#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include "mnemonics.h"

#define ERROR(prog,...) \
	do { \
		fprintf(stderr, "%s: ", prog); \
		fprintf(stderr, __VA_ARGS__); \
		fprintf(stderr, "\n"); \
	} while (0)

#define PERROR(prog,str) \
	do { \
		int err = errno; \
		fprintf(stderr, "%s: ", prog); \
		errno = err; \
		perror(str); \
	} while (0)

static const struct mnemonic *match_instruction(unsigned bits)
{
	for (int i = 0; i < MNEM_LAST; i++) {
		const struct mnemonic *m = mnemonics + i;
		if ((bits & m->mask) == m->bits) return m;
	}
	return NULL;
}

static void print_operand(FILE *out, unsigned bits, const struct operand *op)
{
	switch (op->type) {
	case REG:    fprintf(out,  "r%d",      7 & (bits >> op->shift)); break;
	case REGPTR: fprintf(out, "@r%d",      7 & (bits >> op->shift)); break;
	case IMM:    fprintf(out,   "%d", (uint8_t)(bits >> op->shift)); break;
	case PCOFF:  fprintf(out,   "%d",  (int8_t)(bits >> op->shift)); break;
	}
}

static void usage(const char *progname)
{
	printf("usage: %s [-o output] [input]\n", progname);
	printf("       %s -h\n", progname);
	printf("\n");
	printf("\t%-16s %s\n", "-h",        "display this help text and exit");
	printf("\t%-16s %s\n", "-o output", "write output to 'output' (default=stdout)");
	printf("\t%-16s %s\n", "input",     "read input from 'input' (default=stdin)");
}

int main(int argc, char **argv)
{
	const char *outname = NULL;
	int error = 0;

	extern int   optind;
	extern char *optarg;
	for (int opt; (opt = getopt(argc, argv, "+ho:")) != -1;) {
		switch (opt) {
		case 'h':
			usage(argv[0]);
			return 0;
		case 'o':
			outname = optarg;
			break;
		default:
			error = 1;
		}
	}

	if (optind < argc - 1) {
		ERROR(argv[0], "Too many input files");
		return 1;
	}
	if (error) return 1;

	FILE *in  = stdin;
	FILE *out = stdout;

	if (optind < argc && !(in = fopen(argv[optind], "r"))) {
		PERROR(argv[0], "Error opening input file");
		return 1;
	}
	if (outname && !(out = fopen(outname, "w"))) {
		PERROR(argv[0], "Error opening output file");
		fclose(in);
		return 1;
	}

	unsigned bits;
	while (fscanf(in, " %x\n", &bits) > 0) {
		const struct mnemonic *m = match_instruction(bits);
		if (!m) {
			fprintf(out, "\t.word   0x%04x\n", bits);
			continue;
		}

		fprintf(out, "\t%s", m->mnem);
		for (int i = 0; i < 3 && m->operands[i].type; i++) {
			if (i) fprintf(out, ", ");
			else   fprintf(out, "%*s", 8 - (int)strlen(m->mnem), "");
			print_operand(out, bits, m->operands + i);
		}
		fprintf(out, "\n");
	}

	fclose(in);
	fclose(out);
	return 0;
}