package net.bmahe.genetics4j.gpu.spec;
   
   import java.util.List;
   import java.util.Objects;
   import java.util.Optional;
   import java.util.Set;
   
   import org.apache.commons.lang3.Validate;
   import org.immutables.value.Value;
  
  /**
   * Specification for OpenCL programs containing kernel source code, build options, and compilation settings.
   * 
   * <p>Program represents a complete OpenCL program specification that includes kernel source code (either as direct
   * content or resource references), kernel definitions, and compilation options. This specification is used by the GPU
   * EA system to compile and execute OpenCL kernels for fitness evaluation on GPU devices.
   * 
   * <p>A program can contain:
   * <ul>
   * <li><strong>Source content</strong>: Direct OpenCL C code as strings</li>
   * <li><strong>Resource references</strong>: Paths to OpenCL source files in the classpath</li>
   * <li><strong>Kernel definitions</strong>: Names of kernels to be compiled and made available</li>
   * <li><strong>Build options</strong>: Compiler flags and preprocessor definitions</li>
   * </ul>
   * 
   * <p>Program compilation workflow:
   * <ol>
   * <li><strong>Source loading</strong>: Load content from strings and resource files</li>
   * <li><strong>Source concatenation</strong>: Combine all sources into a single compilation unit</li>
   * <li><strong>Compilation</strong>: Compile with specified build options for target devices</li>
   * <li><strong>Kernel extraction</strong>: Create kernel objects for specified kernel names</li>
   * <li><strong>Validation</strong>: Verify all kernels were successfully created</li>
   * </ol>
   * 
   * <p>Common usage patterns:
   * 
   * <pre>{@code
   * // Simple single-kernel program from resource
   * Program basicProgram = Program.ofResource("/kernels/fitness.cl", "evaluate_fitness");
   * 
   * // Program with build options for optimization
   * Program optimizedProgram = Program
   * 		.ofResource("/kernels/optimization.cl", "fitness_kernel", "-O3 -DPOPULATION_SIZE=1000 -DUSE_FAST_MATH");
   * 
   * // Complex program with multiple sources and kernels
   * Program complexProgram = Program.builder()
   * 		.addContent("#define PROBLEM_SIZE 256") // Direct content
   * 		.addResources("/kernels/common.cl") // Common utilities
   * 		.addResources("/kernels/fitness.cl") // Main fitness logic
   * 		.addKernelNames("fitness_eval") // Primary kernel
   * 		.addKernelNames("data_preparation") // Helper kernel
   * 		.buildOptions("-cl-fast-relaxed-math -DLOCAL_SIZE=64")
   * 		.build();
   * }</pre>
   * 
   * <p>Build options support:
   * <ul>
   * <li><strong>Optimization flags</strong>: -O0, -O1, -O2, -O3 for performance tuning</li>
   * <li><strong>Math optimizations</strong>: -cl-fast-relaxed-math for numerical performance</li>
   * <li><strong>Preprocessor definitions</strong>: -DMACRO=value for compile-time configuration</li>
   * <li><strong>Warning control</strong>: -w to disable warnings, -Werror to treat warnings as errors</li>
   * <li><strong>Standards compliance</strong>: -cl-std=CL1.2 for specific OpenCL version targeting</li>
   * </ul>
   * 
   * <p>Resource loading considerations:
   * <ul>
   * <li><strong>Classpath resolution</strong>: Resources loaded relative to classpath</li>
   * <li><strong>Encoding</strong>: Source files assumed to be UTF-8 encoded</li>
   * <li><strong>Include simulation</strong>: Manual concatenation instead of OpenCL #include</li>
   * <li><strong>Error handling</strong>: Resource loading failures result in compilation errors</li>
   * </ul>
   * 
   * <p>Validation and constraints:
   * <ul>
   * <li><strong>Kernel names required</strong>: At least one kernel name must be specified</li>
   * <li><strong>Source availability</strong>: Either content or resources must provide source code</li>
   * <li><strong>Name uniqueness</strong>: Kernel names must be unique within the program</li>
   * <li><strong>Compilation validity</strong>: Source code must compile successfully for target devices</li>
   * </ul>
   * 
   * @see net.bmahe.genetics4j.gpu.GPUFitnessEvaluator
   * @see net.bmahe.genetics4j.gpu.spec.GPUEAConfiguration
   * @see net.bmahe.genetics4j.gpu.opencl.OpenCLExecutionContext
   */
  @Value.Immutable
  public abstract class Program {
  
