/*
 * ps4_lego_onebrain.ino
 *
 * One ESP32. PS4 controller over Bluetooth Classic (Bluepad32/BTstack) AND two
 * LEGO Powered Up hubs over BLE, driven by a hand-rolled LWP3 GATT client that
 * runs on the same BTstack instance.
 *
 * Board package: esp32-bluepad32 4.1.0  (NOT the plain esp32 package)
 * Libraries:     none. No Legoino, no NimBLE - they would be a second host
 *                stack and that is exactly what we are avoiding.
 *
 * BEFORE THIS WILL COMPILE:
 *   The board package ships the BTstack headers but does not put them on the
 *   include path. You must add a platform.local.txt to the package folder
 *   first - see docs/BUILD.md. Without it you get:
 *     fatal error: btstack.h: No such file or directory
 *
 * THREADING - read this before changing anything:
 *   BTstack is not thread-safe. loop() runs in the Arduino task, BTstack runs
 *   in its own task. The only BTstack call allowed from loop() is
 *   btstack_run_loop_execute_on_main_thread(). Everything LEGO-related here
 *   therefore runs inside a repeating BTstack timer (legoTickHandler), which
 *   executes on the BTstack thread. loop() only ever writes plain ints into
 *   gDesired; the timer reads them.
 *
 * BOOT ORDER:
 *   Gamepad discovery starts disabled. We connect both hubs first, then turn
 *   discovery on. This stops Bluepad32's inquiry/scan from colliding with our
 *   LE create-connection.
 *
 * Created by: Jess Rogerson (yelling commands at Claude.AI)
 */

#include <Bluepad32.h>
#include <btstack.h>

// =========================================================== configuration

// Hub BLE addresses, lower case. Find them with the scanner in the two-board
// repo, or with any BLE app on your phone - do not guess.
static const char *HUB_ADDR_STR[2] = {
    "90:84:2b:61:e6:8c",   // hub 0 - tracks
    "90:84:2b:61:f2:d7",   // hub 1 - upper body
};

// LEGO hubs use a public address (90:84:2B is LEGO's OUI). If the connect
// never completes, try BD_ADDR_TYPE_LE_RANDOM here.
#define HUB_ADDR_TYPE BD_ADDR_TYPE_LE_PUBLIC

static const uint8_t PORT_A = 0x00;
static const uint8_t PORT_B = 0x01;
static const uint8_t PORT_LED = 0x32;

static const int DEADZONE  = 40;    // raw stick counts, Bluepad32 range is +/-512
static const int TRACK_MAX = 100;   // LWP3 power range is -100..100
static const int HEAD_MAX  = 60;

static const uint32_t TICK_MS            = 25;   // BTstack timer period
static const uint32_t MOTOR_MIN_GAP_MS   = 60;   // per-port command throttle
static const uint32_t RECONNECT_GAP_MS   = 3000;

static const int STATUS_LED_PIN = 2;

// LWP3 UUIDs, big-endian byte order as BTstack expects.
static const uint8_t LWP3_SERVICE_UUID[16] = {
    0x00, 0x00, 0x16, 0x23, 0x12, 0x12, 0xef, 0xde,
    0x16, 0x23, 0x78, 0x5f, 0xea, 0xbc, 0xd1, 0x23};
static const uint8_t LWP3_CHAR_UUID[16] = {
    0x00, 0x00, 0x16, 0x24, 0x12, 0x12, 0xef, 0xde,
    0x16, 0x23, 0x78, 0x5f, 0xea, 0xbc, 0xd1, 0x23};

// ============================================== shared between the 2 tasks

// Written by loop() (Arduino task), read by the BTstack timer. 32-bit aligned
// int stores on the ESP32 are single instructions, so a torn read is not
// possible; the worst case is one tick of stale data, which we do not care
// about at 40 Hz.
struct DesiredState {
    volatile int leftTrack;
    volatile int rightTrack;
    volatile int head;
};
static DesiredState gDesired = {0, 0, 0};

static volatile bool gHubsReady = false;

