----------------------------------- LITERATE ----------------------------------

-- Types functions extensions

-- Changes newlines so everything is in one line
function string:linearize()
  return self:gsub("\n", "\\\\n")
end

-- Checks if is empty
function string:isempty()
  return self == ''
end

-- Checks if is directory
function string:isdir()
  if self ~= "." and os.rename(self, self) == nil then
    return false
  end
  return true
end

-- Variable for all literate stuff
local lit = {}

-- Status indicator
lit.status = true

-- Valid metadata structure
lit.metastruct = {
  ["mandatory"] = {
    -- Value as table == whole patterns to match
    ["id"] = {"%a[_%w]*"}, 
  },
  ["optional"] = {
    ["lang"] = {"lua", "fennel", "python", "js", "ruby", "lisp", "graphviz"}, 
    ["cmd"] = {".+"},
    -- Value as string == type to match
    ["args"] = "table",
    ["shift"] = "boolean",
    ["wipe"] = "boolean",
    ["typed"] = "boolean",
    ["link"] = "path",
    ["img"] = "path",
    ["alt"] = "string",
    ["dump"] = "path",
    ["quote"] = "boolean",
  },
}

function lit.getmetaval(meta, key)
  local mtype = pandoc.utils.type(meta[key])
  local mval = meta[key]
  if mtype == "Inlines" then
    mval = pandoc.utils.stringify(mval) 
    mtype = pandoc.utils.type(mval)
  end
  return mval, mtype
end

function lit.checkmetatype(type, meta, key)
  local mval, mtype = lit.getmetaval(meta, key)
  local err = ""
  if type ~= mtype then
    if type == "path" then
      if not(pandoc.path.directory(mval):isdir()) then
        err = "Invalid path '" .. mval .. "' in key '" .. key .. "'"
      end
    else
      err = "Invalid type '" .. mtype .. "' in key '" .. key .. "'"
    end
  end
  if not(err:isempty()) then lit.puts(err, "ERROR") end
end

function lit.checkmetatable(table, meta, key)
  local mval = lit.getmetaval(meta, key) 
  local err = ""
  for _, pattern in pairs(table) do
    if mval:match("^" .. pattern .. "$") then
      err = ""
      break
    else
      err = "Invalid value '" .. mval .. "' in key '" .. key .. "'"
    end
  end
  if not(err:isempty()) then lit.puts(err, "ERROR") end
end

function lit.checkmeta(meta, kind)
  for key, val in pairs(lit.metastruct[kind]) do
    if meta[key] == nil then
      if kind == "mandatory" then
        lit.puts("Key '" .. key .. "' not found", "ERROR")
      end
    else
      if type(val) == "table" then
        lit.checkmetatable(val, meta, key)
      else
        lit.checkmetatype(val, meta, key)
      end
    end
  end
end

function lit.setmeta(meta)
  lit.checkmeta(meta, "mandatory")
  lit.checkmeta(meta, "optional")
  -- TODO checks for 1) extra keys and 2) duplicates
  -- Set defaults if lit.status = true
  return meta
end

-- Grammars
lit.g = {}

-- Lexical elements
lit.newline = lpeg.P"\r"^-1 * lpeg.P"\n"
lit.space = lpeg.S" \t"
lit.anyspace = lpeg.S" \t\r\n"
lit.spot = (1 - lit.anyspace)
lit.any = (lit.spot + lit.space)
lit.yamlheader = lit.space^0 * lpeg.P"---" * lit.space^0 * lit.newline
lit.yamlfooter = lit.space^0 * lpeg.P"..." * lit.space^0 * lit.newline^-1
lit.yamlbody = -lit.yamlfooter * lit.any^0 * lit.newline
lit.id = lpeg.R("az", "AZ") * lpeg.R("az", "AZ", "09")^0
lit.ref = lpeg.P"#" * lit.id

-- Blocks grammar
lit.g.block = lpeg.P {
  "Block";
  Block = lpeg.Ct(lpeg.V"YAML" * lpeg.V"Code", "name");
  YAML = lpeg.C(lit.yamlheader * lit.yamlbody^0 * lit.yamlfooter);
  Code = lpeg.C((lit.any + lit.newline)^0);
}

-- Evals Lisp code
--[[
function lit.eval(code)
  local is_passed, out = pcall (
    function () return fennel.eval(code) end,
    function (e) return e end
  )
  local lua = ""
  local out = tostring(out)
  local preview = out:gsub("\n.*", "")
  if is_passed then
    lua = fennel.compileString(code)
  end
  return {is_passed = is_passed, preview = preview, out = out, lua = lua}
end
]]--

function lit.assert(e, status)
  if status == false then
    lit.puts("Aborted due previous errors", "ERROR")
    os.exit(1)
  end
  return e
end

function lit.debuglevel(str)
  if str == "ERROR" then
    lit.status = false
    return 2
  elseif str == "WARNING" then
    return 1
  else
    return 0
  end
end

function lit.puts(msg, kind)
  local kind = kind or "INFO"
  local verbosity = lit.debuglevel(PANDOC_STATE.verbosity)
  level = lit.debuglevel(kind)
  if level >= verbosity then
    print("[" .. kind .. "] [LIT] " .. msg)
  end
end

function lit.parseyaml(rawyaml)
  -- TODO: avoid popen?
  local yaml = io.popen("pandoc -t json <<<\"" .. rawyaml .. "\" 2>&1")
  if yaml:read("*l"):sub(1, 1) == "{" then
    yaml = pandoc.read(rawyaml).meta
    if pandoc.utils.stringify(yaml):isempty() then
      lit.puts("Empty YAML", "ERROR")
    else
      return lit.setmeta(yaml)
    end
  else
    lit.puts("Invalid YAML", "ERROR")
    return nil
  end
end

function lit.parseblock(parsed)
  lit.puts("Parsing " .. table.concat(parsed, "\n"):linearize())
  local yaml = lit.parseyaml(parsed[1])
  -- TODO: parsecode
  return "TODO"
end

function lit.getblock(codeblock)
  local parsed = lpeg.match(lit.g.block, codeblock.text)
  parsed = (parsed ~= nil and lit.parseblock(parsed) or parsed)
  return codeblock, lit.status
end

function lit.getinsert(code)
  return code, lit.status
end

return lit