use std::{
    fmt::{Debug, Display},
    ops::Not,
};

use smol_str::SmolStr;

use crate::parameter::{Parameter, ParameterKind, ParameterValue};

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum Token {
    /// Token used to represent a finished command (i.e. no more parameters required)
    // todo: this is likely not the right way to represent this
    Empty,

    /// A bot-defined command / subcommand (usually) (eg. "member" in `pk;member MyName`)
    Value(Vec<SmolStr>),

    /// A parameter that must be provided a value
    Parameter(Parameter),
}

#[derive(Debug)]
pub enum TokenMatchError {
    ParameterMatchError { input: SmolStr, msg: SmolStr },
    MissingParameter { name: SmolStr },
}

#[derive(Debug)]
pub(super) struct TokenMatchValue {
    pub raw: SmolStr,
    pub param: Option<(SmolStr, ParameterValue)>,
}

impl TokenMatchValue {
    fn new_match(raw: impl Into<SmolStr>) -> TryMatchResult {
        Some(Ok(Some(Self {
            raw: raw.into(),
            param: None,
        })))
    }

    fn new_match_param(
        raw: impl Into<SmolStr>,
        param_name: impl Into<SmolStr>,
        param: ParameterValue,
    ) -> TryMatchResult {
        Some(Ok(Some(Self {
            raw: raw.into(),
            param: Some((param_name.into(), param)),
        })))
    }
}

/// None -> no match
/// Some(Ok(None)) -> match, no value
/// Some(Ok(Some(_))) -> match, with value
/// Some(Err(_)) -> error while matching
// q: why do this while we could have a NoMatch in TokenMatchError?
// a: because we want to differentiate between no match and match failure (it matched with an error)
//    "no match" has a different charecteristic because we want to continue matching other tokens...
//    ...while "match failure" means we should stop matching and return the error
type TryMatchResult = Option<Result<Option<TokenMatchValue>, TokenMatchError>>;

impl Token {
    pub(super) fn try_match(&self, input: Option<&str>) -> TryMatchResult {
        let input = match input {
            Some(input) => input,
            None => {
                // short circuit on:
                return match self {
                    // empty token
                    Self::Empty => Some(Ok(None)),
                    // missing paramaters
                    Self::Parameter(param) => Some(Err(TokenMatchError::MissingParameter {
                        name: param.name().into(),
                    })),
                    // everything else doesnt match if no input anyway
                    Self::Value(_) => None,
                    // don't add a _ match here!
                };
            }
        };
        let input = input.trim();

        // try actually matching stuff
        match self {
            Self::Empty => None,
            Self::Value(values) => values
                .iter()
                .any(|v| v.eq(input))
                .then(|| TokenMatchValue::new_match(input))
                .unwrap_or(None),
            Self::Parameter(param) => match param.kind().match_value(input) {
                Ok(matched) => TokenMatchValue::new_match_param(input, param.name(), matched),
                Err(err) => Some(Err(TokenMatchError::ParameterMatchError {
                    input: input.into(),
                    msg: err,
                })),
            }, // don't add a _ match here!
        }
    }
}

impl Display for Token {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Token::Empty => write!(f, ""),
            Token::Value(vec) if vec.is_empty().not() => write!(f, "{}", vec.first().unwrap()),
            Token::Value(_) => Ok(()), // if value token has no values (lol), don't print anything
            Token::Parameter(param) => param.kind().format(f, param.name()),
        }
    }
}

impl From<&str> for Token {
    fn from(value: &str) -> Self {
        Token::Value(vec![SmolStr::new(value)])
    }
}

impl<const L: usize> From<[&str; L]> for Token {
    fn from(value: [&str; L]) -> Self {
        Token::Value(value.into_iter().map(SmolStr::from).collect::<Vec<_>>())
    }
}

impl From<Parameter> for Token {
    fn from(value: Parameter) -> Self {
        Token::Parameter(value)
    }
}

impl From<ParameterKind> for Token {
    fn from(value: ParameterKind) -> Self {
        Token::from(Parameter::from(value))
    }
}

impl From<(&str, ParameterKind)> for Token {
    fn from(value: (&str, ParameterKind)) -> Self {
        Token::from(Parameter::from(value))
    }
}