use std::num::NonZero;

pub const PARAM_PREFIX: &str = "__param_";

#[derive(Clone, Debug)]
pub enum Parameter {
    Anonymous(NonZero<usize>),
    Indexed(NonZero<usize>),
    Named(String, NonZero<usize>),
}

impl PartialEq for Parameter {
    fn eq(&self, other: &Self) -> bool {
        self.index() == other.index()
    }
}

impl Parameter {
    pub fn index(&self) -> NonZero<usize> {
        match self {
            Parameter::Anonymous(index) => *index,
            Parameter::Indexed(index) => *index,
            Parameter::Named(_, index) => *index,
        }
    }
}

#[derive(Debug)]
pub struct Parameters {
    index: NonZero<usize>,
    pub list: Vec<Parameter>,
}

impl Default for Parameters {
    fn default() -> Self {
        Self::new()
    }
}

impl Parameters {
    pub fn new() -> Self {
        Self {
            index: 1.try_into().unwrap(),
            list: vec![],
        }
    }

    pub fn count(&self) -> usize {
        let mut params = self.list.clone();
        params.dedup();
        params.len()
    }

    pub fn name(&self, index: NonZero<usize>) -> Option<String> {
        self.list.iter().find_map(|p| match p {
            Parameter::Anonymous(i) if *i == index => Some("?".to_string()),
            Parameter::Indexed(i) if *i == index => Some(format!("?{i}")),
            Parameter::Named(name, i) if *i == index => Some(name.to_owned()),
            _ => None,
        })
    }

    pub fn index(&self, name: impl AsRef<str>) -> Option<NonZero<usize>> {
        self.list
            .iter()
            .find_map(|p| match p {
                Parameter::Named(n, index) if n == name.as_ref() => Some(index),
                _ => None,
            })
            .copied()
    }

    pub fn next_index(&mut self) -> NonZero<usize> {
        let index = self.index;
        self.index = self.index.checked_add(1).unwrap();
        index
    }

    pub fn push(&mut self, name: impl AsRef<str>) -> NonZero<usize> {
        match name.as_ref() {
            param if param.is_empty() || param.starts_with(PARAM_PREFIX) => {
                let index = self.next_index();
                let use_idx = if let Some(idx) = param.strip_prefix(PARAM_PREFIX) {
                    idx.parse().unwrap()
                } else {
                    index
                };
                self.list.push(Parameter::Anonymous(use_idx));
                tracing::trace!("anonymous parameter at {use_idx}");
                use_idx
            }
            name if name.starts_with(['$', ':', '@', '#']) => {
                match self
                    .list
                    .iter()
                    .find(|p| matches!(p, Parameter::Named(n, _) if name == n))
                {
                    Some(t) => {
                        let index = t.index();
                        self.list.push(t.clone());
                        tracing::trace!("named parameter at {index} as {name}");
                        index
                    }
                    None => {
                        let index = self.next_index();
                        self.list.push(Parameter::Named(name.to_owned(), index));
                        tracing::trace!("named parameter at {index} as {name}");
                        index
                    }
                }
            }
            index => {
                // SAFETY: Guaranteed from parser that the index is bigger than 0.
                let index: NonZero<usize> = index.parse().unwrap();
                if index > self.index {
                    self.index = index.checked_add(1).unwrap();
                }
                self.list.push(Parameter::Indexed(index));
                tracing::trace!("indexed parameter at {index}");
                index
            }
        }
    }
}