#' @title ggplot-based plot for objects of class \code{"prc"}
#'
#' @description
#' Produces a multi-layer ggplot object representing the output of
#' objects produced by \code{\link[vegan]{prc}}.
#'
#' @details
#' TODO
#'
#' @param object an object inheriting from class \code{"prc"}, the
#' result of a call to \code{\link[vegan]{prc}}.
#' @param select a logical vector where \code{TRUE} selects and
#' \code{FALSE} deselects species. Alternatively a numeric vector that
#' contains the indices selecting species. Note that these are with
#' respect to the original species matrix, \strong{not} the fortified
#' object.
#' @param xlab character; label for the x-axis
#' @param ylab character; label for the y-axis
#' @param title character; subtitle for the plot
#' @param subtitle character; subtitle for the plot
#' @param caption character; caption for the plot
#' @param legend.position character; position for the legend grob. See argument
#' \code{legend.position} in function \code{\link[ggplot2]{theme}}.
#' @param ... Additional arguments passed to \code{\link{fortify.prc}}.
#'
#' @return Returns a ggplot object.
#'
#' @author Gavin L. Simpson
#'
#' @export
#'
#' @importFrom ggplot2 fortify ggplot geom_hline geom_rug geom_line theme scale_x_continuous labs aes_string
#'
#' @examples
#' data(pyrifos)
#' week <- gl(11, 12, labels=c(-4, -1, 0.1, 1, 2, 4, 8, 12, 15, 19, 24))
#' dose <- factor(rep(c(0.1, 0, 0, 0.9, 0, 44, 6, 0.1, 44, 0.9, 0, 6), 11))
#'
#' ## Fit PRC model
#' mod <- prc(pyrifos, dose, week)
#'
#' ## plot
#' want <- colSums(pyrifos)
#' autoplot(mod, select = want)
`autoplot.prc` <- function(object, select, xlab, ylab,
                           title = NULL, subtitle = NULL, caption = NULL,
                           legend.position = "top", ...) {
    ## fortify the model object
    fobj <- fortify(object, ...)

    ## levels of factors - do this now before we convert things
    TimeLevs <- levels(fobj$Time)
    TreatLevs <- levels(fobj$Treatment)

    ## convert Time to a numeric
    fobj$Time <- as.numeric(as.character(fobj$Time))

    ## process select
    ind <- fobj$score != "Sample"
    if(missing(select)) {
        select <- rep(TRUE,sum(ind))
    } else {
        stopifnot(isTRUE(all.equal(length(select), sum(ind))))
    }

    ## samples and species "scores"
    samp <- fobj[!ind, ]
    spp <- fobj[ind,][select, ]

    ## base plot
    plt <- ggplot(data = samp,
                  aes_string(x = 'Time', y = 'Response', group = 'Treatment',
                             colour = 'Treatment', linetype = 'Treatment'))
    ## add the control
    plt <- plt + geom_hline(yintercept = 0)
    ## add species rug
    plt <- plt +
        geom_rug(data = spp,
                 sides = "r",
                 mapping = aes_string(group = NULL, x = NULL,
                                      colour = NULL, linetype = NULL))
    ## add the coefficients
    plt <- plt + geom_line() +
        theme(legend.position = legend.position) +
        scale_x_continuous(breaks = as.numeric(TimeLevs), minor_breaks = NULL)

    ## add labels
    if(missing(xlab)) {
        xlab <- 'Time'
    }
    if(missing(ylab)) {
        ylab <- 'Treatment'
    }
    plt <- plt + labs(x = xlab, y = ylab, title = title, subtitle = subtitle,
                      caption = caption)

    ## return
    plt
}
