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//! This module contains the parser to turn a byte slice into a `TransientTweet`
use nom::IResult;
use nom::IResult::{Done};
use nom::digit;
use types::{TransientTweet, Tweet, TweetQuoted};
use std::str::from_utf8;
use core::char::from_u32;
use types::convert;

fn lookup(slice: &[u8]) -> char {
    if slice == b"amp" {
        '&'
    }
    else {
        '<'
    }
}

fn join(opt: Option<Option<TweetQuoted>>) -> Option<TweetQuoted> {
    if opt.is_some() {
        opt.unwrap()
    }
    else {
        None
    }
}

fn char_vector_to_string(v: Vec<char>) -> String {
    let s:String = v.into_iter().collect();
    s
}

// TODO consider making this a method?
fn replace_unicode(string: &str) -> char {
    let num_int = u32::from_str_radix(&string[0..4], 16)
        .expect("Failed to parses hexadecimal");
    if let Some(return_value) = from_u32(num_int) {
        return_value 
    }
    else {
        '�'
    }
}
named!(inner_char<&[u8], char>, alt!(html_char | unicode_char | newline_char | special_char | none_of!("\\\"")));
named!(prefield<&[u8], Vec<char> >, many0!(inner_char)); 
named!(field<&[u8], Vec<char> >, delimited!(char!('"'), prefield, char!('"')));
named!(int_field, take_until!(","));
named!(text_value<&[u8], Vec <char> >,
  do_parse!(
    take_until!("\"text\"") >>
    tag!("\"text\":") >>
    value: field >>
    (value)
  )
);
named!(tweet_id,
  do_parse!(
    take_until!("\"id\":") >>
    tag!("\"id\":") >>
    num_value: take_until!(",") >>
    (num_value)
  )
);
named!(html_char<&[u8], char>,
  do_parse!(
    char!('&') >>
    value: take_until!(";") >>
    char!(';') >>
    (lookup(value))
  )
);
//TODO make this parse
named!(skip_quote_status_entity<&[u8], TweetQuoted >,
  do_parse!(
    tag!(",\"quoted_status") >>
    value: step_parse_quoted >> // retweets_value >>
    (value)
  )
);
named!(skip_quote_status<&[u8], Option<TweetQuoted> >,
  do_parse!(
    take_until!("\"is_quote_status\"") >>
    tag!("\"is_quote_status\":true") >>
    take!(1) >> 
    take_until!("\"quoted_status_id_str\"") >>
    tag!("\"quoted_status_id_str\":") >>
    delimited!(char!('"'), digit, char!('"')) >>
    value: opt!(skip_quote_status_entity) >>
    (value)
  )
);
named!(unicode_char<&[u8], char>,
  do_parse!(
    tag!("\\u") >>
    num: take!(4) >>
    (replace_unicode(from_utf8(num).unwrap()))
  )
);
named!(special_char<&[u8], char>,
  do_parse!(
    char!('\\') >>
    value: take!(1) >>
    (from_utf8(value).unwrap().chars().next().unwrap())
  )
);
named!(newline_char<&[u8], char>,
  do_parse!(
    tag!("\\n") >>
    ('\n')
  )
);
named!(name_value<&[u8], Vec<char> >,
  do_parse!(
    take_until!("\"name\"") >>
    tag!("\"name\":") >>
    value: field >>
    (value)
  )
);
named!(retweets_value,
  do_parse!(
    take_until!("\"retweet_count\"") >>
    tag!("\"retweet_count\":") >>
    value: int_field >>
    (value)
  )
);
named!(media_id,
  do_parse!(
    take_until!("\"media_id\"") >>
    tag!("\"media_id\":") >>
    value: int_field >>
    (value)
  )
);
named!(favorites_value,
  do_parse!(
    take_until!("\"favorite_count\"") >>
    tag!("\"favorite_count\":") >>
    value: int_field >>
    (value)
  )
);
named!(skip_mentions<&[u8], () >,
  do_parse!(
    take_until!("\"user_mentions\"") >>
    tag!("\"user_mentions\":") >>
    alt!(tag!("[]")
      | delimited!(tag!("["), take_until!("}]") , tag!("}]"))) >> 
    ()
  )
);
named!(step_parse_quoted<&[u8], TweetQuoted >,
  do_parse!(
    get_text: text_value >>
    skip_mentions >>
    get_name: name_value >>
    opt!(skip_quote_status) >>
    retweets_value >>
    (TweetQuoted{text: char_vector_to_string(get_text), name: char_vector_to_string(get_name)})
  )
);
named!(step_parse<&[u8], TransientTweet >,
  do_parse!(
    get_id: tweet_id >>
    get_text: text_value >>
    skip_mentions >>
    get_name: name_value >>
    quote: opt!(skip_quote_status) >>
    get_retweets: retweets_value >>
    get_favorites: favorites_value >>
    (TransientTweet{text: char_vector_to_string(get_text), name: char_vector_to_string(get_name), quoted: join(quote), retweets: get_retweets, favorites: get_favorites, id: get_id })
  )
);
named!(big_parser<&[u8], Vec<TransientTweet> > , many0!(step_parse)); 

/// Parse a slice of bytes as a vector of tweets. The input should be the JSON-formatted response
/// sent back by twitter. You can look at an example response
/// [here](https://dev.twitter.com/rest/reference/get/statuses/user_timeline).
///
/// The function returns an `IResult`, so you can pattern match to use it. 
pub fn parse_tweets(str_in: &[u8]) -> IResult<&[u8], Vec<TransientTweet>> {
    big_parser(str_in)
}

/// Return a `Tweet`, suitable for libraries etc.
pub fn parse_tweets_string(str_in: &[u8]) -> Option<Vec<Tweet>> {
    if let Done(_,val) = parse_tweets(str_in) {
        Some(val.into_iter().map(convert).collect())
    }
    else {
        None
    }

}

pub fn get_media_id(str_in: &[u8]) -> IResult<&[u8], &[u8]> {
    media_id(str_in)
}