use std::borrow::Cow;

use nom::branch::alt;
use nom::bytes::complete::escaped;
use nom::bytes::complete::is_a;
use nom::bytes::complete::tag;
use nom::bytes::complete::take_till1;
use nom::bytes::complete::take_until;
use nom::character::complete::anychar;
use nom::combinator::consumed;
use nom::combinator::eof;
use nom::combinator::map;
use nom::combinator::map_parser;
use nom::combinator::opt;
use nom::combinator::peek;
use nom::combinator::recognize;
use nom::combinator::rest;
use nom::combinator::verify;
use nom::multi::many_till;
use nom::sequence::tuple;
use nom::InputTake;

use super::object_parser::regular_link_description_set_object;
use super::org_source::OrgSource;
use super::plain_link::protocol;
use super::util::exit_matcher_parser;
use super::util::get_consumed;
use super::util::maybe_consume_object_trailing_whitespace_if_not_exiting;
use crate::context::parser_with_context;
use crate::context::ContextElement;
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::types::LinkType;
use crate::types::Object;
use crate::types::RegularLink;

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
pub(crate) fn regular_link<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, RegularLink<'s>> {
    alt((
        parser_with_context!(regular_link_without_description)(context),
        parser_with_context!(regular_link_with_description)(context),
    ))(input)
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn regular_link_without_description<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, RegularLink<'s>> {
    let (remaining, _opening_bracket) = tag("[[")(input)?;
    let (remaining, path) = pathreg(context, remaining)?;
    let (remaining, _closing_bracket) = tag("]]")(remaining)?;
    let (remaining, _trailing_whitespace) =
        maybe_consume_object_trailing_whitespace_if_not_exiting(context, remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        RegularLink {
            source: source.into(),
            link_type: path.link_type,
            path: path.path,
            raw_link: path.raw_link,
            search_option: path.search_option,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn regular_link_with_description<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, RegularLink<'s>> {
    let (remaining, _opening_bracket) = tag("[[")(input)?;
    let (remaining, path) = pathreg(context, remaining)?;
    let (remaining, _closing_bracket) = tag("][")(remaining)?;
    let (remaining, _description) = description(context, remaining)?;
    let (remaining, _closing_bracket) = tag("]]")(remaining)?;
    let (remaining, _trailing_whitespace) =
        maybe_consume_object_trailing_whitespace_if_not_exiting(context, remaining)?;
    let source = get_consumed(input, remaining);
    Ok((
        remaining,
        RegularLink {
            source: source.into(),
            link_type: path.link_type,
            path: path.path,
            raw_link: path.raw_link,
            search_option: path.search_option,
        },
    ))
}

#[derive(Debug)]
struct PathReg<'s> {
    link_type: LinkType<'s>,
    path: Cow<'s, str>,
    raw_link: Cow<'s, str>,
    search_option: Option<Cow<'s, str>>,
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn pathreg<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, path) = map_parser(
        escaped(
            take_till1(|c| match c {
                '\\' | '[' | ']' => true,
                _ => false,
            }),
            '\\',
            anychar,
        ),
        parser_with_context!(parse_path_reg)(context),
    )(input)?;
    Ok((remaining, path))
}

fn parse_path_reg<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, PathReg<'s>> {
    if let Some(replaced_link) = apply_link_templates(context, input) {
        let replaced_input = Into::<OrgSource<'_>>::into(replaced_link.as_str());
        let (_remaining, link) = alt((
            file_path_reg,
            id_path_reg,
            custom_id_path_reg,
            code_ref_path_reg,
            parser_with_context!(protocol_path_reg)(context),
            fuzzy_path_reg,
        ))(replaced_input)
        .map_err(|_| {
            nom::Err::Error(CustomError::MyError(MyError(
                "No pathreg match after replacement.",
            )))
        })?;
        let remaining = input.take(input.len());
        let link_type = match link.link_type {
            LinkType::Protocol(protocol) => LinkType::Protocol(protocol.into_owned().into()),
            LinkType::File => LinkType::File,
            LinkType::Id => LinkType::Id,
            LinkType::CustomId => LinkType::CustomId,
            LinkType::CodeRef => LinkType::CodeRef,
            LinkType::Fuzzy => LinkType::Fuzzy,
        };
        Ok((
            remaining,
            PathReg {
                link_type,
                path: link.path.into_owned().into(),
                raw_link: link.raw_link.into_owned().into(),
                search_option: link.search_option.map(|s| s.into_owned().into()),
            },
        ))
    } else {
        alt((
            file_path_reg,
            id_path_reg,
            custom_id_path_reg,
            code_ref_path_reg,
            parser_with_context!(protocol_path_reg)(context),
            fuzzy_path_reg,
        ))(input)
    }
}

