// Sort of an internal API endpoint to make testing easy.
// Eventually we could expose this as JSON or Msgpack or whatever. For now
// it's just a Rust struct that we can test on without caring about 
// human-readable HTML

use std::{
	collections::HashMap,
	convert::TryInto,
	path::{Path, PathBuf},
};

use percent_encoding::percent_decode;
use tokio::{
	fs::{
		File,
		read_dir,
		ReadDir,
	},
	io::AsyncReadExt,
};

#[cfg (test)]
use always_equal::test::AlwaysEqual;

#[cfg (not (test))]
use always_equal::prod::AlwaysEqual;

use ptth_core::{
	http_serde::Method,
	prefix_match,
	prelude::*,
};

use crate::{
	load_toml,
};

use super::{
	errors::FileServerError,
	markdown,
	markdown::render_styled,
	range,
};

#[derive (Debug, PartialEq)]
pub struct ServeDirParams {
	pub path: PathBuf,
	pub dir: AlwaysEqual <ReadDir>,
}

#[derive (Debug, PartialEq)]
pub struct ServeFileParams {
	pub send_body: bool,
	pub range: range::ValidParsed,
	pub file: AlwaysEqual <File>,
}

#[derive (Debug, PartialEq)]
pub enum Response {
	Favicon,
	Forbidden,
	InvalidQuery,
	MethodNotAllowed,
	NotFound,
	RangeNotSatisfiable (u64),
	Redirect (String),
	Root,
	ServeDir (ServeDirParams),
	ServeFile (ServeFileParams),
	
	MarkdownErr (markdown::Error),
	MarkdownPreview (String),
}

fn serve_dir (
	path_s: &str,
	path: &Path,
	dir: tokio::fs::ReadDir,
	full_path: PathBuf,
	uri: &http::Uri
)
-> Result <Response, FileServerError>
{
	let has_trailing_slash = path_s.is_empty () || path_s.ends_with ('/');
	
	if ! has_trailing_slash {
		let file_name = path.file_name ().ok_or (FileServerError::NoFileNameRequested)?;
		let file_name = file_name.to_str ().ok_or (FileServerError::FilePathNotUtf8)?;
		return Ok (Response::Redirect (format! ("{}/", file_name)));
	}
	
	if uri.query ().is_some () {
		return Ok (Response::InvalidQuery);
	}
	
	let dir = dir.into ();
	
	Ok (Response::ServeDir (ServeDirParams {
		dir,
		path: full_path,
	}))
}

async fn serve_file (
	mut file: tokio::fs::File,
	uri: &http::Uri,
	send_body: bool,
	headers: &HashMap <String, Vec <u8>>
)
-> Result <Response, FileServerError>
{
	use std::os::unix::fs::PermissionsExt;
	
	let file_md = file.metadata ().await.map_err (FileServerError::CantGetFileMetadata)?;
	if file_md.permissions ().mode () == load_toml::CONFIG_PERMISSIONS_MODE 
	{
		return Ok (Response::Forbidden);
	}
	
	let file_len = file_md.len ();
	
	let range_header = headers.get ("range").and_then (|v| std::str::from_utf8 (v).ok ());
	
	Ok (match range::check (range_header, file_len) {
		range::Parsed::NotSatisfiable (file_len) => Response::RangeNotSatisfiable (file_len),
		range::Parsed::Valid (range) => {
			if uri.query () == Some ("as_markdown") {
				const MAX_BUF_SIZE: u32 = 1_000_000;
				
				if range.range_requested {
					return Ok (Response::InvalidQuery);
				}
				
				if file_len > MAX_BUF_SIZE.into () {
					Response::MarkdownErr (markdown::Error::TooBig)
				}
				else {
					let mut buffer = vec! [0_u8; MAX_BUF_SIZE.try_into ().expect ("Couldn't fit u32 into usize")];
					let bytes_read = file.read (&mut buffer).await?;
					buffer.truncate (bytes_read);
					
					match render_styled (&buffer) {
						Ok (x) => Response::MarkdownPreview (x),
						Err (x) => Response::MarkdownErr (x),
					}
				}
			}
			else {
				let file = file.into ();
				
				Response::ServeFile (ServeFileParams {
					file, 
					send_body, 
					range,
				})
			}
		},
	})
}

pub async fn serve_all (
	root: &Path,
	method: Method,
	uri: &str,
	headers: &HashMap <String, Vec <u8>>,
	hidden_path: Option <&Path>
)
-> Result <Response, FileServerError>
{
	use std::str::FromStr;
	use Response::*;
	
	info! ("Client requested {}", uri);
	
	let uri = http::Uri::from_str (uri).map_err (FileServerError::InvalidUri)?;
	
	let send_body = match &method {
		Method::Get => true,
		Method::Head => false,
		m => {
			debug! ("Unsupported method {:?}", m);
			return Ok (MethodNotAllowed);
		}
	};
	
	if uri.path () == "/favicon.ico" {
		return Ok (Favicon);
	}
	
	let path = match prefix_match ("/files", uri.path ()) {
		Some (x) => x,
		None => return Ok (Root),
	};
	
	if path == "" {
		return Ok (Redirect ("files/".to_string ()));
	}
	
	// TODO: There is totally a dir traversal attack in here somewhere
	
	let encoded_path = &path [1..];
	
	let path_s = percent_decode (encoded_path.as_bytes ()).decode_utf8 ().map_err (FileServerError::PathNotUtf8)?;
	let path = Path::new (&*path_s);
	
	let full_path = root.join (path);
	
	debug! ("full_path = {:?}", full_path);
	
	if let Some (hidden_path) = hidden_path {
		if full_path == hidden_path {
			return Ok (Forbidden);
		}
	}
	
	if let Ok (dir) = read_dir (&full_path).await {
		serve_dir (
			&path_s,
			path,
			dir,
			full_path,
			&uri
		)
	}
	else if let Ok (file) = File::open (&full_path).await {
		serve_file (
			file,
			&uri,
			send_body,
			headers
		).await
	}
	else {
		Ok (NotFound)
	}
}