use std::{
    io::{self, Write},
    time::Duration,
};

use futures_lite::StreamExt;
use tui::layout::Rect;

use crate::{
    render::tui::{draw, ticker},
    Root, Throughput, WeakRoot,
};

/// Configure the terminal user interface
#[derive(Clone)]
pub struct Options {
    /// The initial title to show for the whole window.
    ///
    /// Can be adjusted later by sending `Event::SetTitle(…)`
    /// into the event stream, see see [`tui::render_with_input(…events)`](./fn.render_with_input.html) function.
    pub title: String,
    /// The amount of frames to draw per second. If below 1.0, it determines the amount of seconds between the frame.
    ///
    /// *e.g.* 1.0/4.0 is one frame every 4 seconds.
    pub frames_per_second: f32,

    /// If true, (default false), we will keep track of the previous progress state to derive
    /// continuous throughput information from. Throughput will only show for units which have
    /// explicitly enabled it, it is opt-in.
    ///
    /// This comes at the cost of additional memory and CPU time.
    pub throughput: bool,

    /// If set, recompute the column width of the task tree only every given frame. Otherwise the width will be recomputed every frame.
    ///
    /// Use this if there are many short-running tasks with varying names paired with high refresh rates of multiple frames per second to
    /// stabilize the appearance of the TUI.
    ///
    /// For example, setting the value to 40 will with a frame rate of 20 per second will recompute the column width to fit all task names
    /// every 2 seconds.
    pub recompute_column_width_every_nth_frame: Option<usize>,
    /// The initial window size.
    ///
    /// If unset, it will be retrieved from the current terminal.
    pub window_size: Option<Rect>,

    /// If true (default: true), we will stop running the TUI once the progress isn't available anymore (went out of scope).
    pub stop_if_progress_missing: bool,
}

impl Default for Options {
    fn default() -> Self {
        Options {
            title: "Progress Dashboard".into(),
            frames_per_second: 10.0,
            throughput: false,
            recompute_column_width_every_nth_frame: None,
            window_size: None,
            stop_if_progress_missing: true,
        }
    }
}

/// A line as used in [`Event::SetInformation`](./enum.Event.html#variant.SetInformation)
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Line {
    /// Set a title with the given text
    Title(String),
    /// Set a line of text with the given content
    Text(String),
}

/// The variants represented here allow the user to control when the GUI can be shutdown.
#[derive(Debug, Clone, Copy)]
pub enum Interrupt {
    /// Immediately exit the GUI event loop when there is an interrupt request.
    ///
    /// This is the default when the event loop is entered.
    Instantly,
    /// Instead of exiting the event loop instantly, wait until the next Interrupt::Instantly
    /// event is coming in.
    Deferred,
}

#[derive(Clone, Copy)]
pub(crate) enum InterruptDrawInfo {
    Instantly,
    /// Boolean signals if interrupt is requested
    Deferred(bool),
}

#[cfg(not(any(feature = "render-tui-crossterm")))]
compile_error!("Please set the 'render-tui-crossterm' feature when using the 'render-tui'");

use crosstermion::crossterm::event::{KeyCode, KeyEventKind, KeyModifiers};
use crosstermion::{
    input::{key_input_stream, Key},
    terminal::{tui::new_terminal, AlternateRawScreen},
};

/// An event to be sent in the [`tui::render_with_input(…events)`](./fn.render_with_input.html) stream.
///
/// This way, the TUI can be instructed to draw frames or change the information to be displayed.
#[derive(Debug, Clone)]
pub enum Event {
    /// Draw a frame
    Tick,
    /// Send any key - can be used to simulate user input, and is typically generated by the TUI's own input loop.
    Input(Key),
    /// Change the size of the window to the given rectangle.
    ///
    /// Useful to embed the TUI into other terminal user interfaces that can resize dynamically.
    SetWindowSize(Rect),
    /// Set the title of the progress dashboard
    SetTitle(String),
    /// Provide a list of titles and lines to populate the side bar on the right.
    SetInformation(Vec<Line>),
    /// The way the GUI will respond to interrupt requests. See `Interrupt` for more information.
    SetInterruptMode(Interrupt),
}

/// Returns a future that draws the terminal user interface indefinitely.
///
/// * `progress` is the progress tree whose information to visualize.
///   It will usually be changing constantly while the TUI holds it.
/// * `options` are configuring the TUI.
/// * `events` is a stream of `Event`s which manipulate the TUI while it is running
///
/// Failure may occour if there is no terminal to draw into.
pub fn render_with_input(
    out: impl std::io::Write,
    progress: impl WeakRoot,
    options: Options,
    events: impl futures_core::Stream<Item = Event> + Send + Unpin,
) -> Result<impl std::future::Future<Output = ()>, std::io::Error> {
    let Options {
        title,
        frames_per_second,
        window_size,
        recompute_column_width_every_nth_frame,
        throughput,
        stop_if_progress_missing,
    } = options;
    let mut terminal = new_terminal(AlternateRawScreen::try_from(out)?)?;
    terminal.hide_cursor()?;

    let duration_per_frame = Duration::from_secs_f32(1.0 / frames_per_second);
    let key_receive = key_input_stream();

