use std::iter::once;
use std::marker::PhantomData;

use indextree::{Arena, NodeId};
use jetscii::{bytes, BytesConst};
use memchr::{memchr, memchr_iter};
use nom::bytes::complete::take_while1;

use crate::config::ParseConfig;
use crate::elements::{
    block::RawBlock, emphasis::Emphasis, keyword::RawKeyword, radio_target::parse_radio_target,
    Clock, Comment, Cookie, Drawer, DynBlock, Element, FixedWidth, FnDef, FnRef, InlineCall,
    InlineSrc, Link, List, ListItem, Macros, Rule, Snippet, Table, TableCell, TableRow, Target,
    Timestamp, Title,
};
use crate::parse::combinators::lines_while;

pub trait ElementArena<'a> {
    fn append<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>;
    fn insert_before_last_child<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>;
    fn set<T>(&mut self, node: NodeId, element: T)
    where
        T: Into<Element<'a>>;
}

pub type BorrowedArena<'a> = Arena<Element<'a>>;

impl<'a> ElementArena<'a> for BorrowedArena<'a> {
    fn append<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>,
    {
        let node = self.new_node(element.into());
        parent.append(node, self);
        node
    }

    fn insert_before_last_child<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>,
    {
        if let Some(child) = self[parent].last_child() {
            let node = self.new_node(element.into());
            child.insert_before(node, self);
            node
        } else {
            self.append(element, parent)
        }
    }

    fn set<T>(&mut self, node: NodeId, element: T)
    where
        T: Into<Element<'a>>,
    {
        *self[node].get_mut() = element.into();
    }
}

pub struct OwnedArena<'a, 'b, 'c> {
    arena: &'b mut Arena<Element<'c>>,
    phantom: PhantomData<&'a ()>,
}

impl<'a, 'b, 'c> OwnedArena<'a, 'b, 'c> {
    pub fn new(arena: &'b mut Arena<Element<'c>>) -> OwnedArena<'a, 'b, 'c> {
        OwnedArena {
            arena,
            phantom: PhantomData,
        }
    }
}

impl<'a> ElementArena<'a> for OwnedArena<'a, '_, '_> {
    fn append<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>,
    {
        self.arena.append(element.into().into_owned(), parent)
    }

    fn insert_before_last_child<T>(&mut self, element: T, parent: NodeId) -> NodeId
    where
        T: Into<Element<'a>>,
    {
        self.arena
            .insert_before_last_child(element.into().into_owned(), parent)
    }

    fn set<T>(&mut self, node: NodeId, element: T)
    where
        T: Into<Element<'a>>,
    {
        self.arena.set(node, element.into().into_owned());
    }
}

#[derive(Debug)]
pub enum Container<'a> {
    // Block, List Item
    Block { content: &'a str, node: NodeId },
    // Paragraph, Inline Markup
    Inline { content: &'a str, node: NodeId },
    // Headline
    Headline { content: &'a str, node: NodeId },
    // Document
    Document { content: &'a str, node: NodeId },
}

pub fn parse_container<'a, T: ElementArena<'a>>(
    arena: &mut T,
    container: Container<'a>,
    config: &ParseConfig,
) {
    let containers = &mut vec![container];

    while let Some(container) = containers.pop() {
        match container {
            Container::Document { content, node } => {
                parse_section_and_headlines(arena, content, node, containers);
            }
            Container::Headline { content, node } => {
                parse_headline_content(arena, content, node, containers, config);
            }
            Container::Block { content, node } => {
                parse_blocks(arena, content, node, containers);
            }
            Container::Inline { content, node } => {
                parse_inlines(arena, content, node, containers);
            }
        }
    }
}

pub fn parse_headline_content<'a, T: ElementArena<'a>>(
    arena: &mut T,
    content: &'a str,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
    config: &ParseConfig,
) {
    let (tail, (title, content)) = Title::parse(content, config).unwrap();
    let node = arena.append(title, parent);
    containers.push(Container::Inline { content, node });
    parse_section_and_headlines(arena, tail, parent, containers);
}

pub fn parse_section_and_headlines<'a, T: ElementArena<'a>>(
    arena: &mut T,
    content: &'a str,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
) {
    let content = blank_lines_count(content).0;

    if content.is_empty() {
        return;
    }

    let mut last_end = 0;
    for i in memchr_iter(b'\n', content.as_bytes()).chain(once(content.len())) {
        if let Some((mut tail, (headline_content, level))) = parse_headline(&content[last_end..]) {
            if last_end != 0 {
                let node = arena.append(Element::Section, parent);
                let content = &content[0..last_end];
                containers.push(Container::Block { content, node });
            }

