#include <u.h>
#include <libc.h>

const char*  registers[] = {
	"GSR", // ro; bits give status of ports
	"OCR", // rw; bits control status of output ports; read returns last command
	"PIR", // rw; inverts polarity of input ports 
	"GCR", // rw; 0 -> output, 1 -> input; is 0xFF after boot
	"PUR", // rw; enables internal pull-up resistors; 0xFF after boot -> XRA1200P
	"IER", // rw; enables input interrupt
	"TSCR",// rw; enables three-state mode for output
	"ISR", // ro; status of input interrupts
	"REIR",// rw; enables rising edge interrupt
	"FEIR",// rw; enables falling edge interrupt
	"IFR"  // rw; time-filter for input pulses; transition 1075-225ns
};
enum _registers {
	GSR, OCR, PIR, GCR, PUR, IER, TSCR, ISR, REIR, FEIR, IFR
};
enum _ports {
	P1   = 1 << 0,,
	P2   = 1 << 1,
	P3   = 1 << 2,
	P4   = 1 << 3,
	LED  = 1 << 4,
	HUB  = 1 << 5,
	ALERT= 1 << 6,
	WP   = 1 << 7
};
uchar cmd[8];
uchar reg[1];
uchar res[8];

int
opendata(void)
{
	if (access("/dev/i2c1/i2c.20.data", 0) != 0){
		if (bind("#J20", "/dev", MBEFORE) < 0){
			sysfatal("Cannot detect ClusterHat");
		}
	}
	int fd = open("/dev/i2c1/i2c.20.data", ORDWR);
	if (fd < 0){
		sysfatal("cannot open i2c.20.data file");
	}
	return fd;
}

uchar
readreg(int data, uchar reg)
{
	cmd[0] = reg;
	pwrite(data, cmd, 1, 0);
	pread(data, res, 1, 0);
	return res[0];
}

void
sendcmd(int data, uchar c, uchar v)
{
	cmd[0] = c;
	cmd[1] = v;
	pwrite(data, cmd, 2, 0);
}

void
setuphat(int data)
{
	uchar gcr = readreg(data, GCR);
	int wp_link = 0;
	if(gcr == 0xFF) {
		// first boot setup
		uchar ocr = readreg(data, OCR);

		// detect if EEPROM WP is being pulled high
		uchar pur = readreg(data, PUR);
		if(pur == 0xFF) {
			sendcmd(data, PUR, 0x7F);
			uchar gsr = readreg(data, GSR);
			wp_link = gsr >> 7;
			if(wp_link == 1){
				sendcmd(data, PUR, 0xFF);
			} else {
				sendcmd(data, GCR, 0x7F);
			}
		} else {
			sendcmd(data, GCR, 0x7F);
			wp_link = -1;
		}

		// Power On State for Pi ports p1-p4
		uchar gsr = readreg(data, GSR);
		if ( gsr & 0xF == 0xF) {
			// POS set power ON
			ocr |= 0x0F;
		} else {
			// POS set power OFF
			ocr &= 0xF0;
		}

		// default state for other pins
		ocr &= 0xFF - ALERT;
		ocr |= LED;
		ocr &= 0xFF - HUB;
		sendcmd(data, OCR, ocr);
		
		// set pins to output
		sendcmd(data, GCR, 0);
	} else {
		uchar gsr = readreg(data, GSR);
		wp_link = gsr >> 7;
	}
}

void
printstatus(int data)
{
	for(uchar i=0; i<0x0a; ++i){
		uchar val = readreg(data, i);
		print("%4s: 0x%02X\n", registers[i], val);
	}
}

void
setport(int data, uchar port, int v)
{
	uchar ocr = readreg(data, OCR);
	if (v) {
		sendcmd(data, OCR, ocr | port);
	} else {
		sendcmd(data, OCR, ocr & (0xFF - port));
	}
}

void main(int argc, char *argv[])
{
	int data = opendata();
	setuphat(data);

	if (argc == 3) {
		const char *c = argv[1];
		int v = atoi(argv[2]);
		if ((v != 1) && (v != 0)) {
			print("\"%s\" is not a valid value (0, 1)\n", argv[2]);
			exits(0);
		}
		uchar ocr = readreg(data, OCR);
		if (strcmp(c, "led") == 0) {
			setport(data, LED, v);
		} else if(strcmp(c, "p1") == 0) {
			setport(data, P1, v);
		} else if(strcmp(c, "p2") == 0) {
			setport(data, P2, v);
		} else if(strcmp(c, "p3") == 0) {
			setport(data, P3, v);
		} else if(strcmp(c, "p4") == 0) {
			setport(data, P4, v);
		} else if(strcmp(c, "hub") == 0) {
			setport(data, HUB, v);
		} else if(strcmp(c, "alert") == 0) {
			setport(data, ALERT, v);
		} else {
			print("\"%s\" is not a known command\n", c);
			exits(0);
		}
	} else {
		// TODO: print help
	}

	printstatus(data);
	close(data);
}