Move database logic into submodule and do simple version check

blahd/src/database.rs

@@ -0,0 +1,68 @@
+use std::ops::DerefMut;
+use std::sync::Mutex;
+
+use anyhow::{ensure, Context, Result};
+use rusqlite::{params, Connection, OpenFlags};
+
+use crate::config::DatabaseConfig;
+
+static INIT_SQL: &str = include_str!("../schema.sql");
+
+// Simple and stupid version check for now.
+// `echo -n 'blahd-database-0' | sha256sum | head -c5` || version
+const APPLICATION_ID: i32 = 0xd9e_8400;
+
+#[derive(Debug)]
+pub struct Database {
+    conn: Mutex<Connection>,
+}
+
+impl Database {
+    pub fn open(config: &DatabaseConfig) -> Result<Self> {
+        let mut flags = OpenFlags::SQLITE_OPEN_READ_WRITE | OpenFlags::SQLITE_OPEN_NO_MUTEX;
+        if !config.path.try_exists()? {
+            flags.set(OpenFlags::SQLITE_OPEN_CREATE, config.create);
+        }
+
+        let mut conn = Connection::open_with_flags(&config.path, flags)
+            .context("failed to connect database")?;
+        // Connection-specific pragmas.
+        conn.pragma_update(None, "journal_mode", "WAL")?;
+        conn.pragma_update(None, "foreign_keys", "TRUE")?;
+
+        if conn.query_row(r"SELECT COUNT(*) FROM sqlite_schema", params![], |row| {
+            row.get::<_, u64>(0)
+        })? != 0
+        {
+            let cur_app_id =
+                conn.pragma_query_value(None, "application_id", |row| row.get::<_, i32>(0))?;
+            ensure!(
+                cur_app_id == (APPLICATION_ID),
+                "database is non-empty with a different application_id. \
+                migration is not implemented yet. \
+                got: {cur_app_id:#x}, expect: {APPLICATION_ID:#x} \
+                ",
+            );
+        }
+
+        let txn = conn.transaction()?;
+        txn.execute_batch(INIT_SQL)
+            .context("failed to initialize database")?;
+        txn.pragma_update(None, "application_id", APPLICATION_ID)?;
+        txn.commit()?;
+
+        Ok(Self {
+            conn: Mutex::new(conn),
+        })
+    }
+
+    pub fn get(&self) -> impl DerefMut<Target = Connection> + '_ {
+        self.conn.lock().unwrap()
+    }
+}
+
+#[test]
+fn init_sql_valid() {
+    let conn = Connection::open_in_memory().unwrap();
+    conn.execute_batch(INIT_SQL).unwrap();
+}