expose :mode from connect/1 (#212)

Co-authored-by: Greg Rychlewski <grychle@LLL7WPM64V5M.ngco.com>

Author: greg-rychlewski

lib/exqlite/connection.ex

@@ -82,6 +82,9 @@ defmodule Exqlite.Connection do
 
     * `:database` - The path to the database. In memory is allowed. You can use
       `:memory` or `":memory:"` to designate that.
+    * `:mode` - use `:readwrite` to open the database for reading and writing
+      or `:readonly` to open it in read-only mode. `:readwrite` will also create
+      the database if it doesn't already exist. Defaults to `:readwrite`.
     * `:journal_mode` - Sets the journal mode for the sqlite connection. Can be
       one of the following `:delete`, `:truncate`, `:persist`, `:memory`,
       `:wal`, or `:off`. Defaults to `:delete`. It is recommended that you use
@@ -450,7 +453,7 @@ defmodule Exqlite.Connection do
 
   defp do_connect(path, options) do
     with :ok <- mkdir_p(path),
-         {:ok, db} <- Sqlite3.open(path),
+         {:ok, db} <- Sqlite3.open(path, options),
          :ok <- set_key(db, options),
          :ok <- set_journal_mode(db, options),
          :ok <- set_temp_store(db, options),

test/exqlite/connection_test.exs

@@ -72,6 +72,31 @@ defmodule Exqlite.ConnectionTest do
 
       File.rm(path)
     end
+
+    test "setting connection mode" do
+      path = Temp.path!()
+
+      # Create readwrite connection
+      {:ok, rw_state} = Connection.connect(database: path)
+      create_table_query = "create table test (id integer primary key, stuff text)"
+      :ok = Sqlite3.execute(rw_state.db, create_table_query)
+
+      insert_value_query = "insert into test (stuff) values ('This is a test')"
+      :ok = Sqlite3.execute(rw_state.db, insert_value_query)
+
+      # Read from database with a readonly connection
+      {:ok, ro_state} = Connection.connect(database: path, mode: :readonly)
+
+      select_query = "select id, stuff from test order by id asc"
+      {:ok, statement} = Sqlite3.prepare(ro_state.db, select_query)
+      {:row, columns} = Sqlite3.step(ro_state.db, statement)
+
+      assert [1, "This is a test"] == columns
+
+      # Readonly connection cannot insert
+      assert {:error, "attempt to write a readonly database"} ==
+               Sqlite3.execute(ro_state.db, insert_value_query)
+    end
   end
 
   defp get_pragma(db, pragma_name) do