#' Sidebar layouts
#'
#' @description
#' Sidebar layouts place UI elements, like input controls or additional context,
#' next to the main content area which often holds output elements like plots or
#' tables.
#'
#' There are several page, navigation, and layout functions that allow you to
#' create a sidebar layout. In each case, you can create a collapsing sidebar
#' layout by providing a `sidebar()` object to the `sidebar` argument the
#' following functions.
#'
#' * [page_sidebar()] creates a "page-level" sidebar.
#' * [page_navbar()] creates a multi-panel app with an (optional, page-level)
#'   sidebar that is shown on every panel.
#' * `layout_sidebar()` creates a "floating" sidebar layout component which can
#'   be used inside any [page()] and/or [card()] context.
#' * [navset_card_tab()] and [navset_card_pill()] create multi-tab cards with a
#'   shared sidebar that is accessible from every panel.
#'
#' See [the Sidebars article](https://rstudio.github.io/bslib/articles/sidebars.html)
#' on the bslib website to learn more.
#'
#' @references Sidebar layouts are featured in a number of pages on the bslib
#'   website:
#'
#'   * [Sidebars](https://rstudio.github.io/bslib/articles/sidebars.html)
#'   * [Cards: Sidebars](https://rstudio.github.io/bslib/articles/cards/index.html#sidebars)
#'   * [Getting Started: Dashboards](https://rstudio.github.io/bslib/articles/dashboards/index.html)
#'
#' @param ... Unnamed arguments can be any valid child of an [htmltools
#'   tag][htmltools::tags] and named arguments become HTML attributes on
#'   returned UI element. In the case of `layout_sidebar()`, these arguments are
#'   passed to the main content tag (not the sidebar+main content container).
#' @param width A valid [CSS unit][htmltools::validateCssUnit] used for the
#'   width of the sidebar.
#' @param position Where the sidebar should appear relative to the main content.
#' @param open The initial state of the sidebar, choosing from the following
#'   options:
#'
#'   * `"desktop"`: The sidebar starts open on desktop screen, closed on mobile.
#'     This is default sidebar behavior.
#'   * `"open"` or `TRUE`: The sidebar starts open.
#'   * `"closed"` or `FALSE`: The sidebar starts closed.
#'   * `"always"` or `NA`: The sidebar is always open and cannot be closed.
#'
#'   Alternatively, you can use a list with `desktop` or `mobile` items to set
#'   the initial sidebar state independently for `desktop` and `mobile` screen
#'   sizes. In this case, `desktop` or `mobile` can use any of the above options
#'   except `"desktop"`, which is equivalent to
#'   `list(desktop = "open", mobile = "closed")`. You can also choose to place
#'   an always open sidebar above the main content on mobile devices by setting
#'   `mobile = "always-above"`.
#'
#'   In `sidebar_toggle()`, `open` indicates the desired state of the sidebar,
#'   where the default of `open = NULL` will cause the sidebar to be toggled
#'   open if closed or vice versa. Note that `sidebar_toggle()` can only open or
#'   close the sidebar, so it does not support the `"desktop"` and `"always"`
#'   options.
#' @param id A character string. Required if wanting to re-actively read (or
#'   update) the `collapsible` state in a Shiny app.
#' @param title A character title to be used as the sidebar title, which will be
#'   wrapped in a `<header>` element with class `sidebar-title`. You can also
#'   provide a custom [htmltools::tag()] for the title element, in which case
#'   you'll likely want to give this element `class = "sidebar-title"`.
#' @param bg,fg A background or foreground color. If only one of either is
#'   provided, an accessible contrasting color is provided for the opposite
#'   color, e.g. setting `bg` chooses an appropriate `fg` color.
#' @param class CSS classes for the sidebar container element, in addition to
#'   the fixed `.sidebar` class.
#' @param max_height_mobile A [CSS length unit][htmltools::validateCssUnit()]
#'   defining the maximum height of the horizontal sidebar when viewed on mobile
#'   devices. Only applies to always-open sidebars that use `open = "always"`,
#'   where by default the sidebar container is placed below the main content
#'   container on mobile devices.
#' @param gap A [CSS length unit][htmltools::validateCssUnit()] defining the
#'   vertical `gap` (i.e., spacing) between adjacent elements provided to `...`.
#' @param padding Padding within the sidebar itself. This can be a numeric
#'   vector (which will be interpreted as pixels) or a character vector with
#'   valid CSS lengths. `padding` may be one to four values. If one, then
#'   that value will be used for all four sides. If two, then the first value
#'   will be used for the top and bottom, while the second value will be used
#'   for left and right. If three, then the first will be used for top, the
#'   second will be left and right, and the third will be bottom. If four, then
#'   the values will be interpreted as top, right, bottom, and left
#'   respectively.
#'
#' @export
sidebar <- function(
  ...,
  width = 250,
  position = c("left", "right"),
  open = NULL,
  id = NULL,
  title = NULL,
  bg = NULL,
  fg = NULL,
  class = NULL,
  max_height_mobile = NULL,
  gap = NULL,
  padding = NULL
) {
  position <- rlang::arg_match(position)
  gap <- validateCssUnit(gap)
  padding <- validateCssPadding(padding)
  width <- validateCssUnit(width)
  max_height_mobile <- validateCssUnit(max_height_mobile)

