-- -*- coding: utf-8 -*-

--

-- Simple JSON encoding and decoding in pure Lua.

--

-- Copyright 2010-2013 Jeffrey Friedl

-- http://regex.info/blog/

--

-- Latest version: http://regex.info/blog/lua/json

--

-- This code is released under a Creative Commons CC-BY "Attribution" License:

-- http://creativecommons.org/licenses/by/3.0/deed.en_US

--

-- It can be used for any purpose so long as the copyright notice and

-- web-page links above are maintained. Enjoy.

--

local VERSION = 20131118.9  -- version history at end of file

local OBJDEF = { VERSION = VERSION }

--

-- Simple JSON encoding and decoding in pure Lua.

-- http://www.json.org/

--

--

--   JSON = (loadfile "JSON.lua")() -- one-time load of the routines

--

--   local lua_value = JSON:decode(raw_json_text)

--

--   local raw_json_text    = JSON:encode(lua_table_or_value)

--   local pretty_json_text = JSON:encode_pretty(lua_table_or_value) -- "pretty printed" version for human readability

--

--

-- DECODING

--

--   JSON = (loadfile "JSON.lua")() -- one-time load of the routines

--

--   local lua_value = JSON:decode(raw_json_text)

--

--   If the JSON text is for an object or an array, e.g.

--     { "what": "books", "count": 3 }

--   or

--     [ "Larry", "Curly", "Moe" ]

--

--   the result is a Lua table, e.g.

--     { what = "books", count = 3 }

--   or

--     { "Larry", "Curly", "Moe" }

--

--

--   The encode and decode routines accept an optional second argument, "etc", which is not used

--   during encoding or decoding, but upon error is passed along to error handlers. It can be of any

--   type (including nil).

--

--   With most errors during decoding, this code calls

--

--      JSON:onDecodeError(message, text, location, etc)

--

--   with a message about the error, and if known, the JSON text being parsed and the byte count

--   where the problem was discovered. You can replace the default JSON:onDecodeError() with your

--   own function.

--

--   The default onDecodeError() merely augments the message with data about the text and the

--   location if known (and if a second 'etc' argument had been provided to decode(), its value is

--   tacked onto the message as well), and then calls JSON.assert(), which itself defaults to Lua's

--   built-in assert(), and can also be overridden.

--

--   For example, in an Adobe Lightroom plugin, you might use something like

--

--          function JSON:onDecodeError(message, text, location, etc)

--             LrErrors.throwUserError("Internal Error: invalid JSON data")

--          end

--

--   or even just

--

--          function JSON.assert(message)

--             LrErrors.throwUserError("Internal Error: " .. message)

--          end

--

--   If JSON:decode() is passed a nil, this is called instead:

--

--      JSON:onDecodeOfNilError(message, nil, nil, etc)

--

--   and if JSON:decode() is passed HTML instead of JSON, this is called:

--

--      JSON:onDecodeOfHTMLError(message, text, nil, etc)

--

--   The use of the fourth 'etc' argument allows stronger coordination between decoding and error

--   reporting, especially when you provide your own error-handling routines. Continuing with the

--   the Adobe Lightroom plugin example:

--

--          function JSON:onDecodeError(message, text, location, etc)

--             local note = "Internal Error: invalid JSON data"

--             if type(etc) = 'table' and etc.photo then

--                note = note .. " while processing for " .. etc.photo:getFormattedMetadata('fileName')

--             end

--             LrErrors.throwUserError(note)

--          end

--

--            :

--            :

--

--          for i, photo in ipairs(photosToProcess) do

--               :             

--               :             

--               local data = JSON:decode(someJsonText, { photo = photo })

--               :             

--               :             

--          end

--

--

--

--

-- DECODING AND STRICT TYPES

--

--   Because both JSON objects and JSON arrays are converted to Lua tables, it's not normally

--   possible to tell which a JSON type a particular Lua table was derived from, or guarantee

--   decode-encode round-trip equivalency.

--

--   However, if you enable strictTypes, e.g.

