use std::{
    rc::Rc,
    fmt::Display,
    cmp::Ordering,
    cell::Cell
};
use cursive_core::{
    Cursive, impl_enabled, Printer,
    Rect, Vec2, View, With,
    direction::{Direction, Absolute},
    view::{CannotFocus, Position},
    event::{Event, EventResult, Key, MouseButton, MouseEvent},
    utils::markup::StyledString,
    views::{
        Dialog,
        LayerPosition,
        OnEventView,
    }
};
use crate::{
    c_focus, vlayout,
    AdvancedButton
};
use super::ButtonContent;

type SelectCallback<T> = Rc<dyn Fn(&mut Cursive, &T)>;

/// A view that is a lot like a `SelectView` but allows mutable access to the selection
/// and allows multiline items
//TODO: multiple selections
#[derive(Clone)]
pub struct AdvancedSelectView<T = String>
    where T: 'static
{
    // the items
    items: Vec<StyledItem<T>>,

    // is this view enabled?
    enabled: bool,

    // the selected item id
    selected: Rc<Cell<usize>>,

    // autojump by keyboard key?
    autojump: bool,

    // show as a popup?
    popup: bool,

    // the offset for the popup view
    popup_ofs: Cell<Vec2>,

    // callback for selecting an item
    selected_cb: SelectCallback<T>,

    // callback for pressing Enter
    submit_cb: SelectCallback<T>,

    // the view's current size if it has already been calculated
    size_cache: Option<Vec2>
}

impl AdvancedSelectView {
    /// Add an item with the label as the value
    pub fn add_item_str<S: Display>(&mut self, label: S) {
        self.add_item(label.to_string(), label.to_string());
    }

    /// Add an item with the label as the value
    ///
    /// Chainable version
    #[must_use]
    pub fn item_str<S: Display>(mut self, label: S) -> Self {
        self.add_item_str(label);
        self
    }

    /// Insert an item with the label as the value
    pub fn insert_item_str<S: Display>(&mut self, index: usize, label: S) {
        self.insert_item(index, label.to_string(), label.to_string());
    }

    /// Add all the strings from a string iterator
    pub fn add_all_str<S, I>(&mut self, iter: I)
        where
            S: Display,
            I: IntoIterator<Item = S>
    {
        for label in iter {
            self.add_item_str(label);
        }
    }

    /// Add all the strings from a string iterator
    ///
    /// Chainable version
    #[must_use]
    pub fn with_all_str<S, I>(mut self, iter: I) -> Self
        where
            S: Display,
            I: IntoIterator<Item = S>
    {
        self.add_all_str(iter);
        self
    }
}

impl<T: Ord + 'static> AdvancedSelectView<T> {
    /// Sort all the items by their ordering
    pub fn sort(&mut self) { self.items.sort_by(|a, b| a.item.cmp(&b.item)); }
}

impl<T: 'static> AdvancedSelectView<T> {
    impl_enabled!(self.enabled);

    /// Create a new `AdvancedSelectView`
    #[must_use]
    pub fn new() -> AdvancedSelectView<T> {
        AdvancedSelectView {
            items: vec![],
            enabled: true,
            selected: Rc::new(Cell::new(0)),
            autojump: false,
            popup: false,
            popup_ofs: Cell::new((0, 0).into()),
            selected_cb: Rc::new(|_, _| { }),
            submit_cb: Rc::new(|_, _| { }),
            size_cache: None
        }
    }

    /// Allow jumping to items starting with the the pressed letter key
    pub fn set_autojump(&mut self, autojump: bool) { self.autojump = autojump; }

    /// Allow jumping to items starting with the the pressed letter key
    ///
    /// Chainable version
    #[must_use]
    pub fn autojump(mut self) -> Self {
        self.set_autojump(true);
        self
    }

    /// Show this view as a pop up view
    pub fn set_popup(&mut self, popup: bool) {
        self.popup = popup;
        self.size_cache = None;
    }

    /// Show this view as a pop up view
    ///
    /// Chainable version
    #[must_use]
    pub fn popup(mut self) -> Self {
        self.set_popup(true);
        self
    }

