use crate::actor::message::RefUpdateEvent;
use crate::pb::Oid;
use std::path::{Path, PathBuf};

pub struct BundleApplicator {
    pub repo_path: PathBuf,
}

impl BundleApplicator {
    pub fn new(repo_path: PathBuf) -> Self {
        Self { repo_path }
    }

    pub fn apply_bundle(&self, data: &[u8]) -> Result<(), String> {
        let mut child = std::process::Command::new("git")
            .args([
                "--git-dir",
                &self.repo_path.to_string_lossy(),
                "bundle",
                "unbundle",
                "-",
            ])
            .stdin(std::process::Stdio::piped())
            .stdout(std::process::Stdio::piped())
            .stderr(std::process::Stdio::piped())
            .spawn()
            .map_err(|e| format!("spawn git bundle unbundle: {e}"))?;
        use std::io::Write;
        if let Some(ref mut stdin) = child.stdin {
            stdin
                .write_all(data)
                .map_err(|e| format!("write bundle: {e}"))?;
        }
        let output = child
            .wait_with_output()
            .map_err(|e| format!("wait bundle: {e}"))?;
        if !output.status.success() {
            return Err(String::from_utf8_lossy(&output.stderr).into_owned());
        }
        Ok(())
    }

    /// Apply bundle from a file path (for streaming writes).
    pub fn apply_bundle_from_file(&self, path: &Path) -> Result<(), String> {
        let file = std::fs::File::open(path).map_err(|e| format!("open bundle file: {e}"))?;
        let mut child = std::process::Command::new("git")
            .args([
                "--git-dir",
                &self.repo_path.to_string_lossy(),
                "bundle",
                "unbundle",
                "-",
            ])
            .stdin(std::process::Stdio::piped())
            .stdout(std::process::Stdio::piped())
            .stderr(std::process::Stdio::piped())
            .spawn()
            .map_err(|e| format!("spawn git bundle unbundle: {e}"))?;

        // Stream file contents to stdin in a background thread
        let mut stdin = child.stdin.take().ok_or("no stdin")?;
        let file_handle = file;
        let writer = std::thread::spawn(move || -> Result<(), String> {
            use std::io::{Read, Write};
            let mut reader = std::io::BufReader::new(file_handle);
            let mut buf = vec![0u8; 65536];
            loop {
                match reader.read(&mut buf) {
                    Ok(0) => break,
                    Ok(n) => {
                        stdin
                            .write_all(&buf[..n])
                            .map_err(|e| format!("write to stdin: {e}"))?;
                    }
                    Err(e) => return Err(format!("read bundle file: {e}")),
                }
            }
            Ok(())
        });

        let output = child
            .wait_with_output()
            .map_err(|e| format!("wait bundle: {e}"))?;

        // Wait for writer thread
        let _ = writer.join().map_err(|_| "writer thread panicked")?;

        if !output.status.success() {
            return Err(String::from_utf8_lossy(&output.stderr).into_owned());
        }
        Ok(())
    }
}

pub fn collect_local_haves(repo_path: &Path) -> Result<Vec<Oid>, String> {
    let result = std::process::Command::new("git")
        .args([
            "--git-dir",
            &repo_path.to_string_lossy(),
            "for-each-ref",
            "--format=%(objectname)",
        ])
        .stdout(std::process::Stdio::piped())
        .stderr(std::process::Stdio::piped())
        .output()
        .map_err(|e| format!("git for-each-ref: {e}"))?;

    if !result.status.success() {
        return Err(String::from_utf8_lossy(&result.stderr).into_owned());
    }

    let stdout = String::from_utf8_lossy(&result.stdout);
    let haves: Vec<Oid> = stdout
        .lines()
        .filter(|line| !line.trim().is_empty() && line.trim() != crate::oid::ZERO_OID)
        .map(|hex| {
            let hex = hex.trim().to_string();
            Oid {
                value: crate::oid::hex_to_bytes(&hex).unwrap_or_default(),
                hex,
                format: crate::pb::ObjectFormat::Sha1 as i32,
            }
        })
        .collect();

    tracing::debug!(
        repo = %repo_path.display(),
        haves_count = haves.len(),
        "collected local haves from refs"
    );
    Ok(haves)
}

pub async fn sync_from_primary(event: RefUpdateEvent, local_repo_path: PathBuf) {
    tracing::info!(
        relative_path = %event.relative_path,
        ref_name = %event.ref_name,
        primary = %event.primary_grpc_addr,
        "replica sync starting"
    );

    let grpc_addr = event.primary_grpc_addr.clone();
    let relative_path = event.relative_path.clone();
    let repo_for_haves = local_repo_path.clone();

    // Collect haves in a blocking thread
    let haves = match tokio::task::spawn_blocking(move || collect_local_haves(&repo_for_haves))
        .await
    {
        Ok(Ok(h)) => h,
        Ok(Err(e)) => {
            tracing::error!(relative_path = %event.relative_path, error = %e, "collect haves failed");
            return;
        }
        Err(e) => {
            tracing::error!(relative_path = %event.relative_path, error = %e, "haves task failed");
            return;
        }
    };