--

--      JSON = (loadfile "JSON.lua")() --load the routines

--      JSON.strictTypes = true

--

--   then the Lua table resulting from the decoding of a JSON object or JSON array is marked via Lua

--   metatable, so that when re-encoded with JSON:encode() it ends up as the appropriate JSON type.

--

--   (This is not the default because other routines may not work well with tables that have a

--   metatable set, for example, Lightroom API calls.)

--

--

-- ENCODING

--

--   JSON = (loadfile "JSON.lua")() -- one-time load of the routines

--

--   local raw_json_text    = JSON:encode(lua_table_or_value)

--   local pretty_json_text = JSON:encode_pretty(lua_table_or_value) -- "pretty printed" version for human readability

--   On error during encoding, this code calls:

--

--    JSON:onEncodeError(message, etc)

--

--   which you can override in your local JSON object.

--

--   If the Lua table contains both string and numeric keys, it fits neither JSON's

--   idea of an object, nor its idea of an array. To get around this, when any string

--   key exists (or when non-positive numeric keys exist), numeric keys are converted

--   to strings.

--

--   For example, 

--     JSON:encode({ "one", "two", "three", SOMESTRING = "some string" }))

--   produces the JSON object

--     {"1":"one","2":"two","3":"three","SOMESTRING":"some string"}

--

--   To prohibit this conversion and instead make it an error condition, set

--      JSON.noKeyConversion = true

--

-- SUMMARY OF METHODS YOU CAN OVERRIDE IN YOUR LOCAL LUA JSON OBJECT

--

--    assert

--    onDecodeError

--    onDecodeOfNilError

--    onDecodeOfHTMLError

--    onEncodeError

--

--  If you want to create a separate Lua JSON object with its own error handlers,

--  you can reload JSON.lua or use the :new() method.

--

---------------------------------------------------------------------------

local author = "-[ JSON.lua package by Jeffrey Friedl (http://regex.info/blog/lua/json), version " .. tostring(VERSION) .. " ]-"

local isArray  = { __tostring = function() return "JSON array"  end }    isArray.__index  = isArray

local isObject = { __tostring = function() return "JSON object" end }    isObject.__index = isObject

function OBJDEF:newArray(tbl)

   return setmetatable(tbl or {}, isArray)

end

function OBJDEF:newObject(tbl)

   return setmetatable(tbl or {}, isObject)

end

local function unicode_codepoint_as_utf8(codepoint)

   --

   -- codepoint is a number

   --

   if codepoint <= 127 then

      return string.char(codepoint)

   elseif codepoint <= 2047 then

      --

      -- 110yyyxx 10xxxxxx         <-- useful notation from http://en.wikipedia.org/wiki/Utf8

      --

      local highpart = math.floor(codepoint / 0x40)

      local lowpart  = codepoint - (0x40 * highpart)

      return string.char(0xC0 + highpart,

                         0x80 + lowpart)

   elseif codepoint <= 65535 then

      --

      -- 1110yyyy 10yyyyxx 10xxxxxx

      --

      local highpart  = math.floor(codepoint / 0x1000)

      local remainder = codepoint - 0x1000 * highpart

      local midpart   = math.floor(remainder / 0x40)

      local lowpart   = remainder - 0x40 * midpart

      highpart = 0xE0 + highpart

      midpart  = 0x80 + midpart

      lowpart  = 0x80 + lowpart

      --

      -- Check for an invalid character (thanks Andy R. at Adobe).

      -- See table 3.7, page 93, in http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf#G28070

      --

      if ( highpart == 0xE0 and midpart < 0xA0 ) or

         ( highpart == 0xED and midpart > 0x9F ) or

         ( highpart == 0xF0 and midpart < 0x90 ) or

         ( highpart == 0xF4 and midpart > 0x8F )

      then

         return "?"

