/*
 *  Render C declarations as English.
 *  Copyright © 2011, 2021, 2023-2024 Nick Bowler
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <inttypes.h>

#include "cdecl.h"
#include "cdecl-internal.h"

#define PRE_SPECS (CDECL_SPEC_FUNC|CDECL_SPEC_STOR)
#define POST_SPECS (CDECL_SPEC_QUAL|CDECL_SPEC_TYPE)

static void explain_specs(struct output_state *dst, struct cdecl_declspec *s, unsigned mask)
{
	cdecl__emit(dst, cdecl__emit_specs(dst, s, mask));
}

/*
 * If declarator declares an identifier foo, then emit "foo as "; otherwise
 * emit nothing.
 */
static void
explain_name(struct output_state *dst, struct cdecl_declarator *d)
{
	while (d->child)
		d = d->child;

	if (d->type == CDECL_DECL_IDENT) {
		cdecl__emit(dst, d->u.ident);
		cdecl__emit(dst, " as ");
	}
}

/*
 * For a pointer declarator, emit "[QUAL ]pointer to ", where
 * QUAL is the (possibly empty) list of qualifiers.
 */
static void
explain_pointer(struct output_state *dst, struct cdecl_pointer *p)
{
	explain_specs(dst, p->qualifiers, -1);
	cdecl__emit(dst, "pointer to ");
}

/*
 * For an array declarator, emit "[variable-length ]array [X ]of ", where
 * for a variable-length array X is the (possibly omitted) identifier name,
 * and for normal arrays X is the (possibly omitted) length.
 */
static void
explain_array(struct output_state *dst, struct cdecl_array *a)
{
	size_t rc = 0;

	cdecl__emit(dst, "variable-length array " + (a->vla ? 0 : 16));
	if (a->vla) {
		rc = cdecl__emit(dst, a->vla);
	} else {
		rc = cdecl__emit_uint(dst, a->length);
	}
	cdecl__emit(dst, " of " + !rc);
}

static void
explain_declarators(struct output_state *dst, struct cdecl_declarator *decl);

static void explain_decl(struct output_state *dst, struct cdecl *decl)
{
	explain_name(dst, decl->declarators);
	explain_specs(dst, decl->specifiers, PRE_SPECS);
	explain_declarators(dst, decl->declarators);
	cdecl__emit_specs(dst, decl->specifiers, POST_SPECS);
}

/*
 * For a function declarator, emit "function [PARAM ]returning ", where
 * PARAM is the (omitted in the case of an empty non-prototype identifier
 * list) parameter or identifier lists enclosed in parentheses.
 */
static void
explain_function(struct output_state *dst, struct cdecl_function *f)
{
	int tail_offset = 7;

	cdecl__emit(dst, "function ");
	if (f->parameters) {
		struct cdecl *p;

		cdecl__emit(dst, "(");

		for (p = f->parameters; p; p = p->next) {
			explain_decl(dst, p);
			if (p->next)
				cdecl__emit(dst, ", ");
		}

		tail_offset = f->variadic ? 0 : 5;
	}
	cdecl__emit(dst, ", ...) returning " + tail_offset);
}

static void
explain_declarators(struct output_state *dst, struct cdecl_declarator *d)
{
	if (d->child)
		explain_declarators(dst, d->child);

	switch (d->type) {
	case CDECL_DECL_POINTER:
		explain_pointer(dst, &d->u.pointer);
		return;
	case CDECL_DECL_ARRAY:
		explain_array(dst, &d->u.array);
		return;
	case CDECL_DECL_FUNCTION:
		explain_function(dst, &d->u.function);
		return;
	}
}

size_t cdecl_explain(char *buf, size_t n, struct cdecl *decl)
{
	struct output_state dst = { buf, n };

	if (cdecl_is_abstract(decl->declarators))
		cdecl__emit(&dst, "type ");
	else
		cdecl__emit(&dst, "declare ");

	explain_decl(&dst, decl);
	return dst.accum;
}