// MUTEX EXAMPLE 2024-2025
// DEVELOPED for RTS @ UCF  BY MIKE BOROWCZAK
// PASSED INTO CHATGPT  5 OCT 2025 FOR CLEANUP/COMMENTS and
// to slow down timing so students can visually see task transitions.

#include <stdio.h>
#include <inttypes.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "esp_timer.h"

static SemaphoreHandle_t xMutex = NULL;
static volatile int shared_counter = 0;   // Shared resource
static volatile int current_holder = 0;   // 0 = none, 1 = Task1, 2 = Task2

// -----------------------------------------------------------------------------
// Utility: print current status every second (slower for visibility)
// -----------------------------------------------------------------------------
static void print_task(void *pvParameters)
{
    (void) pvParameters;
    while (1) {
        int64_t time_ms = esp_timer_get_time() / 1000;
        printf("[Monitor] Time=%" PRId64 " ms | Holder=%d | Counter=%d\n",
               time_ms, current_holder, shared_counter);
        vTaskDelay(pdMS_TO_TICKS(1000));  // print once per second
    }
}

// -----------------------------------------------------------------------------
// Task 1: periodically enters the critical section and increments the counter
// -----------------------------------------------------------------------------
static void Task1(void *pvParameters)
{
    (void) pvParameters;
    while (1) {
        // Wait before attempting to acquire mutex
        vTaskDelay(pdMS_TO_TICKS(2000));  // 3 seconds idle

        // Acquire mutex (blocks indefinitely if taken)
        if (xSemaphoreTake(xMutex, portMAX_DELAY) == pdTRUE) {
            current_holder = 1;
            printf("Task1: >>> ENTERING critical section <<<\n");

            // Simulated slow work: increment shared resource
            for (int i = 0; i < 3; i++) {
                shared_counter++;
                printf("Task1: working... counter=%d\n", shared_counter);
                vTaskDelay(pdMS_TO_TICKS(1500)); // 1.5 seconds per step
            }

            printf("Task1: <<< LEAVING critical section >>>\n");
            current_holder = 1;
            xSemaphoreGive(xMutex); // Release mutex
        }
    }
}

// -----------------------------------------------------------------------------
// Task 2: also wants to access shared_counter (decrements)
// -----------------------------------------------------------------------------
static void Task2(void *pvParameters)
{
    (void) pvParameters;
    while (1) {
        // Wait before attempting to acquire mutex
        vTaskDelay(pdMS_TO_TICKS(2000));  // 2 seconds idle

        if (xSemaphoreTake(xMutex, portMAX_DELAY) == pdTRUE) {
            current_holder = 2;
            printf("Task2: >>> ENTERING critical section <<<\n");

            // Simulated slow work: decrement shared resource
            for (int i = 0; i < 3; i++) {
                shared_counter--;
                printf("Task2: working... counter=%d\n", shared_counter);
                vTaskDelay(pdMS_TO_TICKS(2000)); // 2 seconds per step
            }

            printf("Task2: <<< LEAVING critical section >>>\n");
            current_holder = 0;
            xSemaphoreGive(xMutex);
        }
    }
}

// -----------------------------------------------------------------------------
// Entry point
// -----------------------------------------------------------------------------
void app_main(void)
{
    // Create mutex
    xMutex = xSemaphoreCreateMutex();
    if (xMutex == NULL) {
        printf("Failed to create mutex!\n");
        return;
    }
    printf("Mutex created successfully\n");


    // Launch monitor and tasks
    // Monitor prints slowly so students can track ownership clearly.
    xTaskCreate(print_task, "PrintTask", 2048, NULL, 1, NULL);

    // Both tasks same priority to show natural alternation through mutex handoff

    xTaskCreate(Task1, "Task1", 2048, NULL, 2, NULL);
    xTaskCreate(Task2, "Task2", 2048, NULL, 2, NULL);


}