json = serde_json::to_string(&ping_event).unwrap();
                    yield event_json;

                    // The client expects a newline after each event because we are using
                    // a method to read the stream line-by-line:
                    yield "\n".to_string();
                },
            }
        }
    }
}

/// Data structure representing a Tauri event for our event API.
#[derive(Debug, Clone, Serialize)]
pub struct Event {
    pub event_type: TauriEventType,
    pub payload: Vec<String>,
}

/// Implementation of the Event struct.
impl Event {

    /// Creates a new Event instance.
    pub fn new(event_type: TauriEventType, payload: Vec<String>) -> Self {
        Event {
            payload,
            event_type,
        }
    }

    /// Creates an Event instance from a Tauri WindowEvent.
    pub fn from_window_event(window_event: &WindowEvent) -> Self {
        match window_event {
            WindowEvent::FileDrop(drop_event) => {
                match drop_event {
                    FileDropEvent::Hovered(files) => Event::new(TauriEventType::FileDropHovered,
                                                                files.iter().map(|f| f.to_string_lossy().to_string()).collect(),
                    ),

                    FileDropEvent::Dropped(files) => Event::new(TauriEventType::FileDropDropped,
                                                                files.iter().map(|f| f.to_string_lossy().to_string()).collect(),
                    ),

                    FileDropEvent::Cancelled => Event::new(TauriEventType::FileDropCanceled,
                                                           Vec::new(),
                    ),

                    _ => Event::new(TauriEventType::Unknown,
                                    Vec::new(),
                    ),
                }
            },

            WindowEvent::Focused(state) => if *state {
                Event::new(TauriEventType::WindowFocused,
                           Vec::new(),
                )
            } else {
                Event::new(TauriEventType::WindowNotFocused,
                           Vec::new(),
                )
            },

            _ => Event::new(TauriEventType::Unknown,
                            Vec::new(),
            ),
        }
    }
}

/// The types of Tauri events we can send through our event API.
#[derive(Debug, Serialize, Clone)]
pub enum TauriEventType {
    None,
    Ping,
    Unknown,

    WindowFocused,
    WindowNotFocused,

    FileDropHovered,
    FileDropDropped,
    FileDropCanceled,
}

/// Changes the location of the main window to the given URL.
pub async fn change_location_to(url: &str) {
    // Try to get the main window. If it is not available yet, wait for it:
    let mut main_window_ready = false;
    let mut main_window_status_reported = false;
    let main_window_spawn_clone = &MAIN_WINDOW;
    while !main_window_ready
    {
        main_window_ready = {
            let main_window = main_window_spawn_clone.lock().unwrap();
            main_window.is_some()
        };

        if !main_window_ready {
            if !main_window_status_reported {
                info!("Waiting for main window to be ready, because .NET was faster than Tauri.");
                main_window_status_reported = true;
            }

            time::sleep(Duration::from_millis(100)).await;
        }
    }

    let js_location_change = format!("window.location = '{url}';");
    let main_window = main_window_spawn_clone.lock().unwrap();
    let location_change_result = main_window.as_ref().unwrap().eval(js_location_change.as_str());
    match location_change_result {
        Ok(_) => info!("The app location was changed to {url}."),
        Err(e) => error!("Failed to change the app location to {url}: {e}."),
    }
}

/// Checks for updates.
#[get("/updates/check")]
pub async fn check_for_update(_token: APIToken) -> Json<CheckUpdateResponse> {
    if is_dev() {
        warn!(Source = "Updater"; "The app is running in development mode; skipping update check.");
        return Json(CheckUpdateResponse {
            update_is_available: false,
            error: false,
            new_version: String::from(""),
            changelog: String::from(""),
        });
    }

    let app_handle = MAIN_WINDOW.lock().unwrap().as_ref().unwrap().app_handle();
    let response = app_handle.updater().check().await;
    match response {
        Ok(update_response) => match update_response.is_update_available() {
            true => {
                *CHECK_UPDATE_RESPONSE.lock().unwrap() = Some(update_response.clone());
                let new_version = update_response.latest_version();
                info!(Source = "Updater"; "An update to version '{new_version}' is available.");
                let changelog = update_response.body();
                Json(CheckUpdateResponse {
                    update_is_available: true,
                    error: false,
                    new_version: new_version.to_string(),
                    changelog: match changelog {
                        Some(c) => c.to_string(),
                        None => String::from(""),
                    },
                })
            },

            false => {
                info!(Source = "Updater"; "No updates are available.");
                Json(CheckUpdateResponse {
                    update_is_available: false,
                    error: false,
                    new_version: String::from(""),
                    changelog: String::from(""),
                })
            },
        },

        Err(e) => {
            warn!(Source = "Updater"; "Failed to check for updates: {e}.");
            Json(CheckUpdateResponse {
                update_is_available: false,
                error: true,
                new_version: String::from(""),
                changelog: String::from(""),
            })
        },
    }
}

/// The response to the check for update request.
#[derive(Serialize)]
pub struct CheckUpdateResponse {
    update_is_available: bool,
    error: bool,
    new_version: String,
    changelog: String,
}

/// Installs the update.
#[get("/updates/install")]
pub async fn install_update(_token: APIToken) {
    if is_dev() {
        warn!(Source = "Updater"; "The app is running in development mode; skipping update installation.");
        return;
    }

    let cloned_response_option = CHECK_UPDATE_RESPONSE.lock().unwrap().clone();
    match cloned_response_option {
        Some(update_response) => {
            update_response.download_and_install().await.unwrap();
        },

        None => {
            error!(Source = "Updater"; "No update available to install. Did you check for updates first?");
        },
    }
}

