#include <stdio.h>

/*
Copyright (c) 2021-2024 Devine Lu Linvega, Andrew Alderwick

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/

#define TRIM 0x0100
#define LENGTH 0x10000

typedef unsigned char Uint8;
typedef signed char Sint8;
typedef unsigned short Uint16;

typedef struct {
	char name[0x40], items[0x40][0x40];
	Uint8 len;
} Macro;

typedef struct {
	char name[0x40];
	Uint16 addr, refs;
} Label;

typedef struct {
	char name[0x40], rune;
	Uint16 addr;
} Reference;

typedef struct {
	int ptr;
	Uint8 data[LENGTH];
	Uint8 lambda_stack[0x100], lambda_ptr, lambda_len;
	Uint16 line, length, label_len, macro_len, refs_len;
	char scope[0x40], lambda_name[0x05], *location;
	Label labels[0x400];
	Macro macros[0x100];
	Reference refs[0x1000];
} Program;

char sublabel[0x40];
char token[0x40];

Program p;

/* clang-format off */

static char ops[][4] = {
	"LIT", "INC", "POP", "NIP", "SWP", "ROT", "DUP", "OVR",
	"EQU", "NEQ", "GTH", "LTH", "JMP", "JCN", "JSR", "STH",
	"LDZ", "STZ", "LDR", "STR", "LDA", "STA", "DEI", "DEO",
	"ADD", "SUB", "MUL", "DIV", "AND", "ORA", "EOR", "SFT"
};

static char *runes = "|$@&,_.-;=!?#\"%~";
static char *hexad = "0123456789abcdef";

static int   cndx(char *s, char t) { int i = 0; char c; while((c = *s++)) { if(c == t) return i; i++; } return -1; } /* chr in str */
static int   sihx(char *s) { char c; while((c = *s++)) if(cndx(hexad, c) < 0) return 0; return 1; } /* str is hex */
static int   shex(char *s) { int n = 0; char c; while((c = *s++)) { n = n << 4, n |= cndx(hexad, c); } return n; } /* str to num */
static int   scmp(char *a, char *b, int len) { int i = 0; while(a[i] == b[i]) if(!a[i] || ++i >= len) return 1; return 0; } /* str compare */
static int   slen(char *s) { int i = 0; while(s[i]) i++; return i; } /* str length */
static int   spos(char *s, char c) { Uint8 i = 0, j; while((j = s[i++])) if(j == c) return i; return -1; } /* chr position */
static char *scpy(char *src, char *dst, int len) { int i = 0; while((dst[i] = src[i]) && i < len - 2) i++; dst[i + 1] = '\0'; return dst; } /* str copy */
static char *scat(char *dst, const char *src) { char *ptr = dst + slen(dst); while(*src) *ptr++ = *src++; *ptr = '\0'; return dst; } /* str cat */

/* clang-format on */

static int parse(char *w, FILE *f);
static char *makesublabel(char *src, char *scope, char *name);

static int
error_top(const char *name, const char *msg)
{
	fprintf(stderr, "%s: %s\n", name, msg);
	return 0;
}

static int
error_asm(const char *name)
{
	fprintf(stderr, "%s: %s in @%s, %s:%d.\n", name, token, p.scope, p.location, p.line);
	return 0;
}

static char *
setlocation(char *name)
{
	p.location = name;
	p.line = 0;
	return name;
}

static Macro *
findmacro(char *name)
{
	int i;
	for(i = 0; i < p.macro_len; i++)
		if(scmp(p.macros[i].name, name, 0x40))
			return &p.macros[i];
	return NULL;
}

static Label *
findlabel(char *name)
{
	int i;
	if(name[0] == '&')
		name = makesublabel(sublabel, p.scope, name + 1);
	for(i = 0; i < p.label_len; i++)
		if(scmp(p.labels[i].name, name, 0x40))
			return &p.labels[i];
	return NULL;
}

static Uint8
findopcode(char *s)
{
	int i;
	for(i = 0; i < 0x20; i++) {
		int m = 3;
		if(!scmp(ops[i], s, 3))
			continue;
		if(!i)
			i |= (1 << 7);
		while(s[m]) {
			if(s[m] == '2')
				i |= (1 << 5);
			else if(s[m] == 'r')
				i |= (1 << 6);
			else if(s[m] == 'k')
				i |= (1 << 7);
			else
				return 0;
			m++;
		}
		return i;
	}
	return 0;
}

