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

AsmRule **asmrule;
int nasmrule;

static void
addrule(AsmRule a)
{
	if(nasmrule%32 == 0)
		asmrule = erealloc(asmrule, (nasmrule+32)*sizeof(asmrule[0]));
	asmrule[nasmrule++] = a;
}

void
readrules(void)
{
	char *s;
	int nf;
	char *f[10], *g[2];
	int i, n;
	AsmRule a;
	Biobuf *b;

	if((b = Bopen("inst.txt", OREAD)) == nil)
		sysfatal("open inst.txt: %r");

	while((s = Brdline(b, '\n')) != nil){
		s[Blinelen(b)-1] = '\0';
		memset(&a, 0, sizeof a);
		if((nf = getfields(s, f, nelem(f), 1, "\t")) != 3){
			fprint(2, "bad line: %s\n", s);
			continue;
		}
		if(getfields(f[0], a.byte, nelem(a.byte), 1, " ") >= 4){
			fprint(2, "bad bytes\n");
			continue;
		}
		for(i=0; i<nelem(a.byte); i++)
			if(a.byte[i])
				a.byte[i] = atom(a.byte[i]);
		if(getfields(f[1], g, nelem(g), 1, " ") == 1)
			g[1] = "";
		a.op = atom(g[0]);
		getfields(g[1], a.arg, nelem(a.arg), 0, ",");
		for(i=0; i<nelem(a.arg); i++)
			if(a.arg[i])
				a.arg[i] = atom(a.arg[i]);
		addrule(&a);
	}
}

typedef struct Asm Asm;
struct Asm
{
	uint sib;
	uint havesib;
	uint mod;
	uint r;
	uint rm;
	uint havemodrm;
	uint disp;
	uint ndisp;
	uint imm;
	uint nimm;
};

static int
cancoerce(Asm *m, Expr *e, char *arg)
{
	switch(e->ty){
	case ExReg8:
		if(e->r8 == RAL && strcmp(arg, "AL") == 0)
			return 1;
		if(strcmp(arg, "r8") == 0){
			m->r = e->r8;
			m->havemodrm = 1;
			return 1;
		}
		if(strcmp(arg, "r/m8") == 0){
			m->rm = e->r8;
			m->havemodrm = 1;
			return 1;
		}
		return 0;

	case ExReg32:
		if(e->r32 == RAX && strcmp(arg, "EAX") == 0)
			return 1;
		if(strcmp(arg, "r32") == 0){
			m->r = e->r32;
			m->havemodrm = 1;
			return 1;
		}
		if(strcmp(arg, "r/m32") == 0){
			m->rm = e->r32;
			m->havemodrm = 1;
			return 1;
		}
		return 0;

	case ExMem:
		if(strcmp(arg, "r/m8") == 0 || strcmp(arg, "r/m32") == 0){
			m->havemodrm = 1;
			if(e->m.scale != -1 || e->m.index != -1){
				m->havesib = 1;
				m->sib = xxx;
			}
			if(e->m.disp != 0){
				
			return 1;
		}
		return 0;

	case ExConst:
		if(e->i==1 && strcmp(arg, "1") == 0)
			return 1;
		if(e->i==3 && strcmp(arg, "3") == 0)
			return 1;
		if(-128 <= (signed)e->i && (signed)e->i <= 127 && strcmp(arg, "imm8) == 0){
			m->imm = e->i;
			m->nimm = 1;
			return 1;
		}
		if(strcmp(arg, "imm32") == 0){
			m->imm = e->i;
			m->nimm = 4;
			return 1;
		}
		return 0;
}

static int
match(AsmRule *a, Inst *inst)
{
	int i;
	Asm m;

	if(inst->op != a->op)
		return 0;

	memset(&m, 0, sizeof m);
	for(i=0; i<inst->ne; i++){
		if(a->arg[i]==nil)
			return 0;
		if(!cancoerce(inst, &inst->e[i], a->arg[i]))
			return 0;
	}
	
	return 1;
}

int
assem(Inst *inst)
{
	int i;
	AsmRule *a;

	for(i=0; i<nasmrules; i++){
		a = asmrules+i;
		if(match(&a, inst))
			return 1;
	}
	fprint(2, "cannot assemble %s\n", inst->op);
	return 0;
}