#![allow(missing_docs)]
use gpui::{relative, CursorStyle, DefiniteLength, MouseButton};
use gpui::{transparent_black, AnyElement, AnyView, ClickEvent, Hsla, Rems};
use smallvec::SmallVec;

use crate::{prelude::*, DynamicSpacing, ElevationIndex};

/// A trait for buttons that can be Selected. Enables setting the [`ButtonStyle`] of a button when it is selected.
pub trait SelectableButton: Selectable {
    fn selected_style(self, style: ButtonStyle) -> Self;
}

/// A common set of traits all buttons must implement.
pub trait ButtonCommon: Clickable + Disableable {
    /// A unique element ID to identify the button.
    fn id(&self) -> &ElementId;

    /// The visual style of the button.
    ///
    /// Most commonly will be [`ButtonStyle::Subtle`], or [`ButtonStyle::Filled`]
    /// for an emphasized button.
    fn style(self, style: ButtonStyle) -> Self;

    /// The size of the button.
    ///
    /// Most buttons will use the default size.
    ///
    /// [`ButtonSize`] can also be used to help build non-button elements
    /// that are consistently sized with buttons.
    fn size(self, size: ButtonSize) -> Self;

    /// The tooltip that shows when a user hovers over the button.
    ///
    /// Nearly all interactable elements should have a tooltip. Some example
    /// exceptions might a scroll bar, or a slider.
    fn tooltip(self, tooltip: impl Fn(&mut WindowContext) -> AnyView + 'static) -> Self;

    fn layer(self, elevation: ElevationIndex) -> Self;
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Default)]
pub enum IconPosition {
    #[default]
    Start,
    End,
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Default)]
pub enum TintColor {
    #[default]
    Accent,
    Negative,
    Warning,
    Positive,
}

impl TintColor {
    fn button_like_style(self, cx: &mut WindowContext) -> ButtonLikeStyles {
        match self {
            TintColor::Accent => ButtonLikeStyles {
                background: cx.theme().status().info_background,
                border_color: cx.theme().status().info_border,
                label_color: cx.theme().colors().text,
                icon_color: cx.theme().colors().text,
            },
            TintColor::Negative => ButtonLikeStyles {
                background: cx.theme().status().error_background,
                border_color: cx.theme().status().error_border,
                label_color: cx.theme().colors().text,
                icon_color: cx.theme().colors().text,
            },
            TintColor::Warning => ButtonLikeStyles {
                background: cx.theme().status().warning_background,
                border_color: cx.theme().status().warning_border,
                label_color: cx.theme().colors().text,
                icon_color: cx.theme().colors().text,
            },
            TintColor::Positive => ButtonLikeStyles {
                background: cx.theme().status().success_background,
                border_color: cx.theme().status().success_border,
                label_color: cx.theme().colors().text,
                icon_color: cx.theme().colors().text,
            },
        }
    }
}

impl From<TintColor> for Color {
    fn from(tint: TintColor) -> Self {
        match tint {
            TintColor::Accent => Color::Accent,
            TintColor::Negative => Color::Error,
            TintColor::Warning => Color::Warning,
            TintColor::Positive => Color::Success,
        }
    }
}

// Used to go from ButtonStyle -> Color through tint colors.
impl From<ButtonStyle> for Color {
    fn from(style: ButtonStyle) -> Self {
        match style {
            ButtonStyle::Tinted(tint) => tint.into(),
            _ => Color::Default,
        }
    }
}

/// The visual appearance of a button.
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Default)]
pub enum ButtonStyle {
    /// A filled button with a solid background color. Provides emphasis versus
    /// the more common subtle button.
    Filled,

    /// Used to emphasize a button in some way, like a selected state, or a semantic
    /// coloring like an error or success button.
    Tinted(TintColor),

    /// The default button style, used for most buttons. Has a transparent background,
    /// but has a background color to indicate states like hover and active.
    #[default]
    Subtle,

