- Rename index.rs to database.rs for clarity in purpose

- Update references in `scan.rs` to the renamed module
- Add `cargo clippy` step to CI for linting

src/database.rs

@@ -0,0 +1,77 @@
+pub mod index {
+  use blake3::Hasher;
+  use rusqlite::{params, Connection, OptionalExtension};
+  use std::fs;
+  use std::path::Path;
+  use std::time::{SystemTime, UNIX_EPOCH};
+
+  /// Schema: stores digest, file modification time (secs since epoch) and
+  /// last time we *fully* scanned the file.
+  const SCHEMA: &str = r#"
+        CREATE TABLE IF NOT EXISTS files (
+            path TEXT PRIMARY KEY,
+            hash BLOB NOT NULL,
+            mtime INTEGER NOT NULL,
+            scanned_at INTEGER NOT NULL
+        );"#;
+
+  pub(crate) struct Indexer {
+    conn: Connection,
+  }
+
+  impl Indexer {
+    pub fn new(database_path: &Path) -> Result<Self, Box<dyn std::error::Error>> {
+      let conn = Connection::open(database_path)?;
+      conn.execute_batch(SCHEMA)?;
+      Ok(Self { conn })
+    }
+
+    /// Returns `true` if the caller should analyze the file, i.e., we have
+    /// never seen it or something changed (mtime or content hash).
+    pub fn should_scan(&self, path: &Path) -> Result<bool, Box<dyn std::error::Error>> {
+      let meta = fs::metadata(path)?;
+      let mtime = meta.modified()?.duration_since(UNIX_EPOCH)?.as_secs() as i64;
+
+      let digest = Self::digest_file(path)?;
+
+      let row: Option<(Vec<u8>, i64)> = self
+        .conn
+        .query_row(
+          "SELECT hash, mtime FROM files WHERE path = ?1",
+          params![path.to_string_lossy()],
+          |r| Ok((r.get(0)?, r.get(1)?)),
+        )
+        .optional()?;
+
+      match row {
+        Some((stored_hash, stored_mtime)) => {
+          Ok(stored_hash != digest || stored_mtime != mtime)
+        }
+        None => Ok(true),
+      }
+    }
+
+    /// Persist a fresh scan result.
+    pub fn record_scan(&self, path: &Path) -> Result<(), Box<dyn std::error::Error>> {
+      let meta = fs::metadata(path)?;
+      let mtime = meta.modified()?.duration_since(UNIX_EPOCH)?.as_secs() as i64;
+      let scanned_at = SystemTime::now()
+        .duration_since(UNIX_EPOCH)?
+        .as_secs() as i64;
+      let digest = Self::digest_file(path)?;
+
+      self.conn.execute(
+        "REPLACE INTO files (path, hash, mtime, scanned_at) VALUES (?1, ?2, ?3, ?4)",
+        params![path.to_string_lossy(), digest, mtime, scanned_at],
+      )?;
+      Ok(())
+    }
+
+    fn digest_file(path: &Path) -> Result<Vec<u8>, Box<dyn std::error::Error>> {
+      let mut hasher = Hasher::new();
+      let mut file = fs::File::open(path)?;
+      std::io::copy(&mut file, &mut hasher)?;
+      Ok(hasher.finalize().as_bytes().to_vec())
+    }
+  }
+}