organic/src/parser/nom_context.rs

use nom::combinator::not;
use nom::combinator::recognize;
use nom::complete::take;
use nom::error::ErrorKind;
use nom::error::ParseError;
use nom::error::VerboseError;
use nom::IResult;
use std::borrow::Cow;

use super::text::bold_end;
use super::text::Res;

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

pub trait OrgModeContext<'r> {
    fn get_fail_matcher(&'r self) -> Cow<ChainBehavior<'r>>;
}

struct FailMatcherNode<'r> {
    fail_matcher: ChainBehavior<'r>,
}

struct PreviousElementNode<'r> {
    dummy: &'r str,
}

#[derive(Clone)]
pub enum ChainBehavior<'r> {
    AndParent(Option<&'r Matcher>),
    IgnoreParent(Option<&'r Matcher>),
}

struct Node<'r, T: 'r + ?Sized> {
    elem: &'r T,
    parent: Link<'r, T>,
}

pub struct ContextTree<'r, T: 'r + ?Sized> {
    // Not using Link so the ContextTree can own this node
    head: Option<Node<'r, T>>,
}

impl<'r> ContextTree<'r, dyn OrgModeContext<'r>> {
    pub fn new() -> Self {
        ContextTree { head: None }
    }

    pub fn with_additional_node(
        &'r self,
        new_elem: &'r dyn OrgModeContext<'r>,
    ) -> ContextTree<'r, dyn OrgModeContext<'r>> {
        let new_node = Node {
            elem: new_elem,
            parent: self.head.as_ref(),
        };
        ContextTree {
            head: Some(new_node),
        }
    }

    pub fn check_fail_matcher<'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.expect("while loop asserts current_node is some.");
            let current_fail_matcher = current_node_unwrapped.elem.get_fail_matcher();
            match current_fail_matcher.as_ref() {
                ChainBehavior::AndParent(Some(matcher)) => {
                    let local_result = matcher(i);
                    if local_result.is_ok() {
                        return local_result;
                    }
                }
                ChainBehavior::AndParent(None) => {}
                ChainBehavior::IgnoreParent(Some(matcher)) => {
                    return matcher(i);
                }
                ChainBehavior::IgnoreParent(None) => {
                    // TODO: Make this a custom error
                    return Err(nom::Err::Error(VerboseError::from_error_kind(
                        i,
                        ErrorKind::ManyTill,
                    )));
                }
            };
            current_node = current_node
                .map(|current_head| current_head.parent)
                .flatten();
        }
        // TODO: Make this a custom error
        return Err(nom::Err::Error(VerboseError::from_error_kind(
            i,
            ErrorKind::ManyTill,
        )));
    }
}

impl<'r> OrgModeContext<'r> for FailMatcherNode<'r> {
    fn get_fail_matcher(&'r self) -> Cow<ChainBehavior<'r>> {
        Cow::Borrowed(&self.fail_matcher)
    }
}

impl<'r> OrgModeContext<'r> for PreviousElementNode<'r> {
    fn get_fail_matcher(&'r self) -> Cow<ChainBehavior<'r>> {
        Cow::Owned(ChainBehavior::AndParent(None))
    }
}

fn recognize_bold_end(input: &str) -> Res<&str, &str> {
    recognize(bold_end)(input)
}

fn test_context() {
    let foo = "foo";
    let context = ContextTree::new();
    let child1_context = PreviousElementNode { dummy: foo };
    let child1 = context.with_additional_node(&child1_context);
    let child2_context = FailMatcherNode {
        fail_matcher: ChainBehavior::AndParent(Some(&recognize_bold_end)),
    };
    let child2 = child1.with_additional_node(&child2_context);
}

impl<'r, T> std::fmt::Debug for ContextTree<'r, T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "ContextTree")
    }
}