1 files changed, 80 insertions, 0 deletions
diff --git a/src/api/document.rs b/src/api/document.rs
new file mode 100644
index 0000000..6c10c38
--- /dev/null
+++ b/src/api/document.rs
@@ -0,0 +1,80 @@
+//! `GET /admin/document`: the local document as Automerge bytes, for backups and as
+//! input to an `import` remake.
+//!
+//! The whole document is saved: history, and protocol data under `_continuum`. Where
+//! it came from is in headers: `X-Continuum-Swarm`, `X-Continuum-Epoch`
+//! (`<generation>:<id hex>`) and `X-Continuum-Heads` (hex, comma-separated).
+
+use axum::{
+    extract::State,
+    http::{HeaderName, HeaderValue, StatusCode, header},
+    response::{IntoResponse, Response},
+};
+use tokio::time::Instant;
+use tracing::{info, warn};
+
+use crate::state::AppState;
+
+pub(crate) async fn get_document(State(state): State<AppState>) -> Response {
+    if !state.is_ready().await {
+        return (StatusCode::SERVICE_UNAVAILABLE, "node is not ready\n").into_response();
+    }
+    let swarm_id = state.swarm_id().await.unwrap_or_default();
+
+    let start = Instant::now();
+    let version = crate::swarm::stats::document_version(&state);
+    let doc = std::sync::Arc::clone(&state.doc);
+    // Both steps take time proportional to the document: off the async threads, and
+    // the lock only for the copy.
+    let saved = tokio::task::spawn_blocking(move || {
+        let (mut copy, epoch) = {
+            let replica = doc.blocking_read();
+            (replica.doc.clone(), replica.epoch)
+        };
+        let heads = copy.get_heads();
+        (copy.save(), heads, epoch)
+    })
+    .await;
+    let (bytes, heads, epoch) = match saved {
+        Ok(saved) => saved,
+        Err(error) => {
+            warn!(error = %error, "Saving the document for export failed");
+            return (StatusCode::INTERNAL_SERVER_ERROR, "saving failed\n").into_response();
+        }
+    };
+    let took = start.elapsed();
+    state
+        .stats
+        .saved_size_measured(bytes.len() as u64, took, version);
+    info!(
+        bytes = bytes.len(),
+        took_ms = took.as_millis() as u64,
+        "Exported the document"
+    );
+
+    let heads = heads
+        .iter()
+        .map(|head| head.to_string())
+        .collect::<Vec<_>>()
+        .join(",");
+    let filename = format!(
+        "attachment; filename=\"continuum-{swarm_id}-{}.automerge\"",
+        epoch.generation
+    );
+    let mut response = bytes.into_response();
+    let headers = response.headers_mut();
+    let mut set = |name: HeaderName, value: String| {
+        if let Ok(value) = HeaderValue::from_str(&value) {
+            headers.insert(name, value);
+        }
+    };
+    set(header::CONTENT_TYPE, "application/octet-stream".to_owned());
+    set(header::CONTENT_DISPOSITION, filename);
+    set(HeaderName::from_static("x-continuum-swarm"), swarm_id);
+    set(
+        HeaderName::from_static("x-continuum-epoch"),
+        format!("{}:{}", epoch.generation, epoch.id_hex()),
+    );
+    set(HeaderName::from_static("x-continuum-heads"), heads);
+    response
+}