#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include "util.h"
#include "cc.h"

#define F (1<<8)
#define S (2<<8)
static void
cast(struct expr *expr)
{
	unsigned size;

	size = expr->type->size;
	if (expr->type->prop & PROPFLOAT)
		size |= F;
	else if (expr->type->prop & PROPINT && expr->type->basic.issigned)
		size |= S;
	switch (size) {
	case 1:   expr->constant.u = (uint8_t)expr->constant.u; break;
	case 1|S: expr->constant.u = (expr->constant.u & UINT8_MAX ^ INT8_MIN) - INT8_MIN; break;
	case 2:   expr->constant.u = (uint16_t)expr->constant.u; break;
	case 2|S: expr->constant.u = (expr->constant.u & UINT16_MAX ^ INT16_MIN) - INT16_MIN; break;
	case 4:   expr->constant.u = (uint32_t)expr->constant.u; break;
	case 4|S: expr->constant.u = (expr->constant.u & UINT32_MAX ^ INT32_MIN) - INT32_MIN; break;
	case 4|F: expr->constant.f = (float)expr->constant.f; break;
	}
}

static void
binary(struct expr *expr, enum tokenkind op, struct expr *l, struct expr *r)
{
	expr->kind = EXPRCONST;
	if (l->type->prop & PROPFLOAT)
		op |= F;
	else if (l->type->prop & PROPINT && l->type->basic.issigned)
		op |= S;
	switch (op) {
	case TMUL:
	case TMUL|S:     expr->constant.u = l->constant.u * r->constant.u; break;
	case TMUL|F:     expr->constant.f = l->constant.f * r->constant.f; break;
	case TDIV:       expr->constant.u = l->constant.u / r->constant.u; break;
	case TDIV|S:     expr->constant.i = l->constant.i / r->constant.i; break;
	case TDIV|F:     expr->constant.f = l->constant.f / r->constant.f; break;
	case TMOD:       expr->constant.u = l->constant.u % r->constant.u; break;
	case TMOD|S:     expr->constant.i = l->constant.i % r->constant.i; break;
	case TADD:
	case TADD|S:     expr->constant.u = l->constant.u + r->constant.u; break;
	case TADD|F:     expr->constant.f = l->constant.f + r->constant.f; break;
	case TSUB:
	case TSUB|S:     expr->constant.u = l->constant.u - r->constant.u; break;
	case TSUB|F:     expr->constant.f = l->constant.f - r->constant.f; break;
	case TSHL:
	case TSHL|S:     expr->constant.u = l->constant.u << (r->constant.u & 63); break;
	case TSHR:       expr->constant.u = l->constant.u >> (r->constant.u & 63); break;
	case TSHR|S:     expr->constant.i = l->constant.i >> (r->constant.u & 63); break;
	case TBAND:
	case TBAND|S:    expr->constant.u = l->constant.u & r->constant.u; break;
	case TBOR:
	case TBOR|S:     expr->constant.u = l->constant.u | r->constant.u; break;
	case TXOR:
	case TXOR|S:     expr->constant.u = l->constant.u ^ r->constant.u; break;
	case TLESS:      expr->constant.u = l->constant.u < r->constant.u; break;
	case TLESS|S:    expr->constant.u = l->constant.i < r->constant.i; break;
	case TLESS|F:    expr->constant.u = l->constant.f < r->constant.f; break;
	case TGREATER:   expr->constant.u = l->constant.u > r->constant.u; break;
	case TGREATER|S: expr->constant.u = l->constant.i > r->constant.i; break;
	case TGREATER|F: expr->constant.u = l->constant.f > r->constant.f; break;
	case TLEQ:       expr->constant.u = l->constant.u <= r->constant.u; break;
	case TLEQ|S:     expr->constant.u = l->constant.i <= r->constant.i; break;
	case TLEQ|F:     expr->constant.u = l->constant.f <= r->constant.f; break;
	case TGEQ:       expr->constant.u = l->constant.u >= r->constant.u; break;
	case TGEQ|S:     expr->constant.u = l->constant.i >= r->constant.i; break;
	case TGEQ|F:     expr->constant.u = l->constant.f >= r->constant.f; break;
	case TEQL:
	case TEQL|S:     expr->constant.u = l->constant.u == r->constant.u; break;
	case TEQL|F:     expr->constant.u = l->constant.f == r->constant.f; break;
	case TNEQ:
	case TNEQ|S:     expr->constant.u = l->constant.u != r->constant.u; break;
	case TNEQ|F:     expr->constant.u = l->constant.f != r->constant.f; break;
	default:
		fatal("internal error; unknown binary expression");
	}
	cast(expr);
}
#undef F
#undef S

