//! Show toggle controls using checkboxes.
use crate::core::alignment;
use crate::core::event::{self, Event};
use crate::core::layout;
use crate::core::mouse;
use crate::core::renderer;
use crate::core::text;
use crate::core::touch;
use crate::core::widget;
use crate::core::widget::tree::{self, Tree};
use crate::core::{
    Background, Border, Clipboard, Color, Element, Layout, Length, Pixels,
    Rectangle, Shell, Size, Widget,
};
use crate::style::theme::palette;
use crate::style::Theme;

/// A box that can be checked.
///
/// # Example
///
/// ```no_run
/// # type Checkbox<'a, Message> =
/// #     iced_widget::Checkbox<'a, Message, iced_widget::style::Theme, iced_widget::renderer::Renderer>;
/// #
/// pub enum Message {
///     CheckboxToggled(bool),
/// }
///
/// let is_checked = true;
///
/// Checkbox::new("Toggle me!", is_checked).on_toggle(Message::CheckboxToggled);
/// ```
///
/// ![Checkbox drawn by `iced_wgpu`](https://github.com/iced-rs/iced/blob/7760618fb112074bc40b148944521f312152012a/docs/images/checkbox.png?raw=true)
#[allow(missing_debug_implementations)]
pub struct Checkbox<
    'a,
    Message,
    Theme = crate::Theme,
    Renderer = crate::Renderer,
> where
    Renderer: text::Renderer,
{
    is_checked: bool,
    on_toggle: Option<Box<dyn Fn(bool) -> Message + 'a>>,
    label: String,
    width: Length,
    size: f32,
    spacing: f32,
    text_size: Option<Pixels>,
    text_line_height: text::LineHeight,
    text_shaping: text::Shaping,
    font: Option<Renderer::Font>,
    icon: Icon<Renderer::Font>,
    style: fn(&Theme, Status) -> Appearance,
}

impl<'a, Message, Theme, Renderer> Checkbox<'a, Message, Theme, Renderer>
where
    Renderer: text::Renderer,
    Theme: Style,
{
    /// The default size of a [`Checkbox`].
    const DEFAULT_SIZE: f32 = 15.0;

    /// The default spacing of a [`Checkbox`].
    const DEFAULT_SPACING: f32 = 10.0;

    /// Creates a new [`Checkbox`].
    ///
    /// It expects:
    ///   * the label of the [`Checkbox`]
    ///   * a boolean describing whether the [`Checkbox`] is checked or not
    pub fn new(label: impl Into<String>, is_checked: bool) -> Self {
        Checkbox {
            is_checked,
            on_toggle: None,
            label: label.into(),
            width: Length::Shrink,
            size: Self::DEFAULT_SIZE,
            spacing: Self::DEFAULT_SPACING,
            text_size: None,
            text_line_height: text::LineHeight::default(),
            text_shaping: text::Shaping::Basic,
            font: None,
            icon: Icon {
                font: Renderer::ICON_FONT,
                code_point: Renderer::CHECKMARK_ICON,
                size: None,
                line_height: text::LineHeight::default(),
                shaping: text::Shaping::Basic,
            },
            style: Theme::style(),
        }
    }

    /// Sets the function that will be called when the [`Checkbox`] is toggled.
    /// It will receive the new state of the [`Checkbox`] and must produce a
    /// `Message`.
    ///
    /// Unless `on_toggle` is called, the [`Checkbox`] will be disabled.
    pub fn on_toggle<F>(mut self, f: F) -> Self
    where
        F: 'a + Fn(bool) -> Message,
    {
        self.on_toggle = Some(Box::new(f));
        self
    }

    /// Sets the function that will be called when the [`Checkbox`] is toggled,
    /// if `Some`.
    ///
    /// If `None`, the checkbox will be disabled.
    pub fn on_toggle_maybe<F>(mut self, f: Option<F>) -> Self
    where
        F: Fn(bool) -> Message + 'a,
    {
        self.on_toggle = f.map(|f| Box::new(f) as _);
        self
    }

    /// Sets the size of the [`Checkbox`].
    pub fn size(mut self, size: impl Into<Pixels>) -> Self {
        self.size = size.into().0;
        self
    }

    /// Sets the width of the [`Checkbox`].
    pub fn width(mut self, width: impl Into<Length>) -> Self {
        self.width = width.into();
        self
    }

    /// Sets the spacing between the [`Checkbox`] and the text.
    pub fn spacing(mut self, spacing: impl Into<Pixels>) -> Self {
        self.spacing = spacing.into().0;
        self
    }

    /// Sets the text size of the [`Checkbox`].
    pub fn text_size(mut self, text_size: impl Into<Pixels>) -> Self {
        self.text_size = Some(text_size.into());
        self
    }

    /// Sets the text [`text::LineHeight`] of the [`Checkbox`].
    pub fn text_line_height(
        mut self,
        line_height: impl Into<text::LineHeight>,
    ) -> Self {
        self.text_line_height = line_height.into();
        self
    }

    /// Sets the [`text::Shaping`] strategy of the [`Checkbox`].
    pub fn text_shaping(mut self, shaping: text::Shaping) -> Self {
        self.text_shaping = shaping;
        self
    }

