/**
 * @file memory_protection.c
 * @brief Memory Protection for safety-critical applications
 */

#include "kernel.h"
#include "task.h"
#include <string.h>

/* Memory Protection Configuration */
#define MPU_MAX_REGIONS          8
#define MEMORY_PROTECTION_ALIGNMENT  32  /* 32 bytes minimum */

/* Memory Region Attributes */
typedef struct {
    uint32_t base_address;
    uint32_t size;
    uint8_t permissions;
    bool executable;
    bool cacheable;
    bool bufferable;
} MemoryRegion_t;

/* Memory Protection State */
typedef struct {
    bool initialized;
    bool enabled;
    MemoryRegion_t regions[MPU_MAX_REGIONS];
    uint8_t region_count;
    TaskHandle_t current_task;
    Mutex_t mutex;
} MemoryProtectionState_t;

static MemoryProtectionState_t memory_protection;

/* Initialize Memory Protection */
KernelStatus_t memory_protection_init(void) {
    if (memory_protection.initialized) {
        return KERNEL_ERROR;
    }

    memset(&memory_protection, 0, sizeof(MemoryProtectionState_t));
    memory_protection.enabled = false;
    memory_protection.region_count = 0;

    mutex_create(&memory_protection.mutex, false);

    memory_protection.initialized = true;
    return KERNEL_OK;
}

/* Configure Memory Region */
KernelStatus_t memory_protection_configure_region(uint32_t base_address,
                                                   uint32_t size,
                                                   uint8_t permissions,
                                                   bool executable) {
    if (!memory_protection.initialized) {
        return KERNEL_ERROR;
    }

    if (memory_protection.region_count >= MPU_MAX_REGIONS) {
        return KERNEL_OUT_OF_MEMORY;
    }

    /* Validate alignment */
    if ((base_address % MEMORY_PROTECTION_ALIGNMENT) != 0 ||
        (size % MEMORY_PROTECTION_ALIGNMENT) != 0) {
        return KERNEL_INVALID_PARAMETER;
    }

    mutex_lock(&memory_protection.mutex, 100);

    MemoryRegion_t* region = &memory_protection.regions[memory_protection.region_count];
    region->base_address = base_address;
    region->size = size;
    region->permissions = permissions;
    region->executable = executable;

    memory_protection.region_count++;

    mutex_unlock(&memory_protection.mutex);

    return KERNEL_OK;
}

/* Enable Memory Protection */
KernelStatus_t memory_protection_enable(void) {
    if (!memory_protection.initialized) {
        return KERNEL_ERROR;
    }

    /* Configure MPU hardware */
    hal_mpu_enable();

    /* Configure regions */
    for (uint8_t i = 0; i < memory_protection.region_count; i++) {
        MemoryRegion_t* region = &memory_protection.regions[i];
        hal_mpu_configure_region(i, region->base_address, region->size,
                                 region->permissions, region->executable);
    }

    memory_protection.enabled = true;

    return KERNEL_OK;
}

/* Disable Memory Protection */
KernelStatus_t memory_protection_disable(void) {
    if (!memory_protection.initialized) {
        return KERNEL_ERROR;
    }

    hal_mpu_disable();
    memory_protection.enabled = false;

    return KERNEL_OK;
}

/* Set Task Memory Region */
KernelStatus_t memory_protection_set_task_region(TaskHandle_t task,
                                                  uint32_t base_address,
                                                  uint32_t size) {
    if (!memory_protection.initialized || task == NULL) {
        return KERNEL_ERROR;
    }

    /* Configure task-specific memory region */
    hal_mpu_configure_task_region(task, base_address, size);

    return KERNEL_OK;
}

/* Check Memory Access */
bool memory_protection_check_access(uint32_t address, uint8_t access_type) {
    if (!memory_protection.initialized || !memory_protection.enabled) {
        return true;  /* Protection disabled */
    }

    /* Check if address is within any protected region */
    for (uint8_t i = 0; i < memory_protection.region_count; i++) {
        MemoryRegion_t* region = &memory_protection.regions[i];

        if (address >= region->base_address &&
            address < (region->base_address + region->size)) {
            /* Check permissions */
            if ((region->permissions & access_type) == 0) {
                return false;  /* Access denied */
            }
            return true;  /* Access allowed */
        }
    }

    return false;  /* Address not in any region */
}

/* Memory Protection Fault Handler */
void memory_protection_fault_handler(uint32_t fault_address) {
    /* Log fault */
    fault_handler_process(2, fault_address, 0);

    /* Enter safe state */
    while (1) {
        /* Wait for watchdog reset */
    }
}