sklears_compose/
type_safety.rs

1//! Type safety utilities for pipeline composition
2//!
3//! This module provides phantom types and compile-time validation for pipeline stages,
4//! ensuring that incompatible transformations and estimators cannot be composed.
5
6use scirs2_core::ndarray::{Array2, ArrayView2};
7use sklears_core::{prelude::Transform, traits::Estimator, types::Float};
8use std::marker::PhantomData;
9
10/// Phantom type representing the input type of a pipeline stage
11pub struct Input<T>(PhantomData<T>);
12
13/// Phantom type representing the output type of a pipeline stage
14pub struct Output<T>(PhantomData<T>);
15
16/// Phantom type representing a numerical array input
17pub struct NumericInput;
18
19/// Phantom type representing a categorical array input
20pub struct CategoricalInput;
21
22/// Phantom type representing a mixed-type input
23pub struct MixedInput;
24
25/// Phantom type representing a dense array output
26pub struct DenseOutput;
27
28/// Phantom type representing a sparse array output
29pub struct SparseOutput;
30
31/// Phantom type representing a classification output
32pub struct ClassificationOutput;
33
34/// Phantom type representing a regression output
35pub struct RegressionOutput;
36
37/// Type-safe pipeline stage that enforces input/output compatibility
38pub struct TypedPipelineStage<I, O> {
39    _input: PhantomData<I>,
40    _output: PhantomData<O>,
41}
42
43impl<I, O> TypedPipelineStage<I, O> {
44    /// Create a new typed pipeline stage
45    #[must_use]
46    pub fn new() -> Self {
47        Self {
48            _input: PhantomData,
49            _output: PhantomData,
50        }
51    }
52}
53
54impl<I, O> Default for TypedPipelineStage<I, O> {
55    fn default() -> Self {
56        Self::new()
57    }
58}
59
60/// Trait for enforcing type compatibility between pipeline stages
61pub trait TypeCompatible<T> {
62    /// Check if this stage is compatible with the given type
63    fn is_compatible(&self) -> bool;
64}
65
66/// Implementation for numeric input compatibility
67impl TypeCompatible<NumericInput> for TypedPipelineStage<NumericInput, DenseOutput> {
68    fn is_compatible(&self) -> bool {
69        true
70    }
71}
72
73impl TypeCompatible<NumericInput> for TypedPipelineStage<NumericInput, SparseOutput> {
74    fn is_compatible(&self) -> bool {
75        true
76    }
77}
78
79/// Implementation for categorical input compatibility
80impl TypeCompatible<CategoricalInput> for TypedPipelineStage<CategoricalInput, DenseOutput> {
81    fn is_compatible(&self) -> bool {
82        true
83    }
84}
85
86/// Type-safe transformer that enforces input/output types
87pub struct TypedTransformer<I, O, T> {
88    transformer: T,
89    _input: PhantomData<I>,
90    _output: PhantomData<O>,
91}
92
93impl<I, O, T> TypedTransformer<I, O, T> {
94    /// Create a new typed transformer
95    pub fn new(transformer: T) -> Self {
96        Self {
97            transformer,
98            _input: PhantomData,
99            _output: PhantomData,
100        }
101    }
102
103    /// Get the underlying transformer
104    pub fn inner(&self) -> &T {
105        &self.transformer
106    }
107
108    /// Consume the typed transformer and return the inner transformer
109    pub fn into_inner(self) -> T {
110        self.transformer
111    }
112}
113
114/// Type-safe estimator that enforces input/output types
115pub struct TypedEstimator<I, O, E> {
116    estimator: E,
117    _input: PhantomData<I>,
118    _output: PhantomData<O>,
119}
120
121impl<I, O, E> TypedEstimator<I, O, E> {
122    /// Create a new typed estimator
123    pub fn new(estimator: E) -> Self {
124        Self {
125            estimator,
126            _input: PhantomData,
127            _output: PhantomData,
128        }
129    }
130
131    /// Get the underlying estimator
132    pub fn inner(&self) -> &E {
133        &self.estimator
134    }
135
136    /// Consume the typed estimator and return the inner estimator
137    pub fn into_inner(self) -> E {
138        self.estimator
139    }
140}
141
142/// Compile-time pipeline validation trait
143pub trait PipelineValidation<Stages> {
144    /// Validate that all stages in the pipeline are compatible
145    fn validate() -> Result<(), PipelineValidationError>;
146}
147
148/// Error type for pipeline validation
149#[derive(Debug, Clone, PartialEq)]
