test.lua

-- -*- coding: utf-8 -*-
--
-- Simple JSON encoding and decoding in pure Lua.
--
-- Copyright 2010-2014 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 above,
-- the web-page links above, and the 'AUTHOR_NOTE' string below are
-- maintained. Enjoy.
--
local VERSION = 20141223.14 -- version history at end of file
local AUTHOR_NOTE = "-[ JSON.lua package by Jeffrey Friedl (http://regex.info/blog/lua/json) version 20141223.14 ]-"

--
-- The 'AUTHOR_NOTE' variable exists so that information about the source
-- of the package is maintained even in compiled versions. It's also
-- included in OBJDEF below mostly to quiet warnings about unused variables.
--
local OBJDEF = {
   VERSION      = VERSION,
   AUTHOR_NOTE  = AUTHOR_NOTE,
}


--
-- Simple JSON encoding and decoding in pure Lua.
-- http://www.json.org/
--
--
--   JSON = assert(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 (from a JSON string to a Lua table)
--
--
--   JSON = assert(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).
--
--
--
-- ERROR HANDLING
--
--   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 original JSON type a
--   particular Lua table was derived from, or guarantee decode-encode
--   round-trip equivalency.
--
--   However, if you enable strictTypes, e.g.
--
--      JSON = assert(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 (from a lua table to a JSON string)
--
--   JSON = assert(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
--   local custom_pretty    = JSON:encode(lua_table_or_value, etc, { pretty = true, indent = "|  ", align_keys = false })
--
--   On error during encoding, this code calls:
--
--     JSON:onEncodeError(message, etc)
--
--   which you can override in your local JSON object.
--
--   The 'etc' in the error call is the second argument to encode()
--   and encode_pretty(), or nil if it wasn't provided.
--
--
-- PRETTY-PRINTING
--
--   An optional third argument, a table of options, allows a bit of
--   configuration about how the encoding takes place:
--
--     pretty = JSON:encode(val, etc, {
--                                       pretty = true,      -- if false, no other options matter
--                                       indent = "   ",     -- this provides for a three-space indent per nesting level
--                                       align_keys = false, -- see below
--                                     })
--
--   encode() and encode_pretty() are identical except that encode_pretty()
--   provides a default options table if none given in the call:
--
--       { pretty = true, align_keys = false, indent = "  " }
--
--   For example, if
--
--      JSON:encode(data)
--
--   produces:
--
--      {"city":"Kyoto","climate":{"avg_temp":16,"humidity":"high","snowfall":"minimal"},"country":"Japan","wards":11}
--
--   then
--
--      JSON:encode_pretty(data)
--
--   produces:
--
--      {
--        "city": "Kyoto",
--        "climate": {
--          "avg_temp": 16,
--          "humidity": "high",
--          "snowfall": "minimal"
--        },
--        "country": "Japan",
--        "wards": 11
--      }
--
--   The following three lines return identical results:
--       JSON:encode_pretty(data)
--       JSON:encode_pretty(data, nil, { pretty = true, align_keys = false, indent = "  " })
--       JSON:encode       (data, nil, { pretty = true, align_keys = false, indent = "  " })
--
--   An example of setting your own indent string:
--
--     JSON:encode_pretty(data, nil, { pretty = true, indent = "|    " })
--
--   produces:
--
--      {
--      |    "city": "Kyoto",
--      |    "climate": {
--      |    |    "avg_temp": 16,
--      |    |    "humidity": "high",
--      |    |    "snowfall": "minimal"
--      |    },
--      |    "country": "Japan",
--      |    "wards": 11
--      }
--
--   An example of setting align_keys to true:
--
--     JSON:encode_pretty(data, nil, { pretty = true, indent = "  ", align_keys = true })
--  
--   produces:
--   
--      {
--           "city": "Kyoto",
--        "climate": {
--                     "avg_temp": 16,
--                     "humidity": "high",
--                     "snowfall": "minimal"
--                   },
--        "country": "Japan",
--          "wards": 11
--      }
--
--   which I must admit is kinda ugly, sorry. This was the default for
--   encode_pretty() prior to version 20141223.14.
--
--
--  AMBIGUOUS SITUATIONS DURING THE ENCODING
--
--   During the encode, if a Lua table being encoded 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 default_pretty_indent  = "  "
local default_pretty_options = { pretty = true, align_keys = false, indent = default_pretty_indent }