    // Stream pack data to a temporary file to avoid OOM
    let temp_dir = local_repo_path.join(".gitks_tmp");
    if let Err(e) = std::fs::create_dir_all(&temp_dir) {
        tracing::error!(relative_path = %event.relative_path, error = %e, "create temp dir failed");
        return;
    }

    let pack_result =
        sync_via_pack_service_to_file(&grpc_addr, &relative_path, &haves, &temp_dir).await;

    match pack_result {
        Ok(Some(pack_file)) => {
            let repo = local_repo_path.clone();
            let pack_path = pack_file.clone();
            match tokio::task::spawn_blocking(move || {
                let applicator = BundleApplicator::new(repo);
                applicator.apply_bundle_from_file(&pack_path)
            })
            .await
            {
                Ok(Ok(())) => {
                    update_local_ref(&local_repo_path, &event.ref_name, &event.new_oid);
                    tracing::info!(
                        relative_path = %event.relative_path,
                        "replica sync done"
                    );
                }
                Ok(Err(e)) => {
                    tracing::error!(relative_path = %event.relative_path, error = %e, "pack apply failed")
                }
                Err(e) => {
                    tracing::error!(relative_path = %event.relative_path, error = %e, "apply task failed")
                }
            }
            // Cleanup temp file
            let _ = std::fs::remove_file(&pack_file);
        }
        Ok(None) => {
            tracing::warn!(relative_path = %event.relative_path, "empty pack data from primary")
        }
        Err(e) => {
            tracing::error!(relative_path = %event.relative_path, error = %e, "pack fetch failed")
        }
    }

    // Cleanup temp dir if empty
    let _ = std::fs::remove_dir(&temp_dir);
}

/// Maximum pack size before we reject (10GB)
const MAX_PACK_SIZE: u64 = 10 * 1024 * 1024 * 1024;

/// Stream pack data from primary to a temporary file.
/// Returns Ok(Some(path)) on success, Ok(None) if empty, Err on failure.
async fn sync_via_pack_service_to_file(
    grpc_addr: &str,
    relative_path: &str,
    haves: &[Oid],
    temp_dir: &Path,
) -> Result<Option<PathBuf>, String> {
    use crate::pb::pack_service_client::PackServiceClient;
    use crate::pb::{AdvertiseRefsRequest, PackObjectsOptions, PackObjectsRequest, RepositoryHeader};
    use tokio::io::AsyncWriteExt;
    use tokio_stream::StreamExt;

    let endpoint = crate::server::remote_endpoint(grpc_addr)
        .await
        .map_err(|e| e.to_string())?;

    let mut client = PackServiceClient::connect(endpoint)
        .await
        .map_err(|e| format!("connect to primary: {e}"))?;

    let header = RepositoryHeader {
        storage_name: String::new(),
        relative_path: relative_path.to_string(),
        storage_path: String::new(),
    };

    let refs_resp = client
        .advertise_refs(AdvertiseRefsRequest {
            repository: Some(header.clone()),
            protocol: None,
            service: "upload-pack".to_string(),
            raw: false,
        })
        .await
        .map_err(|e| format!("AdvertiseRefs: {e}"))?;

    let refs = refs_resp.into_inner().references;
    if refs.is_empty() {
        return Ok(None);
    }

    let wants: Vec<Oid> = refs.iter().filter_map(|r| r.target_oid.clone()).collect();

    let want_count = wants.len();
    let have_count = haves.len();

    tracing::info!(
        relative_path = %relative_path,
        want_count,
        have_count,
        "requesting incremental pack from primary"
    );

    let options = PackObjectsOptions {
        wants,
        haves: haves.to_vec(),
        shallow_revisions: Vec::new(),
        deepen: 0,
        thin_pack: false,
        include_tag: true,
        use_bitmaps: true,
        delta_base_offset: true,
        pathspec: Vec::new(),
    };

    let req = PackObjectsRequest {
        repository: Some(header.clone()),
        options: Some(options),
    };

    let resp = client
        .pack_objects(req)
        .await
        .map_err(|e| format!("PackObjects: {e}"))?;

    let mut stream = resp.into_inner();

    // Create a temporary file for streaming
    let temp_file = temp_dir.join(format!("pack_{}.bundle", std::process::id()));
    let mut file = tokio::fs::File::create(&temp_file)
        .await
        .map_err(|e| format!("create temp file: {e}"))?;

    let mut total_bytes: u64 = 0;
    while let Some(chunk) = stream.next().await {
        match chunk {
            Ok(msg) => {
                total_bytes += msg.data.len() as u64;
                if total_bytes > MAX_PACK_SIZE {
                    let _ = tokio::fs::remove_file(&temp_file).await;
                    return Err(format!(
                        "pack data exceeds maximum size ({}GB)",
                        MAX_PACK_SIZE / (1024 * 1024 * 1024)
                    ));
                }
                file.write_all(&msg.data)
                    .await
                    .map_err(|e| format!("write pack data: {e}"))?;
            }
            Err(e) => {
                let _ = tokio::fs::remove_file(&temp_file).await;
                return Err(format!("pack stream: {e}"));
            }
        }
    }

    // Flush and close the file
    file.flush()
        .await
        .map_err(|e| format!("flush pack file: {e}"))?;
    drop(file);

    tracing::info!(
        relative_path = %relative_path,
        pack_bytes = total_bytes,
        "received pack data from primary"
    );

    Ok(Some(temp_file))
}

fn update_local_ref(repo_path: &Path, ref_name: &str, new_oid: &str) {
    if ref_name.is_empty() || new_oid.is_empty() {
        return;
    }
    match std::process::Command::new("git")
        .args([
            "--git-dir",
            &repo_path.to_string_lossy(),
            "update-ref",
            ref_name,
            new_oid,
        ])
        .output()
    {
        Ok(o) if o.status.success() => {
            tracing::info!(ref_name = %ref_name, new_oid = %new_oid, "ref updated")
        }
        Ok(o) => {
            tracing::error!(ref_name = %ref_name, error = %String::from_utf8_lossy(&o.stderr), "update-ref failed")
        }
        Err(e) => tracing::error!(ref_name = %ref_name, error = %e, "update-ref spawn failed"),
    }
}