// SPDX-License-Identifier: GPL-2.0-only
/*
 * NII Core Surface Driver - Mathematically Defendable NII Core Driver
 *
 * Copyright (c) 2026 Sovereign Research Stack
 *
 * This driver implements the NII core surface driver based on first principles
 * from Canonical Core v1 architecture:
 * - Layer 6: Steady-State Stability (SSS) monitoring
 * - Layer 7: Alcubierre Information Metric for warp-speed compression
 * - FAMM-aware scheduling based on frustration timing
 * - Topological state management with N-local adaptation
 * - Q16.16 fixed-point arithmetic for hardware-native computation
 *
 * Based on Linux kernel drivers/fpga/ice40-spi.c by Joel Holdsworth
 */

#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/gpio/consumer.h>
#include <linux/fpga/fpga-mgr.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

// ═══════════════════════════════════════════════════════════════════════════
// Q16.16 Fixed-Point Arithmetic
// ═══════════════════════════════════════════════════════════════════════════

typedef int32_t q16_16_t;

#define Q16_16_ONE ((q16_16_t)(1 << 16))
#define Q16_16_ZERO ((q16_16_t)0)
#define Q16_16_FROM_FLOAT(f) ((q16_16_t)((f) * (1 << 16)))
#define Q16_16_TO_FLOAT(q) ((float)(q) / (1 << 16))

static inline q16_16_t q16_16_add(q16_16_t a, q16_16_t b)
{
    return a + b;
}

static inline q16_16_t q16_16_sub(q16_16_t a, q16_16_t b)
{
    return a - b;
}

static inline q16_16_t q16_16_mul(q16_16_t a, q16_16_t b)
{
    return (q16_16_t)(((int64_t)a * (int64_t)b) >> 16);
}

static inline q16_16_t q16_16_div(q16_16_t a, q16_16_t b)
{
    return (q16_16_t)(((int64_t)a << 16) / b);
}

static inline int q16_16_compare(q16_16_t a, q16_16_t b)
{
    if (a < b) return -1;
    if (a > b) return 1;
    return 0;
}

// ═══════════════════════════════════════════════════════════════════════════
// Steady-State Stability (SSS) - Layer 6
// ═══════════════════════════════════════════════════════════════════════════

struct sss_constant {
    q16_16_t routing_load;      // L_R: routing load (counter-torque)
    q16_16_t memory_load;       // L_M: memory load (counter-torque)
    q16_16_t extraneous_weight; // λ_E: extraneous load weight
    q16_16_t engram_length;     // ℓ: characteristic engram neighborhood length
    q16_16_t extraneous_gradient; // ‖∇L_E‖: gradient magnitude
};

struct slip_condition {
    q16_16_t sss_constant;
    q16_16_t heel_dig_limit;   // σ_sys: slip threshold
};

static q16_16_t compute_sss(const struct sss_constant *c)
{
    q16_16_t counter_torque = q16_16_add(c->routing_load, c->memory_load);
    q16_16_t torsional_term = q16_16_mul(
        q16_16_mul(c->extraneous_weight, c->engram_length),
        c->extraneous_gradient
    );
    return q16_16_sub(counter_torque, torsional_term);
}

static bool is_slip_threshold_crossed(const struct slip_condition *c)
{
    return q16_16_compare(c->sss_constant, -c->heel_dig_limit) < 0;
}

// ═══════════════════════════════════════════════════════════════════════════
// Alcubierre Information Metric - Layer 7
// ═══════════════════════════════════════════════════════════════════════════

struct warp_function {
    q16_16_t kappa;            // Steepness parameter
    q16_16_t sss_constant;
    q16_16_t opcode_efficacy;  // Ω_opcode
};

// Simplified sigmoid approximation for Q16.16
static q16_16_t sigmoid_q16_16(q16_16_t x)
{
    // Use piecewise linear approximation for simplicity
    // In production, use polynomial approximation or lookup table
    if (x < Q16_16_FROM_FLOAT(-5.0f))
        return Q16_16_ZERO;
    if (x > Q16_16_FROM_FLOAT(5.0f))
        return Q16_16_ONE;
    return q16_16_div(
        q16_16_add(x, Q16_16_FROM_FLOAT(5.0f)),
        Q16_16_FROM_FLOAT(10.0f)
    );
}

static q16_16_t compute_warp(const struct warp_function *w)
{
    q16_16_t exponent = q16_16_mul(-w->kappa, w->sss_constant);
    q16_16_t sigmoid = sigmoid_q16_16(exponent);
    return q16_16_mul(sigmoid, w->opcode_efficacy);
}

struct effective_velocity {
    q16_16_t local_velocity;
    q16_16_t coherence;        // φ: phase coherence angle
};