    /// Set the select callback
    pub fn set_on_select<F: Fn(&mut Cursive, &T) + 'static>(&mut self, cb: F) { self.selected_cb = Rc::new(cb); }

    /// Set the select callback
    ///
    /// Chainable version
    #[must_use]
    pub fn on_select<F: Fn(&mut Cursive, &T) + 'static>(mut self, cb: F) -> Self {
        self.set_on_select(cb);
        self
    }

    /// Set the callback when Enter is pressed
    pub fn set_on_submit<F: Fn(&mut Cursive, &T) + 'static>(&mut self, cb: F) { self.submit_cb = Rc::new(cb); }

    /// Set the callback when Enter is pressed
    ///
    /// Chainable version
    #[must_use]
    pub fn on_submit<F: Fn(&mut Cursive, &T) + 'static>(mut self, cb: F) -> Self {
        self.set_on_submit(cb);
        self
    }

    /// The current selection
    ///
    /// Returns `None` if the view is empty
    pub fn selection(&self) -> Option<&T> {
        Some(&self.items.get(self.selected.get())?.item)
    }

    /// The current selection as a mutable reference
    ///
    /// Returns `None` if the view is empty
    pub fn selection_mut(&mut self) -> Option<&mut T> {
        Rc::get_mut(&mut self.items.get_mut(self.selected.get())?.item)
    }

    /// The index of the current selection
    pub fn selected_index(&self) -> usize { self.selected.get() }

    /// The label of the current selected item
    pub fn selected_label(&self) -> Option<&StyledString> {
        Some(self.items.get(self.selected.get())?.label.get_content())
    }

    /// The label of the current selected item
    pub fn selected_label_mut(&mut self) -> Option<&mut StyledString> {
        Some(self.items.get_mut(self.selected.get())?.label.get_content_mut())
    }

    /// Set the selected item index
    pub fn set_selection(&mut self, index: usize) {
        if index < self.items.len() { self.selected.set(index); }
    }

    /// Set the selected item ID
    ///
    /// Chainable version
    #[must_use]
    pub fn selected(mut self, index: usize) -> Self {
        self.set_selection(index);
        self
    }

    /// Move the selection down
    ///
    /// Returns true if successful
    pub fn move_down(&mut self) -> bool {
        if self.selected.get() < self.items.len().saturating_sub(1) {
            let new_selected = self.selected.get() + 1;
            self.selected.set(new_selected);
            return true;
        }
        false
    }

    /// Move the selection up
    ///
    /// Returns true if successful
    pub fn move_up(&mut self) -> bool {
        if self.selected.get() != 0 {
            let new_selected = self.selected.get() - 1;
            self.selected.set(new_selected);
            return true;
        }
        false
    }

    /// Clear all items
    pub fn clear(&mut self) {
        self.size_cache = None;
        self.items.clear();
        self.selected.set(0)
    }

    /// How many items are in this view?
    pub fn len(&self) -> usize { self.items.len() }

    /// Is this view empty?
    pub fn is_empty(&self) -> bool { self.items.is_empty() }

    /// Add an item to this view
    pub fn add_item<L: Into<StyledString>>(&mut self, label: L, item: T) {
        let mut new_item = StyledItem::new(label, item);
        if let Some(size) = self.size_cache {
            new_item.fit_to_width(size.x, false);
        }
        self.items.push(new_item)
    }

    /// Add all items from an iterator
    pub fn add_all<L, I>(&mut self, iter: I)
        where
            L: Into<StyledString>,
            I: IntoIterator<Item = (L, T)>
    {
        for (label, item) in iter {
            self.add_item(label, item);
        }
    }

    /// Add all items from an iterator
    ///
    /// Chainable version
    #[must_use]
    pub fn with_all<L, I>(mut self, iter: I) -> Self
        where
            L: Into<StyledString>,
            I: IntoIterator<Item = (L, T)>
    {
        self.add_all(iter);
        self
    }

