use crate::{
    commands,
    keymap::{self, Keymaps},
};
use clap::ArgMatches as Args;
use helix_core::{indent::TAB_WIDTH, syntax::HighlightEvent, Position, Range, State};

use helix_view::{document::Mode, Document, Editor, Theme, View};

use crate::compositor::{Component, Compositor, EventResult};
use crate::prompt::Prompt;

use log::{debug, info};

use std::{
    borrow::Cow,
    io::{self, stdout, Stdout, Write},
    path::PathBuf,
    time::Duration,
};

use smol::prelude::*;

use anyhow::Error;

use crossterm::{
    cursor,
    event::{read, Event, EventStream, KeyCode, KeyEvent},
    execute, queue,
    terminal::{self, disable_raw_mode, enable_raw_mode},
};

use tui::{
    backend::CrosstermBackend,
    buffer::Buffer as Surface,
    layout::Rect,
    style::{Color, Modifier, Style},
};

type Terminal = tui::Terminal<CrosstermBackend<std::io::Stdout>>;

const BASE_WIDTH: u16 = 30;

pub struct Application<'a> {
    compositor: Compositor,
    editor: Editor,
    renderer: Renderer,

    executor: &'a smol::Executor<'a>,
    language_server: helix_lsp::Client,
}

pub struct Renderer {
    size: (u16, u16),
    terminal: Terminal,
    surface: Surface,
    cache: Surface,
    text_color: Style,
}

impl Renderer {
    pub fn new() -> Result<Self, Error> {
        let backend = CrosstermBackend::new(stdout());
        let mut terminal = Terminal::new(backend)?;
        let size = terminal::size().unwrap();
        let text_color: Style = Style::default().fg(Color::Rgb(219, 191, 239)); // lilac

        let area = Rect::new(0, 0, size.0, size.1);

        Ok(Self {
            size,
            terminal,
            surface: Surface::empty(area),
            cache: Surface::empty(area),
            text_color,
        })
    }

    pub fn resize(&mut self, width: u16, height: u16) {
        self.size = (width, height);
        let area = Rect::new(0, 0, width, height);
        self.surface = Surface::empty(area);
        self.cache = Surface::empty(area);
    }

    pub fn render_view(&mut self, view: &mut View, viewport: Rect, theme: &Theme) {
        self.render_buffer(view, viewport, theme);
        self.render_statusline(view, theme);
    }

    // TODO: ideally not &mut View but highlights require it because of cursor cache
    pub fn render_buffer(&mut self, view: &mut View, viewport: Rect, theme: &Theme) {
        let area = Rect::new(0, 0, self.size.0, self.size.1);

        //  clear with background color
        self.surface.set_style(area, theme.get("ui.background"));

        // TODO: inefficient, should feed chunks.iter() to tree_sitter.parse_with(|offset, pos|)
        let source_code = view.doc.text().to_string();

        let last_line = view.last_line();

        let range = {
            // calculate viewport byte ranges
            let start = view.doc.text().line_to_byte(view.first_line);
            let end = view.doc.text().line_to_byte(last_line)
                + view.doc.text().line(last_line).len_bytes();

            start..end
        };

        // TODO: range doesn't actually restrict source, just highlight range
        // TODO: cache highlight results
        // TODO: only recalculate when state.doc is actually modified
        let highlights: Vec<_> = match view.doc.syntax.as_mut() {
            Some(syntax) => {
                syntax
                    .highlight_iter(source_code.as_bytes(), Some(range), None, |_| None)
                    .unwrap()
                    .collect() // TODO: we collect here to avoid double borrow, fix later
            }
            None => vec![Ok(HighlightEvent::Source {
                start: range.start,
                end: range.end,
            })],
        };
        let mut spans = Vec::new();
        let mut visual_x = 0;
        let mut line = 0u16;
        let visible_selections: Vec<Range> = view
            .doc
            .state
            .selection()
            .ranges()
            .iter()
            // TODO: limit selection to one in viewport
            // .filter(|range| !range.is_empty()) // && range.overlaps(&Range::new(start, end + 1))
            .copied()
            .collect();

