import type { ErrorCode } from "./error";

export const RENDER_ROUTING_SCHEMA_VERSION = 1 as const;

export type RenderRoutingBackend =
  | "WEBGL2"
  | "WEBGPU"
  | "CYCLES"
  | "EEVEE_COMPLEX"
  | "CUDA"
  | "OPTIX"
  | "HIP"
  | "METAL"
  | "ONEAPI";
export type RenderRoutingEngine = "BLENDER_EEVEE" | "BLENDER_EEVEE_NEXT" | "BLENDER_CYCLES" | "BLENDER_WORKBENCH";
export type RenderRoutingTarget = "WEB_LOCAL_BOUNDED" | "SERVER_JOB";

export interface RenderRoutingRequestIR {
  schemaVersion: typeof RENDER_ROUTING_SCHEMA_VERSION;
  renderEngine: string;
  backend: RenderRoutingBackend;
  complexity: "BOUNDED" | "COMPLEX";
  hardwareBackend?: "NONE" | "CUDA" | "OPTIX" | "HIP" | "METAL" | "ONEAPI";
}

export interface RenderRoutingContextIR {
  webgpuAvailable?: boolean;
  webgpuRendererBundled?: boolean;
  serverRenderAvailable?: boolean;
}

export interface RenderRoutingResultIR {
  schemaVersion: typeof RENDER_ROUTING_SCHEMA_VERSION;
  target: RenderRoutingTarget;
  status: "READY" | "BLOCKED";
  capability: "WEB_REALTIME_BOUNDED" | "CYCLES_SERVER_RENDER" | "COMPLEX_EEVEE_SERVER_RENDER" |
    "HARDWARE_SERVER_RENDER" | "WORKBENCH_SERVER_RENDER" | "UNSUPPORTED_RENDER_ENGINE";
  reason: "BOUNDED_EEVEE" | "WEBGPU_UNAVAILABLE" | "CYCLES_REQUIRES_SERVER" |
    "COMPLEX_EEVEE_REQUIRES_SERVER" | "HARDWARE_BACKEND_REQUIRES_SERVER" |
    "WORKBENCH_REQUIRES_SERVER" | "SERVER_ENDPOINT_UNAVAILABLE" | "UNSUPPORTED_ENGINE";
  issues: Array<{ code: ErrorCode; message: string; recoverable: boolean }>;
}

function blocked(
  target: RenderRoutingTarget,
  capability: RenderRoutingResultIR["capability"],
  reason: RenderRoutingResultIR["reason"],
  code: ErrorCode,
  message: string,
): RenderRoutingResultIR {
  return {
    schemaVersion: RENDER_ROUTING_SCHEMA_VERSION,
    target,
    status: "BLOCKED",
    capability,
    reason,
    issues: [{ code, message, recoverable: true }],
  };
}

function ready(target: RenderRoutingTarget, capability: RenderRoutingResultIR["capability"], reason: RenderRoutingResultIR["reason"]): RenderRoutingResultIR {
  return { schemaVersion: RENDER_ROUTING_SCHEMA_VERSION, target, status: "READY", capability, reason, issues: [] };
}

function validateRequest(request: RenderRoutingRequestIR): void {
  if (!request || request.schemaVersion !== RENDER_ROUTING_SCHEMA_VERSION) throw new Error("INVALID_ARGUMENT: render routing schema is unsupported");
  if (!Object.hasOwn({ WEBGL2: true, WEBGPU: true, CYCLES: true, EEVEE_COMPLEX: true, CUDA: true, OPTIX: true, HIP: true, METAL: true, ONEAPI: true }, request.backend)) {
    throw new Error("INVALID_ARGUMENT: render routing backend is unsupported");
  }
  if (typeof request.renderEngine !== "string" || !/^[A-Z0-9_]{1,64}$/.test(request.renderEngine)) throw new Error("INVALID_ARGUMENT: render routing engine identity is invalid");
  if (request.complexity !== "BOUNDED" && request.complexity !== "COMPLEX") throw new Error("INVALID_ARGUMENT: render routing complexity is unsupported");
  if (request.hardwareBackend !== undefined && !Object.hasOwn({ NONE: true, CUDA: true, OPTIX: true, HIP: true, METAL: true, ONEAPI: true }, request.hardwareBackend)) {
    throw new Error("INVALID_ARGUMENT: render routing hardware backend is unsupported");
  }
}

