pub(crate) mod padding;
pub(crate) mod ngrams;

use padding::Padder;

/// Returns a padded sequence of items before ngram extraction.
///
/// sequence: sequence of items to pad, in the form of an Iterator of string slices.
/// pad_left: if set to true, prepends a padding symbol to the sentence
/// left_pad_symbol: the padding symbol to prepend
/// pad_right: if set to true, appends a padding symbol after the sentence
/// right_pad_symbol: the padding symbol to append
/// n: the n in n-grams; so for bigrams set to 2, etc
pub fn pad_sequence<'a>(sentence: impl Iterator<Item=&'a &'a str> + 'a, pad_left: bool, left_pad_symbol: &'a &'a str, pad_right: bool, right_pad_symbol: &'a &'a str, n: usize) -> impl Iterator<Item=&'a &'a str> {
    Padder::new(Box::new(sentence), pad_left, left_pad_symbol, pad_right, right_pad_symbol, n)
}

/// Returns a padded sequence of items before ngram extraction, left-padding only. Convenience function that prevents useless arguments
/// sequence: sequence of items to pad, in the form of an Iterator of string slices.
/// left_pad_symbol: the padding symbol to prepend
/// n: the n in n-grams; so for bigrams set to 2, etc
pub fn pad_sequence_left<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a, left_pad_symbol: &'a &'a str, n: usize) -> impl Iterator<Item=&'a &'a str> {
    Padder::new(Box::new(sequence), true, left_pad_symbol, false, &"", n)
}

/// Returns a padded sequence of items before ngram extraction, right-padding only. Convenience function that prevents useless arguments
///
/// sequence: sequence of items to pad, in the form of an Iterator of string slices.
/// pad_right: if set to true, appends a padding symbol after the sentence
/// right_pad_symbol: the padding symbol to append
/// n: the n in n-grams; so for bigrams set to 2, etc
pub fn pad_sequence_right<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a, right_pad_symbol: &'a &'a str, n: usize) -> impl Iterator<Item=&'a &'a str> + 'a {
    Padder::new(Box::new(sequence), false, &"", true, right_pad_symbol, n)
}

/// Return the ngrams generated from a sequence of items, as an iterator.
///
/// sequence: the sequence items in the form of an Iterator over &&str
/// use like:
/// ```
/// let sequence = vec!["a", "b", "c"];
/// let mut bigrams = rltk::util::ngrams(sequence.iter(), 2);
///
/// let bigram1 = vec!["a", "b"];
/// let bigram2 = vec!["b", "c"];
/// let expected = vec![bigram1.iter(), bigram2.iter()];
///
/// for (mut left_outer,mut right_outer) in bigrams.zip(expected.into_iter()){
///     for (left_inner,right_inner) in left_outer.zip(right_outer){
///         assert_eq!(left_inner, right_inner);
///     }
/// }
/// ```
///
pub fn ngrams<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a, n: usize) -> impl Iterator<Item=impl Iterator<Item=&'a &'a str> + 'a> + 'a {
    ngrams::NGramSequenceIter::new(sequence, n)
}

pub fn bigrams<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a) -> impl Iterator<Item=impl Iterator<Item=&'a &'a str> + 'a> + 'a {
    ngrams::NGramSequenceIter::new(sequence, 2)
}

pub fn trigrams<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a) -> impl Iterator<Item=impl Iterator<Item=&'a &'a str> + 'a> + 'a {
    ngrams::NGramSequenceIter::new(sequence, 3)
}

pub fn everygrams<'a>(sequence: impl Iterator<Item=&'a &'a str> + 'a, n: usize) -> impl Iterator<Item=Box<dyn Iterator<Item=&'a &'a str> + 'a>> + 'a {
    ngrams::EveryGramSequenceIter::everygrams(sequence, n)
}

pub fn flatten<'a>(ngrams: impl Iterator<Item=Box<dyn Iterator<Item=&'a &'a str> + 'a>> + 'a) -> impl Iterator<Item=&'a &'a str> + 'a {
    ngrams::FlatteningIter::new(ngrams)
}

#[cfg(test)]
mod tests {
    use crate::lm::preprocessing::pad_both_ends;
    use super::*;
    use crate::test::*;

    #[test]
    fn test_pad_both_ends_default_n2() {
        let text = vec!["a", "b", "c"];
        let padded = pad_sequence(text.iter(), true, &"<s>", true, &"</s>", 2);
        should_be_equal_lists(padded, vec!["<s>", "a", "b", "c", "</s>"]);
    }

    #[test]
    fn test_pad_left() {
        let text = vec!["a", "b", "c"];
        let padded = pad_sequence_left(text.iter(), &"<s>", 2);
        should_be_equal_lists(padded, vec!["<s>", "a", "b", "c"]);
    }

