anathema-widgets 0.2.11

// -----------------------------------------------------------------------------
//   - Here be dragons -
//   This code needs cleaning up.
//
//   At some point this should be better documented and broken
//   into smaller pieces.
//
//   TODO: clean this blessed mess
// -----------------------------------------------------------------------------
use std::ops::ControlFlow;

use anathema_state::Value as StateValue;
use anathema_templates::blueprints::Blueprint;
use anathema_value_resolver::{AttributeStorage, Scope};

use crate::error::Result;
use crate::layout::{LayoutCtx, LayoutFilter};
use crate::nodes::loops::Iteration;
use crate::nodes::{controlflow, eval_blueprint};
use crate::widget::WidgetTreeView;
use crate::{Element, WidgetContainer, WidgetId, WidgetKind};

pub mod debug;

// TODO:
// Add the option to "skip" values with an offset for `inner_each` (this is for overflow widgets)
// Note that this might not be possible, depending on how widget generation goes

/// Determine what kind of widgets that should be laid out:
/// Fixed or floating.
#[derive(Debug, Copy, Clone)]
pub enum WidgetPositionFilter {
    Floating,
    Fixed,
    All,
    None,
}

#[derive(Debug, Copy, Clone)]
pub enum Generator<'widget, 'bp> {
    Single {
        ident: &'bp str,
        body: &'bp [Blueprint],
    },
    Loop {
        len: usize,
        binding: &'bp str,
        body: &'bp [Blueprint],
    },
    Iteration {
        binding: &'bp str,
        body: &'bp [Blueprint],
    },
    With {
        binding: &'bp str,
        body: &'bp [Blueprint],
    },
    ControlFlow(&'widget controlflow::ControlFlow<'bp>),
    ControlFlowContainer(&'bp [Blueprint]),
    Slot(&'bp [Blueprint]),
}

impl<'widget, 'bp> Generator<'widget, 'bp> {
    fn from_loop(body: &'bp [Blueprint], binding: &'bp str, len: usize) -> Self {
        Self::Loop { binding, body, len }
    }

    fn from_with(body: &'bp [Blueprint], binding: &'bp str) -> Self {
        Self::With { binding, body }
    }
}

impl<'widget, 'bp> From<&'widget WidgetContainer<'bp>> for Generator<'widget, 'bp> {
    fn from(widget: &'widget WidgetContainer<'bp>) -> Self {
        match &widget.kind {
            WidgetKind::Element(_) => panic!("use Self::Single directly"),
            WidgetKind::For(_) => panic!("use Self::Loop directly"),
            WidgetKind::With(_) => panic!("use Self::With directly"),
            WidgetKind::ControlFlowContainer(_) => Self::ControlFlowContainer(widget.children),
            WidgetKind::Component(comp) => Self::Single {
                ident: comp.name,
                body: widget.children,
            },
            WidgetKind::Iteration(iter) => Self::Iteration {
                binding: iter.binding,
                body: widget.children,
            },
            WidgetKind::ControlFlow(controlflow) => Self::ControlFlow(controlflow),
            WidgetKind::Slot => Self::Slot(widget.children),
        }
    }
}

// -----------------------------------------------------------------------------
//   - Layout -
// -----------------------------------------------------------------------------
#[derive(Debug)]
pub struct LayoutForEach<'a, 'bp> {
    tree: WidgetTreeView<'a, 'bp>,
    scope: &'a Scope<'a, 'bp>,
    generator: Option<Generator<'a, 'bp>>,
    parent_component: Option<WidgetId>,
    filter: LayoutFilter,
}

impl<'a, 'bp> LayoutForEach<'a, 'bp> {
    pub fn new(
        tree: WidgetTreeView<'a, 'bp>,
        scope: &'a Scope<'a, 'bp>,
        filter: LayoutFilter,
        parent_component: Option<WidgetId>,
    ) -> Self {
        Self {
            tree,
            scope,
            generator: None,
            parent_component,
            filter,
        }
    }

    fn with_generator(
        tree: WidgetTreeView<'a, 'bp>,
        scope: &'a Scope<'a, 'bp>,
        generator: Generator<'a, 'bp>,
        filter: LayoutFilter,
        parent_component: Option<WidgetId>,
    ) -> Self {
        Self {
            tree,
            scope,
            generator: Some(generator),
            filter,
            parent_component,
        }
    }

