-- https://github.com/actboy168/json.lua
-- slightly modified to only decode jsonc
local type = type
local next = next
local error = error
local tonumber = tonumber
local string_char = string.char
local string_byte = string.byte
local string_find = string.find
local string_match = string.match
local string_gsub = string.gsub
local string_sub = string.sub
local string_format = string.format

local utf8_char

if _VERSION == "Lua 5.1" or _VERSION == "Lua 5.2" then
  local math_floor = math.floor
  function utf8_char(c)
    if c <= 0x7f then
      return string_char(c)
    elseif c <= 0x7ff then
      return string_char(math_floor(c / 64) + 192, c % 64 + 128)
    elseif c <= 0xffff then
      return string_char(
        math_floor(c / 4096) + 224,
        math_floor(c % 4096 / 64) + 128,
        c % 64 + 128
      )
    elseif c <= 0x10ffff then
      return string_char(
        math_floor(c / 262144) + 240,
        math_floor(c % 262144 / 4096) + 128,
        math_floor(c % 4096 / 64) + 128,
        c % 64 + 128
      )
    end
    error(string_format("invalid UTF-8 code '%x'", c))
  end
else
  utf8_char = utf8.char
end

local json = {}

local objectMt = {}

function json.createEmptyObject()
  return setmetatable({}, objectMt)
end

function json.isObject(t)
  if t[1] ~= nil then
    return false
  end
  return next(t) ~= nil or getmetatable(t) == objectMt
end

if debug and debug.upvalueid then
  -- Generate a lightuserdata
  json.null = debug.upvalueid(json.createEmptyObject, 1)
else
  json.null = function() end
end

local encode_escape_map = {
  ["\""] = "\\\"",
  ["\\"] = "\\\\",
  ["/"]  = "\\/",
  ["\b"] = "\\b",
  ["\f"] = "\\f",
  ["\n"] = "\\n",
  ["\r"] = "\\r",
  ["\t"] = "\\t",
}

local decode_escape_set = {}
local decode_escape_map = {}
for k, v in next, encode_escape_map do
  decode_escape_map[v] = k
  decode_escape_set[string_byte(v, 2)] = true
end

local statusBuf
local statusPos
local statusTop
local statusAry = {}
local statusRef = {}

local function find_line()
  local line = 1
  local pos = 1
  while true do
    local f, _, nl1, nl2 = string_find(statusBuf, "([\n\r])([\n\r]?)", pos)
    if not f then
      return line, statusPos - pos + 1
    end
    local newpos = f + ((nl1 == nl2 or nl2 == "") and 1 or 2)
    if newpos > statusPos then
      return line, statusPos - pos + 1
    end
    pos = newpos
    line = line + 1
  end
end

local function decode_error(msg)
  error(string_format("ERROR: %s at line %d col %d", msg, find_line()), 2)
end

local function get_word()
  return string_match(statusBuf, "^[^ \t\r\n%]},]*", statusPos)
end

local function skip_comment(b)
  if b ~= 47 --[[ '/' ]] then
    return
  end
  local c = string_byte(statusBuf, statusPos + 1)
  if c == 42 --[[ '*' ]] then
    -- block comment
    local pos = string_find(statusBuf, "*/", statusPos)
    if pos then
      statusPos = pos + 2
    else
      statusPos = #statusBuf + 1
    end
    return true
  elseif c == 47 --[[ '/' ]] then
    -- line comment
    local pos = string_find(statusBuf, "[\r\n]", statusPos)
    if pos then
      statusPos = pos
    else
      statusPos = #statusBuf + 1
    end
    return true
  end
end

local function next_byte()
  local pos = string_find(statusBuf, "[^ \t\r\n]", statusPos)
  if pos then
    statusPos = pos
    local b = string_byte(statusBuf, pos)
    if not skip_comment(b) then
      return b
    end
    return next_byte()
  end
  return -1
end

local function decode_unicode_surrogate(s1, s2)
  return utf8_char(0x10000 + (tonumber(s1, 16) - 0xd800) * 0x400 + (tonumber(s2, 16) - 0xdc00))
end

local function decode_unicode_escape(s)
  return utf8_char(tonumber(s, 16))
end

local function decode_string()
  local has_unicode_escape = false
  local has_escape = false
  local i = statusPos + 1
  while true do
    i = string_find(statusBuf, '[%z\1-\31\\"]', i)
    if not i then
      decode_error "expected closing quote for string"
    end
    local x = string_byte(statusBuf, i)
    if x < 32 then
      statusPos = i
      decode_error "control character in string"
    end
    if x == 34 --[[ '"' ]] then
      local s = string_sub(statusBuf, statusPos + 1, i - 1)
      if has_unicode_escape then
        s = string_gsub(string_gsub(s
        , "\\u([dD][89aAbB]%x%x)\\u([dD][c-fC-F]%x%x)", decode_unicode_surrogate)
        , "\\u(%x%x%x%x)", decode_unicode_escape)
      end
      if has_escape then
        s = string_gsub(s, "\\.", decode_escape_map)
      end
      statusPos = i + 1
      return s
    end
    --assert(x == 92 --[[ "\\" ]])
    local nx = string_byte(statusBuf, i + 1)
    if nx == 117 --[[ "u" ]] then
      if not string_match(statusBuf, "^%x%x%x%x", i + 2) then
        statusPos = i
        decode_error "invalid unicode escape in string"
      end
      has_unicode_escape = true
      i = i + 6
    else
      if not decode_escape_set[nx] then
        statusPos = i
        decode_error("invalid escape char '" .. (nx and string_char(nx) or "<eol>") .. "' in string")
      end
      has_escape = true
      i = i + 2
    end
  end
end

