// Copyright 2019 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use std::env;
use std::error::Error;
use std::fs::File;
use std::io::Write;
use std::path::PathBuf;

type Result<T> = std::result::Result<T, Box<dyn Error>>;

struct Proto {
    // Where to find protos during builds within cros_sdk. Relative to $SYSROOT
    // environment variable set by emerge builds.
    dir_relative_to_sysroot: &'static str,

    // Where to find protos during "cargo build" in a local developer
    // environment. Relative to the platform/crosvm/protos directory.
    dir_relative_to_us: &'static str,

    // *.proto file expected to exist in both of the above directories.
    proto_file_name: &'static str,

    // Code generated by proto compiler will be exported under
    // protos::$module_name.
    name_for_module: &'static str,
}

static PROTOS: &[Proto] = &[Proto {
    dir_relative_to_sysroot: "usr/include/chromeos/dbus/trunks",
    dir_relative_to_us: "../../../platform2/trunks",
    proto_file_name: "interface.proto",
    name_for_module: "trunks",
}];

fn paths_to_strs(paths: &[PathBuf]) -> Vec<&str> {
    paths
        .iter()
        .map(|p| p.as_os_str().to_str().unwrap())
        .collect()
}

fn main() -> Result<()> {
    let out_dir = env::var("OUT_DIR")?;
    let sysroot = env::var_os("SYSROOT");

    // Write out a Rust module that imports the modules generated by protoc.
    let protos_rs = PathBuf::from(&out_dir).join("protos.rs");
    let mut out = File::create(protos_rs)?;

    let mut input_files = Vec::new();
    let mut include_dirs = Vec::new();

    for proto in PROTOS {
        let dir = match &sysroot {
            Some(dir) => PathBuf::from(dir).join(proto.dir_relative_to_sysroot),
            None => PathBuf::from(proto.dir_relative_to_us),
        };

        input_files.push(dir.join(proto.proto_file_name));
        include_dirs.push(dir);

        let generated_module = proto.proto_file_name.replace(".proto", "");
        writeln!(out, "#[path = \"{}/{}.rs\"]", out_dir, generated_module)?;
        writeln!(out, "pub mod {};", proto.name_for_module)?;
    }

    // Invoke proto compiler.
    protoc_rust::run(protoc_rust::Args {
        out_dir: &out_dir,
        input: &paths_to_strs(&input_files),
        includes: &paths_to_strs(&include_dirs),
        ..Default::default()
    })?;

    Ok(())
}