aconfig: Add codegen for java

Add codegen for java skeleton

Bug: 279485059
Test: atest aconfig.test
Change-Id: Ia0481cec9c2e137e88e9a77d1b82412529b64adc
diff --git a/tools/aconfig/Android.bp b/tools/aconfig/Android.bp
index e762f33..9617e0e 100644
--- a/tools/aconfig/Android.bp
+++ b/tools/aconfig/Android.bp
@@ -23,6 +23,7 @@
         "libprotobuf",
         "libserde",
         "libserde_json",
+        "libtinytemplate",
     ],
 }
 
diff --git a/tools/aconfig/Cargo.toml b/tools/aconfig/Cargo.toml
index b439858..8517dd2 100644
--- a/tools/aconfig/Cargo.toml
+++ b/tools/aconfig/Cargo.toml
@@ -14,6 +14,7 @@
 protobuf = "3.2.0"
 serde = { version = "1.0.152", features = ["derive"] }
 serde_json = "1.0.93"
+tinytemplate = "1.2.1"
 
 [build-dependencies]
 protobuf-codegen = "3.2.0"
diff --git a/tools/aconfig/src/codegen_java.rs b/tools/aconfig/src/codegen_java.rs
new file mode 100644
index 0000000..9d52cce
--- /dev/null
+++ b/tools/aconfig/src/codegen_java.rs
@@ -0,0 +1,142 @@
+/*
+ * 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.
+ */
+
+use anyhow::Result;
+use serde::Serialize;
+use tinytemplate::TinyTemplate;
+
+use crate::aconfig::{FlagState, Permission};
+use crate::cache::{Cache, Item};
+
+pub struct GeneratedFile {
+    pub file_content: String,
+    pub file_name: String,
+}
+
+pub fn generate_java_code(cache: &Cache) -> Result<GeneratedFile> {
+    let class_elements: Vec<ClassElement> = cache.iter().map(create_class_element).collect();
+    let readwrite = class_elements.iter().any(|item| item.readwrite);
+    let namespace = uppercase_first_letter(
+        cache.iter().find(|item| !item.namespace.is_empty()).unwrap().namespace.as_str(),
+    );
+    let context = Context { namespace: namespace.clone(), readwrite, class_elements };
+    let mut template = TinyTemplate::new();
+    template.add_template("java_code_gen", include_str!("../templates/java.template"))?;
+    let file_content = template.render("java_code_gen", &context)?;
+    Ok(GeneratedFile { file_content, file_name: format!("{}.java", namespace) })
+}
+
+#[derive(Serialize)]
+struct Context {
+    pub namespace: String,
+    pub readwrite: bool,
+    pub class_elements: Vec<ClassElement>,
+}
+
+#[derive(Serialize)]
+struct ClassElement {
+    pub method_name: String,
+    pub readwrite: bool,
+    pub default_value: String,
+    pub feature_name: String,
+    pub flag_name: String,
+}
+
+fn create_class_element(item: &Item) -> ClassElement {
+    ClassElement {
+        method_name: item.name.clone(),
+        readwrite: item.permission == Permission::ReadWrite,
+        default_value: if item.state == FlagState::Enabled {
+            "true".to_string()
+        } else {
+            "false".to_string()
+        },
+        feature_name: item.name.clone(),
+        flag_name: item.name.clone(),
+    }
+}
+
+fn uppercase_first_letter(s: &str) -> String {
+    s.chars()
+        .enumerate()
+        .map(
+            |(index, ch)| {
+                if index == 0 {
+                    ch.to_ascii_uppercase()
+                } else {
+                    ch.to_ascii_lowercase()
+                }
+            },
+        )
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::aconfig::{Flag, Value};
+    use crate::commands::Source;
+
+    #[test]
+    fn test_generate_java_code() {
+        let namespace = "TeSTFlaG";
+        let mut cache = Cache::new(1, namespace.to_string());
+        cache
+            .add_flag(
+                Source::File("test.txt".to_string()),
+                Flag {
+                    name: "test".to_string(),
+                    description: "buildtime enable".to_string(),
+                    values: vec![Value::default(FlagState::Enabled, Permission::ReadOnly)],
+                },
+            )
+            .unwrap();
+        cache
+            .add_flag(
+                Source::File("test2.txt".to_string()),
+                Flag {
+                    name: "test2".to_string(),
+                    description: "runtime disable".to_string(),
+                    values: vec![Value::default(FlagState::Disabled, Permission::ReadWrite)],
+                },
+            )
+            .unwrap();
+        let expect_content = "package com.android.aconfig;
+
+        import android.provider.DeviceConfig;
+
+        public final class Testflag {
+
+            public static boolean test() {
+                return true;
+            }
+
+            public static boolean test2() {
+                return DeviceConfig.getBoolean(
+                    \"Testflag\",
+                    \"test2__test2\",
+                    false
+                );
+            }
+
+        }
+        ";
+        let expected_file_name = format!("{}.java", uppercase_first_letter(namespace));
+        let generated_file = generate_java_code(&cache).unwrap();
+        assert_eq!(expected_file_name, generated_file.file_name);
+        assert_eq!(expect_content.replace(' ', ""), generated_file.file_content.replace(' ', ""));
+    }
+}
diff --git a/tools/aconfig/src/commands.rs b/tools/aconfig/src/commands.rs
index 2c80a4a..1487e72 100644
--- a/tools/aconfig/src/commands.rs
+++ b/tools/aconfig/src/commands.rs
@@ -23,6 +23,7 @@
 
