#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "vm.h"
#include "ast.h"
#include "value.h"
#include "list.h"
#include "closure.h"
#include "activation.h"
#include "builtin.h"
#include "icode.h"

extern int trace_gen;

static vm_label_t gptr, program;

/*
vm_label_t patch_stack[4096];
int psp = 0;

unsigned char *last_ins_at = NULL;
unsigned char last_ins = 255;
*/

#if 0

/*** backpatcher ***/

static int
request_backpatch(vm_label_t *bp)
{
#ifdef DEBUG
	if (trace_gen)
		printf("[--> #%d]", *bp - program);
#endif
	patch_stack[psp++] = *bp;
	*bp += sizeof(vm_label_t);
	return(psp - 1);
}

static void
backpatch(int bpid)
{
	vm_label_t bp;

	bp = patch_stack[bpid];
	*(vm_label_t *)bp = gptr;
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: [<-- #%d] $%d:\n", gptr - program, bp - program, bpid);
#endif
}

/*** generators ***/

static void
gen(unsigned char ins)
{
	last_ins_at = gptr;
	*gptr++ = last_ins = ins;
}

static void
gen_push_value(struct value *v)
{
#ifdef DEBUG
	if (trace_gen) {
		printf("#%d: *PUSH_VALUE(", gptr - program);
		value_print(v);
		printf(")\n");
	}
#endif

	gen(INSTR_PUSH_VALUE);
	*(((struct value **)gptr)++) = v;
}

static void
gen_push_local(int index, int upcount)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *PUSH_LOCAL(%d,%d)\n", gptr - program, index, upcount);
#endif

	gen(INSTR_PUSH_LOCAL);
	*gptr++ = (unsigned char)index;
	*gptr++ = (unsigned char)upcount;
}

static void
gen_pop_local(int index, int upcount)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *POP_LOCAL(%d,%d)\n", gptr - program, index, upcount);
#endif

	gen(INSTR_POP_LOCAL);
	*gptr++ = (unsigned char)index;
	*gptr++ = (unsigned char)upcount;
}

static void
gen_builtin(struct builtin *bi)
{
	if (bi->index >= 0) {
#ifdef DEBUG
		if (trace_gen)
			printf("#%d: *BUILTIN(%s)\n", gptr - program, bi->name);
#endif
		gen(bi->index);
	} else {
#ifdef DEBUG
		if (trace_gen)
			printf("#%d: *EXTERNAL(%s)\n", gptr - program, bi->name);
#endif
		gen(INSTR_EXTERNAL);
		*(((struct builtin **)gptr)++) = bi;
	}
}

static void
gen_jz_bp(int *bpid)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *JZ", gptr - program);
#endif
	gen(INSTR_JZ);
	*bpid = request_backpatch(&gptr);
#ifdef DEBUG
	if (trace_gen)
		printf("($%d)\n", *bpid);
#endif
}

static void
gen_jmp_bp(int *bpid)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *JMP", gptr - program);
#endif
	gen(INSTR_JMP);
	*bpid = request_backpatch(&gptr);
#ifdef DEBUG
	if (trace_gen)
		printf("($%d)\n", *bpid);
#endif
}

static void
gen_jmp(vm_label_t label)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *JMP", gptr - program);
#endif
	gen(INSTR_JMP);
	*(vm_label_t *)gptr = label;
	gptr += sizeof(vm_label_t);
#ifdef DEBUG
	if (trace_gen)
		printf("(#%d)\n", label - program);
#endif
}

static void
gen_apply(void)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *CALL\n", gptr - program);
#endif
	gen(INSTR_CALL);
}

static void
gen_ret(void)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *RET\n", gptr - program);
#endif
	if (last_ins == INSTR_CALL) {
#ifdef DEBUG
		if (trace_gen)
			printf("*** ELIMINATING TAIL CALL\n");
#endif
		*last_ins_at = INSTR_GOTO;
	}
	gen(INSTR_RET);
}

static void
gen_set_activation(void)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *SET_ACTIVATION\n", gptr - program);
#endif
	gen(INSTR_SET_ACTIVATION);
}

static void
gen_cow_local(int index, int upcount)
{
#ifdef DEBUG
	if (trace_gen)
		printf("#%d: *COW_LOCAL(%d,%d)\n", gptr - program, index, upcount);
#endif

	gen(INSTR_COW_LOCAL);
	*gptr++ = (unsigned char)index;
	*gptr++ = (unsigned char)upcount;
}

