// SPDX-License-Identifier: GPL-3.0-only

use cosmic::{
    iced::{
        event::{Event, Status},
        keyboard::{Event as KeyEvent, KeyCode, Modifiers},
        mouse::{self, Button, Event as MouseEvent, ScrollDelta},
        Color, Element, Length, Padding, Rectangle, Size,
    },
    iced_core::{
        clipboard::Clipboard,
        image,
        layout::{self, Layout},
        renderer,
        widget::{self, tree, Widget},
        Shell,
    },
    theme::{Theme, ThemeType},
};
use cosmic_text::{Action, Edit, Metrics};
use std::{cell::Cell, cmp, sync::Mutex, time::Instant};

use crate::{FONT_SYSTEM, SWASH_CACHE};

pub struct Appearance {
    background_color: Option<Color>,
    text_color: Color,
}

pub trait StyleSheet {
    fn appearance(&self) -> Appearance;
}

impl StyleSheet for Theme {
    fn appearance(&self) -> Appearance {
        match self.theme_type {
            ThemeType::Dark | ThemeType::HighContrastDark => Appearance {
                background_color: Some(Color::from_rgb8(0x34, 0x34, 0x34)),
                text_color: Color::from_rgb8(0xFF, 0xFF, 0xFF),
            },
            ThemeType::Light | ThemeType::HighContrastLight => Appearance {
                background_color: Some(Color::from_rgb8(0xFC, 0xFC, 0xFC)),
                text_color: Color::from_rgb8(0x00, 0x00, 0x00),
            },
            //TODO: what to return for these?
            _ => Appearance {
                background_color: Some(Color::from_rgb8(0x34, 0x34, 0x34)),
                text_color: Color::from_rgb8(0xFF, 0xFF, 0xFF),
            },
        }
    }
}

pub struct TextBox<'a, Editor> {
    editor: &'a Mutex<Editor>,
    padding: Padding,
}

impl<'a, Editor> TextBox<'a, Editor> {
    pub fn new(editor: &'a Mutex<Editor>) -> Self {
        Self {
            editor,
            padding: Padding::new(0.0),
        }
    }

    pub fn padding<P: Into<Padding>>(mut self, padding: P) -> Self {
        self.padding = padding.into();
        self
    }
}

pub fn text_box<'a, Editor>(editor: &'a Mutex<Editor>) -> TextBox<'a, Editor> {
    TextBox::new(editor)
}

//TODO: improve performance
fn draw_rect(
    buffer: &mut [u32],
    image_w: i32,
    image_h: i32,
    start_x: i32,
    start_y: i32,
    w: i32,
    h: i32,
    color: u32,
) {
    let alpha = (color >> 24) & 0xFF;
    if alpha == 0 {
        // Do not draw if alpha is zero
        return;
    } else if alpha >= 255 {
        // Handle overwrite
        for y in start_y..start_y + h {
            if y < 0 || y >= image_h {
                // Skip if y out of bounds
                continue;
            }

            let line_offset = y as usize * image_w as usize;
            for x in start_x..start_x + w {
                if x < 0 || x >= image_w {
                    // Skip if x out of bounds
                    continue;
                }

                let offset = line_offset + x as usize;
                buffer[offset] = color;
            }
        }
    } else {
        let n_alpha = 255 - alpha;
        for y in start_y..start_y + h {
            if y < 0 || y >= image_h {
                // Skip if y out of bounds
                continue;
            }

            let line_offset = y as usize * image_w as usize;
            for x in start_x..start_x + w {
                if x < 0 || x >= image_w {
                    // Skip if x out of bounds
                    continue;
                }