      else

         return string.char(highpart,

                            midpart,

                            lowpart)

      end

   else

      --

      -- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx

      --

      local highpart  = math.floor(codepoint / 0x40000)

      local remainder = codepoint - 0x40000 * highpart

      local midA      = math.floor(remainder / 0x1000)

      remainder       = remainder - 0x1000 * midA

      local midB      = math.floor(remainder / 0x40)

      local lowpart   = remainder - 0x40 * midB

      return string.char(0xF0 + highpart,

                         0x80 + midA,

                         0x80 + midB,

                         0x80 + lowpart)

   end

end

function OBJDEF:onDecodeError(message, text, location, etc)

   if text then

      if location then

         message = string.format("%s at char %d of: %s", message, location, text)

      else

         message = string.format("%s: %s", message, text)

      end

   end

   if etc ~= nil then

      message = message .. " (" .. OBJDEF:encode(etc) .. ")"

   end

   if self.assert then

      self.assert(false, message)

   else

      assert(false, message)

   end

end

OBJDEF.onDecodeOfNilError  = OBJDEF.onDecodeError

OBJDEF.onDecodeOfHTMLError = OBJDEF.onDecodeError

function OBJDEF:onEncodeError(message, etc)

   if etc ~= nil then

      message = message .. " (" .. OBJDEF:encode(etc) .. ")"

   end

   if self.assert then

      self.assert(false, message)

   else

      assert(false, message)

   end

end

local function grok_number(self, text, start, etc)

   --

   -- Grab the integer part

   --

   local integer_part = text:match('^-?[1-9]%d*', start)

                     or text:match("^-?0",        start)

   if not integer_part then

      self:onDecodeError("expected number", text, start, etc)

   end

   local i = start + integer_part:len()

   --

   -- Grab an optional decimal part

   --

   local decimal_part = text:match('^%.%d+', i) or ""

   i = i + decimal_part:len()

   --

   -- Grab an optional exponential part

   --

   local exponent_part = text:match('^[eE][-+]?%d+', i) or ""

   i = i + exponent_part:len()

   local full_number_text = integer_part .. decimal_part .. exponent_part

   local as_number = tonumber(full_number_text)

   if not as_number then

      self:onDecodeError("bad number", text, start, etc)

   end

   return as_number, i

end

local function grok_string(self, text, start, etc)

   if text:sub(start,start) ~= '"' then

      self:onDecodeError("expected string's opening quote", text, start, etc)

   end

   local i = start + 1 -- +1 to bypass the initial quote

   local text_len = text:len()

   local VALUE = ""

   while i <= text_len do

      local c = text:sub(i,i)

      if c == '"' then

         return VALUE, i + 1

      end

      if c ~= '\\' then

         VALUE = VALUE .. c

         i = i + 1

      elseif text:match('^\\b', i) then

         VALUE = VALUE .. "\b"

         i = i + 2

      elseif text:match('^\\f', i) then

         VALUE = VALUE .. "\f"

         i = i + 2

      elseif text:match('^\\n', i) then

         VALUE = VALUE .. "\n"

         i = i + 2

      elseif text:match('^\\r', i) then

         VALUE = VALUE .. "\r"

         i = i + 2

      elseif text:match('^\\t', i) then

         VALUE = VALUE .. "\t"

         i = i + 2

      else

         local hex = text:match('^\\u([0123456789aAbBcCdDeEfF][0123456789aAbBcCdDeEfF][0123456789aAbBcCdDeEfF][0123456789aAbBcCdDeEfF])', i)

         if hex then

            i = i + 6 -- bypass what we just read

            -- We have a Unicode codepoint. It could be standalone, or if in the proper range and

            -- followed by another in a specific range, it'll be a two-code surrogate pair.

            local codepoint = tonumber(hex, 16)

            if codepoint >= 0xD800 and codepoint <= 0xDBFF then

               -- it's a hi surrogate... see whether we have a following low

               local lo_surrogate = text:match('^\\u([dD][cdefCDEF][0123456789aAbBcCdDeEfF][0123456789aAbBcCdDeEfF])', i)

               if lo_surrogate then

                  i = i + 6 -- bypass the low surrogate we just read

                  codepoint = 0x2400 + (codepoint - 0xD800) * 0x400 + tonumber(lo_surrogate, 16)

               else

                  -- not a proper low, so we'll just leave the first codepoint as is and spit it out.

