/* bas.c - API for writing standalone programs that deal with
	tokenized Atari 8-bit BASIC program. */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>

#include "bas.h"

int verbose = 0;
unsigned short lomem;
unsigned short vntp;
unsigned short vntd;
unsigned short vvtp;
unsigned short stmtab;
unsigned short stmcur;
unsigned short starp;
unsigned short codestart;
unsigned short code_end;
unsigned short vnstart;
unsigned short vvstart;
int filelen;
const char *self;
unsigned char program[BUFSIZE];
FILE *input_file;
FILE *output_file;
char *output_filename = NULL;

void die(const char *msg) {
	fprintf(stderr, "%s: %s\n", self, msg);
	exit(1);
}

void parse_general_args(int argc, char **argv, void (*helpfunc)()) {
	if(argc < 2) {
		(*helpfunc)();
		exit(1);
	}

	if(strcmp(argv[1], "--help") == 0) {
		(*helpfunc)();
		exit(0);
	}

	if(strcmp(argv[1], "--version") == 0) {
		printf("%s %s\n", self, VERSION);
		exit(0);
	}
}

/* read entire file into memory */
void readfile(void) {
	filelen = fread(program, 1, BUFSIZE - 1, input_file);
	if(verbose) fprintf(stderr, "Read %d bytes.\n", filelen);
	if(!feof(input_file))
		fprintf(stderr, "Warning: file is >64KB, way too big for a BASIC program.\n");
	else if(filelen > MAX_PROG_SIZE)
		fprintf(stderr, "Warning: file is %d bytes, suspiciously large for a BASIC program.\n", filelen);
	fclose(input_file);
	if(filelen < MIN_PROG_SIZE)
		die("File too short to be a BASIC program (truncated?)\n");
}

int writefile(void) {
	int outbytes;

	outbytes = fwrite(program, 1, filelen, output_file);
	fclose(output_file);
	if(verbose) fprintf(stderr, "Wrote %d bytes.\n", outbytes);
	return outbytes;
}

/* get a 16-bit value from the file, in 6502 LSB/MSB order. */
unsigned short getword(int addr) {
	return program[addr] | (program[addr + 1] << 8);
}

void setword(int addr, int value) {
	program[addr] = value & 0xff;
	program[addr + 1] = value >> 8;
}

void dump_header_vars(void) {
	fprintf(stderr, "LOMEM  $%04x    VNTP $%04x   VNTD $%04x  VVTP $%04x\n", lomem, vntp, vntd, vvtp);
	fprintf(stderr, "STMTAB $%04x  STMCUR $%04x  STARP $%04x\n", stmtab, stmcur, starp);
	fprintf(stderr, "vnstart $%04x, vvstart $%04x, codestart $%04x, code_end $%04x\n", vnstart, vvstart, codestart, code_end);
}

void parse_header(void) {
	lomem = getword(0);
	vntp = getword(2);
	vntd = getword(4);
	vvtp = getword(6);
	stmtab = getword(8);
	stmcur = getword(10);
	starp = getword(12);
	codestart = stmtab - TBL_OFFSET - (vntp - 256);
	vnstart = vntp - TBL_OFFSET;
	vvstart = vvtp - TBL_OFFSET;
	code_end = starp - TBL_OFFSET;

	if(lomem) die("This doesn't look like an Atari BASIC program (no $0000 signature).");

	if(filelen < code_end) {
		fprintf(stderr, "Warning: file is truncated: %d bytes, should be %d.\n", filelen, code_end);
	}

	if(verbose) dump_header_vars();
}

void update_header(void) {
	setword(0, lomem);
	setword(2, vntp);
	setword(4, vntd);
	setword(6, vvtp);
	setword(8, stmtab);
	setword(10, stmcur);
	setword(12, starp);
}

/* sometimes the variable name table isn't large enough to hold
	the generated variable names. move_code() makes more space,
	by moving the rest of the program (including the variable value
	table) up in memory. */
void move_code(int offset) {
	unsigned char *dest = program + vvstart + offset;

	if(dest < program || ((filelen + offset) > (BUFSIZE - 1))) {
		die("Attempt to move memory out of range; corrupt header bytes?\n");
	}

	memmove(dest, program + vvstart, filelen);

	vntd += offset;
	vvtp += offset;
	stmtab += offset;
	stmcur += offset;
	starp += offset;
	filelen += offset;
	update_header();
	parse_header();
}

void adjust_vntable_size(int oldsize, int newsize) {
	int move_by;
	if(oldsize != newsize) {
		move_by = newsize - oldsize;
		if(verbose) fprintf(stderr,
				"Need %d bytes for vntable, have %d, moving VVTP by %d to $%04x.\n",
				newsize, oldsize, move_by, vvtp + move_by);
		move_code(move_by);
	}
}

/* return true if the variable name table is OK */
int vntable_ok(void) {
	int vp, bad;

	if(vntp == vntd) {
		if(verbose) fprintf(stderr, "No variables.\n");
		return 1;
	}

	/* first pass: bad = 1 if all the bytes in the table have the same
		value, no matter what it is. */
	vp = vnstart + 1;
	bad = 1;
	while(vp < vvstart - 1) {
		if(program[vp] != program[vnstart]) {
			bad = 0;
			break;
		}
		vp++;
	}
	if(bad) return 0;

	/* 2nd pass: bad = 1 if there's any invalid character in the table. */
	vp = vnstart;
	while(vp < vvstart) {
		unsigned char c = program[vp];

		/* treat a null byte as end-of-table, ignore any junk between it and VNTP. */
		if(c == 0) break;

		vp++;

		/* inverse $ or ( is OK */
		if(c == 0xa4 || c == 0xa8) continue;

		/* numbers and letters are allowed, inverse or normal. */
		c &= 0x7f;
		if(c >= 0x30 && c <= 0x39) continue;
		if(c >= 0x41 && c <= 0x5a) continue;

		bad++;
		break;
	}

	return !bad;
}

void invalid_args(const char *arg) {
	fprintf(stderr, "%s: Invalid argument '%s'.\n\n", self, arg);
	exit(1);
}

FILE *open_file(const char *name, const char *mode) {
	FILE *fp;
	if(!(fp = fopen(name, mode))) {
		perror(name);
		exit(1);
	}
	return fp;
}

void open_input(const char *name) {
	if(!name || strcmp(name, "-") == 0) {
		if(isatty(fileno(stdin))) {
			die("Can't read binary data from the terminal.");
		}
		if(freopen(NULL, "rb", stdin)) {
			input_file = stdin;
			return;
		} else {
			perror("stdin");
			exit(1);
		}
	}

	input_file = open_file(name, "rb");
}

void open_output(const char *name) {
	if(!name || (strcmp(name, "-") == 0)) {
		if(isatty(fileno(stdout))) {
			die("Refusing to write binary data to the terminal.");
		}
		if(freopen(NULL, "wb", stdout)) {
			output_file = stdout;
			return;
		} else {
			perror("stdout");
			exit(1);
		}
	}
	output_file = open_file(name, "wb");
}

extern void set_self(const char *argv0) {
	char *p;

	self = argv0;
	p = strrchr(self, '/');
	if(p) self = p + 1;
}