Pipeline System

/**
 * Represents an execution pipeline for asynchronous extensible computations
 */
open class Pipeline<TSubject : Any, TContext : Any>(vararg phases: PipelinePhase) {
    /** Common place to store pipeline attributes */
    val attributes: Attributes
    
    /** Indicates if debug mode is enabled for detailed stacktraces */
    open val developmentMode: Boolean
    
    /** Phases of this pipeline */
    val items: List<PipelinePhase>
    
    /** Returns true if there are no interceptors installed */
    val isEmpty: Boolean
    
    /** Executes pipeline in given context with given subject */
    suspend fun execute(context: TContext, subject: TSubject): TSubject
    
    /** Adds phase to the end of pipeline */
    fun addPhase(phase: PipelinePhase)
    
    /** Inserts phase relative to another phase */
    fun insertPhaseAfter(reference: PipelinePhase, phase: PipelinePhase)
    fun insertPhaseBefore(reference: PipelinePhase, phase: PipelinePhase)
    
    /** Installs interceptor for specific phase */
    fun intercept(phase: PipelinePhase, block: PipelineInterceptor<TSubject, TContext>)
    
    /** Checks if phase exists in pipeline */
    fun hasPhase(phase: PipelinePhase): Boolean
    
    /** Merges another pipeline into this one */
    fun merge(from: Pipeline<TSubject, TContext>)
}

import io.ktor.util.pipeline.*

// Define custom phases
val Setup = PipelinePhase("Setup")
val Processing = PipelinePhase("Processing")
val Cleanup = PipelinePhase("Cleanup")

// Create pipeline
val pipeline = Pipeline<String, Unit>(Setup, Processing, Cleanup)

// Install interceptors
pipeline.intercept(Setup) { data ->
    println("Setting up processing for: $data")
    // Modify subject or context as needed
}

pipeline.intercept(Processing) { data ->
    println("Processing: $data")
    val processed = data.uppercase()
    proceed(processed) // Continue with modified subject
}

pipeline.intercept(Cleanup) { data ->
    println("Cleaning up after: $data")
}

// Execute pipeline
val result = pipeline.execute(Unit, "hello world")
println("Final result: $result")

/**
 * Represents a phase in pipeline execution
 */
class PipelinePhase(val name: String) {
    override fun toString(): String = name
}

/**
 * Interface for defining relationships between pipeline phases
 */
interface PipelinePhaseRelation {
    /** Phase that this relation is relative to */
    val reference: PipelinePhase
    
    /** Insert phase after reference */
    object After : PipelinePhaseRelation
    
    /** Insert phase before reference */
    object Before : PipelinePhaseRelation
    
    /** Insert phase at the end */
    object Last : PipelinePhaseRelation
}

import io.ktor.util.pipeline.*

// Create phases
val Authentication = PipelinePhase("Authentication")
val Authorization = PipelinePhase("Authorization")
val Processing = PipelinePhase("Processing")

// Create pipeline with phase ordering
val pipeline = Pipeline<Request, Context>()

// Add phases in specific order
pipeline.addPhase(Authentication)
pipeline.insertPhaseAfter(Authentication, Authorization)
pipeline.insertPhaseAfter(Authorization, Processing)

// Or define relationships when adding
pipeline.insertPhaseBefore(Processing, PipelinePhase("Validation"))

/**
 * Context for pipeline execution providing access to subject and control flow
 */
class PipelineContext<TSubject : Any, TContext : Any>(
    private val context: TContext,
    private var subject: TSubject
) {
    /** The current subject being processed */
    val subject: TSubject get() = this.subject
    
    /** The execution context */
    val context: TContext get() = this.context
    
    /** Proceed to next interceptor with current subject */
    suspend fun proceed(): TSubject
    
    /** Proceed to next interceptor with modified subject */
    suspend fun proceed(subject: TSubject): TSubject
    
    /** Finish pipeline execution with current subject */
    suspend fun finish(): TSubject
    
    /** Finish pipeline execution with modified subject */
    suspend fun finish(subject: TSubject): TSubject
}

import io.ktor.util.pipeline.*

data class Request(val path: String, val method: String)
data class Context(val userId: String?)

val pipeline = Pipeline<Request, Context>()

pipeline.intercept(Authentication) { request ->
    if (context.userId == null) {
        // Modify request or throw exception
        throw SecurityException("Authentication required")
    }
    proceed() // Continue with current request
}

pipeline.intercept(Processing) { request ->
    val modifiedRequest = request.copy(path = request.path.lowercase())
    proceed(modifiedRequest) // Continue with modified request
}

pipeline.intercept(Cleanup) { request ->
    println("Processing complete for: ${request.path}")
    finish() // End pipeline execution
}

