#' @import stats

createUniqueId <- function(bytes) {
  paste(as.hexmode(sample(256, bytes) - 1), collapse = "")
}

is_windows <- function() {
  identical(.Platform$OS.type, "windows")
}

is_osx <- function() {
  Sys.info()["sysname"] == "Darwin"
}

# determine the output file for a pandoc conversion
pandoc_output_file <- function(input, pandoc_options) {
  to <- pandoc_options$to
  if (!is.null(pandoc_options$ext))
    ext <- pandoc_options$ext
  else if (to %in% c("latex", "beamer"))
    ext <- ".pdf"
  else if (to %in% c("html", "html4", "html5", "s5", "slidy",
                     "slideous", "dzslides", "revealjs"))
    ext <- ".html"
  else if (grepl("^markdown", to)) {
    if (!identical(tolower(tools::file_ext(input)), "md"))
      ext <- ".md"
    else {
      ext <- paste(".", strsplit(to, "[\\+\\-]")[[1]][[1]], sep = "")
    }
  }
  else
    ext <- paste(".", to, sep = "")
  output <- paste(tools::file_path_sans_ext(input), ext, sep = "")
  basename(output)
}


rmarkdown_system_file <- function(file) {
  system.file(file, package = "rmarkdown")
}


#' @rdname rmarkdown_format
#' @export
from_rmarkdown <- function(implicit_figures = TRUE, extensions = NULL) {

  # paste extensions together and remove whitespace
  extensions <- paste0(extensions, collapse = "")
  extensions <- gsub(" ", "", extensions)

  # exclude implicit figures unless the user has added them back
  if (!implicit_figures && !grepl("implicit_figures", extensions))
    extensions <- paste0("-implicit_figures", extensions)

  rmarkdown_format(extensions)
}

is_null_or_string <- function(text) {
  is.null(text) || (is.character(text) && (length(text) == 1))
}

read_lines_utf8 <- function(file, encoding) {

  # read the file
  lines <- readLines(file, warn = FALSE)

  # convert to utf8
  to_utf8(lines, encoding)
}


to_utf8 <- function(x, encoding) {
  # normalize encoding to iconv compatible form
  if (identical(encoding, "native.enc"))
    encoding <- ""

  # convert to utf8
  if (!identical(encoding, "UTF-8"))
    iconv(x, from = encoding, to = "UTF-8")
  else
    mark_utf8(x)
}

# mark the encoding of character vectors as UTF-8
mark_utf8 <- function(x) {
  if (is.character(x)) {
    Encoding(x) <- 'UTF-8'
    return(x)
  }
  if (!is.list(x)) return(x)
  attrs <- attributes(x)
  res <- lapply(x, mark_utf8)
  attributes(res) <- attrs
  names(res) <- mark_utf8(names(res))
  res
}

# the yaml UTF-8 bug has been fixed https://github.com/viking/r-yaml/issues/6
# but yaml >= 2.1.14 Win/Mac binaries are not available for R < 3.2.0, so we
# still need the mark_utf8 trick
#' @importFrom utils packageVersion
yaml_load_utf8 <- function(string, ...) {
  string <- paste(string, collapse = '\n')
  if (packageVersion('yaml') >= '2.1.14') {
    yaml::yaml.load(string, ...)
  } else {
    mark_utf8(yaml::yaml.load(enc2utf8(string), ...))
  }
}

yaml_load_file_utf8 <- function(input, ...) {
  yaml_load_utf8(readLines(input, encoding = 'UTF-8'), ...)
}

file_name_without_shell_chars <- function(file) {
  name <- gsub(.shell_chars_regex, '_', basename(file))
  dir <- dirname(file)
  if (nzchar(dir) && !identical(dir, "."))
    file.path(dir, name)
  else
    name
}

tmpfile_pattern <- "rmarkdown-str"

# return a string as a tempfile
as_tmpfile <- function(str) {
  if (length(str) > 0) {
    str_tmpfile <- tempfile(tmpfile_pattern, fileext = ".html")
    writeLines(str, str_tmpfile, useBytes =  TRUE)
    str_tmpfile
  } else {
    NULL
  }
}