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_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 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 new_val, new_i = grok_one(self, text, i)

      VALUE[key] = new_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 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 VALUE_INDEX = 1

   local text_len = text:len()
   while i <= text_len do
      local val, new_i = grok_one(self, text, i)

      -- can't table.insert(VALUE, val) here because it's a no-op if val is nil
      VALUE[VALUE_INDEX] = val
      VALUE_INDEX = VALUE_INDEX + 1

      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

   if text:match('^%s*<') then
      -- Can't be JSON... we'll assume it's HTML
      self:onDecodeOfHTMLError(string.format("html passed to JSON:decode()"), text, nil, etc)
   end

   --
   -- Ensure that it's not UTF-32 or UTF-16.
   -- Those are perfectly valid encodings for JSON (as per RFC 4627 section 3),
   -- but this package can't handle them.
   --
   if text:sub(1,1):byte() == 0 or (text:len() >= 2 and text:sub(2,2):byte() == 0) then
      self:onDecodeError("JSON package groks only UTF-8, sorry", text, nil, etc)
   end

   local success, value = pcall(grok_one, self, text, 1, etc)

   if success then
      return value
   else
      -- if JSON:onDecodeError() didn't abort out of the pcall, we'll have received the error message here as "value", so pass it along as an assert.
      if self.assert then
         self.assert(false, value)
      else
         assert(false, value)
      end
      -- and if we're still here, return a nil and throw the error message on as a second arg
      return nil, value
   end
end

local function backslash_replacement_function(c)
   if c == "\n" then
      return "\\n"
   elseif c == "\r" then
      return "\\r"
   elseif c == "\t" then
      return "\\t"
   elseif c == "\b" then
      return "\\b"
   elseif c == "\f" then
      return "\\f"
   elseif c == '"' then
      return '\\"'
   elseif c == '\\' then
      return '\\\\'
   else
      return string.format("\\u%04x", c:byte())
   end
end

local chars_to_be_escaped_in_JSON_string
   = '['
   ..    '"'    -- class sub-pattern to match a double quote
   ..    '%\\'  -- class sub-pattern to match a backslash
   ..    '%z'   -- class sub-pattern to match a null
   ..    '\001' .. '-' .. '\031' -- class sub-pattern to match control characters
   .. ']'

local function json_string_literal(value)
   local newval = value:gsub(chars_to_be_escaped_in_JSON_string, backslash_replacement_function)
   return '"' .. newval .. '"'
end

local function object_or_array(self, T, etc)
   --
   -- We need to inspect all the keys... if there are any strings, we'll convert to a JSON
   -- object. If there are only numbers, it's a JSON array.
   --
   -- If we'll be converting to a JSON object, we'll want to sort the keys so that the
   -- end result is deterministic.
   --
   local string_keys = { }
   local number_keys = { }
   local number_keys_must_be_strings = false
   local maximum_number_key

   for key in pairs(T) do
      if type(key) == 'string' then
         table.insert(string_keys, key)
      elseif type(key) == 'number' then
         table.insert(number_keys, key)
         if key <= 0 or key >= math.huge then
            number_keys_must_be_strings = true
         elseif not maximum_number_key or key > maximum_number_key then
            maximum_number_key = key
         end
      else
         self:onEncodeError("can't encode table with a key of type " .. type(key), etc)
      end
   end

   if #string_keys == 0 and not number_keys_must_be_strings then
      --
      -- An empty table, or a numeric-only array
      --
      if #number_keys > 0 then
         return nil, maximum_number_key -- an array
      elseif tostring(T) == "JSON array" then
         return nil
      elseif tostring(T) == "JSON object" then
         return { }
      else
         -- have to guess, so we'll pick array, since empty arrays are likely more common than empty objects
         return nil
      end
   end

   table.sort(string_keys)

   local map
   if #number_keys > 0 then
      --
      -- If we're here then we have either mixed string/number keys, or numbers inappropriate for a JSON array
      -- It's not ideal, but we'll turn the numbers into strings so that we can at least create a JSON object.
      --

      if self.noKeyConversion then
         self:onEncodeError("a table with both numeric and string keys could be an object or array; aborting", etc)
      end

