/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include <stdint.h> // Standard Integer Types
#include <stdio.h> // Standard IO facilities
#include <stdlib.h> // General utilities
#include <stdbool.h> // Boolean
#include <string.h> // Strings

#include <avr/io.h> // AVR device-specific IO definitions
#include <util/delay.h> // Convenience functions for busy-wait delay loops
#include <avr/interrupt.h> // Interrupts
#include <avr/wdt.h> // Watchdog timer handling
#include <avr/pgmspace.h> // Program Space Utilities
#include <avr/sleep.h> // Power Management and Sleep Modes

#include "uart.h" // basic UART functions
#include "main.h" // main definitions

/* help strings */
const char help_00[] PROGMEM = "commands:\n";
const char help_01[] PROGMEM = "\thelp                  display this help\n";
const char help_02[] PROGMEM = "\tled on|off|toggle     change LED state\n";
const char help_03[] PROGMEM = "\tread [B-D][0-7]       read value from pin\n";
const char help_04[] PROGMEM = "\twrite [B-D][0-7] 0|1  write value on pin\n";
PGM_P const help_table[] PROGMEM = {
    help_00,
    help_01,
    help_02,
    help_03,
    help_04
};

/* global variables */
char uart_in[32] = {0}; // user input from USART
volatile uint8_t uart_in_i = 0; // how many UART characters have been input

/* flags, set in the interrupts and handled in the main program */
volatile bool uart_flag = false; // UART input data is available

/* switch off LED */
void led_off(void)
{
	LED_PORT &= ~(1<<LED_IO); // remove power to LED
}

/* switch on LED */
void led_on(void)
{
	LED_PORT |= (1<<LED_IO); // provide power to LED
}

/* toggle LED */
void led_toggle(void)
{
	LED_PIN |= (1<<LED_IO);
}

void help(void)
{
	char* str;
	for (uint8_t i=0; i<sizeof(help_table)/sizeof(PGM_P); i++) { /* display all help lines */
		str = malloc(strlen_PF((uint_farptr_t)pgm_read_word(&(help_table[i]))));
		strcpy_PF(str, (uint_farptr_t)pgm_read_word(&(help_table[i])));
		printf(str);
		free(str);
	}
}

/* save the UART input into a string */
ISR(USART_RX_vect) { /* UART receive interrupt */
	uart_in[uart_in_i] = getchar(); // save input
	if (uart_in_i<sizeof(uart_in)-1) { // go to next if there is space left (else overwrite last)
		uart_in_i++; // prepare for next character
		uart_in[uart_in_i] = 0; // always end the string
	}
	uart_flag = true; // notify new character is there
}

/* disable watchdog when booting */
void wdt_init(void) __attribute__((naked)) __attribute__((section(".init3")));
void wdt_init(void)
{
	MCUSR = 0;
	wdt_disable();

	return;
}

/* initialize GPIO */
void io_init(void)
{
	/* use UART as terminal */
	uart_init();
	stdout = &uart_output;
	stdin  = &uart_input;

	/* gpio */
	/* LED */
	LED_DDR |= (1<<LED_IO); // LED is driven by pin (set as output)
	led_off();

	sei(); /* enable interrupts */
}

/* process command */
void command_action()
{
	/* split command */
	const char* delimiter = " ";
	char* word = strtok(uart_in,delimiter);
	if (!word) {
		goto error;
	}
	/* parse command */
	if (0==strcmp(word,"help")) {
		help();
	} else if (0==strcmp(word,"led")) {
		/* expecting state */
		word = strtok(NULL,delimiter);
		if (!word) {
			goto error;
		}
		if (0==strcmp(word,"on")) {
			led_on();
		} else if (0==strcmp(word,"off")) {
			led_off();
		} else if (0==strcmp(word,"toggle")) {
			led_toggle();
		} else {
			goto error;
		}
	} else if (0==strcmp(word,"read")) {
		/* expecting pin */
		word = strtok(NULL,delimiter);
		if (!word) {
			goto error;
		}
		if (2==strlen(word) && word[0]>='B' && word[0]<='D' && word[1]>='0' && word[1]<='7') {
			volatile uint8_t * pin = NULL;
			volatile uint8_t * ddr = NULL;
			switch (word[0]) {
				case 'B':
					pin = &PINB;
					ddr = &DDRB;
					break;
				case 'C':
					pin = &PINC;
					ddr = &DDRC;
					break;
				case 'D':
					pin = &PIND;
					ddr = &DDRD;
					break;
			}
			*ddr &= ~(1<<(word[1]-'0')); // set as input
			printf("%s: %u\n", word, (*pin>>(word[1]-'0'))&0x1); // print value
		} else {
			goto error;
		}
	} else if (0==strcmp(word,"write")) {
		/* expecting pin */
		word = strtok(NULL,delimiter);
		if (!word) {
			goto error;
		}
		if (2==strlen(word) && word[0]>='B' && word[0]<='D' && word[1]>='0' && word[1]<='7') {
			uint8_t pin = word[1]-'0';
			volatile uint8_t * port = NULL;
			volatile uint8_t * ddr = NULL;
			switch (word[0]) {
				case 'B':
					port = &PORTB;
					ddr = &DDRB;
					break;
				case 'C':
					port = &PORTC;
					ddr = &DDRC;
					break;
				case 'D':
					port = &PORTD;
					ddr = &DDRD;
					break;
			}
			*ddr |= (1<<pin); // set as output
			/* expecting value */
			word = strtok(NULL,delimiter);
			if (!word || strlen(word)!=1) {
				goto error;
			}
			/* write value */
			if ('0'==word[0]) {
				*port &= ~(1<<pin);
			} else if ('1'==word[0]) {
				*port |= (1<<pin);
			} else {
				goto error;
			}
		} else {
			goto error;
		}
	} else {
		goto error;
	}

	return;
error:
	printf(PSTR("command not recognized\n"));
	return;
}

int main(void)
{
	uint8_t uart_out_i = 0; // how many UART input characters have been processed

	io_init(); // initialize IOs
	
	printf(PSTR("welcome to the demo code\n"));
	while (true) { // endless loop for micro-controller
		while (uart_flag) { // new UART input
			uart_flag = false;
			while (uart_out_i<uart_in_i) {
				putchar(uart_in[uart_out_i++]); // print current character
			}
			if ('\n'==uart_in[uart_in_i-1] || '\r'==uart_in[uart_in_i-1]) { // end of line detected
				if ('\r'==uart_in[uart_in_i-1]) { // be sure to print a newline (for windows and mac EOL)
					putchar('\n');
				}
				uart_in[uart_in_i-1] = 0; // remove end of line
				if (uart_in_i>1) { // ignore empty lines
					command_action(); // process command
				}
				uart_out_i = 0; // reset output
				uart_in_i = 0; // reset input
			}
		}
		/* go to sleep and wait for next interrupt */
		set_sleep_mode(SLEEP_MODE_IDLE);
		sleep_mode();
	}
	return 0;
}