#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.
*/

/* clang-format off */

#define PAGE 0x0100

typedef unsigned char Uint8;
typedef signed char Sint8;
typedef unsigned short Uint16;
typedef struct { char *name, rune, *content; Uint16 addr, refs; } Item;
typedef struct { int line; char *path; } Context;

static int ptr, length;
static char token[0x40], scope[0x40], lambda[0x05];
static char dict[0x8000], *dictnext = dict;
static Uint8 data[0x10000], lambda_stack[0x100], lambda_ptr, lambda_len;
static Uint16 labels_len, refs_len, macro_len;
static Item labels[0x400], refs[0x1000], macros[0x100];

static char *runes = "|$@&,_.-;=!?#\"%~";
static char *hexad = "0123456789abcdef";
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 int   find(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   shex(char *s) { int n = 0; char c; while((c = *s++)) { if(find(hexad, c) < 0) return -1; n = n << 4, n |= find(hexad, c); } return n; } /* str to hex */
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 char *copy(char *src, char *dst, char c) { while(*src && *src != c) *dst++ = *src++; *dst++ = 0; return dst; } /* str copy */
static char *save(char *s, char c) { char *o = dictnext; while((*dictnext++ = *s++) && *s); *dictnext++ = c; return o; } /* save to dict */
static char *join(char *a, char j, char *b) { char *res = dictnext; save(a, j), save(b, 0); return res; } /* join two str */

#define ishex(x) (shex(x) >= 0)
#define isopc(x) (findopcode(x) || scmp(x, "BRK", 4))
#define isinvalid(x) (!x[0] || ishex(x) || isopc(x) || find(runes, x[0]) >= 0)
#define writeshort(x) (writebyte(x >> 8, ctx) && writebyte(x & 0xff, ctx))
#define findlabel(x) finditem(x, labels, labels_len)
#define findmacro(x) finditem(x, macros, macro_len)
#define error_top(name, msg) !fprintf(stderr, "%s: %s\n", name, msg)
#define error_asm(name) !fprintf(stderr, "%s: %s in @%s, %s:%d.\n", name, token, scope, ctx->path, ctx->line)

/* clang-format on */

static int parse(char *w, FILE *f, Context *ctx);

static char *
push(char *s, char c)
{
	char *d = dict;
	for(d = dict; d < dictnext; d++) {
		char *ss = s, *dd = d, a, b;
		while((a = *dd++) == (b = *ss++))
			if(!a && !b) return d;
	}
	return save(s, c);
}

static Item *
finditem(char *name, Item *list, int len)
{
	int i;
	if(name[0] == '&')
		name = join(scope, '/', name + 1);
	for(i = 0; i < len; i++)
		if(scmp(list[i].name, name, 0x40))
			return &list[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 error_top("Unknown opcode mode", s);
			m++;
		}
		return i;
	}
	return 0;
}

static int
walkcomment(FILE *f, Context *ctx)
{
	char c;
	int depth = 1;
	while(f && fread(&c, 1, 1, f)) {
		if(c == 0xa) ctx->line += 1;
		if(c == '(') depth++;
		if(c == ')' && --depth < 1) return 1;
	}
	return 0;
}

static int
walkmacro(Item *m, Context *ctx)
{
	char c, *contentptr = m->content, *cptr = token;
	while((c = *contentptr++)) {
		if(c < 0x21) {
			*cptr++ = 0x00;
			if(token[0] && !parse(token, NULL, ctx)) return 0;
			cptr = token;
		} else
			*cptr++ = c;
	}
	return 1;
}

static int
walkfile(FILE *f, Context *ctx)
{
	char c, *cptr = token;
	while(f && fread(&c, 1, 1, f)) {
		if(c == 0xa) ctx->line += 1;
		if(c < 0x21) {
			*cptr++ = 0x00;
			if(token[0] && !parse(token, f, ctx))
				return 0;
			cptr = token;
		} else if(cptr - token < 0x3f)
			*cptr++ = c;
		else
			return error_asm("Token too long");
	}
	return 1;
}

