static bool cgen_decls_stmt(CGenerator *g, Statement *s);
static bool cgen_decls_block(CGenerator *g, Block *b);

static bool cgen_decls_expr(CGenerator *g, Expression *e) {
	cgen_recurse_subexprs(g, e, cgen_decls_expr, cgen_decls_block);
	switch (e->kind) {
	case EXPR_CALL: {
		e->call.c.instance = 0;
		assert(e->call.fn->type.kind == TYPE_FN);
		FnType *fn_type = &e->call.fn->type.fn;
		if (fn_type->constant) {
			Value fval;
			/* e->call.fn had better be a compile-time constant if it has compile-time arguments */
			if (!eval_expr(g->evalr, e->call.fn, &fval))
				return false;
			FnExpr *f = fval.fn;
			/* directly calling a function; might need to generate a copy of this function */

			/* OPTIM should we really be constructing a tuple & type every time? */
			Value *compile_time_args = NULL;
			Type *tuple_types = NULL;
			size_t nparams = arr_len(fn_type->types)-1;
			for (size_t i = 0; i < nparams; i++) {
				if (fn_type->constant[i]) {
					Expression *arg = &e->call.arg_exprs[i];
					assert(arg->kind == EXPR_VAL); /* should have been evaluated by types.c */
					*(Value *)arr_adda(&compile_time_args, g->allocr) = arg->val;
					*(Type *)arr_add(&tuple_types) = arg->type;
					i++;
				}
			}
			if (compile_time_args) {
				Value tuple;
				Type tuple_type;
				tuple.tuple = compile_time_args;
				tuple_type.kind = TYPE_TUPLE;
				tuple_type.flags = TYPE_IS_RESOLVED;
				tuple_type.tuple = tuple_types;
				if (!f->c.instances) {
					f->c.instances = allocr_calloc(g->allocr, 1, sizeof *f->c.instances);
				}
				/* lookup compile time arguments */
				I64 instance_number = (I64)f->c.instances->n + 1;
				bool already_generated_decl = val_hash_table_adda(g->allocr, f->c.instances, tuple, &tuple_type, &instance_number);
				if (!already_generated_decl) {
					/* generate a copy of this function */
					if (!cgen_fn_header(g, f, e->where, instance_number))
						return false;
					cgen_write(g, ";");
					cgen_nl(g);
				}
				arr_clear(&tuple_types);
				e->call.c.instance = (U32)instance_number;
			}
		}
	} break;
	case EXPR_FN:
		e->fn.c.name = NULL;
		if (!e->fn.c.id)
			e->fn.c.id = g->ident_counter++;
		if (!e->type.fn.constant) {
			fn_enter(&e->fn, 0);
			if (!cgen_fn_header(g, &e->fn, e->where, 0))
				return false;
			cgen_write(g, ";");
			cgen_nl(g);
			fn_exit(&e->fn);
		}
		break;	
	default:
		break;
	}
	
	return true;
}

static bool cgen_decls_block(CGenerator *g, Block *b) {
	Block *prev = g->block;
	if (!cgen_block_enter(g, b))
		return false;
	arr_foreach(b->stmts, Statement, s)
		cgen_decls_stmt(g, s);
	cgen_block_exit(g, prev);
	return true;
}

static bool cgen_decls_decl(CGenerator *g, Declaration *d) {
	if (cgen_fn_is_direct(g, d)) {
		if (!fn_has_any_const_params(&d->expr.fn)) {
			d->expr.fn.c.name = d->idents[0];
			fn_enter(&d->expr.fn, 0);
			if (!cgen_fn_header(g, &d->expr.fn, d->where, 0))
				return false;
			cgen_write(g, ";");
			cgen_nl(g);
		}
		if (!cgen_decls_block(g, &d->expr.fn.body))
			return false;
		fn_exit(&d->expr.fn);
	} else if (d->flags & DECL_HAS_EXPR) {
		if (d->flags & DECL_IS_CONST) {
			for (size_t idx = 0; idx < arr_len(d->idents); idx++) {
				Identifier i = d->idents[idx];
				Type *type = d->type.kind == TYPE_TUPLE ? &d->type.tuple[idx] : &d->type;
				if (type->kind == TYPE_TYPE) {
					Value *val = d->type.kind == TYPE_TUPLE ? &d->val.tuple[idx] : &d->val;
					if (val->type->kind == TYPE_STRUCT) {
						/* generate struct definition */
						cgen_write(g, "struct ");
						if (g->block == NULL)
							cgen_ident(g, i);
						else
							cgen_ident_id(g, d->c.ids[idx]);
						cgen_write(g, "{");
						cgen_nl(g);
						g->indent_lvl++;
						arr_foreach(val->type->struc.fields, Field, f) {
							if (!cgen_type_pre(g, f->type, d->where)) return false;
							cgen_write(g, " ");
							cgen_ident(g, f->name);
							if (!cgen_type_post(g, f->type, d->where)) return false;
							cgen_write(g, ";");
							cgen_nl(g);
						}
						g->indent_lvl--;
						cgen_write(g, "};");
						cgen_nl(g);
					}
				}
			}
		}
		if (!(d->flags & DECL_IS_CONST) || (d->expr.kind == EXPR_FN)) {
			if (!cgen_decls_expr(g, &d->expr))
				return false;
		}
	}
	return true;
}

static bool cgen_decls_stmt(CGenerator *g, Statement *s) {
	switch (s->kind) {
	case STMT_DECL:
		if (!cgen_decls_decl(g, &s->decl))
			return false;
		break;
	case STMT_EXPR:
		if (!cgen_decls_expr(g, &s->expr))
			return false;
		break;
	case STMT_RET:
		if (s->ret.flags & RET_HAS_EXPR)
			if (!cgen_decls_expr(g, &s->ret.expr))
				return false;
		break;
	}
	return true;
}

static bool cgen_decls_file(CGenerator *g, ParsedFile *f) {
	cgen_write(g, "/* declarations */\n");
	arr_foreach(f->stmts, Statement, s) {
		if (!cgen_decls_stmt(g, s))
			return false;
	}
	return true;
}