    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
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370

    use std::iter::IntoIterator;
    use std::str::FromStr;

    use crate::error::Result;
    use crate::map::Map;
    use crate::source::AsyncSource;
    use crate::{config::Config, path::Expression, source::Source, value::Value};

    /// A configuration builder
    ///
    /// It registers ordered sources of configuration to later build consistent [`Config`] from them.
    /// Configuration sources it defines are defaults, [`Source`]s and overrides.
    ///
    /// Defaults are always loaded first and can be overwritten by any of two other sources.
    /// Overrides are always loaded last, thus cannot be overridden.
    /// Both can be only set explicitly key by key in code
    /// using [`set_default`](Self::set_default) or [`set_override`](Self::set_override).
    ///
    /// An intermediate category, [`Source`], set groups of keys at once implicitly using data coming from external sources
    /// like files, environment variables or others that one implements. Defining a [`Source`] is as simple as implementing
    /// a trait for a struct.
    ///
    /// Adding sources, setting defaults and overrides does not invoke any I/O nor builds a config.
    /// It happens on demand when [`build`](Self::build) (or its alternative) is called.
    /// Therefore all errors, related to any of the [`Source`] will only show up then.
    ///
    /// # Sync and async builder
    ///
    /// [`ConfigBuilder`] uses type parameter to keep track of builder state.
    ///
    /// In [`DefaultState`] builder only supports [`Source`]s
    ///
    /// In [`AsyncState`] it supports both [`Source`]s and [`AsyncSource`]s at the price of building using `async fn`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use config::*;
    /// # use std::error::Error;
    /// # fn main() -> Result<(), Box<dyn Error>> {
    /// let mut builder = Config::builder()
    ///     .set_default("default", "1")?
    ///     .add_source(File::new("config/settings", FileFormat::Json))
    /// //  .add_async_source(...)
    ///     .set_override("override", "1")?;
    ///
    /// match builder.build() {
    ///     Ok(config) => {
    ///         // use your config
    ///     },
    ///     Err(e) => {
    ///         // something went wrong
    ///     }
    /// }
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// If any [`AsyncSource`] is used, the builder will transition to [`AsyncState`].
    /// In such case, it is required to _await_ calls to [`build`](Self::build) and its non-consuming sibling.
    ///
    /// Calls can be not chained as well
    /// ```rust
    /// # use std::error::Error;
    /// # use config::*;
    /// # fn main() -> Result<(), Box<dyn Error>> {
    /// let mut builder = Config::builder();
    /// builder = builder.set_default("default", "1")?;
    /// builder = builder.add_source(File::new("config/settings", FileFormat::Json));
    /// builder = builder.add_source(File::new("config/settings.prod", FileFormat::Json));
    /// builder = builder.set_override("override", "1")?;
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// Calling [`Config::builder`](Config::builder) yields builder in the default state.
    /// If having an asynchronous state as the initial state is desired, _turbofish_ notation needs to be used.
    /// ```rust
    /// # use config::{*, builder::AsyncState};
    /// let mut builder = ConfigBuilder::<AsyncState>::default();
    /// ```
    ///
    /// If for some reason acquiring builder in default state is required without calling [`Config::builder`](Config::builder)
    /// it can also be achieved.
    /// ```rust
    /// # use config::{*, builder::DefaultState};
    /// let mut builder = ConfigBuilder::<DefaultState>::default();
    /// ```
    #[derive(Debug, Clone, Default)]
    pub struct ConfigBuilder<St: BuilderState> {
        defaults: Map<Expression, Value>,
        overrides: Map<Expression, Value>,
        state: St,
    }

    /// Represents [`ConfigBuilder`] state.
    pub trait BuilderState {}

    /// Represents data specific to builder in default, sychronous state, without support for async.
    #[derive(Debug, Default, Clone)]
    pub struct DefaultState {
        sources: Vec<Box<dyn Source + Send + Sync>>,
    }

