use std::{borrow::Cow, path::PathBuf};

use crate::{
    compositor::{Callback, Component, Compositor, Context, EventResult},
    ctrl, key, shift,
};
use crossterm::event::Event;
use tui::{buffer::Buffer as Surface, text::Spans, widgets::Table};

pub use tui::widgets::{Cell, Row};

use fuzzy_matcher::skim::SkimMatcherV2 as Matcher;
use fuzzy_matcher::FuzzyMatcher;

use helix_view::{graphics::Rect, Editor};
use tui::layout::Constraint;

pub trait Item {
    /// Additional editor state that is used for label calculation.
    type Data;

    fn label(&self, data: &Self::Data) -> Spans;

    fn sort_text(&self, data: &Self::Data) -> Cow<str> {
        let label: String = self.label(data).into();
        label.into()
    }

    fn filter_text(&self, data: &Self::Data) -> Cow<str> {
        let label: String = self.label(data).into();
        label.into()
    }

    fn row(&self, data: &Self::Data) -> Row {
        Row::new(vec![Cell::from(self.label(data))])
    }
}

impl Item for PathBuf {
    /// Root prefix to strip.
    type Data = PathBuf;

    fn label(&self, root_path: &Self::Data) -> Spans {
        self.strip_prefix(&root_path)
            .unwrap_or(self)
            .to_string_lossy()
            .into()
    }
}

pub struct Menu<T: Item> {
    options: Vec<T>,
    editor_data: T::Data,

    cursor: Option<usize>,

    matcher: Box<Matcher>,
    /// (index, score)
    matches: Vec<(usize, i64)>,

    widths: Vec<Constraint>,

    callback_fn: Box<dyn Fn(&mut Editor, Option<&T>, MenuEvent)>,

    scroll: usize,
    size: (u16, u16),
    viewport: (u16, u16),
    recalculate: bool,
}

impl<T: Item> Menu<T> {
    const LEFT_PADDING: usize = 1;

    // TODO: it's like a slimmed down picker, share code? (picker = menu + prompt with different
    // rendering)
    pub fn new(
        options: Vec<T>,
        editor_data: <T as Item>::Data,
        callback_fn: impl Fn(&mut Editor, Option<&T>, MenuEvent) + 'static,
    ) -> Self {
        let mut menu = Self {
            options,
            editor_data,
            matcher: Box::new(Matcher::default()),
            matches: Vec::new(),
            cursor: None,
            widths: Vec::new(),
            callback_fn: Box::new(callback_fn),
            scroll: 0,
            size: (0, 0),
            viewport: (0, 0),
            recalculate: true,
        };

        // TODO: scoring on empty input should just use a fastpath
        menu.score("");

        menu
    }

    pub fn score(&mut self, pattern: &str) {
        // reuse the matches allocation
        self.matches.clear();
        self.matches.extend(
            self.options
                .iter()
                .enumerate()
                .filter_map(|(index, option)| {
                    let text: String = option.filter_text(&self.editor_data).into();
                    // TODO: using fuzzy_indices could give us the char idx for match highlighting
                    self.matcher
                        .fuzzy_match(&text, pattern)
                        .map(|score| (index, score))
                }),
        );
        // matches.sort_unstable_by_key(|(_, score)| -score);
        self.matches.sort_unstable_by_key(|(index, _score)| {
            self.options[*index].sort_text(&self.editor_data)
        });

        // reset cursor position
        self.cursor = None;
        self.scroll = 0;
        self.recalculate = true;
    }

    pub fn clear(&mut self) {
        self.matches.clear();

        // reset cursor position
        self.cursor = None;
        self.scroll = 0;
    }

    pub fn move_up(&mut self) {
        let len = self.matches.len();
        let max_index = len.saturating_sub(1);
        let pos = self.cursor.map_or(max_index, |i| (i + max_index) % len) % len;
        self.cursor = Some(pos);
        self.adjust_scroll();
    }

    pub fn move_down(&mut self) {
        let len = self.matches.len();
        let pos = self.cursor.map_or(0, |i| i + 1) % len;
        self.cursor = Some(pos);
        self.adjust_scroll();
    }

    fn recalculate_size(&mut self, viewport: (u16, u16)) {
        let n = self
            .options
            .first()
            .map(|option| option.row(&self.editor_data).cells.len())
            .unwrap_or_default();
        let max_lens = self.options.iter().fold(vec![0; n], |mut acc, option| {
            let row = option.row(&self.editor_data);
            // maintain max for each column
            for (acc, cell) in acc.iter_mut().zip(row.cells.iter()) {
                let width = cell.content.width();
                if width > *acc {
                    *acc = width;
                }
            }

            acc
        });

        let height = self.matches.len().min(10).min(viewport.1 as usize);
        // do all the matches fit on a single screen?
        let fits = self.matches.len() <= height;

        let mut len = max_lens.iter().sum::<usize>() + n;

        if !fits {
            len += 1; // +1: reserve some space for scrollbar
        }

        len += Self::LEFT_PADDING;
        let width = len.min(viewport.0 as usize);

        self.widths = max_lens
            .into_iter()
            .map(|len| Constraint::Length(len as u16))
            .collect();

        self.size = (width as u16, height as u16);

