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pub mod errors;

#[cfg(test)]
pub mod tests;

use crate::lexing::{ Token, TokenKind };

use self::errors::SyntacticalError;

/// Arguments can either be positional or named. Positional arguments are
/// identified by their position relative to the command name. Note that
/// named arguments are not counted towards the positional argument count.
/// Named arguments are identified by a flag, which is an identifier prefixed
/// by a dash. The flag may be followed by a value, which is separated by a
/// space. If the value is not present, the argument is considered a flag.
#[derive(Debug)]
#[allow(dead_code)]
pub struct Argument {
    name: Option<String>,
    value: Option<String>,
    position: Option<usize>,
}

pub fn parse(mut input: Vec<Token>) -> Result<Vec<Argument>, SyntacticalError> {
    let mut arguments: Vec<Argument> = Vec::new();
    while !input.is_empty() {
        let result = parse_argument(
            &mut input,
            arguments
                .iter()
                .filter(|it| it.position.is_some())
                .count()
        );

        if let Err(e) = result {
            return Err(e);
        } else if let Ok(result) = result {
            arguments.push(result);
        }
    }

    Ok(arguments)
}

fn parse_argument(
    input: &mut Vec<Token>,
    positional_count: usize
) -> Result<Argument, SyntacticalError> {
    let token = input.get(0).unwrap();
    match token.get_kind() {
        TokenKind::Dash => {
            input.remove(0);
            parse_named_argument(input)
        }
        _ => Ok(parse_positional_argument(input, positional_count)),
    }
}

fn parse_named_argument(input: &mut Vec<Token>) -> Result<Argument, SyntacticalError> {
    let key = input.remove(0);
    if input.is_empty() || *input[0].get_kind() != TokenKind::Equals {
        let got = if input.is_empty() { String::from("EOF") } else { input[0].get_value().clone() };
        return Err(SyntacticalError::ExpectedToken(String::from("="), got));
    }
    let _ = input.remove(0);

    let value = input.remove(0);

    Ok(Argument {
        name: Some(key.get_value().clone()),
        value: Some(value.get_value().clone()),
        position: None,
    })
}

fn parse_positional_argument(input: &mut Vec<Token>, count: usize) -> Argument {
    let value = input.remove(0);

    Argument {
        name: None,
        value: Some(value.get_value().clone()),
        position: Some(count),
    }
}