Ways to parse JSON in LaTeX?

Question

I'm writing my recipes (food) in a small textfile in JSON. Are there any ways to parse this in LaTeX? I know, that are lots of templates dealing with recipes, but I want to have my own style, which can be change very fast e.g. my mother is not interested in stuff like calories :)

Here is one simple example:

{
"recipe": {
    "title":"First recipe",
    "source":"My first cookbook",
    "carbs":"1 oz",
    "fat":"1 oz",
    "protein":"1 oz",
    "cal":"100 kcal",
    "ingredients": [
        {"item":"Eggs"},
        {"item":"Oil"},
        {"item":"Nuts"}
    ],
    "cooking": [
        {"step":"Mix eggs and oil"},
        {"step":"Add nuts"}
    ]
}
}

Answer 1

Although the question is about parsing JSON in LaTeX, since the OP wants to "have my own style, which can be change very fast", I'll give a ConTeXt solution for its simplicity.

ConTeXt already comes up with a parser for JSON. To use it, simply load

\usemodule[json]

Then, you can use the Lua function utilities.json.tolua to convert JSON string to Lua table and the Lua function utilities.json.tostring to convert a Lua table to a JSON string.

It is very simple to typeset Lua tables using ConTeXt Lua Document. Here is a complete example:

\usemodule[json]
\startluacode

  userdata = userdata or {}
  local json = utilities.json

  userdata.show_recipe = function(recipe)

  local lua_recipe  = json.tolua(recipe).recipe
  local ingredients = lua_recipe.ingredients
  local cooking     = lua_recipe.cooking

  context.subject(lua_recipe.title)

  local show_value = function(value)
    context.NC() context(value) 
    context.EQ() context(lua_recipe[value])
    context.NC() context.NR()
  end

  context.starttabulate()
    show_value("source")
    show_value("carbs")
    show_value("protein")
    show_value("cal")
  context.stoptabulate()

  context.subsubject("Ingredients")
  context.startitemize{"packed, intro"}
  for i = 1,#ingredients do
    context.startitem()
    context(ingredients[i].item)
    context.stopitem()
  end
  context.stopitemize()

  context.subsubject("Cooking")
  context.startitemize{"packed, intro"}
  for i = 1,#cooking do
    context.startitem()
    context(cooking[i].step)
    context.stopitem()
  end
  context.stopitemize()

  end
\stopluacode

Now you can simply define a TeX macro to pass its argument to the Lua function.

% Note that I use the braces around #1 to make the input
% syntax slightly simpler
\define[1]\Recipe
    {\ctxlua{userdata.show_recipe([==[{#1}]==])}}

Let's add some minimal styling to format the section heads. As with all ConTeXt documents, you can change the format by using appropriate \setup... command.

\setuphead[subject][style=\bfb]
\setuphead[subsubject][style=\bfa]

Finally, the main document

\starttext

\Recipe
    {
      "recipe": {
          "title":"First recipe",
          "source":"My first cookbook",
          "carbs":"1 oz",
          "fat":"1 oz",
          "protein":"1 oz",
          "cal":"100 kcal",
          "ingredients": [
              {"item":"Eggs"},
              {"item":"Oil"},
              {"item":"Nuts"}
          ],
          "cooking": [
              {"step":"Mix eggs and oil"},
              {"step":"Add nuts"}
          ]
      }
    } 

\stoptext

which gives

Answer 2

Try this:

\documentclass{scrbook}
\usepackage{luacode}

\begin{filecontents*}{test.json}
{
"recipe": {
    "title":"First recipe",
    "source":"My first cookbook",
    "carbs":"1 oz",
    "fat":"1 oz",
    "protein":"1 oz",
    "cal":"100 kcal",
    "ingredients": [
        {"item":"Eggs"},
        {"item":"Oil"},
        {"item":"Nuts"}
    ],
    "cooking": [
        {"step":"Mix eggs and oil"},
        {"step":"Add nuts"}
    ]
}
}
\end{filecontents*}

\begin{document}



\begin{luacode}
--  We use the lualibs built-in modules
--  this loads all the modules including a json converter
--

local M = M or {}

require("lualibs.lua")


-- @json file
function getjsonfile (file)
    local f, s
      f = io.open(file, 'r')
        s = f:read('*a')
        f.close()
        return s
 end

local s =  utilities.json.tolua(getjsonfile('test.json'))


local rep, write = string.rep, tex.print

function M.inspect (tab, offset)
   local openbracket, closebracket, par = "\\{", "\\mbox{..}\\}", "\\par"

    offset = offset or ""
    for k, v in pairs (tab) do
        local newoffset = offset .. "\\mbox{~~}"
        if type(v) == "table" then
           write(offset .. k .. " = " .. openbracket .. par)
           M.inspect(v, newoffset)
           write(offset .. closebracket .. par)
        else
         if k~="data" then write(offset..k.." =  ".. tostring(v), "\\par") 
           else
                 write(offset.."k = char data ")
           end
       end
    end
end

tex.print(M.inspect(s))
 \end{luacode} 

 \end{document}

It should give you this:

The formatting is done using an inspect method that uses an \mbox{~~} to space the brackets out.

Answer 3

_{As always, I missed David's comment, so my idea is not 100% original. :) As David said in the chatroom, he subliminally gave me a hint, which proves his powers are beyond comprehension, and that ducks aren't noted for their powers of comprehension normally. :)}

Attention: Although my answer works, please favour Yiannis' answer since it uses a module from the standard lualibs available in LuaTeX.

I'll provide a naive answer using LuaTeX just to get things working as quickly as possible. :)

First things first: get this simple JSON encoder/decoder written in pure Lua from Jeffrey Friedl's site. The file is self-contained and it's named JSON.lua. Save to your working directory.

Jeffrey's code is released under a Creative Commons Attribution 3.0 Unported License.

At the very same level, save your JSON file as, say, recipes.json:

{
    "recipe": {
        "title":"First recipe",
        "source":"My first cookbook",
        "carbs":"1 oz",
        "fat":"1 oz",
        "protein":"1 oz",
        "cal":"100 kcal",
        "ingredients": [
            {"item":"Eggs"},
            {"item":"Oil"},
            {"item":"Nuts"}
        ],
        "cooking": [
            {"step":"Mix eggs and oil"},
            {"step":"Add nuts"}
        ]
    }
}

At last, but not least, our TeX file (e.g, recipes.tex):

\documentclass{article}

\usepackage{luacode}

\begin{document}

\begin{luacode}
function read(file)
    local handler = io.open(file, "rb")
    local content = handler:read("*all")
    handler:close()
    return content
end
JSON = (loadfile "JSON.lua")()
local table = JSON:decode(read("recipes.json"))
tex.print(table['recipe']['title'])
\end{luacode}

\end{document}

Run your file with

$ lualatex recipes.tex

The result:

Enjoy! :)