enum ParserState {
    Normal,
    Percent,
}

fn apply_link_templates<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Option<String> {
    let (remaining, key) = opt(map(
        tuple((
            recognize(take_until::<_, _, nom::error::Error<_>>(":")),
            is_a(":"),
        )),
        |(key, _)| key,
    ))(input)
    .expect("opt ensures this cannot error.");
    let key = match key {
        Some(key) => key,
        None => {
            return None;
        }
    };
    let replacement_template = match context.get_global_settings().link_templates.get(key.into()) {
        Some(template) => template,
        None => {
            return None;
        }
    };

    let inject_value = Into::<&str>::into(remaining);
    let mut ret = String::with_capacity(replacement_template.len() + inject_value.len());
    let mut state = ParserState::Normal;
    let mut injected_value = false;
    for c in replacement_template.chars() {
        state = match (&state, c) {
            (ParserState::Normal, '%') => ParserState::Percent,
            (ParserState::Normal, _) => {
                ret.push(c);
                ParserState::Normal
            }
            (ParserState::Percent, 's') => {
                ret.push_str(inject_value);
                injected_value = true;
                ParserState::Normal
            }
            (ParserState::Percent, _) => {
                panic!("Unhandled percent value: {}", c)
            }
        };
    }
    // Handle lingering state
    match state {
        ParserState::Percent => {
            ret.push('%');
        }
        _ => {}
    }
    if !injected_value {
        ret.push_str(inject_value);
    }
    Some(ret)
}

fn file_path_reg<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, (raw_link, (_, path, search_option))) = consumed(tuple((
        alt((tag("file:"), peek(tag(".")), peek(tag("/")))),
        recognize(many_till(anychar, alt((peek(tag("::")), eof)))),
        opt(map(tuple((tag("::"), rest)), |(_, search_option)| {
            search_option
        })),
    )))(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::File,
            path: path.into(),
            raw_link: raw_link.into(),
            search_option: search_option
                .map(Into::<&str>::into)
                .map(Into::<Cow<str>>::into),
        },
    ))
}

fn id_path_reg<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, (raw_link, (_, path))) = consumed(tuple((tag("id:"), rest)))(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::Id,
            path: path.into(),
            raw_link: raw_link.into(),
            search_option: None,
        },
    ))
}

fn custom_id_path_reg<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, (raw_link, (_, path))) = consumed(tuple((tag("#"), rest)))(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::CustomId,
            path: path.into(),
            raw_link: raw_link.into(),
            search_option: None,
        },
    ))
}

fn code_ref_path_reg<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, (raw_link, (_, path, _))) = consumed(tuple((
        tag("("),
        recognize(many_till(anychar, peek(tuple((tag(")"), eof))))),
        tag(")"),
    )))(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::CodeRef,
            path: path.into(),
            raw_link: raw_link.into(),
            search_option: None,
        },
    ))
}

fn protocol_path_reg<'b, 'g, 'r, 's>(
    context: RefContext<'b, 'g, 'r, 's>,
    input: OrgSource<'s>,
) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, (raw_link, (protocol, _, path))) = consumed(tuple((
        parser_with_context!(protocol)(context),
        tag(":"),
        rest,
    )))(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::Protocol(protocol.into()),
            path: path.into(),
            raw_link: raw_link.into(),
            search_option: None,
        },
    ))
}

fn fuzzy_path_reg<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, PathReg<'s>> {
    let (remaining, body) = rest(input)?;
    Ok((
        remaining,
        PathReg {
            link_type: LinkType::Fuzzy,
            path: body.into(),
            raw_link: body.into(),
            search_option: None,
        },
    ))
}

#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
fn description<'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::Beta,
        exit_matcher: &description_end,
    });
    let parser_context = context.with_additional_node(&parser_context);
    let (remaining, (children, _exit_contents)) = verify(
        many_till(
            parser_with_context!(regular_link_description_set_object)(&parser_context),
            parser_with_context!(exit_matcher_parser)(&parser_context),
        ),
        |(children, _exit_contents)| !children.is_empty(),
    )(input)?;

    Ok((remaining, children))
}

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