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use std::io::Result;
use std::ops::{Deref, DerefMut};
use std::path::Path;

#[doc(hidden)]
pub mod prost_build {
    pub use prost_build::*;
}

mod service_generator;

pub use service_generator::TtrpcServiceGenerator;

/// Compile `.proto` files into Rust files during a Cargo build.
///
/// The generated `.rs` files are written to the Cargo `OUT_DIR` directory, suitable for use with
/// the [include!][1] macro. See the [Cargo `build.rs` code generation][2] example for more info.
///
/// This function should be called in a project's `build.rs`.
///
/// # Arguments
///
/// **`protos`** - Paths to `.proto` files to compile. Any transitively [imported][3] `.proto`
/// files are automatically be included.
///
/// **`includes`** - Paths to directories in which to search for imports. Directories are searched
/// in order. The `.proto` files passed in **`protos`** must be found in one of the provided
/// include directories.
///
/// # Errors
///
/// This function can fail for a number of reasons:
///
///   - Failure to locate or download `protoc`.
///   - Failure to parse the `.proto`s.
///   - Failure to locate an imported `.proto`.
///   - Failure to compile a `.proto` without a [package specifier][4].
///
/// It's expected that this function call be `unwrap`ed in a `build.rs`; there is typically no
/// reason to gracefully recover from errors during a build.
///
/// # Example `build.rs`
///
/// ```rust,no_run
/// # use std::io::Result;
/// fn main() -> Result<()> {
///   trapeze_codegen::compile_protos(&["src/frontend.proto", "src/backend.proto"], &["src"])?;
///   Ok(())
/// }
/// ```
///
/// [1]: https://doc.rust-lang.org/std/macro.include.html
/// [2]: http://doc.crates.io/build-script.html#case-study-code-generation
/// [3]: https://developers.google.com/protocol-buffers/docs/proto3#importing-definitions
/// [4]: https://developers.google.com/protocol-buffers/docs/proto#packages
pub fn compile_protos(protos: &[impl AsRef<Path>], includes: &[impl AsRef<Path>]) -> Result<()> {
    Config::new().compile_protos(protos, includes)
}

/// Configuration options for Protobuf code generation.
///
/// This configuration builder can be used to set non-default code generation options.
pub struct Config(prost_build::Config);

impl Config {
    /// Creates a new code generator configuration with default options.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }
}

impl Default for Config {
    fn default() -> Self {
        let mut cfg = prost_build::Config::new();
        cfg.service_generator(Box::new(TtrpcServiceGenerator));
        Self(cfg)
    }
}

impl Deref for Config {
    type Target = prost_build::Config;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for Config {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}