#===== Implementation utility =====


#'get_class_from_xpath
#'@description Gets r2ogs6 class name from an xpath-like expression
#'@param xpath string: An xpath expression. Works for path-like xpaths only
#'@return string: The class name.
get_class_from_xpath <- function(xpath){

  assertthat::assert_that(assertthat::is.string(xpath))

  xpaths_for_classes <- xpaths_for_classes

  for(i in seq_len(length(xpaths_for_classes))){
    if((assertthat::is.string(xpaths_for_classes[[i]]) &&
        xpaths_for_classes[[i]] == xpath) ||
       (length(xpaths_for_classes[[i]]) > 1 &&
        xpath %in% xpaths_for_classes[[i]])){
      return(names(xpaths_for_classes)[[i]])
    }
  }

  return(invisible(NULL))
}


#'get_tag_from_class
#'@description Utility function, returns the tag name of a r2ogs6 class
#'@param class_name string: The name of a r2ogs6 class
#'@return string: The tag name corresponding to `class_name`
get_tag_from_class <- function(class_name) {

  assertthat::assert_that(assertthat::is.string(class_name))

  xpaths_for_classes <- xpaths_for_classes

  xpath <- xpaths_for_classes[[class_name]]
  split_xpath <- unlist(strsplit(xpath[[1]], "/", fixed = TRUE))
  tag_name <- split_xpath[[length(split_xpath)]]

  return(invisible(tag_name))
}


#'get_tag_from_xpath
#'@description Gets the XML tag name from an xpath expression
#'@param xpath string: An xpath expression. Works for path-like xpaths only
#'@return string: The XML tag name.
get_tag_from_xpath <- function(xpath){

  xpath_split <- unlist(strsplit(xpath, "/", fixed = TRUE))
  tag_name <- xpath_split[[length(xpath_split)]]

  return(tag_name)
}


#'prj_top_level_tags
#'@description Gets top level .prj tags along with info if they are required.
#'@return list: List of lists.
prj_top_level_tags <- function(){

  prj_reduxml <- system.file("extdata/xml_redux/", "prj_redu.xml",
                             package = "r2ogs6")

  xml_doc <- xml2::read_xml(prj_reduxml)

  prj_tag_info <- lapply(xml2::xml_children(xml_doc), function(x){
      list(tag_name = xml2::xml_name(x),
           is_required = as.logical(xml2::xml_attrs(x)[["required"]]))
  })

  return(prj_tag_info)
}


#'prj_top_level_classes
#'@description Returns named character vector of `OGS6` top level .prj tags
#' (names) represented by r2ogs6 classes along with their class names (values).
#'@return character
prj_top_level_classes <- function(){

  xpaths_for_classes <- xpaths_for_classes

  flattened_xpaths <- unlist(xpaths_for_classes)
  names(flattened_xpaths) <- NULL

  prj_components <- character()
  seen <- character()

  for(i in seq_len(length(flattened_xpaths))){

    split_xpath <-
      unlist(strsplit(flattened_xpaths[[i]], "/", fixed = TRUE))

    if(!split_xpath[[1]] %in% seen){
      if(!is.null(get_class_from_xpath(split_xpath[[1]]))){
        prj_components <- c(prj_components,
                            get_class_from_xpath(split_xpath[[1]]))

      }else{
        xpath <- paste(split_xpath[[1]], split_xpath[[2]], sep = "/")
        prj_components <- c(prj_components,
                            get_class_from_xpath(xpath))
      }

      names(prj_components)[[length(prj_components)]] <- split_xpath[[1]]
      seen <- c(seen, split_xpath[[1]])
    }
  }

  return(prj_components)
}


#===== Coercion utility =====


#'coerce_string_to_numeric
#'@description If an object is of type string, coerces it to a numeric type
#'@param obj object: Any object
#'@return numeric if 'obj' was a string, else unchanged 'obj'
coerce_string_to_numeric <- function(obj){

  if(assertthat::is.string(obj)){
    obj <- trimws(gsub("\r?\n|\r|\\s+", " ", obj))
    obj <- as.double(unlist(strsplit(obj, " ")))
  }

  return(obj)
}



#'coerce_names
#'@description Validator function for a parameter vector
#'@param vector vector: Vector of parameters
#'@param names character: How the vector elements will be named as
#' per default
#'@return vector: Named vector where the names correspond to `names`
coerce_names <- function(vector, names) {

  assertthat::assert_that(is.vector(vector))
  assertthat::assert_that(is.character(names))
  assertthat::assert_that(length(vector) == length(names))

  sorted_param_names <- sort(names(vector))
  sorted_names <- sort(names)

  if(is.null(names(vector)) ||
     (!is.null(names(vector)) &&
      any(sorted_param_names != sorted_names))){

    names(vector) <- names

    message(paste0(
      "Renaming elements of ",
      deparse(quote(vector)),
      " to fit their default names: '",
      paste(names, collapse = "', '"),
      "'"))
  }

  return(invisible(vector))
}


#'is_null_or_coerce_names
#'@description Validator function for a parameter list or vector or NULL
#'@param obj A list (or vector) of parameters
#'@param names How the list elements will be named as per default
is_null_or_coerce_names <- function(obj, names){