    // pub fn first<F>(&mut self, ctx: &mut LayoutCtx<'_, 'bp>, mut f: F) -> Result<ControlFlow<()>>
    // where
    //     F: FnMut(&mut LayoutCtx<'_, 'bp>, &mut Element<'bp>, LayoutForEach<'_, 'bp>) -> Result<ControlFlow<()>>,
    // {
    //     self.inner_each(ctx, &mut f)
    // }

    pub fn each<F>(&mut self, ctx: &mut LayoutCtx<'_, 'bp>, mut f: F) -> Result<ControlFlow<()>>
    where
        F: FnMut(&mut LayoutCtx<'_, 'bp>, &mut Element<'bp>, LayoutForEach<'_, 'bp>) -> Result<ControlFlow<()>>,
    {
        self.inner_each(ctx, &mut f)
    }

    fn inner_each<F>(&mut self, ctx: &mut LayoutCtx<'_, 'bp>, f: &mut F) -> Result<ControlFlow<()>>
    where
        F: FnMut(&mut LayoutCtx<'_, 'bp>, &mut Element<'bp>, LayoutForEach<'_, 'bp>) -> Result<ControlFlow<()>>,
    {
        for index in 0..self.tree.layout_len() {
            match self.process(index, ctx, f)? {
                ControlFlow::Continue(_) => continue,
                ControlFlow::Break(_) => return Ok(ControlFlow::Break(())),
            }
        }

        // If there is no parent then there can be no children generated
        let Some(parent) = self.generator else { return Ok(ControlFlow::Continue(())) };

        // NOTE: Generate will never happen unless the preceding iteration returns `Continue(())`.
        //       Therefore there is no need to worry about excessive creation of `Iter`s for loops.
        loop {
            let index = self.tree.layout_len();
            if !generate(parent, &mut self.tree, ctx, self.scope, self.parent_component)? {
                break;
            }
            match self.process(index, ctx, f)? {
                ControlFlow::Continue(_) => continue,
                ControlFlow::Break(_) => return Ok(ControlFlow::Break(())),
            }
        }

        Ok(ControlFlow::Continue(()))
    }

    // TODO: this function is gross and large
    fn process<F>(&mut self, index: usize, ctx: &mut LayoutCtx<'_, 'bp>, f: &mut F) -> Result<ControlFlow<()>>
    where
        F: FnMut(&mut LayoutCtx<'_, 'bp>, &mut Element<'bp>, LayoutForEach<'_, 'bp>) -> Result<ControlFlow<()>>,
    {
        let node = self
            .tree
            .layout
            .get(index)
            .expect("widgets are always generated before processed");

        let widget_id = node.value();

        self.tree
            .with_value_mut(widget_id, |_, widget, children| {
                let output = self.filter.filter(widget, ctx.attribute_storage);
                if let FilterOutput::Exclude = output {
                    return Ok(ControlFlow::Continue(()));
                }

                match &mut widget.kind {
                    WidgetKind::Element(el) => {
                        let children = LayoutForEach::with_generator(
                            children,
                            self.scope,
                            Generator::Single {
                                ident: el.ident,
                                body: widget.children,
                            },
                            self.filter,
                            self.parent_component,
                        );
                        f(ctx, el, children)
                    }
                    WidgetKind::ControlFlow(_) => {
                        let generator = Generator::from(&*widget);
                        let mut children = LayoutForEach::with_generator(
                            children,
                            self.scope,
                            generator,
                            self.filter,
                            self.parent_component,
                        );
                        children.inner_each(ctx, f)
                    }
                    WidgetKind::For(for_loop) => {
                        let len = for_loop.collection.len();
                        if len == 0 {
                            return Ok(ControlFlow::Break(()));
                        }

                        let scope = Scope::with_collection(&for_loop.collection, self.scope);
                        let mut children = LayoutForEach::with_generator(
                            children,
                            &scope,
                            Generator::from_loop(widget.children, for_loop.binding, len),
                            self.filter,
                            self.parent_component,
                        );