    /// Used for buttons that only change foreground color on hover and active states.
    ///
    /// TODO: Better docs for this.
    Transparent,
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
pub(crate) enum ButtonLikeRounding {
    All,
    Left,
    Right,
}

#[derive(Debug, Clone)]
pub(crate) struct ButtonLikeStyles {
    pub background: Hsla,
    #[allow(unused)]
    pub border_color: Hsla,
    #[allow(unused)]
    pub label_color: Hsla,
    #[allow(unused)]
    pub icon_color: Hsla,
}

fn element_bg_from_elevation(elevation: Option<ElevationIndex>, cx: &mut WindowContext) -> Hsla {
    match elevation {
        Some(ElevationIndex::Background) => cx.theme().colors().element_background,
        Some(ElevationIndex::ElevatedSurface) => cx.theme().colors().elevated_surface_background,
        Some(ElevationIndex::Surface) => cx.theme().colors().surface_background,
        Some(ElevationIndex::ModalSurface) => cx.theme().colors().background,
        _ => cx.theme().colors().element_background,
    }
}

impl ButtonStyle {
    pub(crate) fn enabled(
        self,
        elevation: Option<ElevationIndex>,
        cx: &mut WindowContext,
    ) -> ButtonLikeStyles {
        match self {
            ButtonStyle::Filled => ButtonLikeStyles {
                background: element_bg_from_elevation(elevation, cx),
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Tinted(tint) => tint.button_like_style(cx),
            ButtonStyle::Subtle => ButtonLikeStyles {
                background: cx.theme().colors().ghost_element_background,
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Transparent => ButtonLikeStyles {
                background: transparent_black(),
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
        }
    }

    pub(crate) fn hovered(
        self,
        elevation: Option<ElevationIndex>,
        cx: &mut WindowContext,
    ) -> ButtonLikeStyles {
        match self {
            ButtonStyle::Filled => {
                let mut filled_background = element_bg_from_elevation(elevation, cx);
                filled_background.fade_out(0.92);

                ButtonLikeStyles {
                    background: filled_background,
                    border_color: transparent_black(),
                    label_color: Color::Default.color(cx),
                    icon_color: Color::Default.color(cx),
                }
            }
            ButtonStyle::Tinted(tint) => {
                let mut styles = tint.button_like_style(cx);
                let theme = cx.theme();
                styles.background = theme.darken(styles.background, 0.05, 0.2);
                styles
            }
            ButtonStyle::Subtle => ButtonLikeStyles {
                background: cx.theme().colors().ghost_element_hover,
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Transparent => ButtonLikeStyles {
                background: transparent_black(),
                border_color: transparent_black(),
                // TODO: These are not great
                label_color: Color::Muted.color(cx),
                // TODO: These are not great
                icon_color: Color::Muted.color(cx),
            },
        }
    }

    pub(crate) fn active(self, cx: &mut WindowContext) -> ButtonLikeStyles {
        match self {
            ButtonStyle::Filled => ButtonLikeStyles {
                background: cx.theme().colors().element_active,
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Tinted(tint) => tint.button_like_style(cx),
            ButtonStyle::Subtle => ButtonLikeStyles {
                background: cx.theme().colors().ghost_element_active,
                border_color: transparent_black(),
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Transparent => ButtonLikeStyles {
                background: transparent_black(),
                border_color: transparent_black(),
                // TODO: These are not great
                label_color: Color::Muted.color(cx),
                // TODO: These are not great
                icon_color: Color::Muted.color(cx),
            },
        }
    }

    #[allow(unused)]
    pub(crate) fn focused(self, cx: &mut WindowContext) -> ButtonLikeStyles {
        match self {
            ButtonStyle::Filled => ButtonLikeStyles {
                background: cx.theme().colors().element_background,
                border_color: cx.theme().colors().border_focused,
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Tinted(tint) => tint.button_like_style(cx),
            ButtonStyle::Subtle => ButtonLikeStyles {
                background: cx.theme().colors().ghost_element_background,
                border_color: cx.theme().colors().border_focused,
                label_color: Color::Default.color(cx),
                icon_color: Color::Default.color(cx),
            },
            ButtonStyle::Transparent => ButtonLikeStyles {
                background: transparent_black(),
                border_color: cx.theme().colors().border_focused,
                label_color: Color::Accent.color(cx),
                icon_color: Color::Accent.color(cx),
            },
        }
    }

