platform-lino 0.7.0

use nom::{
    IResult,
    branch::alt,
    bytes::complete::{take_while, take_while1, is_not},
    character::complete::{char, line_ending},
    combinator::eof,
    multi::{many0, many1},
    sequence::{preceded, terminated, delimited},
    Parser,
};
use std::cell::RefCell;

#[derive(Debug, Clone, PartialEq)]
pub struct Link {
    pub id: Option<String>,
    pub values: Vec<Link>,
    pub children: Vec<Link>,
    pub is_indented_id: bool,
}

impl Link {
    pub fn new_singlet(id: String) -> Self {
        Link {
            id: Some(id),
            values: vec![],
            children: vec![],
            is_indented_id: false,
        }
    }

    pub fn new_indented_id(id: String) -> Self {
        Link {
            id: Some(id),
            values: vec![],
            children: vec![],
            is_indented_id: true,
        }
    }

    pub fn new_value(values: Vec<Link>) -> Self {
        Link {
            id: None,
            values,
            children: vec![],
            is_indented_id: false,
        }
    }

    pub fn new_link(id: Option<String>, values: Vec<Link>) -> Self {
        Link {
            id,
            values,
            children: vec![],
            is_indented_id: false,
        }
    }

    pub fn with_children(mut self, children: Vec<Link>) -> Self {
        self.children = children;
        self
    }
}

pub struct ParserState {
    indentation_stack: RefCell<Vec<usize>>,
}

impl ParserState {
    pub fn new() -> Self {
        ParserState {
            indentation_stack: RefCell::new(vec![0]),
        }
    }

    pub fn push_indentation(&self, indent: usize) {
        self.indentation_stack.borrow_mut().push(indent);
    }

    pub fn pop_indentation(&self) {
        let mut stack = self.indentation_stack.borrow_mut();
        if stack.len() > 1 {
            stack.pop();
        }
    }

    pub fn current_indentation(&self) -> usize {
        *self.indentation_stack.borrow().last().unwrap_or(&0)
    }

    pub fn check_indentation(&self, indent: usize) -> bool {
        indent >= self.current_indentation()
    }
}

fn is_whitespace_char(c: char) -> bool {
    c == ' ' || c == '\t' || c == '\n' || c == '\r'
}

fn is_horizontal_whitespace(c: char) -> bool {
    c == ' ' || c == '\t'
}

fn is_reference_char(c: char) -> bool {
    !is_whitespace_char(c) && c != '(' && c != ':' && c != ')'
}

fn horizontal_whitespace(input: &str) -> IResult<&str, &str> {
    take_while(is_horizontal_whitespace)(input)
}

fn whitespace(input: &str) -> IResult<&str, &str> {
    take_while(is_whitespace_char)(input)
}

fn simple_reference(input: &str) -> IResult<&str, String> {
    take_while1(is_reference_char)
        .map(|s: &str| s.to_string())
        .parse(input)
}

fn double_quoted_reference(input: &str) -> IResult<&str, String> {
    delimited(
        char('"'),
        is_not("\""),
        char('"')
    )
    .map(|s: &str| s.to_string())
    .parse(input)
}

fn single_quoted_reference(input: &str) -> IResult<&str, String> {
    delimited(
        char('\''),
        is_not("'"),
        char('\'')
    )
    .map(|s: &str| s.to_string())
    .parse(input)
}

fn reference(input: &str) -> IResult<&str, String> {
    alt((
        double_quoted_reference,
        single_quoted_reference,
        simple_reference,
    )).parse(input)
}

fn eol(input: &str) -> IResult<&str, &str> {
    alt((
        preceded(horizontal_whitespace, line_ending),
        preceded(horizontal_whitespace, eof),
    )).parse(input)
}



fn reference_or_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    alt((
        |i| multi_line_any_link(i, state),
        reference.map(Link::new_singlet),
    )).parse(input)
}

fn multi_line_value_and_whitespace<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    terminated(
        |i| reference_or_link(i, state),
        whitespace
    ).parse(input)
}

fn multi_line_values<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Vec<Link>> {
    preceded(
        whitespace,
        many0(|i| multi_line_value_and_whitespace(i, state))
    ).parse(input)
}

fn single_line_value_and_whitespace<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    preceded(
        horizontal_whitespace,
        |i| reference_or_link(i, state)
    ).parse(input)
}