local function decode_number()
  local num, c = string_match(statusBuf, "^([0-9]+%.?[0-9]*)([eE]?)", statusPos)
  if not num or string_byte(num, -1) == 0x2E --[[ "." ]] then
    decode_error("invalid number '" .. get_word() .. "'")
  end
  if c ~= "" then
    num = string_match(statusBuf, "^([^eE]*[eE][-+]?[0-9]+)[ \t\r\n%]},/]", statusPos)
    if not num then
      decode_error("invalid number '" .. get_word() .. "'")
    end
  end
  statusPos = statusPos + #num
  return tonumber(num)
end

local function decode_number_zero()
  local num, c = string_match(statusBuf, "^(.%.?[0-9]*)([eE]?)", statusPos)
  if not num or string_byte(num, -1) == 0x2E --[[ "." ]] or string_match(statusBuf, "^.[0-9]+", statusPos) then
    decode_error("invalid number '" .. get_word() .. "'")
  end
  if c ~= "" then
    num = string_match(statusBuf, "^([^eE]*[eE][-+]?[0-9]+)[ \t\r\n%]},/]", statusPos)
    if not num then
      decode_error("invalid number '" .. get_word() .. "'")
    end
  end
  statusPos = statusPos + #num
  return tonumber(num)
end

local function decode_number_negative()
  statusPos = statusPos + 1
  local c = string_byte(statusBuf, statusPos)
  if c then
    if c == 0x30 then
      return -decode_number_zero()
    elseif c > 0x30 and c < 0x3A then
      return -decode_number()
    end
  end
  decode_error("invalid number '" .. get_word() .. "'")
end

local function decode_true()
  if string_sub(statusBuf, statusPos, statusPos + 3) ~= "true" then
    decode_error("invalid literal '" .. get_word() .. "'")
  end
  statusPos = statusPos + 4
  return true
end

local function decode_false()
  if string_sub(statusBuf, statusPos, statusPos + 4) ~= "false" then
    decode_error("invalid literal '" .. get_word() .. "'")
  end
  statusPos = statusPos + 5
  return false
end

local function decode_null()
  if string_sub(statusBuf, statusPos, statusPos + 3) ~= "null" then
    decode_error("invalid literal '" .. get_word() .. "'")
  end
  statusPos = statusPos + 4
  return json.null
end

local function decode_array()
  statusPos = statusPos + 1
  local res = {}
  local chr = next_byte()
  if chr == 93 --[[ ']' ]] then
    statusPos = statusPos + 1
    return res
  end
  statusTop = statusTop + 1
  statusAry[statusTop] = true
  statusRef[statusTop] = res
  return res
end

local function decode_object()
  statusPos = statusPos + 1
  local res = {}
  local chr = next_byte()
  if chr == 125 --[[ ']' ]] then
    statusPos = statusPos + 1
    return json.createEmptyObject()
  end
  statusTop = statusTop + 1
  statusAry[statusTop] = false
  statusRef[statusTop] = res
  return res
end

local decode_uncompleted_map = {
  [string_byte '"'] = decode_string,
  [string_byte "0"] = decode_number_zero,
  [string_byte "1"] = decode_number,
  [string_byte "2"] = decode_number,
  [string_byte "3"] = decode_number,
  [string_byte "4"] = decode_number,
  [string_byte "5"] = decode_number,
  [string_byte "6"] = decode_number,
  [string_byte "7"] = decode_number,
  [string_byte "8"] = decode_number,
  [string_byte "9"] = decode_number,
  [string_byte "-"] = decode_number_negative,
  [string_byte "t"] = decode_true,
  [string_byte "f"] = decode_false,
  [string_byte "n"] = decode_null,
  [string_byte "["] = decode_array,
  [string_byte "{"] = decode_object,
}
local function unexpected_character()
  decode_error("unexpected character '" .. string_sub(statusBuf, statusPos, statusPos) .. "'")
end
local function unexpected_eol()
  decode_error("unexpected character '<eol>'")
end

local decode_map = {}
for i = 0, 255 do
  decode_map[i] = decode_uncompleted_map[i] or unexpected_character
end
decode_map[-1] = unexpected_eol

local function decode()
  return decode_map[next_byte()]()
end

local function decode_item()
  local top = statusTop
  local ref = statusRef[top]
  if statusAry[top] then
    ref[#ref + 1] = decode()
  else
    local key = decode_string()
    if next_byte() ~= 58 --[[ ':' ]] then
      decode_error "expected ':'"
    end
    statusPos = statusPos + 1
    ref[key] = decode()
  end
  if top == statusTop then
    repeat
      local chr = next_byte()
      statusPos = statusPos + 1
      if chr == 44 --[[ "," ]] then
        local c = next_byte()
        if statusAry[statusTop] then
          if c ~= 93 --[[ "]" ]] then return end
        else
          if c ~= 125 --[[ "}" ]] then return end
        end
        statusPos = statusPos + 1
      else
        if statusAry[statusTop] then
          if chr ~= 93 --[[ "]" ]] then decode_error "expected ']' or ','" end
        else
          if chr ~= 125 --[[ "}" ]] then decode_error "expected '}' or ','" end
        end
      end
      statusTop = statusTop - 1
    until statusTop == 0
  end
end

function json.decode(str)
  if type(str) ~= "string" then
    error("expected argument of type string, got " .. type(str))
  end
  statusBuf = str
  statusPos = 1
  statusTop = 0
  if next_byte() == -1 then
    return json.null
  end
  local res = decode()
  while statusTop > 0 do
    decode_item()
  end
  if string_find(statusBuf, "[^ \t\r\n]", statusPos) then
    decode_error "trailing garbage"
  end
  return res
end

return json