use POP3StreamTypes::{Basic, Ssl};
use POP3Command::{Greet, User, Pass, Stat, UidlAll, UidlOne, ListAll, ListOne, Retr, Dele, Noop, Rset, Quit};
use std::string::String;
use async_std::net::{ToSocketAddrs,TcpStream};
use async_native_tls::{TlsStream, TlsConnector};
use std::str::FromStr;
use regex::Regex;
use lazy_static::lazy_static;
use async_std::io::{Error, ErrorKind, Result};
use async_std::prelude::*;

lazy_static! {
    static ref ENDING_REGEX: Regex = Regex::new(r"^\.\r\n$").unwrap();
    static ref OK_REGEX: Regex = Regex::new(r"\+OK(.*)").unwrap();
    static ref ERR_REGEX: Regex = Regex::new(r"-ERR(.*)").unwrap();
    static ref STAT_REGEX: Regex = Regex::new(r"\+OK (\d+) (\d+)\r\n").unwrap();
    static ref MESSAGE_DATA_UIDL_ALL_REGEX: Regex = Regex::new(r"(\d+) ([\x21-\x7e]+)\r\n").unwrap();
    static ref MESSAGE_DATA_UIDL_ONE_REGEX: Regex = Regex::new(r"\+OK (\d+) ([\x21-\x7e]+)\r\n").unwrap();
    static ref MESSAGE_DATA_LIST_ALL_REGEX: Regex = Regex::new(r"(\d+) (\d+)\r\n").unwrap();
}

/// Wrapper for a regular TcpStream or a SslStream.
#[derive(Debug)]
enum POP3StreamTypes {
	Basic(TcpStream),
	Ssl(TlsStream<TcpStream>)
}

/// The stream to use for interfacing with the POP3 Server.
#[derive(Debug)]
pub struct POP3Stream {
	stream: POP3StreamTypes,
	pub is_authenticated: bool
}

/// List of POP3 Commands
#[derive(Clone)]
enum POP3Command {
	Greet,
	User,
	Pass,
	Stat,
    UidlAll,
    UidlOne,
	ListAll,
	ListOne,
	Retr,
	Dele,
	Noop,
	Rset,
	Quit
}

impl POP3Stream {

	/// Creates a new POP3Stream.
	pub async fn connect<A:ToSocketAddrs>(addr: A,ssl_context: Option<TlsConnector>,domain: &str) -> Result<POP3Stream> {
		let tcp_stream = TcpStream::connect(addr).await?;
		let mut socket = match ssl_context {
			Some(context) => POP3Stream {
                stream: Ssl(TlsConnector::connect(&context, domain,tcp_stream).await.unwrap()),
                is_authenticated: false},
			None => POP3Stream {
                stream: Basic(tcp_stream),
                is_authenticated: false},
		};
		match socket.read_response(Greet).await {
			Ok(_) => (),
			Err(_) => return Err(Error::new(ErrorKind::Other, "Failed to read greet response"))
		}
		Ok(socket)
	}

	async fn write_str(&mut self, s: &str) -> Result<()> {
		match self.stream {
			Ssl(ref mut stream) => stream.write_fmt(format_args!("{}", s)).await,
			Basic(ref mut stream) => stream.write_fmt(format_args!("{}", s)).await,
		}
	}

	async fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
		match self.stream {
			Ssl(ref mut stream) => stream.read(buf).await,
			Basic(ref mut stream) => stream.read(buf).await,
		}
	}

	/// Login to the POP3 server.
	pub async fn login(&mut self, username: &str, password: &str) -> POP3Result {
		let user_command = format!("USER {}\r\n", username);
		let pass_command = format!("PASS {}\r\n", password);
		//Send user command
		match self.write_str(&user_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}
		match self.read_response(User).await {
			Ok(_) => {
				match self.write_str(&pass_command).await {
					Ok(_) => self.is_authenticated = true,
					Err(_) => panic!("Error writing"),
				}
				match self.read_response(Pass).await {
					Ok(_) => {
						POP3Result::POP3Ok
					},
					Err(_) => panic!("Failure to use PASS")
				}
			},
			Err(_) => panic!("Failure to use USER")
		}
	}

