import { RP2040, GPIOPinState, ConsoleLogger, LogLevel, USBCDC } from 'rp2040js';
import type { RPI2C } from 'rp2040js';
import { PinManager } from './PinManager';
import { I2CBusManager, wireRpI2cToBus, nullI2CMaster } from './I2CBusManager';
import type { I2CDevice } from './I2CBusManager';
import { bootromB1 } from './rp2040-bootrom';
import { loadUF2, loadUserFiles, getFirmware } from './MicroPythonLoader';
import {
  Cyw43Emulator,
  PioBusSniffer,
  type Cyw43Bridge,
  type LedEvent,
  type PacketOutEvent,
} from './cyw43';

/**
 * RP2040Simulator — Emulates Raspberry Pi Pico (RP2040) using rp2040js
 *
 * Features:
 * - ARM Cortex-M0+ dual-core Cortex-M0+ CPU at 125 MHz (single-core emulated)
 * - 30 GPIO pins (GPIO0-GPIO29)  xc fv       nn
 * - 2× UART, 2× SPI, 2× I2C
 * - ADC on GPIO26-GPIO29 (A0-A3) + internal temp sensor (ch4)
 * - PWM on any GPIO
 * - LED_BUILTIN on GPIO25
 * - Full bootrom B1 for proper boot sequence
 *
 * Arduino-pico pin mapping (Earle Philhower's core):
 *   D0  = GPIO0   … D29 = GPIO29
 *   A0  = GPIO26  … A3  = GPIO29
 *   LED_BUILTIN = GPIO25
 *   Default Serial  → UART0 (GPIO0=TX, GPIO1=RX)
 *   Default I2C     → I2C0  (GPIO4=SDA, GPIO5=SCL)
 *   Default SPI     → SPI0  (GPIO16=MISO, GPIO19=MOSI, GPIO18=SCK, GPIO17=CS)
 */

const F_CPU = 125_000_000; // 125 MHz
const CYCLE_NANOS = 1e9 / F_CPU; // nanoseconds per cycle (~8 ns)
const FPS = 60;
const CYCLES_PER_FRAME = Math.floor(F_CPU / FPS); // ~2 083 333

/**
 * Backward-compatible alias for the unified `I2CDevice` shape used by
 * both AVR and RP2040 buses now that I2CBusManager is the canonical
 * abstraction.  Existing call sites that import `RP2040I2CDevice` keep
 * working without changes.
 */
export type RP2040I2CDevice = I2CDevice;

export class RP2040Simulator {
  private rp2040: RP2040 | null = null;
  private running = false;
  private animationFrame: number | null = null;
  public pinManager: PinManager;
  private speed = 1.0;
  private gpioUnsubscribers: Array<() => void> = [];
  private flashCopy: Uint8Array | null = null;
  private totalCycles = 0;
  private scheduledPinChanges: Array<{ cycle: number; pin: number; state: boolean }> = [];
  private pioStepAccum = 0;
  private usbCDC: USBCDC | null = null;
  private micropythonMode = false;

  // ── Pico W WiFi (CYW43439) — only attached when boardKind === 'pi-pico-w'.
  private cyw43: Cyw43Emulator | null = null;
  private cyw43Sniffer: PioBusSniffer | null = null;
  private cyw43Bridge: Cyw43Bridge | null = null;
  private cyw43HookedFifos: Array<{ restore: () => void }> = [];

  /** Serial output callback — fires for each byte the Pico sends on UART0 (or USBCDC in MicroPython mode) */
  public onSerialData: ((char: string) => void) | null = null;

  /**
   * Generic SPI bus adapter — same shape as AVRSimulator.spi so SPI parts
   * (ILI9341, SD cards, custom chips) can hook the bus uniformly across
   * boards. Defaults to RP2040 SPI0; firmware that uses SPI1 will need to
   * wrap rp2040.spi[1] manually until we add a .spi1 alias.
   *
   * Lazy-initialised so the rp2040.spi[0].onTransmit is only overridden
   * once a part actually accesses .spi (avoiding clobbering the default
   * loopback handler if no SPI part is on the canvas).
   */
  private _spiAdapter: { onByte: ((mosi: number) => void) | null;
                         completeTransfer: (miso: number) => void } | null = null;
  public get spi(): { onByte: ((mosi: number) => void) | null;
                      completeTransfer: (miso: number) => void } {
    if (!this._spiAdapter) {
      const adapter = {
        onByte: null as ((mosi: number) => void) | null,
        completeTransfer: (miso: number) => {
          this.rp2040?.spi[0].completeTransmit(miso & 0xff);
        },
      };
      // Re-route SPI0's onTransmit through our adapter when initMCU /
      // initMicroPython runs. Until rp2040 is constructed (mcu=null) the
      // setter just stages the handler — we wire it in start().
      this._spiAdapter = adapter;
      if (this.rp2040) {
        this.rp2040.spi[0].onTransmit = (v: number) => adapter.onByte?.(v);
      }
    }
    return this._spiAdapter;
  }