        'outer: for event in highlights {
            match event.unwrap() {
                HighlightEvent::HighlightStart(span) => {
                    spans.push(span);
                }
                HighlightEvent::HighlightEnd => {
                    spans.pop();
                }
                HighlightEvent::Source { start, end } => {
                    // TODO: filter out spans out of viewport for now..

                    let start = view.doc.text().byte_to_char(start);
                    let end = view.doc.text().byte_to_char(end); // <-- index 744, len 743

                    let text = view.doc.text().slice(start..end);

                    use helix_core::graphemes::{grapheme_width, RopeGraphemes};

                    let style = match spans.first() {
                        Some(span) => theme.get(theme.scopes()[span.0].as_str()),
                        None => Style::default().fg(Color::Rgb(164, 160, 232)), // lavender
                    };

                    // TODO: we could render the text to a surface, then cache that, that
                    // way if only the selection/cursor changes we can copy from cache
                    // and paint the new cursor.

                    let mut char_index = start;

                    // iterate over range char by char
                    for grapheme in RopeGraphemes::new(&text) {
                        // TODO: track current char_index

                        if grapheme == "\n" {
                            visual_x = 0;
                            line += 1;

                            // TODO: with proper iter this shouldn't be necessary
                            if line >= viewport.height {
                                break 'outer;
                            }
                        } else if grapheme == "\t" {
                            visual_x += (TAB_WIDTH as u16);
                        } else {
                            // Cow will prevent allocations if span contained in a single slice
                            // which should really be the majority case
                            let grapheme = Cow::from(grapheme);
                            let width = grapheme_width(&grapheme) as u16;

                            // TODO: this should really happen as an after pass
                            let style = if visible_selections
                                .iter()
                                .any(|range| range.contains(char_index))
                            {
                                // cedar
                                style.clone().bg(Color::Rgb(128, 47, 0))
                            } else {
                                style
                            };

                            let style = if visible_selections
                                .iter()
                                .any(|range| range.head == char_index)
                            {
                                style.clone().bg(Color::Rgb(255, 255, 255))
                            } else {
                                style
                            };

                            // ugh, improve with a traverse method
                            // or interleave highlight spans with selection and diagnostic spans
                            let style = if view.doc.diagnostics.iter().any(|diagnostic| {
                                diagnostic.range.0 <= char_index && diagnostic.range.1 > char_index
                            }) {
                                style.clone().add_modifier(Modifier::UNDERLINED)
                            } else {
                                style
                            };

                            // TODO: paint cursor heads except primary

                            self.surface.set_string(
                                viewport.x + visual_x,
                                viewport.y + line,
                                grapheme,
                                style,
                            );

                            visual_x += width;
                        }

                        char_index += 1;
                    }
                }
            }
        }

        let style: Style = theme.get("ui.linenr");
        let warning: Style = theme.get("warning");
        let last_line = view.last_line();
        for (i, line) in (view.first_line..last_line).enumerate() {
            if view.doc.diagnostics.iter().any(|d| d.line == line) {
                self.surface.set_stringn(0, i as u16, "●", 1, warning);
            }

            self.surface
                .set_stringn(1, i as u16, format!("{:>5}", line + 1), 5, style);
        }
    }

    pub fn render_statusline(&mut self, view: &View, theme: &Theme) {
        let mode = match view.doc.mode() {
            Mode::Insert => "INS",
            Mode::Normal => "NOR",
            Mode::Goto => "GOTO",
        };
        // statusline
        self.surface.set_style(
            Rect::new(0, self.size.1 - 2, self.size.0, 1),
            theme.get("ui.statusline"),
        );
        self.surface
            .set_string(1, self.size.1 - 2, mode, self.text_color);