                        children.inner_each(ctx, f)
                    }
                    WidgetKind::Iteration(iteration) => {
                        let loop_index = *iteration.loop_index.to_ref() as usize;
                        let scope = Scope::with_index(
                            iteration.binding,
                            loop_index,
                            self.scope,
                            iteration.loop_index.reference(),
                        );
                        let mut children = LayoutForEach::with_generator(
                            children,
                            &scope,
                            Generator::from(&*widget),
                            self.filter,
                            self.parent_component,
                        );
                        children.inner_each(ctx, f)
                    }
                    WidgetKind::With(with) => {
                        let scope = Scope::with_value(with.binding, &with.data, self.scope);
                        let mut children = LayoutForEach::with_generator(
                            children,
                            &scope,
                            Generator::from_with(widget.children, with.binding),
                            self.filter,
                            self.parent_component,
                        );

                        children.inner_each(ctx, f)
                    }
                    WidgetKind::Component(component) => {
                        let parent_component = component.widget_id;
                        let state_id = component.state_id();
                        let scope = Scope::with_component(state_id, component.widget_id, Some(self.scope));
                        let mut children = LayoutForEach::with_generator(
                            children,
                            &scope,
                            Generator::from(&*widget),
                            self.filter,
                            Some(parent_component),
                        );
                        children.inner_each(ctx, f)
                    }
                    WidgetKind::ControlFlowContainer(_) => {
                        let mut children = LayoutForEach::with_generator(
                            children,
                            self.scope,
                            Generator::from(&*widget),
                            self.filter,
                            self.parent_component,
                        );
                        children.inner_each(ctx, f)
                    }
                    WidgetKind::Slot => {
                        let mut children = LayoutForEach::with_generator(
                            children,
                            self.scope.outer(),
                            Generator::from(&*widget),
                            self.filter,
                            self.parent_component,
                        );
                        children.inner_each(ctx, f)
                    }
                }
            })
            .unwrap_or(Ok(ControlFlow::Continue(())))
    }

    pub(crate) fn len(&self) -> usize {
        self.tree.layout_len()
    }
}

// Generate the next available widget into the tree
// TODO: break this down into more manageable code.
//       this is a hot mess
fn generate<'bp>(
    parent: Generator<'_, 'bp>,
    tree: &mut WidgetTreeView<'_, 'bp>,
    ctx: &mut LayoutCtx<'_, 'bp>,
    scope: &Scope<'_, 'bp>,
    parent_component: Option<WidgetId>,
) -> Result<bool> {
    match parent {
        Generator::Single { body: blueprints, .. }
        | Generator::Iteration { body: blueprints, .. }
        | Generator::With { body: blueprints, .. }
        | Generator::ControlFlowContainer(blueprints) => {
            if blueprints.is_empty() {
                return Ok(false);
            }

            let index = tree.layout_len();
            if index >= blueprints.len() {
                return Ok(false);
            }

            let mut ctx = ctx.eval_ctx(parent_component);
            // TODO: unwrap.
            // this should propagate somewhere useful
            eval_blueprint(&blueprints[index], &mut ctx, scope, tree.offset, tree)?;
            Ok(true)
        }

        Generator::Slot(blueprints) => {
            if blueprints.is_empty() {
                return Ok(false);
            }

            let index = tree.layout_len();
            if index >= blueprints.len() {
                return Ok(false);
            }

            let mut ctx = ctx.eval_ctx(parent_component);
            eval_blueprint(&blueprints[index], &mut ctx, scope, tree.offset, tree).unwrap();
            Ok(true)
        }
        Generator::Loop { len, .. } if len == tree.layout_len() => Ok(false),
        Generator::Loop { binding, body, .. } => {
            let loop_index = tree.layout_len();

            let transaction = tree.insert(tree.offset);
            let widget = WidgetKind::Iteration(Iteration {
                loop_index: StateValue::new(loop_index as i64),
                binding,
            });
            let widget = WidgetContainer::new(widget, body);
            // NOTE: for this to fail one of the values along the path would have to
            // have been removed
            transaction.commit_child(widget).unwrap();
            Ok(true)
        }
        Generator::ControlFlow(controlflow) => {
            let child_count = tree.layout_len();
            assert_eq!(child_count.saturating_sub(1), 0, "too many branches have been created");