    /// Add an item to this view
    ///
    /// Chainable version
    #[must_use]
    pub fn item<L: Into<StyledString>>(mut self, label: L, item: T) -> Self {
        self.add_item(label, item);
        self
    }

    /// Get an item at the index
    pub fn get_item(&self, index: usize) -> Option<(&StyledString, &T)> {
        let item = self.items.get(index)?;
        Some((item.label.get_content(), &item.item))
    }

    /// Get an item (mutable reference) at the index
    pub fn get_item_mut(&mut self, index: usize) -> Option<(&mut StyledString, &mut T)> {
        let item = self.items.get_mut(index)?;
        if let Some(t) = Rc::get_mut(&mut item.item) {
            let label = &mut item.label;
            Some((label.get_content_mut(), t))
        }
        else { None }
    }

    /// Iterate over all the items
    pub fn iter(&self) -> impl Iterator<Item = (&StyledString, &T)> + DoubleEndedIterator + ExactSizeIterator {
        self.items.iter().map(|item| (item.label.get_content(), &*item.item))
    }

    /// Iterate over all the items with mutability
    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&mut StyledString, &mut T)> + DoubleEndedIterator + ExactSizeIterator
        where T: Clone
    {
        self.items.iter_mut().map(|item| (item.label.get_content_mut(), Rc::make_mut(&mut item.item)))
    }

    /// Remove an item at a specific index
    pub fn remove_item(&mut self, index: usize) {
        if index < self.items.len() {
            self.items.remove(index);
            if index >= self.len() {
                self.selected.set(self.len() - 1);
            }
            let new_size = self.calc_size();
            self.size_cache = Some(new_size);
        }
    }

    /// Insert an item at a specific index
    pub fn insert_item<L: Into<StyledString>>(&mut self, index: usize, label: L, item: T) {
        if index < self.items.len() {
            let mut new_item = StyledItem::new(label, item);
            if let Some(size) = self.size_cache {
                new_item.fit_to_width(size.x, false);
            }
            self.items.insert(index, new_item);
        }
    }

    /// Sort the view by label
    pub fn label_sort(&mut self) {
        self.items
            .sort_by(|a, b| a.label.get_content().source().cmp(b.label.get_content().source()));

        self.calc_y_ofs();
    }

    /// Sort the view with the specified comparator function
    pub fn sort_by<F>(&mut self, mut compare: F)
        where
            F: FnMut(&T, &T) -> Ordering,
    {
        self.items.sort_by(|a, b| compare(&a.item, &b.item));
        self.calc_y_ofs();
    }

    /// Sort the view with a key extraction function
    pub fn sort_by_key<K, F>(&mut self, mut key_of: F)
        where
            F: FnMut(&T) -> K,
            K: Ord
    {
        self.items.sort_by_key(|item| key_of(&item.item));
        self.calc_y_ofs();
    }

    /// Move an item up in the view
    pub fn move_item_up(&mut self, index: usize) {
        if index > 0 {
            self.items.swap(index, index - 1);
            self.calc_y_ofs();
        }
    }

    /// Move an item down in the view
    pub fn move_item_down(&mut self, index: usize) {
        if index < self.items.len() - 1 {
            self.items.swap(index, index + 1);
            self.calc_y_ofs();
        }
    }

    fn open_popup(&mut self) -> EventResult {
        let mut sv_layout = vlayout!();

        for (i, item) in self.items.iter().enumerate() {
            let selected = self.selected.clone();
            let submit_cb = self.submit_cb.clone();
            let selected_cb = self.selected_cb.clone();
            let data = item.item.clone();
            sv_layout.add_child(
                AdvancedButton::new_with_data(
                    item.label.get_content().clone(),
                    item.item.clone(),
                    move |root| {
                        selected.set(i);
                        root.pop_layer();
                        submit_cb(root, &data);
                        selected_cb(root, &data);
                    }
                )
            );
            if i == self.selected.get() { sv_layout.set_focus_index(i).unwrap(); }
        }

        let y_ofs = self.items[self.selected.get()].y_ofs;
        let ofs = self.popup_ofs.get();
        let ofs = ofs.saturating_sub((0, y_ofs + 1)) + (1, 0);