	/// Gives the current number of messages in the mailbox and the total size in bytes of the mailbox.
	pub async fn stat(&mut self) -> POP3Result {
		if !self.is_authenticated {
			panic!("login");
		}

		let stat_command = "STAT\r\n";
		match self.write_str(&stat_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}
		match self.read_response(Stat).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

    pub async fn uidl(&mut self, message_number: Option<i32>) -> POP3Result {
        if !self.is_authenticated {
            panic!("login");
        }

        let uidl_command = match message_number {
            Some(i) => format!("UIDL {}\r\n", i),
            None => format!("UIDL\r\n"),
        };
        let command_type = match message_number {
            Some(_) => UidlOne,
            None => UidlAll,
        };

        match self.write_str(&uidl_command).await {
            Ok(_) => {},
            Err(_) => panic!("Error writing"),
        }

        match self.read_response(command_type).await {
            Ok(res) => {
                match res.result {
                    Some(s) => s,
                    None => POP3Result::POP3Err
                }
            },
            Err(_) => POP3Result::POP3Err
        }
    }

	/// List displays a summary of messages where each message number is shown and the size of the message in bytes.
	pub async fn list(&mut self, message_number: Option<i32>) -> POP3Result {
		if !self.is_authenticated {
			panic!("login");
		}

		let list_command = match message_number {
							Some(i) => format!("LIST {}\r\n", i),
							None => format!("LIST\r\n"),
						};
		let command_type = match message_number {
							Some(_) => ListOne,
							None => ListAll,
						};

		match self.write_str(&list_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(command_type).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

	/// retrieves the message of the message id given.
	pub async fn retr(&mut self, message_id: i32) -> POP3Result {
		if !self.is_authenticated {
			panic!("login");
		}

		let retr_command = format!("RETR {}\r\n", message_id);

		match self.write_str(&retr_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(Retr).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

	/// Delete the message with the given message id.
	pub async fn dele(&mut self, message_id: i32) -> POP3Result {
		if !self.is_authenticated {
			panic!("login");
		}

		let dele_command = format!("DELE {}\r\n", message_id);

		match self.write_str(&dele_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(Dele).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

	/// This resets the session to its original state.
	pub async fn rset(&mut self) -> POP3Result {
		if !self.is_authenticated {
			panic!("Not Logged In");
		}

		let retr_command = format!("RETR\r\n");

		match self.write_str(&retr_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(Rset).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

	/// Quits the current session.
	pub async fn quit(&mut self) -> POP3Result {
		let quit_command = "QUIT\r\n";

		match self.write_str(&quit_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(Quit).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => POP3Result::POP3Err
		}
	}

	/// Doesn't do anything. This is usually just used to keep the connection open.
	pub async fn noop(&mut self) -> POP3Result {
		if !self.is_authenticated {
			panic!("Not Logged In");
		}

		let noop_command = "noop\r\n";

		match self.write_str(noop_command).await {
			Ok(_) => {},
			Err(_) => panic!("Error writing"),
		}

		match self.read_response(Noop).await {
			Ok(res) => {
				match res.result {
					Some(s) => s,
					None => POP3Result::POP3Err
				}
			},
			Err(_) => panic!("Error noop")
		}
	}

	async fn read_response(&mut self, command: POP3Command) -> Result<Box<POP3Response>> {
		let mut response = Box::new(POP3Response::new());
		//Carriage return
		let cr = 0x0d;
		//Line Feed
		let lf = 0x0a;
		let mut line_buffer: Vec<u8> = Vec::new();

		while !response.complete {
			while line_buffer.len() < 2 || (line_buffer[line_buffer.len()-1] != lf && line_buffer[line_buffer.len()-2] != cr) {
				let byte_buffer: &mut [u8] = &mut [0];
				match self.read(byte_buffer).await {
					Ok(_) => {},
					Err(_) => println!("Error Reading!"),
				}
				line_buffer.push(byte_buffer[0]);
			}

			match String::from_utf8(line_buffer.clone()) {
        		Ok(res) => {
          			response.add_line(res, command.clone());
            		line_buffer = Vec::new();
        		},
        		Err(_) => return Err(Error::new(ErrorKind::Other, "Failed to read the response"))
      		}
		}
		Ok(response)
	}
}

#[derive(Clone,Copy,Debug)]
pub struct POP3EmailMetadata {
	pub message_id: i32,
	pub message_size: i32
}

#[derive(Clone,Debug)]
pub struct POP3EmailUidldata {
    pub message_id: i32,
    pub message_uid: String
}

#[derive(Debug)]
pub enum POP3Result {
	POP3Ok,
	POP3Err,
	POP3Stat {
		num_email: i32,
		mailbox_size: i32
	},
    POP3Uidl {
        emails_metadata: Vec<POP3EmailUidldata>,
    },
	POP3List {
		emails_metadata: Vec<POP3EmailMetadata>,
	},
	POP3Message {
		raw: Vec<String>,
	},
}

