// Copyright 2022 System76 <info@system76.com>
// SPDX-License-Identifier: MPL-2.0

use crate::{ext::CollectionWidget, widget, Element};
use apply::Apply;
use derive_setters::Setters;
use iced::{window, Length};
use iced_core::{widget::tree, Widget};
use std::borrow::Cow;

#[must_use]
pub fn header_bar<'a, Message>() -> HeaderBar<'a, Message> {
    HeaderBar {
        title: Cow::Borrowed(""),
        on_close: None,
        on_drag: None,
        on_maximize: None,
        on_minimize: None,
        on_right_click: None,
        start: Vec::new(),
        center: Vec::new(),
        end: Vec::new(),
        focused: false,
    }
}

#[derive(Setters)]
pub struct HeaderBar<'a, Message> {
    /// Defines the title of the window
    #[setters(skip)]
    title: Cow<'a, str>,

    /// A message emitted when the close button is pressed.
    #[setters(strip_option)]
    on_close: Option<Message>,

    /// A message emitted when dragged.
    #[setters(strip_option)]
    on_drag: Option<Message>,

    /// A message emitted when the maximize button is pressed.
    #[setters(strip_option)]
    on_maximize: Option<Message>,

    /// A message emitted when the minimize button is pressed.
    #[setters(strip_option)]
    on_minimize: Option<Message>,

    /// A message emitted when the header is right clicked.
    #[setters(strip_option)]
    on_right_click: Option<Message>,

    /// Focused state of the window
    focused: bool,

    /// Elements packed at the start of the headerbar.
    #[setters(skip)]
    start: Vec<Element<'a, Message>>,

    /// Elements packed in the center of the headerbar.
    #[setters(skip)]
    center: Vec<Element<'a, Message>>,

    /// Elements packed at the end of the headerbar.
    #[setters(skip)]
    end: Vec<Element<'a, Message>>,
}

impl<'a, Message: Clone + 'static> HeaderBar<'a, Message> {
    /// Defines the title of the window
    #[must_use]
    pub fn title(mut self, title: impl Into<Cow<'a, str>> + 'a) -> Self {
        self.title = title.into();
        self
    }

    /// Pushes an element to the start region.
    #[must_use]
    pub fn start(mut self, widget: impl Into<Element<'a, Message>> + 'a) -> Self {
        self.start.push(widget.into());
        self
    }

    /// Pushes an element to the center region.
    #[must_use]
    pub fn center(mut self, widget: impl Into<Element<'a, Message>> + 'a) -> Self {
        self.center.push(widget.into());
        self
    }

    /// Pushes an element to the end region.
    #[must_use]
    pub fn end(mut self, widget: impl Into<Element<'a, Message>> + 'a) -> Self {
        self.end.push(widget.into());
        self
    }

    /// Build the widget
    #[must_use]
    pub fn build(self) -> HeaderBarWidget<'a, Message> {
        HeaderBarWidget {
            header_bar_inner: self.into_element(),
        }
    }
}

pub struct HeaderBarWidget<'a, Message> {
    header_bar_inner: Element<'a, Message>,
}

impl<'a, Message: Clone + 'static> Widget<Message, crate::Theme, crate::Renderer>
    for HeaderBarWidget<'a, Message>
{
    fn diff(&mut self, tree: &mut tree::Tree) {
        tree.diff_children(&mut [&mut self.header_bar_inner]);
    }

    fn children(&self) -> Vec<tree::Tree> {
        vec![tree::Tree::new(&self.header_bar_inner)]
    }

    fn size(&self) -> iced_core::Size<Length> {
        self.header_bar_inner.as_widget().size()
    }

    fn layout(
        &self,
        tree: &mut tree::Tree,
        renderer: &crate::Renderer,
        limits: &iced_core::layout::Limits,
    ) -> iced_core::layout::Node {
        let child_tree = &mut tree.children[0];
        let child = self
            .header_bar_inner
            .as_widget()
            .layout(child_tree, renderer, limits);
        iced_core::layout::Node::with_children(child.size(), vec![child])
    }

    fn draw(
        &self,
        tree: &tree::Tree,
        renderer: &mut crate::Renderer,
        theme: &crate::Theme,
        style: &iced_core::renderer::Style,
        layout: iced_core::Layout<'_>,
        cursor: iced_core::mouse::Cursor,
        viewport: &iced_core::Rectangle,
    ) {
        let layout_children = layout.children().next().unwrap();
        let state_children = &tree.children[0];
        self.header_bar_inner.as_widget().draw(
            state_children,
            renderer,
            theme,
            style,
            layout_children,
            cursor,
            viewport,
        );
    }

    fn on_event(
        &mut self,
        state: &mut tree::Tree,
        event: iced_core::Event,
        layout: iced_core::Layout<'_>,
        cursor: iced_core::mouse::Cursor,
        renderer: &crate::Renderer,
        clipboard: &mut dyn iced_core::Clipboard,
        shell: &mut iced_core::Shell<'_, Message>,
        viewport: &iced_core::Rectangle,
    ) -> iced_core::event::Status {
        let child_state = &mut state.children[0];
        let child_layout = layout.children().next().unwrap();
        self.header_bar_inner.as_widget_mut().on_event(
            child_state,
            event,
            child_layout,
            cursor,
            renderer,
            clipboard,
            shell,
            viewport,
        )
    }

    fn mouse_interaction(
        &self,
        state: &tree::Tree,
        layout: iced_core::Layout<'_>,
        cursor: iced_core::mouse::Cursor,
        viewport: &iced_core::Rectangle,
        renderer: &crate::Renderer,
    ) -> iced_core::mouse::Interaction {
        let child_tree = &state.children[0];
        let child_layout = layout.children().next().unwrap();
        self.header_bar_inner.as_widget().mouse_interaction(
            child_tree,
            child_layout,
            cursor,
            viewport,
            renderer,
        )
    }