    #[test]
    fn test_pad_right() {
        let text = vec!["a", "b", "c"];
        let padded = pad_sequence_right(text.iter(), &"</s>", 2);

        should_be_equal_lists(padded, vec!["a", "b", "c", "</s>"]);
    }

    #[test]
    fn test_pad_both_ends_default_n_eq_3() {
        let text = vec!["a", "b", "c"];
        let padded = pad_sequence(text.iter(), true, &"<s>", true, &"</s>", 3);
        should_be_equal_lists(padded, vec!["<s>", "<s>", "a", "b", "c", "</s>", "</s>"]);
    }

    #[test]
    fn test_pad_both_ends_non_default_symbols() {
        let text = vec!["a", "b", "c"];
        let padded = pad_sequence(text.iter(), true, &"left", true, &"right", 2);

        should_be_equal_lists(padded, vec!["left", "a", "b", "c", "right"]);
    }

    #[test]
    fn test_bigrams() {
        let sequence = vec!["a", "b", "c", "d"];
        let mut bigrams = ngrams(sequence.iter(), 2);
        let bigram1 = vec!["a", "b"];
        let bigram2 = vec!["b", "c"];
        let bigram3 = vec!["c", "d"];
        let expected = vec![bigram1.iter(), bigram2.iter(), bigram3.iter()];

        should_be_equal_list_of_lists(&mut bigrams, expected)
    }

    #[test]
    fn test_trigrams() {
        let sequence = vec!["a", "b", "c", "d", "e"];
        let mut bigrams = ngrams(sequence.iter(), 3);
        let trigram1 = vec!["a", "b", "c"];
        let trigram2 = vec!["b", "c", "d"];
        let trigram3 = vec!["c", "d", "e"];
        let expected = vec![trigram1.iter(), trigram2.iter(), trigram3.iter()];

        should_be_equal_list_of_lists(&mut bigrams, expected)
    }

    #[test]
    fn test_bigrams_n_gt_len() {
        let sequence = vec!["a"];
        let mut bigrams = ngrams(sequence.iter(), 2);
        assert!(bigrams.next().is_none());
    }

    #[test]
    fn test_bigrams_empty_sequence() {
        let sequence = vec![];
        let mut bigrams = ngrams(sequence.iter(), 10);
        assert!(bigrams.next().is_none());
    }

    #[test]
    fn test_bigrams_n_eq_len() {
        let sequence = vec!["a", "b"];
        let mut bigrams = ngrams(sequence.iter(), 2);
        let bigram1 = vec!["a", "b"];
        let expected = vec![bigram1.iter()];

        should_be_equal_list_of_lists(&mut bigrams, expected);
    }


    #[test]
    fn test_everygrams_n_eq_2() {
        let sequence = vec!["a", "b", "c", "d"];
        let mut grams = everygrams(sequence.iter(), 2);
        // let gram1 = vec!["a"];
        // let gram2 = vec!["a", "b"];
        // let gram3 = vec!["b"];
        // let gram4 = vec!["b", "c"];
        // let gram5 = vec!["c"];
        // let gram6 = vec!["c", "d"];
        // let gram7 = vec!["d"];
        // let expected = vec![gram1.iter(), gram2.iter(), gram3.iter(), gram4.iter(), gram5.iter(), gram6.iter(), gram7.iter()];

        for i in grams{
            for j in i{
                print!("{},",j);
            }
            println!();
        }
        // should_be_equal_list_of_lists(&mut bigrams, expected);
    }

    #[test]
    fn test_everygrams_n_eq_3() {
        let sequence = vec!["a", "b", "c", "d", "e"];
        let mut bigrams = everygrams(sequence.iter(), 3);

        let gram1 = vec!["a"];
        let gram2 = vec!["a", "b"];
        let gram3 = vec!["a", "b", "c"];
        let gram4 = vec!["b"];
        let gram5 = vec!["b", "c"];
        let gram6 = vec!["b", "c", "d"];
        let gram7 = vec!["c"];
        let gram8 = vec!["c", "d"];
        let gram9 = vec!["c", "d", "e"];
        let gram10 = vec!["d"];
        let gram11 = vec!["d", "e"];
        let gram12 = vec!["e"];

        let expected = vec![gram1.iter(), gram2.iter(), gram3.iter(), gram4.iter(), gram5.iter(), gram6.iter(), gram7.iter(), gram8.iter(), gram9.iter(), gram10.iter(), gram11.iter(), gram12.iter()];

        should_be_equal_list_of_lists(&mut bigrams, expected);
    }

    #[test]
    fn test_flatten() {
        let sequence = vec!["a", "b", "c", "d", "e"];
        let expected = vec!["a", "a", "b", "a", "b", "c", "b", "b", "c", "b", "c", "d", "c", "c", "d", "c", "d", "e"];

        should_be_equal_lists(flatten(everygrams(sequence.iter(), 3)), expected);
    }

    #[test]
    fn example() {
        let text = vec![vec!["a", "b", "c"], vec!["a", "c", "d", "c", "e", "f"]];
        let result: Vec<&&str> = text.iter().map(|sent|pad_both_ends(sent.iter(),2)).flatten().collect();
        println!("{:?}", result);
    }
}