use std::{
	fs::{File, Metadata},
	io::{BufRead, BufReader},
	time::{Duration, SystemTime},
};

use camino::{Utf8Path, Utf8PathBuf};
use getopts::Options;

struct Context {
	root: Utf8PathBuf,
	ignores: Vec<String>,
}

impl Context {
	pub fn new(root: Utf8PathBuf) -> Self {
		Self {
			root,
			ignores: vec![],
		}
	}

	pub fn ignore_file(&mut self, ignore_path: Utf8PathBuf) {
		let file = File::open(ignore_path).unwrap();
		let mut bufread = BufReader::new(file);

		let mut line = String::new();
		loop {
			if bufread.read_line(&mut line).unwrap() == 0 {
				break;
			}

			if line.starts_with("\\#") || line.starts_with("/") {
				self.ignores.push(String::from((&line[1..]).trim()));
			} else if line.starts_with("#") || line.is_empty() || line.trim().is_empty() {
				()
			} else {
				self.ignores.push(line.trim().to_owned());
			}

			line.clear();
		}
	}

	pub fn is_file_ignored<P: AsRef<Utf8Path>>(&self, path: P) -> bool {
		match path.as_ref().strip_prefix(&self.root) {
			Ok(rel) => {
				for ignore in &self.ignores {
					if rel.starts_with(ignore) {
						return true;
					}
				}

				false
			}
			Err(_) => false,
		}
	}
}

fn main() {
	let mut opts = Options::new();
	#[rustfmt::skip]
	opts.optopt("", "ignore", "file of paths to ignore, one per line", "PATH");
	opts.optflag("h", "help", "print this help thing");

	let matches = match opts.parse(std::env::args()) {
		Ok(m) => m,
		Err(e) => {
			eprintln!("{e}");
			return;
		}
	};

	if matches.opt_present("h") {
		println!("{}", opts.usage("Usage: whenwasit [options] PATH"));
		return;
	}

	let root = match matches.free.get(1) {
		None => {
			println!("expected path");
			println!("{}", opts.usage("Usage: whenwasit [options] PATH"));
			return;
		}
		Some(p) => Utf8PathBuf::from(p),
	};

	let mut context = Context::new(root);

	if let Some(ignore) = matches.opt_str("ignore") {
		let ignore = Utf8PathBuf::from(ignore);
		context.ignore_file(ignore);
	}

	process(&context, &context.root)
}

/// Loop through the provided directory printing CSV rows. The `root_path` is
/// used to make printed paths relative to it.
///
/// Does two passes: First pass prints files. Second pass recurs, printing directories.
fn process(ctx: &Context, path: &Utf8Path) {
	//TODO: do not panic, please
	let this_meta = std::fs::metadata(&path).unwrap();
	let this_times = Times::metadata(&this_meta);
	row(&ctx.root, &path, &this_times);

	for entry in path.read_dir_utf8().unwrap() {
		let entry = entry.unwrap();

		match entry.file_type() {
			Err(_) => panic!(),
			Ok(ft) if ft.is_file() => {
				let path = entry.path();
				if ctx.is_file_ignored(path) {
					continue;
				}

				let meta = entry.metadata().unwrap();
				let times = Times::metadata(&meta);
				row(&ctx.root, path, &times)
			}
			Ok(_) => {}
		}
	}

	for entry in path.read_dir_utf8().unwrap() {
		let entry = entry.unwrap();

		match entry.file_type() {
			Err(_) => panic!(),
			Ok(ft) if ft.is_dir() => {
				let path = entry.path();
				if ctx.is_file_ignored(path) {
					continue;
				}

				process(ctx, entry.path())
			}
			Ok(_) => {}
		}
	}
}

fn row<P: AsRef<Utf8Path>>(root: &Utf8Path, path: P, times: &Times) {
	let relative = path
		.as_ref()
		.strip_prefix(root)
		.expect("row wasn't relative to the root; what happened?");

	/// Returns an owned string with the duration formatted as seconds, or a
	/// borrowed empty string
	fn time_string(time: Option<Duration>) -> String {
		time.map(|d| d.as_secs().to_string()).unwrap_or_default()
	}

	println!(
		"{},{},{},{}",
		escape(relative),
		time_string(times.created()),
		time_string(times.modified()),
		time_string(times.accessed())
	);
}

/// Blackslash-escape comma and backslash
fn escape<S: AsRef<str>>(raw: S) -> String {
	let raw = raw.as_ref();

	let mut escaped = String::with_capacity(raw.len());
	for c in raw.chars() {
		match c {
			',' | '\\' => {
				escaped.push('\\');
				escaped.push(c);
			}
			_ => escaped.push(c),
		}
	}

	escaped
}

struct Times {
	created: Option<SystemTime>,
	modified: Option<SystemTime>,
	accessed: Option<SystemTime>,
}

impl Times {
	/// Get the btime, mtime, atime from the Metadata. If a time cannot
	/// be attained, leave a None in it's place
	pub fn metadata(meta: &Metadata) -> Self {
		Self {
			created: meta.created().ok(),
			modified: meta.modified().ok(),
			accessed: meta.accessed().ok(),
		}
	}

	/// The time since the Unix Epoch the file was created
	pub fn created(&self) -> Option<Duration> {
		Self::from_epoch(self.created.as_ref())
	}

	/// The time since the Unix Epoch the file was last modified
	pub fn modified(&self) -> Option<Duration> {
		Self::from_epoch(self.modified.as_ref())
	}

	/// The time since the Unix Epoch the file was last accessed
	pub fn accessed(&self) -> Option<Duration> {
		Self::from_epoch(self.accessed.as_ref())
	}

	fn from_epoch(maybe_time: Option<&SystemTime>) -> Option<Duration> {
		maybe_time.map(|st| st.duration_since(SystemTime::UNIX_EPOCH).unwrap())
	}
}