use failure::{Error,bail};
use pest::iterators::Pair;

use document_tree::{
	Element,HasChildren,ExtraAttributes,
	elements as e,
	element_categories as c,
	extra_attributes as a,
	attribute_types as at
};

use crate::{
	pest_rst::Rule,
	pair_ext_parse::PairExt,
};
use super::{whitespace_normalize_name, inline::convert_inlines};


#[derive(PartialEq)]
pub(super) enum TitleKind { Double(char), Single(char) }

pub(super) enum TitleOrSsubel {
	Title(e::Title, TitleKind),
	Ssubel(c::StructuralSubElement),
}


pub(super) fn convert_ssubel(pair: Pair<Rule>) -> Result<Option<TitleOrSsubel>, Error> {
	use self::TitleOrSsubel::*;
	Ok(Some(match pair.as_rule() {
		Rule::title => { let (t, k) = convert_title(pair)?; Title(t, k) },
		//TODO: subtitle, decoration, docinfo
		Rule::EOI   => return Ok(None),
		_           => Ssubel(convert_substructure(pair)?.into()),
	}))
}


fn convert_substructure(pair: Pair<Rule>) -> Result<c::SubStructure, Error> {
	Ok(match pair.as_rule() {
		// todo: Topic, Sidebar, Transition
		// no section here, as it’s constructed from titles
		_ => convert_body_elem(pair)?.into(),
	})
}


fn convert_body_elem(pair: Pair<Rule>) -> Result<c::BodyElement, Error> {
	Ok(match pair.as_rule() {
		Rule::paragraph        => convert_paragraph(pair)?.into(),
		Rule::target           => convert_target(pair)?.into(),
		Rule::substitution_def => convert_substitution_def(pair)?.into(),
		Rule::admonition_gen   => convert_admonition_gen(pair)?.into(),
		Rule::image            => convert_image::<e::Image>(pair)?.into(),
		Rule::bullet_list      => convert_bullet_list(pair)?.into(),
		Rule::code_directive   => convert_code_directive(pair)?.into(),
		Rule::raw_directive    => convert_raw_directive(pair)?.into(),
		Rule::block_comment    => convert_comment(pair)?.into(),
		rule => unimplemented!("unhandled rule {:?}", rule),
	})
}


fn convert_title(pair: Pair<Rule>) -> Result<(e::Title, TitleKind), Error> {
	let mut title: Option<String> = None;
	let mut title_inlines: Option<Vec<c::TextOrInlineElement>> = None;
	let mut adornment_char: Option<char> = None;
	// title_double or title_single. Extract kind before consuming
	let inner_pair = pair.into_inner().next().unwrap();
	let kind = inner_pair.as_rule();
	for p in inner_pair.into_inner() {
		match p.as_rule() {
			Rule::line => {
				title = Some(p.as_str().to_owned());
				title_inlines = Some(convert_inlines(p)?);
			},
			Rule::adornments => adornment_char = Some(p.as_str().chars().next().expect("Empty adornment?")),
			rule => unimplemented!("Unexpected rule in title: {:?}", rule),
		};
	}
	// now we encountered one line of text and one of adornments
	// TODO: emit error if the adornment line is too short (has to match title length)
	let mut elem = e::Title::with_children(title_inlines.expect("No text in title"));
	if let Some(title) = title {
		//TODO: slugify properly
		let slug =  title.to_lowercase().replace("\n", "").replace(" ", "-");
		elem.names_mut().push(at::NameToken(slug));
	}
	let title_kind = match kind {
		Rule::title_double => TitleKind::Double(adornment_char.unwrap()),
		Rule::title_single => TitleKind::Single(adornment_char.unwrap()),
		_ => unreachable!(),
	};
	Ok((elem, title_kind))
}


fn convert_paragraph(pair: Pair<Rule>) -> Result<e::Paragraph, Error> {
	Ok(e::Paragraph::with_children(convert_inlines(pair)?))
}


fn convert_target(pair: Pair<Rule>) -> Result<e::Target, Error> {
	let mut elem: e::Target = Default::default();
	elem.extra_mut().anonymous = false;
	for p in pair.into_inner() {
		match p.as_rule() {
			Rule::target_name_uq | Rule::target_name_qu => {
				elem.ids_mut().push(p.as_str().into());
				elem.names_mut().push(p.as_str().into());
			},
			// TODO: also handle non-urls
			Rule::link_target => elem.extra_mut().refuri = Some(p.parse()?),
			rule => panic!("Unexpected rule in target: {:?}", rule),
		}
	}
	Ok(elem)
}

fn convert_substitution_def(pair: Pair<Rule>) -> Result<e::SubstitutionDefinition, Error> {
	let mut pairs = pair.into_inner();
	let name = whitespace_normalize_name(pairs.next().unwrap().as_str());  // Rule::substitution_name
	let inner_pair = pairs.next().unwrap();
	let inner: Vec<c::TextOrInlineElement> = match inner_pair.as_rule() {
		Rule::replace => convert_replace(inner_pair)?,
		Rule::image   => vec![convert_image::<e::ImageInline>(inner_pair)?.into()],
		rule => panic!("Unknown substitution rule {:?}", rule),
	};
	let mut subst_def = e::SubstitutionDefinition::with_children(inner);
	subst_def.names_mut().push(at::NameToken(name));
	Ok(subst_def)
}

fn convert_replace(pair: Pair<Rule>) -> Result<Vec<c::TextOrInlineElement>, Error> {
	let mut pairs = pair.into_inner();
	let paragraph = pairs.next().unwrap();
	convert_inlines(paragraph)
}