    fn operate(
        &self,
        state: &mut tree::Tree,
        layout: iced_core::Layout<'_>,
        renderer: &crate::Renderer,
        operation: &mut dyn iced_core::widget::Operation<
            iced_core::widget::OperationOutputWrapper<Message>,
        >,
    ) {
        let child_tree = &mut state.children[0];
        let child_layout = layout.children().next().unwrap();
        self.header_bar_inner
            .as_widget()
            .operate(child_tree, child_layout, renderer, operation);
    }

    fn overlay<'b>(
        &'b mut self,
        state: &'b mut tree::Tree,
        layout: iced_core::Layout<'_>,
        renderer: &crate::Renderer,
    ) -> Option<iced_core::overlay::Element<'b, Message, crate::Theme, crate::Renderer>> {
        let child_tree = &mut state.children[0];
        let child_layout = layout.children().next().unwrap();
        self.header_bar_inner
            .as_widget_mut()
            .overlay(child_tree, child_layout, renderer)
    }
}

impl<'a, Message: Clone + 'static> HeaderBar<'a, Message> {
    /// Converts the headerbar builder into an Iced element.
    pub fn into_element(mut self) -> Element<'a, Message> {
        // Take ownership of the regions to be packed.
        let start = std::mem::take(&mut self.start);
        let center = std::mem::take(&mut self.center);
        let mut end = std::mem::take(&mut self.end);

        // Also packs the window controls at the very end.
        end.push(widget::horizontal_space(Length::Fixed(12.0)).into());
        end.push(self.window_controls());

        // Creates the headerbar widget.
        let mut widget = widget::row::with_capacity(4)
            // If elements exist in the start region, append them here.
            .push(
                widget::row::with_children(start)
                    .align_items(iced::Alignment::Center)
                    .apply(widget::container)
                    .align_x(iced::alignment::Horizontal::Left)
                    .width(Length::Shrink),
            )
            // If elements exist in the center region, use them here.
            // This will otherwise use the title as a widget if a title was defined.
            .push(if !center.is_empty() {
                widget::row::with_children(center)
                    .align_items(iced::Alignment::Center)
                    .apply(widget::container)
                    .align_x(iced::alignment::Horizontal::Center)
                    .width(Length::Fill)
                    .into()
            } else if self.title.is_empty() {
                widget::horizontal_space(Length::Fill).into()
            } else {
                self.title_widget()
            })
            .push(
                widget::row::with_children(end)
                    .align_items(iced::Alignment::Center)
                    .apply(widget::container)
                    .align_x(iced::alignment::Horizontal::Right)
                    .width(Length::Shrink),
            )
            .align_items(iced::Alignment::Center)
            .height(Length::Fixed(50.0))
            .padding(8)
            .spacing(8)
            .apply(widget::container)
            .style(crate::theme::Container::HeaderBar)
            .center_y()
            .apply(widget::mouse_area);

        // Assigns a message to emit when the headerbar is dragged.
        if let Some(message) = self.on_drag.clone() {
            widget = widget.on_drag(message);
        }

        // Assigns a message to emit when the headerbar is double-clicked.
        if let Some(message) = self.on_maximize.clone() {
            widget = widget.on_release(message);
        }

        if let Some(message) = self.on_right_click.clone() {
            widget = widget.on_right_press(message);
        }

        widget.into()
    }

    fn title_widget(&mut self) -> Element<'a, Message> {
        let mut title = Cow::default();
        std::mem::swap(&mut title, &mut self.title);

        widget::text(title)
            .size(16)
            .font(crate::font::FONT_SEMIBOLD)
            .apply(widget::container)
            .center_x()
            .center_y()
            .width(Length::Fill)
            .height(Length::Fill)
            .into()
    }

    /// Creates the widget for window controls.
    fn window_controls(&mut self) -> Element<'a, Message> {
        let icon = |icon_bytes, size, on_press| {
            widget::icon::from_svg_bytes(icon_bytes)
                .symbolic(true)
                .apply(widget::button::icon)
                .style(crate::theme::Button::HeaderBar)
                .selected(self.focused)
                .icon_size(size)
                .on_press(on_press)
        };

        widget::row::with_capacity(3)
            .push_maybe(self.on_minimize.take().map(|m| {
                icon(
                    &include_bytes!("../../res/icons/window-minimize-symbolic.svg")[..],
                    16,
                    m,
                )
            }))
            .push_maybe(self.on_maximize.take().map(|m| {
                icon(
                    &include_bytes!("../../res/icons/window-maximize-symbolic.svg")[..],
                    16,
                    m,
                )
            }))
            .push_maybe(self.on_close.take().map(|m| {
                icon(
                    &include_bytes!("../../res/icons/window-close-symbolic.svg")[..],
                    16,
                    m,
                )
            }))
            .spacing(8)
            .apply(widget::container)
            .height(Length::Fill)
            .center_y()
            .into()
    }
}

impl<'a, Message: Clone + 'static> From<HeaderBar<'a, Message>> for Element<'a, Message> {
    fn from(headerbar: HeaderBar<'a, Message>) -> Self {
        Element::new(headerbar.build())
    }
}

impl<'a, Message: Clone + 'static> From<HeaderBarWidget<'a, Message>> for Element<'a, Message> {
    fn from(headerbar: HeaderBarWidget<'a, Message>) -> Self {
        Element::new(headerbar)
    }
}