use std::{io::Read, path::PathBuf};

use crate::DOT_GIT_DIR;

///
pub mod from_gitdir_file {
    /// The error returned by [`from_gitdir_file()`][crate::path::from_gitdir_file()].
    #[derive(Debug, thiserror::Error)]
    #[allow(missing_docs)]
    pub enum Error {
        #[error(transparent)]
        Io(#[from] std::io::Error),
        #[error(transparent)]
        Parse(#[from] crate::parse::gitdir::Error),
    }
}

fn read_regular_file_content_with_size_limit(path: &std::path::Path) -> std::io::Result<Vec<u8>> {
    let mut file = std::fs::File::open(path)?;
    let max_file_size = 1024 * 64; // NOTE: git allows 1MB here
    let file_size = file.metadata()?.len();
    if file_size > max_file_size {
        return Err(std::io::Error::new(
            std::io::ErrorKind::Other,
            format!(
                "Refusing to open files larger than {} bytes, '{}' was {} bytes large",
                max_file_size,
                path.display(),
                file_size
            ),
        ));
    }
    let mut buf = Vec::with_capacity(512);
    file.read_to_end(&mut buf)?;
    Ok(buf)
}

/// Reads a plain path from a file that contains it as its only content, with trailing newlines trimmed.
pub fn from_plain_file(path: &std::path::Path) -> Option<std::io::Result<PathBuf>> {
    use bstr::ByteSlice;
    let mut buf = match read_regular_file_content_with_size_limit(path) {
        Ok(buf) => buf,
        Err(err) if err.kind() == std::io::ErrorKind::NotFound => return None,
        Err(err) => return Some(Err(err)),
    };
    let trimmed_len = buf.trim_end().len();
    buf.truncate(trimmed_len);
    Some(Ok(gix_path::from_bstring(buf)))
}

/// Reads typical `gitdir: ` files from disk as used by worktrees and submodules.
pub fn from_gitdir_file(path: &std::path::Path) -> Result<PathBuf, from_gitdir_file::Error> {
    let buf = read_regular_file_content_with_size_limit(path)?;
    let mut gitdir = crate::parse::gitdir(&buf)?;
    if let Some(parent) = path.parent() {
        gitdir = parent.join(gitdir);
    }
    Ok(gitdir)
}

/// Conditionally pop a trailing `.git` dir if present.
pub fn without_dot_git_dir(mut path: PathBuf) -> PathBuf {
    if path.file_name().and_then(std::ffi::OsStr::to_str) == Some(DOT_GIT_DIR) {
        path.pop();
    }
    path
}