  if (!is.null(open)) {
    open <- as_sidebar_open_on(open)
  }

  if (!is.null(id)) {
    if (length(id) != 1 || is.na(id) || !nzchar(id)) {
      rlang::abort(
        "`id` must be a non-empty, length-1 character string or `NULL`."
      )
    }

    # when user provides id, make the sidebar a shiny input to report its state
    class <- c("bslib-sidebar-input", class)
  }

  if (is.null(fg) && !is.null(bg)) {
    fg <- get_color_contrast(bg)
  }
  if (is.null(bg) && !is.null(fg)) {
    bg <- get_color_contrast(fg)
  }

  if (rlang::is_bare_character(title) || rlang::is_bare_numeric(title)) {
    title <- tags$header(title, class = "sidebar-title")
  }

  dots <- separate_arguments(...)

  res <- list2(
    id = id,
    title = title,
    class = class,
    gap = gap,
    padding = padding,
    open = open,
    position = position,
    width = width,
    max_height_mobile = max_height_mobile,
    color = list(bg = bg, fg = fg),
    attributes = dots$attribs,
    children = dots$children
  )

  class(res) <- c("bslib_sidebar", "sidebar", class(res))
  res
}

#' Render a sidebar as HTML tags
#'
#' Renders the sidebar element and collapse toggle elements for a [sidebar()] in
#' a [layout_sidebar()] context.
#'
#' @param x A [sidebar()] object.
#' @param ... Additional arguments passed to [htmltools::as.tags()].
#'
#' @importFrom htmltools as.tags
#' @keywords internal
#' @export
as.tags.bslib_sidebar <- function(x, ...) {
  if (is.null(open)) {
    open <- sidebar_open_on()
  }

  if (x$open$mobile == "always-above") {
    x$open$mobile <- "always"
  }

  is_always_open <- all(vapply(x$open, identical, logical(1), "always"))

  if (!is_always_open && is.null(x$id)) {
    # always provide an id for accessibility reasons when collapsible
    x$id <- paste0("bslib-sidebar-", p_randomInt(1000, 10000))
  }

  if (!is.null(x$max_height_mobile) && x$open$mobile != "always") {
    rlang::warn(
      'The `max_height_mobile` argument only applies to the sidebar when `open = "always"` on mobile.'
    )
    x$max_height_mobile <- NULL
  }

  is_starts_closed <- all(vapply(x$open, identical, logical(1), "closed"))
  is_starts_open <- all(vapply(x$open, identical, logical(1), "open"))

  hidden_initially <-
    if (is_always_open) FALSE else if (is_starts_open) FALSE else TRUE

  collapse_tag <-
    tags$button(
      class = "collapse-toggle",
      type = "button",
      title = "Toggle sidebar",
      "aria-expanded" = tolower(
        is_starts_open || identical(x$open$desktop, "open")
      ),
      "aria-controls" = x$id,
      collapse_icon()
    )

