//! Utility module which handles filesystem writes

use lcc::traits::AutoEncoder;

use std::collections::HashMap;
use std::error::Error;
use std::io::{self, Read, Write};
use std::{
    fs::{self, File, OpenOptions as OO}, path::PathBuf,
};

pub struct Filesystem {
    name: String,
    path: String,
    root: PathBuf,
}

/// A switching enum to determine what type of file to load

pub enum FileType {
    /// A data record file
    Record,
    /// A MetaDomain file
    Metadata,
    /// A simple checksum file
    Checksum,
}

macro_rules! file_ending {
    ($type:expr) => {
        match $type {
            FileType::Record => "record",
            FileType::Metadata => "meta",
            _ => "dat",
        }
    };
}

impl Filesystem {
    pub fn create(path: &str, name: &str) -> Filesystem {
        let mut buffer = PathBuf::new();
        buffer.push(path);
        buffer.push(format!("{}.vault", name));

        Filesystem {
            name: name.to_owned(),
            path: path.to_owned(),
            root: buffer,
        }
    }

    /// Create required directories
    pub fn scaffold(&self) -> Option<()> {
        fs::create_dir_all(&self.root).ok()?;
        fs::create_dir(&self.root.join("records")).ok()?;
        fs::create_dir(&self.root.join("metadata")).ok()?;
        fs::create_dir(&self.root.join("checksums")).ok()?;
        Some(())
    }

    /// Load all files of a certain type into a Vec<String>
    pub fn fetch<T: AutoEncoder>(&self, types: FileType) -> Result<Vec<T>, Box<Error>> {
        Ok(fs::read_dir(match types {
            FileType::Record => self.root.join("records"),
            FileType::Metadata => self.root.join("metadata"),
            _ => self.root.join("."),
        })?.into_iter()
            .filter_map(|r| r.ok())
            .filter(|f| match f.file_type() {
                Ok(vf) => vf.is_file(),
                _ => false,
            })
            .map(|de| de.path())
            .filter_map(|p| p.into_os_string().into_string().ok())
            .filter_map(|s| File::open(s).ok())
            .filter_map(|mut f| f.get_string().ok())
            .filter_map(|s| T::decode(&s).ok())
            .collect())
    }

    pub fn pull<T: AutoEncoder>(&self, types: FileType, id: &str) -> Result<T, Box<Error>> {
        Ok(T::decode(
            &File::open(self.root.join(&format!("{}.{}", id, file_ending!(types))))?.get_string()?,
        )?)
    }

    pub fn sync<T>(&self, data: &HashMap<String, T>, types: FileType) -> Result<(), Box<Error>>
    where
        T: AutoEncoder,
    {
        data.into_iter()
            .map(|(k, v)| (k, v.encode().ok()))
            .map(|(k, v)| (self.root.join(format!("{}.{}", k, file_ending!(types))), v))
            .filter(|(_, v)| v.is_some())
            .map(|(k, v)| (k, v.unwrap()))
            .map(|(path, data): (PathBuf, String)| (OO::new().write(true).open(path), data))
            .filter(|(path, _)| path.is_ok())
            .map(|(file, data)| (file.unwrap(), data))
            .for_each(|(mut file, data)| {
                file.write_all(data.as_bytes())
                    .expect("Failed to write file!")
            });

        Ok(())
    }
}

/// A utility trait to read the conents from a file in
/// a single line.
pub trait FileToString {
    /// Read the file contents into a string without any
    /// error handling.
    fn get_string(&mut self) -> Result<String, io::Error>;
}

impl FileToString for File {
    fn get_string(&mut self) -> Result<String, io::Error> {
        let mut s = String::new();
        return match self.read_to_string(&mut s) {
            Ok(_) => Ok(s),
            Err(e) => Err(e),
        };
    }
}