        if let Some(path) = view.doc.path() {
            self.surface
                .set_string(6, self.size.1 - 2, path.to_string_lossy(), self.text_color);
        }

        self.surface.set_string(
            self.size.0 - 10,
            self.size.1 - 2,
            format!("{}", view.doc.diagnostics.len()),
            self.text_color,
        );
    }

    pub fn render_prompt(&mut self, prompt: &Prompt, theme: &Theme) {
        // completion
        if !prompt.completion.is_empty() {
            // TODO: find out better way of clearing individual lines of the screen
            let mut row = 0;
            let mut col = 0;
            let max_col = self.size.0 / BASE_WIDTH;
            let col_height = ((prompt.completion.len() as u16 + max_col - 1) / max_col);

            for i in (3..col_height + 3) {
                self.surface.set_string(
                    0,
                    self.size.1 - i as u16,
                    " ".repeat(self.size.0 as usize),
                    self.text_color,
                );
            }
            self.surface.set_style(
                Rect::new(0, self.size.1 - col_height - 2, self.size.0, col_height),
                theme.get("ui.statusline"),
            );
            for (i, command) in prompt.completion.iter().enumerate() {
                let color = if prompt.completion_selection_index.is_some()
                    && i == prompt.completion_selection_index.unwrap()
                {
                    Style::default().bg(Color::Rgb(104, 060, 232))
                } else {
                    self.text_color
                };
                self.surface.set_stringn(
                    1 + col * BASE_WIDTH,
                    self.size.1 - col_height - 2 + row,
                    &command,
                    BASE_WIDTH as usize - 1,
                    color,
                );
                row += 1;
                if row > col_height - 1 {
                    row = 0;
                    col += 1;
                }
                if col > max_col {
                    break;
                }
            }
        }
        // render buffer text
        self.surface
            .set_string(1, self.size.1 - 1, &prompt.prompt, self.text_color);
        self.surface
            .set_string(2, self.size.1 - 1, &prompt.line, self.text_color);
    }

    pub fn draw_and_swap(&mut self) {
        use tui::backend::Backend;
        // TODO: theres probably a better place for this
        self.terminal
            .backend_mut()
            .draw(self.cache.diff(&self.surface).into_iter());
        // swap the buffer
        std::mem::swap(&mut self.surface, &mut self.cache);
    }

    pub fn render_cursor(&mut self, view: &View, prompt: Option<&Prompt>, viewport: Rect) {
        let mut stdout = stdout();
        match view.doc.mode() {
            Mode::Insert => write!(stdout, "\x1B[6 q"),
            mode => write!(stdout, "\x1B[2 q"),
        };
        let pos = if let Some(prompt) = prompt {
            Position::new(self.size.0 as usize, 2 + prompt.cursor)
        } else {
            let cursor = view.doc.state.selection().cursor();

            let mut pos = view
                .screen_coords_at_pos(&view.doc.text().slice(..), cursor)
                .expect("Cursor is out of bounds.");
            pos.col += viewport.x as usize;
            pos.row += viewport.y as usize;
            pos
        };

        execute!(stdout, cursor::MoveTo(pos.col as u16, pos.row as u16));
    }
}

struct EditorView {
    keymap: Keymaps,
}

impl EditorView {
    fn new() -> Self {
        Self {
            keymap: keymap::default(),
        }
    }
}

use crate::compositor::Context;

impl Component for EditorView {
    fn handle_event(&mut self, event: Event, cx: &mut Context) -> EventResult {
        match event {
            Event::Resize(width, height) => {
                // TODO: simplistic ensure cursor in view for now
                // TODO: loop over views
                if let Some(view) = cx.editor.view_mut() {
                    view.size = (width, height);
                    view.ensure_cursor_in_view()
                };
                EventResult::Consumed(None)
            }
            Event::Key(event) => {
                if let Some(view) = cx.editor.view_mut() {
                    let keys = vec![event];
                    // TODO: sequences (`gg`)
                    let mode = view.doc.mode();
                    // TODO: handle count other than 1
                    let mut cx = commands::Context {
                        view,
                        executor: cx.executor,
                        count: 1,
                        callback: None,
                    };