  /** Fires when the on-board LED on Pico W (driven through the CYW43, not GPIO 25) toggles. */
  public onPicoWLed: ((on: boolean) => void) | null = null;
  /** Fires whenever the chip emits a Wi-Fi link-up event for the synthetic AP. */
  public onPicoWWifiUp: ((ssid: string) => void) | null = null;

  /**
   * Fires for every GPIO pin transition with a millisecond timestamp.
   * Used by the oscilloscope / logic analyzer.
   * timeMs is derived from the RP2040 cycle counter (cycles / F_CPU * 1000).
   */
  public onPinChangeWithTime: ((pin: number, state: boolean, timeMs: number) => void) | null = null;

  /**
   * One `I2CBusManager` per hardware I2C controller (RP2040 has two:
   * I2C0/Wire and I2C1/Wire1).  Constructed up-front in the
   * simulator's constructor with a placeholder master so that cross-
   * board bridges + device registrations can land BEFORE firmware
   * loads.  The real RPI2C peripheral takes over in `wireI2C()` via
   * `attachMaster` + `wireRpI2cToBus`.
   */
  private i2cBuses: [I2CBusManager, I2CBusManager];

  constructor(pinManager: PinManager) {
    this.pinManager = pinManager;
    this.i2cBuses = [
      new I2CBusManager(nullI2CMaster()),
      new I2CBusManager(nullI2CMaster()),
    ];
  }

  /**
   * Load a compiled binary into the RP2040 flash memory.
   * Accepts a base64-encoded string of the raw .bin file output by arduino-cli.
   */
  loadBinary(base64: string): void {
    console.log('[RP2040] Loading binary...');

    const binaryStr = atob(base64);
    const bytes = new Uint8Array(binaryStr.length);
    for (let i = 0; i < binaryStr.length; i++) {
      bytes[i] = binaryStr.charCodeAt(i);
    }

    console.log(`[RP2040] Binary size: ${bytes.length} bytes`);
    this.flashCopy = bytes;

    this.initMCU(bytes);
    console.log('[RP2040] CPU initialized with bootrom, UART, I2C, SPI, GPIO');
  }

  /** Same interface as AVRSimulator for store compatibility */
  // eslint-disable-next-line @typescript-eslint/no-unused-vars
  loadHex(_hexContent: string): void {
    console.warn('[RP2040] loadHex() called on RP2040Simulator — use loadBinary() instead');
  }

  /**
   * Load MicroPython firmware + user .py files into RP2040 flash.
   * Uses USBCDC for serial (REPL) instead of UART.
   */
  async loadMicroPython(
    files: Array<{ name: string; content: string }>,
    onProgress?: (loaded: number, total: number) => void,
  ): Promise<void> {
    console.log('[RP2040] Loading MicroPython firmware...');

    // 1. Get MicroPython UF2 firmware (cached in IndexedDB)
    const firmware = await getFirmware(onProgress);

    // 2. Create fresh RP2040 instance
    this.rp2040 = new RP2040();
    this.rp2040.logger = new ConsoleLogger(LogLevel.Error);
    this.rp2040.loadBootrom(bootromB1);

    // 3. Load UF2 firmware into flash
    loadUF2(firmware, this.rp2040.flash);
    console.log(`[RP2040] MicroPython UF2 loaded (${firmware.length} bytes)`);

    // 4. Create LittleFS with user files and load into flash
    await loadUserFiles(files, this.rp2040.flash);
    console.log(`[RP2040] LittleFS loaded with ${files.length} file(s)`);

    // Keep a flash copy for reset
    this.flashCopy = new Uint8Array(this.rp2040.flash);