        EventResult::with_cb_once(move |root| {
            let current_offset = root
                .screen()
                .layer_offset(LayerPosition::FromFront(0))
                .unwrap_or_else(Vec2::zero);

            let offset = ofs.signed() - current_offset;
            root.screen_mut().add_layer_at(
                Position::parent(offset),
                c_focus!(
                    Dialog::around(sv_layout)
                        .wrap_with(OnEventView::new)
                        .on_event(Event::Key(Key::Esc), |r| { r.pop_layer(); })
                )
            );
        })
    }

    // the height of this view
    fn view_height(&self) -> usize { self.items.iter().map(|item| item.size.y).sum() }

    // recalculate the y offset of all the items
    fn calc_y_ofs(&mut self) {
        let mut y = 0;
        for item in &mut self.items {
            item.y_ofs = y;
            y += item.size.y;
        }
    }

    fn calc_size(&mut self) -> Vec2 {
        let width = self
            .items
            .iter()
            .map(|item| item.size.x)
            .max()
            .unwrap_or(1);

        (width, self.view_height()).into()
    }
}

impl<T: 'static> View for AdvancedSelectView<T> {
    fn draw(&self, printer: &Printer) {
        if printer.size.x == 0 || printer.size.y == 0 { return; }
        if self.popup && !self.items.is_empty() {
            self.popup_ofs.set(printer.offset);
            self.items[self.selected.get()].draw(printer, self.enabled, printer.focused, true);
        }
        else {
            for (i, item) in self.items.iter().enumerate() {
                item.draw(printer, self.enabled, i == self.selected.get() && printer.focused, false);
            }
        }
    }

    fn required_size(&mut self, bound: Vec2) -> Vec2 {
        if bound.x == 0 || bound.y == 0 { return (0, 0).into() }
        let new_size = if self.popup && !self.items.is_empty() {
            let item = &mut self.items[self.selected.get()];
            item.fit_to_width(bound.x, true);
            item.label.size(true)
        }
        else {
            if let Some(size) = self.size_cache {
                if let Some(item) = self.items.get(0) {
                    if item.size.x > 0 { return size; }
                }
            }
            for item in &mut self.items {
                item.fit_to_width(bound.x, false);
            }

            self.calc_size()
        };
        new_size
    }

    fn layout(&mut self, size: Vec2) {
        if size.x == 0 || size.y == 0 { return; }
        self.calc_y_ofs();
        for item in &mut self.items {
            item.fit_to_width(size.x, false);
        }

        if self.popup {
            let selected = &mut self.items[self.selected.get()];
            selected.fit_to_width(size.x, true);
        }
        self.size_cache = Some(size);
    }

    fn take_focus(&mut self, dir: Direction) -> Result<EventResult, CannotFocus> {
        if self.enabled && !self.items.is_empty() {
            if !self.popup {
                match dir {
                    Direction::Abs(Absolute::Up) => self.selected.set(0),
                    Direction::Abs(Absolute::Down) => self.selected.set(self.items.len().saturating_sub(1)),
                    _ => { }
                }
            }
            Ok(EventResult::consumed())
        }
        else { Err(CannotFocus) }
    }

    fn on_event(&mut self, event: Event) -> EventResult {
        if self.enabled {
            match event {
                Event::Key(Key::Up) if !self.popup => if !self.move_up() { return EventResult::Ignored; }
                Event::Key(Key::Down) if !self.popup => if !self.move_down() { return EventResult::Ignored; },
                Event::Key(Key::End) if !self.popup => self.selected.set(self.items.len() - 1),
                Event::Key(Key::Home) if !self.popup => self.selected.set(0),

                Event::Key(Key::PageUp) if !self.popup => {
                    if self.selected.get() < 10 { self.selected.set(0) }
                    else {
                        let new_selected = self.selected.get() - 10;
                        self.selected.set(new_selected);
                    }
                }