struct expr *
eval(struct expr *expr, enum evalkind kind)
{
	struct expr *l, *r, *c;
	struct decl *d;

	switch (expr->kind) {
	case EXPRIDENT:
		if (expr->ident.decl->kind != DECLCONST)
			break;
		expr->kind = EXPRCONST;
		expr->constant.u = intconstvalue(expr->ident.decl->value);
		break;
	case EXPRCOMPOUND:
		if (kind != EVALINIT)
			break;
		d = mkdecl(DECLOBJECT, expr->type, expr->qual, LINKNONE);
		d->value = mkglobal(NULL, true);
		emitdata(d, expr->compound.init);
		expr->kind = EXPRIDENT;
		expr->ident.decl = d;
		break;
	case EXPRUNARY:
		l = eval(expr->base, kind);
		if (expr->op != TBAND)
			break;
		switch (l->kind) {
		case EXPRUNARY:
			if (l->op == TMUL)
				expr = eval(l->base, kind);
			break;
		case EXPRSTRING:
			if (kind != EVALINIT)
				break;
			l->ident.decl = stringdecl(l);
			l->kind = EXPRIDENT;
			expr->base = l;
			break;
		}
		break;
	case EXPRCAST:
		l = eval(expr->base, kind);
		if (l->kind == EXPRCONST) {
			expr->kind = EXPRCONST;
			if (l->type->prop & PROPINT && expr->type->prop & PROPFLOAT)
				expr->constant.f = l->constant.u;
			else if (l->type->prop & PROPFLOAT && expr->type->prop & PROPINT)
				expr->constant.u = l->constant.f;
			else
				expr->constant = l->constant;
			cast(expr);
		} else if (l->type->kind == TYPEPOINTER) {
			/*
			A cast from a pointer to integer is not a valid constant
			expression, but C11 allows implementations to recognize
			other forms of constant expressions (6.6p10), and some
			programs expect this functionality.
			*/
			if (expr->type->kind == TYPEPOINTER || expr->type->prop & PROPINT && expr->type->size == typelong.size)
				expr = l;
		}
		break;
	case EXPRBINARY:
		l = eval(expr->binary.l, kind);
		r = eval(expr->binary.r, kind);
		expr->binary.l = l;
		expr->binary.r = r;
		switch (expr->op) {
		case TADD:
			if (r->kind == EXPRBINARY)
				c = l, l = r, r = c;
			/* fallthrough */
		case TSUB:
			if (r->kind != EXPRCONST)
				break;
			if (l->kind == EXPRCONST) {
				binary(expr, expr->op, l, r);
			} else if (l->kind == EXPRBINARY && l->type->kind == TYPEPOINTER && l->op == TADD && l->binary.r->kind == EXPRCONST) {
				/* (P + C1) ± C2  ->  P + (C1 ± C2) */
				binary(expr->binary.r, expr->op, l->binary.r, r);
				expr->op = TADD;
				expr->binary.l = l->binary.l;
			}
			break;
		case TLOR:
			if (l->kind != EXPRCONST)
				break;
			return l->constant.u ? l : r;
		case TLAND:
			if (l->kind != EXPRCONST)
				break;
			return l->constant.u ? r : l;
		default:
			if (l->kind != EXPRCONST || r->kind != EXPRCONST)
				break;
			binary(expr, expr->op, l, r);
		}
		break;
	}

	return expr;
}