static q16_16_t compute_effective_velocity(const struct effective_velocity *v)
{
    q16_16_t denominator = q16_16_sub(Q16_16_ONE, v->coherence);
    if (denominator <= Q16_16_ZERO)
        return v->local_velocity;  // Avoid division by zero
    return q16_16_div(v->local_velocity, denominator);
}

struct warp_metric {
    q16_16_t proper_time;       // dτ
    q16_16_t entropy_displacement; // dH
    q16_16_t effective_velocity;
    q16_16_t warp_coupling;     // f · Ω
};

static q16_16_t compute_warp_metric(const struct warp_metric *m)
{
    q16_16_t time_term = q16_16_mul(-m->proper_time, m->proper_time);
    q16_16_t space_term = q16_16_sub(
        m->entropy_displacement,
        q16_16_mul(
            q16_16_mul(m->effective_velocity, m->warp_coupling),
            m->proper_time
        )
    );
    return q16_16_add(time_term, q16_16_mul(space_term, space_term));
}

// ═══════════════════════════════════════════════════════════════════════════
// FAMM-Aware Scheduling
// ═══════════════════════════════════════════════════════════════════════════

struct famm_timing {
    q16_16_t torsional_stress;   // Σ²
    q16_16_t interlocking_energy; // I_lock
    q16_16_t laplacian_energy;   // Δϕ
};

enum schedule_decision {
    SCHEDULE_EXECUTE,
    SCHEDULE_DEFER,
    SCHEDULE_THROTTLE,
};

static q16_16_t compute_famm_load(const struct famm_timing *t)
{
    return q16_16_add(
        q16_16_add(t->torsional_stress, t->interlocking_energy),
        t->laplacian_energy
    );
}

static enum schedule_decision make_schedule_decision(q16_16_t load)
{
    if (load < Q16_16_FROM_FLOAT(0.25f))
        return SCHEDULE_EXECUTE;
    else if (load < Q16_16_FROM_FLOAT(0.5f))
        return SCHEDULE_THROTTLE;
    else
        return SCHEDULE_DEFER;
}

// ═══════════════════════════════════════════════════════════════════════════
// Topological State Management
// ═══════════════════════════════════════════════════════════════════════════

struct topological_state {
    q16_16_t cognitive_load;
    const char *topology_metric;  // "relational", "semantic", "topological", "minimal"
    q16_16_t coherence;
};

static const char *adapt_topology(q16_16_t cognitive_load)
{
    if (cognitive_load < Q16_16_FROM_FLOAT(0.25f))
        return "relational";
    else if (cognitive_load < Q16_16_FROM_FLOAT(0.5f))
        return "semantic";
    else if (cognitive_load < Q16_16_FROM_FLOAT(0.75f))
        return "topological";
    else
        return "minimal";
}

// ═══════════════════════════════════════════════════════════════════════════
// NII Core Surface Driver State
// ═══════════════════════════════════════════════════════════════════════════

enum nii_core_id {
    NII_CORE_SEMANTIC,
    NII_CORE_TRANSLATION,
    NII_CORE_VERIFICATION,
};

enum core_status {
    CORE_STATUS_IDLE,
    CORE_STATUS_PROCESSING,
    CORE_STATUS_COMPLETE,
    CORE_STATUS_ERROR,
};

struct nii_surface_driver_state {
    enum nii_core_id core_id;
    struct sss_constant sss_constant;
    struct slip_condition slip_condition;
    struct warp_function warp_function;
    struct famm_timing famm_timing;
    struct topological_state topological_state;
    enum core_status current_status;
    
    // Hardware resources
    struct spi_device *spi;
    struct gpio_desc *reset;
    struct gpio_desc *cdone;
    
    // Work queue for async operations
    struct workqueue_struct *workqueue;
    struct work_struct work;
};

// ═══════════════════════════════════════════════════════════════════════════
// Driver Initialization
// ═══════════════════════════════════════════════════════════════════════════

static void init_nii_driver_state(struct nii_surface_driver_state *state,
                                   enum nii_core_id core_id)
{
    state->core_id = core_id;
    
    // Initialize SSS constant
    state->sss_constant.routing_load = Q16_16_FROM_FLOAT(1.0f);
    state->sss_constant.memory_load = Q16_16_FROM_FLOAT(0.8f);
    state->sss_constant.extraneous_weight = Q16_16_FROM_FLOAT(0.5f);
    state->sss_constant.engram_length = Q16_16_FROM_FLOAT(4.0f);
    state->sss_constant.extraneous_gradient = Q16_16_FROM_FLOAT(0.1f);
    
    // Initialize slip condition
    state->slip_condition.sss_constant = compute_sss(&state->sss_constant);
    state->slip_condition.heel_dig_limit = Q16_16_FROM_FLOAT(0.5f);
    
    // Initialize warp function
    state->warp_function.kappa = Q16_16_FROM_FLOAT(1.0f);
    state->warp_function.sss_constant = state->slip_condition.sss_constant;
    state->warp_function.opcode_efficacy = Q16_16_ONE;
    
