local concat, format, sort, type = table.concat, string.format, table.sort, type
local setmetatable = setmetatable
local pdf_escape = require'luatagging-pdf-escape'

local type PdfObject = boolean | number | string | Name | Dict | Array | Ref | Raw
local type Name = {string}
local interface Ref is {integer}
  lazy: function(Ref): integer
end
local type Array = {PdfObject}
local type Dict = {(string | RawKey): PdfObject}
local type Raw = {string}
local type RawKey = function(string): Raw
local name_metatable: metatable<Name> = {}
local dict_metatable: metatable<Dict> = {}
local array_metatable: metatable<Array> = {}
local ref_metatable: metatable<Ref> = {}
local raw_metatable: metatable<Raw> = {}

local raw: RawKey = function(literal: string): Raw
  return setmetatable({literal}, raw_metatable)
end

local names: {string: Name} = setmetatable({}, {__index = function(t: {string: Name}, name: string): Name
  if name == nil then return nil end
  local name_dict: Name = setmetatable({name, pdf_escape.escape_name(name)}, name_metatable)
  t[name] = name_dict
  return name_dict
end})

local append_obj: function({string}, integer, PdfObject): integer
local function append_dict_content(existing: {string}, i: integer, obj: Dict): integer
  local keys, length: {string}, integer = {}, 0
  for k in next, obj do
    if k ~= raw then
      length = length + 1
      keys[length] = k as string
    end
  end
  sort(keys)
  for j = 1, length do
    i = i + 1
    local key = keys[j]
    existing[i] = names[key][2]
    i = append_obj(existing, i, obj[key])
  end
  local raw_content = obj[raw]
  if raw_content then
    i = i + 1
    existing[i] = raw_content as string
  end
  return i
end
function append_obj(existing: {string}, i: integer, obj: PdfObject): integer
  local t = type(obj)
  local result: string
  if t == nil then
  elseif t == 'boolean' then
    result = obj as boolean and ' true' or ' false'
  elseif t == 'number' then
    if math.type(obj) == 'integer' then
    -- if obj is integer then
      result = format(' %i', obj as integer)
    else
      result = format(' %f', obj as number) -- TODO: Proper PDF syntax
    end
  elseif t == 'string' then
    result = pdf_escape.escape_text(obj as string)
  elseif t == 'table' then
    local mt = getmetatable(obj) as any
    if mt == name_metatable then
      result = (obj as Name)[2]
    elseif mt == dict_metatable then
      i = i + 1
      existing[i] = '<<'
      i = append_dict_content(existing, i, obj as Dict)
      i = i + 1
      existing[i] = '>>'
      return i
    elseif mt == array_metatable then
      local arr = obj as Array
      i = i + 1
      existing[i] = '['
      for j = 1, #arr do
        i = append_obj(existing, i, arr[j])
      end
      i = i + 1
      existing[i] = ']'
      return i
    elseif mt == ref_metatable then
      local ref = obj as Ref
      local lazy = ref.lazy
      local id: integer
      if lazy then
        id = lazy(ref)
      else
        id = ref[1]
      end
      result = format(' %i 0 R', id)
    elseif mt == raw_metatable then
      i = i + 1
      existing[i] = ' '
      result = (obj as Raw)[1]
    else
      print(require'inspect'(obj))
      error'unknown table'
    end
  elseif t == 'function' then
    return error'unknown function'
  elseif obj == nil then
    i = i + 1
    existing[i] = ' null'
  else
    return error'unknown object'
  end
  i = i + 1
  existing[i] = result
  return i
end

local function to_pdf_string(data: PdfObject): string
  local existing = {}
  local i = append_obj(existing, 0, data)
  return concat(existing, '', 1, i)
end

local function to_pdf_dict_content(data: Dict): string
  local existing = {}
  local i = append_dict_content(existing, 0, data)
  return concat(existing, '', 1, i)
end

local record Objectwriter
  type PdfObject = PdfObject
  type Ref = Ref
  type Array = Array
  type Name = Name
  type Dict = Dict
  to_pdf_string: function(data: PdfObject): string
  to_pdf_dict_content: function(data: Dict): string
  names: {string: Name}
  dict: function(d: {(string | RawKey): PdfObject}): Dict
  array: function(d: {PdfObject}): Array
  ref: function(id: integer): Ref
  lazy: function(f: function(Ref): integer): Ref
  raw: RawKey
end

local objectwriter: Objectwriter = {
  to_pdf_string = to_pdf_string,
  to_pdf_dict_content = to_pdf_dict_content,
  names = names,
  dict = function(d: {(string | RawKey): PdfObject}): Dict return setmetatable(d, dict_metatable) end,
  array = function(d: {PdfObject}): Array return setmetatable(d, array_metatable) end,
  ref = function(id: integer): Ref return setmetatable({id}, ref_metatable) end,
  lazy = function(f: function(Ref): integer): Ref return setmetatable({lazy = f}, ref_metatable) end,
  raw = raw,
}

return objectwriter