organic/src/parser/nom_context.rs

use std::cell::RefCell;
use std::rc::Rc;

use nom::branch::alt;
use nom::bytes::complete::take;
use nom::combinator::not;
use nom::error::ContextError;
use nom::error::ErrorKind;
use nom::error::ParseError;
use nom::error::VerboseError;
use nom::IResult;
use nom::Parser;

type Link<'r, T> = Option<&'r Node<'r, T>>;
type Matcher = dyn for<'s> Fn(&'s str) -> IResult<&'s str, &'s str, VerboseError<&'s str>>;
pub type OrgModeContext<'r> = ContextTree<'r, ContextElement<'r>>;

struct Node<'r, T> {
    elem: T,
    next: Link<'r, T>,
}

pub struct ContextTree<'r, T> {
    head: Option<Node<'r, T>>,
}

impl<'r, T> ContextTree<'r, T> {
    pub fn new() -> Self {
        ContextTree { head: None }
    }

    pub fn with_additional_node(&'r self, element: T) -> ContextTree<'r, T> {
        let new_node = Node {
            elem: element,
            next: self.head.as_ref(),
        };

        ContextTree {
            head: Some(new_node),
        }
    }
}

pub struct ContextElement<'r> {
    pub fail_matcher: ChainBehavior<'r>,
}

pub enum ChainBehavior<'r> {
    AndParent(Option<&'r Matcher>),
    IgnoreParent(Option<&'r Matcher>),
}

pub trait OrgModeContextTree<'r> {
    fn with_additional_fail_matcher(&'r self, fail_matcher: &'r Matcher) -> OrgModeContext<'r>;

    fn match_fail<'s>(&'r self, i: &'s str) -> IResult<&'s str, &'s str, VerboseError<&'s str>>;
}

impl<'r> OrgModeContextTree<'r> for OrgModeContext<'r> {
    fn with_additional_fail_matcher(
        &'r self,
        fail_matcher: &'r Matcher,
    ) -> ContextTree<'r, ContextElement<'r>> {
        self.with_additional_node(ContextElement {
            fail_matcher: ChainBehavior::AndParent(Some(fail_matcher)),
        })
    }

    fn match_fail<'s>(&'r self, i: &'s str) -> IResult<&'s str, &'s str, VerboseError<&'s str>> {
        let mut current_node = self.head.as_ref();
        while current_node.is_some() {
            let current_node_unwrapped = current_node
                .as_ref()
                .expect("while loop asserts current_node is some.");
            match current_node_unwrapped.elem.fail_matcher {
                ChainBehavior::AndParent(Some(matcher)) => {
                    let local_result = matcher(i);
                    if local_result.is_ok() {
                        return local_result;
                    }
                }
                ChainBehavior::AndParent(None) => {}
                ChainBehavior::IgnoreParent(Some(matcher)) => {
                    let local_result = matcher(i);
                    if local_result.is_ok() {
                        return local_result;
                    }
                    // TODO: Make this a custom error
                    not(take(0usize))(i)?;
                }
                ChainBehavior::IgnoreParent(None) => {
                    // TODO: Make this a custom error
                    not(take(0usize))(i)?;
                }
            };
            current_node = current_node.map(|current_head| current_head.next).flatten();
        }
        // TODO: Make this a custom error
        not(take(0usize))(i)?;
        unreachable!()
    }
}