static int
isopcode(char *s)
{
	return findopcode(s) || scmp(s, "BRK", 4);
}

static int
makemacro(char *name, FILE *f)
{
	Macro *m;
	char word[0x40];
	if(!slen(name)) return error_asm("Macro is empty");
	if(findmacro(name)) return error_asm("Macro is duplicate");
	if(sihx(name)) return error_asm("Macro is hex number");
	if(isopcode(name)) return error_asm("Macro is opcode");
	if(p.macro_len == 0x100) return error_asm("Macros limit exceeded");
	m = &p.macros[p.macro_len++];
	scpy(name, m->name, 0x40);
	while(fscanf(f, "%63s", word) == 1) {
		if(word[0] == '{') continue;
		if(word[0] == '}') break;
		if(word[0] == '%')
			return error_asm("Macro error");
		if(m->len >= 0x40)
			return error_asm("Macro size exceeded");
		scpy(word, m->items[m->len++], 0x40);
	}
	return 1;
}

static int
makelabel(char *name)
{
	Label *l;
	if(!slen(name)) return error_asm("Label is empty");
	if(findlabel(name)) return error_asm("Label is duplicate");
	if(sihx(name)) return error_asm("Label is hex number");
	if(isopcode(name)) return error_asm("Label is opcode");
	if(cndx(runes, name[0]) >= 0) return error_asm("Label name is runic");
	if(p.label_len == 0x400) return error_asm("Labels limit exceeded");
	l = &p.labels[p.label_len++];
	l->addr = p.ptr;
	l->refs = 0;
	scpy(name, l->name, 0x40);
	return 1;
}

static char *
makelambda(int id)
{
	p.lambda_name[0] = (char)0xce;
	p.lambda_name[1] = (char)0xbb;
	p.lambda_name[2] = hexad[id >> 0x4];
	p.lambda_name[3] = hexad[id & 0xf];
	return p.lambda_name;
}

static char *
makesublabel(char *buf, char *scope, char *name)
{
	if(slen(scope) + slen(name) >= 0x3f) {
		error_asm("Sublabel length too long");
		return NULL;
	}
	return scat(scat(scpy(scope, buf, 0x40), "/"), name);
}

static int
makepad(char *w)
{
	Label *l;
	int rel = w[0] == '$' ? p.ptr : 0;
	if(sihx(w + 1))
		p.ptr = shex(w + 1) + rel;
	else if((l = findlabel(w + 1)))
		p.ptr = l->addr + rel;
	else
		return error_asm("Invalid padding");
	return 1;
}

static int
addref(char *scope, char *label, char rune, Uint16 addr)
{
	char parent[0x40];
	Reference *r;
	if(p.refs_len >= 0x1000)
		return error_asm("References limit exceeded");
	r = &p.refs[p.refs_len++];
	if(label[0] == '{') {
		p.lambda_stack[p.lambda_ptr++] = p.lambda_len;
		scpy(makelambda(p.lambda_len++), r->name, 0x40);
	} else if(label[0] == '&' || label[0] == '/') {
		if(!makesublabel(r->name, scope, label + 1))
			return error_asm("Invalid sublabel");
	} else {
		int pos = spos(label, '/');
		if(pos > 0) {
			Label *l;
			if((l = findlabel(scpy(label, parent, pos))))
				l->refs++;
		}
		scpy(label, r->name, 0x40);
	}
	r->rune = rune;
	r->addr = addr;
	return 1;
}

static int
writebyte(Uint8 b)
{
	if(p.ptr < TRIM)
		return error_asm("Writing in zero-page");
	else if(p.ptr >= 0x10000)
		return error_asm("Writing outside memory");
	else if(p.ptr < p.length)
		return error_asm("Writing rewind");
	p.data[p.ptr++] = b;
	p.length = p.ptr;
	return 1;
}

static int
writeshort(Uint16 s, int lit)
{
	return (lit ? writebyte(findopcode("LIT2")) : 1) && writebyte(s >> 8) && writebyte(s & 0xff);
}