            let node = arena.append(Element::Headline { level }, parent);
            containers.push(Container::Headline {
                content: headline_content,
                node,
            });

            while let Some((new_tail, (content, level))) = parse_headline(tail) {
                debug_assert_ne!(tail, new_tail);
                let node = arena.append(Element::Headline { level }, parent);
                containers.push(Container::Headline { content, node });
                tail = new_tail;
            }
            return;
        }
        last_end = i + 1;
    }

    let node = arena.append(Element::Section, parent);
    containers.push(Container::Block { content, node });
}

pub fn parse_blocks<'a, T: ElementArena<'a>>(
    arena: &mut T,
    content: &'a str,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
) {
    let mut tail = blank_lines_count(content).0;

    if let Some(new_tail) = parse_block(content, arena, parent, containers) {
        tail = blank_lines_count(new_tail).0;
    }

    let mut text = tail;
    let mut pos = 0;

    while !tail.is_empty() {
        let i = memchr(b'\n', tail.as_bytes())
            .map(|i| i + 1)
            .unwrap_or_else(|| tail.len());
        if tail.as_bytes()[0..i].iter().all(u8::is_ascii_whitespace) {
            let (tail_, blank) = blank_lines_count(&tail[i..]);
            debug_assert_ne!(tail, tail_);
            tail = tail_;

            let node = arena.append(
                Element::Paragraph {
                    // including the current line (&tail[0..i])
                    post_blank: blank + 1,
                },
                parent,
            );

            containers.push(Container::Inline {
                content: &text[0..pos].trim_end(),
                node,
            });

            pos = 0;
            text = tail;
        } else if let Some(new_tail) = parse_block(tail, arena, parent, containers) {
            if pos != 0 {
                let node =
                    arena.insert_before_last_child(Element::Paragraph { post_blank: 0 }, parent);

                containers.push(Container::Inline {
                    content: &text[0..pos].trim_end(),
                    node,
                });

                pos = 0;
            }
            debug_assert_ne!(tail, blank_lines_count(new_tail).0);
            tail = blank_lines_count(new_tail).0;
            text = tail;
        } else {
            debug_assert_ne!(tail, &tail[i..]);
            tail = &tail[i..];
            pos += i;
        }
    }

    if !text.is_empty() {
        let node = arena.append(Element::Paragraph { post_blank: 0 }, parent);

        containers.push(Container::Inline {
            content: &text[0..pos].trim_end(),
            node,
        });
    }
}

pub fn parse_block<'a, T: ElementArena<'a>>(
    contents: &'a str,
    arena: &mut T,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
) -> Option<&'a str> {
    match contents
        .as_bytes()
        .iter()
        .find(|c| !c.is_ascii_whitespace())?
    {
        b'[' => {
            let (tail, (fn_def, content)) = FnDef::parse(contents)?;
            let node = arena.append(fn_def, parent);
            containers.push(Container::Block { content, node });
            Some(tail)
        }
        b'0'..=b'9' | b'*' => {
            let tail = parse_list(arena, contents, parent, containers)?;
            Some(tail)
        }
        b'C' => {
            let (tail, clock) = Clock::parse(contents)?;
            arena.append(clock, parent);
            Some(tail)
        }
        b'\'' => {
            // TODO: LaTeX environment
            None
        }
        b'-' => {
            if let Some((tail, rule)) = Rule::parse(contents) {
                arena.append(rule, parent);
                Some(tail)
            } else {
                let tail = parse_list(arena, contents, parent, containers)?;
                Some(tail)
            }
        }
        b':' => {
            if let Some((tail, (drawer, content))) = Drawer::parse(contents) {
                let node = arena.append(drawer, parent);
                containers.push(Container::Block { content, node });
                Some(tail)
            } else {
                let (tail, fixed_width) = FixedWidth::parse(contents)?;
                arena.append(fixed_width, parent);
                Some(tail)
            }
        }
        b'|' => {
            let tail = parse_org_table(arena, contents, containers, parent);
            Some(tail)
        }
        b'+' => {
            if let Some((tail, table)) = Table::parse_table_el(contents) {
                arena.append(table, parent);
                Some(tail)
            } else {
                let tail = parse_list(arena, contents, parent, containers)?;
                Some(tail)
            }
        }
        b'#' => {
            if let Some((tail, block)) = RawBlock::parse(contents) {
                let (element, content) = block.into_element();
                // avoid use after free
                let is_block_container = match element {
                    Element::CenterBlock(_)
                    | Element::QuoteBlock(_)
                    | Element::VerseBlock(_)
                    | Element::SpecialBlock(_) => true,
                    _ => false,
                };
                let node = arena.append(element, parent);
                if is_block_container {
                    containers.push(Container::Block { content, node });
                }
                Some(tail)
            } else if let Some((tail, (dyn_block, content))) = DynBlock::parse(contents) {
                let node = arena.append(dyn_block, parent);
                containers.push(Container::Block { content, node });
                Some(tail)
            } else if let Some((tail, keyword)) = RawKeyword::parse(contents) {
                arena.append(keyword.into_element(), parent);
                Some(tail)
            } else {
                let (tail, comment) = Comment::parse(contents)?;
                arena.append(comment, parent);
                Some(tail)
            }
        }
        _ => None,
    }
}