  if(!is.null(obj)){
    obj <- coerce_names(obj, names)
  }

  return(invisible(obj))
}


#'clean_imported_list
#'@description Cleans an imported list because sometimes strings containing
#' only newline characters and spaces get imported in
#'@param list list: A list
clean_imported_list <- function(list){

  assertthat::assert_that(is.list(list))

  cleaned_list <- list()

  for(i in seq_len(length(list))){
    if(assertthat::is.string(list[[i]]) &&
       stringr::str_remove_all(list[[i]], "[\n|[:space:]]") == ""){
      next
    }
    cleaned_list <- c(cleaned_list, list(list[[i]]))
    names(cleaned_list)[[length(cleaned_list)]] <- names(list)[[i]]
  }

  return(invisible(cleaned_list))
}


#'as_dir_path
#'@description Checks if a given path ends on '/'
#'@param path string: A path
as_dir_path <- function(path){

  assertthat::assert_that(assertthat::is.string(path))

  path <- gsub("\\", "/", path, fixed = TRUE)

  nchar <- nchar(path)

  if(substring(path, nchar, nchar) != "/"){
    path <- paste0(path, "/")
  }

  return(invisible(path))
}


#===== Validation utility =====


#'are_numbers
#'@description Checks if objects are numbers
#'@param ... Ellipsis
are_numbers <- function(...){

  lapply(list(...), function(x){
    assertthat::assert_that(assertthat::is.number(x))
  })

  return(invisible(TRUE))
}


#'are_null_or_numbers
#'@description Checks if objects are either NULL or numbers
#'@param ... Ellipsis
are_null_or_numbers <- function(...){

  lapply(list(...), function(x){
    if(!is.null(x)){
      assertthat::assert_that(assertthat::is.number(x))
    }
  })

  return(invisible(TRUE))
}


#'are_numeric
#'@description Checks if objects are numeric
#'@param ... Ellipsis
are_numeric <- function(...){

  lapply(list(...), function(x){
    assertthat::assert_that(is.numeric(x))
  })

  return(invisible(TRUE))
}


#'are_null_or_numeric
#'@description Checks if objects are either NULL or numeric
#'@param ... Ellipsis
are_null_or_numeric <- function(...){

  lapply(list(...), function(x){
    if(!is.null(x)){
      assertthat::assert_that(is.numeric(x))
    }
  })

  return(invisible(TRUE))
}


#'are_strings
#'@description Checks if objects are strings
#'@param ... Ellipsis
are_strings <- function(...){

  lapply(list(...), function(x){
    assertthat::assert_that(assertthat::is.string(x))
  })

  return(invisible(TRUE))
}


#'are_null_or_strings
#'@description Checks if objects are either NULL or strings
#'@param ... Ellipsis
are_null_or_strings <- function(...){

  lapply(list(...), function(x){
    if(!is.null(x)){
      assertthat::assert_that(assertthat::is.string(x))
    }
  })

  return(invisible(TRUE))
}


#'are_string_flags
#'@description Checks if objects are strings reading either "true" or "false"
#'@param ... Ellipsis
are_string_flags <- function(...){

  lapply(list(...), function(x){
    assertthat::assert_that(assertthat::is.string(x))
    assertthat::assert_that(x %in% c("true", "false"))
  })

  return(invisible(TRUE))
}


#'are_null_or_string_flags
#'@description Checks if objects are either NULL or strings reading either
#' "true" or "false"
#'@param ... Ellipsis
are_null_or_string_flags <- function(...){

  lapply(list(...), function(x){
    if(!is.null(x)){
      are_string_flags(x)
    }
  })

  return(invisible(TRUE))
}


#'is_wrapper_list
#'@description Checks if a list consists only of elements of class
#' `element_class`
#'@param list list: List to check
#'@param element_class string: Class each element of `list` should have
is_wrapper_list <- function(list, element_class) {

  assertthat::assert_that(is.list(list))

  lapply(list, function(x){
    assertthat::assert_that(any(grepl(element_class, class(x), fixed = TRUE)))
  })

  return(invisible(TRUE))
}


#'is_null_or_wrapper_list
#'@description Checks if an object is either NULL or a list of elements
#' of class `element_class`
#'@param obj list | NULL: Object to check
#'@param element_class string: Class each element of `obj` should have
is_null_or_wrapper_list <- function(obj, element_class) {

  if(!is.null(obj)){
    assertthat::assert_that(is.list(obj))

    lapply(obj, function(x){
      assertthat::assert_that(any(grepl(element_class, class(x), fixed = TRUE)))
    })
  }

  return(invisible(TRUE))
}


#'is_null_or_has_class
#'@description Checks if an object is either null or a class object of class
#' 'class_name'
#'@param obj The object to check
#'@param class_name The name of the expected class
is_null_or_has_class <- function(obj, class_name){

  if(!is.null(obj)){
      assertthat::assert_that(class(obj) == class_name)
  }

  return(invisible(TRUE))
}