            // TODO: this could probably be replaced with the functionality in
            // ControlFlow::has_changed

            let should_create = {
                if child_count == 0 {
                    true
                } else {
                    let node_id = tree.layout[0].value();
                    let (_, widget) = tree
                        .values
                        .get(node_id)
                        .expect("because the node exists, the value exist");

                    let is_true = match &widget.kind {
                        WidgetKind::ControlFlowContainer(id) => controlflow.elses[*id as usize].is_true(),
                        _ => unreachable!("the child of `ControlFlow` can only be `Else`"),
                    };

                    // The condition no longer holds so the branch has to be trimmed
                    if is_true {
                        return Ok(false);
                    }

                    is_true
                }
            };

            if !should_create {
                return Ok(false);
            }

            let thing = controlflow
                .elses
                .iter()
                .enumerate()
                .filter_map(|(id, node)| {
                    // If there is a condition but it's not a bool, then it's false
                    // If there is no condition then it's true (a conditionless else)
                    // Everything else is down to the value
                    let cond = match node.cond.as_ref() {
                        Some(val) => val.truthiness(),
                        None => true,
                    };
                    match cond {
                        true => Some((id, node.body)),
                        false => None,
                    }
                })
                .next();

            match thing {
                Some((id, body)) => {
                    let kind = WidgetKind::ControlFlowContainer(id as u16);
                    let widget = WidgetContainer::new(kind, body);
                    let transaction = tree.insert(tree.offset);
                    transaction.commit_child(widget);
                }
                None => return Ok(false),
            }

            Ok(true)
        }
    }
}

#[derive(Debug)]
pub enum FilterOutput<T, F> {
    Include(T, F),
    Exclude,
    Continue,
}

pub trait Filter<'bp>: std::fmt::Debug + Copy {
    type Output: std::fmt::Debug;

    fn filter<'a>(
        &mut self,
        widget: &'a mut WidgetContainer<'bp>,
        attribute_storage: &AttributeStorage<'_>,
    ) -> FilterOutput<&'a mut Self::Output, Self>;
}

// -----------------------------------------------------------------------------
//   - Position / Paint -
// -----------------------------------------------------------------------------
#[derive(Debug)]
pub struct ForEach<'a, 'bp, Fltr> {
    tree: WidgetTreeView<'a, 'bp>,
    attribute_storage: &'a AttributeStorage<'bp>,
    pub filter: Fltr,
}

impl<'a, 'bp, Fltr: Filter<'bp>> ForEach<'a, 'bp, Fltr> {
    pub fn new(tree: WidgetTreeView<'a, 'bp>, attribute_storage: &'a AttributeStorage<'bp>, filter: Fltr) -> Self {
        Self {
            tree,
            attribute_storage,
            filter,
        }
    }

    pub fn each<F>(&mut self, mut f: F) -> ControlFlow<()>
    where
        F: FnMut(&mut Fltr::Output, ForEach<'_, 'bp, Fltr>) -> ControlFlow<()>,
    {
        self.inner_each(&mut f)
    }

    fn inner_each<F>(&mut self, f: &mut F) -> ControlFlow<()>
    where
        F: FnMut(&mut Fltr::Output, ForEach<'_, 'bp, Fltr>) -> ControlFlow<()>,
    {
        for index in 0..self.tree.layout_len() {
            _ = self.process(index, f);
        }

        ControlFlow::Continue(())
    }

    fn process<F>(&mut self, index: usize, f: &mut F) -> ControlFlow<()>
    where
        F: FnMut(&mut Fltr::Output, ForEach<'_, 'bp, Fltr>) -> ControlFlow<()>,
    {
        let Some(node) = self.tree.layout.get(index) else { panic!() };
        self.tree
            .with_value_mut(node.value(), |_, widget, children| {
                match self.filter.filter(widget, self.attribute_storage) {
                    FilterOutput::Include(el, filter) => f(el, ForEach::new(children, self.attribute_storage, filter)),
                    FilterOutput::Exclude => ControlFlow::Break(()),
                    FilterOutput::Continue => ForEach::new(children, self.attribute_storage, self.filter).inner_each(f),
                }
            })
            .unwrap() // TODO: unwrap...
    }
}