use std::fmt;

use crate::sharry;

pub struct Chunk<'t> {
    file_id: sharry::FileID,
    offset: u64,
    data: &'t [u8],
}

impl fmt::Debug for Chunk<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Chunk")
            .field("file_id", &self.file_id)
            .field("offset", &self.offset)
            .field("data.len()", &self.data.len())
            .finish_non_exhaustive()
    }
}

impl<'t> Chunk<'t> {
    pub(super) fn new_direct(file_id: sharry::FileID, offset: u64, data: &'t [u8]) -> Self {
        Self {
            file_id,
            offset,
            data,
        }
    }

    pub fn get_file_id(&self) -> &sharry::FileID {
        &self.file_id
    }

    pub fn get_offset(&self) -> u64 {
        self.offset
    }

    pub fn get_data(&self) -> &[u8] {
        self.data
    }

    pub(super) fn get_length(&self) -> u64 {
        let len = self.data.len();

        // BOOKMARK this might **panic** on platforms where `usize` has more than 64 bit.
        // Also, you've allocated more than 2 EiB ... in ONE chunk.
        // Whoa! Maybe just chill?
        u64::try_from(len).unwrap_or_else(|e| panic!("usize={len} did not fit into u64: {e}"))
    }

    pub fn get_behind(&self) -> u64 {
        self.offset + self.get_length()
    }
}

#[cfg(test)]
mod tests {
    // use super::*;

    // #[test]
    // fn basic_tests() {
    //     let mut foo = [0u8; 10];
    //     let fid = sharry::FileID("fid".to_string());
    // }
}