# temp files created by as_tmpfile() cannot be immediately removed because they
# are needed later by the pandoc conversion; we have to clean up the temp files
# that have the pattern specified in `tmpfile_pattern` when render() exits
clean_tmpfiles <- function() {
  unlink(list.files(
    tempdir(), sprintf("^%s[0-9a-f]+[.]html$", tmpfile_pattern), full.names = TRUE
  ))
}

dir_exists <- function(x) {
  utils::file_test('-d', x)
}

file_with_ext <- function(file, ext) {
  paste(tools::file_path_sans_ext(file), ".", ext, sep = "")
}


file_with_meta_ext <- function(file, meta_ext, ext = tools::file_ext(file)) {
  paste(tools::file_path_sans_ext(file),
        ".", meta_ext, ".", ext, sep = "")
}

knitr_files_dir <- function(file) {
  paste(tools::file_path_sans_ext(file), "_files", sep = "")
}

knitr_root_cache_dir <- function(file) {
  paste(tools::file_path_sans_ext(file), "_cache", sep = "")
}

knitr_cache_dir <- function(file, pandoc_to) {
  paste(tools::file_path_sans_ext(file), "_cache/", pandoc_to, "/", sep = "")
}

get_knitr_hook_list <- function(hook_names = NULL) {
  if (is.null(hook_names))
    hook_names <- c("knit_hooks", "opts_chunk", "opts_hooks", "opts_knit")
  knitr_ns <- asNamespace("knitr")
  hook_list <- lapply(hook_names, function(hook_name) {
    hooks <- get(hook_name, envir = knitr_ns, inherits = FALSE)
    hooks$get()
  })
  names(hook_list) <- hook_names
  hook_list
}

set_knitr_hook_list <- function(hook_list) {
  knitr_ns <- asNamespace("knitr")
  enumerate(hook_list, function(hook_name, hook_value) {
    hook <- get(hook_name, envir = knitr_ns, inherits = FALSE)
    hook$set(hook_value)
  })
}

highlighters <- function() {
  c("default",
    "tango",
    "pygments",
    "kate",
    "monochrome",
    "espresso",
    "zenburn",
    "haddock")
}

merge_lists <- function(base_list, overlay_list, recursive = TRUE) {
  if (length(base_list) == 0)
    overlay_list
  else if (length(overlay_list) == 0)
    base_list
  else {
    merged_list <- base_list
    for (name in names(overlay_list)) {
      base <- base_list[[name]]
      overlay <- overlay_list[[name]]
      if (is.list(base) && is.list(overlay) && recursive)
        merged_list[[name]] <- merge_lists(base, overlay)
      else {
        merged_list[[name]] <- NULL
        merged_list <- append(merged_list,
                              overlay_list[which(names(overlay_list) %in% name)])
      }
    }
    merged_list
  }
}

strip_white <- function(x)
{
  if (!length(x))
    return(x)
  while (is_blank(x[1])) {
    x = x[-1]
    if (!length(x))
      return(x)
  }
  while (is_blank(x[(n <- length(x))])) {
    x = x[-n]
    if (n < 2)
      return(x)
  }
  x
}

is_blank <- function(x)
{
  if (length(x))
    all(grepl("^\\s*$", x))
  else TRUE
}

trim_trailing_ws <- function(x) {
  sub("\\s+$", "", x)
}


# Find common base directory, throw error if it doesn't exist
base_dir <- function(x) {
  abs <- vapply(x, tools::file_path_as_absolute, character(1))

  base <- unique(dirname(abs))
  if (length(base) > 1) {
    stop("Input files not all in same directory, please supply explicit wd",
      call. = FALSE)
  }

  base
}

move_dir <- function(from, to) {
  dir.create(dirname(to), showWarnings = FALSE)
  file.rename(from, to)
}

# Check if two paths are the same after being normalized
same_path <- function(path1, path2, ...) {
  if (length(path1) * length(path2) != 1)
    stop('The two paths must be both of length 1')
  normalize_path(path1, ...) == normalize_path(path2, ...)
}

# Regular expression representing characters likely to be considered special by
# the shell (require quoting/escaping)
.shell_chars_regex <- '[ <>()|\\:&;#?*\']'

