use super::{name::*, parse::*, value::*};

/// An iterator over the parameters.
#[derive(Debug)]
pub struct Params<'a> {
    source: ParamsSource<'a>,
    index: usize,
}

impl<'a> Params<'a> {
    pub(crate) fn from_slice(s: &'a [(Name<'a>, Value<'a>)]) -> Self {
        Self {
            source: ParamsSource::Slice(s),
            index: 0,
        }
    }

    pub(crate) fn from_indices(s: &'a str, i: &'a Indices) -> Self {
        Self {
            source: ParamsSource::Indices(s, i),
            index: 0,
        }
    }
}

#[derive(Debug)]
enum ParamsSource<'a> {
    Slice(&'a [(Name<'a>, Value<'a>)]),
    Indices(&'a str, &'a Indices),
}

impl<'a> Iterator for Params<'a> {
    type Item = (&'a str, &'a str);

    fn next(&mut self) -> Option<Self::Item> {
        let index = self.index;
        match self.source {
            ParamsSource::Slice(s) => {
                if index >= s.len() {
                    None
                } else {
                    self.index += 1;
                    Some((s[index].0.as_ref(), s[index].1.as_ref()))
                }
            }
            ParamsSource::Indices(s, i) => {
                if index >= i.params().len() {
                    None
                } else {
                    self.index += 1;
                    let param = i.params()[index];
                    Some((
                        &s[param[0] as usize..param[1] as usize],
                        &s[param[2] as usize..param[3] as usize],
                    ))
                }
            }
        }
    }
}