fn convert_image<I>(pair: Pair<Rule>) -> Result<I, Error> where I: Element + ExtraAttributes<a::Image> {
	let mut pairs = pair.into_inner();
	let mut image = I::with_extra(a::Image::new(
		pairs.next().unwrap().as_str().trim().parse()?,  // line
	));
	for opt in pairs {
		let mut opt_iter = opt.into_inner();
		let opt_name = opt_iter.next().unwrap();
		let opt_val = opt_iter.next().unwrap();
		match opt_name.as_str() {
			"class"  => image.classes_mut().push(opt_val.as_str().to_owned()),
			"name"   => image.names_mut().push(opt_val.as_str().into()),
			"alt"    => image.extra_mut().alt    = Some(opt_val.as_str().to_owned()),
			"height" => image.extra_mut().height = Some(opt_val.parse()?),
			"width"  => image.extra_mut().width  = Some(opt_val.parse()?),
			"scale"  => image.extra_mut().scale  = Some(parse_scale(&opt_val)?),
			"align"  => image.extra_mut().align  = Some(opt_val.parse()?),
			"target" => image.extra_mut().target = Some(opt_val.parse()?),
			name => bail!("Unknown Image option {}", name),
		}
	}
	Ok(image)
}

fn parse_scale(pair: &Pair<Rule>) -> Result<u8, Error> {
	let input = if pair.as_str().chars().rev().next() == Some('%') { &pair.as_str()[..pair.as_str().len()-1] } else { pair.as_str() };
	use pest::error::{Error,ErrorVariant};
	Ok(input.parse().map_err(|e: std::num::ParseIntError| {
		let var: ErrorVariant<Rule> = ErrorVariant::CustomError { message: e.to_string() };
		Error::new_from_span(var, pair.as_span())
	})?)
}

fn convert_admonition_gen(pair: Pair<Rule>) -> Result<c::BodyElement, Error> {
	let mut iter = pair.into_inner();
	let typ = iter.next().unwrap().as_str();
	// TODO: in reality it contains body elements.
	let children: Vec<c::BodyElement> = iter.map(|p| e::Paragraph::with_children(vec![p.as_str().into()]).into()).collect();
	Ok(match typ {
		"attention" => e::Attention::with_children(children).into(),
		"hint"      =>      e::Hint::with_children(children).into(),
		"note"      =>      e::Note::with_children(children).into(),
		"caution"   =>   e::Caution::with_children(children).into(),
		"danger"    =>    e::Danger::with_children(children).into(),
		"error"     =>     e::Error::with_children(children).into(),
		"important" => e::Important::with_children(children).into(),
		"tip"       =>       e::Tip::with_children(children).into(),
		"warning"   =>   e::Warning::with_children(children).into(),
		typ         => panic!("Unknown admontion type {}!", typ),
	})
}

fn convert_bullet_list(pair: Pair<Rule>) -> Result<e::BulletList, Error> {
	Ok(e::BulletList::with_children(pair.into_inner().map(convert_bullet_item).collect::<Result<_, _>>()?))
}

fn convert_bullet_item(pair: Pair<Rule>) -> Result<e::ListItem, Error> {
	let mut iter = pair.into_inner();
	let mut children: Vec<c::BodyElement> = vec![
		convert_paragraph(iter.next().unwrap())?.into()
	];
	for p in iter {
		children.push(convert_body_elem(p)?);
	}
	Ok(e::ListItem::with_children(children))
}

fn convert_code_directive(pair: Pair<Rule>) -> Result<e::LiteralBlock, Error> {
	let mut iter = pair.into_inner();
	let (lang, code) = match (iter.next().unwrap(), iter.next()) {
		(lang, Some(code)) => (Some(lang), code),
		(code, None) => (None, code),
	};
	let children = code.into_inner().map(|l| match l.as_rule() {
		Rule::code_line => l.as_str(),
		Rule::code_line_blank => "\n",
		_ => unreachable!(),
	}.into()).collect();
	let mut code_block = e::LiteralBlock::with_children(children);
	if let Some(lang) = lang {
		code_block.classes_mut().push(lang.as_str().to_owned());
	};
	Ok(code_block)
}

fn convert_raw_directive(pair: Pair<Rule>) -> Result<e::Raw, Error> {
	let mut iter = pair.into_inner();
	let format = iter.next().unwrap();
    let block = iter.next().unwrap();
	let children = block.into_inner().map(|l| match l.as_rule() {
		Rule::raw_line => l.as_str(),
		Rule::raw_line_blank => "\n",
		_ => unreachable!(),
	}.into()).collect();
	let mut raw_block = e::Raw::with_children(children);
	raw_block.extra_mut().format.push(at::NameToken(format.as_str().to_owned()));
	Ok(raw_block)
}

fn convert_comment_block(pair: Pair<Rule>) -> String {
	let iter = pair.into_inner();
	let block = iter.skip(1).next().unwrap();
	let text = block.into_inner().map(|l| match l.as_rule() {
		Rule::comment_line_blank => "",
		Rule::comment_line => l.as_str(),
		_ => unreachable!(),
	}.into()).collect::<Vec<&str>>().join("\n");
	text
}

fn convert_comment(pair: Pair<Rule>) -> Result<e::Comment, Error> {
	let block = pair.into_inner().skip(1).next().unwrap();
	let children = block.into_inner().map(|l| match l.as_rule() {
		Rule::comment_title => String::from(l.as_str()),
		Rule::comment_block => convert_comment_block(l),
		_ => unreachable!(),
	}.into()).collect();
	Ok(e::Comment::with_children(children))
}