/// Let the user select a directory.
#[post("/select/directory?<title>", data = "<previous_directory>")]
pub fn select_directory(_token: APIToken, title: &str, previous_directory: Option<Json<PreviousDirectory>>) -> Json<DirectorySelectionResponse> {
    let folder_path = match previous_directory {
        Some(previous) => {
            let previous_path = previous.path.as_str();
            FileDialogBuilder::new()
                .set_title(title)
                .set_directory(previous_path)
                .pick_folder()
        },

        None => {
            FileDialogBuilder::new()
                .set_title(title)
                .pick_folder()
        },
    };
    
    match folder_path {
        Some(path) => {
            info!("User selected directory: {path:?}");
            Json(DirectorySelectionResponse {
                user_cancelled: false,
                selected_directory: path.to_str().unwrap().to_string(),
            })
        },

        None => {
            info!("User cancelled directory selection.");
            Json(DirectorySelectionResponse {
                user_cancelled: true,
                selected_directory: String::from(""),
            })
        },
    }
}

#[derive(Clone, Deserialize)]
pub struct PreviousDirectory {
    path: String,
}

#[derive(Clone, Deserialize)]
pub struct FileTypeFilter {
    filter_name: String,
    filter_extensions: Vec<String>,
}

#[derive(Clone, Deserialize)]
pub struct SelectFileOptions {
    title: String,
    previous_file: Option<PreviousFile>,
    filter: Option<FileTypeFilter>,
}

#[derive(Clone, Deserialize)]
pub struct SaveFileOptions {
    title: String,
    name_file: Option<PreviousFile>,
    filter: Option<FileTypeFilter>,
}

#[derive(Serialize)]
pub struct DirectorySelectionResponse {
    user_cancelled: bool,
    selected_directory: String,
}

/// Let the user select a file.
#[post("/select/file", data = "<payload>")]
pub fn select_file(_token: APIToken, payload: Json<SelectFileOptions>) -> Json<FileSelectionResponse> {

    // Create a new file dialog builder:
    let file_dialog = FileDialogBuilder::new();

    // Set the title of the file dialog:
    let file_dialog = file_dialog.set_title(&payload.title);

    // Set the file type filter if provided:
    let file_dialog = match &payload.filter {
        Some(filter) => {
            file_dialog.add_filter(&filter.filter_name, &filter.filter_extensions.iter().map(|s| s.as_str()).collect::<Vec<&str>>())
        },

        None => file_dialog,
    };

    // Set the previous file path if provided:
    let file_dialog = match &payload.previous_file {
        Some(previous) => {
            let previous_path = previous.file_path.as_str();
            file_dialog.set_directory(previous_path)
        },

        None => file_dialog,
    };

    // Show the file dialog and get the selected file path:
    let file_path = file_dialog.pick_file();
    match file_path {
        Some(path) => {
            info!("User selected file: {path:?}");
            Json(FileSelectionResponse {
                user_cancelled: false,
                selected_file_path: path.to_str().unwrap().to_string(),
            })
        },

        None => {
            info!("User cancelled file selection.");
            Json(FileSelectionResponse {
                user_cancelled: true,
                selected_file_path: String::from(""),
            })
        },
    }
}

#[post("/save/file", data = "<payload>")]
pub fn save_file(_token: APIToken, payload: Json<SaveFileOptions>) -> Json<FileSaveResponse> {

    // Create a new file dialog builder:
    let file_dialog = FileDialogBuilder::new();

    // Set the title of the file dialog:
    let file_dialog = file_dialog.set_title(&payload.title);

    // Set the file type filter if provided:
    let file_dialog = match &payload.filter {
        Some(filter) => {
            file_dialog.add_filter(&filter.filter_name, &filter.filter_extensions.iter().map(|s| s.as_str()).collect::<Vec<&str>>())
        },

        None => file_dialog,
    };

    // Set the previous file path if provided:
    let file_dialog = match &payload.name_file {
        Some(previous) => {
            let previous_path = previous.file_path.as_str();
            file_dialog.set_directory(previous_path)
        },

        None => file_dialog,
    };

    // Displays the file dialogue box and select the file:
    let file_path = file_dialog.save_file();
    match file_path {
        Some(path) => {
            info!("User selected file for writing operation: {path:?}");
            Json(FileSaveResponse {
                user_cancelled: false,
                save_file_path: path.to_str().unwrap().to_string(),
            })
        },

        None => {
            info!("User cancelled file selection.");
            Json(FileSaveResponse {
                user_cancelled: true,
                save_file_path: String::from(""),
            })
        },
    }
}

#[derive(Clone, Deserialize)]
pub struct PreviousFile {
    file_path: String,
}

#[derive(Serialize)]
pub struct FileSelectionResponse {
    user_cancelled: bool,
    selected_file_path: String,
}
#[derive(Serialize)]
pub struct FileSaveResponse {
    user_cancelled: bool,
    save_file_path: String,
}

fn set_pdfium_path(path_resolver: PathResolver) {
    let pdfium_relative_source_path = String::from("resources/libraries/");
    let pdfium_source_path = path_resolver.resolve_resource(pdfium_relative_source_path);
    if pdfium_source_path.is_none() {
        error!(Source = "Bootloader Tauri"; "Failed to set the PDFium library path.");
        return;
    }

    let pdfium_source_path = pdfium_source_path.unwrap();
    let pdfium_source_path = pdfium_source_path.to_str().unwrap().to_string();
    *PDFIUM_LIB_PATH.lock().unwrap() = Some(pdfium_source_path.clone());
}