                // Alpha blend with current value
                let offset = line_offset + x as usize;
                let current = buffer[offset];
                let rb = ((n_alpha * (current & 0x00FF00FF)) + (alpha * (color & 0x00FF00FF))) >> 8;
                let ag = (n_alpha * ((current & 0xFF00FF00) >> 8))
                    + (alpha * (0x01000000 | ((color & 0x0000FF00) >> 8)));
                buffer[offset] = (rb & 0x00FF00FF) | (ag & 0xFF00FF00);
            }
        }
    }
}

impl<'a, 'editor, Editor, Message, Renderer> Widget<Message, Renderer> for TextBox<'a, Editor>
where
    Renderer: renderer::Renderer + image::Renderer<Handle = image::Handle>,
    Renderer::Theme: StyleSheet,
    Editor: Edit,
{
    fn tag(&self) -> tree::Tag {
        tree::Tag::of::<State>()
    }

    fn state(&self) -> tree::State {
        tree::State::new(State::new())
    }

    fn width(&self) -> Length {
        Length::Fill
    }

    fn height(&self) -> Length {
        Length::Fill
    }

    fn layout(&self, _renderer: &Renderer, limits: &layout::Limits) -> layout::Node {
        let limits = limits.width(Length::Fill).height(Length::Fill);

        //TODO: allow lazy shape
        let mut editor = self.editor.lock().unwrap();
        editor
            .borrow_with(&mut FONT_SYSTEM.lock().unwrap())
            .buffer_mut()
            .shape_until(i32::max_value());

        let mut layout_lines = 0;
        for line in editor.buffer().lines.iter() {
            match line.layout_opt() {
                Some(layout) => layout_lines += layout.len(),
                None => (),
            }
        }

        let height = layout_lines as f32 * editor.buffer().metrics().line_height;
        let size = Size::new(limits.max().width, height);

        layout::Node::new(limits.resolve(size))
    }

    fn mouse_interaction(
        &self,
        _tree: &widget::Tree,
        layout: Layout<'_>,
        cursor_position: mouse::Cursor,
        _viewport: &Rectangle,
        _renderer: &Renderer,
    ) -> mouse::Interaction {
        if cursor_position.is_over(layout.bounds()) {
            mouse::Interaction::Text
        } else {
            mouse::Interaction::Idle
        }
    }

    fn draw(
        &self,
        tree: &widget::Tree,
        renderer: &mut Renderer,
        theme: &Renderer::Theme,
        style: &renderer::Style,
        layout: Layout<'_>,
        _cursor_position: mouse::Cursor,
        viewport: &Rectangle,
    ) {
        let instant = Instant::now();

        let state = tree.state.downcast_ref::<State>();

        let appearance = theme.appearance();

        if let Some(background_color) = appearance.background_color {
            renderer.fill_quad(
                renderer::Quad {
                    bounds: layout.bounds(),
                    border_radius: 0.0.into(),
                    border_width: 0.0,
                    border_color: Color::TRANSPARENT,
                },
                background_color,
            );
        }

        let text_color = cosmic_text::Color::rgba(
            cmp::max(0, cmp::min(255, (appearance.text_color.r * 255.0) as i32)) as u8,
            cmp::max(0, cmp::min(255, (appearance.text_color.g * 255.0) as i32)) as u8,
            cmp::max(0, cmp::min(255, (appearance.text_color.b * 255.0) as i32)) as u8,
            cmp::max(0, cmp::min(255, (appearance.text_color.a * 255.0) as i32)) as u8,
        );

        let mut editor = self.editor.lock().unwrap();

        let view_w = cmp::min(viewport.width as i32, layout.bounds().width as i32)
            - self.padding.horizontal() as i32;
        let view_h = cmp::min(viewport.height as i32, layout.bounds().height as i32)
            - self.padding.vertical() as i32;

        let scale_factor = style.scale_factor;

        let image_w = (view_w as f64 * scale_factor) as i32;
        let image_h = (view_h as f64 * scale_factor) as i32;
        let scrollbar_w = (8.0 * scale_factor) as i32;

        if image_w <= scrollbar_w || image_h <= 0 {
            // Zero sized image
            return;
        }

        let mut font_system = FONT_SYSTEM.lock().unwrap();
        let mut editor = editor.borrow_with(&mut font_system);