    #[allow(unused)]
    pub(crate) fn disabled(
        self,
        elevation: Option<ElevationIndex>,
        cx: &mut WindowContext,
    ) -> ButtonLikeStyles {
        match self {
            ButtonStyle::Filled => ButtonLikeStyles {
                background: cx.theme().colors().element_disabled,
                border_color: cx.theme().colors().border_disabled,
                label_color: Color::Disabled.color(cx),
                icon_color: Color::Disabled.color(cx),
            },
            ButtonStyle::Tinted(tint) => tint.button_like_style(cx),
            ButtonStyle::Subtle => ButtonLikeStyles {
                background: cx.theme().colors().ghost_element_disabled,
                border_color: cx.theme().colors().border_disabled,
                label_color: Color::Disabled.color(cx),
                icon_color: Color::Disabled.color(cx),
            },
            ButtonStyle::Transparent => ButtonLikeStyles {
                background: transparent_black(),
                border_color: transparent_black(),
                label_color: Color::Disabled.color(cx),
                icon_color: Color::Disabled.color(cx),
            },
        }
    }
}

/// The height of a button.
///
/// Can also be used to size non-button elements to align with [`Button`]s.
#[derive(Default, PartialEq, Clone, Copy)]
pub enum ButtonSize {
    Large,
    #[default]
    Default,
    Compact,
    None,
}

impl ButtonSize {
    pub fn rems(self) -> Rems {
        match self {
            ButtonSize::Large => rems_from_px(32.),
            ButtonSize::Default => rems_from_px(22.),
            ButtonSize::Compact => rems_from_px(18.),
            ButtonSize::None => rems_from_px(16.),
        }
    }
}

/// A button-like element that can be used to create a custom button when
/// prebuilt buttons are not sufficient. Use this sparingly, as it is
/// unconstrained and may make the UI feel less consistent.
///
/// This is also used to build the prebuilt buttons.
#[derive(IntoElement)]
pub struct ButtonLike {
    pub(super) base: Div,
    id: ElementId,
    pub(super) style: ButtonStyle,
    pub(super) disabled: bool,
    pub(super) selected: bool,
    pub(super) selected_style: Option<ButtonStyle>,
    pub(super) width: Option<DefiniteLength>,
    pub(super) height: Option<DefiniteLength>,
    pub(super) layer: Option<ElevationIndex>,
    size: ButtonSize,
    rounding: Option<ButtonLikeRounding>,
    tooltip: Option<Box<dyn Fn(&mut WindowContext) -> AnyView>>,
    cursor_style: CursorStyle,
    on_click: Option<Box<dyn Fn(&ClickEvent, &mut WindowContext) + 'static>>,
    children: SmallVec<[AnyElement; 2]>,
}

impl ButtonLike {
    pub fn new(id: impl Into<ElementId>) -> Self {
        Self {
            base: div(),
            id: id.into(),
            style: ButtonStyle::default(),
            disabled: false,
            selected: false,
            selected_style: None,
            width: None,
            height: None,
            size: ButtonSize::Default,
            rounding: Some(ButtonLikeRounding::All),
            tooltip: None,
            children: SmallVec::new(),
            cursor_style: CursorStyle::PointingHand,
            on_click: None,
            layer: None,
        }
    }

    pub fn new_rounded_left(id: impl Into<ElementId>) -> Self {
        Self::new(id).rounding(ButtonLikeRounding::Left)
    }

    pub fn new_rounded_right(id: impl Into<ElementId>) -> Self {
        Self::new(id).rounding(ButtonLikeRounding::Right)
    }

    pub(crate) fn height(mut self, height: DefiniteLength) -> Self {
        self.height = Some(height);
        self
    }

