#' @include logging.R
setGeneric("textMetadata", function(kco, ...) standardGeneric("textMetadata"))

#' Retrieve metadata for a text, identified by its sigle (id)
#'
#' @aliases textMetadata
#'
#' @description
#' Retrieves metadata for a text, identified by its sigle (id) using the corresponding KorAP API
#' (see [Kustvakt Wiki](https://github.com/KorAP/Kustvakt/wiki/Service:-Metadata-Retrieval)).
#' To retrieve the metadata for every text in a virtual corpus, use [corpusQuery()]
#' with `<base/s=t>` as query, instead.
#'
#'
#' @param kco [KorAPConnection()] object (obtained e.g. from `KorAPConnection()`)
#' @param textSigle unique text id (concatenation of corpus, document and text ids, separated by `/`, e.g. ) or vector thereof
#' @param verbose logical. If `TRUE`, additional diagnostics are printed. Defaults to `kco@verbose`.
#' @param cacheAs path to an RDS file to keep the result in. If the file exists and records the same call, it is read back instead of contacting the server; otherwise the query is run and its result stored there. Unlike the connection's `cache`, this file belongs to the caller, which is what keeps an analysis reproducible once the corpus has grown or the scores have changed. Defaults to \code{NULL} (no file).
#'
#' @return Tibble with columns for each metadata property. In case of errors, such as non-existing texts/sigles, the tibble will also contain a column called `errors`.
#' If there are metadata columns you cannot make sense of, please ignore them. The function simply returns all the metadata it gets from the server.
#'
#' @importFrom urltools url_encode
#' @importFrom dplyr across bind_rows relocate mutate where
#' @importFrom tibble as_tibble
#' @importFrom tidyr pivot_wider
#'
#' @examples
#' \dontrun{
#' KorAPConnection() |> textMetadata(c("WUD17/A97/08542", "WUD17/B96/57558", "WUD17/A97/08541"))
#' }
#'
#' @export
setMethod(
  "textMetadata", "KorAPConnection",
  function(kco, textSigle, verbose = kco@verbose, cacheAs = NULL) {
    cacheRecord <- NULL
    if (!is.null(cacheAs)) {
      cacheAs <- cacheAsFileName(cacheAs)
      cacheRecord <- cacheAsRecord(environment(), NULL, kco)
      cached <- readCacheAs(cacheAs, kco, cacheRecord, "text metadata")
      if (!is.null(cached)) {
        return(cached)
      }
    }

    # https://stackoverflow.com/questions/8096313/no-visible-binding-for-global-variable-note-in-r-cmd-check
    key <- 0
    metadata <- if (length(textSigle) > 1) {
      do.call(bind_rows, Map(function(atomicSigle) {
        textMetadata(kco, atomicSigle)
      }, textSigle))
    } else {
      url <-
        paste0(
          kco@apiUrl, "corpus/",
          URLencode(enc2utf8(textSigle), reserved = TRUE)
        )
      log_info(verbose, "Getting metadata for ", textSigle, sep = "")
      res <- apiCall(kco, url)
      log_info(verbose, ifelse(is.null(res) || "errors" %in% names(res), " [error]\n", "\n"))

      if (is.null(res)) {
        res <- tibble(errors = "API request failed")
      } else {
        if ("document" %in% names(res) & "fields" %in% names(res$document) && length(res$document$fields) > 0) {
          res <- as_tibble(res$document$fields) %>%
            dplyr::mutate(across(where(is.list), ~ purrr::map(.x, ~ if (length(.x) < 2) unlist(.x) else paste(.x, collapse = "\\t")))) %>%
            select(key, value) %>%
            tidyr::pivot_wider(names_from = key, values_from = value, names_repair = "unique") %>%
            mutate(
              textSigle = as.character(textSigle),
              requestUrl = url,
              webUIRequestUrl = paste0(kco@KorAPUrl, sprintf('?q=<base/s=t>&cq=textSigle+%%3D+"%s"', url_encode(enc2utf8(textSigle))))
            ) %>%
            mutate(across(everything(), as.character)) %>%
            relocate(textSigle)
        } else {
          res <- lapply(res, function(x) paste0(x, collapse = "\\t")) # flatten list
          res <- as_tibble(res) %>%
            head(n = 1) %>%
            mutate(
              requestUrl = url,
              textSigle = textSigle,
              webUIRequestUrl = paste0(kco@KorAPUrl, sprintf('?q=<base/s=t>&cq=textSigle+%%3D+"%s"', url_encode(enc2utf8(textSigle))))
            ) %>%
            relocate(textSigle)
        }
      }
      res
    }

    if (!is.null(cacheAs)) {
      writeCacheAs(cacheAs, kco, cacheRecord, "text metadata", metadata)
    }
    metadata
  }
)