use std::path::Path;

use crate::{error::Result, model::ContentHash};

const BUFFER_SIZE: usize = 65536;

/// Computes the BLAKE3 hash of a file asynchronously.
///
/// # Arguments
///
/// * `path` - Path to the file to hash
///
/// # Returns
///
/// The content hash
///
/// # Errors
///
/// Returns I/O errors or task execution errors
pub async fn compute_file_hash(path: &Path) -> Result<ContentHash> {
  let path = path.to_path_buf();
  let hash = tokio::task::spawn_blocking(move || -> Result<ContentHash> {
    let mut hasher = blake3::Hasher::new();
    let mut file = std::fs::File::open(&path)?;
    let mut buf = vec![0u8; BUFFER_SIZE];
    loop {
      let n = std::io::Read::read(&mut file, &mut buf)?;
      if n == 0 {
        break;
      }
      hasher.update(&buf[..n]);
    }
    Ok(ContentHash::new(hasher.finalize().to_hex().to_string()))
  })
  .await
  .map_err(|e| crate::error::PinakesError::Io(std::io::Error::other(e)))??;
  Ok(hash)
}

/// Computes the BLAKE3 hash of a byte slice synchronously.
#[must_use]
pub fn compute_hash_sync(data: &[u8]) -> ContentHash {
  let hash = blake3::hash(data);
  ContentHash::new(hash.to_hex().to_string())
}