RollFor = RollFor or {}
local m = RollFor

--
-- json.lua
--
-- Copyright (c) 2020 rxi
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.
--

---@diagnostic disable-next-line: undefined-global
local libStub = LibStub
local json = libStub:NewLibrary( "Json-0.1.2", 1 )
if not json then return end

local getn = m.getn

-------------------------------------------------------------------------------
-- Encode
-------------------------------------------------------------------------------

local encode

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

local escape_char_map_inv = { [ "/" ] = "/" }
for k, v in pairs( escape_char_map ) do
  escape_char_map_inv[ v ] = k
end


local function escape_char( c )
  return "\\" .. (escape_char_map[ c ] or string.format( "u%04x", string.byte( c ) ))
end

local function encode_nil()
  return "null"
end

local function encode_table( val, stack )
  local res = {}
  stack = stack or {}

  -- Circular reference?
  if stack[ val ] then error( "circular reference" ) end

  stack[ val ] = true

  if rawget( val, 1 ) ~= nil or next( val ) == nil then
    -- Treat as array -- check keys are valid and it is not sparse
    local n = 0
    for k in pairs( val ) do
      if type( k ) ~= "number" then
        error( "invalid table: mixed or invalid key types" )
      end
      n = n + 1
    end
    if n ~= getn( val ) then
      error( "invalid table: sparse array" )
    end
    -- Encode
    for _, v in ipairs( val ) do
      table.insert( res, encode( v, stack ) )
    end
    stack[ val ] = nil
    return "[" .. table.concat( res, "," ) .. "]"
  else
    -- Treat as an object
    for k, v in pairs( val ) do
      if type( k ) ~= "string" then
        error( "invalid table: mixed or invalid key types" )
      end
      table.insert( res, encode( k, stack ) .. ":" .. encode( v, stack ) )
    end
    stack[ val ] = nil
    return "{" .. table.concat( res, "," ) .. "}"
  end
end

local function encode_string( val )
  return '"' .. string.gsub( val, '[%z\1-\31\\"]', escape_char ) .. '"'
end

local function encode_number( val )
  -- Check for NaN, -inf and inf
  if val ~= val or val <= -math.huge or val >= math.huge then
    error( "unexpected number value '" .. tostring( val ) .. "'" )
  end
  return string.format( "%.14g", val )
end

local type_func_map = {
  [ "nil" ] = encode_nil,
  [ "table" ] = encode_table,
  [ "string" ] = encode_string,
  [ "number" ] = encode_number,
  [ "boolean" ] = tostring,
}


encode = function( val, stack )
  local t = type( val )
  local f = type_func_map[ t ]
  if f then
    return f( val, stack )
  end
  error( "unexpected type '" .. t .. "'" )
end


function json.encode( val )
  return (encode( val ))
end

-------------------------------------------------------------------------------
-- Decode
-------------------------------------------------------------------------------

local parse

---@diagnostic disable-next-line: unused-vararg
local function create_set( ... )
  local res = {}
  local t = { unpack( arg ) }

  for i = 1, getn( t ) do
    res[ t[ i ] ] = true
  end

  return res
end

local space_chars  = create_set( " ", "\t", "\r", "\n" )
local delim_chars  = create_set( " ", "\t", "\r", "\n", "]", "}", "," )
local escape_chars = create_set( "\\", "/", '"', "b", "f", "n", "r", "t", "u" )
local literals     = create_set( "true", "false", "null" )

local literal_map  = {
  [ "true" ] = true,
  [ "false" ] = false,
  [ "null" ] = nil,
}


local function next_char( str, idx, set, negate )
  for i = idx, string.len( str ) do
    if set[ string.sub( str, i, i ) ] ~= negate then
      return i
    end
  end
  return string.len( str ) + 1
end

local function decode_error( str, idx, msg )
  local line_count = 1
  local col_count = 1
  for i = 1, idx - 1 do
    col_count = col_count + 1
    if string.sub( str, i, i ) == "\n" then
      line_count = line_count + 1
      col_count = 1
    end
  end
  error( string.format( "%s at line %d col %d", msg, line_count, col_count ) )
end

local function codepoint_to_utf8( n )
  ---@diagnostic disable-next-line: undefined-field
  local mod = math.mod
  -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
  local f = math.floor
  if n <= tonumber( "7f", 16 ) then
    return string.char( n )
  elseif n <= tonumber( "7ff", 16 ) then
    return string.char( f( n / 64 ) + 192, mod( n, 64 ) + 128 )
  elseif n <= tonumber( "ffff", 16 ) then
    return string.char( f( n / 4096 ) + 224, f( mod( n, 4096 ) / 64 ) + 128, mod( n, 64 ) + 128 )
  elseif n <= tonumber( "10ffff", 16 ) then
    return string.char( f( n / 262144 ) + 240, f( mod( n, 262144 ) / 4096 ) + 128,
      f( mod( n, 4096 ) / 64 ) + 128, mod( n, 64 ) + 128 )
  end
  error( string.format( "invalid unicode codepoint '%x'", n ) )
end