    // 5. Set up USBCDC for serial REPL (instead of UART)
    this.usbCDC = new USBCDC(this.rp2040.usbCtrl);
    this.usbCDC.onDeviceConnected = () => {
      // Send newline to trigger the REPL prompt
      this.usbCDC!.sendSerialByte('\r'.charCodeAt(0));
      this.usbCDC!.sendSerialByte('\n'.charCodeAt(0));
    };
    this.usbCDC.onSerialData = (buffer: Uint8Array) => {
      for (const byte of buffer) {
        if (this.onSerialData) {
          this.onSerialData(String.fromCharCode(byte));
        }
      }
    };

    // 6. Set PC to flash start
    this.rp2040.core.PC = 0x10000000;

    // 7. Wire peripherals (I2C, SPI, ADC, PIO, GPIO — same as Arduino mode)
    // But skip UART serial wiring since MicroPython uses USBCDC
    this.rp2040.uart[1].onByte = (value: number) => {
      if (this.onSerialData) this.onSerialData(String.fromCharCode(value));
    };
    this.wireI2C(0);
    this.wireI2C(1);
    // Default loopback for SPI0 — overridden by the generic .spi adapter
    // if a SPI part later accesses simulator.spi. The adapter routes
    // onTransmit into adapter.onByte and uses completeTransmit to drive
    // MISO when the part calls completeTransfer.
    this.rp2040.spi[0].onTransmit = (v: number) => {
      if (this._spiAdapter && this._spiAdapter.onByte) {
        this._spiAdapter.onByte(v);
      } else {
        this.rp2040!.spi[0].completeTransmit(v);
      }
    };
    this.rp2040.spi[1].onTransmit = (v: number) => {
      this.rp2040!.spi[1].completeTransmit(v);
    };
    this.rp2040.adc.channelValues[0] = 2048;
    this.rp2040.adc.channelValues[1] = 2048;
    this.rp2040.adc.channelValues[2] = 2048;
    this.rp2040.adc.channelValues[3] = 2048;
    this.rp2040.adc.channelValues[4] = 876;

    // Patch PIO (same as initMCU)
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    for (const pio of (this.rp2040 as any).pio) {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      pio.run = function (this: any) {
        if (this.runTimer) {
          clearTimeout(this.runTimer);
          this.runTimer = null;
        }
      };
    }
    this.pioStepAccum = 0;

    this.setupGpioListeners();
    this.micropythonMode = true;
    console.log('[RP2040] MicroPython ready');
  }

  /** Returns true if currently in MicroPython mode */
  isMicroPythonMode(): boolean {
    return this.micropythonMode;
  }

  // ── Pico W (CYW43439) attachment ────────────────────────────────────────

  /**
   * Wire a CYW43 chip emulator onto this RP2040 instance. Should only be
   * called for ``pi-pico-w`` boards. Idempotent — calling twice is a no-op.
   *
   * The emulator observes outbound PIO TX FIFO writes (which the cyw43
   * driver uses to bit-bang the gSPI bus) and feeds back synthesised
   * responses. When a Cyw43Bridge is supplied, outbound Ethernet frames
   * are forwarded to the backend network bridge and inbound packets
   * coming back from the bridge are queued for the chip to deliver.
   */
  attachCyw43(bridge: Cyw43Bridge | null = null): Cyw43Emulator {
    if (this.cyw43) return this.cyw43;
    const emu = new Cyw43Emulator();
    const sniffer = new PioBusSniffer();
    this.cyw43 = emu;
    this.cyw43Sniffer = sniffer;
    this.cyw43Bridge = bridge;

    emu.onLed((ev: LedEvent) => {
      this.onPicoWLed?.(ev.on);
    });
    emu.onConnect((ev) => {
      this.onPicoWWifiUp?.(ev.ssid);
    });
    emu.onPacketOut((ev: PacketOutEvent) => {
      this.cyw43Bridge?.sendPacket(ev.ether);
    });

    if (bridge) {
      bridge.onPacketIn = (p) => emu.injectPacket(p.ether);
    }

    this.installCyw43PioHooks();
    return emu;
  }

  /** Detach the CYW43 emulator (called from teardown). */
  detachCyw43(): void {
    for (const h of this.cyw43HookedFifos) h.restore();
    this.cyw43HookedFifos = [];
    this.cyw43 = null;
    this.cyw43Sniffer = null;
    this.cyw43Bridge = null;
  }