# Find a program within the PATH. On OSX we need to explictly call
# /usr/bin/which with a forwarded PATH since OSX Yosemite strips
# the PATH from the environment of child processes
find_program <- function(program) {
  if (is_osx()) {
    res <- suppressWarnings({
      # Quote the path (so it can contain spaces, etc.) and escape any quotes
      # and escapes in the path itself
      sanitized_path <- gsub("\\", "\\\\", Sys.getenv("PATH"), fixed = TRUE)
      sanitized_path <- gsub("\"", "\\\"", sanitized_path, fixed = TRUE)
      system(paste0("PATH=\"", sanitized_path, "\" /usr/bin/which ", program),
             intern = TRUE)
    })
    if (length(res) == 0)
      ""
    else
      res
  } else {
    Sys.which(program)
  }
}

# given a string, escape the regex metacharacters it contains:
# regex metas are these,
#   . \ | ( ) [ { ^ $ * + ?
# as defined here:
#   http://stat.ethz.ch/R-manual/R-devel/library/base/html/regex.html
escape_regex_metas <- function(in_str) {
  gsub("([.\\|()[{^$+?])", "\\\\\\1", in_str)
}

# call latexmk to compile tex to PDF; if not available, use a simple emulation
latexmk <- function(file, engine, biblatex = FALSE) {
  if (requireNamespace('tinytex', quietly = TRUE)) {
    return(tinytex::latexmk(file, engine, if (biblatex) 'biber' else 'bibtex'))
  }
  message('You are recommended to install the tinytex package to build PDF.', call. = FALSE)
  if (!grepl('[.]tex$', file))
    stop("The input file '", file, "' does not appear to be a LaTeX document")
  engine <- find_latex_engine(engine)
  latexmk_path <- find_program('latexmk')
  if (latexmk_path == '') {
    # latexmk not found
    latexmk_emu(file, engine, biblatex)
  } else if (find_program('perl') != '' && latexmk_installed(latexmk_path)) {
    system2_quiet(latexmk_path, c(
      '-pdf -latexoption=-halt-on-error -interaction=batchmode',
      paste0('-pdflatex=', shQuote(engine)), shQuote(file)
    ), error = {
      check_latexmk_version(latexmk_path)
      show_latex_error(file)
    })
    system2(latexmk_path, '-c', stdout = FALSE)  # clean up nonessential files
  } else {
    latexmk_emu(file, engine, biblatex)
  }
}

# a quick and dirty version of latexmk (should work reasonably well unless the
# LaTeX document is extremely complicated)
latexmk_emu <- function(file, engine, biblatex = FALSE) {
  owd <- setwd(dirname(file))
  on.exit(setwd(owd), add = TRUE)
  # only use basename because bibtex may not work with full path
  file <- basename(file)

  file_with_same_base <- function(file) {
    files <- list.files()
    files <- files[utils::file_test('-f', files)]
    base <- tools::file_path_sans_ext(file)
    normalizePath(files[tools::file_path_sans_ext(files) == base])
  }
  # clean up aux files from LaTeX compilation
  files1 <- file_with_same_base(file)
  keep_log <- FALSE
  on.exit(add = TRUE, {
    files2 <- file_with_same_base(file)
    files3 <- setdiff(files2, files1)
    aux <- c(
      'aux', 'log', 'bbl', 'blg', 'fls', 'out', 'lof', 'lot', 'idx', 'toc',
      'nav', 'snm', 'vrb', 'ilg', 'ind'
    )
    if (keep_log) aux <- setdiff(aux, 'log')
    unlink(files3[tools::file_ext(files3) %in% aux])
  })

  fileq <- shQuote(file)
  run_engine <- function() {
    system2_quiet(engine, c('-halt-on-error -interaction=batchmode', fileq), error = {
      keep_log <<- TRUE
      show_latex_error(file)
    })
  }
  run_engine()
  # generate index
  idx <- sub('[.]tex$', '.idx', file)
  if (file.exists(idx)) {
    system2_quiet(find_latex_engine('makeindex'), shQuote(idx), error = {
      stop("Failed to build the index via makeindex", call. = FALSE)
    })
  }
  # generate bibliography
  if (biblatex) {
    aux_ext <- '.bcf'
    bib_engine <- 'biber'
  } else {
    aux_ext <- '.aux'
    bib_engine <- 'bibtex'
  }
  aux <- sub('[.]tex$', aux_ext, file)
  if (file.exists(aux)) {
    if (biblatex || require_bibtex(aux))
      system2_quiet(find_latex_engine(bib_engine), shQuote(aux), error = {
        stop("Failed to build the bibliography via ", bib_engine, call. = FALSE)
      })
  }
  run_engine()
  run_engine()
}

require_bibtex <- function(aux) {
  x <- readLines(aux)
  r <- length(grep('^\\\\citation\\{', x)) && length(grep('^\\\\bibdata\\{', x)) &&
    length(grep('^\\\\bibstyle\\{', x))
  if (r && is_windows()) tweak_aux(aux, x)
  r
}

