use std::error;
use std::io::{self, BufRead, BufReader, Write};
use std::fmt;
use std::fs::{File, OpenOptions};
use std::path::Path;

#[cfg(test)]
mod tests;

struct Alias {
    alias: String,
    name: String,
    email: String,
}

impl Alias {
    fn new(email: &str) -> Alias {
        let mut split: Vec<&str> = email.split_whitespace().collect();

        // Remove "From: "
        split.remove(0);

        let mut alias = String::new();
        let mut name = String::new();
        let mut email = String::new();

        if split.len() == 1 {
            alias = split[0].to_lowercase().to_string();
            email = split[0].to_string();
        } else if split.len() == 2 {
            alias = split[0].to_lowercase().to_string();
            name = split[0].to_string();
            email = split[1].to_string();
        } else if split.len() > 2 {
            alias = format!("{}-{}", split[split.len() - 2], split[0]).to_lowercase().to_string();
            name = split[0..(split.len() - 1)].join(" ");
            email = split[split.len() - 1].to_string();
        }

        alias = alias.replace(',', "");
        alias = alias.replace('\'', "");
        alias = alias.replace('"', "");

        Alias { alias: alias, name: name, email: email }
    }

    fn to_string(&self) -> String {
        if self.name.is_empty() {
            format!("alias {} {}", self.alias, self.email)
        } else {
            format!("alias {} {} {}", self.alias, self.name, self.email)
        }
    }

    fn write_to_file<P: AsRef<Path>>(&self, file: P) -> Result<(), io::Error> {
        let mut f = try!(OpenOptions::new().append(true).open(file));
        try!(f.write_all(format!("{}\n", self.to_string()).as_bytes()));
        Ok(())
    }

    fn update_alias_id(&mut self, similar_aliases: Vec<String>) {
        if !similar_aliases.is_empty() {
            self.alias = format!("{}-{}", self.alias, similar_aliases.len() + 1);
        }
    }
}

fn write_alias(from: String) -> Result<(), AliasSearchError> {
    let mut alias = Alias::new(&from);
    let similar_aliases = try!(find_alias_in_file(&alias, "./testaliases"));
    alias.update_alias_id(similar_aliases);
    try!(alias.write_to_file("./testaliases"));
    Ok(())
}

#[derive(Debug)]
enum AliasSearchError {
    NotFound,
    EmailExists,
    Io(io::Error),
}

impl fmt::Display for AliasSearchError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            AliasSearchError::NotFound => write!(f, ""),
            AliasSearchError::EmailExists => write!(f, ""),
            AliasSearchError::Io(ref err) => write!(f, "IO error: {}", err),
        }
    }
}

impl error::Error for AliasSearchError {
    fn description(&self) -> &str {
        match *self {
            AliasSearchError::NotFound => "Alias could not be found in aliases file",
            AliasSearchError::EmailExists => "Email already exists in aliases file",
            AliasSearchError::Io(ref err) => err.description(),
        }
    }

    fn cause(&self) -> Option<&error::Error> {
        match *self {
            AliasSearchError::Io(ref err) => Some(err),
            _ => None,
        }
    }
}

impl From<io::Error> for AliasSearchError {
    fn from(err: io::Error) -> AliasSearchError {
        AliasSearchError::Io(err)
    }
}

#[cfg(test)]
impl PartialEq<AliasSearchError> for AliasSearchError {
    fn eq(&self, other: &AliasSearchError) -> bool {
        match *self {
            AliasSearchError::NotFound => match *other {
                AliasSearchError::NotFound => true,
                _ => false,
            },
            AliasSearchError::EmailExists => match *other {
                AliasSearchError::EmailExists => true,
                _ => false,
            },
            AliasSearchError::Io(_) => match *other {
                AliasSearchError::Io(_) => true,
                _ => false,
            },
        }
    }
}

fn find_alias_in_file(alias: &Alias, file: &str) -> Result<Vec<String>, AliasSearchError> {
    let mut matches = Vec::new();
    let f = try!(File::open(file));
    let file = BufReader::new(&f);
    for line in file.lines() {
        let line = try!(line);
        let split: Vec<&str> = line.split_whitespace().collect();

        if line.contains(&alias.email) {
            return Err(AliasSearchError::EmailExists)
        }

        if split[1].starts_with(&alias.alias) {
            matches.push(split[1].to_owned());
        }
    }

    if matches.is_empty() {
        Err(AliasSearchError::NotFound)
    } else {
        Ok(matches)
    }
}

fn main() {
    let stdin = io::stdin();

    for line in stdin.lock().lines() {
        let line = line.unwrap();

        // Write the message to STDOUT so that it can be properly read by Mutt
        println!("{}", line);

        if line.starts_with("From: ") {
            match write_alias(line) {
                Ok(_)  => continue,
                Err(AliasSearchError::NotFound) | Err(AliasSearchError::EmailExists) => continue,
                Err(e) => io::stderr().write(e.to_string().as_bytes()).ok(),
            };
        }
    }
}