I wanted to see what else people have done in terms of combining Minecraft and Emacs. It turns out that you can control Minecraft from Emacs via mcf if you set enable-rcon=true in your server.properties (also a good idea to set rcon.password) and you configure variables like mcf-rcon-password on the Emacs side. It needed a little tweaking to get it to connect to a remote server, so I've submitted a pull request. Anyway, since Emacs can talk to Minecraft and I can write sequences of Minecraft commands as functions, I thought about turning my Minecraft command books into something that I could update right from Emacs.

Creating my own datapack was pretty straightforward once I figured out the directory structure. I needed to put functions in <world-name>/datapacks/sachac/data/sachac/functions. Inside <world-name>/datapacks/sachac, I created pack.mcmeta with the following contents:

{
    "pack": {
        "pack_format": 10,
        "description": "sachac's tweaks"
    }
}

Inside <world-name>/datapacks/sachac/data/sachac/functions, I created a command_book.mcfunction file with the command to give me the book. I updated my command book function to remove the / from the beginning.

I used /reload to reload my Minecraft configuration and /datapack list to confirm that my datapack was loaded. Then /function sachac:command_book ran the function to give me the command book, so that all worked out. I replaced the command in the command block with the function call.

The next step was to update it directly from Emacs, including reloading. First, I needed a function to give me the filename of a function file.

(defun my-minecraft-datapack-function-file-name (world datapack-name function-name)
  "Return the filename for a mcfunction file given WORLD, DATAPACK-NAME, and FUNCTION-NAME."
  (seq-reduce
   (lambda (path subdir) (expand-file-name subdir path))
   (list "datapacks"
         datapack-name
         "data"
         datapack-name
         "functions"
         (concat function-name ".mcfunction"))
   world))

I used C-c C-x p (org-set-property) to add a WORLD property to my Org subtree. For example, my snapshot world is at /ssh:desktop:~/.minecraft/saves/Snapshot. Then I can get the correct value within the subtree by using org-entry-get-with-inheritance. This is how I wrote the command book function for my snapshot world:

#+begin_src emacs-lisp :var body=mc-snapshot :var team=mc-team :var quick=mc-quick :var effects=mc-effects :var items=mc-items :results silent
(with-temp-file
    (my-minecraft-datapack-function-file-name
     (org-entry-get-with-inheritance "WORLD")
     "sachac"
     "command_book")
  (insert (my-minecraft-book "Commands 8.5" "Mom" (append team quick body effects items))))
(mcf-eval "reload")
#+end_src

So now I can use C-c C-c to execute the Emacs Lisp block and have my Minecraft world updated. Then I just need to right-click on my command block's button or run the function in order to get the new version.

I'm looking forward to learning more about mcfunctions so that I can write a function that automatically replaces the book in everyone's inventories. Could be fun.

A+ likes playing recent Minecraft snapshots because of the new features. The modding systems haven't been updated for the snaphots yet, so we couldn't use mods like JourneyMap to teleport around. I didn't want to be the keeper of coordinates and be in charge of teleporting people to various places.

It turns out that you can make clickable books using JSON. I used the Minecraft book editor to make a prototype book and figure out the syntax. Then I used a command block to give it to myself in order to work around the length limits on commands in chat. A+ loved being able to carry around a book that could teleport her to either of us or to specified places, change the time of day, clear the weather, and change game mode. That also meant that I no longer had to type all the commands to give her water breathing, night vision, or slow falling, or give her whatever tools she forgot to pack before she headed out. It was so handy, W- and I got our own copies too.

Manually creating the clickable targets was annoying, especially since we wanted the book to have slightly different content depending on the instance we were in. I wanted to be able to specify the contents using Org Mode tables and generate the JSON for the book using Emacs.

