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use std::error::Error;
use std::fmt;
use std::path::Path;
use std::process::Command;

#[derive(Debug)]
struct BisonErr {
    message: String,
    code: Option<i32>,
}

impl fmt::Display for BisonErr {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "BisonErr: {} ({:#?})", self.message, self.code)
    }
}

impl Error for BisonErr {}

pub fn process_bison_file(filepath: &Path) -> Result<(), Box<dyn Error>> {
    let input = filepath;
    let output = filepath.with_extension("rs");

    println!("cargo:rerun-if-changed={}", input.to_str().unwrap());
    let bison_root_dir = Path::new(file!())
        .parent()
        .unwrap()
        .parent()
        .unwrap()
        .join("bison");

    println!(
        "cargo:rerun-if-changed={}",
        bison_root_dir.join("c-like.m4").to_str().unwrap()
    );
    println!(
        "cargo:rerun-if-changed={}",
        bison_root_dir.join("lalr1-rust.m4").to_str().unwrap()
    );
    println!(
        "cargo:rerun-if-changed={}",
        bison_root_dir.join("main.m4").to_str().unwrap()
    );
    println!(
        "cargo:rerun-if-changed={}",
        bison_root_dir.join("rust.m4").to_str().unwrap()
    );

    let bison_root_file = bison_root_dir.join("main.m4");

    let args = &[
        "-S",
        bison_root_file.to_str().unwrap(),
        "-o",
        output.to_str().unwrap(),
        input.to_str().unwrap(),
    ];
    println!("bison args = {:#?}", args);

    let output = Command::new("bison").args(args).output()?;

    if output.status.success() {
        return Ok(());
    } else {
        let stderr = String::from_utf8(output.stderr).unwrap();
        return Err(Box::new(BisonErr {
            message: stderr,
            code: output.status.code(),
        }));
    }
}