# Font family name constants used as defaults in theme functions.
# These match the --cv-font-* CSS custom properties on www.civilytics.com.
CV_FONT_DISPLAY <- "Libre Franklin"  # headings / display text
CV_FONT_SANS    <- "Inter"           # axis text, legends, UI elements
CV_FONT_SERIF   <- "Source Serif 4"  # body prose / editorial long-form
CV_FONT_MONO    <- "JetBrains Mono"  # code, data tables, numeric callouts

# Mutable package state held in an environment so the binding itself stays
# locked (R locks all namespace bindings at load time) while the contents
# remain writable. See https://adv-r.hadley.nz/environments.html#environments-as-containers
.cv_state <- new.env(parent = emptyenv())
.cv_state$fonts_loaded <- FALSE

#' Load Civilytics brand fonts
#'
#' Downloads Inter, Libre Franklin, Source Serif 4 and JetBrains Mono from
#' Google Fonts via [sysfonts::font_add_google()], then calls
#' [showtext::showtext_auto()] so that all graphics devices render text with
#' those fonts. This is called automatically when the package loads; use this
#' function to retry if the initial load failed (e.g., the machine was offline
#' at load time).
#'
#' Subsequent calls within the same session are no-ops unless `force = TRUE`.
#'
#' @param force Logical. If `TRUE`, reload fonts even if they were already
#'   loaded in this session. Default `FALSE`.
#'
#' @return Invisibly returns `TRUE` if fonts were loaded, `FALSE` if skipped
#'   (already loaded and `force = FALSE`).
#' @export
#'
#' @examples
#' \dontrun{
#' civilytics_load_fonts()
#' }
civilytics_load_fonts <- function(force = FALSE) {
  if (.cv_state$fonts_loaded && !force) return(invisible(FALSE))

  sysfonts::font_add_google("Inter",          family = "Inter")
  sysfonts::font_add_google("Libre Franklin", family = "Libre Franklin")
  sysfonts::font_add_google("Source Serif 4", family = "Source Serif 4")
  sysfonts::font_add_google("JetBrains Mono", family = "JetBrains Mono")
  showtext::showtext_auto()

  .cv_state$fonts_loaded <- TRUE
  invisible(TRUE)
}

.onLoad <- function(libname, pkgname) {
  tryCatch(
    civilytics_load_fonts(),
    error = function(e) {
      # Store the failure so .onAttach can surface a message to the user.
      options(.civilytics_fonts_failed = TRUE)
    }
  )
}

.onAttach <- function(libname, pkgname) {
  if (isTRUE(getOption(".civilytics_fonts_failed"))) {
    packageStartupMessage(
      "[civilytics] Brand fonts (Inter, Libre Franklin, Source Serif 4, ",
      "JetBrains Mono) could not be loaded from Google Fonts. ",
      "Charts will fall back to system fonts. ",
      "Call civilytics_load_fonts() once you have an internet connection."
    )
  }
}