  /** Read access for tests / debug panels. */
  getCyw43(): Cyw43Emulator | null { return this.cyw43; }

  /**
   * Hook every PIO state machine's ``txFIFO.push`` so the CYW43 emulator
   * sees every word the cyw43 driver bit-bangs onto the bus, and
   * mirror responses back into ``rxFIFO`` so the driver's reads land
   * without needing a real chip on the wire.
   */
  private installCyw43PioHooks(): void {
    if (!this.rp2040 || !this.cyw43 || !this.cyw43Sniffer) return;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const pios: any[] = (this.rp2040 as any).pio;
    for (const pio of pios) {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      for (const sm of pio.machines as any[]) {
        const tx = sm.txFIFO;
        const rx = sm.rxFIFO;
        if (!tx || !rx) continue;
        const origPush: (v: number) => void = tx.push.bind(tx);
        tx.push = (value: number) => {
          // Feed the gSPI sniffer; if the command produces a response,
          // surface it word-by-word into the rxFIFO so the driver's
          // `pull` instruction reads it back.
          this.feedCyw43Word(value);
          return origPush(value);
        };
        this.cyw43HookedFifos.push({
          restore: () => { tx.push = origPush; },
        });
      }
    }
  }

  private cyw43RxQueue: number[] = [];
  private feedCyw43Word(word: number): void {
    if (!this.cyw43Sniffer || !this.cyw43) return;
    for (const ev of this.cyw43Sniffer.feedWord(word)) {
      if (ev.kind === 'payload') {
        const reply = this.cyw43.onCommand(ev.cmd, ev.payload);
        if (reply && reply.length > 0) this.queueCyw43Reply(reply);
      }
    }
    // Drain queued reply words into any state machine that has space.
    this.drainCyw43RxIntoSomeSM();
  }

  private queueCyw43Reply(reply: Uint8Array): void {
    // 32-bit big-endian repacking with the same halfword swap the PIO
    // program does on input. We push host-byte-order words; the SM's
    // shift register puts them on the wire LSB-first per the gSPI spec.
    for (let i = 0; i + 4 <= reply.length; i += 4) {
      const w =
        ((reply[i + 3] << 24) | (reply[i + 2] << 16) | (reply[i + 1] << 8) | reply[i]) >>> 0;
      this.cyw43RxQueue.push(w);
    }
    if (reply.length % 4 !== 0) {
      // Pad to 4 bytes with zeros — the driver discards trailing bytes
      // it didn't request.
      const tail = reply.subarray(reply.length - (reply.length % 4));
      let w = 0;
      for (let i = 0; i < tail.length; i++) w |= tail[i] << (i * 8);
      this.cyw43RxQueue.push(w >>> 0);
    }
  }

  private drainCyw43RxIntoSomeSM(): void {
    if (!this.rp2040 || this.cyw43RxQueue.length === 0) return;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const pios: any[] = (this.rp2040 as any).pio;
    for (const pio of pios) {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      for (const sm of pio.machines as any[]) {
        const rx = sm.rxFIFO;
        if (!rx) continue;
        while (this.cyw43RxQueue.length > 0 && !rx.full) {
          rx.push(this.cyw43RxQueue.shift());
        }
        if (this.cyw43RxQueue.length === 0) return;
      }
    }
  }

  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  getADC(): any {
    return this.rp2040?.adc ?? null;
  }

  /** Get underlying RP2040 instance (for advanced usage / tests) */
  getMCU(): RP2040 | null {
    return this.rp2040;
  }

  // ── Private initialization ───────────────────────────────────────────────

  private initMCU(programBytes: Uint8Array): void {
    this.rp2040 = new RP2040();

    // Suppress noisy internal logs (only show errors)
    this.rp2040.logger = new ConsoleLogger(LogLevel.Error);

    // Load RP2040 B1 bootrom — needed for proper boot sequence
    this.rp2040.loadBootrom(bootromB1);

    // Load binary into flash starting at offset 0 (maps to 0x10000000)
    this.rp2040.flash.set(programBytes, 0);

    // Set PC to flash start (boot vector)
    this.rp2040.core.PC = 0x10000000;

