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//! Building blocks for meta rules.

pub use self::lines::Lines;
pub use self::node::Node;
pub use self::number::Number;
pub use self::optional::Optional;
pub use self::repeat::Repeat;
pub use self::rule::Rule;
pub use self::select::Select;
pub use self::separate_by::SeparateBy;
pub use self::sequence::Sequence;
pub use self::text::Text;
pub use self::token::Token;
pub use self::until_any::UntilAny;
pub use self::until_any_or_whitespace::UntilAnyOrWhitespace;
pub use self::whitespace::Whitespace;

use std::rc::Rc;
use range::Range;
use {
    MetaData,
    ParseError,
};
use tokenizer::TokenizerState;

mod lines;
mod node;
mod number;
mod optional;
mod repeat;
mod rule;
mod select;
mod separate_by;
mod sequence;
mod text;
mod token;
mod until_any;
mod until_any_or_whitespace;
mod whitespace;


/// Parses text with rules.
pub fn parse(
    rules: &[(Rc<String>, Rule)],
    text: &str
) -> Result<Vec<(Range, MetaData)>, (Range, ParseError)> {
    let chars: Vec<char> = text.chars().collect();
    let mut tokens = vec![];
    let s = TokenizerState::new();
    let n = match rules.len() {
        0 => { return Err((Range::empty(0), ParseError::NoRules)); }
        x => x
    };
    let res = rules[n - 1].1.parse(&mut tokens, &s, &chars, 0, rules);
    match res {
        Ok((range, s, opt_error)) => {
            // Report error if did not reach the end of text.
            if range.next_offset() < text.chars().count() {
                Err(ret_err(
                    (Range::empty(range.next_offset()),
                        ParseError::ExpectedEnd),
                    opt_error
                ))
            } else {
                tokens.truncate(s.0);
                Ok(tokens)
            }
        }
        Err((err_range, err)) => {
            Err((err_range, err))
        }
    }
}

/// Updates the references such that they point to each other.
pub fn update_refs(rules: &[(Rc<String>, Rule)]) {
    for r in rules {
        r.1.update_refs(rules);
    }
}

/// A parse result succeeds with a new state,
/// plus an optional error to replace other errors if it is deeper.
/// The deepest error is likely the most useful.
pub type ParseResult<S> = Result<(Range, S, Option<(Range, ParseError)>),
    (Range, ParseError)>;

/// Updates the parser state.
/// Used by rules that have multiple sub rules.
#[inline(always)]
fn update<'a>(
    range: Range,
    err: Option<(Range, ParseError)>,
    chars: &mut &'a [char],
    offset: &mut usize,
    opt_error: &mut Option<(Range, ParseError)>
) {
    let next_offset = range.next_offset();
    *chars = &chars[next_offset - *offset..];
    *offset = next_offset;
    err_update(err, opt_error);
}

/// Picks deepest error, overwriting with the newest one if they are
/// equally deep.
#[inline(always)]
fn err_update(
    err: Option<(Range, ParseError)>,
    opt_error: &mut Option<(Range, ParseError)>
) {
    if let &mut Some(ref mut opt_error) = opt_error {
        if let Some(err) = err {
            if opt_error.0.next_offset() <= err.0.next_offset() {
                *opt_error = err;
            }
        }
    } else {
        *opt_error = err;
    };
}

/// This is used to pick the deepest error or two alternatives,
/// one from a rule that fails certainly and another that could be optional.
#[inline(always)]
fn ret_err(a: (Range, ParseError), b: Option<(Range, ParseError)>) ->
    (Range, ParseError) {
    if let Some(b) = b {
        if b.0.next_offset() > a.0.next_offset() {
            b
        } else {
            a
        }
    } else {
        a
    }
}

#[cfg(test)]
mod tests{
    use range::Range;
    use all::*;

    #[test]
    fn no_rules() {
        assert_eq!(parse(&[], ""),
            Err((Range::empty(0), ParseError::NoRules)));
    }
}