use std::process::{Command, Stdio};

use tokio_stream::wrappers::ReceiverStream;

use crate::bare::GitBare;
use crate::pb::{ArchiveChunk, ArchiveRequest, archive_options, object_selector};

impl GitBare {
    /// Stream archive data via a channel to avoid loading the entire archive into memory.
    /// Returns a ReceiverStream that yields ArchiveChunk as the subprocess produces output.
    pub fn get_archive_stream(
        &self,
        request: ArchiveRequest,
    ) -> Result<ReceiverStream<Result<ArchiveChunk, tonic::Status>>, tonic::Status> {
        let bare_dir = self.bare_dir.clone();
        tracing::info!(
            repo = %bare_dir.display(),
            "spawning git archive subprocess"
        );

        let (tx, rx) = tokio::sync::mpsc::channel(16);

        let revision = match request.treeish.and_then(|s| s.selector) {
            Some(object_selector::Selector::Oid(oid)) => {
                crate::sanitize::validate_oid_hex(&oid.hex)
                    .map_err(|e| tonic::Status::invalid_argument(e.to_string()))?;
                oid.hex
            }
            Some(object_selector::Selector::Revision(name)) => {
                crate::sanitize::validate_revision(&name.revision)
                    .map_err(|e| tonic::Status::invalid_argument(e.to_string()))?;
                name.revision
            }
            None => "HEAD".into(),
        };

        let options = request.options.unwrap_or_default();
        if !options.prefix.is_empty() {
            crate::sanitize::validate_file_path(&options.prefix)
                .map_err(|e| tonic::Status::invalid_argument(e.to_string()))?;
        }
        for path in &options.pathspec {
            crate::sanitize::validate_file_path(path)
                .map_err(|e| tonic::Status::invalid_argument(e.to_string()))?;
        }

        tokio::task::spawn_blocking(move || {
            let format = archive_options::Format::try_from(options.format)
                .unwrap_or(archive_options::Format::ArchiveFormatTar);
            let mut args = vec!["archive".to_string()];
            args.push(match format {
                archive_options::Format::ArchiveFormatZip => "--format=zip".into(),
                _ => "--format=tar".into(),
            });
            if !options.prefix.is_empty() {
                args.push(format!("--prefix={}", options.prefix));
            }
            args.push(revision);
            if !options.pathspec.is_empty() {
                args.push("--".into());
                args.extend(options.pathspec);
            }

            let mut child = match Command::new("git")
                .arg("--git-dir")
                .arg(&bare_dir)
                .args(&args)
                .stdout(Stdio::piped())
                .stderr(Stdio::piped())
                .spawn()
            {
                Ok(c) => c,
                Err(e) => {
                    let _ = tx.blocking_send(Err(tonic::Status::internal(format!(
                        "failed to spawn git archive: {e}"
                    ))));
                    return;
                }
            };

            let stdout = match child.stdout.take() {
                Some(s) => s,
                None => {
                    let _ =
                        tx.blocking_send(Err(tonic::Status::internal("failed to capture stdout")));
                    return;
                }
            };

            use std::io::Read;
            let mut reader = std::io::BufReader::new(stdout);
            let mut buf = vec![0u8; 65536];
            loop {
                match reader.read(&mut buf) {
                    Ok(0) => break,
                    Ok(n) => {
                        let chunk = ArchiveChunk {
                            data: buf[..n].to_vec(),
                        };
                        if tx.blocking_send(Ok(chunk)).is_err() {
                            break;
                        }
                    }
                    Err(e) => {
                        let _ = tx.blocking_send(Err(tonic::Status::internal(format!(
                            "read error: {e}"
                        ))));
                        break;
                    }
                }
            }

            match child.wait() {
                Ok(status) if !status.success() => {
                    let _ = tx.blocking_send(Err(tonic::Status::internal(
                        "git archive exited with error",
                    )));
                }
                Err(e) => {
                    let _ =
                        tx.blocking_send(Err(tonic::Status::internal(format!("wait error: {e}"))));
                }
                _ => {}
            }
        });

        Ok(ReceiverStream::new(rx))
    }
}