#include "stm32l0xx_hal.h"
#include <stdio.h>
#include <string.h>

UART_HandleTypeDef huart2;

void SystemClock_Config(void);
void MX_GPIO_Init(void);
void MX_USART2_UART_Init(void);
void Process_Command(char *cmd);

// Global buffers for command line processing
char rx_buffer[64];
uint8_t rx_index = 0;
uint8_t led_state = 0; // 0 = OFF, 1 = ON

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  
  MX_GPIO_Init();
  MX_USART2_UART_Init();

  char tx_buf[128];
  sprintf(tx_buf, "\r\n=== STM32 HAL UART CLI Initialized ===\r\nType 'HELP' to see available commands.\r\n\r\n> ");
  HAL_UART_Transmit(&huart2, (uint8_t*)tx_buf, strlen(tx_buf), HAL_MAX_DELAY);

  uint8_t rx_char;

  while (1)
  {
    // Receive 1 byte via polling mode (non-blocking style 10ms timeout)
    if (HAL_UART_Receive(&huart2, &rx_char, 1, 10) == HAL_OK)
    {
      // Echo the typed character back to the terminal screen
      HAL_UART_Transmit(&huart2, &rx_char, 1, HAL_MAX_DELAY);

      // Check for Carriage Return or Line Feed (Enter key)
      if (rx_char == '\r' || rx_char == '\n') 
      {
        if (rx_index > 0) 
        {
          rx_buffer[rx_index] = '\0'; // Null-terminate string
          
          // Print newline before command response
          HAL_UART_Transmit(&huart2, (uint8_t*)"\r\n", 2, HAL_MAX_DELAY);
          
          // Parse and run the input command string
          Process_Command(rx_buffer);
          
          // Reset buffer index for next command entry
          rx_index = 0;
          
          // Print command prompt line symbol
          HAL_UART_Transmit(&huart2, (uint8_t*)"> ", 2, HAL_MAX_DELAY);
        }
      }
      // Handle backspace safely
      else if (rx_char == '\b' || rx_char == 127) 
      {
        if (rx_index > 0) rx_index--;
      }
      // Collect valid characters into buffer safely
      else if (rx_index < sizeof(rx_buffer) - 1) 
      {
        rx_buffer[rx_index++] = rx_char;
      }
    }
  }
}

// Parsing function matching specified assignment requirements
void Process_Command(char *cmd)
{
  char reply[128];

  // 1. LED ON Command
  if (strcmp(cmd, "LED ON") == 0) 
  {
    HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_SET);
    led_state = 1;
    sprintf(reply, "SUCCESS: Blue LED is turned ON.\r\n");
  }
  // 2. LED OFF Command
  else if (strcmp(cmd, "LED OFF") == 0) 
  {
    HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_RESET);
    led_state = 0;
    sprintf(reply, "SUCCESS: Blue LED is turned OFF.\r\n");
  }
  // 3. STATUS Command
  else if (strcmp(cmd, "STATUS") == 0) 
  {
    if (led_state == 1) {
      sprintf(reply, "STATUS: LED state is currently [ON].\r\n");
    } else {
      sprintf(reply, "STATUS: LED state is currently [OFF].\r\n");
    }
  }
  // 4. HELP Command
  else if (strcmp(cmd, "HELP") == 0) 
  {
    sprintf(reply, "Available Commands:\r\n"
                   "  LED ON  -> Turn on the indicator LED\r\n"
                   "  LED OFF -> Turn off the indicator LED\r\n"
                   "  STATUS  -> Query current hardware state\r\n"
                   "  HELP    -> View this command list\r\n");
  }
  // Error handling for unrecognized inputs
  else 
  {
    sprintf(reply, "ERROR: Command '%s' not recognized. Type 'HELP'.\r\n", cmd);
  }

  HAL_UART_Transmit(&huart2, (uint8_t*)reply, strlen(reply), HAL_MAX_DELAY);
}

void MX_USART2_UART_Init(void)
{
  __HAL_RCC_USART2_CLK_ENABLE();

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  HAL_UART_Init(&huart2);
}

void MX_GPIO_Init(void)
{
  __HAL_RCC_GPIOA_CLK_ENABLE();
  
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  // Setup PA0 for driving the external LED output
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  // Configure PA2 (TX) and PA15 (RX) for USART2 VCP routing channel lines
  GPIO_InitStruct.Pin = GPIO_PIN_2 | GPIO_PIN_15;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

void SystemClock_Config(void) {}