      --
      -- Have to make a shallow copy of the source table so we can remap the numeric keys to be strings
      --
      map = { }
      for key, val in pairs(T) do
         map[key] = val
      end

      table.sort(number_keys)

      --
      -- Throw numeric keys in there as strings
      --
      for _, number_key in ipairs(number_keys) do
         local string_key = tostring(number_key)
         if map[string_key] == nil then
            table.insert(string_keys , string_key)
            map[string_key] = T[number_key]
         else
            self:onEncodeError("conflict converting table with mixed-type keys into a JSON object: key " .. number_key .. " exists both as a string and a number.", etc)
         end
      end
   end

   return string_keys, nil, map
end

--
-- Encode
--
-- 'options' is nil, or a table with possible keys:
--    pretty            -- if true, return a pretty-printed version
--    indent            -- a string (usually of spaces) used to indent each nested level
--    align_keys        -- if true, align all the keys when formatting a table
--
local encode_value -- must predeclare because it calls itself
function encode_value(self, value, parents, etc, options, indent)

   if value == nil then
      return 'null'

   elseif type(value) == 'string' then
      return json_string_literal(value)

   elseif type(value) == 'number' then
      if value ~= value then
         --
         -- NaN (Not a Number).
         -- JSON has no NaN, so we have to fudge the best we can. This should really be a package option.
         --
         return "null"
      elseif value >= math.huge then
         --
         -- Positive infinity. JSON has no INF, so we have to fudge the best we can. This should
         -- really be a package option. Note: at least with some implementations, positive infinity
         -- is both ">= math.huge" and "<= -math.huge", which makes no sense but that's how it is.
         -- Negative infinity is properly "<= -math.huge". So, we must be sure to check the ">="
         -- case first.
         --
         return "1e+9999"
      elseif value <= -math.huge then
         --
         -- Negative infinity.
         -- JSON has no INF, so we have to fudge the best we can. This should really be a package option.
         --
         return "-1e+9999"
      else
         return tostring(value)
      end

   elseif type(value) == 'boolean' then
      return tostring(value)

   elseif type(value) ~= 'table' then
      self:onEncodeError("can't convert " .. type(value) .. " to JSON", etc)

   else
      --
      -- A table to be converted to either a JSON object or array.
      --
      local T = value

      if type(options) ~= 'table' then
         options = {}
      end
      if type(indent) ~= 'string' then
         indent = ""
      end

      if parents[T] then
         self:onEncodeError("table " .. tostring(T) .. " is a child of itself", etc)
      else
         parents[T] = true
      end

      local result_value

      local object_keys, maximum_number_key, map = object_or_array(self, T, etc)
      if maximum_number_key then
         --
         -- An array...
         --
         local ITEMS = { }
         for i = 1, maximum_number_key do
            table.insert(ITEMS, encode_value(self, T[i], parents, etc, options, indent))
         end

         if options.pretty then
            result_value = "[ " .. table.concat(ITEMS, ", ") .. " ]"
         else
            result_value = "["  .. table.concat(ITEMS, ",")  .. "]"
         end

      elseif object_keys then
         --
         -- An object
         --
         local TT = map or T

         if options.pretty then

            local KEYS = { }
            local max_key_length = 0
            for _, key in ipairs(object_keys) do
               local encoded = encode_value(self, tostring(key), parents, etc, options, indent)
               if options.align_keys then
                  max_key_length = math.max(max_key_length, #encoded)
               end
               table.insert(KEYS, encoded)
            end
            local key_indent = indent .. tostring(options.indent or "")
            local subtable_indent = key_indent .. string.rep(" ", max_key_length) .. (options.align_keys and "  " or "")
            local FORMAT = "%s%" .. string.format("%d", max_key_length) .. "s: %s"

            local COMBINED_PARTS = { }
            for i, key in ipairs(object_keys) do
               local encoded_val = encode_value(self, TT[key], parents, etc, options, subtable_indent)
               table.insert(COMBINED_PARTS, string.format(FORMAT, key_indent, KEYS[i], encoded_val))
            end
            result_value = "{\n" .. table.concat(COMBINED_PARTS, ",\n") .. "\n" .. indent .. "}"