    /// Sets the [`Renderer::Font`] of the text of the [`Checkbox`].
    ///
    /// [`Renderer::Font`]: crate::core::text::Renderer
    pub fn font(mut self, font: impl Into<Renderer::Font>) -> Self {
        self.font = Some(font.into());
        self
    }

    /// Sets the [`Icon`] of the [`Checkbox`].
    pub fn icon(mut self, icon: Icon<Renderer::Font>) -> Self {
        self.icon = icon;
        self
    }

    /// Sets the style of the [`Checkbox`].
    pub fn style(mut self, style: fn(&Theme, Status) -> Appearance) -> Self {
        self.style = style.into();
        self
    }
}

impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
    for Checkbox<'a, Message, Theme, Renderer>
where
    Renderer: text::Renderer,
{
    fn tag(&self) -> tree::Tag {
        tree::Tag::of::<widget::text::State<Renderer::Paragraph>>()
    }

    fn state(&self) -> tree::State {
        tree::State::new(widget::text::State::<Renderer::Paragraph>::default())
    }

    fn size(&self) -> Size<Length> {
        Size {
            width: self.width,
            height: Length::Shrink,
        }
    }

    fn layout(
        &self,
        tree: &mut Tree,
        renderer: &Renderer,
        limits: &layout::Limits,
    ) -> layout::Node {
        layout::next_to_each_other(
            &limits.width(self.width),
            self.spacing,
            |_| layout::Node::new(Size::new(self.size, self.size)),
            |limits| {
                let state = tree
                    .state
                    .downcast_mut::<widget::text::State<Renderer::Paragraph>>();

                widget::text::layout(
                    state,
                    renderer,
                    limits,
                    self.width,
                    Length::Shrink,
                    &self.label,
                    self.text_line_height,
                    self.text_size,
                    self.font,
                    alignment::Horizontal::Left,
                    alignment::Vertical::Top,
                    self.text_shaping,
                )
            },
        )
    }

    fn on_event(
        &mut self,
        _tree: &mut Tree,
        event: Event,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        _renderer: &Renderer,
        _clipboard: &mut dyn Clipboard,
        shell: &mut Shell<'_, Message>,
        _viewport: &Rectangle,
    ) -> event::Status {
        match event {
            Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left))
            | Event::Touch(touch::Event::FingerPressed { .. }) => {
                let mouse_over = cursor.is_over(layout.bounds());

                if mouse_over {
                    if let Some(on_toggle) = &self.on_toggle {
                        shell.publish((on_toggle)(!self.is_checked));
                        return event::Status::Captured;
                    }
                }
            }
            _ => {}
        }

        event::Status::Ignored
    }

    fn mouse_interaction(
        &self,
        _tree: &Tree,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        _viewport: &Rectangle,
        _renderer: &Renderer,
    ) -> mouse::Interaction {
        if cursor.is_over(layout.bounds()) && self.on_toggle.is_some() {
            mouse::Interaction::Pointer
        } else {
            mouse::Interaction::default()
        }
    }

    fn draw(
        &self,
        tree: &Tree,
        renderer: &mut Renderer,
        theme: &Theme,
        style: &renderer::Style,
        layout: Layout<'_>,
        cursor: mouse::Cursor,
        viewport: &Rectangle,
    ) {
        let is_mouse_over = cursor.is_over(layout.bounds());
        let is_disabled = self.on_toggle.is_none();
        let is_checked = self.is_checked;

        let mut children = layout.children();

        let status = if is_disabled {
            Status::Disabled { is_checked }
        } else if is_mouse_over {
            Status::Hovered { is_checked }
        } else {
            Status::Active { is_checked }
        };

        let appearance = (self.style)(theme, status);

        {
            let layout = children.next().unwrap();
            let bounds = layout.bounds();

            renderer.fill_quad(
                renderer::Quad {
                    bounds,
                    border: appearance.border,
                    ..renderer::Quad::default()
                },
                appearance.background,
            );

            let Icon {
                font,
                code_point,
                size,
                line_height,
                shaping,
            } = &self.icon;
            let size = size.unwrap_or(Pixels(bounds.height * 0.7));

            if self.is_checked {
                renderer.fill_text(
                    text::Text {
                        content: &code_point.to_string(),
                        font: *font,
                        size,
                        line_height: *line_height,
                        bounds: bounds.size(),
                        horizontal_alignment: alignment::Horizontal::Center,
                        vertical_alignment: alignment::Vertical::Center,
                        shaping: *shaping,
                    },
                    bounds.center(),
                    appearance.icon_color,
                    *viewport,
                );
            }
        }

        {
            let label_layout = children.next().unwrap();

            crate::text::draw(
                renderer,
                style,
                label_layout,
                tree.state.downcast_ref(),
                crate::text::Appearance {
                    color: appearance.text_color,
                },
                viewport,
            );
        }
    }
}

impl<'a, Message, Theme, Renderer> From<Checkbox<'a, Message, Theme, Renderer>>
    for Element<'a, Message, Theme, Renderer>
where
    Message: 'a,
    Theme: 'a,
    Renderer: 'a + text::Renderer,
{
    fn from(
        checkbox: Checkbox<'a, Message, Theme, Renderer>,
    ) -> Element<'a, Message, Theme, Renderer> {
        Element::new(checkbox)
    }
}

