aconfig: add create-device-config-defaults command

DeviceConfig is the backend for READ_WRITE flags.

Add a new command "create-device-config-defaults" to create a file that
DeviceConfig will read to pre-populate its data store on first init.

This will be used to quickly switch flag values during CI tests:
rebuilding and reflashing a device would have the same effect, but would
be costlier. This feature is not expected to be used outside CI tests.

Note: because DeviceConfig only works with READ_WRITE flags, the
generated file excludes READ_ONLY flags.

Bug: 285468565
Test: atest aconfig.test
Change-Id: I4caff1a10647b8da0ce4e3615678993a957a92dd
diff --git a/tools/aconfig/src/commands.rs b/tools/aconfig/src/commands.rs
index df1a17a..d5e47da 100644
--- a/tools/aconfig/src/commands.rs
+++ b/tools/aconfig/src/commands.rs
@@ -22,8 +22,8 @@
 use std::io::Read;
 use std::path::PathBuf;
 
-use crate::aconfig::{FlagDeclarations, FlagValue};
-use crate::cache::{Cache, CacheBuilder};
+use crate::aconfig::{FlagDeclarations, FlagState, FlagValue, Permission};
+use crate::cache::{Cache, CacheBuilder, Item};
 use crate::codegen_cpp::generate_cpp_code;
 use crate::codegen_java::generate_java_code;
 use crate::codegen_rust::generate_rust_code;
@@ -105,6 +105,24 @@
     generate_rust_code(&cache)
 }
 
+pub fn create_device_config_defaults(caches: Vec<Cache>) -> Result<Vec<u8>> {
+    let mut output = Vec::new();
+    for item in sort_and_iter_items(caches).filter(|item| item.permission == Permission::ReadWrite)
+    {
+        let line = format!(
+            "{}/{}:{}\n",
+            item.namespace,
+            item.name,
+            match item.state {
+                FlagState::Enabled => "enabled",
+                FlagState::Disabled => "disabled",
+            }
+        );
+        output.extend_from_slice(line.as_bytes());
+    }
+    Ok(output)
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, ValueEnum)]
 pub enum DumpFormat {
     Text,
@@ -112,29 +130,26 @@
     Protobuf,
 }
 
-pub fn dump_cache(mut caches: Vec<Cache>, format: DumpFormat) -> Result<Vec<u8>> {
+pub fn dump_cache(caches: Vec<Cache>, format: DumpFormat) -> Result<Vec<u8>> {
     let mut output = Vec::new();
-    caches.sort_by_cached_key(|cache| cache.namespace().to_string());
-    for cache in caches.into_iter() {
-        match format {
-            DumpFormat::Text => {
-                let mut lines = vec![];
-                for item in cache.iter() {
-                    lines.push(format!(
-                        "{}/{}: {:?} {:?}\n",
-                        item.namespace, item.name, item.state, item.permission
-                    ));
-                }
-                output.append(&mut lines.concat().into());
+    match format {
+        DumpFormat::Text => {
+            for item in sort_and_iter_items(caches) {
+                let line = format!(
+                    "{}/{}: {:?} {:?}\n",
+                    item.namespace, item.name, item.state, item.permission
+                );
+                output.extend_from_slice(line.as_bytes());
             }
-            DumpFormat::Debug => {
-                let mut lines = vec![];
-                for item in cache.iter() {
-                    lines.push(format!("{:#?}\n", item));
-                }
-                output.append(&mut lines.concat().into());
+        }
+        DumpFormat::Debug => {
+            for item in sort_and_iter_items(caches) {
+                let line = format!("{:#?}\n", item);
+                output.extend_from_slice(line.as_bytes());
             }
-            DumpFormat::Protobuf => {
+        }
+        DumpFormat::Protobuf => {
+            for cache in sort_and_iter_caches(caches) {
                 let parsed_flags: ProtoParsedFlags = cache.into();
                 parsed_flags.write_to_vec(&mut output)?;
             }
@@ -143,6 +158,15 @@
     Ok(output)
 }
 
+fn sort_and_iter_items(caches: Vec<Cache>) -> impl Iterator<Item = Item> {
+    sort_and_iter_caches(caches).flat_map(|cache| cache.into_iter())
+}
+
+fn sort_and_iter_caches(mut caches: Vec<Cache>) -> impl Iterator<Item = Cache> {
+    caches.sort_by_cached_key(|cache| cache.namespace().to_string());
+    caches.into_iter()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -203,6 +227,14 @@
     }
 
     #[test]
+    fn test_create_device_config_defaults() {
+        let caches = vec![crate::test::create_cache()];
+        let bytes = create_device_config_defaults(caches).unwrap();
+        let text = std::str::from_utf8(&bytes).unwrap();
+        assert_eq!("test/disabled_rw:disabled\ntest/enabled_rw:enabled\n", text);
+    }
+
+    #[test]
     fn test_dump_text_format() {
         let caches = vec![create_test_cache_ns1()];
         let bytes = dump_cache(caches, DumpFormat::Text).unwrap();