fn single_line_values<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Vec<Link>> {
    many1(|i| single_line_value_and_whitespace(i, state)).parse(input)
}

fn single_line_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    (
        horizontal_whitespace,
        reference,
        horizontal_whitespace,
        char(':'),
        |i| single_line_values(i, state)
    ).map(|(_, id, _, _, values)| Link::new_link(Some(id), values))
    .parse(input)
}

fn multi_line_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    (
        char('('),
        whitespace,
        reference,
        whitespace,
        char(':'),
        |i| multi_line_values(i, state),
        whitespace,
        char(')')
    ).map(|(_, _, id, _, _, values, _, _)| Link::new_link(Some(id), values))
    .parse(input)
}

fn single_line_value_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    (|i| single_line_values(i, state))
        .map(|values| {
            if values.len() == 1 && values[0].id.is_some() && values[0].values.is_empty() && values[0].children.is_empty() {
                Link::new_singlet(values[0].id.clone().unwrap())
            } else {
                Link::new_value(values)
            }
        })
        .parse(input)
}

fn indented_id_link<'a>(input: &'a str, _state: &ParserState) -> IResult<&'a str, Link> {
    (
        reference,
        horizontal_whitespace,
        char(':'),
        eol
    ).map(|(id, _, _, _)| Link::new_indented_id(id))
    .parse(input)
}

fn multi_line_value_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    (
        char('('),
        |i| multi_line_values(i, state),
        whitespace,
        char(')')
    ).map(|(_, values, _, _)| {
        if values.len() == 1 && values[0].id.is_some() && values[0].values.is_empty() && values[0].children.is_empty() {
            Link::new_singlet(values[0].id.clone().unwrap())
        } else {
            Link::new_value(values)
        }
    })
    .parse(input)
}

fn multi_line_any_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    alt((
        |i| multi_line_value_link(i, state),
        |i| multi_line_link(i, state),
    )).parse(input)
}

fn single_line_any_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    alt((
        terminated(|i| single_line_link(i, state), eol),
        terminated(|i| single_line_value_link(i, state), eol),
    )).parse(input)
}

fn any_link<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    alt((
        terminated(|i| multi_line_any_link(i, state), eol),
        |i| indented_id_link(i, state),
        |i| single_line_any_link(i, state),
    )).parse(input)
}

fn count_indentation(input: &str) -> IResult<&str, usize> {
    take_while(|c| c == ' ')
        .map(|s: &str| s.len())
        .parse(input)
}

fn push_indentation<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, ()> {
    let (input, spaces) = count_indentation(input)?;
    let current = state.current_indentation();
    
    if spaces > current {
        state.push_indentation(spaces);
        Ok((input, ()))
    } else {
        Err(nom::Err::Error(nom::error::Error::new(input, nom::error::ErrorKind::Verify)))
    }
}

fn check_indentation<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, ()> {
    let (input, spaces) = count_indentation(input)?;
    
    if state.check_indentation(spaces) {
        Ok((input, ()))
    } else {
        Err(nom::Err::Error(nom::error::Error::new(input, nom::error::ErrorKind::Verify)))
    }
}

fn element<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    let (input, link) = any_link(input, state)?;
    
    if let Ok((input, _)) = push_indentation(input, state) {
        let (input, children) = links(input, state)?;
        Ok((input, link.with_children(children)))
    } else {
        Ok((input, link))
    }
}

fn first_line<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    element(input, state)
}

fn line<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Link> {
    preceded(
        |i| check_indentation(i, state),
        |i| element(i, state)
    ).parse(input)
}

fn links<'a>(input: &'a str, state: &ParserState) -> IResult<&'a str, Vec<Link>> {
    let (input, first) = first_line(input, state)?;
    let (input, rest) = many0(|i| line(i, state)).parse(input)?;
    
    state.pop_indentation();
    
    let mut result = vec![first];
    result.extend(rest);
    Ok((input, result))
}

pub fn parse_document(input: &str) -> IResult<&str, Vec<Link>> {
    let state = ParserState::new();
    
    // Skip leading whitespace but preserve the line structure
    let input = input.trim_start_matches(|c: char| c == '\n' || c == '\r');
    
    // Handle empty or whitespace-only documents
    if input.trim().is_empty() {
        return Ok(("", vec![]));
    }
    
    let (input, result) = links(input, &state)?;
    let (input, _) = whitespace(input)?;
    let (input, _) = eof(input)?;
    
    Ok((input, result))
}