/*
 * call-seq:
 *  Ogg::Vorbis::Tagger.new(filename) -> object
 *
 * Returns a new Ogg::Vorbis::Tagger object for the specified file.
 *
 * FIXME: add optional mode argument (read-only or read-write)
 */
static VALUE
c_init (VALUE self, VALUE filename)
{
        RbVorbisTagger *o;
        vorbis_comment *vc;
        int i;

        Data_Get_Struct (self, RbVorbisTagger, o);

        StringValue (filename);

        o->state = vcedit_state_new (StringValuePtr (filename));
        if (!o->state)
                rb_raise (rb_eNoMemError, "Out of Memory");

        switch (vcedit_open (o->state)) {
                case VCEDIT_ERR_OPEN:
                        rb_raise (eOpen, "Cannot open file");
                case VCEDIT_ERR_INVAL:
                        rb_raise (eInvalidData, "Invalid data");
                default:
                        break;
        }

        vc = vcedit_comments (o->state);

        /* vcedit_open() succeeded, so vcedit_comments() cannot
         * return NULL.
         */
        assert (vc);

        /* check whether all comments are well-formed */
        for (i = 0; i < vc->comments; i++) {
                char *ptr, *content = vc->user_comments[i];

                ptr = strchr (content, '=');
                if (!ptr || ptr == content)
                        rb_raise (eInvalidComment, "invalid comment - %s", content);
        }

        o->comments = rb_class_new_instance (0, NULL, cComments);

        comments_init (o->comments, o->state);

        return self;
}

/*
 * call-seq:
 *  Ogg::Vorbis::Tagger.open(arg)                    -> object
 *  Ogg::Vorbis::Tagger.open(arg) { |object| block } -> object
 *
 * If a block isn't specified, Ogg::Vorbis::Tagger.open is a synonym
 * for Ogg::Vorbis::Tagger.new.
 * If a block is given, it will be invoked with the * Ogg::Vorbis::Tagger
 * object as a parameter.
 */
static VALUE
c_open (VALUE klass, VALUE arg)
{
        VALUE obj = rb_class_new_instance (1, &arg, klass);

        if (rb_block_given_p ())
                return rb_ensure (rb_yield, obj, c_close, obj);
        else
                return obj;
}

/*
 * call-seq:
 *  object.close -> nil
 *
 * Closes *object*. Further method calls on *object* will raise an
 * Ogg::Vorbis::Tagger::ClosedStreamError exception.
 * Returns +nil+.
 */
static VALUE
c_close (VALUE self)
{
        RbVorbisTagger *o;

        Data_Get_Struct (self, RbVorbisTagger, o);

        CHECK_CLOSED (o);

        vcedit_state_unref (o->state);
        o->state = NULL;

        return Qnil;
}

/*
 * call-seq:
 *  object.comments -> comments
 *
 * Returns the comments collection of *object*, which is an instance of
 * Ogg::Vorbis::Comments.
 */
static VALUE
c_comments (VALUE self)
{
        RbVorbisTagger *o;

        Data_Get_Struct (self, RbVorbisTagger, o);

        CHECK_CLOSED (o);

        return o->comments;
}

/*
 * call-seq:
 *  object.write -> integer
 *
 * Writes the comments from *object* back to the IO object and
 * returns the numbers of comments written.
 */
static VALUE
c_write (VALUE self)
{
        RbVorbisTagger *o;

        Data_Get_Struct (self, RbVorbisTagger, o);

        CHECK_CLOSED (o);

        comments_sync (o->comments, o->state);

        switch (vcedit_write (o->state)) {
                case VCEDIT_ERR_INVAL:
                        rb_raise (eInvalidData, "Invalid data");
                case VCEDIT_ERR_TMPFILE:
                        rb_raise (eTempFile, "Cannot create temporary file");
                case VCEDIT_ERR_REOPEN:
                        rb_raise (eReopen, "Cannot reopen file");
                default:
                        break;
        }

        return rb_funcall (o->comments, id_length, 0);
}