    // Initialize FAMM timing
    state->famm_timing.torsional_stress = Q16_16_FROM_FLOAT(1.0f);
    state->famm_timing.interlocking_energy = Q16_16_FROM_FLOAT(0.5f);
    state->famm_timing.laplacian_energy = Q16_16_FROM_FLOAT(0.3f);
    
    // Initialize topological state
    state->topological_state.cognitive_load = Q16_16_ZERO;
    state->topological_state.topology_metric = "relational";
    state->topological_state.coherence = Q16_16_ONE;
    
    state->current_status = CORE_STATUS_IDLE;
}

// ═══════════════════════════════════════════════════════════════════════════
// SSS Monitoring Loop (Work Queue)
// ═══════════════════════════════════════════════════════════════════════════

static void sss_monitor_work(struct work_struct *work)
{
    struct nii_surface_driver_state *state = container_of(work,
        struct nii_surface_driver_state, work);
    
    // Update SSS constant
    state->slip_condition.sss_constant = compute_sss(&state->sss_constant);
    
    // Check slip threshold
    if (is_slip_threshold_crossed(&state->slip_condition)) {
        dev_err(&state->spi->dev, "Slip threshold crossed - MODE_SURVIVAL\n");
        state->current_status = CORE_STATUS_ERROR;
        // Trigger MODE_SURVIVAL: VRAM_FLUSH
        gpiod_set_value(state->reset, 1);
        udelay(1000);  // 1ms reset
        gpiod_set_value(state->reset, 0);
    }
    
    // Update warp function
    state->warp_function.sss_constant = state->slip_condition.sss_constant;
    
    // Update topological state
    state->topological_state.topology_metric = 
        adapt_topology(state->topological_state.cognitive_load);
}

// ═══════════════════════════════════════════════════════════════════════════
// FPGA Manager Operations
// ═══════════════════════════════════════════════════════════════════════════

static enum fpga_mgr_states nii_fpga_ops_state(struct fpga_manager *mgr)
{
    struct nii_surface_driver_state *state = mgr->priv;
    
    return gpiod_get_value(state->cdone) ? FPGA_MGR_STATE_OPERATING :
                                             FPGA_MGR_STATE_UNKNOWN;
}

static int nii_fpga_ops_write_init(struct fpga_manager *mgr,
                                    struct fpga_image_info *info,
                                    const char *buf, size_t count)
{
    struct nii_surface_driver_state *state = mgr->priv;
    struct spi_device *spi = state->spi;
    struct spi_message message;
    struct spi_transfer assert_cs_then_reset_delay = {
        .cs_change = 1,
        .delay = {
            .value = 1,  // 1us delay
            .unit = SPI_DELAY_UNIT_USECS
        }
    };
    struct spi_transfer housekeeping_delay_then_release_cs = {
        .delay = {
            .value = 10,  // 10us housekeeping
            .unit = SPI_DELAY_UNIT_USECS
        }
    };
    int ret;
    
    if ((info->flags & FPGA_MGR_PARTIAL_RECONFIG)) {
        dev_err(&spi->dev, "Partial reconfiguration is not supported\n");
        return -ENOTSUPP;
    }
    
    // Lock the bus, assert CRESET_B and SS_B
    spi_bus_lock(spi->controller);
    
    gpiod_set_value(state->reset, 1);
    
    spi_message_init(&message);
    spi_message_add_tail(&assert_cs_then_reset_delay, &message);
    ret = spi_sync_locked(spi, &message);
    
    // Come out of reset
    gpiod_set_value(state->reset, 0);
    
    if (ret)
        goto fail;
    
    // Check CDONE is de-asserted
    if (gpiod_get_value(state->cdone)) {
        dev_err(&spi->dev, "Device reset failed, CDONE is asserted\n");
        ret = -EIO;
        goto fail;
    }
    
    // Wait for housekeeping
    spi_message_init(&message);
    spi_message_add_tail(&housekeeping_delay_then_release_cs, &message);
    ret = spi_sync_locked(spi, &message);
    
fail:
    spi_bus_unlock(spi->controller);
    
    return ret;
}

static int nii_fpga_ops_write(struct fpga_manager *mgr,
                               const char *buf, size_t count)
{
    struct nii_surface_driver_state *state = mgr->priv;
    return spi_write(state->spi, buf, count);
}

static int nii_fpga_ops_write_complete(struct fpga_manager *mgr,
                                        struct fpga_image_info *info)
{
    struct nii_surface_driver_state *state = mgr->priv;
    struct spi_device *spi = state->spi;
    const u8 padding[7] = {0};  // 49 bits = 7 bytes
    
