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
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
#![allow(clippy::wrong_self_convention)]

use std::iter::FromIterator;
use std::ops::{Deref, DerefMut};
use std::result::Result as StdResult;

use crate::error::Result;
use crate::lua::Lua;
use crate::value::{FromLua, FromLuaMulti, MultiValue, Nil, ToLua, ToLuaMulti};

/// Result is convertible to `MultiValue` following the common Lua idiom of returning the result
/// on success, or in the case of an error, returning `nil` and an error message.
impl<'lua, T: ToLua<'lua>, E: ToLua<'lua>> ToLuaMulti<'lua> for StdResult<T, E> {
    #[inline]
    fn to_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
        let mut result = MultiValue::new_or_cached(lua);
        match self {
            Ok(v) => result.push_front(v.to_lua(lua)?),
            Err(e) => {
                result.push_front(e.to_lua(lua)?);
                result.push_front(Nil);
            }
        }
        Ok(result)
    }
}

impl<'lua, T: ToLua<'lua>> ToLuaMulti<'lua> for T {
    #[inline]
    fn to_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
        let mut v = MultiValue::new_or_cached(lua);
        v.push_front(self.to_lua(lua)?);
        Ok(v)
    }
}

impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for T {
    #[inline]
    fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
        let res = T::from_lua(values.pop_front().unwrap_or(Nil), lua);
        lua.cache_multivalue(values);
        res
    }
}

impl<'lua> ToLuaMulti<'lua> for MultiValue<'lua> {
    #[inline]
    fn to_lua_multi(self, _: &'lua Lua) -> Result<MultiValue<'lua>> {
        Ok(self)
    }
}

impl<'lua> FromLuaMulti<'lua> for MultiValue<'lua> {
    #[inline]
    fn from_lua_multi(values: MultiValue<'lua>, _: &'lua Lua) -> Result<Self> {
        Ok(values)
    }
}

/// Wraps a variable number of `T`s.
///
/// Can be used to work with variadic functions more easily. Using this type as the last argument of
/// a Rust callback will accept any number of arguments from Lua and convert them to the type `T`
/// using [`FromLua`]. `Variadic<T>` can also be returned from a callback, returning a variable
/// number of values to Lua.
///
/// The [`MultiValue`] type is equivalent to `Variadic<Value>`.
///
/// # Examples
///
/// ```
/// # use mlua::{Lua, Result, Variadic};
/// # fn main() -> Result<()> {
/// # let lua = Lua::new();
/// let add = lua.create_function(|_, vals: Variadic<f64>| -> Result<f64> {
///     Ok(vals.iter().sum())
/// })?;
/// lua.globals().set("add", add)?;
/// assert_eq!(lua.load("add(3, 2, 5)").eval::<f32>()?, 10.0);
/// # Ok(())
/// # }
/// ```
///
/// [`FromLua`]: crate::FromLua
/// [`MultiValue`]: crate::MultiValue
#[derive(Debug, Clone)]
pub struct Variadic<T>(Vec<T>);

impl<T> Variadic<T> {
    /// Creates an empty `Variadic` wrapper containing no values.
    pub const fn new() -> Variadic<T> {
        Variadic(Vec::new())
    }
}

impl<T> Default for Variadic<T> {
    fn default() -> Variadic<T> {
        Variadic::new()
    }
}

impl<T> FromIterator<T> for Variadic<T> {
    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
        Variadic(Vec::from_iter(iter))
    }
}

impl<T> IntoIterator for Variadic<T> {
    type Item = T;
    type IntoIter = <Vec<T> as IntoIterator>::IntoIter;

    fn into_iter(self) -> Self::IntoIter {
        self.0.into_iter()
    }
}

impl<T> Deref for Variadic<T> {
    type Target = Vec<T>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T> DerefMut for Variadic<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl<'lua, T: ToLua<'lua>> ToLuaMulti<'lua> for Variadic<T> {
    #[inline]
    fn to_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
        let mut values = MultiValue::new_or_cached(lua);
        values.refill(self.0.into_iter().map(|e| e.to_lua(lua)))?;
        Ok(values)
    }
}

impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for Variadic<T> {
    #[inline]
    fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
        let res = values
            .drain_all()
            .map(|e| T::from_lua(e, lua))
            .collect::<Result<Vec<T>>>()
            .map(Variadic);
        lua.cache_multivalue(values);
        res
    }
}

macro_rules! impl_tuple {
    () => (
        impl<'lua> ToLuaMulti<'lua> for () {
            #[inline]
            fn to_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
                Ok(MultiValue::new_or_cached(lua))
            }
        }

        impl<'lua> FromLuaMulti<'lua> for () {
            #[inline]
            fn from_lua_multi(values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
                lua.cache_multivalue(values);
                Ok(())
            }
        }
    );

    ($last:ident $($name:ident)*) => (
        impl<'lua, $($name,)* $last> ToLuaMulti<'lua> for ($($name,)* $last,)
            where $($name: ToLua<'lua>,)*
                  $last: ToLuaMulti<'lua>
        {
            #[allow(unused_mut)]
            #[allow(non_snake_case)]
            #[inline]
            fn to_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
                let ($($name,)* $last,) = self;

                let mut results = $last.to_lua_multi(lua)?;
                push_reverse!(results, $($name.to_lua(lua)?,)*);
                Ok(results)
            }
        }

        impl<'lua, $($name,)* $last> FromLuaMulti<'lua> for ($($name,)* $last,)
            where $($name: FromLua<'lua>,)*
                  $last: FromLuaMulti<'lua>
        {
            #[allow(unused_mut)]
            #[allow(non_snake_case)]
            #[inline]
            fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
                $(let $name = values.pop_front().unwrap_or(Nil);)*
                let $last = FromLuaMulti::from_lua_multi(values, lua)?;
                Ok(($(FromLua::from_lua($name, lua)?,)* $last,))
            }
        }
    );
}

macro_rules! push_reverse {
    ($multi_value:expr, $first:expr, $($rest:expr,)*) => (
        push_reverse!($multi_value, $($rest,)*);
        $multi_value.push_front($first);
    );

    ($multi_value:expr, $first:expr) => (
        $multi_value.push_front($first);
    );

    ($multi_value:expr,) => ();
}

impl_tuple!();
impl_tuple!(A);
impl_tuple!(A B);
impl_tuple!(A B C);
impl_tuple!(A B C D);
impl_tuple!(A B C D E);
impl_tuple!(A B C D E F);
impl_tuple!(A B C D E F G);
impl_tuple!(A B C D E F G H);
impl_tuple!(A B C D E F G H I);
impl_tuple!(A B C D E F G H I J);
impl_tuple!(A B C D E F G H I J K);
impl_tuple!(A B C D E F G H I J K L);
impl_tuple!(A B C D E F G H I J K L M);
impl_tuple!(A B C D E F G H I J K L M N);
impl_tuple!(A B C D E F G H I J K L M N O);
impl_tuple!(A B C D E F G H I J K L M N O P);