/** Routes final-render-only capabilities without claiming a local approximation is equivalent. */
export function routeRenderExecution(request: RenderRoutingRequestIR, context: RenderRoutingContextIR = {}): RenderRoutingResultIR {
  validateRequest(request);
  const hardware = request.hardwareBackend && request.hardwareBackend !== "NONE" ? request.hardwareBackend : undefined;
  if (hardware || ["CUDA", "OPTIX", "HIP", "METAL", "ONEAPI"].includes(request.backend)) {
    if (!context.serverRenderAvailable) return blocked("SERVER_JOB", "HARDWARE_SERVER_RENDER", "HARDWARE_BACKEND_REQUIRES_SERVER", "SERVER_JOB_UNAVAILABLE", `Hardware backend ${hardware ?? request.backend} requires a configured server render job`);
    return ready("SERVER_JOB", "HARDWARE_SERVER_RENDER", "HARDWARE_BACKEND_REQUIRES_SERVER");
  }
  if (request.renderEngine === "BLENDER_CYCLES" || request.backend === "CYCLES") {
    if (!context.serverRenderAvailable) return blocked("SERVER_JOB", "CYCLES_SERVER_RENDER", "CYCLES_REQUIRES_SERVER", "SERVER_JOB_UNAVAILABLE", "Cycles final rendering requires a configured server render job");
    return ready("SERVER_JOB", "CYCLES_SERVER_RENDER", "CYCLES_REQUIRES_SERVER");
  }
  if (request.renderEngine === "BLENDER_WORKBENCH") {
    if (!context.serverRenderAvailable) return blocked("SERVER_JOB", "WORKBENCH_SERVER_RENDER", "WORKBENCH_REQUIRES_SERVER", "SERVER_JOB_UNAVAILABLE", "Workbench final rendering is not a Web realtime equivalent and requires a configured server render job");
    return ready("SERVER_JOB", "WORKBENCH_SERVER_RENDER", "WORKBENCH_REQUIRES_SERVER");
  }
  if (request.renderEngine === "BLENDER_EEVEE" || request.renderEngine === "BLENDER_EEVEE_NEXT") {
    if (request.complexity === "COMPLEX" || request.backend === "EEVEE_COMPLEX") {
      if (!context.serverRenderAvailable) return blocked("SERVER_JOB", "COMPLEX_EEVEE_SERVER_RENDER", "COMPLEX_EEVEE_REQUIRES_SERVER", "SERVER_JOB_UNAVAILABLE", "Complex Eevee final rendering requires a configured server render job");
      return ready("SERVER_JOB", "COMPLEX_EEVEE_SERVER_RENDER", "COMPLEX_EEVEE_REQUIRES_SERVER");
    }
    if (request.backend === "WEBGPU" && !(context.webgpuAvailable && context.webgpuRendererBundled)) {
      return blocked("WEB_LOCAL_BOUNDED", "WEB_REALTIME_BOUNDED", "WEBGPU_UNAVAILABLE", "WEBGPU_RENDERER_UNAVAILABLE", "The requested WebGPU realtime renderer is unavailable");
    }
    if (request.backend !== "WEBGL2" && request.backend !== "WEBGPU") throw new Error("INVALID_ARGUMENT: bounded Eevee requires WEBGL2 or WEBGPU");
    return ready("WEB_LOCAL_BOUNDED", "WEB_REALTIME_BOUNDED", "BOUNDED_EEVEE");
  }
  return blocked("SERVER_JOB", "UNSUPPORTED_RENDER_ENGINE", "UNSUPPORTED_ENGINE", "PLATFORM_CAPABILITY_UNAVAILABLE", "The requested render engine has no declared Web or server route");
}