struct InlinePositions<'a> {
    bytes: &'a [u8],
    pos: usize,
    next: Option<usize>,
}

impl InlinePositions<'_> {
    fn new(bytes: &[u8]) -> InlinePositions {
        InlinePositions {
            bytes,
            pos: 0,
            next: Some(0),
        }
    }
}

impl Iterator for InlinePositions<'_> {
    type Item = usize;

    fn next(&mut self) -> Option<Self::Item> {
        lazy_static::lazy_static! {
            static ref PRE_BYTES: BytesConst =
                bytes!(b'@', b'<', b'[', b' ', b'(', b'{', b'\'', b'"', b'\n');
        }

        self.next.take().or_else(|| {
            PRE_BYTES.find(&self.bytes[self.pos..]).map(|i| {
                self.pos += i + 1;

                match self.bytes[self.pos - 1] {
                    b'{' => {
                        self.next = Some(self.pos);
                        self.pos - 1
                    }
                    b' ' | b'(' | b'\'' | b'"' | b'\n' => self.pos,
                    _ => self.pos - 1,
                }
            })
        })
    }
}

pub fn parse_inlines<'a, T: ElementArena<'a>>(
    arena: &mut T,
    content: &'a str,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
) {
    let mut tail = content;

    if let Some(tail_) = parse_inline(tail, arena, containers, parent) {
        tail = tail_;
    }

    while let Some((tail_, i)) = InlinePositions::new(tail.as_bytes())
        .filter_map(|i| parse_inline(&tail[i..], arena, containers, parent).map(|tail| (tail, i)))
        .next()
    {
        if i != 0 {
            arena.insert_before_last_child(
                Element::Text {
                    value: tail[0..i].into(),
                },
                parent,
            );
        }
        tail = tail_;
    }

    if !tail.is_empty() {
        arena.append(Element::Text { value: tail.into() }, parent);
    }
}

pub fn parse_inline<'a, T: ElementArena<'a>>(
    contents: &'a str,
    arena: &mut T,
    containers: &mut Vec<Container<'a>>,
    parent: NodeId,
) -> Option<&'a str> {
    if contents.len() < 3 {
        return None;
    }

    let byte = contents.as_bytes()[0];

    match byte {
        b'@' => {
            let (tail, snippet) = Snippet::parse(contents)?;
            arena.append(snippet, parent);
            Some(tail)
        }
        b'{' => {
            let (tail, macros) = Macros::parse(contents)?;
            arena.append(macros, parent);
            Some(tail)
        }
        b'<' => {
            if let Some((tail, _content)) = parse_radio_target(contents) {
                arena.append(Element::RadioTarget, parent);
                Some(tail)
            } else if let Some((tail, target)) = Target::parse(contents) {
                arena.append(target, parent);
                Some(tail)
            } else if let Some((tail, timestamp)) = Timestamp::parse_active(contents) {
                arena.append(timestamp, parent);
                Some(tail)
            } else {
                let (tail, timestamp) = Timestamp::parse_diary(contents)?;
                arena.append(timestamp, parent);
                Some(tail)
            }
        }
        b'[' => {
            if let Some((tail, fn_ref)) = FnRef::parse(contents) {
                arena.append(fn_ref, parent);
                Some(tail)
            } else if let Some((tail, link)) = Link::parse(contents) {
                arena.append(link, parent);
                Some(tail)
            } else if let Some((tail, cookie)) = Cookie::parse(contents) {
                arena.append(cookie, parent);
                Some(tail)
            } else {
                let (tail, timestamp) = Timestamp::parse_inactive(contents)?;
                arena.append(timestamp, parent);
                Some(tail)
            }
        }
        b'*' | b'+' | b'/' | b'_' | b'=' | b'~' => {
            let (tail, emphasis) = Emphasis::parse(contents, byte)?;
            let (element, content) = emphasis.into_element();
            let is_inline_container = match element {
                Element::Bold | Element::Strike | Element::Italic | Element::Underline => true,
                _ => false,
            };
            let node = arena.append(element, parent);
            if is_inline_container {
                containers.push(Container::Inline { content, node });
            }
            Some(tail)
        }
        b's' => {
            let (tail, inline_src) = InlineSrc::parse(contents)?;
            arena.append(inline_src, parent);
            Some(tail)
        }
        b'c' => {
            let (tail, inline_call) = InlineCall::parse(contents)?;
            arena.append(inline_call, parent);
            Some(tail)
        }
        _ => None,
    }
}