/*** gen VM from AST ***/

static void
ast_gen_r(struct ast *a)
{
	int bpid_1, bpid_2;
	vm_label_t label;
	struct value *v;

	if (a == NULL)
		return;

	a->label = gptr;
	switch (a->type) {
	case AST_LOCAL:
		gen_push_local(a->u.local.index, a->u.local.upcount);
		break;
	case AST_VALUE:
		gen_push_value(a->u.value.value);
		if (a->u.value.value->type == VALUE_CLOSURE) {
			gen_set_activation();
			gen_jmp_bp(&bpid_1);
			a->u.value.value->v.k->label = gptr;
			ast_gen_r(a->u.value.value->v.k->ast);
			gen_ret();
			backpatch(bpid_1);
		}
		break;
	case AST_BUILTIN:
		if (a->u.builtin.bi->index == INDEX_BUILTIN_STORE) {
			struct ast *lvalue;
			
			lvalue = ast_find_local(a);
			gen_cow_local(lvalue->u.local.index, lvalue->u.local.upcount);
		}
		ast_gen_r(a->u.builtin.right);
		if (a->u.builtin.bi->arity == -1) {
			v = value_new_integer(ast_count_args(a->u.builtin.right));
			value_deregister(v);
			gen_push_value(v);
		}
		gen_builtin(a->u.builtin.bi);
		break;
	case AST_APPLY:
		ast_gen_r(a->u.apply.right);
		ast_gen_r(a->u.apply.left);
		gen_apply();
		break;
	case AST_ROUTINE:
		ast_gen_r(a->u.routine.body);
		break;
	case AST_ARG:
		ast_gen_r(a->u.arg.left);
		ast_gen_r(a->u.arg.right);
		break;
	case AST_STATEMENT:
		ast_gen_r(a->u.statement.left);
		ast_gen_r(a->u.statement.right);
		break;
	case AST_ASSIGNMENT:
		assert(a->u.assignment.left != NULL);
		assert(a->u.assignment.left->type == AST_LOCAL);
		ast_gen_r(a->u.assignment.right);
		if (a->u.assignment.defining) {
			/* XXX */
			/*
			gen_init_local(a->u.assignment.left->u.local.index,
			    a->u.assignment.left->u.local.upcount);
			*/
		} else {
			gen_pop_local(a->u.assignment.left->u.local.index,
			    a->u.assignment.left->u.local.upcount);
		}
		break;
	case AST_CONDITIONAL:
		ast_gen_r(a->u.conditional.test);
		gen_jz_bp(&bpid_1);
		ast_gen_r(a->u.conditional.yes);
		if (a->u.conditional.no != NULL)
			gen_jmp_bp(&bpid_2);
		backpatch(bpid_1);
		if (a->u.conditional.no != NULL) {
			ast_gen_r(a->u.conditional.no);
			backpatch(bpid_2);
		}
		break;
	case AST_WHILE_LOOP:
		label = gptr;
		ast_gen_r(a->u.while_loop.test);
		gen_jz_bp(&bpid_1);
		ast_gen_r(a->u.while_loop.body);
		gen_jmp(label);
		backpatch(bpid_1);
		break;
	case AST_RETR:
		ast_gen_r(a->u.retr.body);
		gen_ret();
		break;
	}
}

void
ast_gen(vm_label_t *given_prog, struct ast *a)
{
	program = *given_prog;
	gptr = *given_prog;
	ast_gen_r(a);
	*gptr++ = INSTR_HALT;
}

#else
#define gen(x)	*gptr++ = x
#endif

/*** gen VM from iprogram ***/

void
iprogram_gen(vm_label_t *given_prog, struct iprogram *ip)
{
	struct icode *ic;
	struct {
		vm_label_t label;
		struct icode *icode;
	} bp[2048];
	int bpi = 0;
	struct closure *k[2048];
	int ki = 0;

	program = *given_prog;
	gptr = *given_prog;

	for (ic = ip->head; ic != NULL; ic = ic->next) {
		ic->label = gptr;
		gen(ic->opcode);
		switch (ic->opcode) {
		case INSTR_PUSH_VALUE:
			if (ic->operand.value.type == VALUE_CLOSURE) {
				k[ki++] = ic->operand.value.v.s->v.k;
			}
			*(((struct value *)gptr)++) = ic->operand.value;
			break;
		case INSTR_PUSH_LOCAL:
		case INSTR_POP_LOCAL:
		case INSTR_COW_LOCAL:
		case INSTR_INIT_LOCAL:
			*gptr++ = (unsigned char)ic->operand.local.index;
			*gptr++ = (unsigned char)ic->operand.local.upcount;
			break;
		case INSTR_JZ:
		case INSTR_JMP:
			bp[bpi].label = gptr;
			bp[bpi].icode = ic->operand.branch;
			bpi++;
			gptr += sizeof(vm_label_t);
			break;
		case INSTR_EXTERNAL:
			*(((struct builtin **)gptr)++) = ic->operand.builtin;
			break;
		}
	}

	/* Backpatching run. */
	bpi--;
	while (bpi >= 0) {
		*(vm_label_t *)bp[bpi].label = bp[bpi].icode->label;
		bpi--;
	}

	/* Resolve addresses of all closures. */
	ki--;
	while (ki >= 0) {
		k[ki]->label = k[ki]->icode->label;
		ki--;
	}
}