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

static int
makemacro(char *name, FILE *f, Context *ctx)
{
	char c;
	Item *m;
	if(macro_len >= 0x100) return error_asm("Macros limit exceeded");
	if(isinvalid(name)) return error_asm("Macro is invalid");
	if(findmacro(name)) return error_asm("Macro is duplicate");
	m = &macros[macro_len++];
	m->name = push(name, 0);
	m->content = dictnext;
	while(f && fread(&c, 1, 1, f) && c != '{')
		if(c == 0xa) ctx->line += 1;
	while(f && fread(&c, 1, 1, f) && c != '}') {
		if(c == 0xa) ctx->line += 1;
		if(c == '%') return error_top("Nested macro", name);
		if(c == '(')
			walkcomment(f, ctx);
		else
			*dictnext++ = c;
	}
	*dictnext++ = 0;
	return 1;
}

static int
makelabel(char *name, int setscope, Context *ctx)
{
	Item *l;
	if(name[0] == '&')
		name = join(scope, '/', name + 1);
	if(labels_len >= 0x400) return error_asm("Labels limit exceeded");
	if(isinvalid(name)) return error_asm("Label is invalid");
	if(findlabel(name)) return error_asm("Label is duplicate");
	l = &labels[labels_len++];
	l->name = push(name, 0);
	l->addr = ptr;
	l->refs = 0;
	if(setscope) copy(name, scope, '/');
	return 1;
}

static int
makeref(char *label, char rune, Uint16 addr)
{
	Item *r;
	if(refs_len >= 0x1000) return error_top("References limit exceeded", label);
	r = &refs[refs_len++];
	if(label[0] == '{') {
		lambda_stack[lambda_ptr++] = lambda_len;
		r->name = push(makelambda(lambda_len++), 0);
	} else if(label[0] == '&' || label[0] == '/') {
		r->name = join(scope, '/', label + 1);
	} else
		r->name = push(label, 0);
	r->rune = rune;
	r->addr = addr;
	return 1;
}

static int
writepad(char *w)
{
	Item *l;
	int rel = w[0] == '$' ? ptr : 0;
	if(ishex(w + 1)) {
		ptr = shex(w + 1) + rel;
		return 1;
	}
	if((l = findlabel(w + 1))) {
		ptr = l->addr + rel;
		return 1;
	}
	return 0;
}

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

static int
writehex(char *w, Context *ctx)
{
	if(*w == '#')
		writebyte(findopcode("LIT") | !!(++w)[2] << 5, ctx);
	if(w[1] && !w[2])
		return writebyte(shex(w), ctx);
	else if(w[3] && !w[4])
		return writeshort(shex(w));
	else
		return 0;
}

static int
writestring(char *w, Context *ctx)
{
	char c;
	while((c = *(w++)))
		if(!writebyte(c, ctx)) return 0;
	return 1;
}

static int
assemble(char *filename)
{
	FILE *f;
	int res = 0;
	Context ctx;
	ctx.line = 0;
	ctx.path = push(filename, 0);
	if(!(f = fopen(filename, "r")))
		return error_top("Invalid source", filename);
	res = walkfile(f, &ctx);
	fclose(f);
	return res;
}

static int
parse(char *w, FILE *f, Context *ctx)
{
	Item *m;
	switch(w[0]) {
	case '(': return !walkcomment(f, ctx) ? error_asm("Invalid comment") : 1;
	case '%': return !makemacro(w + 1, f, ctx) ? error_asm("Invalid macro") : 1;
	case '@': return !makelabel(w + 1, 1, ctx) ? error_asm("Invalid label") : 1;
	case '&': return !makelabel(w, 0, ctx) ? error_asm("Invalid sublabel") : 1;
	case '}': return !makelabel(makelambda(lambda_stack[--lambda_ptr]), 0, ctx) ? error_asm("Invalid label") : 1;
	case '#': return !ishex(w + 1) || !writehex(w, ctx) ? error_asm("Invalid hexadecimal") : 1;
	case '_': return makeref(w + 1, w[0], ptr) && writebyte(0xff, ctx);
	case ',': return makeref(w + 1, w[0], ptr + 1) && writebyte(findopcode("LIT"), ctx) && writebyte(0xff, ctx);
	case '-': return makeref(w + 1, w[0], ptr) && writebyte(0xff, ctx);
	case '.': return makeref(w + 1, w[0], ptr + 1) && writebyte(findopcode("LIT"), ctx) && writebyte(0xff, ctx);
	case ':': fprintf(stderr, "Deprecated rune %s, use =%s\n", w, w + 1); /* fall-through */
	case '=': return makeref(w + 1, w[0], ptr) && writeshort(0xffff);
	case ';': return makeref(w + 1, w[0], ptr + 1) && writebyte(findopcode("LIT2"), ctx) && writeshort(0xffff);
	case '?': return makeref(w + 1, w[0], ptr + 1) && writebyte(0x20, ctx) && writeshort(0xffff);
	case '!': return makeref(w + 1, w[0], ptr + 1) && writebyte(0x40, ctx) && writeshort(0xffff);
	case '"': return !writestring(w + 1, ctx) ? error_asm("Invalid string") : 1;
	case '~': return !assemble(w + 1) ? error_asm("Invalid include") : 1;
	case '$':
	case '|': return !writepad(w) ? error_asm("Invalid padding") : 1;
	case '[':
	case ']': return 1;
	}
	if(ishex(w)) return writehex(w, ctx);
	if(isopc(w)) return writebyte(findopcode(w), ctx);
	if((m = findmacro(w))) return walkmacro(m, ctx);
	return makeref(w, ' ', ptr + 1) && writebyte(0x60, ctx) && writeshort(0xffff);
}