local function parse_unicode_escape( s )
  local n1 = tonumber( string.sub( s, 1, 4 ), 16 )
  local n2 = tonumber( string.sub( s, 7, 10 ), 16 )
  -- Surrogate pair?
  if n2 then
    return codepoint_to_utf8( (n1 - tonumber( "d800", 16 )) * tonumber( "400", 16 ) + (n2 - tonumber( "dc00", 16 )) + tonumber( "10000", 16 ) )
  else
    return codepoint_to_utf8( n1 )
  end
end

local function parse_string( str, i )
  local res = ""
  local j = i + 1
  local k = j

  while j <= string.len( str ) do
    local x = string.byte( str, j )

    if x < 32 then
      decode_error( str, j, "control character in string" )
    elseif x == 92 then -- `\`: Escape
      res = res .. string.sub( str, k, j - 1 )
      j = j + 1
      local c = string.sub( str, j, j )
      if c == "u" then
        local hex = string.match( str, "^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1 )
            or string.match( str, "^%x%x%x%x", j + 1 )
            or decode_error( str, j - 1, "invalid unicode escape in string" )
        res = res .. parse_unicode_escape( hex )
        j = j + getn( hex )
      else
        if not escape_chars[ c ] then
          decode_error( str, j - 1, "invalid escape char '" .. c .. "' in string" )
        end
        res = res .. escape_char_map_inv[ c ]
      end
      k = j + 1
    elseif x == 34 then -- `"`: End of string
      res = res .. string.sub( str, k, j - 1 )
      return res, j + 1
    end

    j = j + 1
  end

  decode_error( str, i, "expected closing quote for string" )
end

local function parse_number( str, i )
  local x = next_char( str, i, delim_chars )
  local s = string.sub( str, i, x - 1 )
  local n = tonumber( s )
  if not n then
    decode_error( str, i, "invalid number '" .. s .. "'" )
  end
  return n, x
end

local function parse_literal( str, i )
  local x = next_char( str, i, delim_chars )
  local word = string.sub( str, i, x - 1 )
  if not literals[ word ] then
    decode_error( str, i, "invalid literal '" .. word .. "'" )
  end
  return literal_map[ word ], x
end

local function parse_array( str, i )
  local res = {}
  local n = 1
  i = i + 1
  while 1 do
    local x
    i = next_char( str, i, space_chars, true )
    -- Empty / end of array?
    if string.sub( str, i, i ) == "]" then
      i = i + 1
      break
    end
    -- Read token
    x, i = parse( str, i )
    res[ n ] = x
    n = n + 1
    -- Next token
    i = next_char( str, i, space_chars, true )
    local chr = string.sub( str, i, i )
    i = i + 1
    if chr == "]" then break end
    if chr ~= "," then decode_error( str, i, "expected ']' or ','" ) end
  end
  return res, i
end

local function parse_object( str, i )
  local res = {}
  i = i + 1
  while 1 do
    local key, val
    i = next_char( str, i, space_chars, true )
    -- Empty / end of object?
    if string.sub( str, i, i ) == "}" then
      i = i + 1
      break
    end
    -- Read key
    if string.sub( str, i, i ) ~= '"' then
      decode_error( str, i, "expected string for key" )
    end
    key, i = parse( str, i )
    -- Read ':' delimiter
    i = next_char( str, i, space_chars, true )
    if string.sub( str, i, i ) ~= ":" then
      decode_error( str, i, "expected ':' after key" )
    end
    i = next_char( str, i + 1, space_chars, true )
    -- Read value
    val, i = parse( str, i )
    -- Set
    res[ key ] = val
    -- Next token
    i = next_char( str, i, space_chars, true )
    local chr = string.sub( str, i, i )
    i = i + 1
    if chr == "}" then break end
    if chr ~= "," then decode_error( str, i, "expected '}' or ','" ) end
  end
  return res, i
end

local char_func_map = {
  [ '"' ] = parse_string,
  [ "0" ] = parse_number,
  [ "1" ] = parse_number,
  [ "2" ] = parse_number,
  [ "3" ] = parse_number,
  [ "4" ] = parse_number,
  [ "5" ] = parse_number,
  [ "6" ] = parse_number,
  [ "7" ] = parse_number,
  [ "8" ] = parse_number,
  [ "9" ] = parse_number,
  [ "-" ] = parse_number,
  [ "t" ] = parse_literal,
  [ "f" ] = parse_literal,
  [ "n" ] = parse_literal,
  [ "[" ] = parse_array,
  [ "{" ] = parse_object,
}

parse = function( str, idx )
  local chr = string.sub( str, idx, idx )
  local f = char_func_map[ chr ]
  if f then
    return f( str, idx )
  end
  decode_error( str, idx, "unexpected character '" .. chr .. "'" )
end

function json.decode( str )
  if type( str ) ~= "string" then
    error( "expected argument of type string, got " .. type( str ) )
  end
  local res, idx = parse( str, next_char( str, 1, space_chars, true ) )
  idx = next_char( str, idx, space_chars, true )
  if idx <= string.len( str ) then
    decode_error( str, idx, "trailing garbage" )
  end
  return res
end
