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use std::ops::{Index, IndexMut};

use super::StructuredBlock;
use crate::FlatBlock;

#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub struct BlockId(pub usize);

/// A convenient wrapper around a vector of blocks.
/// This is used instead of id_arena, since the latter is harder to clone and modify.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct Blocks<T>(pub Vec<T>);

impl<T> Blocks<T> {
    pub fn new() -> Self {
        Blocks(vec![])
    }
    pub fn alloc(&mut self, block: T) -> BlockId {
        let res = BlockId(self.0.len());
        self.0.push(block);
        res
    }
    pub fn iter(&self) -> BlocksIter<'_, T> {
        self.into_iter()
    }

    pub fn len(&self) -> usize {
        self.0.len()
    }

    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }
}
impl<T> Index<BlockId> for Blocks<T> {
    type Output = T;

    fn index(&self, index: BlockId) -> &Self::Output {
        &self.0[index.0]
    }
}
impl<T> IndexMut<BlockId> for Blocks<T> {
    fn index_mut(&mut self, index: BlockId) -> &mut Self::Output {
        &mut self.0[index.0]
    }
}
impl<'a, T> IntoIterator for &'a Blocks<T> {
    type Item = (BlockId, &'a T);
    type IntoIter = BlocksIter<'a, T>;

    fn into_iter(self) -> Self::IntoIter {
        BlocksIter { blocks: self, index: 0 }
    }
}
pub struct BlocksIter<'a, T> {
    pub blocks: &'a Blocks<T>,
    pub index: usize,
}
impl<'a, T> Iterator for BlocksIter<'a, T> {
    type Item = (BlockId, &'a T);

    fn next(&mut self) -> Option<Self::Item> {
        self.blocks.0.get(self.index).map(|b| {
            let res = (BlockId(self.index), b);
            self.index += 1;
            res
        })
    }
}

pub type StructuredBlocks = Blocks<StructuredBlock>;
pub type FlatBlocks = Blocks<FlatBlock>;