1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148

use std::collections::BTreeMap;
use std::fmt;
use std::fmt::{Debug, Display};
use std::iter::FromIterator;

use itertools::Itertools;
use lazy_init::Lazy;

/// Token features.
///
/// In the CoNLL-X specification, these are morphological features of the
/// token. Typically, the features are a list or a key-value mapping.
pub struct Features {
    features: String,
    feature_map: Lazy<BTreeMap<String, Option<String>>>,
}

impl Features {
    /// Create features from a string. The casual format uses key-value
    /// pairs that are separated by a vertical bar (`|`) and keys and
    /// values using a colon (`:`). Arbitrary strings will also be accepted,
    /// however they will not give a nice feature-value mapping when using
    /// `as_map`.
    pub fn from_string<S>(s: S) -> Self
    where
        S: Into<String>,
    {
        Features {
            features: s.into(),
            feature_map: Lazy::new(),
        }
    }

    pub fn from_iter<I, S>(iter: I) -> Self
    where
        I: IntoIterator<Item = (S, Option<S>)>,
        S: Into<String> + Ord + Sync,
    {
        let feature_map =
            BTreeMap::from_iter(iter.into_iter().map(|(k, v)| (k.into(), v.map(Into::into))));
        let features = map_to_string(&feature_map);

        let lazy_feature_map = Lazy::new();
        lazy_feature_map.get_or_create(|| feature_map);

        Features {
            features,
            feature_map: lazy_feature_map,
        }
    }

    /// Get the features field as a key-value mapping. This assumes that
    /// the key-value pairs are separed using a vertical bar (`|`) and keys
    /// and values using a colon (`:`). If the value is absent, corresponding
    /// value in the mapping is `None`.
    ///
    /// The feature map is constructed lazily:
    ///
    /// * If `as_map` is never called, the feature map is never created.
    /// * If `as_map` is called once or more, the feature map is only created
    ///   once.
    pub fn as_map(&self) -> &BTreeMap<String, Option<String>> {
        self.feature_map.get_or_create(|| self.as_map_eager())
    }

    /// Get the features field.
    pub fn as_str(&self) -> &str {
        self.features.as_ref()
    }

    fn as_map_eager(&self) -> BTreeMap<String, Option<String>> {
        let mut features = BTreeMap::new();

        for fv in self.features.split('|') {
            let mut iter = fv.split(':');
            if let Some(k) = iter.next() {
                let v = iter.next().map(|s| s.to_owned());
                features.insert(k.to_owned(), v.to_owned());
            }
        }

        features
    }
}

impl Clone for Features {
    fn clone(&self) -> Self {
        Features {
            features: self.features.clone(),
            feature_map: Lazy::new(),
        }
    }
}

impl Debug for Features {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Features {{ features: {} }}", self.features)
    }
}

impl Display for Features {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(self.features.as_ref())
    }
}

impl PartialEq for Features {
    fn eq(&self, other: &Features) -> bool {
        self.features.eq(&other.features)
    }
}

fn map_to_string(feature_map: &BTreeMap<String, Option<String>>) -> String {
    feature_map
        .iter()
        .map(|(k, v)| match *v {
            Some(ref v) => format!("{}:{}", k, v),
            None => k.to_owned(),
        })
        .join("|")
}

#[cfg(test)]
mod tests {
    use std::collections::BTreeMap;

    use super::Features;

    #[test]
    quickcheck! {
        fn from_iter(feature_map: BTreeMap<String, Option<String>>) -> bool{
            &feature_map == Features::from_iter(feature_map.clone()).as_map()
        }
    }

    #[test]
    fn from_iter_as_string() {
        let feature_map = btreemap!{
            "feature2" => Some("y"),
            "feature3" => None,
            "feature1" => Some("x")
        };

        let features = Features::from_iter(feature_map);

        assert_eq!(features.as_str(), "feature1:x|feature2:y|feature3");
    }
}