// ============================================================ hub plumbing

enum HubState {
    HUB_IDLE,
    HUB_CONNECTING,
    HUB_W4_SERVICE,
    HUB_W4_CHARACTERISTIC,
    HUB_READY,
};

struct Hub {
    bd_addr_t addr;
    HubState state;
    hci_con_handle_t conHandle;
    gatt_client_service_t service;
    uint16_t valueHandle;
    uint32_t retryAt;
};

static Hub gHubs[2];
static int gActive = -1;          // hub currently mid-discovery, -1 if none

struct PortThrottle {
    int lastPower;
    uint32_t lastSentAt;
};
static PortThrottle gThrottle[3] = {{999, 0}, {999, 0}, {999, 0}};

static btstack_packet_callback_registration_t gHciRegistration;
static btstack_context_callback_registration_t gBootstrapRegistration;
static btstack_timer_source_t gLegoTimer;

// ============================================================== gamepad io

ControllerPtr myControllers[BP32_MAX_CONTROLLERS];
static bool gDiscoveryEnabled = false;

void onConnectedController(ControllerPtr ctl) {
    for (int i = 0; i < BP32_MAX_CONTROLLERS; i++) {
        if (myControllers[i] == nullptr) {
            myControllers[i] = ctl;
            return;
        }
    }
}

void onDisconnectedController(ControllerPtr ctl) {
    for (int i = 0; i < BP32_MAX_CONTROLLERS; i++) {
        if (myControllers[i] == ctl) {
            myControllers[i] = nullptr;
            return;
        }
    }
}

// Deadzone, then rescale so the remaining travel still reaches full power.
static int stickToPower(int raw, int maxPower) {
    if (raw > -DEADZONE && raw < DEADZONE) return 0;
    int sign = (raw < 0) ? -1 : 1;
    long mag = labs((long)raw) - DEADZONE;
    long scaled = (mag * maxPower) / (512L - DEADZONE);
    if (scaled > maxPower) scaled = maxPower;
    return sign * (int)scaled;
}

// ======================================= LWP3 - all of this on BTstack task

// Port Output Command / WriteDirectModeData:
//   08 00 81 <port> 11 51 00 <power>
//   len, hubID, msgType, port, startup+completion, subcmd, mode, payload
static void lwp3SendPower(Hub &h, uint8_t port, int8_t power) {
    if (h.state != HUB_READY) return;
    uint8_t msg[8] = {0x08, 0x00, 0x81, port, 0x11, 0x51, 0x00, (uint8_t)power};
    gatt_client_write_value_of_characteristic_without_response(
        h.conHandle, h.valueHandle, sizeof(msg), msg);
}

static void lwp3SetLed(Hub &h, uint8_t colour) {
    if (h.state != HUB_READY) return;
    uint8_t msg[8] = {0x08, 0x00, 0x81, PORT_LED, 0x11, 0x51, 0x00, colour};
    gatt_client_write_value_of_characteristic_without_response(
        h.conHandle, h.valueHandle, sizeof(msg), msg);
}

static void driveMotor(Hub &h, uint8_t port, int power, PortThrottle &t) {
    if (h.state != HUB_READY) return;

    uint32_t now = btstack_run_loop_get_time_ms();
    bool stopping = (power == 0 && t.lastPower != 0);
    if (!stopping) {
        if (power == t.lastPower) return;
        if ((now - t.lastSentAt) < MOTOR_MIN_GAP_MS) return;
    }

    lwp3SendPower(h, port, (int8_t)power);
    t.lastPower = power;
    t.lastSentAt = now;
}

static void gattPacketHandler(uint8_t packet_type, uint16_t channel,
                              uint8_t *packet, uint16_t size) {
    if (gActive < 0) return;
    Hub &h = gHubs[gActive];
    gatt_client_characteristic_t ch;

    switch (hci_event_packet_get_type(packet)) {
        case GATT_EVENT_SERVICE_QUERY_RESULT:
            gatt_event_service_query_result_get_service(packet, &h.service);
            break;