Here's a screenshot:

This is the code to make it:

(defun my-minecraft-remove-markup (s)
  (if (string-match "^[=~]\\(.+?\\)[=~]$" s)
      (match-string 1 s)
    s))

(defun my-minecraft-book-json (title author book)
  "Generate the JSON for TITLE AUTHOR BOOK.
BOOK should be a list of lists of the form (text click-command color)."
  (json-encode
   `((pages . 
            ,(apply 'vector
                    (mapcar
                     (lambda (page)
                       (json-encode
                        (apply 'vector 
                               (seq-mapcat
                                (lambda (command)
                                  (let ((text (my-minecraft-remove-markup (or (elt command 0) "")))
                                        (click (my-minecraft-remove-markup (or (elt command 1) "")))
                                        (color (or (elt command 2) "")))
                                    (unless (or (string-match "^<.*>$" text)
                                                (string-match "^<.*>$" click)
                                                (string-match "^<.*>$" color))
                                      (list
                                       (append
                                        (list (cons 'text text))
                                        (unless (string= click "")
                                          `((clickEvent 
                                             (action . "run_command")
                                             (value . ,(concat "/" click)))))                                    
                                        (unless (string= color "")
                                          (list (cons 'color
                                                      color))))
                                       (if (string= color "")
                                           '((text . "\n"))
                                         '((text . "\n")
                                           (color . "reset")))))))
                                page))))
                     (seq-partition book 14)
                     )))
     (author . ,author)
     (title . ,title))))

(defun my-minecraft-book (title author book)
  "Generate a command to put into a command block in order to get a book.
Label it with TITLE and AUTHOR.
BOOK should be a list of lists of the form (text click-command color).
Copy the command text to the kill ring for pasting into a command block."
  (let ((s (concat "item replace entity @p weapon.mainhand with written_book"
                   (my-minecraft-book-json title author book))))
    (kill-new s)
    s))

With this code, I can generate a simple book like this:

(my-minecraft-book "Simple book" "sachac"
                   '(("Daytime" "set time 0800")
                     ("Creative" "gamemode creative" "#0000cd")))

item replace entity @p weapon.mainhand with written_book{"pages":["[{\"text\":\"Daytime\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/set time 0800\"}},{\"text\":\"\\n\"},{\"text\":\"Creative\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/gamemode creative\"},\"color\":\"#0000cd\"},{\"text\":\"\\n\",\"color\":\"reset\"}]"],"author":"sachac","title":"Simple book"}

To place it in the world:

1. I changed my server.properties to set enable-command-block=true.
2. In the game, I used /gamemode creative to switch to creative mode.
3. I used /give @p minecraft:command_block to give myself a command block.
4. I right-clicked an empty place to set the block there.
5. I right-clicked on the command block and pasted in the command.
6. I added a button.

Then I clicked on the button and it replaced whatever I was holding with the book. I used item replace instead of give so that it's easy to replace old versions.

On the Org Mode side, it's much nicer to specify commands in a named table. For example, if I name the following table with #+name: mc-quick, I can refer to it with :var quick=mc-quick in the Emacs Lisp source block. (You can check the Org source for this post if that makes it easier to understand.)

(my-minecraft-book "Book from table" "sachac" quick)

item replace entity @p weapon.mainhand with written_book{"pages":["[{\"text\":\"Daytime\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/time set 0800\"}},{\"text\":\"\\n\"},{\"text\":\"Clear weather\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/weather clear\"}},{\"text\":\"\\n\"},{\"text\":\"Creative\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/gamemode creative\"},\"color\":\"#0000cd\"},{\"text\":\"\\n\",\"color\":\"reset\"},{\"text\":\"Survival\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/gamemode survival\"},\"color\":\"#ff4500\"},{\"text\":\"\\n\",\"color\":\"reset\"},{\"text\":\"Spectator\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/gamemode spectator\"},\"color\":\"#228b22\"},{\"text\":\"\\n\",\"color\":\"reset\"}]"],"author":"sachac","title":"Book from table"}

Then I can define several named tables and append them together. Here's one for different effects:

Some commands are pretty long. Specifying a width like <20> in the first row lets me use C-c TAB to toggle width.

Here's what that table looks like in Org Mode:

Here's how to combine multiple tables:

#+begin_src emacs-lisp :results silent :var quick=mc-quick :var effects=mc-effects :var items=mc-items :exports code
(my-minecraft-book "Book from multiple tables" "sachac" (append quick effects items))
#+end_src

Now producing instance-specific books is just a matter of including the sections I want, like a table that has coordinates for different bases in that particular instance.

I thought about making an Org link type for click commands and some way of exporting that will convert to JSON and keep the whitespace. That way, I might be able to write longer notes and export them to Minecraft book JSON for in-game references, such as notes on villager blocks or potion ingredients. The table + Emacs Lisp approach is already quite useful for quick shortcuts, though, and it was easy to write. We'll see if we need more fanciness!