use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::anychar;
use nom::character::complete::digit1;
use nom::character::complete::line_ending;
use nom::character::complete::one_of;
use nom::character::complete::space0;
use nom::character::complete::space1;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::opt;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many0;
use nom::multi::many1;
use nom::multi::many_till;
use nom::sequence::tuple;

use super::element_parser::element;
use super::object_parser::standard_set_object;
use super::org_source::OrgSource;
use super::util::include_input;
use super::util::indentation_level;
use super::util::non_whitespace_character;
use crate::context::parser_with_context;
use crate::context::ContextElement;
use crate::context::ContextMatcher;
use crate::context::ExitClass;
use crate::context::ExitMatcherNode;
use crate::context::RefContext;
use crate::error::CustomError;
use crate::error::MyError;
use crate::error::Res;
use crate::parser::util::blank_line;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
use crate::parser::util::org_space;
use crate::parser::util::start_of_line;
use crate::types::CheckboxType;
use crate::types::IndentationLevel;
use crate::types::Object;
use crate::types::PlainList;
use crate::types::PlainListItem;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn detect_plain_list<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, ()> {
    if verify(
        tuple((
            start_of_line,
            space0,
            parser_with_context!(bullet)(context),
            alt((space1, line_ending, eof)),
        )),
        |(_start, indent, (_bullet_type, bull), _after_whitespace)| {
            Into::<&str>::into(bull) != "*" || indent.len() > 0
        },
    )(input)
    .is_ok()
    {
        return Ok((input, ()));
    }
    return Err(nom::Err::Error(CustomError::MyError(MyError(
        "No element detected.".into(),
    ))));
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn plain_list<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, PlainList<'s>> {
    let contexts = [
        ContextElement::Context("plain list"),
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &plain_list_end,
        }),
    ];

    let parser_context = context.with_additional_node(&contexts[0]);
    let parser_context = parser_context.with_additional_node(&contexts[1]);
    let parser_context = parser_context.with_additional_node(&contexts[2]);
    // children stores tuple of (input string, parsed object) so we can re-parse the final item
    let mut children = Vec::new();
    let mut first_item_indentation: Option<IndentationLevel> = None;
    let mut remaining = input;

    // The final list item does not consume trailing blank lines (which instead get consumed by the list). We have three options here:
    //
    // 1. Parse all items while consuming trailing whitespace, then edit the final item to remove trailing whitespace.
    // 2. Parse all items without consuming trailing whitespace, then edit all but the final one to add in the trailing whitespace.
    // 3. Re-parse the final item with consume trailing whitespace disabled.
    //
    // While #3 is the most slow, it also seems to cleanest and involves the least manual mutation of already-parsed objects so I am going with #3 for now, but we should revisit #1 or #2 when the parser is more developed.

    loop {
        let list_item = parser_with_context!(plain_list_item)(&parser_context)(remaining);
        match list_item {
            Ok((remain, item))
                if item.indentation == *first_item_indentation.get_or_insert(item.indentation) =>
            {
                children.push((remaining, item));
                remaining = remain;
            }
            Ok(_) | Err(_) => {
                break;
            }
        };

        let maybe_exit = parser_with_context!(exit_matcher_parser)(&parser_context)(remaining);
        if maybe_exit.is_ok() {
            break;
        }
    }

    let (final_child_start, _final_item_first_parse) = match children.pop() {
        Some(final_child) => final_child,
        None => {
            return Err(nom::Err::Error(CustomError::MyError(MyError(
                "Plain lists require at least one element.".into(),
            ))));
        }
    };
    let final_item_context = ContextElement::ConsumeTrailingWhitespace(false);
    let final_item_context = parser_context.with_additional_node(&final_item_context);
    let (remaining, reparsed_final_item) =
        parser_with_context!(plain_list_item)(&final_item_context)(final_child_start)?;
    children.push((final_child_start, reparsed_final_item));

