move store helpers to store module

1 files changed, 93 insertions, 3 deletions

diff --git a/src/api/store.rs b/src/api/store.rs
index 0b0a40f..bc43824 100644
--- a/src/api/store.rs
+++ b/src/api/store.rs
@@ -9,17 +9,19 @@ use axum::{
     extract::{Path, Query, RawQuery, State},
     http::{
         HeaderMap, HeaderValue, StatusCode,
-        header::{ACCEPT, CONTENT_TYPE, LOCATION},
+        header::{ACCEPT, CONTENT_TYPE, ETAG, LOCATION},
     },
     response::{IntoResponse, Response},
 };
 use serde::Deserialize;
 use serde_json::Value as JsonValue;
+use sha2::{Digest, Sha256};
 use tokio::sync::broadcast;
-use tracing::{debug, error, instrument};
+use tracing::{debug, error, instrument, warn};
 
 use super::auth::AuthenticatedUser;
-use super::{parse_key_path, parse_write_path, response_for_value, store_status};
+use super::store_status;
+use crate::document::meta;
 use crate::document::store::{self, StoreError, paths_related};
 use crate::state::{AppState, ReadSource};
 
@@ -220,6 +222,94 @@ pub(crate) async fn put_store_entry(
     response_for_value(&value, headers.get(ACCEPT))
 }
 
+fn etag_for(bytes: &[u8]) -> String {
+    let digest = Sha256::digest(bytes);
+    let hex = digest
+        .iter()
+        .map(|byte| format!("{byte:02x}"))
+        .collect::<String>();
+
+    format!("\"{hex}\"")
+}
+
+fn parse_key_path(key: &str) -> Result<Vec<String>, StatusCode> {
+    let segments: Vec<String> = key.split('/').map(str::to_owned).collect();
+
+    if segments.is_empty() || segments.iter().any(|segment| segment.is_empty()) {
+        return Err(StatusCode::BAD_REQUEST);
+    }
+
+    Ok(segments)
+}
+
+/// A path for a write. Protocol data (`_continuum`: remake records, members, forget
+/// records, epoch metadata) is what every node acts on, so a write there acts on the
+/// whole swarm: only users listed in `--protocol-writers` may, and each such write is
+/// logged. Epoch metadata (and `_continuum` as a whole, which contains it) is never
+/// writable: the protocol reads it at the snapshot change, so an edit only misleads
+/// whoever reads it later. `403` otherwise.
+fn parse_write_path(
+    state: &AppState,
+    user: &AuthenticatedUser,
+    key: &str,
+    method: &str,
+) -> Result<Vec<String>, StatusCode> {
+    let path = parse_key_path(key)?;
+    if !meta::is_protocol(&path) {
+        return Ok(path);
+    }
+    // `_continuum` itself, epoch metadata and the swarm ID: nobody.
+    let fixed = path.len() < 2 || path[1] == meta::EPOCHS || path[1] == meta::SWARM;
+    if fixed || !state.protocol_writers.contains(&user.0) {
+        warn!(user = %user.0, method, path = %key, "Refused a write to protocol data");
+        return Err(StatusCode::FORBIDDEN);
+    }
+    warn!(user = %user.0, method, path = %key, "Protocol data written through the store API; this acts on the whole swarm");
+    Ok(path)
+}
+
+fn response_for_value(
+    value: &JsonValue,
+    accept: Option<&HeaderValue>,
+) -> Result<Response, StatusCode> {
+    let wants_text = accept
+        .and_then(|value| value.to_str().ok())
+        .is_some_and(|value| {
+            value
+                .split(',')
+                .any(|item| item.trim().starts_with("text/plain"))
+        });
+
+    let (content_type, body) = if wants_text {
+        let body = match value {
+            JsonValue::String(value) => value.clone(),
+            other => serde_json::to_string(other).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
+        };
+
+        ("text/plain; charset=utf-8", body)
+    } else {
+        (
+            "application/json",
+            serde_json::to_string(value).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
+        )
+    };
+
+    let etag = etag_for(body.as_bytes());
+
+    let mut response = body.into_response();
+
+    response
+        .headers_mut()
+        .insert(CONTENT_TYPE, HeaderValue::from_static(content_type));
+
+    response.headers_mut().insert(
+        ETAG,
+        HeaderValue::from_str(&etag).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
+    );
+
+    Ok(response)
+}
+
 /// A write's body as a value: JSON (the default), or text as a string.
 fn body_value(headers: &HeaderMap, body: &Bytes) -> Result<JsonValue, StatusCode> {
     let content_type = headers