use std::path::{PathBuf,Path};
use std::fs;
use std::os::unix::fs::MetadataExt;
use std::ffi::OsString;

#[derive(Debug)]
pub enum Error {
    EntryNotFound(String)
}

#[derive(Debug, Clone)]
pub struct Entry {
    pub name: OsString,
    pub path: PathBuf,
    pub base_dir: PathBuf,
}

impl Entry {
    pub fn new(path: PathBuf, name: OsString, base_dir: PathBuf) -> Entry {
        Entry {
            path,
            name,
            base_dir,
        }
    }

    pub fn read_setting(&self, setting: &str) -> Option<String> {
        let mut path = self.path.clone();
        path.set_extension(setting);
        read_or_none(&path)
    }
}

/// Load single entry from folder
pub fn entry(basedir: &str, filter: impl Fn(&Path) -> bool, name: &str) -> Option<Entry> {
    let basepath = PathBuf::from(&basedir);
    let path = basepath.clone().join(name);

    if !path.exists() || !filter(&path) {
        return None;
    }

    Some(Entry::new(
            path.clone(),
            path.file_name().expect("Failed to read file name").to_os_string(),
            basepath
            ))
}

/// Loads entire database from folder
pub fn from(path_name: &str, filter: impl Fn(&Path) -> bool) -> Result<Vec<Entry>, std::io::Error> {
    let path = PathBuf::from(&path_name);

    let mut entries = Vec::new();

    for file in path.read_dir()? {
        if file.is_err() {
            // Dismiss individual errors (in case there's a permission problem)
            // TODO: maybe print a warning? Actually a configurable error level
            // (using enum variants) should be passed to the function to configure
            // whether to continue silently or error out for individual files
            continue;
        }
        let entry = file?.path();
        if filter(&entry) {
            entries.push(
                Entry::new(
                    entry.clone(),
                    entry.file_name().expect("Failed to read file name").to_os_string(),
                    path.clone()
                    )
                );
        }
    }

    return Ok(entries);
}

/// Reads the file and strips whitespace (including newlines)
/// Useful for file-based key-value store
pub fn read_or_none(path: &Path) -> Option<String> {
    if !path.is_file() {
        return None;
    }
    match fs::read_to_string(path) {
        Ok(content) => {
            // Remove trailing space/newlines
            Some(content.trim().to_string())
        },
        Err(e) => {
            eprintln!("IO ERROR: {}", e);
            None
        }
    }
}

fn list_files(path: &Path) -> Vec<PathBuf> {
    let mut res = Vec::new();
    match fs::read_dir(path) {
        Ok(files) => {
            for r in files {
                match r {
                    Ok(entry) => {
                        let file = entry.path();
                        if file.is_file() {
                            res.push(file);
                        }
                    },
                    Err(e) => {
                        eprintln!("IOERROR: {}", e)
                    }
                }
            }
        },
        Err(e) => {
            eprintln!("IOERROR: {}", e);
        }
    }
    return res;
}


// If the file doesn't exist or fails, return false
pub fn is_executable(path: &Path) -> bool {
    // Do not match directories
    if !path.is_file() {
        return false;
    }
    match fs::metadata(path) {
        Ok(stat) => {
            let mode = stat.mode();
            // Check user exec permission)
            if (mode & 0o100) == 0o100 {
                true
            } else {
                false
            }
        },
        Err(e) => {
            eprintln!("IO Error: {}", e);
            false
        }
    }
}


#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn can_load_db() {
        let base_dir = "tests/success";
        let entries = from(base_dir, is_executable).expect("Could not load db");
        let entries_names: Vec<String> = entries.iter().map(|x| x.name.clone().into_string().unwrap()).collect();

        let expected: Vec<String> = vec!("task", "symlink", "no_source").iter().map(|x| x.to_string()).collect();

        assert_eq!(expected.len(), entries_names.len());

        for entry in expected {
            if !entries_names.contains(&entry.to_string()) {
                panic!("Could not find {}", &entry);
            }
        }
    }
}