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

/*
 * Copyright 2018 The Starlark in Rust Authors.
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

use std::cell::Ref;
use std::cell::RefCell;
use std::cell::RefMut;
use std::ops::Deref;
use std::ops::DerefMut;

use either::Either;

use crate::coerce::coerce;
use crate::typing::Ty;
use crate::values::dict::value::DictGen;
use crate::values::dict::value::FrozenDictData;
use crate::values::dict::Dict;
use crate::values::type_repr::StarlarkTypeRepr;
use crate::values::FrozenValue;
use crate::values::UnpackValue;
use crate::values::Value;
use crate::values::ValueError;
use crate::values::ValueLike;

/// Borrowed `Dict`.
pub struct DictRef<'v> {
    pub(crate) aref: Either<Ref<'v, Dict<'v>>, &'v Dict<'v>>,
}

/// Mutably borrowed `Dict`.
pub struct DictMut<'v> {
    pub(crate) aref: RefMut<'v, Dict<'v>>,
}

/// Reference to frozen `Dict`.
pub struct FrozenDictRef {
    dict: &'static FrozenDictData,
}

impl<'v> DictRef<'v> {
    /// Downcast the value to a dict.
    pub fn from_value(x: Value<'v>) -> Option<DictRef<'v>> {
        if x.unpack_frozen().is_some() {
            x.downcast_ref::<DictGen<FrozenDictData>>()
                .map(|x| DictRef {
                    aref: Either::Right(coerce(&x.0)),
                })
        } else {
            let ptr = x.downcast_ref::<DictGen<RefCell<Dict<'v>>>>()?;
            Some(DictRef {
                aref: Either::Left(ptr.0.borrow()),
            })
        }
    }
}

impl<'v> DictMut<'v> {
    /// Downcast the value to a mutable dict reference.
    #[inline]
    pub fn from_value(x: Value<'v>) -> anyhow::Result<DictMut> {
        #[derive(thiserror::Error, Debug)]
        #[error("Value is not dict, value type: `{0}`")]
        struct NotDictError(&'static str);

        #[cold]
        #[inline(never)]
        fn error<'v>(x: Value<'v>) -> anyhow::Error {
            if x.downcast_ref::<DictGen<FrozenDictData>>().is_some() {
                ValueError::CannotMutateImmutableValue.into()
            } else {
                NotDictError(x.get_type()).into()
            }
        }

        let ptr = x.downcast_ref::<DictGen<RefCell<Dict<'v>>>>();
        match ptr {
            None => Err(error(x)),
            Some(ptr) => match ptr.0.try_borrow_mut() {
                Ok(x) => Ok(DictMut { aref: x }),
                Err(_) => Err(ValueError::MutationDuringIteration.into()),
            },
        }
    }
}

impl FrozenDictRef {
    /// Downcast to frozen dict.
    pub fn from_frozen_value(x: FrozenValue) -> Option<FrozenDictRef> {
        x.downcast_ref::<DictGen<FrozenDictData>>()
            .map(|x| FrozenDictRef { dict: &x.0 })
    }

    /// Get value by a string key.
    pub fn get_str(&self, key: &str) -> Option<FrozenValue> {
        self.dict.get_str(key)
    }

    /// Iterate over dict entries.
    pub fn iter(&self) -> impl ExactSizeIterator<Item = (FrozenValue, FrozenValue)> {
        self.dict.iter()
    }
}

impl<'v> Deref for DictRef<'v> {
    type Target = Dict<'v>;

    fn deref(&self) -> &Self::Target {
        &self.aref
    }
}

impl<'v> Deref for DictMut<'v> {
    type Target = Dict<'v>;

    fn deref(&self) -> &Self::Target {
        &self.aref
    }
}

impl<'v> DerefMut for DictMut<'v> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.aref
    }
}

impl<'v> StarlarkTypeRepr for DictRef<'v> {
    fn starlark_type_repr() -> Ty {
        Dict::<'v>::starlark_type_repr()
    }
}

impl<'v> UnpackValue<'v> for DictRef<'v> {
    fn expected() -> String {
        "dict".to_owned()
    }

    fn unpack_value(value: Value<'v>) -> Option<DictRef<'v>> {
        DictRef::from_value(value)
    }
}