                    match mode {
                        Mode::Insert => {
                            if let Some(command) = self.keymap[&Mode::Insert].get(&keys) {
                                command(&mut cx);
                            } else if let KeyEvent {
                                code: KeyCode::Char(c),
                                ..
                            } = event
                            {
                                commands::insert::insert_char(&mut cx, c);
                            }
                        }
                        Mode::Normal => {
                            if let Some(command) = self.keymap[&Mode::Normal].get(&keys) {
                                command(&mut cx);

                                // TODO: simplistic ensure cursor in view for now
                            }
                        }
                        mode => {
                            if let Some(command) = self.keymap[&mode].get(&keys) {
                                command(&mut cx);

                                // TODO: simplistic ensure cursor in view for now
                            }
                        }
                    }
                    // appease borrowck
                    let callback = cx.callback.take();

                    view.ensure_cursor_in_view();

                    EventResult::Consumed(callback)
                } else {
                    EventResult::Ignored
                }
            }
            Event::Mouse(_) => EventResult::Ignored,
        }
    }
    fn render(&mut self, renderer: &mut Renderer, cx: &mut Context) {
        const OFFSET: u16 = 7; // 1 diagnostic + 5 linenr + 1 gutter
        let viewport = Rect::new(OFFSET, 0, renderer.size.0, renderer.size.1 - 2); // - 2 for statusline and prompt

        // SAFETY: we cheat around the view_mut() borrow because it doesn't allow us to also borrow
        // theme. Theme is immutable mutating view won't disrupt theme_ref.
        let theme_ref = unsafe { &*(&cx.editor.theme as *const Theme) };
        if let Some(view) = cx.editor.view_mut() {
            renderer.render_view(view, viewport, theme_ref);
        }

        // TODO: drop unwrap
        renderer.render_cursor(cx.editor.view().unwrap(), None, viewport);
    }
}

impl<'a> Application<'a> {
    pub fn new(mut args: Args, executor: &'a smol::Executor<'a>) -> Result<Self, Error> {
        let renderer = Renderer::new()?;
        let mut editor = Editor::new();

        if let Some(file) = args.values_of_t::<PathBuf>("files").unwrap().pop() {
            editor.open(file, renderer.size)?;
        }

        let mut compositor = Compositor::new();
        compositor.push(Box::new(EditorView::new()));

        let language_server = helix_lsp::Client::start(&executor, "rust-analyzer", &[]);

        let mut app = Self {
            editor,
            renderer,
            // TODO; move to state
            compositor,

            executor,
            language_server,
        };

        Ok(app)
    }

    fn render(&mut self) {
        self.renderer.surface.reset(); // reset is faster than allocating new empty surface
        let mut cx = crate::compositor::Context {
            editor: &mut self.editor,
            executor: &self.executor,
        };
        self.compositor.render(&mut self.renderer, &mut cx); // viewport,
        self.renderer.draw_and_swap();
    }

    pub async fn event_loop(&mut self) {
        let mut reader = EventStream::new();

        // initialize lsp
        self.language_server.initialize().await.unwrap();
        // TODO: temp
        // self.language_server
        //     .text_document_did_open(&cx.editor.view().unwrap().doc)
        //     .await
        //     .unwrap();

        self.render();

        loop {
            if self.editor.should_close {
                break;
            }

            use futures_util::{select, FutureExt};
            select! {
                event = reader.next().fuse() => {
                    self.handle_terminal_events(event)
                }
                call = self.language_server.incoming.next().fuse() => {
                    self.handle_language_server_message(call).await
                }
            }
        }
    }