    // Check CDONE is asserted
    if (!gpiod_get_value(state->cdone)) {
        dev_err(&spi->dev, "CDONE was not asserted after firmware transfer\n");
        return -EIO;
    }
    
    // Send zero-padding to activate firmware
    return spi_write(spi, padding, sizeof(padding));
}

static const struct fpga_manager_ops nii_fpga_ops = {
    .state = nii_fpga_ops_state,
    .write_init = nii_fpga_ops_write_init,
    .write = nii_fpga_ops_write,
    .write_complete = nii_fpga_ops_write_complete,
};

// ═══════════════════════════════════════════════════════════════════════════
// Probe Function
// ═══════════════════════════════════════════════════════════════════════════

static int nii_surface_driver_probe(struct spi_device *spi)
{
    struct device *dev = &spi->dev;
    struct nii_surface_driver_state *state;
    struct fpga_manager *mgr;
    int ret;
    
    state = devm_kzalloc(dev, sizeof(*state), GFP_KERNEL);
    if (!state)
        return -ENOMEM;
    
    state->spi = spi;
    
    // Check SPI speed limits
    if (spi->max_speed_hz > 25000000) {  // 25MHz max
        dev_err(dev, "SPI speed is too high, maximum speed is 25MHz\n");
        return -EINVAL;
    }
    
    if (spi->max_speed_hz < 1000000) {  // 1MHz min
        dev_err(dev, "SPI speed is too low, minimum speed is 1MHz\n");
        return -EINVAL;
    }
    
    if (spi->mode & SPI_CPHA) {
        dev_err(dev, "Bad SPI mode, CPHA not supported\n");
        return -EINVAL;
    }
    
    // Set up GPIOs
    state->cdone = devm_gpiod_get(dev, "cdone", GPIOD_IN);
    if (IS_ERR(state->cdone)) {
        ret = PTR_ERR(state->cdone);
        dev_err(dev, "Failed to get CDONE GPIO: %d\n", ret);
        return ret;
    }
    
    state->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
    if (IS_ERR(state->reset)) {
        ret = PTR_ERR(state->reset);
        dev_err(dev, "Failed to get CRESET_B GPIO: %d\n", ret);
        return ret;
    }
    
    // Initialize driver state
    init_nii_driver_state(state, NII_CORE_SEMANTIC);
    
    // Create work queue for SSS monitoring
    state->workqueue = alloc_workqueue("nii_sss_monitor", WQ_HIGHPRI, 0);
    if (!state->workqueue) {
        dev_err(dev, "Failed to allocate workqueue\n");
        return -ENOMEM;
    }
    
    INIT_WORK(&state->work, sss_monitor_work);
    
    // Register FPGA manager
    mgr = devm_fpga_mgr_register(dev, "NII Core Surface Driver",
                                   &nii_fpga_ops, state);
    if (IS_ERR(mgr)) {
        ret = PTR_ERR(mgr);
        dev_err(dev, "Failed to register FPGA manager: %d\n", ret);
        destroy_workqueue(state->workqueue);
        return ret;
    }
    
    spi_set_drvdata(spi, state);
    
    dev_info(dev, "NII Core Surface Driver initialized\n");
    dev_info(dev, "SSS constant: %f\n", Q16_16_TO_FLOAT(state->slip_condition.sss_constant));
    dev_info(dev, "Topology: %s\n", state->topological_state.topology_metric);
    
    return 0;
}

static void nii_surface_driver_remove(struct spi_device *spi)
{
    struct nii_surface_driver_state *state = spi_get_drvdata(spi);
    
    if (state->workqueue) {
        destroy_workqueue(state->workqueue);
    }
    
    dev_info(&spi->dev, "NII Core Surface Driver removed\n");
}

// ═══════════════════════════════════════════════════════════════════════════
// Device Tree Match Table
// ═══════════════════════════════════════════════════════════════════════════

static const struct of_device_id nii_fpga_of_match[] = {
    { .compatible = "sovereign,nii-surface-driver", },
    {},
};
MODULE_DEVICE_TABLE(of, nii_fpga_of_match);

static const struct spi_device_id nii_fpga_spi_ids[] = {
    { .name = "nii-surface-driver", },
    {},
};
MODULE_DEVICE_TABLE(spi, nii_fpga_spi_ids);

static struct spi_driver nii_surface_driver = {
    .probe = nii_surface_driver_probe,
    .remove = nii_surface_driver_remove,
    .driver = {
        .name = "nii-surface-driver",
        .of_match_table = nii_fpga_of_match,
    },
    .id_table = nii_fpga_spi_ids,
};

module_spi_driver(nii_surface_driver);

MODULE_AUTHOR("Sovereign Research Stack <research@sovereign.stack>");
MODULE_DESCRIPTION("NII Core Surface Driver - Mathematically Defendable NII Core Driver");
MODULE_LICENSE("GPL v2");
MODULE_VERSION("1.0");