         else

            local PARTS = { }
            for _, key in ipairs(object_keys) do
               local encoded_val = encode_value(self, TT[key],       parents, etc, options, indent)
               local encoded_key = encode_value(self, tostring(key), parents, etc, options, indent)
               table.insert(PARTS, string.format("%s:%s", encoded_key, encoded_val))
            end
            result_value = "{" .. table.concat(PARTS, ",") .. "}"

         end
      else
         --
         -- An empty array/object... we'll treat it as an array, though it should really be an option
         --
         result_value = "[]"
      end

      parents[T] = false
      return result_value
   end
end


function OBJDEF:encode(value, etc, options)
   if type(self) ~= 'table' or self.__index ~= OBJDEF then
      OBJDEF:onEncodeError("JSON:encode must be called in method format", etc)
   end
   return encode_value(self, value, {}, etc, options or nil)
end

function OBJDEF:encode_pretty(value, etc, options)
   if type(self) ~= 'table' or self.__index ~= OBJDEF then
      OBJDEF:onEncodeError("JSON:encode_pretty must be called in method format", etc)
   end
   return encode_value(self, value, {}, etc, options or default_pretty_options)
end

function OBJDEF.__tostring()
   return "JSON encode/decode package"
end

OBJDEF.__index = OBJDEF

function OBJDEF:new(args)
   local new = { }

   if args then
      for key, val in pairs(args) do
         new[key] = val
      end
   end

   return setmetatable(new, OBJDEF)
end

JSON = OBJDEF:new()

--
-- Version history:
--
--   20141223.14   The encode_pretty() routine produced fine results for small datasets, but isn't really
--                 appropriate for anything large, so with help from Alex Aulbach I've made the encode routines
--                 more flexible, and changed the default encode_pretty() to be more generally useful.
--
--                 Added a third 'options' argument to the encode() and encode_pretty() routines, to control
--                 how the encoding takes place.
--
--                 Updated docs to add assert() call to the loadfile() line, just as good practice so that
--                 if there is a problem loading JSON.lua, the appropriate error message will percolate up.
--
--   20140920.13   Put back (in a way that doesn't cause warnings about unused variables) the author string,
--                 so that the source of the package, and its version number, are visible in compiled copies.
--
--   20140911.12   Minor lua cleanup.
--                 Fixed internal reference to 'JSON.noKeyConversion' to reference 'self' instead of 'JSON'.
--                 (Thanks to SmugMug's David Parry for these.)
--
--   20140418.11   JSON nulls embedded within an array were being ignored, such that
--                     ["1",null,null,null,null,null,"seven"],
--                 would return
--                     {1,"seven"}
--                 It's now fixed to properly return
--                     {1, nil, nil, nil, nil, nil, "seven"}
--                 Thanks to "haddock" for catching the error.
--
--   20140116.10   The user's JSON.assert() wasn't always being used. Thanks to "blue" for the heads up.
--
--   20131118.9    Update for Lua 5.3... it seems that tostring(2/1) produces "2.0" instead of "2",
--                 and this caused some problems.
--
--   20131031.8    Unified the code for encode() and encode_pretty(); they had been stupidly separate,
--                 and had of course diverged (encode_pretty didn't get the fixes that encode got, so
--                 sometimes produced incorrect results; thanks to Mattie for the heads up).
--
--                 Handle encoding tables with non-positive numeric keys (unlikely, but possible).
--
--                 If a table has both numeric and string keys, or its numeric keys are inappropriate
--                 (such as being non-positive or infinite), the numeric keys are turned into
--                 string keys appropriate for a JSON object. So, as before,
--                         JSON:encode({ "one", "two", "three" })
--                 produces the array
--                         ["one","two","three"]
--                 but now something with mixed key types like
--                         JSON:encode({ "one", "two", "three", SOMESTRING = "some string" }))
--                 instead of throwing an error produces an object:
--                         {"1":"one","2":"two","3":"three","SOMESTRING":"some string"}
--
--                 To maintain the prior throw-an-error semantics, set
--                      JSON.noKeyConversion = true
--                 
--   20131004.7    Release under a Creative Commons CC-BY license, which I should have done from day one, sorry.
--
--   20130120.6    Comment update: added a link to the specific page on my blog where this code can
--                 be found, so that folks who come across the code outside of my blog can find updates
--                 more easily.
--
--   20111207.5    Added support for the 'etc' arguments, for better error reporting.
--
--   20110731.4    More feedback from David Kolf on how to make the tests for Nan/Infinity system independent.
--
--   20110730.3    Incorporated feedback from David Kolf at http://lua-users.org/wiki/JsonModules:
--
--                   * When encoding lua for JSON, Sparse numeric arrays are now handled by
--                     spitting out full arrays, such that
--                        JSON:encode({"one", "two", [10] = "ten"})
--                     returns
--                        ["one","two",null,null,null,null,null,null,null,"ten"]
--
--                     In 20100810.2 and earlier, only up to the first non-null value would have been retained.
--
--                   * When encoding lua for JSON, numeric value NaN gets spit out as null, and infinity as "1+e9999".
--                     Version 20100810.2 and earlier created invalid JSON in both cases.
--
--                   * Unicode surrogate pairs are now detected when decoding JSON.
--
--   20100810.2    added some checking to ensure that an invalid Unicode character couldn't leak in to the UTF-8 encoding
--
--   20100731.1    initial public release
--