        // Set metrics and size
        editor.buffer_mut().set_metrics_and_size(
            //TODO: get from config
            Metrics::new(14.0, 20.0).scale(scale_factor as f32),
            image_w as f32,
            image_h as f32,
        );

        // Shape and layout as needed
        editor.shape_as_needed();

        if editor.buffer().redraw() {
            // Draw to pixel buffer
            let mut pixels = vec![0; image_w as usize * image_h as usize * 4];
            {
                let buffer = unsafe {
                    std::slice::from_raw_parts_mut(
                        pixels.as_mut_ptr() as *mut u32,
                        pixels.len() / 4,
                    )
                };

                editor.draw(
                    &mut SWASH_CACHE.lock().unwrap(),
                    text_color,
                    |x, y, w, h, color| {
                        draw_rect(buffer, image_w, image_h, x, y, w as i32, h as i32, color.0);
                    },
                );

                // Draw scrollbar
                {
                    let mut start_line_opt = None;
                    let mut end_line = 0;
                    for run in editor.buffer().layout_runs() {
                        end_line = run.line_i;
                        if start_line_opt.is_none() {
                            start_line_opt = Some(end_line);
                        }
                    }

                    let start_line = start_line_opt.unwrap_or(end_line);
                    let lines = editor.buffer().lines.len();
                    let start_y = (start_line * image_h as usize) / lines;
                    let end_y = (end_line * image_h as usize) / lines;
                    if end_y > start_y {
                        draw_rect(
                            buffer,
                            image_w,
                            image_h,
                            image_w - scrollbar_w,
                            start_y as i32,
                            scrollbar_w,
                            (end_y - start_y) as i32,
                            0x40FFFFFF,
                        );
                    }
                }
            }

            // Clear redraw flag
            editor.buffer_mut().set_redraw(false);

            state.scale_factor.set(scale_factor);
            *state.handle.lock().unwrap() =
                image::Handle::from_pixels(image_w as u32, image_h as u32, pixels);
        }

        let handle = state.handle.lock().unwrap().clone();
        image::Renderer::draw(
            renderer,
            handle,
            Rectangle::new(
                layout.position() + [self.padding.left as f32, self.padding.top as f32].into(),
                Size::new(view_w as f32, view_h as f32),
            ),
        );

        let duration = instant.elapsed();
        log::debug!("redraw {}, {}: {:?}", view_w, view_h, duration);
    }

    fn on_event(
        &mut self,
        tree: &mut widget::Tree,
        event: Event,
        layout: Layout<'_>,
        cursor_position: mouse::Cursor,
        _renderer: &Renderer,
        _clipboard: &mut dyn Clipboard,
        _shell: &mut Shell<'_, Message>,
        _viewport: &Rectangle<f32>,
    ) -> Status {
        let state = tree.state.downcast_mut::<State>();
        let scale_factor = state.scale_factor.get() as f32;
        let mut editor = self.editor.lock().unwrap();
        let mut font_system = FONT_SYSTEM.lock().unwrap();
        let mut editor = editor.borrow_with(&mut font_system);