  	/**
  	 * Returns the direct OpenCL source code content as strings.
  	 * 
  	 * <p>Content represents OpenCL C source code provided directly as strings rather than loaded from resources.
  	 * Multiple content strings are concatenated during compilation to form a single compilation unit.
  	 * 
  	 * @return list of OpenCL source code strings
  	 */
  	@Value.Parameter
  	public abstract List<String> content();
  
  	/**
 	 * Returns the classpath resource paths containing OpenCL source code.
 	 * 
 	 * <p>Resources are loaded from the classpath at compilation time and concatenated with any direct content to form
 	 * the complete program source. Resource paths should be relative to the classpath root.
 	 * 
 	 * @return set of classpath resource paths for OpenCL source files
 	 */
 	@Value.Parameter
 	public abstract Set<String> resources();
 
 	/**
 	 * Returns the names of kernels to be extracted from the compiled program.
 	 * 
 	 * <p>Kernel names specify which functions in the OpenCL source should be made available as executable kernels. These
 	 * names must correspond to functions declared with the {@code __kernel} qualifier in the source code.
 	 * 
 	 * @return set of kernel function names to extract after compilation
 	 */
 	@Value.Parameter
 	public abstract Set<String> kernelNames();
 
 	/**
 	 * Returns the OpenCL compiler build options for program compilation.
 	 * 
 	 * <p>Build options are passed to the OpenCL compiler to control optimization, define preprocessor macros, and
 	 * configure compilation behavior. Common options include optimization levels, math optimizations, and macro
 	 * definitions.
 	 * 
 	 * @return optional build options string for OpenCL compilation
 	 */
 	public abstract Optional<String> buildOptions();
 
 	@Value.Check
 	protected void check() {
 		Objects.requireNonNull(kernelNames());
 		Validate.isTrue(kernelNames().isEmpty() == false, "At least one kernel name must be specified");
 	}
 
 	/**
 	 * Creates a program from direct OpenCL source content with a single kernel.
 	 * 
 	 * <p>This factory method creates a simple program specification with source code provided directly as a string and a
 	 * single kernel to be extracted.
 	 * 
 	 * @param content    the OpenCL source code as a string
 	 * @param kernelName the name of the kernel function to extract
 	 * @return a new program specification with the given content and kernel
 	 * @throws IllegalArgumentException if content or kernelName is null or blank
 	 */
 	public static Program ofContent(final String content, final String kernelName) {
 		Validate.notBlank(content);
 		Validate.notBlank(kernelName);
 
 		return ImmutableProgram.builder().addContent(content).addKernelNames(kernelName).build();
 	}
 
 	/**
 	 * Creates a program from a classpath resource with a single kernel.
 	 * 
 	 * <p>This factory method creates a program specification that loads OpenCL source code from a classpath resource and
 	 * extracts a single named kernel.
 	 * 
 	 * @param resource   the classpath path to the OpenCL source file
 	 * @param kernelName the name of the kernel function to extract
 	 * @return a new program specification with the given resource and kernel
 	 * @throws IllegalArgumentException if resource or kernelName is null or blank
 	 */
 	public static Program ofResource(final String resource, final String kernelName) {
 		Validate.notBlank(resource);
 		Validate.notBlank(kernelName);
 
 		return ImmutableProgram.builder().addResources(resource).addKernelNames(kernelName).build();
 	}
 
 	/**
 	 * Creates a program from a classpath resource with a single kernel and build options.
 	 * 
 	 * <p>This factory method creates a program specification that loads OpenCL source code from a classpath resource,
 	 * extracts a single named kernel, and applies the specified build options during compilation.
 	 * 
 	 * @param resource     the classpath path to the OpenCL source file
 	 * @param kernelName   the name of the kernel function to extract
 	 * @param buildOptions the build options for OpenCL compilation
 	 * @return a new program specification with the given resource, kernel, and build options
 	 * @throws IllegalArgumentException if resource or kernelName is null or blank
 	 */
 	public static Program ofResource(final String resource, final String kernelName, final String buildOptions) {
 		Validate.notBlank(resource);
 		Validate.notBlank(kernelName);
 
 		return ImmutableProgram.builder()
 				.addResources(resource)
 				.addKernelNames(kernelName)
 				.buildOptions(buildOptions)
 				.build();
 	}
 
 	/**
 	 * Creates a new builder for constructing complex program specifications.
 	 * 
 	 * <p>The builder provides a fluent interface for creating programs with multiple source files, kernels, and advanced
 	 * configuration options.
 	 * 
 	 * @return a new builder instance for creating program specifications
 	 */
 	public static ImmutableProgram.Builder builder() {
 		return ImmutableProgram.builder();
 	}
 }