               end

            end

            VALUE = VALUE .. unicode_codepoint_as_utf8(codepoint)

         else

            -- just pass through what's escaped

            VALUE = VALUE .. text:match('^\\(.)', i)

            i = i + 2

         end

      end

   end

   self:onDecodeError("unclosed string", text, start, etc)

end

local function skip_whitespace(text, start)

   local match_start, match_end = text:find("^[ \n\r\t]+", start) -- [http://www.ietf.org/rfc/rfc4627.txt] Section 2

   if match_end then

      return match_end + 1

   else

      return start

   end

end

local grok_one -- assigned later

local function grok_object(self, text, start, etc)

   if not text:sub(start,start) == '{' then

      self:onDecodeError("expected '{'", text, start, etc)

   end

   local i = skip_whitespace(text, start + 1) -- +1 to skip the '{'

   local VALUE = self.strictTypes and self:newObject { } or { }

   if text:sub(i,i) == '}' then

      return VALUE, i + 1

   end

   local text_len = text:len()

   while i <= text_len do

      local key, new_i = grok_string(self, text, i, etc)

      i = skip_whitespace(text, new_i)

      if text:sub(i, i) ~= ':' then

         self:onDecodeError("expected colon", text, i, etc)

      end

      i = skip_whitespace(text, i + 1)

      local val, new_i = grok_one(self, text, i)

      VALUE[key] = val

      --

      -- Expect now either '}' to end things, or a ',' to allow us to continue.

      --

      i = skip_whitespace(text, new_i)

      local c = text:sub(i,i)

      if c == '}' then

         return VALUE, i + 1

      end

      if text:sub(i, i) ~= ',' then

         self:onDecodeError("expected comma or '}'", text, i, etc)

      end

      i = skip_whitespace(text, i + 1)

   end

   self:onDecodeError("unclosed '{'", text, start, etc)

end

local function grok_array(self, text, start, etc)

   if not text:sub(start,start) == '[' then

      self:onDecodeError("expected '['", text, start, etc)

   end

   local i = skip_whitespace(text, start + 1) -- +1 to skip the '['

   local VALUE = self.strictTypes and self:newArray { } or { }

   if text:sub(i,i) == ']' then

      return VALUE, i + 1

   end

   local text_len = text:len()

   while i <= text_len do

      local val, new_i = grok_one(self, text, i)

      table.insert(VALUE, val)

      i = skip_whitespace(text, new_i)

      --

      -- Expect now either ']' to end things, or a ',' to allow us to continue.

      --

      local c = text:sub(i,i)

      if c == ']' then

         return VALUE, i + 1

      end

      if text:sub(i, i) ~= ',' then

         self:onDecodeError("expected comma or '['", text, i, etc)

      end

      i = skip_whitespace(text, i + 1)

   end

   self:onDecodeError("unclosed '['", text, start, etc)

end

grok_one = function(self, text, start, etc)

   -- Skip any whitespace

   start = skip_whitespace(text, start)

   if start > text:len() then

      self:onDecodeError("unexpected end of string", text, nil, etc)

   end

   if text:find('^"', start) then

      return grok_string(self, text, start, etc)

   elseif text:find('^[-0123456789 ]', start) then

      return grok_number(self, text, start, etc)

   elseif text:find('^%{', start) then

      return grok_object(self, text, start, etc)

   elseif text:find('^%[', start) then

      return grok_array(self, text, start, etc)

   elseif text:find('^true', start) then

      return true, start + 4

   elseif text:find('^false', start) then

      return false, start + 5

   elseif text:find('^null', start) then

      return nil, start + 4

   else

      self:onDecodeError("can't parse JSON", text, start, etc)

   end

end

function OBJDEF:decode(text, etc)

   if type(self) ~= 'table' or self.__index ~= OBJDEF then

      OBJDEF:onDecodeError("JSON:decode must be called in method format", nil, nil, etc)

   end

   if text == nil then

      self:onDecodeOfNilError(string.format("nil passed to JSON:decode()"), nil, nil, etc)

   elseif type(text) ~= 'string' then

      self:onDecodeError(string.format("expected string argument to JSON:decode(), got %s", type(text)), nil, nil, etc)

   end

   if text:match('^%s*$') then

      return nil

   end