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        PlainList {
            source: source.into(),
            children: children.into_iter().map(|(_start, item)| item).collect(),
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn plain_list_item<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, PlainListItem<'s>> {
    start_of_line(input)?;
    let (remaining, (indent_level, _leading_whitespace)) = indentation_level(context, input)?;
    let (remaining, (bullet_type, bull)) = verify(
        parser_with_context!(bullet)(context),
        |(_bullet_type, bull)| Into::<&str>::into(bull) != "*" || indent_level > 0,
    )(remaining)?;

    let (remaining, _maybe_counter_set) = opt(tuple((
        space1,
        tag("[@"),
        parser_with_context!(counter)(context),
        tag("]"),
    )))(remaining)?;

    let (remaining, maybe_checkbox) = opt(tuple((space1, item_checkbox)))(remaining)?;

    let (remaining, maybe_tag) = if let BulletType::Unordered = bullet_type {
        opt(tuple((space1, parser_with_context!(item_tag)(context))))(remaining)?
    } else {
        (remaining, None)
    };

    let exit_matcher = plain_list_item_end(indent_level);
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Beta,
            exit_matcher: &exit_matcher,
        }),
    ];
    let parser_context = context.with_additional_node(&contexts[0]);
    let parser_context = parser_context.with_additional_node(&contexts[1]);

    let maybe_contentless_item: Res<OrgSource<'_>, ()> = peek(parser_with_context!(
        detect_contentless_item_contents
    )(&parser_context))(remaining);
    match maybe_contentless_item {
        Ok((_rem, _ws)) => {
            let (remaining, _trailing_ws) = if context.should_consume_trailing_whitespace() {
                recognize(alt((recognize(many1(blank_line)), eof)))(remaining)?
            } else {
                recognize(alt((blank_line, eof)))(remaining)?
            };
            let source = get_consumed(input, remaining);
            return Ok((
                remaining,
                PlainListItem {
                    source: source.into(),
                    indentation: indent_level,
                    bullet: bull.into(),
                    checkbox: None,
                    tag: maybe_tag
                        .map(|(_ws, item_tag)| item_tag)
                        .unwrap_or(Vec::new()),
                    children: Vec::new(),
                },
            ));
        }
        Err(_) => {}
    };
    let (remaining, _ws) = item_tag_post_gap(&parser_context, remaining)?;

    let (mut remaining, (mut children, _exit_contents)) = many_till(
        include_input(parser_with_context!(element(true))(&parser_context)),
        parser_with_context!(exit_matcher_parser)(&parser_context),
    )(remaining)?;

    if !children.is_empty() && !context.should_consume_trailing_whitespace() {
        let final_item_context = ContextElement::ConsumeTrailingWhitespace(false);
        let final_item_context = parser_context.with_additional_node(&final_item_context);
        let (final_child_start, _original_final_child) = children
            .pop()
            .expect("if-statement already checked that children was non-empty.");
        let (remain, reparsed_final_element) = include_input(parser_with_context!(element(true))(
            &final_item_context,
        ))(final_child_start)?;
        remaining = remain;
        children.push(reparsed_final_element);
    }

    let (remaining, _trailing_ws) =
        maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;

    let source = get_consumed(input, remaining);
    return Ok((
        remaining,
        PlainListItem {
            source: source.into(),
            indentation: indent_level,
            bullet: bull.into(),
            checkbox: maybe_checkbox
                .map(|(_, (checkbox_type, source))| (checkbox_type, Into::<&str>::into(source))),
            tag: maybe_tag
                .map(|(_ws, item_tag)| item_tag)
                .unwrap_or(Vec::new()),
            children: children.into_iter().map(|(_start, item)| item).collect(),
        },
    ));
}

#[derive(Debug)]
enum BulletType {
    Ordered,
    Unordered,
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn bullet<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, (BulletType, OrgSource<'s>)> {
    alt((
        map(tag("*"), |bull| (BulletType::Unordered, bull)),
        map(tag("-"), |bull| (BulletType::Unordered, bull)),
        map(tag("+"), |bull| (BulletType::Unordered, bull)),
        map(
            recognize(tuple((
                parser_with_context!(counter)(context),
                alt((tag("."), tag(")"))),
            ))),
            |bull| (BulletType::Ordered, bull),
        ),
    ))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn counter<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    if context.get_global_settings().org_list_allow_alphabetical {
        alt((
            recognize(one_of(
                "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
            )),
            digit1,
        ))(input)
    } else {
        digit1(input)
    }
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn plain_list_end<'b, 'g, 'r, 's>(
    _context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    recognize(tuple((
        start_of_line,
        verify(many1(blank_line), |lines: &Vec<OrgSource<'_>>| {
            lines.len() >= 2
        }),
    )))(input)
}

const fn plain_list_item_end(indent_level: IndentationLevel) -> impl ContextMatcher {
    let line_indented_lte_matcher = line_indented_lte(indent_level);
    move |context, input: OrgSource<'_>| {
        _plain_list_item_end(context, input, &line_indented_lte_matcher)
    }
}