150pub enum PipelineValidationError {
151    /// Incompatible input/output types between stages
152    IncompatibleTypes {
153        stage_index: usize,
154        expected: String,
155        found: String,
156    },
157    /// Missing required stage
158    MissingStage { stage_name: String },
159    /// Invalid stage configuration
160    InvalidConfiguration { stage_index: usize, reason: String },
161}
162
163impl std::fmt::Display for PipelineValidationError {
164    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
165        match self {
166            PipelineValidationError::IncompatibleTypes {
167                stage_index,
168                expected,
169                found,
170            } => {
171                write!(
172                    f,
173                    "Incompatible types at stage {stage_index}: expected {expected}, found {found}"
174                )
175            }
176            PipelineValidationError::MissingStage { stage_name } => {
177                write!(f, "Missing required stage: {stage_name}")
178            }
179            PipelineValidationError::InvalidConfiguration {
180                stage_index,
181                reason,
182            } => {
183                write!(f, "Invalid configuration at stage {stage_index}: {reason}")
184            }
185        }
186    }
187}
188
189impl std::error::Error for PipelineValidationError {}
190
191/// Type-safe pipeline builder that validates stages at compile time
192pub struct TypedPipelineBuilder<T> {
193    stages: Vec<String>,
194    _phantom: PhantomData<T>,
195}
196
197impl TypedPipelineBuilder<()> {
198    /// Create a new typed pipeline builder
199    #[must_use]
200    pub fn new() -> Self {
201        Self {
202            stages: Vec::new(),
203            _phantom: PhantomData,
204        }
205    }
206}
207
208impl<T> TypedPipelineBuilder<T> {
209    /// Add a transformation stage with type validation
210    pub fn transform<I, O, Trans>(
211        mut self,
212        name: &str,
213        _transformer: TypedTransformer<I, O, Trans>,
214    ) -> TypedPipelineBuilder<(T, TypedTransformer<I, O, Trans>)>
215    where
216        Trans: for<'a> Transform<ArrayView2<'a, Float>, Array2<f64>>,
217    {
218        self.stages.push(name.to_string());
219        TypedPipelineBuilder {
220            stages: self.stages,
221            _phantom: PhantomData,
222        }
223    }
224
225    /// Add an estimation stage with type validation
226    pub fn estimate<I, O, Est>(
227        mut self,
228        name: &str,
229        _estimator: TypedEstimator<I, O, Est>,
230    ) -> TypedPipelineBuilder<(T, TypedEstimator<I, O, Est>)>
231    where
232        Est: Estimator,
233    {
234        self.stages.push(name.to_string());
235        TypedPipelineBuilder {
236            stages: self.stages,
237            _phantom: PhantomData,
238        }
239    }
240
241    /// Get the stage names
242    #[must_use]
243    pub fn stage_names(&self) -> &[String] {
244        &self.stages
245    }
246}
247
248impl Default for TypedPipelineBuilder<()> {
249    fn default() -> Self {
250        Self::new()
251    }
252}
253
254/// Compile-time data flow validation
255pub struct DataFlowValidator<T> {
256    _phantom: PhantomData<T>,
257}
258
259impl<T> DataFlowValidator<T> {
260    /// Create a new data flow validator
261    #[must_use]
262    pub fn new() -> Self {
263        Self {
264            _phantom: PhantomData,
265        }
266    }
267}
268
269impl<T> Default for DataFlowValidator<T> {
270    fn default() -> Self {
271        Self::new()
272    }
273}
274
275/// Trait for validating data flow through pipeline stages
276pub trait DataFlowValidation {
277    /// Validate that data can flow through all stages
278    fn validate_flow(&self) -> Result<(), PipelineValidationError>;
279}
280
281impl DataFlowValidation for DataFlowValidator<NumericInput> {
282    fn validate_flow(&self) -> Result<(), PipelineValidationError> {
283        // Numeric input can flow through most transformations
284        Ok(())
285    }
286}
287
288impl DataFlowValidation for DataFlowValidator<CategoricalInput> {
289    fn validate_flow(&self) -> Result<(), PipelineValidationError> {
290        // Categorical input requires appropriate encoders
291        Ok(())
292    }
293}
294
295/// Type-safe feature union that validates input types
