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use super::errors::*;
use regex::Regex;
use std::path::{Path, PathBuf};

pub struct Paths;

impl Paths {
    pub fn shebang(path: &Path) -> Result<String> {
        let text = std::fs::read_to_string(path)
            .chain_err(|| ErrorKind::ShebangNotFound(path.to_path_buf()))?;
        let re = Regex::new(r"#!\s*([/:\.\w\-]+)")
            .chain_err(|| ErrorKind::ShebangNotFound(path.to_path_buf()))?;
        match re.captures(&text) {
            Some(caps) => {
                if caps.len() > 1 {
                    Ok(caps[1].to_string())
                } else {
                    Err(Error::from_kind(ErrorKind::ShebangNotFound(
                        path.to_path_buf(),
                    )))
                }
            }
            None => Err(Error::from_kind(ErrorKind::ShebangNotFound(
                path.to_path_buf(),
            ))),
        }
    }

    pub fn which(name: &str) -> Result<PathBuf> {
        let extensions = vec![".exe", ".bat", ".cmd", ""];
        for ext in extensions.iter() {
            let exe_name = format!("{}{}", name, ext);
            match Paths::which_exact(&exe_name) {
                Some(path) => {
                    return Ok(path);
                }
                None => {}
            };
        }
        Err(Error::from_kind(ErrorKind::UnrecognizedCommand(
            name.to_string(),
        )))
    }

    fn which_exact(name: &str) -> Option<PathBuf> {
        std::env::var_os("PATH").and_then(|paths| {
            std::env::split_paths(&paths)
                .filter_map(|dir| {
                    let full_path = dir.join(&name);
                    if full_path.is_file() {
                        Some(full_path)
                    } else {
                        None
                    }
                })
                .next()
        })
    }

    pub fn extension(path: &Path) -> String {
        match path.extension() {
            Some(os_str) => match os_str.to_str() {
                Some(ext) => ext.to_string(),
                None => "".to_string(),
            },
            None => "".to_string(),
        }
    }
}

#[cfg(test)]
#[test]
fn which_test() {
    match crate::paths::Paths::which("git") {
        Ok(git_path) => assert!(
            git_path.exists(),
            "path {} does not exist.",
            git_path.display()
        ),
        Err(e) => assert!(false, "which('git') returned an error: {}", e),
    }
}