/// The icon in a [`Checkbox`].
#[derive(Debug, Clone, PartialEq)]
pub struct Icon<Font> {
    /// Font that will be used to display the `code_point`,
    pub font: Font,
    /// The unicode code point that will be used as the icon.
    pub code_point: char,
    /// Font size of the content.
    pub size: Option<Pixels>,
    /// The line height of the icon.
    pub line_height: text::LineHeight,
    /// The shaping strategy of the icon.
    pub shaping: text::Shaping,
}

/// The possible status of a [`Checkbox`].
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Status {
    /// The [`Checkbox`] can be interacted with.
    Active {
        /// Indicates if the [`Checkbox`] is currently checked.
        is_checked: bool,
    },
    /// The [`Checkbox`] can be interacted with and it is being hovered.
    Hovered {
        /// Indicates if the [`Checkbox`] is currently checked.
        is_checked: bool,
    },
    /// The [`Checkbox`] cannot be interacted with.
    Disabled {
        /// Indicates if the [`Checkbox`] is currently checked.
        is_checked: bool,
    },
}

/// The appearance of a checkbox.
#[derive(Debug, Clone, Copy)]
pub struct Appearance {
    /// The [`Background`] of the checkbox.
    pub background: Background,
    /// The icon [`Color`] of the checkbox.
    pub icon_color: Color,
    /// The [`Border`] of hte checkbox.
    pub border: Border,
    /// The text [`Color`] of the checkbox.
    pub text_color: Option<Color>,
}

/// A set of rules that dictate the style of a checkbox.
pub trait Style {
    /// The supported style of the [`StyleSheet`].
    fn style() -> fn(&Self, Status) -> Appearance;
}

impl Style for Theme {
    fn style() -> fn(&Self, Status) -> Appearance {
        primary
    }
}

/// A primary checkbox; denoting a main toggle.
pub fn primary(theme: &Theme, status: Status) -> Appearance {
    let palette = theme.extended_palette();

    match status {
        Status::Active { is_checked } => styled(
            palette.primary.strong.text,
            palette.background.base,
            palette.primary.strong,
            is_checked,
        ),
        Status::Hovered { is_checked } => styled(
            palette.primary.strong.text,
            palette.background.weak,
            palette.primary.base,
            is_checked,
        ),
        Status::Disabled { is_checked } => styled(
            palette.primary.strong.text,
            palette.background.weak,
            palette.background.strong,
            is_checked,
        ),
    }
}

/// A secondary checkbox; denoting a complementary toggle.
pub fn secondary(theme: &Theme, status: Status) -> Appearance {
    let palette = theme.extended_palette();

    match status {
        Status::Active { is_checked } => styled(
            palette.background.base.text,
            palette.background.base,
            palette.background.strong,
            is_checked,
        ),
        Status::Hovered { is_checked } => styled(
            palette.background.base.text,
            palette.background.weak,
            palette.background.strong,
            is_checked,
        ),
        Status::Disabled { is_checked } => styled(
            palette.background.strong.color,
            palette.background.weak,
            palette.background.weak,
            is_checked,
        ),
    }
}

/// A success checkbox; denoting a positive toggle.
pub fn success(theme: &Theme, status: Status) -> Appearance {
    let palette = theme.extended_palette();

    match status {
        Status::Active { is_checked } => styled(
            palette.success.base.text,
            palette.background.base,
            palette.success.base,
            is_checked,
        ),
        Status::Hovered { is_checked } => styled(
            palette.success.base.text,
            palette.background.weak,
            palette.success.base,
            is_checked,
        ),
        Status::Disabled { is_checked } => styled(
            palette.success.base.text,
            palette.background.weak,
            palette.success.weak,
            is_checked,
        ),
    }
}

/// A danger checkbox; denoting a negaive toggle.
pub fn danger(theme: &Theme, status: Status) -> Appearance {
    let palette = theme.extended_palette();

    match status {
        Status::Active { is_checked } => styled(
            palette.danger.base.text,
            palette.background.base,
            palette.danger.base,
            is_checked,
        ),
        Status::Hovered { is_checked } => styled(
            palette.danger.base.text,
            palette.background.weak,
            palette.danger.base,
            is_checked,
        ),
        Status::Disabled { is_checked } => styled(
            palette.danger.base.text,
            palette.background.weak,
            palette.danger.weak,
            is_checked,
        ),
    }
}

fn styled(
    icon_color: Color,
    base: palette::Pair,
    accent: palette::Pair,
    is_checked: bool,
) -> Appearance {
    Appearance {
        background: Background::Color(if is_checked {
            accent.color
        } else {
            base.color
        }),
        icon_color,
        border: Border {
            radius: 2.0.into(),
            width: 1.0,
            color: accent.color,
        },
        text_color: None,
    }
}