    pub(crate) fn rounding(mut self, rounding: impl Into<Option<ButtonLikeRounding>>) -> Self {
        self.rounding = rounding.into();
        self
    }
}

impl Disableable for ButtonLike {
    fn disabled(mut self, disabled: bool) -> Self {
        self.disabled = disabled;
        self
    }
}

impl Selectable for ButtonLike {
    fn selected(mut self, selected: bool) -> Self {
        self.selected = selected;
        self
    }
}

impl SelectableButton for ButtonLike {
    fn selected_style(mut self, style: ButtonStyle) -> Self {
        self.selected_style = Some(style);
        self
    }
}

impl Clickable for ButtonLike {
    fn on_click(mut self, handler: impl Fn(&ClickEvent, &mut WindowContext) + 'static) -> Self {
        self.on_click = Some(Box::new(handler));
        self
    }

    fn cursor_style(mut self, cursor_style: CursorStyle) -> Self {
        self.cursor_style = cursor_style;
        self
    }
}

impl FixedWidth for ButtonLike {
    fn width(mut self, width: DefiniteLength) -> Self {
        self.width = Some(width);
        self
    }

    fn full_width(mut self) -> Self {
        self.width = Some(relative(1.));
        self
    }
}

impl ButtonCommon for ButtonLike {
    fn id(&self) -> &ElementId {
        &self.id
    }

    fn style(mut self, style: ButtonStyle) -> Self {
        self.style = style;
        self
    }

    fn size(mut self, size: ButtonSize) -> Self {
        self.size = size;
        self
    }

    fn tooltip(mut self, tooltip: impl Fn(&mut WindowContext) -> AnyView + 'static) -> Self {
        self.tooltip = Some(Box::new(tooltip));
        self
    }

    fn layer(mut self, elevation: ElevationIndex) -> Self {
        self.layer = Some(elevation);
        self
    }
}

impl VisibleOnHover for ButtonLike {
    fn visible_on_hover(mut self, group_name: impl Into<SharedString>) -> Self {
        self.base = self.base.visible_on_hover(group_name);
        self
    }
}

impl ParentElement for ButtonLike {
    fn extend(&mut self, elements: impl IntoIterator<Item = AnyElement>) {
        self.children.extend(elements)
    }
}

impl RenderOnce for ButtonLike {
    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
        let style = self
            .selected_style
            .filter(|_| self.selected)
            .unwrap_or(self.style);

        self.base
            .h_flex()
            .id(self.id.clone())
            .group("")
            .flex_none()
            .h(self.height.unwrap_or(self.size.rems().into()))
            .when_some(self.width, |this, width| this.w(width).justify_center())
            .when_some(self.rounding, |this, rounding| match rounding {
                ButtonLikeRounding::All => this.rounded_md(),
                ButtonLikeRounding::Left => this.rounded_l_md(),
                ButtonLikeRounding::Right => this.rounded_r_md(),
            })
            .gap(DynamicSpacing::Base04.rems(cx))
            .map(|this| match self.size {
                ButtonSize::Large => this.px(DynamicSpacing::Base06.rems(cx)),
                ButtonSize::Default | ButtonSize::Compact => {
                    this.px(DynamicSpacing::Base04.rems(cx))
                }
                ButtonSize::None => this,
            })
            .bg(style.enabled(self.layer, cx).background)
            .when(self.disabled, |this| this.cursor_not_allowed())
            .when(!self.disabled, |this| {
                this.cursor_pointer()
                    .hover(|hover| hover.bg(style.hovered(self.layer, cx).background))
                    .active(|active| active.bg(style.active(cx).background))
            })
            .when_some(
                self.on_click.filter(|_| !self.disabled),
                |this, on_click| {
                    this.on_mouse_down(MouseButton::Left, |_, cx| cx.prevent_default())
                        .on_click(move |event, cx| {
                            cx.stop_propagation();
                            (on_click)(event, cx)
                        })
                },
            )
            .when_some(self.tooltip, |this, tooltip| {
                this.tooltip(move |cx| tooltip(cx))
            })
            .children(self.children)
    }
}