  sidebar_tag <- tags$aside(
    id = x$id,
    class = c("sidebar", x$class),
    hidden = if (hidden_initially) NA,
    tags$div(
      class = "sidebar-content bslib-gap-spacing",
      x$title,
      style = css(
        gap = x$gap,
        padding = x$padding
      ),
      !!!x$attributes,
      !!!x$children
    )
  )

  htmltools::tagList(sidebar_tag, collapse_tag)
}

as_sidebar_open_on <- function(open) {
  if (is.null(open)) return(NULL)

  if (rlang::is_list(open)) {
    unknown <- setdiff(names(open), c("desktop", "mobile"))
    if (length(unknown)) {
      rlang::warn(
        paste(
          "Ignoring unknown items in `open` options list:",
          paste0('"', unknown, '"', collapse = ", ")
        ),
      )
    }
    return(sidebar_open_on(open[["desktop"]], open[["mobile"]]))
  }

  if (length(open) == 1) {
    open <- sidebar_open_as_string(open, extra = "desktop", rlang::caller_env())
    if (identical(open, "desktop")) {
      return(sidebar_open_on("open", "closed"))
    }
    return(sidebar_open_on(open, open))
  }

  msg <- sprintf(
    "`open` must be a character string, a boolean, or a list with `desktop` and `mobile` items, not `%s`.",
    rlang::expr_text(open)
  )

  rlang::abort(
    c(
      msg,
      "i" = 'Character options include "open", "closed", "always" or "desktop".'
    ),
    call = rlang::caller_call()
  )
}

#' @param desktop,mobile The initial state of the sidebar on desktop or mobile
#'   screen sizes. Can be one of `"open"` (or `TRUE`), `"closed"` (or `FALSE`),
#'   or `"always"` (or `NA`). `mobile` also accepts `"always-above"`.
#' @noRd
sidebar_open_on <- function(
  desktop = "open",
  mobile = "closed"
) {
  desktop <- desktop %||% "open"
  mobile <- mobile %||% "closed"

  desktop <- sidebar_open_as_string(desktop)
  mobile <- sidebar_open_as_string(mobile, extra = "always-above")

  structure(
    list(desktop = desktop, mobile = mobile),
    class = "bslib_sidebar_open_options"
  )
}

sidebar_open_as_string <- function(
  open,
  extra = NULL,
  error_call = rlang::caller_env()
) {
  error_arg <- deparse(substitute(open))

  if (is.null(open)) return(NULL)
  if (identical(open, NA)) return("always")
  if (isTRUE(open)) return("open")
  if (isFALSE(open)) return("closed")

  rlang::arg_match(
    open,
    values = c("open", "closed", "always", extra),
    error_arg = error_arg,
    error_call = error_call
  )
}

#' @rdname sidebar
#' @param sidebar A [sidebar()] object.
#' @param fillable Whether or not the `main` content area should be considered a
#'   fillable (i.e., flexbox) container.
#' @param fill Whether or not to allow the layout container to grow/shrink to fit a
#'   fillable container with an opinionated height (e.g., `page_fillable()`).
#' @param border Whether or not to add a border.
#' @param border_radius Whether or not to add a border radius.
#' @param border_color The border color that is applied to the entire layout (if
#'   `border = TRUE`) and the color of the border between the sidebar and the
#'   main content area.
#' @inheritParams card
#' @inheritParams page_fillable
#'
#' @export
layout_sidebar <- function(
  ...,
  sidebar = NULL,
  fillable = TRUE,
  fill = TRUE,
  bg = NULL,
  fg = NULL,
  border = NULL,
  border_radius = NULL,
  border_color = NULL,
  padding = NULL,
  gap = NULL,
  height = NULL
) {
  if (!inherits(sidebar, "sidebar")) {
    sidebar <- sidebar(sidebar)
  }

  if (is.null(sidebar$open)) {
    sidebar$open <- sidebar_open_on()
  }

  if (!(is.null(border) || isTRUE(border) || isFALSE(border))) {
    abort("`border` must be `NULL`, `TRUE`, or `FALSE`")
  }
  if (
    !(is.null(border_radius) || isTRUE(border_radius) || isFALSE(border_radius))
  ) {
    abort("`border_radius` must be `NULL`, `TRUE`, or `FALSE`")
  }

