//! A single element of text.
use crate::parser::parser_with_context::parser_with_context;
use crate::parser::text::paragraph_end;

use super::combinator::context_many1;
use super::combinator::context_many_till;
use super::error::CustomError;
use super::error::MyError;
use super::nom_context::ChainBehavior;
use super::nom_context::ContextElement;
use super::nom_context::ContextTree;
use super::nom_context::ExitMatcherNode;
use super::nom_context::PreviousElementNode;
use super::text::bold_end;
use super::text::bold_start;
use super::text::line_break;
use super::text::link_end;
use super::text::link_start;
use super::text::space;
use super::text::span;
use super::text::symbol;
use super::text::Bold;
use super::text::Link;
use super::text::Paragraph;
use super::text::Res;
use super::text::TextElement;
use super::token::Token;
use super::Context;
use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::bytes::complete::take;
use nom::combinator::cond;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::error::ErrorKind;
use nom::error::ParseError;
use nom::error::VerboseError;
use nom::multi::many1;
use nom::multi::many_till;
use nom::sequence::tuple;
use nom::IResult;
use nom::InputLength;

type UnboundMatcher<'r, 's, I, O, E> = dyn Fn(Context<'r, 's>, I) -> IResult<I, O, E>;

pub fn document(input: &str) -> Res<&str, Vec<Paragraph>> {
    let initial_context: ContextTree<'_, '_> = ContextTree::new();
    let (remaining, tokens) = context_many1(&initial_context, paragraph)(input)?;
    let paragraphs = tokens.into_iter().map(|token| {
        match token {
            Token::TextElement(_) => unreachable!(),
            Token::Paragraph(paragraph) => paragraph,
        }
    }).collect();
    Ok((remaining, paragraphs))
}

pub fn context_paragraph_end<'s, 'r>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, &'s str> {
    paragraph_end(input)
}

fn can_start_bold<'s, 'r>(context: Context<'r, 's>) -> bool {
    _preceded_by_whitespace(context) && !_in_section(context, "bold")
}

fn _in_section<'s, 'r, 'x>(context: Context<'r, 's>, section_name: &'x str) -> bool {
    for thing in context.iter() {
        match thing.get_data() {
            ContextElement::ExitMatcherNode(_) => {}
            ContextElement::PreviousElementNode(_) => {}
            ContextElement::Context(name) if *name == section_name => return true,
            ContextElement::Context(_) => {}
            ContextElement::StartOfParagraph => {} // TODO: If we specialize this to bold then this would be a good spot to stop scanning
        }
    }
    false
}

fn _preceded_by_whitespace<'s, 'r>(context: Context<'r, 's>) -> bool {
    let mut context_iterator = context.iter().enumerate();
    loop {
        if let Some((i, ctx)) = context_iterator.next() {
            match ctx.get_data() {
                ContextElement::ExitMatcherNode(_) => {}
                ContextElement::PreviousElementNode(previous_element_node) => {
                    match &previous_element_node.element {
                        Token::TextElement(text_element) => {
                            match text_element {
                                TextElement::Span(_) => return false,
                                TextElement::Space(_) => return true,
                                TextElement::LineBreak(_) => return true,
                                TextElement::Symbol(_) => return false,
                                TextElement::Bold(_) => return false,
                                TextElement::Link(_) => return false,
                            };
                        }
                        Token::Paragraph(_) => unreachable!(),
                    };
                }
                ContextElement::StartOfParagraph => {
                    return true;
                }
                ContextElement::Context(_) => {}
            }
        } else {
            break;
        }
    }
    false
}

pub fn context_bold_start<'s, 'r>(
    context: Context<'r, 's>,
    input: &'s str,
) -> Res<&'s str, &'s str> {
    if can_start_bold(context) {
        recognize(bold_start)(input)
    } else {
        // TODO: Make this a specific error instead of just a generic MyError
        return Err(nom::Err::Error(CustomError::MyError(MyError(
            "Cannot start bold",
        ))));
    }
}

pub fn context_bold_end<'s, 'r>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    let (remaining, actual_match) = recognize(bold_end)(input)?;
    peek(alt((
        // Must have whitespace after the end asterisk or it must be the end of that section (as checked by the exit matcher)
        tag(" "),
        tag("\t"),
        tag("\n"),
        |i| context.check_exit_matcher(i),
    )))(remaining)?;

    Ok((remaining, actual_match))
}

pub fn paragraph<'s, 'r>(context: Context<'r, 's>, i: &'s str) -> Res<&'s str, Paragraph<'s>> {
    // Add a not(eof) check because many_till cannot match a zero-length string
    not(eof)(i)?;
    let paragraph_context = context
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&context_paragraph_end)),
        }))
        .with_additional_node(ContextElement::StartOfParagraph);
    let (remaining, (many, till)) =
        context_many_till(&paragraph_context, flat_text_element, context_paragraph_end)(i)?;
    let many = many
        .into_iter()
        .filter_map(|token| match token {
            Token::TextElement(text_element) => Some(text_element),
            Token::Paragraph(_) => panic!("There should only be text elements in paragraphs."),
        })
        .collect();
    Ok((
        remaining,
        Paragraph {
            contents: many,
            paragraph_end: till,
        },
    ))
}

fn flat_text_element<'s, 'r>(
    context: Context<'r, 's>,
    i: &'s str,
) -> Res<&'s str, TextElement<'s>> {
    not(|i| context.check_exit_matcher(i))(i)?;

    let bold_matcher = parser_with_context!(flat_bold)(&context);
    let link_matcher = parser_with_context!(flat_link)(&context);

    alt((
        map(bold_matcher, TextElement::Bold),
        map(link_matcher, TextElement::Link),
        map(span, TextElement::Span),
        map(symbol("*"), TextElement::Symbol),
        map(symbol("["), TextElement::Symbol),
        map(symbol("]"), TextElement::Symbol),
        map(space, TextElement::Space),
        map(line_break, TextElement::LineBreak),
    ))(i)
}

fn flat_bold<'s, 'r>(context: Context<'r, 's>, i: &'s str) -> Res<&'s str, Bold<'s>> {
    let bold_start = parser_with_context!(context_bold_start)(&context);
    let nom_context = context
        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&context_bold_end)),
        }))
        .with_additional_node(ContextElement::Context("bold"));
    let (remaining, captured) = recognize(tuple((bold_start, |i| {
        context_many_till(&nom_context, flat_text_element, context_bold_end)(i)
    })))(i)?;
    let ret = Bold { contents: captured };
    Ok((remaining, ret))
}

fn recognize_link_end<'s, 'r>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
    recognize(link_end)(input)
}

fn flat_link<'s, 'r>(context: Context<'r, 's>, i: &'s str) -> Res<&'s str, Link<'s>> {
    let nom_context =
        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
            exit_matcher: ChainBehavior::AndParent(Some(&recognize_link_end)),
        }));
    // let nom_context = context.with_additional_exit_matcher(&recognize_link_end);
    let text_element_parser = parser_with_context!(flat_text_element)(&nom_context);
    let (remaining, captured) = recognize(tuple((
        link_start,
        many_till(text_element_parser, link_end),
    )))(i)?;
    let ret = Link { contents: captured };
    Ok((remaining, ret))
}