static int
tokenize(FILE *f)
{
	unsigned int buf;
	char *cptr = token;
	while(fread(&buf, 1, 1, f)) {
		char c = (char)buf;
		if(c < 0x21) {
			*cptr++ = 0x00;
			if(c == 0x0a)
				p.line++;
			if(token[0])
				if(!parse(token, f))
					return 0;
			cptr = token;
		} else if(cptr - token < 0x3f)
			*cptr++ = c;
		else
			return error_asm("Token too long");
	}
	return 1;
}

static int
doinclude(char *filename)
{
	FILE *f;
	int res;
	if(!(f = fopen(setlocation(filename), "r")))
		return error_top("Invalid source", filename);
	res = tokenize(f);
	fclose(f);
	return res;
}

static int
parse(char *w, FILE *f)
{
	int i;
	char word[0x40], subw[0x40], c;
	Macro *m;
	switch(w[0]) {
	case '(': /* comment */
		if(slen(w) != 1) fprintf(stderr, "-- Malformed comment: %s\n", w);
		i = 1; /* track nested comment depth */
		while(fscanf(f, "%63s", word) == 1) {
			if(slen(word) != 1)
				continue;
			else if(word[0] == '(')
				i++;
			else if(word[0] == ')' && --i < 1)
				break;
		}
		break;
	case '~': /* include */
		if(!doinclude(w + 1))
			return error_asm("Invalid include");
		break;
	case '%': /* macro */
		if(!makemacro(w + 1, f))
			return error_asm("Invalid macro");
		break;
	case '$': /* pad-relative */
	case '|': /* pad-absolute */
		if(!makepad(w))
			return error_asm("Invalid padding");
		break;
	case '@': /* label */
		if(!makelabel(w + 1))
			return error_asm("Invalid label");
		i = 0;
		while(w[i + 1] != '/' && i < 0x3e && (p.scope[i] = w[i + 1]))
			i++;
		p.scope[i] = '\0';
		break;
	case '&': /* sublabel */
		if(!makesublabel(subw, p.scope, w + 1) || !makelabel(subw))
			return error_asm("Invalid sublabel");
		break;
	case '#': /* literals hex */
		if(sihx(w + 1) && slen(w) == 3)
			return writebyte(findopcode("LIT")) && writebyte(shex(w + 1));
		else if(sihx(w + 1) && slen(w) == 5)
			return writeshort(shex(w + 1), 1);
		else
			return error_asm("Invalid hex literal");
		break;
	case '_': /* raw byte relative */
		return addref(p.scope, w + 1, w[0], p.ptr) && writebyte(0xff);
	case ',': /* literal byte relative */
		return addref(p.scope, w + 1, w[0], p.ptr + 1) && writebyte(findopcode("LIT")) && writebyte(0xff);
	case '-': /* raw byte absolute */
		return addref(p.scope, w + 1, w[0], p.ptr) && writebyte(0xff);
	case '.': /* literal byte zero-page */
		return addref(p.scope, w + 1, w[0], p.ptr + 1) && writebyte(findopcode("LIT")) && writebyte(0xff);
	case ':': fprintf(stderr, "Deprecated rune %s, use =%s\n", w, w + 1);
	case '=': /* raw short absolute */
		return addref(p.scope, w + 1, w[0], p.ptr) && writeshort(0xffff, 0);
	case ';': /* literal short absolute */
		return addref(p.scope, w + 1, w[0], p.ptr + 1) && writeshort(0xffff, 1);
	case '?': /* JCI */
		return addref(p.scope, w + 1, w[0], p.ptr + 1) && writebyte(0x20) && writeshort(0xffff, 0);
	case '!': /* JMI */
		return addref(p.scope, w + 1, w[0], p.ptr + 1) && writebyte(0x40) && writeshort(0xffff, 0);
	case '"': /* raw string */
		i = 0;
		while((c = w[++i]))
			if(!writebyte(c)) return 0;
		break;
	case '}': /* lambda end */
		if(!makelabel(makelambda(p.lambda_stack[--p.lambda_ptr])))
			return error_asm("Invalid label");
		break;
	case '[':
	case ']':
		if(slen(w) == 1) break; /* else fallthrough */
	default:
		/* opcode */
		if(isopcode(w))
			return writebyte(findopcode(w));
		/* raw byte */
		else if(sihx(w) && slen(w) == 2)
			return writebyte(shex(w));
		/* raw short */
		else if(sihx(w) && slen(w) == 4)
			return writeshort(shex(w), 0);
		/* macro */
		else if((m = findmacro(w))) {
			for(i = 0; i < m->len; i++)
				if(!parse(m->items[i], f))
					return 0;
			return 1;
		} else
			return addref(p.scope, w, ' ', p.ptr + 1) && writebyte(0x60) && writeshort(0xffff, 0);
	}
	return 1;
}