    pub fn handle_terminal_events(&mut self, event: Option<Result<Event, crossterm::ErrorKind>>) {
        let mut cx = crate::compositor::Context {
            editor: &mut self.editor,
            executor: &self.executor,
        };
        // Handle key events
        let should_redraw = match event {
            Some(Ok(Event::Resize(width, height))) => {
                self.renderer.resize(width, height);

                self.compositor
                    .handle_event(Event::Resize(width, height), &mut cx)
            }
            Some(Ok(event)) => self.compositor.handle_event(event, &mut cx),
            Some(Err(x)) => panic!(x),
            None => panic!(),
        };

        if should_redraw {
            self.render();
        }
    }

    pub async fn handle_language_server_message(&mut self, call: Option<helix_lsp::Call>) {
        use helix_lsp::{Call, Notification};
        match call {
            Some(Call::Notification(helix_lsp::jsonrpc::Notification {
                method, params, ..
            })) => {
                let notification = Notification::parse(&method, params);
                match notification {
                    Notification::PublishDiagnostics(params) => {
                        let path = Some(params.uri.to_file_path().unwrap());
                        let view: Option<&mut helix_view::View> = None;
                        // TODO:
                        // let view = self
                        //     .editor
                        //     .views
                        //     .iter_mut()
                        //     .find(|view| view.doc.path == path);

                        if let Some(view) = view {
                            let doc = view.doc.text().slice(..);
                            let diagnostics = params
                                .diagnostics
                                .into_iter()
                                .map(|diagnostic| {
                                    use helix_lsp::util::lsp_pos_to_pos;
                                    let start = lsp_pos_to_pos(&doc, diagnostic.range.start);
                                    let end = lsp_pos_to_pos(&doc, diagnostic.range.end);

                                    helix_core::Diagnostic {
                                        range: (start, end),
                                        line: diagnostic.range.start.line as usize,
                                        message: diagnostic.message,
                                        // severity
                                        // code
                                        // source
                                    }
                                })
                                .collect();

                            view.doc.diagnostics = diagnostics;

                            // TODO: we want to process all the events in queue, then render. publishDiagnostic tends to send a whole bunch of events
                            self.render();
                        }
                    }
                    _ => unreachable!(),
                }
            }
            Some(Call::MethodCall(call)) => {
                debug!("Method not found {}", call.method);

                self.language_server.reply(
                    call.id,
                    // TODO: make a Into trait that can cast to Err(jsonrpc::Error)
                    Err(helix_lsp::jsonrpc::Error {
                        code: helix_lsp::jsonrpc::ErrorCode::MethodNotFound,
                        message: "Method not found".to_string(),
                        data: None,
                    }),
                );
            }
            _ => unreachable!(),
        }
    }

    pub async fn run(&mut self) -> Result<(), Error> {
        enable_raw_mode()?;

        let mut stdout = stdout();

        execute!(stdout, terminal::EnterAlternateScreen)?;

        // Exit the alternate screen and disable raw mode before panicking
        let hook = std::panic::take_hook();
        std::panic::set_hook(Box::new(move |info| {
            execute!(std::io::stdout(), terminal::LeaveAlternateScreen);
            disable_raw_mode();
            hook(info);
        }));

        self.event_loop().await;

        // reset cursor shape
        write!(stdout, "\x1B[2 q");

        execute!(stdout, terminal::LeaveAlternateScreen)?;

        disable_raw_mode()?;

        Ok(())
    }
}

// TODO: language configs:
// tabSize, fileExtension etc, mapping to tree sitter parser
// themes:
// map tree sitter highlights to color values
//
// TODO: expand highlight thing so we're able to render only viewport range
// TODO: async: maybe pre-cache scopes as empty so we render all graphemes initially as regular
////text until calc finishes
// TODO: scope matching: biggest union match? [string] & [html, string], [string, html] & [ string, html]
// can do this by sorting our theme matches based on array len (longest first) then stopping at the
// first rule that matches (rule.all(|scope| scopes.contains(scope)))