// fif - File Info Fixer
// Copyright (C) 2021 Lynnesbian
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

mod parameters;
mod inspectors;

use std::path::{Path, PathBuf};
use walkdir::{WalkDir, DirEntry};
use mime_guess::Mime;
use smartstring::alias::String;
use clap::Clap;
use log::{debug, trace, info, warn, error};
use rayon::prelude::*;

struct Findings {
	file: PathBuf,
	valid: bool,
	mime: Mime,
}

impl Findings {
	fn recommended_extension(&self) -> Option<String> {
		inspectors::mime_extension_lookup(self.mime.clone())
			.map(|extensions| extensions[0].to_owned())
	}
}

// TODO: test if this actually works on a windows machine
#[cfg(windows)]
fn is_hidden(entry: &DirEntry) -> bool {
	use std::os::windows::prelude::*;
	use std::fs;
	fs::metadata(entry) // try to get metadata for file
		.map_or(
			false, // if getting metadata/attributes fails, assume it's not hidden
      |f| f.file_attributes() & 0x2 // flag for hidden - https://docs.microsoft.com/en-us/windows/win32/fileio/file-attribute-constants
		)
}

#[cfg(not(windows))]
fn is_hidden(entry: &DirEntry) -> bool {
	entry.file_name().to_str().map_or(false, |f| f.starts_with('.') && f != ".")
}

fn wanted_file(args: &parameters::Parameters, entry: &DirEntry) -> bool {
	if !args.scan_hidden && is_hidden(entry) {
		// skip hidden files and directories. this check is performed first because it's very lightweight.
		return false;
	}

	if entry.file_type().is_dir() {
		// always allow directories - there's no point doing file extension matching on something that isn't a file.
		return true;
	}

	let ext = extension_from_path(entry.path());

	if ext.is_none() { return false } // don't scan files without extensions. TODO - this should be configurable

	if let Some(extensions) = &args.extensions {
		// if the user has specified a list of extensions to check against, make sure this file ends in one of them.
		return extensions.contains(&ext.unwrap().to_lowercase().into())
	}
	true
}

fn extension_from_path(path: &Path) -> Option<String> {
	path.extension(). // Get the path's extension
		map(|e| String::from(e.to_string_lossy())) // Convert from OsStr to String
}

fn main() {
	let args = parameters::Parameters::parse();
	let mut builder = env_logger::Builder::from_default_env();
	builder
		// .format(|buf, r| writeln!(buf, "{} - {}", r.level(), r.args()))
		.format_module_path(false)
		.format_timestamp(None)
		.init();

	let db = xdg_mime::SharedMimeInfo::new();
	debug!("Iterating directory: {:?}", args.dirs);

	let stepper = WalkDir::new(&args.dirs).into_iter();
	let entries: Vec<DirEntry> = stepper
		.filter_entry(|e| wanted_file(&args, e)) // filter out unwanted files
		.filter_map(|e| e.ok()) // ignore anything that fails, e.g. files we don't have read access on
		.filter(|e| !e.file_type().is_dir()) // remove directories from the final list
		.collect();

	info!("Found {} items to check", entries.len());

	let results: Vec<Result<Findings, PathBuf>> = entries
		.par_iter()
		.map(|entry: &DirEntry | {
			// try to determine mimetype for this entry
			let result = inspectors::mime_type(&db, entry.path());

			if let Err(error) = result {
				// an error occurred while trying to read the file
				error!("{}: {}", entry.path().to_string_lossy(), error);
				return Err(entry.path().to_path_buf());
			}

			let result = result.unwrap();
			if result.is_none() {
				// the file was read successfully, but we were unable to determine its mimetype
				warn!("Couldn't determine mimetype for {}", entry.path().to_string_lossy());
				return Err(entry.path().to_path_buf());
			}

			let result = result.unwrap();

			// set of known extensions for the given mimetype
			let known_exts = inspectors::mime_extension_lookup(result.clone());
			// file extension for this particular file
			let entry_ext = extension_from_path(entry.path());

			let valid = match known_exts {
				// there is a known set of extensions for this mimetype, and the file has an extension
				Some(e) if entry_ext.is_some() => e.contains(&entry_ext.unwrap().to_lowercase().into()),
				// there is a known set of extensions for this mimetype, but the file has no extension
				Some(_) => false,
				// there is no known set of extensions for this mimetype -- assume it's correct
				None => true
			};

			Ok(Findings {
				file: entry.path().to_path_buf(),
				valid, // make this a function
				mime: result,
			})
		})
		.collect();

	for result in results {
		match result {
			Ok(r) => trace!("{:#?}: {:#?} - {:?} - {:?}", r.file, r.mime, r.valid, r.recommended_extension()),
			Err(f) => warn!("{:#?}: Error 0uo", f)
		}
	}

	debug!("Done");
}