R/pagination_helpers.R

Defines functions fetch_until fetch_all next_page total_pages current_page is_paginated headers

Documented in fetch_all fetch_until

headers <- function(response) {
  attr(response, "headers")
}

is_paginated <- function(response) {
  h <- headers(response)
  "x-pagination-current-page" %in% names(h)
}

current_page <- function(response) {
  h <- headers(response)
  as.numeric(h$`x-pagination-current-page`)
}

total_pages <- function(response) {
  h <- headers(response)
  as.numeric(h$`x-pagination-total-pages`)
}

next_page <- function(response) {
  n <- current_page(response) + 1
  if (n > total_pages(response)) {
    return(NULL)
  } else {
    return(n)
  }
}

#' Retrieve all results from a paginated endpoint
#'
#' @param fn The API function to be called.
#' @param ... Arguments passed to \code{fn}.
#'
#' @return A \code{list} with the concatenated results of each page of \code{fn}.
#' @export
#'
#' @family pagination
#'
#' @examples \dontrun{
#' columns <- fetch_all(tables_list_columns, id = 123)
#' column_names <- columns %>% purrr::map_chr("name")
#' }
fetch_all <- function(fn, ...) {
  fetch_until(fn, function(x) x == FALSE, ...)
}

#' Retrieve some results from a paginated endpoint
#'
#' \code{fetch_until} will retrieve paginated results until a condition is met.
#' This is useful when searching for a particular value or record.
#'
#' @param fn The API function to be called.
#' @param .until A function which returns a boolean value.
#' \code{.until} will be called with each item from the API response. When
#' \code{.until} returns \code{TRUE} iteration will stop and \code{fetch_until}
#' will return all responses accumulated so far.
#' @param ... Arguments passed to \code{fn}.
#'
#' @return A \code{list} with the concatenated results of each page of \code{fn}.
#' @export
#'
#' @family pagination
#'
#' @examples \dontrun{
#' columns <- fetch_until(tables_list_columns,
#'                        .until = function(x) x == "voterbase_id")
#' }
fetch_until <- function(fn, .until, ...) {
  args <- list(...)

  args$page_num <- 1
  args$limit <- NULL
  full_results <- list()

  repeat {
    res <- do.call(fn, args)
    full_results <- append(full_results, res)
    if (any(sapply(res, .until))) {
      break
    }

    args$page_num <- next_page(res)
    if (is.null(args$page_num)) {
      break
    }
  }

  full_results
}

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civis documentation built on July 2, 2020, 12:44 a.m.