        let mut status = Status::Ignored;
        match event {
            Event::Keyboard(KeyEvent::KeyPressed {
                key_code,
                modifiers,
            }) => match key_code {
                KeyCode::Left => {
                    editor.action(Action::Left);
                    status = Status::Captured;
                }
                KeyCode::Right => {
                    editor.action(Action::Right);
                    status = Status::Captured;
                }
                KeyCode::Up => {
                    editor.action(Action::Up);
                    status = Status::Captured;
                }
                KeyCode::Down => {
                    editor.action(Action::Down);
                    status = Status::Captured;
                }
                KeyCode::Home => {
                    editor.action(Action::Home);
                    status = Status::Captured;
                }
                KeyCode::End => {
                    editor.action(Action::End);
                    status = Status::Captured;
                }
                KeyCode::PageUp => {
                    editor.action(Action::PageUp);
                    status = Status::Captured;
                }
                KeyCode::PageDown => {
                    editor.action(Action::PageDown);
                    status = Status::Captured;
                }
                KeyCode::Escape => {
                    editor.action(Action::Escape);
                    status = Status::Captured;
                }
                KeyCode::Enter => {
                    editor.action(Action::Enter);
                    status = Status::Captured;
                }
                KeyCode::Backspace => {
                    editor.action(Action::Backspace);
                    status = Status::Captured;
                }
                KeyCode::Delete => {
                    editor.action(Action::Delete);
                    status = Status::Captured;
                }
                KeyCode::Tab => {
                    if modifiers.shift() {
                        editor.action(Action::Unindent);
                    } else {
                        editor.action(Action::Indent);
                    }
                    status = Status::Captured;
                }
                _ => (),
            },
            Event::Keyboard(KeyEvent::ModifiersChanged(modifiers)) => {
                state.modifiers = modifiers;
            }
            Event::Keyboard(KeyEvent::CharacterReceived(character)) => {
                // Only parse keys when Super, Ctrl, and Alt are not pressed
                if !state.modifiers.logo() && !state.modifiers.control() && !state.modifiers.alt() {
                    match character {
                        '\n' | '\r' | '\t' => {}
                        _ => {
                            editor.action(Action::Insert(character));
                        }
                    }
                    status = Status::Captured;
                }
            }
            Event::Mouse(MouseEvent::ButtonPressed(Button::Left)) => {
                if let Some(p) = cursor_position.position_in(layout.bounds()) {
                    editor.action(Action::Click {
                        x: ((p.x - self.padding.left) * scale_factor) as i32,
                        y: ((p.y - self.padding.top) * scale_factor) as i32,
                    });
                    state.is_dragging = true;
                    status = Status::Captured;
                }
            }
            Event::Mouse(MouseEvent::ButtonReleased(Button::Left)) => {
                state.is_dragging = false;
                status = Status::Captured;
            }
            Event::Mouse(MouseEvent::CursorMoved { .. }) => {
                if state.is_dragging {
                    if let Some(p) = cursor_position.position() {
                        editor.action(Action::Drag {
                            x: (((p.x - layout.bounds().x) - self.padding.left) * scale_factor)
                                as i32,
                            y: (((p.y - layout.bounds().y) - self.padding.top) * scale_factor)
                                as i32,
                        });
                    }
                    status = Status::Captured;
                }
            }
            Event::Mouse(MouseEvent::WheelScrolled { delta }) => match delta {
                ScrollDelta::Lines { x, y } => {
                    editor.action(Action::Scroll {
                        lines: (-y * 6.0) as i32,
                    });
                    status = Status::Captured;
                }
                _ => (),
            },
            _ => (),
        }

        status
    }
}

impl<'a, 'editor, Editor, Message, Renderer> From<TextBox<'a, Editor>>
    for Element<'a, Message, Renderer>
where
    Renderer: renderer::Renderer + image::Renderer<Handle = image::Handle>,
    Renderer::Theme: StyleSheet,
    Editor: Edit,
{
    fn from(text_box: TextBox<'a, Editor>) -> Self {
        Self::new(text_box)
    }
}

pub struct State {
    modifiers: Modifiers,
    is_dragging: bool,
    scale_factor: Cell<f64>,
    handle: Mutex<image::Handle>,
}

impl State {
    /// Creates a new [`State`].
    pub fn new() -> State {
        State {
            modifiers: Modifiers::empty(),
            is_dragging: false,
            scale_factor: Cell::new(1.0),
            //TODO: make option!
            handle: Mutex::new(image::Handle::from_pixels(1, 1, vec![0, 0, 0, 0])),
        }
    }
}