        // adjust scroll offsets if size changed
        self.adjust_scroll();
        self.recalculate = false;
    }

    fn adjust_scroll(&mut self) {
        let win_height = self.size.1 as usize;
        if let Some(cursor) = self.cursor {
            let mut scroll = self.scroll;
            if cursor > (win_height + scroll).saturating_sub(1) {
                // scroll down
                scroll += cursor - (win_height + scroll).saturating_sub(1)
            } else if cursor < scroll {
                // scroll up
                scroll = cursor
            }
            self.scroll = scroll;
        }
    }

    pub fn selection(&self) -> Option<&T> {
        self.cursor.and_then(|cursor| {
            self.matches
                .get(cursor)
                .map(|(index, _score)| &self.options[*index])
        })
    }

    pub fn is_empty(&self) -> bool {
        self.matches.is_empty()
    }

    pub fn len(&self) -> usize {
        self.matches.len()
    }
}

use super::PromptEvent as MenuEvent;

impl<T: Item + 'static> Component for Menu<T> {
    fn handle_event(&mut self, event: Event, cx: &mut Context) -> EventResult {
        let event = match event {
            Event::Key(event) => event,
            _ => return EventResult::Ignored(None),
        };

        let close_fn: Option<Callback> = Some(Box::new(|compositor: &mut Compositor, _| {
            // remove the layer
            compositor.pop();
        }));

        match event.into() {
            // esc or ctrl-c aborts the completion and closes the menu
            key!(Esc) | ctrl!('c') => {
                (self.callback_fn)(cx.editor, self.selection(), MenuEvent::Abort);
                return EventResult::Consumed(close_fn);
            }
            // arrow up/ctrl-p/shift-tab prev completion choice (including updating the doc)
            shift!(Tab) | key!(Up) | ctrl!('p') | ctrl!('k') => {
                self.move_up();
                (self.callback_fn)(cx.editor, self.selection(), MenuEvent::Update);
                return EventResult::Consumed(None);
            }
            key!(Tab) | key!(Down) | ctrl!('n') | ctrl!('j') => {
                // arrow down/ctrl-n/tab advances completion choice (including updating the doc)
                self.move_down();
                (self.callback_fn)(cx.editor, self.selection(), MenuEvent::Update);
                return EventResult::Consumed(None);
            }
            key!(Enter) => {
                if let Some(selection) = self.selection() {
                    (self.callback_fn)(cx.editor, Some(selection), MenuEvent::Validate);
                    return EventResult::Consumed(close_fn);
                } else {
                    return EventResult::Ignored(close_fn);
                }
            }
            // KeyEvent {
            //     code: KeyCode::Char(c),
            //     modifiers: KeyModifiers::NONE,
            // } => {
            //     self.insert_char(c);
            //     (self.callback_fn)(cx.editor, &self.line, MenuEvent::Update);
            // }

            // / -> edit_filter?
            //
            // enter confirms the match and closes the menu
            // typing filters the menu
            // if we run out of options the menu closes itself
            _ => (),
        }
        // for some events, we want to process them but send ignore, specifically all input except
        // tab/enter/ctrl-k or whatever will confirm the selection/ ctrl-n/ctrl-p for scroll.
        // EventResult::Consumed(None)
        EventResult::Ignored(None)
    }

    fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
        if viewport != self.viewport || self.recalculate {
            self.recalculate_size(viewport);
        }

        Some(self.size)
    }

    fn render(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        let theme = &cx.editor.theme;
        let style = theme
            .try_get("ui.menu")
            .unwrap_or_else(|| theme.get("ui.text"));
        let selected = theme.get("ui.menu.selected");
        surface.clear_with(area, style);

        let scroll = self.scroll;

        let options: Vec<_> = self
            .matches
            .iter()
            .map(|(index, _score)| {
                // (index, self.options.get(*index).unwrap()) // get_unchecked
                &self.options[*index] // get_unchecked
            })
            .collect();

        let len = options.len();

        let win_height = area.height as usize;

        const fn div_ceil(a: usize, b: usize) -> usize {
            (a + b - 1) / b
        }

        let scroll_height = std::cmp::min(div_ceil(win_height.pow(2), len), win_height as usize);

        let scroll_line = (win_height - scroll_height) * scroll
            / std::cmp::max(1, len.saturating_sub(win_height));

        let rows = options.iter().map(|option| option.row(&self.editor_data));
        let table = Table::new(rows)
            .style(style)
            .highlight_style(selected)
            .column_spacing(1)
            .widths(&self.widths);

        use tui::widgets::TableState;

        table.render_table(
            area.clip_left(Self::LEFT_PADDING as u16).clip_right(1),
            surface,
            &mut TableState {
                offset: scroll,
                selected: self.cursor,
            },
        );

        if let Some(cursor) = self.cursor {
            let offset_from_top = cursor - scroll;
            let left = &mut surface[(area.left(), area.y + offset_from_top as u16)];
            left.set_style(selected);
            let right = &mut surface[(
                area.right().saturating_sub(1),
                area.y + offset_from_top as u16,
            )];
            right.set_style(selected);
        }

        let fits = len <= win_height;

        let scroll_style = theme.get("ui.menu.scroll");
        for (i, _) in (scroll..(scroll + win_height).min(len)).enumerate() {
            let cell = &mut surface[(area.x + area.width - 1, area.y + i as u16)];

            if !fits {
                // Draw scroll track
                cell.set_symbol("▐"); // right half block
                cell.set_fg(scroll_style.bg.unwrap_or(helix_view::theme::Color::Reset));
            }

            let is_marked = i >= scroll_line && i < scroll_line + scroll_height;

            if !fits && is_marked {
                // Draw scroll thumb
                cell.set_fg(scroll_style.fg.unwrap_or(helix_view::theme::Color::Reset));
            }
        }
    }
}