#[derive(Default)]
struct POP3Response {
	complete: bool,
	lines: Vec<String>,
	result: Option<POP3Result>
}

impl POP3Response {
	fn new() -> POP3Response {
		POP3Response {
			complete: false,
			lines: Vec::new(),
			result: None
		}
	}

	fn add_line(&mut self, line: String, command: POP3Command) {
		//We are retreiving status line
		if self.lines.len() == 0 {
			if OK_REGEX.is_match(&line) {
				self.lines.push(line);
				match command {
					Greet|User|Pass|Quit|Dele|Rset => {
						self.result = Some(POP3Result::POP3Ok);
						self.complete = true;
					},
					Stat => {
						self.complete = true;
						self.parse_stat()
					},
                                    UidlAll => {

                                    },
                                    UidlOne => {
                                        self.complete = true;
                                        self.parse_uidl_one();
                                    },
					ListAll => {

					},
					ListOne => {
						self.complete = true;
						self.parse_list_one();
					},
					Retr => {

					},
					_ => self.complete = true,
				}
			} else if ERR_REGEX.is_match(&line) {
				self.lines.push(line);
				self.result = Some(POP3Result::POP3Err);
				self.complete = true;
			}
		} else {
			if ENDING_REGEX.is_match(&line) {
				self.lines.push(line);
				match command {
                                    UidlAll => {
                                        self.complete = true;
                                        self.parse_uidl_all();
                                    },
					ListAll => {
						self.complete = true;
						self.parse_list_all();
					},
					Retr => {
						self.complete = true;
						self.parse_message();
					},
					_ => self.complete = true,
				}
			} else {
				self.lines.push(line);
			}
		}
	}

	fn parse_stat(&mut self) {
		let caps = STAT_REGEX.captures(&self.lines[0]).unwrap();
		let num_emails = FromStr::from_str(caps.get(1).unwrap().as_str());
		let total_email_size = FromStr::from_str(caps.get(2).unwrap().as_str());
		self.result = Some(POP3Result::POP3Stat {
			num_email: num_emails.unwrap(),
			mailbox_size: total_email_size.unwrap()
		})
	}


    fn parse_uidl_all(&mut self) {
        let mut metadata = Vec::new();

        for i in 1..self.lines.len() - 1 {
            let caps = MESSAGE_DATA_UIDL_ALL_REGEX.captures(&self.lines[i]).unwrap();
            let message_id = FromStr::from_str(caps.get(1).unwrap().as_str());
            let message_uid = caps.get(2).unwrap().as_str();

            metadata.push(POP3EmailUidldata {
                message_id: message_id.unwrap(),
                message_uid: message_uid.to_owned()
            });
        }

        self.result = Some(POP3Result::POP3Uidl {
            emails_metadata: metadata
        });
    }

    fn parse_uidl_one(&mut self) {
        let caps = MESSAGE_DATA_UIDL_ONE_REGEX.captures(&self.lines[0]).unwrap();
        let message_id = FromStr::from_str(caps.get(1).unwrap().as_str());
        let message_uid = caps.get(2).unwrap().as_str();

        self.result = Some(POP3Result::POP3Uidl {
            emails_metadata: vec![POP3EmailUidldata{
                    message_id: message_id.unwrap(),
                    message_uid: message_uid.to_owned()
            }]
        });
    }

	fn parse_list_all(&mut self) {
		let mut metadata = Vec::new();

		for i in 1 .. self.lines.len()-1 {
			let caps = MESSAGE_DATA_LIST_ALL_REGEX.captures(&self.lines[i]).unwrap();
			let message_id = FromStr::from_str(caps.get(1).unwrap().as_str());
			let message_size = FromStr::from_str(caps.get(2).unwrap().as_str());
			metadata.push(POP3EmailMetadata{ message_id: message_id.unwrap(), message_size: message_size.unwrap()});
		}
		self.result = Some(POP3Result::POP3List {
			emails_metadata: metadata
		});
	}

	fn parse_list_one(&mut self) {
		let caps = STAT_REGEX.captures(&self.lines[0]).unwrap();
		let message_id = FromStr::from_str(caps.get(1).unwrap().as_str());
		let message_size = FromStr::from_str(caps.get(2).unwrap().as_str());
		self.result = Some(POP3Result::POP3List {
			emails_metadata: vec![POP3EmailMetadata{ message_id: message_id.unwrap(), message_size: message_size.unwrap()}]
		});
	}

	fn parse_message(&mut self) {
		let mut raw = Vec::new();
		for i in 1 .. self.lines.len()-1 {
			raw.push(self.lines[i].clone());
		}
		self.result = Some(POP3Result::POP3Message{
			raw: raw
		});
	}
}