export const CANVAS_IMAGE_TASK_QUEUE_CONFIG_KEY = "canvas_image_task_queue_config";

export const DEFAULT_CANVAS_IMAGE_TASK_CONCURRENCY = 1;
export const MAX_CANVAS_IMAGE_TASK_CONCURRENCY = 100;

export interface CanvasImageTaskQueueConfig {
  concurrency: number;
}

function clampConcurrency(value: number) {
  return Math.min(
    MAX_CANVAS_IMAGE_TASK_CONCURRENCY,
    Math.max(DEFAULT_CANVAS_IMAGE_TASK_CONCURRENCY, Math.floor(value))
  );
}

function parseConcurrencyCandidate(value: unknown): number | null {
  if (typeof value === "number" && Number.isFinite(value)) {
    return clampConcurrency(value);
  }

  if (typeof value === "string" && value.trim()) {
    const parsed = Number.parseInt(value.trim(), 10);
    if (Number.isFinite(parsed)) {
      return clampConcurrency(parsed);
    }
  }

  return null;
}

export function normalizeCanvasImageTaskQueueConfig(
  value: unknown,
  options?: { envConcurrency?: unknown }
): CanvasImageTaskQueueConfig {
  const raw = value && typeof value === "object" && !Array.isArray(value)
    ? (value as Record<string, unknown>)
    : {};
  const candidates = [
    raw.concurrency,
    raw.maxConcurrency,
    raw.maxConcurrent,
    typeof value === "number" || typeof value === "string" ? value : undefined,
    options?.envConcurrency,
  ];

  for (const candidate of candidates) {
    const parsed = parseConcurrencyCandidate(candidate);
    if (parsed !== null) {
      return { concurrency: parsed };
    }
  }

  return { concurrency: DEFAULT_CANVAS_IMAGE_TASK_CONCURRENCY };
}