"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import type { LoadPinballOptions, PinballInstance } from "@valknar/vpinball-wasm";
import { hasWebGL2 } from "./webglSupport";

// Served as a plain static file, not bundled — loadPinball() internally does
// a dynamic import(`${baseUrl}/vpinball.js`) with a template-literal path
// that webpack can't statically resolve, so the whole engine must stay
// outside webpack's module graph (see scripts/copy-engine-assets.mjs).
const ENGINE_BASE_URL = "/vendor/vpinball-wasm";

export type PinballStatus = "idle" | "loading" | "ready" | "starting" | "running" | "error";

interface EngineModule {
  loadPinball(options: LoadPinballOptions): Promise<PinballInstance>;
}

async function loadEngineModule(): Promise<EngineModule> {
  return (await import(
    /* webpackIgnore: true */ `${ENGINE_BASE_URL}/index.js`
  )) as EngineModule;
}

export interface UsePinballInstanceResult {
  status: PinballStatus;
  /** 0-1 download progress, only meaningful while status is "loading". */
  progress: number;
  error: string | null;
  loadTimeMs: number | null;
  instanceRef: React.RefObject<PinballInstance | null>;
  /** Call from a user-gesture handler (audio autoplay / fullscreen policy). */
  start: () => void;
}

export interface RomSelection {
  gameName: string;
  romData: ArrayBuffer;
}

export function usePinballInstance(
  canvasRef: React.RefObject<HTMLCanvasElement | null>,
  tableData: ArrayBuffer | undefined,
  rom: RomSelection | undefined,
): UsePinballInstanceResult {
  // Computed once at mount (not inside the effect below) so the WebGL2-
  // unsupported case is derived initial state rather than a setState call
  // that an effect makes only to immediately return.
  const [webgl2Supported] = useState(hasWebGL2);
  const [status, setStatus] = useState<PinballStatus>(webgl2Supported ? "idle" : "error");
  const [progress, setProgress] = useState(0);
  const [error, setError] = useState<string | null>(
    webgl2Supported ? null : "Your browser doesn't support WebGL2, which this pinball engine requires.",
  );
  const [loadTimeMs, setLoadTimeMs] = useState<number | null>(null);
  const instanceRef = useRef<PinballInstance | null>(null);
  const disposedRef = useRef(false);

  useEffect(() => {
    disposedRef.current = false;
    const canvas = canvasRef.current;
    if (!canvas || !webgl2Supported) return;

    // The engine sets a table-supplied image as the page favicon via a
    // blob: URL (see vpinball.js's rel~='icon' link handling) — undesirable
    // here, where the app's own favicon should stay put. Snapshot the
    // current icon links up front and revert any blob: href the moment it
    // appears, rather than patching the (compiled) engine itself.
    const originalIconHrefs = new Map<HTMLLinkElement, string>();
    document.querySelectorAll<HTMLLinkElement>("link[rel~='icon']").forEach((link) => {
      originalIconHrefs.set(link, link.href);
    });
    const faviconObserver = new MutationObserver(() => {
      document.querySelectorAll<HTMLLinkElement>("link[rel~='icon']").forEach((link) => {
        if (!link.href.startsWith("blob:")) return;
        const blobUrl = link.href;
        const original = originalIconHrefs.get(link);
        if (original) link.href = original;
        else link.remove();
        URL.revokeObjectURL(blobUrl);
      });
    });
    faviconObserver.observe(document.head, {
      childList: true,
      subtree: true,
      attributes: true,
      attributeFilter: ["href"],
    });

    setStatus("loading");
    const startedAt = performance.now();

    (async () => {
      try {
        const { loadPinball } = await loadEngineModule();
        const instance = await loadPinball({
          canvas,
          baseUrl: ENGINE_BASE_URL,
          tableData,
          onProgress: (fraction) => {
            if (!disposedRef.current) setProgress(fraction);
          },
        });
        if (disposedRef.current) {
          instance.dispose();
          return;
        }
        if (rom) {
          try {
            // Must run before start() — Controller.Run() reads the ROM
            // file synchronously at table-init time. A bad/mismatched ROM
            // zip fails cleanly inside the engine rather than here, so this
            // is defensive against loadRom() itself throwing (e.g. a
            // corrupt zip), not something expected to fire routinely.
            instance.loadRom(rom.gameName, rom.romData);
          } catch (err) {
            console.error("Failed to load ROM:", err);
          }
        }
        instanceRef.current = instance;
        setLoadTimeMs(performance.now() - startedAt);
        setStatus("ready");
      } catch (err) {
        if (!disposedRef.current) {
          setStatus("error");
          setError(err instanceof Error ? err.message : "Failed to load the pinball engine.");
        }
      }
    })();

    return () => {
      faviconObserver.disconnect();
      disposedRef.current = true;
      const instance = instanceRef.current;
      instanceRef.current = null;
      if (instance) {
        // stop() halts the engine's render loop, but only takes effect on
        // its next internal step rather than immediately. Calling dispose()
        // synchronously right after — freeing WASM memory before that step
        // runs — is what hangs the tab. Give it a couple of frames first.
        instance.stop();
        requestAnimationFrame(() => {
          requestAnimationFrame(() => {
            instance.dispose();
          });
        });
      }
    };
    // Intentionally run once: PlayView mounts a fresh PinballCanvasImpl
    // (via `key`) per table rather than swapping tableData in place.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  const start = useCallback(() => {
    if (!instanceRef.current) return;
    setStatus("starting");
    // instance.start() runs synchronously and blocks the main thread for a
    // noticeable moment (heavy WASM init) — a nested rAF lets the browser
    // paint the "starting" spinner from the state update above before that
    // block hits, instead of the UI freezing on the old screen mid-click.
    requestAnimationFrame(() => {
      requestAnimationFrame(() => {
        if (disposedRef.current || !instanceRef.current) return;
        instanceRef.current.start();
        setStatus("running");
      });
    });
  }, []);

  return { status, progress, error, loadTimeMs, instanceRef, start };
}