Add original database code

src/db/mod.rs

@@ -0,0 +1,54 @@
+use diesel::prelude::*;
+use diesel_migrations::{embed_migrations, EmbeddedMigrations, MigrationHarness};
+use log::info;
+
+pub use diesel::SqliteConnection;
+
+pub mod ensembles;
+pub use ensembles::*;
+
+pub mod error;
+pub use error::*;
+
+pub mod instruments;
+pub use instruments::*;
+
+pub mod medium;
+pub use medium::*;
+
+pub mod persons;
+pub use persons::*;
+
+pub mod recordings;
+pub use recordings::*;
+
+pub mod works;
+pub use works::*;
+
+mod schema;
+
+// This makes the SQL migration scripts accessible from the code.
+const MIGRATIONS: EmbeddedMigrations = embed_migrations!();
+
+/// Connect to a Musicus database running migrations if necessary.
+pub fn connect(file_name: &str) -> Result<SqliteConnection> {
+    info!("Opening database file '{}'", file_name);
+    let mut connection = SqliteConnection::establish(file_name)?;
+    diesel::sql_query("PRAGMA foreign_keys = ON").execute(&mut connection)?;
+
+    info!("Running migrations if necessary");
+    connection.run_pending_migrations(MIGRATIONS)?;
+
+    Ok(connection)
+}
+
+/// Generate a random string suitable as an item ID.
+pub fn generate_id() -> String {
+    uuid::Uuid::new_v4().simple().to_string()
+}
+
+/// Defer all foreign keys for the next transaction.
+fn defer_foreign_keys(connection: &mut SqliteConnection) -> Result<()> {
+    diesel::sql_query("PRAGMA defer_foreign_keys = ON").execute(connection)?;
+    Ok(())
+}