    /// The asynchronous configuration builder.
    ///
    /// Similar to a [`ConfigBuilder`] it maintains a set of defaults, a set of sources, and overrides.
    ///
    /// Defaults do not override anything, sources override defaults, and overrides override anything else.
    /// Within those three groups order of adding them at call site matters - entities added later take precedence.
    ///
    /// For more detailed description and examples see [`ConfigBuilder`].
    /// [`AsyncConfigBuilder`] is just an extension of it that takes async functions into account.
    ///
    /// To obtain a [`Config`] call [`build`](AsyncConfigBuilder::build) or [`build_cloned`](AsyncConfigBuilder::build_cloned)
    ///
    /// # Example
    /// Since this library does not implement any [`AsyncSource`] an example in rustdocs cannot be given.
    /// Detailed explanation about why such a source is not implemented is in [`AsyncSource`]'s documentation.
    ///
    /// Refer to [`ConfigBuilder`] for similar API sample usage or to the examples folder of the crate, where such a source is implemented.
    #[derive(Debug, Clone, Default)]
    pub struct AsyncConfigBuilder {}

    /// Represents data specific to builder in asychronous state, with support for async.
    #[derive(Debug, Default, Clone)]
    pub struct AsyncState {
        sources: Vec<SourceType>,
    }

    #[derive(Debug, Clone)]
    enum SourceType {
        Sync(Box<dyn Source + Send + Sync>),
        Async(Box<dyn AsyncSource + Send + Sync>),
    }

    impl BuilderState for DefaultState {}
    impl BuilderState for AsyncState {}

    impl<St: BuilderState> ConfigBuilder<St> {
        // operations allowed in any state

        /// Set a default `value` at `key`
        ///
        /// This value can be overwritten by any [`Source`], [`AsyncSource`] or override.
        ///
        /// # Errors
        ///
        /// Fails if `Expression::from_str(key)` fails.
        pub fn set_default<S, T>(mut self, key: S, value: T) -> Result<Self>
        where
            S: AsRef<str>,
            T: Into<Value>,
        {
            self.defaults
                .insert(Expression::from_str(key.as_ref())?, value.into());
            Ok(self)
        }

        /// Set an override
        ///
        /// This function sets an overwrite value. It will not be altered by any default, [`Source`] nor [`AsyncSource`]
        ///
        /// # Errors
        ///
        /// Fails if `Expression::from_str(key)` fails.
        pub fn set_override<S, T>(mut self, key: S, value: T) -> Result<Self>
        where
            S: AsRef<str>,
            T: Into<Value>,
        {
            self.overrides
                .insert(Expression::from_str(key.as_ref())?, value.into());
            Ok(self)
        }

        /// Sets an override if value is Some(_)
        ///
        /// This function sets an overwrite value if Some(_) is passed. If None is passed, this function does nothing.
        /// It will not be altered by any default, [`Source`] nor [`AsyncSource`]
        ///
        /// # Errors
        ///
        /// Fails if `Expression::from_str(key)` fails.
        pub fn set_override_option<S, T>(mut self, key: S, value: Option<T>) -> Result<Self>
        where
            S: AsRef<str>,
            T: Into<Value>,
        {
            if let Some(value) = value {
                self.overrides
                    .insert(Expression::from_str(key.as_ref())?, value.into());
            }
            Ok(self)
        }
    }

    impl ConfigBuilder<DefaultState> {
        // operations allowed in sync state

        /// Registers new [`Source`] in this builder.
        ///
        /// Calling this method does not invoke any I/O. [`Source`] is only saved in internal register for later use.
        #[must_use]
        pub fn add_source<T>(mut self, source: T) -> Self
        where
            T: Source + Send + Sync + 'static,
        {
            self.state.sources.push(Box::new(source));
            self
        }

        /// Registers new [`AsyncSource`] in this builder and forces transition to [`AsyncState`].
        ///
        /// Calling this method does not invoke any I/O. [`AsyncSource`] is only saved in internal register for later use.
        pub fn add_async_source<T>(self, source: T) -> ConfigBuilder<AsyncState>
        where
            T: AsyncSource + Send + Sync + 'static,
        {
            let async_state = ConfigBuilder {
                state: AsyncState {
                    sources: self
                        .state
                        .sources
                        .into_iter()
                        .map(|s| SourceType::Sync(s))
                        .collect(),
                },
                defaults: self.defaults,
                overrides: self.overrides,
            };

            async_state.add_async_source(source)
        }

        /// Reads all registered [`Source`]s.
        ///
        /// This is the method that invokes all I/O operations.
        /// For a non consuming alternative see [`build_cloned`](Self::build_cloned)
        ///
        /// # Errors
        /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
        /// this method returns error.
        pub fn build(self) -> Result<Config> {
            Self::build_internal(self.defaults, self.overrides, &self.state.sources)
        }