    // ── Wire UART0 (default Serial port for Arduino-Pico) ────────────
    let serialBuffer = '';
    this.rp2040.uart[0].onByte = (value: number) => {
      const ch = String.fromCharCode(value);
      serialBuffer += ch;
      if (ch === '\n') {
        console.log('[RP2040 UART0]', serialBuffer.trimEnd());
        serialBuffer = '';
      }
      if (this.onSerialData) {
        this.onSerialData(ch);
      }
    };

    // ── Wire UART1 (Serial1) — also forward to onSerialData for now ──
    this.rp2040.uart[1].onByte = (value: number) => {
      if (this.onSerialData) {
        this.onSerialData(String.fromCharCode(value));
      }
    };

    // ── Wire I2C0 and I2C1 ───────────────────────────────────────────
    this.wireI2C(0);
    this.wireI2C(1);

    // ── Wire SPI0 and SPI1 ────────────────────────────────────────────
    // SPI0 must check for a registered .spi adapter on every byte. If a
    // part on the canvas (ILI9341, custom chip, …) accessed simulator.spi
    // BEFORE this initMCU runs, the adapter is already staged but
    // _adapter.onByte points at the part's handler — we have to route
    // the byte through it. Without this, SPI parts see nothing and the
    // canvas stays black (real regression — Pico Doom shipped with this
    // bug for months because the same wiring in initMicroPython was
    // adapter-aware but this Arduino path wasn't).
    this.rp2040.spi[0].onTransmit = (v: number) => {
      if (this._spiAdapter && this._spiAdapter.onByte) {
        this._spiAdapter.onByte(v);
      } else {
        this.rp2040!.spi[0].completeTransmit(v);
      }
    };
    this.rp2040.spi[1].onTransmit = (value: number) => {
      this.rp2040!.spi[1].completeTransmit(value); // loopback
    };

    // ── Set default ADC values ───────────────────────────────────────
    // Channel 0-3: GPIO26-29, channel 4: internal temp sensor
    // Default to mid-range (~1.65V on 3.3V ref, 12-bit)
    this.rp2040.adc.channelValues[0] = 2048;
    this.rp2040.adc.channelValues[1] = 2048;
    this.rp2040.adc.channelValues[2] = 2048;
    this.rp2040.adc.channelValues[3] = 2048;
    // Internal temp sensor: T = 27 - (V - 0.706) / 0.001721
    // For 27°C: V = 0.706V → ADC = 0.706/3.3 * 4095 ≈ 876
    this.rp2040.adc.channelValues[4] = 876;

    // ── Patch PIO to use synchronous stepping instead of setTimeout ──
    // rp2040js PIO uses setTimeout(() => this.run(), 0) which deadlocks
    // when the CPU busy-waits for PIO FIFO space (e.g. pio_sm_put_blocking).
    // We step PIO synchronously in the execute loop instead.
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    for (const pio of (this.rp2040 as any).pio) {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      pio.run = function (this: any) {
        if (this.runTimer) {
          clearTimeout(this.runTimer);
          this.runTimer = null;
        }
        // No-op: execute loop calls pio.step() synchronously
      };
    }
    this.pioStepAccum = 0;

    // ── Set up GPIO listeners ────────────────────────────────────────
    this.setupGpioListeners();
  }

  private wireI2C(bus: 0 | 1): void {
    if (!this.rp2040) return;
    const i2c: RPI2C = this.rp2040.i2c[bus];
    // Swap in the real RPI2C peripheral and route its per-callback
    // events into the existing bus manager.  Any devices + bridges
    // registered before the firmware loaded are preserved.
    const busManager = this.i2cBuses[bus];
    busManager.attachMaster(i2c);
    wireRpI2cToBus(i2c, busManager);
  }

  private setupGpioListeners(): void {
    this.gpioUnsubscribers.forEach((fn) => fn());
    this.gpioUnsubscribers = [];

    if (!this.rp2040) return;

    for (let gpioIdx = 0; gpioIdx < 30; gpioIdx++) {
      const pin = gpioIdx;
      const gpio = this.rp2040.gpio[gpioIdx];
      if (!gpio) continue;

      const unsub = gpio.addListener((state: GPIOPinState) => {
        const isHigh = state === GPIOPinState.High || state === GPIOPinState.InputPullUp;
        this.pinManager.triggerPinChange(pin, isHigh);
        if (this.onPinChangeWithTime && this.rp2040) {
          // IClock interface exposes `nanos` (not `timeUs`)
          // eslint-disable-next-line @typescript-eslint/no-explicit-any
          const clk = (this.rp2040 as any).clock;
          const timeMs = clk ? (clk.nanos as number) / 1_000_000 : 0;
          this.onPinChangeWithTime(pin, isHigh, timeMs);
        }
      });
      this.gpioUnsubscribers.push(unsub);
    }
  }