        case GATT_EVENT_CHARACTERISTIC_QUERY_RESULT:
            gatt_event_characteristic_query_result_get_characteristic(packet, &ch);
            h.valueHandle = ch.value_handle;
            break;

        case GATT_EVENT_QUERY_COMPLETE:
            if (h.state == HUB_W4_SERVICE) {
                if (h.service.start_group_handle == 0) {
                    // Not a LEGO hub, or it never answered.
                    gap_disconnect(h.conHandle);
                    break;
                }
                h.state = HUB_W4_CHARACTERISTIC;
                gatt_client_discover_characteristics_for_service_by_uuid128(
                    &gattPacketHandler, h.conHandle, &h.service, LWP3_CHAR_UUID);
            } else if (h.state == HUB_W4_CHARACTERISTIC) {
                if (h.valueHandle == 0) {
                    gap_disconnect(h.conHandle);
                    break;
                }
                h.state = HUB_READY;
                gActive = -1;
                lwp3SetLed(h, 0x06);   // green
            }
            break;

        default:
            break;
    }
}

static void onLeConnected(hci_con_handle_t handle) {
    if (gActive < 0) return;
    Hub &h = gHubs[gActive];
    if (h.state != HUB_CONNECTING) return;   // not ours - probably a BLE gamepad

    h.conHandle = handle;
    h.state = HUB_W4_SERVICE;
    memset(&h.service, 0, sizeof(h.service));
    h.valueHandle = 0;
    gatt_client_discover_primary_services_by_uuid128(
        &gattPacketHandler, handle, LWP3_SERVICE_UUID);
}

static void onDisconnected(hci_con_handle_t handle) {
    for (int i = 0; i < 2; i++) {
        if (gHubs[i].state == HUB_IDLE) continue;
        if (gHubs[i].conHandle != handle) continue;

        gHubs[i].state = HUB_IDLE;
        gHubs[i].conHandle = HCI_CON_HANDLE_INVALID;
        gHubs[i].valueHandle = 0;
        gHubs[i].retryAt = btstack_run_loop_get_time_ms() + RECONNECT_GAP_MS;
        gHubsReady = false;
        if (gActive == i) gActive = -1;
        for (int p = 0; p < 3; p++) gThrottle[p].lastPower = 999;
    }
}

static void hciPacketHandler(uint8_t packet_type, uint16_t channel,
                             uint8_t *packet, uint16_t size) {
    if (packet_type != HCI_EVENT_PACKET) return;

    switch (hci_event_packet_get_type(packet)) {
#ifdef HCI_EVENT_META_GAP
        case HCI_EVENT_META_GAP:
            if (hci_event_gap_meta_get_subevent_code(packet) !=
                GAP_SUBEVENT_LE_CONNECTION_COMPLETE)
                break;
            onLeConnected(
                gap_subevent_le_connection_complete_get_connection_handle(packet));
            break;
#endif
        case HCI_EVENT_LE_META:
            if (hci_event_le_meta_get_subevent_code(packet) !=
                HCI_SUBEVENT_LE_CONNECTION_COMPLETE)
                break;
            onLeConnected(
                hci_subevent_le_connection_complete_get_connection_handle(packet));
            break;

        case HCI_EVENT_DISCONNECTION_COMPLETE:
            onDisconnected(
                hci_event_disconnection_complete_get_connection_handle(packet));
            break;

        default:
            break;
    }
}

// One hub at a time. The controller only allows a single outstanding LE
// create-connection, and doing them in sequence keeps this simple.
static void serviceHubConnections() {
    if (gActive >= 0) return;

    uint32_t now = btstack_run_loop_get_time_ms();
    for (int i = 0; i < 2; i++) {
        if (gHubs[i].state != HUB_IDLE) continue;
        if (now < gHubs[i].retryAt) continue;

        gActive = i;
        gHubs[i].state = HUB_CONNECTING;
        gHubs[i].retryAt = now + RECONNECT_GAP_MS;
        gap_connect(gHubs[i].addr, HUB_ADDR_TYPE);
        return;
    }
}

static void legoTick() {
    serviceHubConnections();

