use crate::renderer::breadcrumb_tree::BreadcrumbTreeElement;
use crate::renderer::context_element::CompareContextElement;
use crate::renderer::context_element::ContextElement;
use crate::renderer::context_element::IceResult;
use crate::renderer::context_element::IntoContextElement;
use crate::renderer::DustRenderer;
use crate::renderer::Loopable;
use crate::renderer::RenderError;
use crate::renderer::Renderable;
use crate::renderer::Truthiness;
use crate::renderer::WalkError;
use crate::{parser::Filter, parser::OwnedLiteral, renderer::Walkable};
use std::convert::TryInto;

use std::cmp::Ordering;

/// An injected context for $idx and $len
///
/// Functions the same as the injected parameters contexts for
/// helpers/partials with parameters but this has no need for storing
/// breadcrumbs since its simply storing two integers.
#[derive(Debug)]
pub struct IterationContext {
    idx: OwnedLiteral,
    len: OwnedLiteral,
}

impl IterationContext {
    pub fn new(idx: usize, len: usize) -> Self {
        // TODO: it would be nice to handle usize vs u64 better
        IterationContext {
            idx: OwnedLiteral::LPositiveInteger(idx.try_into().unwrap()),
            len: OwnedLiteral::LPositiveInteger(len.try_into().unwrap()),
        }
    }
}

impl IntoContextElement for IterationContext {
    fn into_context_element<'b>(
        &'b self,
        renderer: &DustRenderer,
        breadcrumbs: &'b Vec<BreadcrumbTreeElement<'b>>,
    ) -> Option<IceResult<'b>> {
        panic!("into_context_element cannot be called on pseudo elements");
    }
}

impl Walkable for IterationContext {
    fn walk(&self, segment: &str) -> Result<&dyn IntoContextElement, WalkError> {
        match segment {
            "$idx" => Ok(&self.idx),
            "$len" => Ok(&self.len),
            _ => Err(WalkError::CantWalk),
        }
    }

    fn is_pseudo_element(&self) -> bool {
        true
    }
}