computable-pandoc/src/extensions.lua

---------------------------------- EXTENSIONS ---------------------------------

-- Tries popen
-- @param ... string: Chunks for popen
-- @return boolean, string: Status and output of popen
function io.try(...)
  local cmd = table.concat({...}, " ") .. " 2>&1"
  local handle = io.popen(cmd)
  local output = handle:read("*a")
  local status = (handle:close() ~= nil and true or false)
  return status, output
end

-- Gets OS short name
-- It is just intented to know if it is Linux, macOS or Windows.
-- Sorry 
-- @return string: "linux" or "bsd" or "macos" or "windows"
function os.uname() 
  local status, output = io.try("uname")
  if status then
    output = output:gsub(" .*", ""):lower()
    if output ~= "linux" and output:match("bsd") ~= nil then
      return "bsd"
    elseif out ~= "linux" then
      return "macos"
    end
    return "linux"
  end
  return "windows"
end

-- Checks if OS is windows
-- @return boolean: Windows or not
function os.iswin()
  return os.uname() == "windows"
end

-- Checks if OS is Unix
-- @return boolean: Unix or not
function os.isunix()
  return os.uname() ~= "windows"
end

-- Changes newlines so everything is in one line
-- @return string: String with formatted newlines as literal "\n"
function string:linearize()
  return self:gsub("\n", "\\\\n")
end

-- Checks if string is empty
-- @return boolean: Empty or not
function string:isempty()
  return self == ''
end

function string:lstrip()
  return self:gsub("^%s+", "")
end

function string:rstrip()
  return self:gsub("%s+$", "")
end

function string:strip()
  return self:lstrip():rstrip()
end

-- The following are heavily influenced by Python pathlib
-- Check: https://docs.python.org/3/library/pathlib.html

-- Checks if string is a file or directory
-- @return boolean: Exists or not
function string:exists()
  return os.rename(self, self) ~= nil
end

-- Checks if string is a file
-- @return boolean: File or not
function string:isfile()
  if self:exists() then
    return io.open(self, "a+") ~= nil
  end
  return false
end

-- Checks if string is a directory
-- @return boolean: Directory or not
function string:isdir()
  if self:exists() then
    return io.open(self, "a+") == nil
  elseif self == "." or self == ".." then
    return true
  end
  return false
end

-- Reads file content
-- @return string or nil: File content or nil
function string:read_text()
  if self:exists() then
    return io.open(self):read("*a")
  end
end

function string:stem()
  return self:gsub("%.%a+$", "")
end

-- Gets file extensions
-- @return table: list of file extensions
function string:suffixes()
  local suffixes = {}
  for suffix in self:gmatch("%.%a+") do
    table.insert(suffixes, suffix)
  end
  return suffixes
end

-- Gets file final extension
-- @return string: final file extension
function string:suffix()
  local suffixes = self:suffixes()
  if suffixes[#suffixes] then
    return suffixes[#suffixes]
  end
  return ""
end

-- Requires Pandoc
-- Check: https://pandoc.org/lua-filters.html#module-pandoc

if pandoc ~= nil then

  -- Gets file extension namespace
  -- Check: https://pandoc.org/MANUAL.html#general-options
  -- @param file string: File name
  -- @return string: File extension according to Pandoc format namespaces
  function pandoc.getext(file)
    local ext = file:suffix():gsub("^.", "")
    return ((ext == "md" or ext:isempty()) and "markdown" or ext)
  end

  -- Pandoc converter
  -- Converts input file name into output format name.
  -- If ofile is not nil, writes output file name instead of returning content.
  -- If iformat is nil, defaults to ifile extension name.
  -- @param ifile string: Input file name
  -- @param oformat string: Output format name
  -- @param ofile string or nil: Output file name
  -- @param iformat string or nil: Input format name
  -- @return string or nil: Output file content
  function pandoc.convert(ifile, oformat, ofile, iformat)
    iformat = (iformat == nil and pandoc.getext(ifile) or iformat)
    local doc = pandoc.write(pandoc.read(ifile:read_text(), iformat), oformat)
    if ofile == nil then
      return doc
    else
      local eol = (os:isunix() and "\n" or "\r\n")
      io.open(ofile, "w"):write(doc, eol):close()
    end
  end

end