    // A connect attempt that never completes leaves us stuck on gActive.
    if (gActive >= 0 && gHubs[gActive].state == HUB_CONNECTING &&
        btstack_run_loop_get_time_ms() > gHubs[gActive].retryAt) {
        gap_connect_cancel();
        gHubs[gActive].state = HUB_IDLE;
        gHubs[gActive].retryAt = btstack_run_loop_get_time_ms() + RECONNECT_GAP_MS;
        gActive = -1;
        return;
    }

    gHubsReady = (gHubs[0].state == HUB_READY && gHubs[1].state == HUB_READY);

    driveMotor(gHubs[0], PORT_A, gDesired.leftTrack,  gThrottle[0]);
    driveMotor(gHubs[0], PORT_B, gDesired.rightTrack, gThrottle[1]);
    driveMotor(gHubs[1], PORT_A, gDesired.head,       gThrottle[2]);
}

static void legoTickHandler(btstack_timer_source_t *ts) {
    legoTick();
    btstack_run_loop_set_timer(ts, TICK_MS);
    btstack_run_loop_add_timer(ts);
}

// Runs once, on the BTstack thread, scheduled from setup().
static void legoBootstrap(void *context) {
    (void)context;

    gatt_client_init();

    gHciRegistration.callback = &hciPacketHandler;
    hci_add_event_handler(&gHciRegistration);

    gLegoTimer.process = &legoTickHandler;
    btstack_run_loop_set_timer(&gLegoTimer, TICK_MS);
    btstack_run_loop_add_timer(&gLegoTimer);
}

// =================================================================== setup

void setup() {
    Serial.begin(115200);
    pinMode(STATUS_LED_PIN, OUTPUT);
    digitalWrite(STATUS_LED_PIN, LOW);

    for (int i = 0; i < 2; i++) {
        sscanf_bd_addr(HUB_ADDR_STR[i], gHubs[i].addr);
        gHubs[i].state = HUB_IDLE;
        gHubs[i].conHandle = HCI_CON_HANDLE_INVALID;
        gHubs[i].valueHandle = 0;
        gHubs[i].retryAt = 0;
    }

    BP32.setup(&onConnectedController, &onDisconnectedController);
    BP32.enableVirtualDevice(false);

    // Hubs first. Gamepad discovery gets switched on once they are up.
    BP32.enableNewBluetoothConnections(false);

    gBootstrapRegistration.callback = &legoBootstrap;
    gBootstrapRegistration.context = NULL;
    btstack_run_loop_execute_on_main_thread(&gBootstrapRegistration);

    Serial.println("Connecting hubs, then opening for the gamepad");
}

void loop() {
    BP32.update();

    if (gHubsReady && !gDiscoveryEnabled) {
        BP32.enableNewBluetoothConnections(true);
        gDiscoveryEnabled = true;
        Serial.println("Hubs up - put the PS4 pad in pairing mode (SHARE + PS)");
    }

    ControllerPtr gp = nullptr;
    for (int i = 0; i < BP32_MAX_CONTROLLERS; i++) {
        if (myControllers[i] && myControllers[i]->isConnected() &&
            myControllers[i]->isGamepad()) {
            gp = myControllers[i];
            break;
        }
    }

    digitalWrite(STATUS_LED_PIN, (gp && gHubsReady) ? HIGH : LOW);

    if (gp == nullptr) {
        gDesired.leftTrack = 0;
        gDesired.rightTrack = 0;
        gDesired.head = 0;
    } else {
        gDesired.leftTrack  = stickToPower(-gp->axisY(),  TRACK_MAX);
        gDesired.rightTrack = stickToPower(-gp->axisRY(), TRACK_MAX);
        gDesired.head       = stickToPower(gp->axisX(),   HEAD_MAX);
    }

    vTaskDelay(1);
}