  // ── Public API ───────────────────────────────────────────────────────────

  start(): void {
    if (this.running || !this.rp2040) {
      console.warn('[RP2040] Already running or not initialized');
      return;
    }

    this.running = true;
    console.log('[RP2040] Starting simulation at 125 MHz...');

    const execute = () => {
      if (!this.running || !this.rp2040) return;

      const cyclesTarget = Math.floor(CYCLES_PER_FRAME * this.speed);
      const { core } = this.rp2040;
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      const clock = (this.rp2040 as any).clock;

      try {
        let cyclesDone = 0;
        const pioDiv = this.getPIOClockDiv();
        while (cyclesDone < cyclesTarget) {
          if (core.waiting) {
            if (clock) {
              const jump: number = clock.nanosToNextAlarm;
              if (jump <= 0) {
                // No clock alarms — step PIO so it can unblock the CPU
                // (e.g. PIO consuming FIFO data may generate an interrupt)
                this.stepPIO();
                break;
              }
              const jumped = Math.ceil(jump / CYCLE_NANOS);
              const pioSteps = Math.floor(jumped / pioDiv);
              // Advance clock incrementally per PIO step so GPIO transitions
              // get accurate timestamps (not all lumped at the end of the jump).
              const nanoPerPioStep = pioDiv * CYCLE_NANOS;
              const maxSteps = Math.min(pioSteps, 50000);
              let nanosStepped = 0;
              for (let i = 0; i < maxSteps; i++) {
                clock.tick(nanoPerPioStep);
                nanosStepped += nanoPerPioStep;
                this.totalCycles += pioDiv;
                this.stepPIO();
              }
              // Tick any remaining nanoseconds not covered by PIO steps
              const remaining = jump - nanosStepped;
              if (remaining > 0) {
                clock.tick(remaining);
                this.totalCycles += Math.ceil(remaining / CYCLE_NANOS);
              }
              cyclesDone += jumped;
              this.flushScheduledPinChanges();
            } else {
              break;
            }
          } else {
            const cycles: number = core.executeInstruction();
            if (clock) clock.tick(cycles * CYCLE_NANOS);
            cyclesDone += cycles;
            this.totalCycles += cycles;
            // Step PIO synchronously at the PIO clock rate
            this.pioStepAccum += cycles;
            while (this.pioStepAccum >= pioDiv) {
              this.pioStepAccum -= pioDiv;
              this.stepPIO();
            }
            this.flushScheduledPinChanges();
          }
        }
      } catch (error) {
        console.error('[RP2040] Simulation error:', error);
        this.stop();
        return;
      }

      this.animationFrame = requestAnimationFrame(execute);
    };

    this.animationFrame = requestAnimationFrame(execute);
  }

  stop(): void {
    if (!this.running) return;
    this.running = false;
    if (this.animationFrame !== null) {
      cancelAnimationFrame(this.animationFrame);
      this.animationFrame = null;
    }
    console.log('[RP2040] Simulation stopped');
  }

  reset(): void {
    this.stop();
    this.totalCycles = 0;
    this.scheduledPinChanges = [];
    if (this.rp2040 && this.flashCopy) {
      if (this.micropythonMode) {
        // In MicroPython mode, restore the full flash snapshot (UF2 + LittleFS)
        this.rp2040 = new RP2040();
        this.rp2040.logger = new ConsoleLogger(LogLevel.Error);
        this.rp2040.loadBootrom(bootromB1);
        this.rp2040.flash.set(this.flashCopy);
        this.rp2040.core.PC = 0x10000000;

        // Re-wire USBCDC
        this.usbCDC = new USBCDC(this.rp2040.usbCtrl);
        this.usbCDC.onDeviceConnected = () => {
          this.usbCDC!.sendSerialByte('\r'.charCodeAt(0));
          this.usbCDC!.sendSerialByte('\n'.charCodeAt(0));
        };
        this.usbCDC.onSerialData = (buffer: Uint8Array) => {
          for (const byte of buffer) {
            if (this.onSerialData) this.onSerialData(String.fromCharCode(byte));
          }
        };