#[cfg_attr(
    feature = "tracing",
    tracing::instrument(ret, level = "debug", skip(line_indented_lte_matcher))
)]
fn _plain_list_item_end<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
    line_indented_lte_matcher: impl ContextMatcher,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    start_of_line(input)?;
    recognize(tuple((
        opt(blank_line),
        parser_with_context!(line_indented_lte_matcher)(context),
    )))(input)
}

const fn line_indented_lte(indent_level: IndentationLevel) -> impl ContextMatcher {
    move |context, input: OrgSource<'_>| _line_indented_lte(context, input, indent_level)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn _line_indented_lte<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
    indent_level: IndentationLevel,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    let matched = recognize(verify(
        tuple((
            parser_with_context!(indentation_level)(context),
            non_whitespace_character,
        )),
        // It is fine that we get the indent level using the number of bytes rather than the number of characters because nom's space0 only matches space and tab (0x20 and 0x09)
        |((indentation_level, _leading_whitespace), _anychar)| *indentation_level <= indent_level,
    ))(input)?;

    Ok(matched)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn item_tag<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, Vec<Object<'s>>> {
    let parser_context = ContextElement::ExitMatcherNode(ExitMatcherNode {
        class: ExitClass::Gamma,
        exit_matcher: &item_tag_end,
    });
    let parser_context = context.with_additional_node(&parser_context);
    let (remaining, (children, _exit_contents)) = verify(
        many_till(
            // TODO: Should this be using a different set like the minimal set?
            parser_with_context!(standard_set_object)(&parser_context),
            parser_with_context!(exit_matcher_parser)(&parser_context),
        ),
        |(children, _exit_contents)| !children.is_empty(),
    )(input)?;
    let (remaining, _) = item_tag_divider(remaining)?;
    Ok((remaining, children))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn item_tag_end<'b, 'g, 'r, 's>(
    _context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    alt((item_tag_divider, line_ending))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn item_tag_divider<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, OrgSource<'s>> {
    recognize(tuple((
        one_of(" \t"),
        tag("::"),
        peek(tuple((
            opt(tuple((
                peek(one_of(" \t")),
                many_till(anychar, peek(alt((item_tag_divider, line_ending, eof)))),
            ))),
            alt((line_ending, eof)),
        ))),
    )))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn item_tag_post_gap<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    verify(
        recognize(tuple((
            alt((blank_line, space0)),
            many_till(
                blank_line,
                alt((
                    peek(recognize(not(blank_line))),
                    peek(recognize(tuple((many0(blank_line), eof)))),
                    parser_with_context!(exit_matcher_parser)(context),
                )),
            ),
        ))),
        |gap| gap.len() > 0,
    )(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn item_checkbox<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, (CheckboxType, OrgSource<'s>)> {
    alt((
        map(
            recognize(tuple((tag("["), org_space, tag("]")))),
            |capture| (CheckboxType::Off, capture),
        ),
        map(tag("[-]"), |capture| (CheckboxType::Trans, capture)),
        map(tag("[X]"), |capture| (CheckboxType::On, capture)),
    ))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn detect_contentless_item_contents<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, ()> {
    let (remaining, _) = recognize(many_till(
        blank_line,
        parser_with_context!(exit_matcher_parser)(context),
    ))(input)?;
    Ok((remaining, ()))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::context::Context;
    use crate::context::GlobalSettings;
    use crate::context::List;
    use crate::types::Source;

    #[test]
    fn plain_list_item_empty() {
        let input = OrgSource::new("1.");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_item_matcher = parser_with_context!(plain_list_item)(&initial_context);
        let (remaining, result) = plain_list_item_matcher(input).unwrap();
        assert_eq!(Into::<&str>::into(remaining), "");
        assert_eq!(result.source, "1.");
    }