static int
resolve(void)
{
	Label *l;
	int i;
	Uint16 a;
	for(i = 0; i < p.refs_len; i++) {
		Reference *r = &p.refs[i];
		switch(r->rune) {
		case '_':
		case ',':
			if(!(l = findlabel(r->name)))
				return error_top("Unknown relative reference", r->name);
			p.data[r->addr] = (Sint8)(l->addr - r->addr - 2);
			if((Sint8)p.data[r->addr] != (l->addr - r->addr - 2))
				return error_top("Relative reference is too far", r->name);
			l->refs++;
			break;
		case '-':
		case '.':
			if(!(l = findlabel(r->name)))
				return error_top("Unknown zero-page reference", r->name);
			p.data[r->addr] = l->addr & 0xff;
			l->refs++;
			break;
		case ':':
		case '=':
		case ';':
			if(!(l = findlabel(r->name)))
				return error_top("Unknown absolute reference", r->name);
			p.data[r->addr] = l->addr >> 0x8;
			p.data[r->addr + 1] = l->addr & 0xff;
			l->refs++;
			break;
		case '?':
		case '!':
		default:
			if(!(l = findlabel(r->name)))
				return error_top("Unknown absolute reference", r->name);
			a = l->addr - r->addr - 2;
			p.data[r->addr] = a >> 0x8;
			p.data[r->addr + 1] = a & 0xff;
			l->refs++;
			break;
		}
	}
	return 1;
}

static int
assemble(char *filename)
{
	p.ptr = 0x100;
	scpy("on-reset", p.scope, 0x40);
	return doinclude(filename) && resolve();
}

static void
review(char *filename)
{
	int i;
	for(i = 0; i < p.label_len; i++)
		if(p.labels[i].name[0] - 'A' > 25 && !p.labels[i].refs)
			fprintf(stdout, "-- Unused label: %s\n", p.labels[i].name);
	fprintf(stdout,
		"Assembled %s in %d bytes(%.2f%% used), %d labels, %d macros.\n",
		filename,
		p.length - TRIM,
		(p.length - TRIM) / 652.80,
		p.label_len,
		p.macro_len);
}

static void
writesym(char *filename)
{
	int i;
	char symdst[0x60];
	FILE *fp;
	if(slen(filename) > 0x60 - 5)
		return;
	fp = fopen(scat(scpy(filename, symdst, slen(filename) + 1), ".sym"), "w");
	if(fp != NULL) {
		for(i = 0; i < p.label_len; i++) {
			Uint8 hb = p.labels[i].addr >> 8, lb = p.labels[i].addr & 0xff;
			fwrite(&hb, 1, 1, fp);
			fwrite(&lb, 1, 1, fp);
			fwrite(p.labels[i].name, slen(p.labels[i].name) + 1, 1, fp);
		}
	}
	fclose(fp);
}

int
main(int argc, char *argv[])
{
	FILE *dst;
	if(argc == 1) return error_top("usage", "uxnasm [-v] input.tal output.rom");
	if(scmp(argv[1], "-v", 2)) return !fprintf(stdout, "Uxnasm - Uxntal Assembler, 26 Mar 2024.\n");
	if(!assemble(argv[1])) return !error_top("Assembly", "Failed to assemble rom.");
	if(!(dst = fopen(argv[2], "wb"))) return !error_top("Invalid Output", argv[2]);
	if(p.length <= TRIM) return !error_top("Assembly", "Output rom is empty.");
	review(argv[2]);
	fwrite(p.data + TRIM, p.length - TRIM, 1, dst);
	writesym(argv[2]);
	return 0;
}