duster/src/renderer/context_element.rs

use crate::parser::Filter;
use crate::renderer::breadcrumb_tree::BreadcrumbTreeElement;
use crate::renderer::errors::RenderError;
use crate::renderer::errors::WalkError;
use crate::renderer::DustRenderer;
use std::any::Any;
use std::rc::Rc;
use std::{cmp::Ordering, fmt::Debug};

pub trait ContextElement:
    Debug
    + Truthiness
    + Walkable
    + Renderable
    + Loopable
    // + CloneIntoBoxedContextElement
    + CompareContextElement
    + FromContextElement
    + IntoRcIce
{
}

pub trait Truthiness {
    fn is_truthy(&self) -> bool;
}

pub trait Walkable {
    fn walk(&self, segment: &str) -> Result<&dyn IntoContextElement, WalkError>;

    /// If an element contains meta information and should not be
    /// returned as the final result of a walk, this function should
    /// return true.
    ///
    /// For example, the iteration context contains $idx and $len but
    /// it should not be the result of a dot-reference like `{.}`.
    fn is_pseudo_element(&self) -> bool {
        false
    }
}

pub trait Renderable {
    fn render(&self, filters: &Vec<Filter>) -> Result<String, RenderError>;
}

pub trait Loopable {
    /// Return the elements for a Dust section
    ///
    /// Sections in dust are accomplished with the {#path} syntax.  If
    /// its an array-like value then it will render n-times, once for
    /// each element of the array. If this is a scalar value, then
    /// return an empty array. Sections with scalar values will still
    /// be rendered (only once) if their truthiness check comes back
    /// true.
    fn get_loop_elements(&self) -> Vec<&dyn ContextElement>;
}

pub trait CastToAny {
    fn to_any(&self) -> &dyn Any;
}

pub trait CompareContextElement: CastToAny {
    fn equals(&self, other: &dyn ContextElement) -> bool;

    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering>;
}

// pub trait CloneIntoBoxedContextElement {
//     fn clone_to_box(&self) -> Box<dyn IntoContextElement>;
// }

// impl<C: 'static + IntoContextElement + Clone> CloneIntoBoxedContextElement for C {
//     fn clone_to_box(&self) -> Box<dyn IntoContextElement> {
//         Box::new(self.clone())
//     }
// }

impl<C: 'static + ContextElement> CastToAny for C {
    fn to_any(&self) -> &dyn Any {
        self
    }
}

impl<'a, 'b> PartialEq<&'b dyn ContextElement> for &'a dyn ContextElement {
    fn eq(&self, other: &&'b dyn ContextElement) -> bool {
        self.equals(*other)
    }
}

impl<'a, 'b> PartialOrd<&'b dyn ContextElement> for &'a dyn ContextElement {
    fn partial_cmp(&self, other: &&'b dyn ContextElement) -> Option<Ordering> {
        self.partial_compare(*other)
    }
}

pub trait FromContextElement {
    fn from_context_element(&self) -> &dyn IntoContextElement;
}

impl<C: ContextElement> FromContextElement for C {
    fn from_context_element(&self) -> &dyn IntoContextElement {
        self
    }
}

pub trait IntoContextElement: Debug + Walkable /* + CloneIntoBoxedContextElement*/ {
    fn into_context_element<'a>(
        &'a self,
        renderer: &DustRenderer,
        breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
    ) -> Option<IceResult<'a>>;
}

impl<C: ContextElement> IntoContextElement for C {
    fn into_context_element<'a>(
        &'a self,
        renderer: &DustRenderer,
        breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
    ) -> Option<IceResult<'a>> {
        Some(IceResult::from_borrowed(self))
    }
}

pub trait IntoRcIce {
    fn into_rc_ice(self: Rc<Self>) -> Rc<dyn IntoContextElement>;
}

impl<C: 'static + ContextElement> IntoRcIce for C {
    fn into_rc_ice(self: Rc<C>) -> Rc<dyn IntoContextElement> {
        Rc::clone(&self) as Rc<dyn IntoContextElement>
    }
}

#[derive(Clone, Debug)]
pub enum IceResult<'a> {
    // Using Rc so that when we need to create BreadcrumbTrees with
    // the same BreadcrumbTreeElement but a different parent (for
    // example, when inserting behind the tail), we don't need to the
    // copy the already owned/malloc'd data.
    Owned(Rc<dyn ContextElement>),
    Borrowed(&'a dyn ContextElement),
}

impl<'a> IceResult<'a> {
    pub fn from_owned<C: 'static + ContextElement>(val: C) -> IceResult<'a> {
        IceResult::Owned(Rc::new(val))
    }

    pub fn from_borrowed(val: &'a dyn ContextElement) -> IceResult<'a> {
        IceResult::Borrowed(val)
    }

    pub fn get_context_element_reference(&self) -> &dyn ContextElement {
        match self {
            IceResult::Owned(rc_ce) => rc_ce.as_ref(),
            IceResult::Borrowed(ce) => *ce,
        }
    }
}

impl<'a> IntoContextElement for IceResult<'a> {
    fn into_context_element<'b>(
        &'b self,
        renderer: &DustRenderer,
        breadcrumbs: &'b Vec<BreadcrumbTreeElement<'b>>,
    ) -> Option<IceResult<'b>> {
        match self {
            IceResult::Owned(rc_ce) => Some(IceResult::from_borrowed(rc_ce.as_ref())),
            IceResult::Borrowed(ce) => Some(IceResult::from_borrowed(*ce)),
        }
    }
}

impl<'a> Walkable for IceResult<'a> {
    fn walk(&self, segment: &str) -> Result<&dyn IntoContextElement, WalkError> {
        self.get_context_element_reference().walk(segment)
    }
}