use std::env;
use std::error::Error;
use std::fs::{read as read_file, File};
use std::io::ErrorKind::NotFound;
use std::io::Write;
use std::path::Path;

pub fn create_static_output(
  source_path: &Path,
  mut target: impl Write,
) -> Result<(), Box<dyn Error>> {
  let const_name = source_path
    .file_stem()
    .ok_or("Not a filename")?
    .to_str()
    .ok_or("Filename is not valid unicode")?
    .to_uppercase();
  let file = read_file(source_path)?;
  let content = std::str::from_utf8(&file)?;
  let fence = content.chars().filter(|&c| c == '#').collect::<String>() + "#";

  writeln!(
    target,
    "pub const {const_name}: &str = r{fence}\"{content}\"{fence};"
  )?;
  Ok(())
}

pub fn create_static_output_files(
  source_dir: &Path,
  dest_path: &Path,
) -> Result<(), Box<dyn Error>> {
  let mut f = File::create(dest_path)?;
  match source_dir.read_dir() {
    Ok(dir_content) => {
      for maybe_dir_entry in dir_content {
        create_static_output(&maybe_dir_entry?.path(), &mut f)?;
      }
    }
    Err(err) => {
      if err.kind() != NotFound {
        return Err(format!("Unexpected error: {err}").into());
      }
    }
  }
  Ok(())
}

pub fn main() -> Result<(), Box<dyn Error>> {
  create_static_output_files(
    Path::new("static_files"),
    &(Path::new(&env::var("OUT_DIR")?).join("static_files.rs")),
  )
}