# remove the .bib extension in \bibdata{} in the .aux file, because bibtex on
# Windows requires no .bib extension (sigh)
tweak_aux <- function(aux, x = readLines(aux)) {
  r <- '^\\\\bibdata\\{.+\\}\\s*$'
  if (length(i <- grep(r, x)) == 0) return()
  x[i] = gsub('[.]bib([,}])', '\\1', x[i])
  writeLines(x, aux)
}

system2_quiet <- function(..., error = NULL) {
  # run the command quietly if possible
  res <- system2(..., stdout = FALSE, stderr = FALSE)
  # if failed, use the normal mode
  if (res != 0) res <- system2(...)
  # if still fails, run the error callback
  if (res != 0) error  # lazy evaluation
  invisible(res)
}

# parse the LaTeX log and show error messages
show_latex_error <- function(file) {
  logfile <- file_with_ext(file, 'log')
  e <- c('Failed to compile ', file, '.')
  if (!file.exists(logfile)) stop(e, call. = FALSE)
  x <- readLines(logfile, warn = FALSE)
  b <- grep('^\\s*$', x)  # blank lines
  m <- NULL
  for (i in grep('^! ', x)) {
    # ignore the last error message about the fatal error
    if (grepl('==> Fatal error occurred', x[i], fixed = TRUE)) next
    n <- b[b > i]
    n <- if (length(n) == 0) i else min(n) - 1L
    m <- c(m, x[i:n], '')
  }
  if (length(m)) {
    message(paste(m, collapse = '\n'))
    stop(e, ' See ', logfile, ' for more info.', call. = FALSE)
  }
}

# check if latexmk was correctly installed; see more info at
# https://github.com/rstudio/bookdown/issues/121
latexmk_installed <- function(latexmk_path) {
  if (system2_quiet(latexmk_path, '-v') == 0) return(TRUE)
  warning('The LaTeX package latexmk was not correctly installed.', call. = FALSE)
  if (!is_windows()) return(FALSE)
  shell('latexmk -v')  # hopefully MiKTeX can fix it automatically
  system2_quiet(latexmk_path, '-v') == 0
}

# check the version of latexmk
check_latexmk_version <- function(latexmk_path = find_program('latexmk')) {
  out <- system2(latexmk_path, '-v', stdout = TRUE)
  reg <- '^.*Version (\\d+[.]\\d+).*$'
  out <- grep(reg, out, value = TRUE)
  if (length(out) == 0) return()
  ver <- as.numeric_version(gsub(reg, '\\1', out[1]))
  if (ver >= '4.43') return()
  system2(latexmk_path, '-v')
  warning(
    'Your latexmk version seems to be too low. ',
    'You may need to update the latexmk package or your LaTeX distribution.',
    call. = FALSE
  )
}

n_bytes <- function(string) {
  nchar(string, type = "bytes")
}

starts_with_bytes <- function(string, bytes) {
  Encoding(string) <- Encoding(bytes) <- "bytes"
  if (n_bytes(bytes) > n_bytes(string))
    return(FALSE)
  substring(string, 1, n_bytes(bytes)) == bytes
}

ends_with_bytes <- function(string, bytes) {
  Encoding(string) <- Encoding(bytes) <- "bytes"
  if (n_bytes(bytes) > n_bytes(string))
    return(FALSE)
  substring(string, n_bytes(string) - n_bytes(bytes) + 1, n_bytes(string)) == bytes
}

base64_encode_object <- function(object) {
  object <- rapply(object, unclass, how = "list")
  json <- charToRaw(jsonlite::toJSON(object, auto_unbox = TRUE))
  base64enc::base64encode(json)
}

base64_decode_object <- function(encoded) {
  json <- rawToChar(base64enc::base64decode(encoded))
  jsonlite::fromJSON(json)
}

read_file <- function(path, binary = FALSE) {
  n <- file.info(path)$size
  if (binary) {
    readBin(path, raw(), n)
  } else {
    readChar(path, n, TRUE)
  }
}

surround <- function(string, with) {
  paste(with, string, with, sep = "")
}

to_html_attributes <- function(data, on_empty = "", prefix = " ") {

  if (inherits(data, "html"))
    return(data)

  if (!length(data))
    return(on_empty)

