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

//! This mutation is chosen when the element mutator is a “unit” mutator,
//! meaning that it can only produce a single value. In this case, the
//! vector mutator’s role is simply to choose a length.
//!
//! For example, if we have:
//! ```
//! use fuzzcheck::{Mutator, DefaultMutator};
//! use fuzzcheck::mutators::vector::VecMutator;
//!
//! let m /* : impl Mutator<Vec<()>> */ = VecMutator::new(<()>::default_mutator(), 2..=5, true);
//! ```
//! Then the values that `m` can produce are only:
//! ```txt
//! [(), ()]
//! [(), (), ()]
//! [(), (), (), ()]
//! [(), (), (), (), ()]
//! ```
//! and nothing else.
//!
//! We can detect if the element mutator is a unit mutator by calling
//! `m.global_search_space_complexity()`. If the complexity is `0.0`, then the
//! mutator is only capable of producing a single value.

use super::VecMutator;
use crate::mutators::mutations::{Mutation, RevertMutation};
use crate::{Mutator, SubValueProvider};

pub struct OnlyChooseLength;

#[derive(Clone)]
pub struct OnlyChooseLengthStep {
    length: usize,
}
#[derive(Clone)]
pub struct OnlyChooseLengthRandomStep;

pub struct ConcreteOnlyChooseLength {
    length: usize,
}
pub struct RevertOnlyChooseLength<T> {
    replace_by: Vec<T>,
}

impl<T, M> RevertMutation<Vec<T>, VecMutator<T, M>> for RevertOnlyChooseLength<T>
where
    T: Clone + 'static,
    M: Mutator<T>,
{
    #[no_coverage]
    fn revert(
        mut self,
        _mutator: &VecMutator<T, M>,
        value: &mut Vec<T>,
        _cache: &mut <VecMutator<T, M> as Mutator<Vec<T>>>::Cache,
    ) {
        std::mem::swap(value, &mut self.replace_by);
    }
}

impl<T, M> Mutation<Vec<T>, VecMutator<T, M>> for OnlyChooseLength
where
    T: Clone + 'static,
    M: Mutator<T>,
{
    type RandomStep = OnlyChooseLengthRandomStep;
    type Step = OnlyChooseLengthStep;
    type Concrete<'a> = ConcreteOnlyChooseLength;
    type Revert = RevertOnlyChooseLength<T>;
    #[no_coverage]
    fn default_random_step(&self, mutator: &VecMutator<T, M>, _value: &Vec<T>) -> Option<Self::RandomStep> {
        if mutator.m.global_search_space_complexity() <= 0.0 {
            Some(OnlyChooseLengthRandomStep)
        } else {
            None
        }
    }
    #[no_coverage]
    fn random<'a>(
        mutator: &VecMutator<T, M>,
        _value: &Vec<T>,
        _cache: &<VecMutator<T, M> as Mutator<Vec<T>>>::Cache,
        _random_step: &Self::RandomStep,
        max_cplx: f64,
    ) -> Self::Concrete<'a> {
        let cplx_element = mutator.m.min_complexity();
        assert_eq!(cplx_element, mutator.m.max_complexity(), "A mutator of type {:?} has a global_search_space_complexity of 0.0 (indicating that it can produce only one value), but its min_complexity() is different than its max_complexity(), which is a contradiction.", std::any::type_name::<M>());

        let cplx_element = if mutator.inherent_complexity {
            // then each element adds an additional 1.0 of complexity
            1.0 + cplx_element
        } else {
            cplx_element
        };

        let upperbound = std::cmp::max(
            std::cmp::min(*mutator.len_range.end(), ((max_cplx - 1.0) / cplx_element) as usize),
            *mutator.len_range.start(),
        );
        ConcreteOnlyChooseLength {
            length: mutator.rng.usize(*mutator.len_range.start()..=upperbound),
        }
    }
    #[no_coverage]
    fn default_step(
        &self,
        mutator: &VecMutator<T, M>,
        _value: &Vec<T>,
        _cache: &<VecMutator<T, M> as Mutator<Vec<T>>>::Cache,
    ) -> Option<Self::Step> {
        if mutator.m.global_search_space_complexity() <= 0.0 {
            Some(OnlyChooseLengthStep {
                length: *mutator.len_range.start(),
            })
        } else {
            None
        }
    }
    #[no_coverage]
    fn from_step<'a>(
        mutator: &VecMutator<T, M>,
        _value: &Vec<T>,
        _cache: &<VecMutator<T, M> as Mutator<Vec<T>>>::Cache,
        step: &'a mut Self::Step,
        _subvalue_provider: &dyn SubValueProvider,
        max_cplx: f64,
    ) -> Option<Self::Concrete<'a>> {
        let cplx_element = mutator.m.min_complexity();
        if step.length <= *mutator.len_range.end()
            && mutator.complexity_from_inner(cplx_element * step.length as f64, step.length) < max_cplx
        {
            let x = ConcreteOnlyChooseLength { length: step.length };
            step.length += 1;
            Some(x)
        } else {
            None
        }
    }
    #[no_coverage]
    fn apply<'a>(
        mutation: Self::Concrete<'a>,
        mutator: &VecMutator<T, M>,
        value: &mut Vec<T>,
        _cache: &mut <VecMutator<T, M> as Mutator<Vec<T>>>::Cache,
        _subvalue_provider: &dyn SubValueProvider,
        _max_cplx: f64,
    ) -> (Self::Revert, f64) {
        let (el, el_cplx) = mutator.m.random_arbitrary(0.0);
        let mut value_2 = std::iter::repeat(el).take(mutation.length).collect();
        std::mem::swap(value, &mut value_2);
        let cplx = mutator.complexity_from_inner(el_cplx * mutation.length as f64, mutation.length);
        (RevertOnlyChooseLength { replace_by: value_2 }, cplx)
    }
}