pub fn parse_list<'a, T: ElementArena<'a>>(
    arena: &mut T,
    contents: &'a str,
    parent: NodeId,
    containers: &mut Vec<Container<'a>>,
) -> Option<&'a str> {
    let (mut tail, (first_item, content)) = ListItem::parse(contents)?;
    let first_item_indent = first_item.indent;
    let first_item_ordered = first_item.ordered;

    let parent = arena.append(Element::Document { pre_blank: 0 }, parent); // placeholder

    let node = arena.append(first_item, parent);
    containers.push(Container::Block { content, node });

    while let Some((tail_, (item, content))) = ListItem::parse(tail) {
        if item.indent == first_item_indent {
            let node = arena.append(item, parent);
            containers.push(Container::Block { content, node });
            debug_assert_ne!(tail, tail_);
            tail = tail_;
        } else {
            break;
        }
    }

    let (tail, post_blank) = blank_lines_count(tail);

    arena.set(
        parent,
        List {
            indent: first_item_indent,
            ordered: first_item_ordered,
            post_blank,
        },
    );

    Some(tail)
}

pub fn parse_org_table<'a, T: ElementArena<'a>>(
    arena: &mut T,
    contents: &'a str,
    containers: &mut Vec<Container<'a>>,
    parent: NodeId,
) -> &'a str {
    let (tail, contents) =
        lines_while::<_, ()>(|line| line.trim_start().starts_with('|'))(contents)
            .unwrap_or((contents, ""));
    let (tail, post_blank) = blank_lines_count(tail);

    let mut iter = contents.trim_end().lines().peekable();

    let mut lines = vec![];

    let mut has_header = false;

    // TODO: merge contiguous rules

    if let Some(line) = iter.next() {
        let line = line.trim_start();
        if !line.starts_with("|-") {
            lines.push(line);
        }
    }

    while let Some(line) = iter.next() {
        let line = line.trim_start();
        if iter.peek().is_none() && line.starts_with("|-") {
            break;
        } else if line.starts_with("|-") {
            has_header = true;
        }
        lines.push(line);
    }

    let parent = arena.append(
        Table::Org {
            tblfm: None,
            post_blank,
            has_header,
        },
        parent,
    );

    for line in lines {
        if line.starts_with("|-") {
            if has_header {
                arena.append(Element::TableRow(TableRow::HeaderRule), parent);
                has_header = false;
            } else {
                arena.append(Element::TableRow(TableRow::BodyRule), parent);
            }
        } else {
            if has_header {
                let parent = arena.append(Element::TableRow(TableRow::Header), parent);
                for content in line.split_terminator('|').skip(1) {
                    let node = arena.append(Element::TableCell(TableCell::Header), parent);
                    containers.push(Container::Inline {
                        content: content.trim(),
                        node,
                    });
                }
            } else {
                let parent = arena.append(Element::TableRow(TableRow::Body), parent);
                for content in line.split_terminator('|').skip(1) {
                    let node = arena.append(Element::TableCell(TableCell::Body), parent);
                    containers.push(Container::Inline {
                        content: content.trim(),
                        node,
                    });
                }
            }
        }
    }

    tail
}

pub fn blank_lines_count(input: &str) -> (&str, usize) {
    crate::parse::combinators::blank_lines_count::<()>(input).unwrap_or((input, 0))
}

pub fn parse_headline(input: &str) -> Option<(&str, (&str, usize))> {
    let (input_, level) = parse_headline_level(input)?;
    let (input_, content) = lines_while::<_, ()>(move |line| {
        parse_headline_level(line)
            .map(|(_, l)| l > level)
            .unwrap_or(true)
    })(input_)
    .unwrap_or((input_, ""));
    Some((input_, (&input[0..level + content.len()], level)))
}

pub fn parse_headline_level(input: &str) -> Option<(&str, usize)> {
    let (input, stars) = take_while1::<_, _, ()>(|c: char| c == '*')(input).ok()?;

    if input.starts_with(' ') || input.starts_with('\n') || input.is_empty() {
        Some((input, stars.len()))
    } else {
        None
    }
}