        // Re-wire peripherals (skipping UART0 serial)
        this.rp2040.uart[1].onByte = (value: number) => {
          if (this.onSerialData) this.onSerialData(String.fromCharCode(value));
        };
        this.wireI2C(0);
        this.wireI2C(1);
        this.rp2040.spi[0].onTransmit = (v: number) => {
          this.rp2040!.spi[0].completeTransmit(v);
        };
        this.rp2040.spi[1].onTransmit = (v: number) => {
          this.rp2040!.spi[1].completeTransmit(v);
        };
        // eslint-disable-next-line @typescript-eslint/no-explicit-any
        for (const pio of (this.rp2040 as any).pio) {
          // eslint-disable-next-line @typescript-eslint/no-explicit-any
          pio.run = function (this: any) {
            if (this.runTimer) {
              clearTimeout(this.runTimer);
              this.runTimer = null;
            }
          };
        }
        this.pioStepAccum = 0;
        this.setupGpioListeners();
      } else {
        this.initMCU(this.flashCopy);
      }
      console.log('[RP2040] CPU reset');
    }
  }

  isRunning(): boolean {
    return this.running;
  }

  setSpeed(speed: number): void {
    this.speed = Math.max(0.1, Math.min(10.0, speed));
  }

  getSpeed(): number {
    return this.speed;
  }

  /** Returns the CPU clock frequency in Hz. */
  getClockHz(): number {
    return F_CPU;
  }

  /** Returns total CPU cycles executed since last reset/load. */
  getCurrentCycles(): number {
    return this.totalCycles;
  }

  /**
   * Schedule a GPIO pin state change at a specific future cycle count.
   * Enables cycle-accurate protocol simulation (e.g. HC-SR04 echo timing).
   */
  schedulePinChange(pin: number, state: boolean, atCycle: number): void {
    let i = this.scheduledPinChanges.length;
    while (i > 0 && this.scheduledPinChanges[i - 1].cycle > atCycle) i--;
    this.scheduledPinChanges.splice(i, 0, { cycle: atCycle, pin, state });
  }

  /** Get the PIO clock divider from the first enabled state machine. */
  private getPIOClockDiv(): number {
    if (!this.rp2040) return 64;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    for (const pio of (this.rp2040 as any).pio) {
      if (pio.stopped) continue;
      for (const m of pio.machines) {
        if (m.enabled) {
          return Math.max(1, m.clockDivInt || 1);
        }
      }
    }
    return 64; // default
  }

  /** Step PIO state machines synchronously (prevents setTimeout deadlock). */
  private stepPIO(): void {
    if (!this.rp2040) return;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const pio = (this.rp2040 as any).pio;
    if (pio[0] && !pio[0].stopped) pio[0].step();
    if (pio[1] && !pio[1].stopped) pio[1].step();
  }

  private flushScheduledPinChanges(): void {
    if (this.scheduledPinChanges.length === 0) return;
    while (
      this.scheduledPinChanges.length > 0 &&
      this.scheduledPinChanges[0].cycle <= this.totalCycles
    ) {
      const { pin, state } = this.scheduledPinChanges.shift()!;
      this.setPinState(pin, state);
    }
  }

  /**
   * Drive a GPIO pin externally (e.g. from a button or slider).
   * GPIO n = Arduino D(n) for Raspberry Pi Pico.
   */
  setPinState(arduinoPin: number, state: boolean): void {
    if (!this.rp2040) return;
    const gpio = this.rp2040.gpio[arduinoPin];
    if (gpio) {
      gpio.setInputValue(state);
    }
  }

  /**
   * Send text to UART0 RX (or USBCDC in MicroPython mode).
   */
  serialWrite(text: string): void {
    if (!this.rp2040) return;
    if (this.micropythonMode && this.usbCDC) {
      for (let i = 0; i < text.length; i++) {
        this.usbCDC.sendSerialByte(text.charCodeAt(i));
      }
    } else {
      for (let i = 0; i < text.length; i++) {
        this.rp2040.uart[0].feedByte(text.charCodeAt(i));
      }
    }
  }

