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use std::{
    io::Read,
    sync::atomic::{AtomicI32, Ordering},
};

use lazy_static::lazy_static;
use tokio::io::{AsyncWrite, AsyncWriteExt};

use crate::error::Result;

/// Closure to obtain a new, unique request ID.
pub(crate) fn next_request_id() -> i32 {
    lazy_static! {
        static ref REQUEST_ID: AtomicI32 = AtomicI32::new(0);
    }

    REQUEST_ID.fetch_add(1, Ordering::SeqCst)
}

/// Serializes `string` to bytes and writes them to `writer` with a null terminator appended.
pub(super) async fn write_cstring<W: AsyncWrite + Unpin>(
    writer: &mut W,
    string: &str,
) -> Result<()> {
    // Write the string's UTF-8 bytes.
    writer.write_all(string.as_bytes()).await?;

    // Write the null terminator.
    writer.write_all(&[0]).await?;

    Ok(())
}

pub(super) struct SyncCountReader<R> {
    reader: R,
    bytes_read: usize,
}

impl<R: Read> SyncCountReader<R> {
    /// Constructs a new CountReader that wraps `reader`.
    pub(super) fn new(reader: R) -> Self {
        SyncCountReader {
            reader,
            bytes_read: 0,
        }
    }

    /// Gets the number of bytes read so far.
    pub(super) fn bytes_read(&self) -> usize {
        self.bytes_read
    }
}

impl<R: Read> Read for SyncCountReader<R> {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let bytes = self.reader.read(buf)?;
        self.bytes_read += bytes;
        Ok(bytes)
    }
}