use std::borrow::Cow;

use handlebars::Handlebars;
use serde::Serialize;
use tracing::instrument;
use tokio::fs::{
	DirEntry as FsDirEntry,
	ReadDir as FsReadDir,
};

use super::{
	FileServerError,
	Response,
	metrics,
	pretty_print_bytes,
};

#[derive (Serialize)]
struct Dir <'a> {
	#[serde (flatten)]
	instance_metrics: &'a metrics::Startup,
	
	path: Cow <'a, str>,
	entries: Vec <DirEntry>,
}

#[derive (Serialize)]
struct DirEntry {
	icon: &'static str,
	trailing_slash: &'static str,
	
	// Unfortunately file_name will allocate as long as some platforms
	// (Windows!) aren't UTF-8. Cause I don't want to write separate code
	// for such a small problem.
	
	file_name: String,
	
	// This could be a Cow with file_name if no encoding was done but
	// it's simpler to allocate.
	
	encoded_file_name: String,
	
	size: Cow <'static, str>,
	
	error: bool,
}

pub async fn serve_root (
	state: &super::State,
) -> Result <Response, FileServerError>
{
	#[derive (Serialize)]
	struct RootHtml <'a> {
		metrics_startup: &'a metrics::Startup,
		metrics_interval: &'a Option <metrics::Interval>,
	}
	
	let params = RootHtml {
		metrics_startup: &state.metrics_startup,
		metrics_interval: &**state.metrics_interval.load (),
	};
	
	let s = state.handlebars.render ("file_server_root", &params)?;
	
	Ok (serve_html (s))
}

#[instrument (level = "debug", skip (handlebars, instance_metrics, dir))]
pub async fn serve_dir (
	handlebars: &Handlebars <'static>,
	instance_metrics: &metrics::Startup,
	path: Cow <'_, str>,
	mut dir: FsReadDir
) -> Result <Response, FileServerError>
{
	let mut entries = vec! [];
	
	while let Ok (Some (entry)) = dir.next_entry ().await {
		entries.push (read_dir_entry (entry).await);
	}
	
	entries.sort_unstable_by (|a, b| a.file_name.cmp (&b.file_name));
	
	let s = handlebars.render ("file_server_dir", &Dir {
		path,
		entries,
		instance_metrics,
	})?;
	
	Ok (serve_html (s))
}

async fn read_dir_entry (entry: FsDirEntry) -> DirEntry
{
	use percent_encoding::{
		CONTROLS,
		utf8_percent_encode,
	};
	
	let file_name = match entry.file_name ().into_string () {
		Ok (x) => x,
		Err (_) => return DirEntry {
			icon: emoji::ERROR,
			trailing_slash: "",
			file_name: "File / directory name is not UTF-8".into (),
			encoded_file_name: "".into (),
			size: "".into (),
			error: true,
		},
	};
	
	let metadata = match entry.metadata ().await {
		Ok (x) => x,
		Err (_) => return DirEntry {
			icon: emoji::ERROR,
			trailing_slash: "",
			file_name: "Could not fetch metadata".into (),
			encoded_file_name: "".into (),
			size: "".into (),
			error: true,
		},
	};
	
	let (trailing_slash, icon, size) = {
		let t = metadata.file_type ();
		
		if t.is_dir () {
			("/", emoji::FOLDER, "".into ())
		}
		else {
			("", get_icon (&file_name), pretty_print_bytes (metadata.len ()).into ())
		}
	};
	
	let encoded_file_name = utf8_percent_encode (&file_name, CONTROLS).to_string ();
	
	DirEntry {
		icon,
		trailing_slash: &trailing_slash,
		file_name,
		encoded_file_name,
		size,
		error: false,
	}
}

pub fn serve_html (s: String) -> Response {
	let mut resp = Response::default ();
	resp
		.header ("content-type".to_string (), "text/html; charset=UTF-8".to_string ().into_bytes ())
		.body_bytes (s.into_bytes ())
	;
	resp
}

fn get_icon (file_name: &str) -> &'static str {
	if 
		file_name.ends_with (".mp4") ||
		file_name.ends_with (".avi") ||
		file_name.ends_with (".mkv") ||
		file_name.ends_with (".webm")
	{
		emoji::VIDEO
	}
	else if 
		file_name.ends_with (".jpg") ||
		file_name.ends_with (".jpeg") ||
		file_name.ends_with (".png") ||
		file_name.ends_with (".bmp")
	{
		emoji::PICTURE
	}
	else {
		emoji::FILE
	}
}

mod emoji {
	pub const VIDEO: &str = "\u{1f39e}\u{fe0f}";
	pub const PICTURE: &str = "\u{1f4f7}";
	pub const FILE: &str = "\u{1f4c4}";
	pub const FOLDER: &str = "\u{1f4c1}";
	pub const ERROR: &str = "\u{26a0}\u{fe0f}";
}

#[cfg (test)]
mod tests {
	#[test]
	fn icons () {
		let video = "🎞️";
		let picture = "📷";
		let file = "📄";
		
		for (input, expected) in vec! [
			("copying_is_not_theft.mp4",  video),
			("copying_is_not_theft.avi",  video),
			("copying_is_not_theft.mkv",  video),
			("copying_is_not_theft.webm", video),
			("lolcats.jpg",  picture),
			("lolcats.jpeg", picture),
			("lolcats.png",  picture),
			("lolcats.bmp",  picture),
			("ptth.log",  file),
			("README.md", file),
			("todo.txt",  file),
		].into_iter () {
			assert_eq! (super::get_icon (input), expected);
		}
	}
}