    #[test]
    fn plain_list_item_simple() {
        let input = OrgSource::new("1. foo");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_item_matcher = parser_with_context!(plain_list_item)(&initial_context);
        let (remaining, result) = plain_list_item_matcher(input).unwrap();
        assert_eq!(Into::<&str>::into(remaining), "");
        assert_eq!(result.source, "1. foo");
    }

    #[test]
    fn plain_list_empty() {
        let input = OrgSource::new("1.");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(plain_list)(&initial_context);
        let (remaining, result) = plain_list_matcher(input).unwrap();
        assert_eq!(Into::<&str>::into(remaining), "");
        assert_eq!(result.source, "1.");
    }

    #[test]
    fn plain_list_simple() {
        let input = OrgSource::new("1. foo");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(plain_list)(&initial_context);
        let (remaining, result) = plain_list_matcher(input).unwrap();
        assert_eq!(Into::<&str>::into(remaining), "");
        assert_eq!(result.source, "1. foo");
    }

    #[test]
    fn plain_list_cant_start_line_with_asterisk() {
        // Plain lists with an asterisk bullet must be indented or else they would be a headline
        let input = OrgSource::new("* foo");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(plain_list)(&initial_context);
        let result = plain_list_matcher(input);
        assert!(result.is_err());
    }

    #[test]
    fn indented_can_start_line_with_asterisk() {
        // Plain lists with an asterisk bullet must be indented or else they would be a headline
        let input = OrgSource::new(" * foo");
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(plain_list)(&initial_context);
        let result = plain_list_matcher(input);
        assert!(result.is_ok());
    }

    #[test]
    fn two_blank_lines_ends_list() {
        let input = OrgSource::new(
            r#"1. foo
2. bar
   baz
3. lorem


   ipsum
"#,
        );
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(element(true))(&initial_context);
        let (remaining, result) =
            plain_list_matcher(input).expect("Should parse the plain list successfully.");
        assert_eq!(Into::<&str>::into(remaining), "   ipsum\n");
        assert_eq!(
            result.get_source(),
            r#"1. foo
2. bar
   baz
3. lorem


"#
        );
    }

    #[test]
    fn two_blank_lines_ends_nested_list() {
        let input = OrgSource::new(
            r#"1. foo
   1. bar


baz"#,
        );
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(element(true))(&initial_context);
        let (remaining, result) =
            plain_list_matcher(input).expect("Should parse the plain list successfully.");
        assert_eq!(Into::<&str>::into(remaining), "baz");
        assert_eq!(
            result.get_source(),
            r#"1. foo
   1. bar


"#
        );
    }

    #[test]
    fn interior_trailing_whitespace() {
        let input = OrgSource::new(
            r#"1. foo

   bar

   1. baz

      lorem

   ipsum


dolar"#,
        );
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let plain_list_matcher = parser_with_context!(element(true))(&initial_context);
        let (remaining, result) =
            plain_list_matcher(input).expect("Should parse the plain list successfully.");
        assert_eq!(Into::<&str>::into(remaining), "dolar");
        assert_eq!(
            result.get_source(),
            r#"1. foo

   bar

   1. baz

      lorem

   ipsum


"#
        );
    }

    #[test]
    fn detect_line_break() {
        let input = OrgSource::new(
            r#"+
"#,
        );
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let result = detect_plain_list(&initial_context, input);
        assert!(result.is_ok());
    }

    #[test]
    fn detect_eof() {
        let input = OrgSource::new(r#"+"#);
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let result = detect_plain_list(&initial_context, input);
        assert!(result.is_ok());
    }

    #[test]
    fn detect_no_gap() {
        let input = OrgSource::new(r#"+foo"#);
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let result = detect_plain_list(&initial_context, input);
        // Since there is no whitespace after the '+' this is a paragraph, not a plain list.
        assert!(result.is_err());
    }

    #[test]
    fn detect_with_gap() {
        let input = OrgSource::new(r#"+ foo"#);
        let global_settings = GlobalSettings::default();
        let initial_context = ContextElement::document_context();
        let initial_context = Context::new(&global_settings, List::new(&initial_context));
        let result = detect_plain_list(&initial_context, input);
        assert!(result.is_ok());
    }
}