function lowerkeys(t)
  local tn = {}
  for i,v in pairs(t) do
    local typ = type(i)
    if type(v)=="table" then
      v = lowerkeys(v)
    end
    if typ=="string" then
      tn[i:lower()] = v
    else
      tn[i] = v
    end
  end
  return tn
end

function load()

unitDef = {
  unitname            = [[corsh]],
  name                = [[Dagger]],
  description         = [[Fast Attack Hovercraft]],
  acceleration        = 0.066,
  activateWhenBuilt   = true,
  brakeRate           = 0.0835,
  buildCostEnergy     = 90,
  buildCostMetal      = 90,
  builder             = false,
  buildPic            = [[CORSH.png]],
  buildTime           = 90,
  canAttack           = true,
  canGuard            = true,
  canHover            = true,
  canMove             = true,
  canPatrol           = true,
  category            = [[HOVER]],
  collisionVolumeOffsets = [[0 -2 0]],
  collisionVolumeScales  = [[19 19 36]],
  collisionVolumeTest    = 1,
  collisionVolumeType    = [[cylZ]],  
  corpse              = [[DEAD]],

  customParams        = {
    description_fr = [[Hovercraft d'Attaque Éclair]],
    description_de = [[Schnellangriff Luftkissenboot]],
    description_pl = [[Lekki poduszkowiec]],
    helptext       = [[The Dagger is the hover plant's scout. It provides a cheap, disposable method of getting intel, and can also hit economic targets of opportunity. Its light Gauss gun can also hit underwater targets.]],
    helptext_fr    = [[Le Dagger est petit, maniable, rapide et n'a qu'une faible puissance de feu. Idéal pour les attaques surprises depuis la mer, il surprendra bien des ennemis. Son blindage est cependant trop faible pour faire face r une quelquonque résistance.]],
    helptext_de    = [[Der Dagger ist der Aufklärer unter den Luftkissenbooten. Es bietet dir eine kostengünstige, entbehrliche Möglichkeit deinen Feind frühzeitig um seine Rohstoffquellen zu bringen. Es kann auch U-Booten schiessen.]],
    helptext_pl    = [[Dagger to lekki poduszkowiec, ktory nadaje sie zarowno do zwiadu, jak i atakowania przeciwnika. Jest w stanie atakowac rowniez cele podwodne.]],
  },

  explodeAs           = [[SMALL_UNITEX]],
  footprintX          = 2,
  footprintZ          = 2,
  iconType            = [[hoverraider]],
  idleAutoHeal        = 5,
  idleTime            = 1800,
  mass                = 97,
  maxDamage           = 300,
  maxSlope            = 36,
  maxVelocity         = 4.8,
  minCloakDistance    = 75,
  movementClass       = [[HOVER3]],
  noAutoFire          = false,
  noChaseCategory     = [[TERRAFORM FIXEDWING SUB]],
  objectName          = [[CORSH.s3o]],
  seismicSignature    = 4,
  selfDestructAs      = [[SMALL_UNITEX]],

  sfxtypes            = {

    explosiongenerators = {
      [[custom:HOVERS_ON_GROUND]],
      [[custom:flashmuzzle1]],
    },

