predicates/str/
difference.rs

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
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
// Copyright (c) 2018 The predicates-rs Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::borrow;
use std::fmt;

use crate::reflection;
use crate::Predicate;

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum DistanceOp {
    Similar,
    Different,
}

impl DistanceOp {
    fn eval(self, limit: i32, distance: i32) -> bool {
        match self {
            DistanceOp::Similar => distance <= limit,
            DistanceOp::Different => limit < distance,
        }
    }
}

/// Predicate that diffs two strings.
///
/// This is created by the `predicate::str::similar`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct DifferencePredicate {
    orig: borrow::Cow<'static, str>,
    split: borrow::Cow<'static, str>,
    distance: i32,
    op: DistanceOp,
}

impl DifferencePredicate {
    /// The split used when identifying changes.
    ///
    /// Common splits include:
    /// - `""` for char-level.
    /// - `" "` for word-level.
    /// - `"\n"` for line-level.
    ///
    /// Default: `"\n"`
    ///
    /// # Examples
    ///
    /// ```
    /// use predicates::prelude::*;
    ///
    /// let predicate_fn = predicate::str::similar("Hello World").split(" ");
    /// assert_eq!(true, predicate_fn.eval("Hello World"));
    /// ```
    pub fn split<S>(mut self, split: S) -> Self
    where
        S: Into<borrow::Cow<'static, str>>,
    {
        self.split = split.into();
        self
    }

    /// The maximum allowed edit distance.
    ///
    /// Default: `0`
    ///
    /// # Examples
    ///
    /// ```
    /// use predicates::prelude::*;
    ///
    /// let predicate_fn = predicate::str::similar("Hello World!").split("").distance(1);
    /// assert_eq!(true, predicate_fn.eval("Hello World!"));
    /// assert_eq!(true, predicate_fn.eval("Hello World"));
    /// assert_eq!(false, predicate_fn.eval("Hello World?"));
    /// ```
    pub fn distance(mut self, distance: i32) -> Self {
        self.distance = distance;
        self
    }
}

impl Predicate<str> for DifferencePredicate {
    fn eval(&self, edit: &str) -> bool {
        let change = difference::Changeset::new(&self.orig, edit, &self.split);
        self.op.eval(self.distance, change.distance)
    }

    fn find_case<'a>(&'a self, expected: bool, variable: &str) -> Option<reflection::Case<'a>> {
        let change = difference::Changeset::new(&self.orig, variable, &self.split);
        let result = self.op.eval(self.distance, change.distance);
        if result == expected {
            Some(
                reflection::Case::new(Some(self), result)
                    .add_product(reflection::Product::new("actual distance", change.distance))
                    .add_product(reflection::Product::new("diff", change)),
            )
        } else {
            None
        }
    }
}

impl reflection::PredicateReflection for DifferencePredicate {
    fn parameters<'a>(&'a self) -> Box<dyn Iterator<Item = reflection::Parameter<'a>> + 'a> {
        let params = vec![reflection::Parameter::new("original", &self.orig)];
        Box::new(params.into_iter())
    }
}

impl fmt::Display for DifferencePredicate {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self.op {
            DistanceOp::Similar => write!(f, "var - original <= {}", self.distance),
            DistanceOp::Different => write!(f, "{} < var - original", self.distance),
        }
    }
}

/// Creates a new `Predicate` that diffs two strings.
///
/// # Examples
///
/// ```
/// use predicates::prelude::*;
///
/// let predicate_fn = predicate::str::diff("Hello World");
/// assert_eq!(false, predicate_fn.eval("Hello World"));
/// assert_eq!(true, predicate_fn.eval("Goodbye World"));
/// ```
pub fn diff<S>(orig: S) -> DifferencePredicate
where
    S: Into<borrow::Cow<'static, str>>,
{
    DifferencePredicate {
        orig: orig.into(),
        split: "\n".into(),
        distance: 0,
        op: DistanceOp::Different,
    }
}

/// Creates a new `Predicate` that checks strings for how similar they are.
///
/// # Examples
///
/// ```
/// use predicates::prelude::*;
///
/// let predicate_fn = predicate::str::similar("Hello World");
/// assert_eq!(true, predicate_fn.eval("Hello World"));
/// assert_eq!(false, predicate_fn.eval("Goodbye World"));
/// ```
pub fn similar<S>(orig: S) -> DifferencePredicate
where
    S: Into<borrow::Cow<'static, str>>,
{
    DifferencePredicate {
        orig: orig.into(),
        split: "\n".into(),
        distance: 0,
        op: DistanceOp::Similar,
    }
}