  # main content area colors, if not provided ----
  if (is.null(fg) && !is.null(bg)) {
    fg <- get_color_contrast(bg)
  }
  if (is.null(bg) && !is.null(fg)) {
    bg <- get_color_contrast(fg)
  }

  main <- div(
    class = "main",
    class = if (fillable) "bslib-gap-spacing",
    style = css(
      padding = validateCssPadding(padding),
      gap = validateCssUnit(gap)
    ),
    ...
  )

  main <- bindFillRole(main, container = fillable)
  contents <- if (sidebar$open$mobile == "always-above") {
    list(as.tags(sidebar), main)
  } else {
    list(main, as.tags(sidebar))
  }

  right <- identical(sidebar$position, "right")

  res <- div(
    class = "bslib-sidebar-layout bslib-mb-spacing",
    class = if (right) "sidebar-right",
    class = if (identical(sidebar$open$desktop, "closed")) "sidebar-collapsed",
    `data-bslib-sidebar-init` = TRUE,
    `data-open-desktop` = sidebar$open$desktop,
    `data-open-mobile` = sidebar$open$mobile,
    `data-collapsible-mobile` = tolower(
      !sidebar$open$mobile %in% c("always", "always-above")
    ),
    `data-collapsible-desktop` = tolower(
      !identical(sidebar$open$desktop, "always")
    ),
    `data-bslib-sidebar-border` = if (!is.null(border)) tolower(border),
    `data-bslib-sidebar-border-radius` = if (!is.null(border_radius))
      tolower(border_radius),
    style = css(
      "--_sidebar-width" = sidebar$width,
      "--_sidebar-bg" = sidebar$color$bg,
      "--_sidebar-fg" = sidebar$color$fg,
      "--_main-fg" = fg,
      "--_main-bg" = bg,
      "--bs-card-border-color" = border_color,
      height = validateCssUnit(height),
      "--_mobile-max-height" = sidebar$max_height_mobile
    ),
    !!!contents,
    sidebar_init_js(),
    component_dependencies()
  )

  res <- bindFillRole(res, item = fill)

  res <- as.card_item(res)

  as_fragment(
    tag_require(res, version = 5, caller = "layout_sidebar()")
  )
}

#' @describeIn sidebar Toggle a `sidebar()` state during an active Shiny user
#'   session.
#' @param session A Shiny session object (the default should almost always be
#'   used).
#' @export
toggle_sidebar <- function(id, open = NULL, session = get_current_session()) {
  method <- sidebar_open_as_string(open %||% "toggle", "toggle")

  if (identical(method, "always")) {
    abort('`open = "always"` is not supported by `sidebar_toggle()`.')
  }

  force(id)
  callback <- function() {
    session$sendInputMessage(id, list(method = method))
  }
  session$onFlush(callback, once = TRUE)
}

#' @rdname sidebar
#' @usage NULL
#' @export
sidebar_toggle <- toggle_sidebar

collapse_icon <- function() {
  if (!is_installed("bsicons")) {
    icon <- "<svg xmlns=\"http://www.w3.org/2000/svg\" viewBox=\"0 0 16 16\" class=\"bi bi-chevron-left collapse-icon\" style=\"fill:currentColor;\" aria-hidden=\"true\" role=\"img\" ><path fill-rule=\"evenodd\" d=\"M11.354 1.646a.5.5 0 0 1 0 .708L5.707 8l5.647 5.646a.5.5 0 0 1-.708.708l-6-6a.5.5 0 0 1 0-.708l6-6a.5.5 0 0 1 .708 0z\"></path></svg>"
    return(HTML(icon))
  }
  bsicons::bs_icon("chevron-left", class = "collapse-icon", size = NULL)
}

sidebar_init_js <- function() {
  # Note: if we want to avoid inline `<script>` tags in the future for
  # initialization code, we might be able to do so by turning the sidebar layout
  # container into a web component
  tags$script(
    `data-bslib-sidebar-init` = NA,
    HTML("bslib.Sidebar.initCollapsibleAll()")
  )
}