 use crate::aconfig::{Namespace, Override};
 use crate::cache::Cache;
+use crate::codegen_java::{generate_java_code, GeneratedFile};
 use crate::protos::ProtoParsedFlags;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
@@ -84,6 +85,10 @@
     Ok(cache)
 }
 
+pub fn generate_code(cache: &Cache) -> Result<GeneratedFile> {
+    generate_java_code(cache)
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, ValueEnum)]
 pub enum Format {
     Text,
diff --git a/tools/aconfig/src/main.rs b/tools/aconfig/src/main.rs
index f253735..f29186a 100644
--- a/tools/aconfig/src/main.rs
+++ b/tools/aconfig/src/main.rs
@@ -24,6 +24,7 @@
 
 mod aconfig;
 mod cache;
+mod codegen_java;
 mod commands;
 mod protos;
 
@@ -47,6 +48,11 @@
                 .arg(Arg::new("cache").long("cache").required(true)),
         )
         .subcommand(
+            Command::new("create-java-lib")
+                .arg(Arg::new("cache").long("cache").required(true))
+                .arg(Arg::new("out").long("out").required(true)),
+        )
+        .subcommand(
             Command::new("dump")
                 .arg(Arg::new("cache").long("cache").required(true))
                 .arg(
@@ -81,6 +87,17 @@
             let file = fs::File::create(path)?;
             cache.write_to_writer(file)?;
         }
+        Some(("create-java-lib", sub_matches)) => {
+            let path = sub_matches.get_one::<String>("cache").unwrap();
+            let file = fs::File::open(path)?;
+            let cache = Cache::read_from_reader(file)?;
+            let out = sub_matches.get_one::<String>("out").unwrap();
+            let generated_file = commands::generate_code(&cache).unwrap();
+            fs::write(
+                format!("{}/{}", out, generated_file.file_name),
+                generated_file.file_content,
+            )?;
+        }
         Some(("dump", sub_matches)) => {
             let path = sub_matches.get_one::<String>("cache").unwrap();
             let file = fs::File::open(path)?;
diff --git a/tools/aconfig/templates/java.template b/tools/aconfig/templates/java.template
new file mode 100644
index 0000000..3854579
--- /dev/null
+++ b/tools/aconfig/templates/java.template
@@ -0,0 +1,19 @@
+package com.android.aconfig;
+{{ if readwrite }}
+import android.provider.DeviceConfig;
+{{ endif }}
+public final class {namespace} \{
+    {{ for item in class_elements}}
+    public static boolean {item.method_name}() \{
+        {{ if item.readwrite- }}
+        return DeviceConfig.getBoolean(
+            "{namespace}",
+            "{item.feature_name}__{item.flag_name}",
+            {item.default_value}
+        ); 
+        {{ -else- }}
+        return {item.default_value};
+        {{ -endif }}
+    }
+    {{ endfor }}
+}