aconfig: move codegen into separate module

Consolidate the code generation sources into its own module. This is
done in preparation for when support for the new flag storage will be
added, which should also be placed in a separate module.

Bug: N/A
Test: atest aconfig.test aconfig.test.java
Change-Id: I8246729218ec60f2af4568c460e98329665a89fa

tools/aconfig/src/codegen/mod.rs

@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+pub mod cpp;
+pub mod java;
+pub mod rust;
+
+use anyhow::{ensure, Result};
+
+pub fn is_valid_name_ident(s: &str) -> bool {
+    // Identifiers must match [a-z][a-z0-9_]*, except consecutive underscores are not allowed
+    if s.contains("__") {
+        return false;
+    }
+    let mut chars = s.chars();
+    let Some(first) = chars.next() else {
+        return false;
+    };
+    if !first.is_ascii_lowercase() {
+        return false;
+    }
+    chars.all(|ch| ch.is_ascii_lowercase() || ch.is_ascii_digit() || ch == '_')
+}
+
+pub fn is_valid_package_ident(s: &str) -> bool {
+    if !s.contains('.') {
+        return false;
+    }
+    s.split('.').all(is_valid_name_ident)
+}
+
+pub fn is_valid_container_ident(s: &str) -> bool {
+    is_valid_name_ident(s) || s.split('.').all(is_valid_name_ident)
+}
+
+pub fn create_device_config_ident(package: &str, flag_name: &str) -> Result<String> {
+    ensure!(is_valid_package_ident(package), "bad package");
+    ensure!(is_valid_name_ident(flag_name), "bad flag name");
+    Ok(format!("{}.{}", package, flag_name))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_is_valid_name_ident() {
+        assert!(is_valid_name_ident("foo"));
+        assert!(is_valid_name_ident("foo_bar_123"));
+        assert!(is_valid_name_ident("foo_"));
+
+        assert!(!is_valid_name_ident(""));
+        assert!(!is_valid_name_ident("123_foo"));
+        assert!(!is_valid_name_ident("foo-bar"));
+        assert!(!is_valid_name_ident("foo-b\u{00e5}r"));
+        assert!(!is_valid_name_ident("foo__bar"));
+        assert!(!is_valid_name_ident("_foo"));
+    }
+
+    #[test]
+    fn test_is_valid_package_ident() {
+        assert!(is_valid_package_ident("foo.bar"));
+        assert!(is_valid_package_ident("foo.bar_baz"));
+        assert!(is_valid_package_ident("foo.bar.a123"));
+
+        assert!(!is_valid_package_ident("foo_bar_123"));
+        assert!(!is_valid_package_ident("foo"));
+        assert!(!is_valid_package_ident("foo._bar"));
+        assert!(!is_valid_package_ident(""));
+        assert!(!is_valid_package_ident("123_foo"));
+        assert!(!is_valid_package_ident("foo-bar"));
+        assert!(!is_valid_package_ident("foo-b\u{00e5}r"));
+        assert!(!is_valid_package_ident("foo.bar.123"));
+        assert!(!is_valid_package_ident(".foo.bar"));
+        assert!(!is_valid_package_ident("foo.bar."));
+        assert!(!is_valid_package_ident("."));
+        assert!(!is_valid_package_ident(".."));
+        assert!(!is_valid_package_ident("foo..bar"));
+        assert!(!is_valid_package_ident("foo.__bar"));
+    }
+
+    #[test]
+    fn test_is_valid_container_ident() {
+        assert!(is_valid_container_ident("foo.bar"));
+        assert!(is_valid_container_ident("foo.bar_baz"));
+        assert!(is_valid_container_ident("foo.bar.a123"));
+        assert!(is_valid_container_ident("foo"));
+        assert!(is_valid_container_ident("foo_bar_123"));
+
+        assert!(!is_valid_container_ident(""));
+        assert!(!is_valid_container_ident("foo._bar"));
+        assert!(!is_valid_container_ident("_foo"));
+        assert!(!is_valid_container_ident("123_foo"));
+        assert!(!is_valid_container_ident("foo-bar"));
+        assert!(!is_valid_container_ident("foo-b\u{00e5}r"));
+        assert!(!is_valid_container_ident("foo.bar.123"));
+        assert!(!is_valid_container_ident(".foo.bar"));
+        assert!(!is_valid_container_ident("foo.bar."));
+        assert!(!is_valid_container_ident("."));
+        assert!(!is_valid_container_ident(".."));
+        assert!(!is_valid_container_ident("foo..bar"));
+        assert!(!is_valid_container_ident("foo.__bar"));
+    }
+
+    #[test]
+    fn test_create_device_config_ident() {
+        assert_eq!(
+            "com.foo.bar.some_flag",
+            create_device_config_ident("com.foo.bar", "some_flag").unwrap()
+        );
+    }
+}