use super::*;
use std::{
    fmt,
    borrow::Cow,
    path::{
	Path,
	PathBuf,
    },
};

const DEFAULT_BINARY_NAME: &'static str = "leanify";

#[derive(Debug)]
pub enum Error
{
    FileFailed(PathBuf),
    PathFailed(PathBuf),
}

impl std::error::Error for Error{}
impl std::fmt::Display for Error
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	match self {
	    Self::FileFailed(path) => write!(f, "file {:?} does not exist.", path),
	    Self::PathFailed(path) => write!(f, "no directory in `$PATH` contained file {:?}", path),
	}
    }
}

fn binary_name() -> Cow<'static, str>
{
    if let Ok(bin_name) = std::env::var("LEANIFY") {
	if bin_name.len() > 0 {
	    return Cow::Owned(bin_name);
	}
    }
    return Cow::Borrowed(DEFAULT_BINARY_NAME);
}

fn get_path() -> Vec<PathBuf>
{
    if let Ok(path) = std::env::var("PATH")
    {
	path.split(":").filter_map(|x| {
	    let path = Path::new(x);
	    if path.is_dir() {
		Some(path.to_owned())
	    } else {
		None
	    }
	}).collect()
    } else {
	Vec::default()
    }
}

/// Find the path to leanify binary
pub fn find_binary() -> Result<PathBuf, Error>
{
    let path = binary_name();
    let path = Path::new(path.as_ref());

    if path.is_file() {
	Ok(path.to_owned())
    }
    else if !path.is_absolute() {
	//Lookup in $PATH
	for spath in get_path().into_iter() {
	    let spath = spath.join(path);
	    if spath.is_file() {
		return Ok(spath);
	    }
	}
	Err(Error::PathFailed(path.to_owned()))
    } else {
	Err(Error::FileFailed(path.to_owned()))
    }
}