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use std::pin::Pin;

use bytes::Bytes;
use futures::{
  stream::Stream,
  task::{Context, Poll},
};
use log::{error, trace};
use pin_project::pin_project;
use reqwest::{self, Method, StatusCode};

use crate::{
  errors::{Error, Result},
  v2::*,
};

impl Client {
  /// Check if a blob exists.
  pub async fn has_blob(&self, name: &str, digest: &str) -> Result<bool> {
    let url = {
      let ep = format!("{}/v2/{}/blobs/{}", self.base_url, name, digest);
      reqwest::Url::parse(&ep)?
    };

    let res = self.build_reqwest(Method::HEAD, url.clone()).send().await?;

    trace!("Blob HEAD status: {:?}", res.status());

    match res.status() {
      StatusCode::OK => Ok(true),
      _ => Ok(false),
    }
  }

  pub async fn get_blob_response(&self, name: &str, digest: &str) -> Result<BlobResponse> {
    let ep = format!("{}/v2/{}/blobs/{}", self.base_url, name, digest);
    let url = reqwest::Url::parse(&ep)?;

    let resp = self.build_reqwest(Method::GET, url.clone()).send().await?;

    let status = resp.status();
    trace!("GET {} status: {}", resp.url(), status);

    match resp.error_for_status_ref() {
      Ok(_) => {
        if let Some(len) = resp.content_length() {
          trace!("Receiving a blob with {} bytes", len);
        } else {
          trace!("Receiving a blob");
        }
        Ok(BlobResponse::new(resp, ContentDigest::try_new(digest)?))
      }
      Err(_) if status.is_client_error() => Err(Error::Client { status }),
      Err(_) if status.is_server_error() => Err(Error::Server { status }),
      Err(_) => {
        error!("Received unexpected HTTP status '{}'", status);
        Err(Error::UnexpectedHttpStatus(status))
      }
    }
  }

  /// Retrieve blob.
  pub async fn get_blob(&self, name: &str, digest: &str) -> Result<Vec<u8>> {
    self.get_blob_response(name, digest).await?.bytes().await
  }

  /// Retrieve blob stream.
  pub async fn get_blob_stream(&self, name: &str, digest: &str) -> Result<impl Stream<Item = Result<Vec<u8>>>> {
    Ok(self.get_blob_response(name, digest).await?.stream())
  }
}

#[derive(Debug)]
pub struct BlobResponse {
  resp: reqwest::Response,
  digest: ContentDigest,
}

impl BlobResponse {
  fn new(resp: reqwest::Response, digest: ContentDigest) -> Self {
    Self { resp, digest }
  }

  /// Get size of the blob.
  /// This method can be useful to render progress bar when downloading a blob.
  pub fn size(&self) -> Option<u64> {
    self.resp.content_length()
  }

  /// Retrieve content of the blob.
  pub async fn bytes(self) -> Result<Vec<u8>> {
    let blob = self.resp.bytes().await?.to_vec();

    let mut digest = self.digest;
    digest.update(&blob);
    digest.verify()?;

    Ok(blob)
  }

  /// Get bytes stream of the blob.
  pub fn stream(self) -> impl Stream<Item = Result<Vec<u8>>> {
    BlobStream::new(self.resp.bytes_stream(), self.digest)
  }
}

#[pin_project]
struct BlobStream<S>
where
  S: Stream<Item = reqwest::Result<Bytes>>,
{
  #[pin]
  stream: S,
  #[pin]
  digest: Option<ContentDigest>,
}

impl<S> BlobStream<S>
where
  S: Stream<Item = reqwest::Result<Bytes>> + Unpin,
{
  fn new(stream: S, digest: ContentDigest) -> Self {
    Self {
      stream,
      digest: Some(digest),
    }
  }
}

impl<S> Stream for BlobStream<S>
where
  S: Stream<Item = reqwest::Result<Bytes>> + Unpin,
{
  type Item = Result<Vec<u8>>;

  fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
    let mut this = self.project();
    match this.stream.poll_next(cx) {
      Poll::Ready(Some(chunk_res)) => {
        let mut digest = match this.digest.as_pin_mut() {
          Some(digest) => digest,
          None => return Poll::Ready(None),
        };
        let chunk = chunk_res?;
        digest.update(&chunk);
        Poll::Ready(Some(Ok(chunk.to_vec())))
      }
      Poll::Ready(None) => match this.digest.take() {
        Some(digest) => match digest.verify() {
          Ok(()) => Poll::Ready(None),
          Err(err) => Poll::Ready(Some(Err(err.into()))),
        },
        None => Poll::Ready(None),
      },
      Poll::Pending => Poll::Pending,
    }
  }
}