// ============================================================================
// Import
// ============================================================================

import { ConfigInterface } from "../../interface/ConfigInterface";
import { AbstractProcess } from "../abstract/AbstractProcess";
import { Stage } from "./Stage";

// ============================================================================
// Class
// ============================================================================

/**
 * Represents the pipeline of stages to be executed.
 * This class manages the execution flow of stages, including parallel
 * execution, dependency handling, and applying global options for consistent
 * pipeline behavior.
 */
export class Pipeline extends AbstractProcess {
    // Parameters
    // ========================================================================

    /**
     * List of stages to be executed in the pipeline.
     */
    private stages: Stage[];

    /**
     * Global options that apply across the entire pipeline.
     */
    private options?: ConfigInterface["options"];

    // Constructor
    // ========================================================================

    /**
     * Constructs a new Pipeline instance with the given configuration.
     * Initializes stages and applies global options for execution control.
     *
     * @param config - The configuration object defining the stages, steps,
     * and global options for the pipeline.
     */
    constructor(private config: ConfigInterface) {
        super();
        this.stages = config.stages.map((stage) => new Stage(stage));
        this.options = config.options;
        this.logInfo("Pipeline instance created.");
    }

    // Methods
    // ========================================================================

    /**
     * Runs the pipeline, executing stages based on their dependencies.
     * Stages are run in parallel by default, but their execution respects
     * defined dependencies. Applies global options for logging, error
     * handling, and execution control.
     */
    async run(): Promise<void> {
        this.logInfo("Starting pipeline execution...");

        // Track stages that have been completed
        const completedStages = new Set<string>();

        // Run stages with dependency management and parallel execution control
        try {
            this.logDebug("Pipeline execution started with debug logging.");

            // Execute all stages with concurrency control
            const stagePromises = this.stages.map((stage) =>
                stage.execute(completedStages),
            );
            await this.runWithConcurrencyControl(stagePromises);

            this.logInfo("Pipeline execution completed successfully.");
        } catch (error) {
            this.logError("Pipeline execution failed:", error);

            // Halt pipeline if configured to do so on failure
            if (this.options?.haltOnFailure !== false) {
                this.logError("Halting pipeline due to failure.");
                process.exit(1);
            } else {
                this.logWarn("Continuing pipeline execution despite errors.");
            }
        }
    }

    /**
     * Runs the stage promises with concurrency control based on global
     * options. Limits the number of parallel running stages if
     * maxConcurrentStages is set in global options.
     * @param stagePromises - An array of promises representing stage
     * executions.
     */
    private async runWithConcurrencyControl(
        stagePromises: Promise<void>[],
    ): Promise<void> {
        const maxConcurrentStages =
            this.options?.maxConcurrentStages || stagePromises.length;

        // Process stages with a concurrency limit
        const executingStages = new Set<Promise<void>>();

        for (const stagePromise of stagePromises) {
            executingStages.add(stagePromise);

            // Ensure stages are removed from the set once complete
            stagePromise.finally(() => executingStages.delete(stagePromise));

            // Enforce concurrency limit
            if (executingStages.size >= (maxConcurrentStages as number)) {
                // Wait until at least one stage completes
                await Promise.race(executingStages);
            }
        }

        // Wait for all remaining stages to complete
        await Promise.all(executingStages);
    }
}