use nom::branch::alt;
use nom::bytes::complete::is_not;
use nom::bytes::complete::tag;
use nom::bytes::complete::tag_no_case;
use nom::character::complete::anychar;
use nom::character::complete::line_ending;
use nom::character::complete::space0;
use nom::character::complete::space1;
use nom::combinator::consumed;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::opt;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::verify;
use nom::multi::many_till;
use nom::multi::separated_list0;
use nom::multi::separated_list1;
use nom::sequence::tuple;

use super::org_source::OrgSource;
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::Res;
use crate::parser::object_parser::standard_set_object;
use crate::parser::util::blank_line;
use crate::parser::util::exit_matcher_parser;
use crate::parser::util::get_consumed;
use crate::parser::util::start_of_line;
use crate::parser::util::text_until_exit;
use crate::types::CharOffsetInLine;
use crate::types::CommentBlock;
use crate::types::ExampleBlock;
use crate::types::ExportBlock;
use crate::types::LineNumber;
use crate::types::Object;
use crate::types::PlainText;
use crate::types::RetainLabels;
use crate::types::SrcBlock;
use crate::types::SwitchNumberLines;
use crate::types::VerseBlock;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn verse_block<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, VerseBlock<'s>> {
    let (remaining, name) = lesser_block_begin("verse")(context, input)?;
    let (remaining, parameters) = opt(tuple((space1, data)))(remaining)?;
    let (remaining, _nl) = recognize(tuple((space0, line_ending)))(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("verse");
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::Context("lesser block"),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &lesser_block_end_specialized,
        }),
    ];
    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]);
    let parameters = match parameters {
        Some((_ws, parameters)) => Some(parameters),
        None => None,
    };

    let object_matcher = parser_with_context!(standard_set_object)(&parser_context);
    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
    // Check for a completely empty block
    let (remaining, children) = match consumed(many_till(blank_line, exit_matcher))(remaining) {
        Ok((remaining, (whitespace, (_children, _exit_contents)))) => (
            remaining,
            vec![Object::PlainText(PlainText {
                source: whitespace.into(),
            })],
        ),
        Err(_) => {
            let (remaining, (children, _exit_contents)) =
                many_till(object_matcher, exit_matcher)(remaining)?;
            (remaining, children)
        }
    };
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        VerseBlock {
            source: source.into(),
            name: name.into(),
            data: parameters.map(|parameters| Into::<&str>::into(parameters)),
            children,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn comment_block<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, CommentBlock<'s>> {
    let (remaining, _name) = lesser_block_begin("comment")(context, input)?;
    let (remaining, _parameters) = opt(tuple((space1, data)))(remaining)?;
    let (remaining, _nl) = recognize(tuple((space0, line_ending)))(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("comment");
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::Context("lesser block"),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &lesser_block_end_specialized,
        }),
    ];
    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]);

    let (remaining, contents) = parser_with_context!(text_until_exit)(&parser_context)(remaining)?;
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        CommentBlock {
            source: source.into(),
            contents: contents.into(),
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn example_block<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, ExampleBlock<'s>> {
    let (remaining, _name) = lesser_block_begin("example")(context, input)?;
    let (remaining, parameters) = opt(tuple((space1, example_switches)))(remaining)?;
    let (remaining, _nl) = recognize(tuple((space0, line_ending)))(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("example");
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::Context("lesser block"),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &lesser_block_end_specialized,
        }),
    ];
    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]);
    let parameters = parameters.map(|(_, parameters)| parameters);

    let (remaining, contents) = content(&parser_context, remaining)?;
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let source = get_consumed(input, remaining);
    let (switches, number_lines, retain_labels, use_labels, label_format) = {
        if let Some(parameters) = parameters {
            (
                if parameters.source.len() == 0 {
                    None
                } else {
                    Some(parameters.source)
                },
                parameters.number_lines,
                parameters.retain_labels,
                parameters.use_labels,
                parameters.label_format,
            )
        } else {
            (None, None, RetainLabels::Yes, true, None)
        }
    };
    Ok((
        remaining,
        ExampleBlock {
            source: source.into(),
            switches,
            number_lines,
            retain_labels,
            use_labels,
            label_format,
            contents,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn export_block<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, ExportBlock<'s>> {
    let (remaining, name) = lesser_block_begin("export")(context, input)?;
    // https://orgmode.org/worg/org-syntax.html#Blocks claims that export blocks must have a single word for data but testing shows no data and multi-word data still parses as an export block.
    let (remaining, parameters) = opt(tuple((space1, data)))(remaining)?;
    let (remaining, _nl) = recognize(tuple((space0, line_ending)))(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("export");
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::Context("lesser block"),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &lesser_block_end_specialized,
        }),
    ];
    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]);
    let parameters = match parameters {
        Some((_ws, parameters)) => Some(parameters),
        None => None,
    };