  },

  side                = [[CORE]],
  sightDistance       = 450,
  sonarDistance       = 250,
  smoothAnim          = true,
  turninplace         = 0,
  turnRate            = 673,
  workerTime          = 0,

  weapons             = {

    {
      def                = [[GAUSS]],
      badTargetCategory  = [[FIXEDWING]],
      onlyTargetCategory = [[FIXEDWING LAND SINK TURRET SUB SHIP SWIM FLOAT GUNSHIP HOVER]],
    },

  },


  weaponDefs          = {

    GAUSS = {
      name                    = [[Gauss Cannon]],
      alphaDecay              = 0.12,
      areaOfEffect            = 16,
    avoidfeature            = false,
      bouncerebound           = 0.15,
      bounceslip              = 1,
      burst                   = 1,
      cegTag                  = [[gauss_tag_l]],
      craterBoost             = 0,
      craterMult              = 0,

      damage                  = {
        default = 110,
        planes  = 110,
      },
      
      customParams = {
        single_hit = true,
      },

      explosionGenerator      = [[custom:gauss_hit_l]],
      groundbounce            = 1,
      impactOnly              = true,
      impulseBoost            = 0,
      impulseFactor           = 0,
      interceptedByShieldType = 1,
      noExplode               = true,
      noSelfDamage            = true,
      numbounce               = 40,
      range                   = 205,
      reloadtime              = 3,
      rgbColor                = [[0.5 1 1]],
      separation              = 0.5,
      size                    = 0.8,
      sizeDecay               = -0.1,
      soundHit                = [[weapon/gauss_hit]],
      soundHitVolume          = 2.5,
      soundStart              = [[weapon/gauss_fire]],
    soundTrigger            = true,
      soundStartVolume        = 2,
      sprayangle              = 400,
      stages                  = 32,
      turret                  = true,
      waterweapon       = true,
      weaponType              = [[Cannon]],
      weaponVelocity          = 2200,
    },

  },


  featureDefs         = {

    DEAD  = {
      description      = [[Wreckage - Dagger]],
      blocking         = false,
      category         = [[corpses]],
      damage           = 300,
      energy           = 0,
      featureDead      = [[DEAD2]],
      footprintX       = 3,
      footprintZ       = 3,
      height           = [[20]],
      hitdensity       = [[100]],
      metal            = 36,
      object           = [[corsh_dead.s3o]],
      reclaimable      = true,
      reclaimTime      = 36,
      seqnamereclamate = [[TREE1RECLAMATE]],
      world            = [[All Worlds]],
    },


    DEAD2 = {
      description      = [[Debris - Dagger]],
      blocking         = false,
      category         = [[heaps]],
      damage           = 300,
      energy           = 0,
      featureDead      = [[HEAP]],
      footprintX       = 3,
      footprintZ       = 3,
      height           = [[4]],
      hitdensity       = [[100]],
      metal            = 36,
      object           = [[debris3x3c.s3o]],
      reclaimable      = true,
      reclaimTime      = 36,
      seqnamereclamate = [[TREE1RECLAMATE]],
      world            = [[All Worlds]],
    },


    HEAP  = {
      description      = [[Debris - Dagger]],
      blocking         = false,
      category         = [[heaps]],
      damage           = 300,
      energy           = 0,
      footprintX       = 3,
      footprintZ       = 3,
      height           = [[4]],
      hitdensity       = [[100]],
      metal            = 18,
      object           = [[debris3x3c.s3o]],
      reclaimable      = true,
      reclaimTime      = 18,
      seqnamereclamate = [[TREE1RECLAMATE]],
      world            = [[All Worlds]],
    },

  },

}

return lowerkeys({ corsh = unitDef })

end

print(JSON:encode(load()))