/**
 * Type alias for pipeline interceptor functions
 */
typealias PipelineInterceptor<TSubject, TContext> = 
    suspend PipelineContext<TSubject, TContext>.(TSubject) -> Unit

/**
 * Creates a pipeline context for execution
 */
fun <TSubject : Any, TContext : Any> Pipeline<TSubject, TContext>.createContext(
    context: TContext,
    subject: TSubject,
    coroutineContext: CoroutineContext
): PipelineContext<TSubject, TContext>

import io.ktor.util.pipeline.*

// Define reusable interceptors
val loggingInterceptor: PipelineInterceptor<String, Unit> = { subject ->
    println("Processing: $subject")
    proceed()
}

val transformInterceptor: PipelineInterceptor<String, Unit> = { subject ->
    val transformed = subject.trim().lowercase()
    proceed(transformed)
}

// Install interceptors
pipeline.intercept(Processing, loggingInterceptor)
pipeline.intercept(Processing, transformInterceptor)

// Create custom interceptor with complex logic
pipeline.intercept(Validation) { subject ->
    if (subject.isBlank()) {
        throw IllegalArgumentException("Subject cannot be blank")
    }
    
    val validated = subject.take(100) // Limit length
    proceed(validated)
}

/**
 * Suspend function gun for optimized pipeline execution
 */
class SuspendFunctionGun<TSubject : Any, TContext : Any> {
    /** Execute pipeline with optimized suspend function handling */
    suspend fun execute(
        initial: TSubject,
        context: PipelineContext<TSubject, TContext>
    ): TSubject
}

/**
 * Phase content container for interceptors and metadata
 */
class PhaseContent<TSubject : Any, TContext : Any>(
    val phase: PipelinePhase,
    val relation: PipelinePhaseRelation
) {
    /** Add interceptor to this phase */
    fun addInterceptor(interceptor: PipelineInterceptor<TSubject, TContext>)
    
    /** Remove interceptor from this phase */
    fun removeInterceptor(interceptor: PipelineInterceptor<TSubject, TContext>)
    
    /** Get all interceptors for this phase */
    val interceptors: List<PipelineInterceptor<TSubject, TContext>>
}

import io.ktor.util.pipeline.*

// Advanced pipeline with custom phase content
class CustomPipeline<TSubject : Any, TContext : Any> : Pipeline<TSubject, TContext>() {
    override val developmentMode: Boolean = true // Enable debug mode
    
    init {
        // Configure custom phase relationships
        val setupPhase = PipelinePhase("Setup")
        val mainPhase = PipelinePhase("Main") 
        val finishPhase = PipelinePhase("Finish")
        
        addPhase(setupPhase)
        insertPhaseAfter(setupPhase, mainPhase)
        insertPhaseAfter(mainPhase, finishPhase)
    }
}

// Use custom pipeline
val customPipeline = CustomPipeline<String, Map<String, Any>>()

customPipeline.intercept(PipelinePhase("Setup")) { subject ->
    // Access pipeline attributes
    attributes.put(AttributeKey("startTime"), System.currentTimeMillis())
    proceed()
}

/**
 * Stack trace recovery utilities for pipeline debugging
 */
object StackTraceRecover {
    /** Recover stack trace information from pipeline execution */
    fun recoverStackTrace(exception: Throwable, continuation: Continuation<*>)
}

/**
 * Debug pipeline context with enhanced error reporting
 */
class DebugPipelineContext<TSubject : Any, TContext : Any> : PipelineContext<TSubject, TContext> {
    /** Stack trace information for debugging */
    val stackTraceRecover: StackTraceRecover?
}

import io.ktor.util.pipeline.*

// Enable debug mode for better error reporting
class DebuggablePipeline<TSubject : Any, TContext : Any> : Pipeline<TSubject, TContext>() {
    override val developmentMode: Boolean = true
}

val debugPipeline = DebuggablePipeline<String, Unit>()

debugPipeline.intercept(Processing) { subject ->
    try {
        // Potentially failing operation
        val result = processData(subject)
        proceed(result)
    } catch (e: Exception) {
        // Enhanced error information available in development mode
        logger.error("Pipeline processing failed", e)
        throw e
    }
}