  # escape attribute contents
  escaped <- unlist(lapply(data, function(el) {
    htmltools::htmlEscape(join(as.character(el), collapse = " "), attribute = TRUE)
  }))

  # generate html attributes as string
  quoted <- surround(escaped, with = "\"")
  result <- join(names(data), quoted, sep = "=", collapse = " ")

  # add prefix if necessary
  if (nzchar(prefix))
    result <- join(prefix, result)

  # mark as html and return
  class(result) <- "html"
  result

}

to_css <- function(data, on_empty = "", prefix = "") {

  if (inherits(data, "html"))
    return(data)

  if (!length(data))
    return(on_empty)

  # collapse vectors in data list
  collapsed <- unlist(lapply(data, function(el) {
    join(el, collapse = " ")
  }))

  # paste into single string
  joined <- join(names(data), collapsed, sep = ": ", collapse = "; ")

  # add prefix
  if (nzchar(prefix))
    joined <- join(prefix, joined)

  # return with trailing semi-colon
  result <- join(joined, ";", sep = "")
  class(result) <- "html"
  result
}

rbind_list <- function(data) {
  result <- do.call(mapply, c(c, data, USE.NAMES = FALSE, SIMPLIFY = FALSE))
  names(result) <- names(data[[1]])
  as.data.frame(result, stringsAsFactors = FALSE)
}

enumerate <- function(data, f, ...) {
  lapply(seq_along(data), function(i) {
    f(names(data)[[i]], data[[i]], ...)
  })
}

insert <- function(vector, index, ...) {

  dots <- list(...)
  mode(dots) <- mode(vector)
  n <- length(vector)

  result <- if (index == 0) {
    c(dots, vector)
  } else if (index == n) {
    c(vector, dots)
  } else {
    c(vector[1:index], dots, vector[(index + 1):n])
  }

  result
}

replace_binding <- function(binding, package, override) {
  # override in namespace
  if (!requireNamespace(package, quietly = TRUE))
    stop(sprintf("Failed to load namespace for package '%s'", package))

  namespace <- asNamespace(package)

  # get reference to original binding
  original <- get(binding, envir = namespace)

  # replace the binding
  if (is.function(override))
    environment(override) <- namespace

  do.call("unlockBinding", list(binding, namespace))
  assign(binding, override, envir = namespace)
  do.call("lockBinding", list(binding, namespace))

  # if package is attached, override there as well
  search_name <- paste("package", package, sep = ":")
  if (search_name %in% search()) {
    env <- as.environment(search_name)
    do.call("unlockBinding", list(binding, env))
    assign(binding, override, envir = env)
    do.call("lockBinding", list(binding, env))
  }

  # return original
  original
}

join <- function(..., sep = "", collapse = "") {
  paste(..., sep = sep, collapse = collapse)
}

shell_exec <- function(cmd, intern = FALSE, wait = TRUE, ...) {
  if (Sys.info()[["sysname"]] == "Windows")
    shell(cmd, intern = intern, wait = wait, ...)
  else
    system(cmd, intern = intern, wait = wait, ...)
}

# Adjust the graphical device in chunk options: if the device from the output
# format is png but knitr's global chunk option is not png, respect knitr's
# option, because (1) users may knitr::opts_chunk$set(dev) (which usually means
# they know what they are doing) before rmarkdown::render(), and we probably
# should not override the user's choice; (2) the png device does not work on
# certain platforms (e.g. headless servers without X11), in which case knitr
# will set the device to svg instead of png by default in knitr:::set_html_dev,
# and rmarkdown should also respect this setting, otherwise we will run into
# issues like https://github.com/rstudio/rmarkdown/issues/1100
adjust_dev <- function(opts) {
  dev <- knitr::opts_chunk$get('dev')
  if (identical(opts$dev, 'png') && length(dev) == 1 && dev != 'png') {
    opts$dev <- dev
  }
  opts
}