    let (remaining, contents) = parser_with_context!(text_until_exit)(&parser_context)(remaining)?;
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        ExportBlock {
            source: source.into(),
            name: name.into(),
            data: parameters.map(|parameters| Into::<&str>::into(parameters)),
            contents: contents.into(),
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn src_block<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, SrcBlock<'s>> {
    let (remaining, _name) = lesser_block_begin("src")(context, input)?;
    // https://orgmode.org/worg/org-syntax.html#Blocks claims that data is mandatory and must follow the LANGUAGE SWITCHES ARGUMENTS pattern but testing has shown that no data and incorrect data here will still parse to a src block.
    let (remaining, parameters) = opt(tuple((space1, src_switches)))(remaining)?;
    let (remaining, _nl) = recognize(tuple((space0, line_ending)))(remaining)?;
    let lesser_block_end_specialized = lesser_block_end("src");
    let contexts = [
        ContextElement::ConsumeTrailingWhitespace(true),
        ContextElement::Context("lesser block"),
        ContextElement::ExitMatcherNode(ExitMatcherNode {
            class: ExitClass::Alpha,
            exit_matcher: &lesser_block_end_specialized,
        }),
    ];
    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]);
    let parameters = match parameters {
        Some((_ws, parameters)) => Some(parameters),
        None => None,
    };

    let (remaining, contents) = content(&parser_context, remaining)?;
    let (remaining, _end) = lesser_block_end_specialized(&parser_context, remaining)?;

    let source = get_consumed(input, remaining);
    let (switches, language, number_lines, retain_labels, use_labels, label_format) = {
        if let Some(parameters) = parameters {
            (
                if parameters.source.len() == 0 {
                    None
                } else {
                    Some(parameters.source)
                },
                parameters.language,
                parameters.number_lines,
                parameters.retain_labels,
                parameters.use_labels,
                parameters.label_format,
            )
        } else {
            (None, None, None, RetainLabels::Yes, true, None)
        }
    };
    Ok((
        remaining,
        SrcBlock {
            source: source.into(),
            switches,
            language,
            number_lines,
            retain_labels,
            use_labels,
            label_format,
            contents,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn name<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, OrgSource<'s>> {
    is_not(" \t\r\n")(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn data<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, OrgSource<'s>> {
    is_not("\r\n")(input)
}

fn lesser_block_end<'c>(current_name: &'c str) -> impl ContextMatcher + 'c {
    // Since the lesser block names are statically defined in code, we can simply assert that the name is lowercase instead of causing an allocation by converting to lowercase.
    debug_assert!(current_name == current_name.to_lowercase());
    move |context, input: OrgSource<'_>| _lesser_block_end(context, input, current_name)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn _lesser_block_end<'b, 'g, 'r, 's, 'c>(
    _context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
    current_name_lower: &'c str,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    start_of_line(input)?;
    let (remaining, _leading_whitespace) = space0(input)?;
    let (remaining, (_begin, _name, _ws, _ending)) = tuple((
        tag_no_case("#+end_"),
        tag_no_case(current_name_lower),
        space0,
        alt((eof, line_ending)),
    ))(remaining)?;
    let source = get_consumed(input, remaining);
    Ok((remaining, source))
}

/// Parser for the beginning of a lesser block
///
/// current_name MUST be lowercase. We do not do the conversion ourselves because it is not allowed in a const fn.
const fn lesser_block_begin<'c>(current_name: &'c str) -> impl ContextMatcher + 'c {
    // TODO: Since this is a const fn, is there ANY way to "generate" functions at compile time?
    move |context, input: OrgSource<'_>| _lesser_block_begin(context, input, current_name)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn _lesser_block_begin<'b, 'g, 'r, 's, 'c>(
    _context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
    current_name_lower: &'c str,
) -> Res<OrgSource<'s>, OrgSource<'s>> {
    start_of_line(input)?;
    let (remaining, _leading_whitespace) = space0(input)?;
    let (remaining, (_begin, name)) = tuple((
        tag_no_case("#+begin_"),
        verify(name, |name: &OrgSource<'_>| {
            Into::<&str>::into(name).to_lowercase().as_str() == current_name_lower
        }),
    ))(remaining)?;
    Ok((remaining, name))
}

#[derive(Debug)]
struct ExampleSrcSwitches<'s> {
    source: &'s str,
    language: Option<&'s str>,
    number_lines: Option<SwitchNumberLines>,
    retain_labels: RetainLabels,
    use_labels: bool,
    label_format: Option<&'s str>,
}

#[derive(Debug)]
enum SwitchState {
    Normal,
    NewLineNumber,
    ContinuedLineNumber,
    LabelFormat,
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn src_switches<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSrcSwitches<'s>> {
    example_src_switches(true)(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn example_switches<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSrcSwitches<'s>> {
    let (remaining, switches) = example_src_switches(false)(input)?;
    debug_assert!(switches.language.is_none());
    Ok((remaining, switches))
}

fn example_src_switches(
    grab_language: bool,
) -> impl for<'s> Fn(OrgSource<'s>) -> Res<OrgSource<'s>, ExampleSrcSwitches<'s>> {
    move |input| _example_src_switches(input, grab_language)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn _example_src_switches<'s>(
    input: OrgSource<'s>,
    grab_language: bool,
) -> Res<OrgSource<'s>, ExampleSrcSwitches<'s>> {
    let mut number_lines = None;
    let mut retain_labels = RetainLabels::Yes;
    let mut use_labels = true;
    let mut label_format = None;
    let mut saw_r = false;
    let mut language = None;