    let render_fut = async move {
        let mut state = draw::State {
            title,
            duration_per_frame,
            ..draw::State::default()
        };
        if throughput {
            state.throughput = Some(Throughput::default());
        }
        let mut interrupt_mode = InterruptDrawInfo::Instantly;
        let (entries_cap, messages_cap) = progress
            .upgrade()
            .map(|p| (p.num_tasks(), p.messages_capacity()))
            .unwrap_or_default();
        let mut entries = Vec::with_capacity(entries_cap);
        let mut messages = Vec::with_capacity(messages_cap);
        let mut events = ticker(duration_per_frame)
            .map(|_| Event::Tick)
            .or(key_receive.map(Event::Input))
            .or(events);

        let mut tick = 0usize;
        let store_task_size_every = recompute_column_width_every_nth_frame.unwrap_or(1).max(1);
        while let Some(event) = events.next().await {
            let mut skip_redraw = false;
            match event {
                Event::Tick => {}
                Event::Input(key) if key.kind != KeyEventKind::Release => match key.code {
                    KeyCode::Char('c') | KeyCode::Char('[') if key.modifiers.contains(KeyModifiers::CONTROL) => {
                        match interrupt_mode {
                            InterruptDrawInfo::Instantly => break,
                            InterruptDrawInfo::Deferred(_) => interrupt_mode = InterruptDrawInfo::Deferred(true),
                        }
                    }
                    KeyCode::Esc | KeyCode::Char('q') => match interrupt_mode {
                        InterruptDrawInfo::Instantly => break,
                        InterruptDrawInfo::Deferred(_) => interrupt_mode = InterruptDrawInfo::Deferred(true),
                    },
                    KeyCode::Char('`') => state.hide_messages = !state.hide_messages,
                    KeyCode::Char('~') => state.messages_fullscreen = !state.messages_fullscreen,
                    KeyCode::Char('J') => state.message_offset = state.message_offset.saturating_add(1),
                    KeyCode::Char('D') => state.message_offset = state.message_offset.saturating_add(10),
                    KeyCode::Char('j') => state.task_offset = state.task_offset.saturating_add(1),
                    KeyCode::Char('d') => state.task_offset = state.task_offset.saturating_add(10),
                    KeyCode::Char('K') => state.message_offset = state.message_offset.saturating_sub(1),
                    KeyCode::Char('U') => state.message_offset = state.message_offset.saturating_sub(10),
                    KeyCode::Char('k') => state.task_offset = state.task_offset.saturating_sub(1),
                    KeyCode::Char('u') => state.task_offset = state.task_offset.saturating_sub(10),
                    KeyCode::Char('[') => state.hide_info = !state.hide_info,
                    KeyCode::Char('{') => state.maximize_info = !state.maximize_info,
                    _ => skip_redraw = true,
                },
                Event::Input(_) => skip_redraw = true,
                Event::SetWindowSize(bound) => state.user_provided_window_size = Some(bound),
                Event::SetTitle(title) => state.title = title,
                Event::SetInformation(info) => state.information = info,
                Event::SetInterruptMode(mode) => {
                    interrupt_mode = match mode {
                        Interrupt::Instantly => {
                            if let InterruptDrawInfo::Deferred(true) = interrupt_mode {
                                break;
                            }
                            InterruptDrawInfo::Instantly
                        }
                        Interrupt::Deferred => InterruptDrawInfo::Deferred(match interrupt_mode {
                            InterruptDrawInfo::Deferred(interrupt_requested) => interrupt_requested,
                            _ => false,
                        }),
                    };
                }
            }
            if !skip_redraw {
                tick += 1;

                let progress = match progress.upgrade() {
                    Some(progress) => progress,
                    None if stop_if_progress_missing => break,
                    None => continue,
                };
                progress.sorted_snapshot(&mut entries);
                if stop_if_progress_missing && entries.is_empty() {
                    break;
                }
                let terminal_window_size = terminal.pre_render().expect("pre-render to work");
                let window_size = state
                    .user_provided_window_size
                    .or(window_size)
                    .unwrap_or(terminal_window_size);
                let buf = terminal.current_buffer_mut();
                if !state.hide_messages {
                    progress.copy_messages(&mut messages);
                }

                draw::all(&mut state, interrupt_mode, &entries, &messages, window_size, buf);
                if tick == 1 || tick % store_task_size_every == 0 || state.last_tree_column_width.unwrap_or(0) == 0 {
                    state.next_tree_column_width = state.last_tree_column_width;
                }
                terminal.post_render().expect("post render to work");
            }
        }
        // Make sure the terminal responds right away when this future stops, to reset back to the 'non-alternate' buffer
        drop(terminal);
        io::stdout().flush().ok();
    };
    Ok(render_fut)
}

/// An easy-to-use version of `render_with_input(…)` that does not allow state manipulation via an event stream.
pub fn render(
    out: impl std::io::Write,
    progress: impl WeakRoot,
    config: Options,
) -> Result<impl std::future::Future<Output = ()>, std::io::Error> {
    render_with_input(out, progress, config, futures_lite::stream::pending())
}
