#' Plot a jpeg image as a raster
#'
#' @param path a character representing the relative or absolute path to the image
#' @param add a logical, TRUE to add the image to an existing plot, FALSE creates a new plot
#' @param upscale a logical, TRUE upscales the resolution of the graphic by a factor of 3, FALSE
#' preserves the resolution
#' @return a rasterImage
#' @export
#' @importFrom jpeg readJPEG
#' @importFrom graphics rasterImage
#' @examples
#' img <- system.file("img","civilytics_logo.jpg",package="civilytics")
#' plot_jpeg(img)
plot_jpeg <- function(path, add=FALSE, upscale = TRUE)
{
  jpg = readJPEG(path, native = T) # read the file
  res = dim(jpg)[2:1] # get the resolution, [x, y]
  if (upscale){
    res <- res * 3
  }
  if (!add) # initialize an empty plot area if add==FALSE
    plot(1,1,xlim=c(1,res[1]),ylim=c(1,res[2]),asp=1,type='n',xaxs='i',yaxs='i',
         xaxt='n',yaxt='n',xlab='',ylab='',bty='n',  oma=c(0,0,1,1), mar=c(0,0,1,1)
    )
  rasterImage(jpg,1,1,res[1],res[2],interpolate=TRUE)
}


#' Plot a PNG file as a rasterGrob for inclusion in ggplot2
#'
#' @param filename a character with file path to a png file
#'
#' @return a plotted rasteGrob of a png image
#' @export
#' @importFrom png readPNG
#' @importFrom grid rasterGrob
get_png <- function(filename) {
  grid::rasterGrob(png::readPNG(filename), interpolate = TRUE)
}


#' Add a logo to a ggplot2 object
#'
#' @param plot a ggplot2 grob
#' @param logo a logo grob created by make_logo_grob()
#' @param margin_param a numeric specifying what margin to add or subtract to align the logo
#'
#' @return a grob with a logo attached to it ready to plot
#' @importFrom ggplot2 theme
#' @importFrom gridExtra arrangeGrob
#' @export
add_logo <- function(plot, logo, margin_param = NULL) {
  if(has_caption(plot)) {
    # convert the caption size to a negative number and on the "pt" scale
    # p1$theme$plot.caption$size * 1.1
    # Count the number of lines, which is this + 1
    # For each line, we can add a certain negative space to align the logo
    cap_lines <- measure_caption(plot)
    if (!is.null(margin_param)) {
      plot <- plot + theme(plot.margin = unit(c(7, 7, margin_param, 7), "pt"))
    } else {
      plot <- plot + theme(plot.margin = unit(c(7, 7, cap_lines * -52, 7), "pt"))
    }
  } else {
    plot <- plot + theme(plot.margin = unit(c(7, 7, -14, 7), "pt"))
  }

  arrangeGrob(plot, logo, heights = c(0.93, 0.1),
              padding = unit(0.1, "line"))
}

#' Measure a ggplot2 object caption
#'
#' @param gg a ggplot object
#'
#' @return a numeric value stating the number of lines to be added or subtracted to align a logo with
#' the caption
#' @importFrom stringr str_count
#' @export
#'
#' @examples
#' p1 <- ggplot2::qplot(mpg, wt, data = mtcars)
#' measure_caption(p1) # Should equal 1 since no caption is required
measure_caption <- function(gg) {
  if (has_caption(gg)) {
    stringr::str_count(gg$labels$caption, pattern = "\n") + 1
  } else {
    1
  }
}


#' Test whether a ggplot2 object has a caption
#'
#' @param gg a gg object from ggplot2
#'
#' @return a logical, TRUE if a caption exists and FALSE if it does not
#' @import ggplot2
#' @export
#'
#' @examples
#' p1 <- ggplot2::qplot(mpg, wt, data = mtcars)
#' has_caption(p1) # FALSE
has_caption <- function(gg) {
  any(names(gg$labels) == "caption")
}

#' Add a logo to a ggplot2 object
#'
#' @param plot_list a list containing ggplot2 objects
#' @param logo a grob containing the logo created with `make_logo_grob`
#' @param nrow an integer, default = 1, for the number of rows to align the plots in
#' @param widths an optional vector the same length as plot_list with the widths for each plot
#' @param margin_param a number giving the adjustment up or down to help manually align logo and captions
#'
#' @return a grid object
#' @note The resulting object needs to be drawn to the screen using grid.draw()
#' @importFrom gridExtra arrangeGrob
#' @importFrom ggplot2 theme
#' @importFrom grid grid.draw
#' @export
#'
#' @examples
#' library(ggplot2); library(grid)
#' tmp_plot <- ggplot(mtcars) + aes(x = hp, y = disp) + geom_point() + theme_civilytics()
#' tmp_logo <- make_logo_grob()
#' plot_and_logo <- add_logo(tmp_plot, tmp_logo)
#' grid.draw(plot_and_logo)
#' dev.off()
add_logo_ga <- function(plot_list, logo, nrow = 1, widths = NULL, margin_param = NULL) {
  # Change position of logo depending on if plot has a caption
  if (!is.null(margin_param)) {
    margin <- theme(plot.margin = unit(c(7, 7, margin_param, 7), "pt"))
  } else if (any(unlist(lapply(plot_list, has_caption)))) {
    cap_lines <- measure_caption(plot_list[[1]]) # measure caption in first plot
    margin <- theme(plot.margin = unit(c(7, 7, -7 * sqrt(cap_lines), 7), "pt"))
  } else {
    margin <- theme(plot.margin = unit(c(7, 7, 7, 7), "pt"))
  }
  if (nrow > 1) {
    len <- length(plot_list)
    plot_list[[len]] <- plot_list[[len]] + margin
  } else {
    plot_list <- lapply(plot_list, "+", margin)
  }

  if (nrow != 1) {
    hold <- arrangeGrob(grobs = plot_list, nrow = nrow, ncol = 1, widths = widths)
  } else {
    hold <- arrangeGrob(grobs = plot_list, nrow = 1, ncol = 2, widths = widths)
  }

  arrangeGrob(hold, logo, heights = c(0.93, .07))
}


#' Get a Civilytics Logo grob
#'
#' @return a gg object which contains the logo file stored as a Grob suitable for manipulating in
#' grid
#' @export
#' @import ggplot2
#' @examples
#' logo <- make_logo_grob()
#' class(logo) # gg
make_logo_grob <- function() {
  logo_grob <- ggplot(mapping = aes(x = 0:1, y = 1)) +
    theme_void() +
    annotation_custom(get_png(system.file("img", "civilytics_logo.png",
                                          package="civilytics")), xmin= 0.7, xmax = 1)
  logo_grob
}