    let remaining = if grab_language {
        let (remain, first_word) = opt(map(tuple((switch_word, space0)), |(word, _)| word))(input)?;
        language = first_word.map(Into::<&str>::into);
        remain
    } else {
        input
    };

    let (remaining, (source, (words, _))) = if language.is_none() {
        consumed(tuple((separated_list1(space1, switch_word), space0)))(remaining)?
    } else {
        consumed(tuple((separated_list0(space1, switch_word), space0)))(remaining)?
    };

    let mut state = SwitchState::Normal;
    for word in words {
        let normalized_word = Into::<&str>::into(word);
        loop {
            match (&state, normalized_word) {
                (SwitchState::Normal, "-n") => {
                    state = SwitchState::NewLineNumber;
                }
                (SwitchState::Normal, "+n") => {
                    state = SwitchState::ContinuedLineNumber;
                }
                (SwitchState::Normal, "-r") => {
                    saw_r = true;
                    use_labels = false;
                    match retain_labels {
                        RetainLabels::Yes => {
                            retain_labels = RetainLabels::No;
                        }
                        _ => {}
                    }
                }
                (SwitchState::Normal, "-l") => {
                    state = SwitchState::LabelFormat;
                }
                (SwitchState::Normal, "-k") => {
                    use_labels = false;
                    let text_until_flag = input.get_until(word);
                    let character_offset = Into::<&str>::into(text_until_flag).chars().count();
                    let character_offset = CharOffsetInLine::try_from(character_offset)
                        .expect("Character offset should fit in CharOffsetInLine");
                    retain_labels = RetainLabels::Keep(character_offset);
                }
                (SwitchState::NewLineNumber, _) => {
                    let val = normalized_word.parse::<LineNumber>();
                    if let Ok(val) = val {
                        if val < 0 {
                            number_lines = Some(SwitchNumberLines::New(0));
                        } else {
                            // Note that this can result in a negative 1 if the val is originally 0.
                            number_lines = Some(SwitchNumberLines::New(val - 1));
                        }
                        state = SwitchState::Normal;
                    } else {
                        number_lines = Some(SwitchNumberLines::New(0));
                        state = SwitchState::Normal;
                        continue; // Re-processes the word
                    }
                }
                (SwitchState::ContinuedLineNumber, _) => {
                    let val = normalized_word.parse::<LineNumber>();
                    if let Ok(val) = val {
                        if val < 0 {
                            number_lines = Some(SwitchNumberLines::Continued(0));
                        } else {
                            // Note that this can result in a negative 1 if the val is originally 0.
                            number_lines = Some(SwitchNumberLines::Continued(val - 1));
                        }
                        state = SwitchState::Normal;
                    } else {
                        number_lines = Some(SwitchNumberLines::Continued(0));
                        state = SwitchState::Normal;
                        continue; // Re-processes the word
                    }
                }
                (SwitchState::LabelFormat, _) => {
                    label_format = Some(normalized_word);
                    state = SwitchState::Normal;
                }
                (SwitchState::Normal, _) => {}
            };
            break;
        }
    }

    let retain_labels = match retain_labels {
        RetainLabels::Keep(_) if !saw_r => RetainLabels::Yes,
        _ => retain_labels,
    };

    Ok((
        remaining,
        ExampleSrcSwitches {
            source: Into::<&str>::into(source),
            language,
            number_lines,
            retain_labels,
            use_labels,
            label_format,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn switch_word<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, OrgSource<'s>> {
    alt((
        map(
            tuple((tag(r#"""#), is_not("\"\r\n"), tag(r#"""#))),
            |(_, contents, _)| contents,
        ),
        is_not(" \t\r\n"),
    ))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn content<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, String> {
    let mut ret = String::new();
    let mut remaining = input;
    let exit_matcher_parser = parser_with_context!(exit_matcher_parser)(context);
    loop {
        if exit_matcher_parser(remaining).is_ok() {
            break;
        }

        let (remain, (pre_escape_whitespace, line)) = content_line(remaining)?;
        pre_escape_whitespace.map(|val| ret.push_str(Into::<&str>::into(val)));
        ret.push_str(line.into());
        remaining = remain;
    }

    Ok((remaining, ret))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn content_line<'s>(
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, (Option<OrgSource<'s>>, OrgSource<'s>)> {
    let (remaining, pre_escape_whitespace) = opt(map(
        tuple((
            recognize(tuple((
                space0,
                many_till(
                    tag(","),
                    peek(tuple((tag(","), alt((tag("#+"), tag("*")))))),
                ),
            ))),
            tag(","),
        )),
        |(pre_comma, _)| pre_comma,
    ))(input)?;
    let (remaining, line_post_escape) = recognize(many_till(anychar, line_ending))(remaining)?;
    Ok((remaining, (pre_escape_whitespace, line_post_escape)))
}