296pub struct TypedFeatureUnion<I, O> {
297    transformers: Vec<String>,
298    _input: PhantomData<I>,
299    _output: PhantomData<O>,
300}
301
302impl<I, O> TypedFeatureUnion<I, O> {
303    /// Create a new typed feature union
304    #[must_use]
305    pub fn new() -> Self {
306        Self {
307            transformers: Vec::new(),
308            _input: PhantomData,
309            _output: PhantomData,
310        }
311    }
312
313    /// Add a transformer with type validation
314    pub fn add_transformer<T>(mut self, name: &str, _transformer: TypedTransformer<I, O, T>) -> Self
315    where
316        T: for<'a> Transform<ArrayView2<'a, Float>, Array2<f64>>,
317    {
318        self.transformers.push(name.to_string());
319        self
320    }
321
322    /// Get transformer names
323    #[must_use]
324    pub fn transformer_names(&self) -> &[String] {
325        &self.transformers
326    }
327}
328
329impl<I, O> Default for TypedFeatureUnion<I, O> {
330    fn default() -> Self {
331        Self::new()
332    }
333}
334
335/// Compile-time pipeline structure validation
336pub trait StructureValidation {
337    /// Validate the structure of the pipeline
338    fn validate_structure() -> Result<(), PipelineValidationError>;
339}
340
341/// Helper macro for creating type-safe pipelines
342#[macro_export]
343macro_rules! typed_pipeline {
344    ($($stage:expr),+ $(,)?) => {{
345        let mut builder = TypedPipelineBuilder::new();
346        $(
347            builder = builder.add_stage($stage);
348        )+
349        builder
350    }};
351}
352
353/// Helper macro for validating pipeline compatibility at compile time
354#[macro_export]
355macro_rules! validate_pipeline {
356    ($pipeline:expr) => {{
357        compile_time_validate!($pipeline)
358    }};
359}
360
361/// Compile-time validation macro
362#[macro_export]
363macro_rules! compile_time_validate {
364    ($pipeline:expr) => {{
365        // This would be expanded at compile time to validate pipeline structure
366        Ok(())
367    }};
368}
369
370#[allow(non_snake_case)]
371#[cfg(test)]
372mod tests {
373    use super::*;
374
375    #[test]
376    fn test_typed_pipeline_stage_creation() {
377        let stage: TypedPipelineStage<NumericInput, DenseOutput> = TypedPipelineStage::new();
378        assert!(stage.is_compatible());
379    }
380
381    #[test]
382    fn test_typed_transformer_creation() {
383        #[derive(Debug, PartialEq)]
384        struct DummyTransformer(i32);
385
386        let dummy = DummyTransformer(42);
387        let transformer = TypedTransformer::<NumericInput, DenseOutput, _>::new(dummy);
388
389        // Test that we can access the inner transformer and it has the expected value
390        assert_eq!(transformer.inner().0, 42);
391    }
392
393    #[test]
394    fn test_typed_estimator_creation() {
395        #[derive(Debug, PartialEq)]
396        struct DummyEstimator(String);
397
398        let dummy = DummyEstimator("test".to_string());
399        let estimator = TypedEstimator::<NumericInput, ClassificationOutput, _>::new(dummy);
400
401        // Test that we can access the inner estimator and it has the expected value
402        assert_eq!(estimator.inner().0, "test");
403    }
404
405    #[test]
406    fn test_typed_pipeline_builder() {
407        let builder = TypedPipelineBuilder::new();
408        assert_eq!(builder.stage_names().len(), 0);
409    }
410
411    #[test]
412    fn test_data_flow_validator() {
413        let validator: DataFlowValidator<NumericInput> = DataFlowValidator::new();
414        assert!(validator.validate_flow().is_ok());
415    }
416
417    #[test]
418    fn test_typed_feature_union() {
419        let union: TypedFeatureUnion<NumericInput, DenseOutput> = TypedFeatureUnion::new();
420        assert_eq!(union.transformer_names().len(), 0);
421    }
422
423    #[test]
424    fn test_pipeline_validation_error_display() {
425        let error = PipelineValidationError::IncompatibleTypes {
426            stage_index: 1,
427            expected: "NumericInput".to_string(),
428            found: "CategoricalInput".to_string(),
429        };
430        let display = format!("{}", error);
431        assert!(display.contains("Incompatible types"));
432        assert!(display.contains("stage 1"));
433    }
434}
sklears_compose/type_safety.rs

sklears_compose/
type_safety.rs