static int
resolve(void)
{
	int i, rel;
	if(!length) return error_top("Assembly", "Output rom is empty.");
	for(i = 0; i < refs_len; i++) {
		Item *r = &refs[i], *l = findlabel(r->name);
		Uint8 *rom = data + r->addr;
		if(!l) return error_top("Unknown label", r->name);
		switch(r->rune) {
		case '_':
		case ',':
			*rom = rel = l->addr - r->addr - 2;
			if((Sint8)data[r->addr] != rel)
				return error_top("Relative reference is too far", r->name);
			break;
		case '-':
		case '.':
			*rom = l->addr;
			break;
		case ':':
		case '=':
		case ';':
			*rom++ = l->addr >> 8, *rom = l->addr;
			break;
		case '?':
		case '!':
		default:
			rel = l->addr - r->addr - 2;
			*rom++ = rel >> 8, *rom = rel;
			break;
		}
		l->refs++;
	}
	return 1;
}

static int
build(char *rompath)
{
	int i;
	FILE *dst, *dstsym;
	char *sympath = join(rompath, '.', "sym");
	/* rom */
	if(!(dst = fopen(rompath, "wb")))
		return !error_top("Invalid output file", rompath);
	for(i = 0; i < labels_len; i++)
		if(labels[i].name[0] - 'A' > 25 && !labels[i].refs)
			fprintf(stdout, "-- Unused label: %s\n", labels[i].name);
	fwrite(data + PAGE, length - PAGE, 1, dst);
	fprintf(stdout,
		"Assembled %s in %d bytes(%.2f%% used), %d labels, %d macros.\n",
		rompath,
		length - PAGE,
		(length - PAGE) / 652.80,
		labels_len,
		macro_len);
	/* sym */
	if(!(dstsym = fopen(sympath, "w")))
		return !error_top("Invalid symbols file", sympath);
	for(i = 0; i < labels_len; i++) {
		Uint8 hb = labels[i].addr >> 8, lb = labels[i].addr;
		char c, d = 0, *name = labels[i].name;
		fwrite(&hb, 1, 1, dstsym);
		fwrite(&lb, 1, 1, dstsym);
		while((c = *name++)) fwrite(&c, 1, 1, dstsym);
		fwrite(&d, 1, 1, dstsym);
	}
	fclose(dst), fclose(dstsym);
	return 1;
}

int
main(int argc, char *argv[])
{
	ptr = PAGE;
	copy("on-reset", scope, 0);
	if(argc == 2 && scmp(argv[1], "-v", 2)) return !fprintf(stdout, "Uxnasm - Uxntal Assembler, 29 Mar 2024.\n");
	if(argc != 3) return error_top("usage", "uxnasm [-v] input.tal output.rom");
	if(!assemble(argv[1])) return !error_top("Assembly", "Failed to assemble rom.");
	if(!length) return !error_top("Assembly", "Output rom is empty.");
	if(!resolve()) return !error_top("Assembly", "Failed to resolve symbols.");
	if(!build(argv[2])) return !error_top("Assembly", "Failed to build rom.");
	return 0;
}