use std::fmt;
use regex::Regex;
use std::result::Result;
use std::error::Error;

pub struct QifFile {
    header: String,
    entries: Vec<QifEntry>
}

impl QifFile {
    pub fn new(header: String) -> QifFile {
        QifFile {
            header: header,
            entries: Vec::new()
        }
    }

    pub fn push(&mut self, entry: QifEntry) {
        if !entry.is_empty() {
            self.entries.push(entry);
        }
    }
}

impl fmt::Display for QifFile {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut hat_separated = String::new();

        for entry in &self.entries {
            hat_separated.push_str("\n");
            hat_separated.push_str(&entry.to_string());
            hat_separated.push_str("\n^");
        }

        write!(f, "{}{}", self.header, hat_separated)
    }
}

pub struct QifEntry {
    date: String,
    amount: String,
    description: String
}

const DATE_PREFIX: &str = "D";
const AMOUNT_PREFIX: &str = "T";
const DESCRIPTION_PREFIX: &str = "M";

#[derive(Debug)]
pub enum QifParsingError {
    MissingDate,
    MissingAmount,
    MissingDescription
}

impl fmt::Display for QifParsingError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:?}", self)
    }
}

impl Error for QifParsingError {}

impl QifEntry {
    pub fn new(lines: &Vec<String>) -> Result<QifEntry, QifParsingError> {
        let date = lines.iter().find(|l| l.starts_with(DATE_PREFIX));
        let amount = lines.iter().find(|l| l.starts_with(AMOUNT_PREFIX));
        let description = lines.iter().find(|l| l.starts_with(DESCRIPTION_PREFIX));
        match (date, amount, description) {
            (Some(date), Some(amount), Some(description)) => Ok(QifEntry {
                date: date.chars().skip(1).collect(),
                amount: amount.chars().skip(1).collect(),
                description: description.chars().skip(1).collect()
            }),
            (None, _, _) => Err(QifParsingError::MissingDate),
            (_, None, _) => Err(QifParsingError::MissingAmount),
            (_, _, None) => Err(QifParsingError::MissingDescription),
        }
    }

    pub fn is_empty(&self) -> bool {
        self.amount == String::from("0")
    }

    pub fn clean_description(&self) -> String {
        let replaced_date = replace_date(&self.description);
        replace_common(&replaced_date)
    }
}

impl fmt::Display for QifEntry {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}{}\n{}{}\n{}{}",
               DATE_PREFIX, self.date,
               AMOUNT_PREFIX, self.amount,
               DESCRIPTION_PREFIX, self.clean_description()
        )
    }
}

fn replace_date(text: &str) -> String {
    lazy_static! {
        static ref DATE_REGEX: Regex = Regex::new(r"(?i)(\d{2} )?(JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)( \d{4})?").unwrap();
    }
    DATE_REGEX.replace_all(text, "").trim().to_string()
}

fn replace_common(text: &str) -> String {
    lazy_static! {
        static ref COMMON_NAMES: Vec<(Regex, &'static str)> = vec!(
            (Regex::new(r"(?i)(pick n pay|pnp)").unwrap(), "Pick n Pay"),
            (Regex::new(r"(?i)checkers").unwrap(), "Checkers"),
            (Regex::new(r"(?i)WOOLWORTHS").unwrap(), "Woolworths"),
            (Regex::new(r"(?i)clicks").unwrap(), "Clicks"),
            (Regex::new(r"(?i)spar").unwrap(), "Spar"),
            (Regex::new(r"(?i)Crazy store").unwrap(), "Crazy Store"),
            (Regex::new(r"^PNA").unwrap(), "PNA"),
            (Regex::new(r"(?i)sahl").unwrap(), "SA Home Loans"),
            (Regex::new(r"(?i)gautrain").unwrap(), "Gautrain"),
            (Regex::new(r"(?i)BANK YOUR CHANGE DEBI").unwrap(), "TO SAVINGS POCKET"),
            (Regex::new(r"(?i)AFRIHOST").unwrap(), "Afrihost"),
            (Regex::new(r"(?i)DIALDIRECT").unwrap(), "Dialdirect"),
            (Regex::new(r"(?i)STEERS").unwrap(), "Steers"),
            (Regex::new(r"(?i)CELL C").unwrap(), "Cell C"),
            (Regex::new(r"(?i)ELECTRICITY").unwrap(), "Electricity"),
            (Regex::new(r"(?i)(COUNTRY VIEW|STAR STOP|Shell|Sasol)").unwrap(), "Petrol"),
            (Regex::new(r"(?i)kung ?-?fu").unwrap(), "Kungfu Kitchen"),
        );
    }
    COMMON_NAMES.iter().fold(
        text, |acc, next| if next.0.is_match(acc) {next.1} else {acc}
    ).to_string()
}