chore: filesystem layout helpers

Author: radim

crates/dry_run_cli/src/main.rs

@@ -966,14 +966,8 @@ fn write_snapshot_export(
     key: &SnapshotKey,
     snap: &dry_run_core::SchemaSnapshot,
 ) -> anyhow::Result<PathBuf> {
-    let path = out_root
-        .join(&key.project_id.0)
-        .join(&key.database_id.0)
-        .join(format!(
-            "{}-{}.json.zst",
-            snap.timestamp.format("%Y%m%dT%H%M%SZ"),
-            snap.content_hash,
-        ));
+    let path =
+        dry_run_core::history::snapshot_path(out_root, key, snap.timestamp, &snap.content_hash);
     if let Some(parent) = path.parent() {
         std::fs::create_dir_all(parent)?;
     }

crates/dry_run_core/src/history/filesystem_layout.rs

@@ -0,0 +1,34 @@
+use crate::history::SnapshotKey;
+use chrono::{DateTime, NaiveDateTime, TimeZone, Utc};
+use std::path::{Path, PathBuf};
+
+pub const SNAPSHOT_EXTENSION: &str = "json.zst";
+
+const TS_FORMAT: &str = "%Y%m%dT%H%M%SZ";
+
+#[must_use]
+pub fn snapshot_path(
+    root: &Path,
+    key: &SnapshotKey,
+    timestamp: DateTime<Utc>,
+    content_hash: &str,
+) -> PathBuf {
+    root.join(&key.project_id.0)
+        .join(&key.database_id.0)
+        .join(format!(
+            "{}-{}.{}",
+            timestamp.format(TS_FORMAT),
+            content_hash,
+            SNAPSHOT_EXTENSION,
+        ))
+}
+
+#[must_use]
+pub fn parse_snapshot_filename(name: &str) -> Option<(DateTime<Utc>, String)> {
+    let stem = name.strip_suffix(&format!(".{SNAPSHOT_EXTENSION}"))?;
+    let (ts_str, hash) = stem.split_once('-')?;
+    let naive = NaiveDateTime::parse_from_str(ts_str, TS_FORMAT).ok()?;
+    let ts = Utc.from_utc_datetime(&naive);
+
+    Some((ts, hash.to_string()))
+}

crates/dry_run_core/src/history/mod.rs

@@ -1,6 +1,8 @@
+pub mod filesystem_layout;
 mod snapshot_store;
 mod store;
 
+pub use filesystem_layout::{SNAPSHOT_EXTENSION, parse_snapshot_filename, snapshot_path};
 pub use snapshot_store::{
     DatabaseId, ProjectId, PutOutcome, SnapshotKey, SnapshotRef, SnapshotStore, TimeRange,
 };