ref: ac0f0bec0de9e3923ecb4166c5141b3df1453c2d gemif/README.md -rw-r--r-- 8.0 KiB
ac0f0becNorm MacLennan Have Air restart server when .gemif files change 1 year, 5 months ago


builds.sr.ht status

GemIF is a simple Interactive Fiction engine which runs as a Gemini server.

Check out my live GemIF instance with your favorite gemini client at gemini://gemif.fedi.farm or through a gemini web portal like the one at portal.mozz.us. Though be warned the web portal does terrible things to the ASCII art.



Compiled binaries for several architectures are automatically generated on each tagged commit. You can find the latest one and download it

Otherwise, you can clone this repo and use the regular golang toolchain to build (check the Makefile for details).


Once you have the binary compiled, you need a few files to make it run.

#Step One: Generate your TLS Cert

The first thing to do is generate your TLS cert in whatever way makes sense for you.

In production, you might use certbot in standalone mode to generate a LetsEncrypt cert.

Otherwise, since most (all?) Gemini clients use TOFU for TLS certificates, you can also feel free to generate a self-signed cert in whatever way is appropriate for you.

#Step Two: Gather up your stories

This repo comes with a couple of sample stories in ./stories (also bundled as artifacts alongside the binaries in the releases linked above). If you want to add, remove, or change them, go ahead and do that now (see below for details on writing your own).

#Step Three: Make a config file

GemIF configures itself based on the contents of ./config.toml. Take sample.config.toml and copy it. Change the configuration to match your desired values.

#Run it

That's it. Go ahead and run the binary.

$ ./bin/gemif-linux-amd64/gemif
Starting GemIF 0.1.1 (bd561ac) - built 2020.12.05.210341

[gig-debug] ⇨ gemini server started on [::]:1965
time="2020-12-05T21:29:40-05:00" path=/ status=20 duration=0.28

#Writing Stories

GemIF loads stories from YAML files (from the directory named in engine.stories_dir in config.toml), but authors have the option to write their stories in GemIF format using .gemif files.

#.gemif files and gemifc

.gemif files are a lighweight abstraction on top of the YAML files. Honestly it's still not the most pleasant writing experience, but it's generally better than writing the YAML by hand.

You can see some examples in stories/src/.

Each story directory will contain:

  • metadata.yml - With story and author information
  • An arbitrary number of .gemif files - These files contain the rooms and exits

Each .gemif contains one or more different rooms. Room metadata is presented as YAML frontmatter (or, uh midmatter in the case of multiple rooms in a file) while each description template is presented as plaintext.

# metadata.yml
id: simple
name: Simple Demo
description: A simple demo
author: Norm MacLennan

# room.gemif
room_id: inside
room_name: Inside
- exit_id: leave
  exit_description: You're right, let's seize the day!
  destination_id: outside
You're inside, but it's such a lovely day out.

room_id: outside
room_name: Outside
You made it outside. Now you can get on with your life.


Once you're ready to test your story, you can use gemifc to "compile" it to YAML.

$ gemifc ./path/to/my/story/ ./my/compiled/stories/
Compiling story ./path/to/my/story/ to ./my/compiled/stories/

Finished loading story:
  Name: Simple Demo
  Author: Norm MacLennan
  Descriptions: A simple demo
  Number of Rooms: 2

Serializing and writing to disk...

Then you can load it up with gemif as usual.

#Object specification

Whether you're writing in gemif format or right in a YAML file, here are the object specifications for the things you're building.

metadata comes from the metadata.yml file in gemif format or the metadata key in YAML:

  • id: is a unique id (within your instance) for the story
  • name: is a human-friendly title of the story
  • description: is a brief description of the story
  • author: a name or other identifier of the author(s)

rooms objects are described by your .gemif files or as the rooms object in your YAML.

Each room has:

  • room_id: a story-unique id for the room
  • room_name: a human-readable name
  • room_description: a description of the room
    • in .gemif format this is the plaintext part of each room while the rest of the properties live in the frontmatter
  • exits: an array of exit objects

Each exit contains:

  • exit_description: a description of the exit (the text of the exit link)
  • desination_id: the id of the room this exit takes you to
  • exit_id: a unique id for the exit, I recommend a GUID
  • set_condition: condition tag to attach to the game state if the user takes this exit
  • if_condition: condition tag the user must posses to use this exit
  • not_condition: conditoin tag to the user must NOT posses to use this exit


Conditions are simple tags attached to the user's state. Condition usage will vary from story to story, and some will not require conditions at all, but you might use them to:

  • Track something that has (or has not) happened in the story
  • Track if a user has (or has not) picked up an object
  • Track that the user has said a certain thing to somebody

Conditions are set as part of using exits and can be used to control which exits a user can use in the future as well as used within room descriptions to offer conditional passages.

#Description Templates

Speaking of which, room descriptions are rendered as golang text/template templates with the active gamestate in scope. This allows you to perform a little bit of logic with regards to what you display to the user, how, and when.

The following struct is in scope within your template:

type GameState struct {
	StoryID     string
	CurrentRoom string
	Conditions  []string

StoryID and CurrentRoom (RoomID) probably aren't very interesting, but Conditions can be used to perform conditional rendering.

GameState offers some (currently one) convenience function to help simplify your rendering when it comes to conditions.

ConditionMet(condition string) bool can help you quickly tell if a user meets a specific condition:

- room_id: the_end
  room_name: The End
  room_description: |
    Though because this is a simple demo, you always end up in the same place.

    {{- if .ConditionMet "choice_a"}}

    oh cool, you made choice a! nice work.
    {{- end}}
    {{- if .ConditionMet "choice_b"}}

    oh you made choice b, that's too bad :(
    {{- end}}

#Quick Sample

The sample in the repo contains a walking tour of my home and another contains some examples of the use of conditions. But here's a simpler sample:

- room_id: the_beginning
  room_name: The Beginning
  room_description: >
    This is the beginning of the story!
  - exit_description: This is boring, flip to the end
    destination_id: the_end
    exit_id: exit_a
- room_id: the_end
  room_name: The End
  room_description: >
    And they lived happily ever after.


Hopefully between these two examples, you can get an idea of how you can build simple linear or branching stories.

I plan to continue to extend the features available to offers to add a little more flexibility, but part of the idea is that it's meant to be simple so I'm trying to be careful of how much I add.

Currently focused on refactoring and solidifying the foundation of the application so it is performant and maintainable.


MIT © Norm MacLennan