                Event::Key(Key::PageDown) if !self.popup => {
                    if self.items.len() < 10 { self.selected.set(self.items.len() - 1) }
                    else if self.selected.get() > self.items.len() - 10 { self.selected.set(self.items.len() - 1); }
                    else {
                        let new_selected = self.selected.get() + 10;
                        self.selected.set(new_selected);
                    }
                }

                Event::Key(Key::Enter) => {
                    if self.is_empty() { return EventResult::Ignored; }
                    if self.popup { return self.open_popup(); }
                    let callback = self.submit_cb.clone();
                    let item = self.items[self.selected.get()].item.clone();
                    return EventResult::with_cb_once(move |root| callback(root, &item))
                }

                Event::Mouse {
                    event: MouseEvent::Press(button),
                    position,
                    offset
                }
                if position.checked_sub(offset).is_some() && !self.popup => {
                    for (i, item) in self.items.iter().enumerate() {
                        if item.has_mouse_pos(position - offset) {
                            self.selected.set(i);
                        }
                    }

                    if button == MouseButton::Left {
                        let callback = self.submit_cb.clone();
                        let item = self.items[self.selected.get()].item.clone();
                        return EventResult::with_cb_once(move |root| callback(root, &item))
                    }
                }

                Event::Mouse {
                    event: MouseEvent::Release(MouseButton::Left),
                    position,
                    offset
                } if self.popup => {
                    let item = &self.items[self.selected.get()];
                    let b_rect = Rect::from_size((0, 0), item.size);

                    if let Some(new_pos) = position.checked_sub(offset) {
                        if b_rect.contains(new_pos) {
                            return self.open_popup();
                        }
                    }
                }

                Event::Char(c) if self.autojump && !self.popup => {
                    let lc = c.to_ascii_lowercase();
                    for (i, item) in self.items.iter().enumerate() {
                        let raw_label = item.label.get_content().source();
                        if raw_label.is_empty() || i <= self.selected.get() { continue; }
                        else {
                            let first_char = raw_label
                                .chars()
                                .next().unwrap()
                                .to_ascii_lowercase();
                            if lc == first_char {
                                self.selected.set(i);
                                break;
                            }
                        }
                    }
                }

                Event::WindowResize => {
                    self.size_cache = None;
                    for item in &mut self.items {
                        item.size = (0, 1).into();
                    }
                    return EventResult::Ignored;
                }

                _ => return EventResult::Ignored
            }

            if self.items.is_empty() { EventResult::Ignored }
            else {
                let callback = self.selected_cb.clone();
                let item = self.items[self.selected.get()].item.clone();
                EventResult::with_cb_once(move |root| callback(root, &item))
            }
        }
        else { EventResult::Ignored }
    }

    fn important_area(&self, size: Vec2) -> Rect {
        if self.popup { Rect::from_size((0, 0), size) }
        else {
            let loc = (0, self.items[self.selected.get()].y_ofs);
            Rect::from_size(loc, self.items[self.selected.get()].size)
        }
    }
}

impl<T: 'static> Default for AdvancedSelectView<T> {
    fn default() -> Self { Self::new() }
}

#[derive(Clone)]
struct StyledItem<T: 'static> {
    // this item's label
    label: ButtonContent,

    // the value
    item: Rc<T>,

    // size
    size: Vec2,

    // Y offset
    y_ofs: usize
}

impl<T: 'static> StyledItem<T> {
    fn new<L: Into<StyledString>>(label: L, item: T) -> StyledItem<T> {
        StyledItem {
            label: ButtonContent::new(label),
            item: Rc::new(item),
            size: (0, 1).into(),
            y_ofs: 0
        }
    }

    fn has_mouse_pos(&self, pos: Vec2) -> bool {
        Rect::from_size((0, self.y_ofs), self.size)
            .contains(pos)
    }

    fn draw(&self, printer: &Printer, enabled: bool, focused: bool, popup: bool) {
        self.label.draw(printer, if popup { (0, 0).into() } else { (0, self.y_ofs).into() }, enabled, focused, popup);
    }

    fn fit_to_width(&mut self, new_width: usize, popup: bool) {
        self.label.fit_to_width(new_width);
        self.size = self.label.size(popup);
    }
}