  /**
   * Send a raw byte to the serial interface (for control characters like Ctrl+C).
   */
  serialWriteByte(byte: number): void {
    if (!this.rp2040) return;
    if (this.micropythonMode && this.usbCDC) {
      this.usbCDC.sendSerialByte(byte);
    } else {
      this.rp2040.uart[0].feedByte(byte);
    }
  }

  /**
   * Register a virtual I2C device on the specified bus (0 or 1).
   * Default bus 0 = Wire, bus 1 = Wire1.  Devices are added directly
   * to the bus manager (which exists from construction time, with a
   * placeholder master until the real RPI2C is wired in start()).
   */
  addI2CDevice(device: I2CDevice, bus: 0 | 1 = 0): void {
    this.i2cBuses[bus].addDevice(device);
  }

  /** Remove an I2C device by address from the given bus. */
  removeI2CDevice(address: number, bus: 0 | 1 = 0): void {
    this.i2cBuses[bus].removeDevice(address);
  }

  /**
   * Get the I2CBusManager for a given hardware bus (0 or 1).
   * Available from construction time so Interconnect can install
   * cross-board bridges before firmware loads.
   */
  getI2CBus(bus: 0 | 1 = 0): I2CBusManager {
    return this.i2cBuses[bus];
  }

  /**
   * Execute one ARM instruction synchronously and return the number
   * of CPU cycles it took.  Mirrors `AVRSimulator.step()` for tests
   * that need deterministic single-stepping outside the
   * `requestAnimationFrame` loop used in production.  No-op if the
   * firmware has not been loaded.
   *
   * Does NOT advance PIO or fire scheduled pin changes — for those
   * use the production `start()` loop or call `stepCycles(n)`.
   */
  step(): number {
    if (!this.rp2040) return 0;
    const core = this.rp2040.core;
    const clock = this.rp2040.clock;
    if (core.waiting) {
      // CPU is in WFE/WFI — advance clock to the next alarm so an
      // interrupt can wake it.  Without this, single-stepping a
      // waiting CPU spins indefinitely.
      const jump = clock?.nanosToNextAlarm ?? CYCLE_NANOS;
      if (jump > 0 && clock) clock.tick(jump);
      this.totalCycles += Math.ceil((jump || CYCLE_NANOS) / CYCLE_NANOS);
      return Math.ceil((jump || CYCLE_NANOS) / CYCLE_NANOS);
    }
    const cycles: number = core.executeInstruction();
    if (clock) clock.tick(cycles * CYCLE_NANOS);
    this.totalCycles += cycles;
    return cycles;
  }

  /**
   * Drive the CPU forward by approximately `targetCycles` cycles,
   * synchronously.  Useful for test harnesses that want bounded,
   * deterministic execution without depending on
   * `requestAnimationFrame`.  Returns the actual number of cycles
   * consumed (may exceed targetCycles by at most the cost of one
   * instruction).
   */
  stepCycles(targetCycles: number): number {
    let consumed = 0;
    while (consumed < targetCycles) {
      const c = this.step();
      if (c === 0) break; // firmware not loaded
      consumed += c;
    }
    return consumed;
  }

  /**
   * Set ADC channel value (0-4095 for 12-bit).
   * Channels 0-3 = GPIO26-29, channel 4 = internal temperature sensor.
   */
  setADCValue(channel: number, value: number): void {
    if (!this.rp2040) return;
    if (channel >= 0 && channel < 5) {
      this.rp2040.adc.channelValues[channel] = Math.max(0, Math.min(4095, value));
    }
  }

  /**
   * Set SPI onTransmit handler for a bus (0 or 1).
   * callback receives TX byte and must call completeTransmit on the SPI instance.
   */
  setSPIHandler(bus: 0 | 1, handler: (value: number) => number): void {
    if (!this.rp2040) return;
    const spi = this.rp2040.spi[bus];
    spi.onTransmit = (value: number) => {
      const response = handler(value);
      spi.completeTransmit(response);
    };
  }

  // ── Generic sensor registration (board-agnostic API) ──────────────────────
  // RP2040 handles all sensor protocols locally via schedulePinChange,
  // so these return false / no-op — the sensor runs its own frontend logic.

  registerSensor(_type: string, _pin: number, _props: Record<string, unknown>): boolean {
    return false;
  }
  updateSensor(_pin: number, _props: Record<string, unknown>): void {}
  unregisterSensor(_pin: number): void {}
}