        /// Reads all registered [`Source`]s.
        ///
        /// Similar to [`build`](Self::build), but it does not take ownership of `ConfigBuilder` to allow later reuse.
        /// Internally it clones data to achieve it.
        ///
        /// # Errors
        /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
        /// this method returns error.
        pub fn build_cloned(&self) -> Result<Config> {
            Self::build_internal(
                self.defaults.clone(),
                self.overrides.clone(),
                &self.state.sources,
            )
        }

        fn build_internal(
            defaults: Map<Expression, Value>,
            overrides: Map<Expression, Value>,
            sources: &[Box<dyn Source + Send + Sync>],
        ) -> Result<Config> {
            let mut cache: Value = Map::<String, Value>::new().into();

            // Add defaults
            for (key, val) in defaults {
                key.set(&mut cache, val);
            }

            // Add sources
            sources.collect_to(&mut cache)?;

            // Add overrides
            for (key, val) in overrides {
                key.set(&mut cache, val);
            }

            Ok(Config::new(cache))
        }
    }

    impl ConfigBuilder<AsyncState> {
        // operations allowed in async state

        /// Registers new [`Source`] in this builder.
        ///
        /// Calling this method does not invoke any I/O. [`Source`] is only saved in internal register for later use.
        #[must_use]
        pub fn add_source<T>(mut self, source: T) -> Self
        where
            T: Source + Send + Sync + 'static,
        {
            self.state.sources.push(SourceType::Sync(Box::new(source)));
            self
        }

        /// Registers new [`AsyncSource`] in this builder.
        ///
        /// Calling this method does not invoke any I/O. [`AsyncSource`] is only saved in internal register for later use.
        #[must_use]
        pub fn add_async_source<T>(mut self, source: T) -> Self
        where
            T: AsyncSource + Send + Sync + 'static,
        {
            self.state.sources.push(SourceType::Async(Box::new(source)));
            self
        }

        /// Reads all registered defaults, [`Source`]s, [`AsyncSource`]s and overrides.
        ///
        /// This is the method that invokes all I/O operations.
        /// For a non consuming alternative see [`build_cloned`](Self::build_cloned)
        ///
        /// # Errors
        /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
        /// this method returns error.
        pub async fn build(self) -> Result<Config> {
            Self::build_internal(self.defaults, self.overrides, &self.state.sources).await
        }

        /// Reads all registered defaults, [`Source`]s, [`AsyncSource`]s and overrides.
        ///
        /// Similar to [`build`](Self::build), but it does not take ownership of `ConfigBuilder` to allow later reuse.
        /// Internally it clones data to achieve it.
        ///
        /// # Errors
        /// If source collection fails, be it technical reasons or related to inability to read data as `Config` for different reasons,
        /// this method returns error.
        pub async fn build_cloned(&self) -> Result<Config> {
            Self::build_internal(
                self.defaults.clone(),
                self.overrides.clone(),
                &self.state.sources,
            )
            .await
        }

        async fn build_internal(
            defaults: Map<Expression, Value>,
            overrides: Map<Expression, Value>,
            sources: &[SourceType],
        ) -> Result<Config> {
            let mut cache: Value = Map::<String, Value>::new().into();

            // Add defaults
            for (key, val) in defaults {
                key.set(&mut cache, val);
            }

            for source in sources.iter() {
                match source {
                    SourceType::Sync(source) => source.collect_to(&mut cache)?,
                    SourceType::Async(source) => source.collect_to(&mut cache).await?,
                }
            }

            // Add overrides
            for (key, val) in overrides {
                key.set(&mut cache, val);
            }

            Ok(Config::new(cache))
        }
    }