Module:Json

-- -- 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. --

local json = { _version = "0.1.2" }

--- -- 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", c:byte)) end

local function encode_nil(val) 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 ~= #val then error("invalid table: sparse array") end -- Encode for i, 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 '"' .. val:gsub('[%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

local function create_set(...) local res = {} for i = 1, select("#", ...) do   res[ select(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, #str do   if set[str:sub(i, i)] ~= negate then return i   end end return #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 str:sub(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) -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa local f = math.floor if n <= 0x7f then return string.char(n) elseif n <= 0x7ff then return string.char(f(n / 64) + 192, n % 64 + 128) elseif n <= 0xffff then return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128) elseif n <= 0x10ffff then return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,                      f(n % 4096 / 64) + 128, n % 64 + 128) end error( string.format("invalid unicode codepoint '%x'", n) ) end

local function parse_unicode_escape(s) local n1 = tonumber( s:sub(1, 4), 16 ) local n2 = tonumber( s:sub(7, 10), 16 ) -- Surrogate pair? if n2 then return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000) 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 <= #str do   local x = str:byte(j)

if x < 32 then decode_error(str, j, "control character in string")

elseif x == 92 then -- `\`: Escape res = res .. str:sub(k, j - 1) j = j + 1 local c = str:sub(j, j)     if c == "u" then local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1) or str:match("^%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 + #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 .. str:sub(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 = str:sub(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 = str:sub(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 str:sub(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 = str:sub(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 str:sub(i, i) == "}" then i = i + 1 break end -- Read key if str:sub(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 str:sub(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 = str:sub(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 = str:sub(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 <= #str then decode_error(str, idx, "trailing garbage") end return res end

return json