State Machine cat

write beautiful state charts

What?

Makes this

from this

initial,
doing: entry/ write unit test
       do/ write code
       exit/ ...,
# smcat recognizes initial
# and final states by name
# and renders them appropriately
final;

initial      => "on backlog" : item adds most value;
"on backlog" => doing        : working on it;
doing        => testing      : built & unit tested;
testing      => "on backlog" : test not ok;
testing      => final        : test ok;

Why

To enable me to make state charts ...

• ... that look good
• ... with the least effort possible
• ... whithout having to interact with drag and drop tools. Entering text
  is fine, doing my own layout is not.
• ... without having to dive into GraphViz dot each time. GraphViz is cool,
  but is was not designed to write & maintain conceptual documents in
  (You'll know what I'm talking about if you ever tried to get it to draw nested nodes. Or edges between those. )

Usage

On line

A no-frills interpreter on line: state-machine-cat.js.org.

Within the Atom editor

There's an Atom package
with syntax highlighting, a previewer and some export options. You can install
it from within Atom (search for state machine cat in the install section
of the settings screen) or use apm i state-machine-cat-preview
if you're a command line person.

OTOH. if you're a command line person the command line interface might be
something for you too:

Command line interface

Just npm install --global state-machine-cat and run smcat

This is what smcat --help would get you:

Usage: smcat [options] [infile]

Options:
  -V, --version               output the version number
  -T --output-type <type>     svg, dot, smcat, json, ast, scxml, scjson (default: "svg")
  -I --input-type <type>      smcat, scxml, json (default: "smcat")
  -E --engine <type>          dot, circo, fdp, neato, osage, twopi (default: "dot")
  -d --direction <dir>        top-down, bottom-top, left-right, right-left (default: "top-down")
  -o --output-to <file>       File to write to. use - for stdout.
  --dot-graph-attrs <string>  graph attributes to pass to the dot render engine
  --dot-node-attrs <string>   node attributes to pass to the dot render engine
  --dot-edge-attrs <string>   edge attributes to pass to the dot render engine
  --desugar                   transform forks and joins into transitions (!experimental!)
  -l --license                Display license and exit
  -h, --help                  output usage information

... so to convert the above chart to sample.svg

bin/smcat docs/sample.smcat

Or, if you'd rather have the native GraphViz dot do that for you:

bin/smcat -T dot docs/sample.smcat -o -, dot -T svg -odoc/sample.svg

Leaving the options at the default settings usually deliver the best
results already, so if they bewilder you: don't worry.

The --dot-graph-attrs (and the node and edge variants thereof) exist in case you want
to override default attributes in the generated picture; e.g. to get a transparent background
and draw edges as line segments instead of splines, use this:

bin/smcat --dot-graph-attrs "bgcolor=transparent splines=line" docs/sample.smcat

When you pass the --desugar (⨻ experimental) switch, state-machine-cat will,
before rendering, transform some pseudo states into transitions - see
de-sugaring state machines for details.

State chart XML (SCXML)

state machine cat can write and read valid core constructs
scxml documents. If you're into that sort
of thing you can read all about it in State Machine Cat and SCXML.

Programmatically

After you npm i 'd state-machine-cat:

const smcat = require("state-machine-cat");

try {
  const lSVGInAString = smcat.render(
    `
            initial => backlog;
            backlog => doing;
            doing => test;
        `,
    {
      outputType: "svg"
    }
  );
  console.log(lSVGInAString);
} catch (pError) {
  console.error(pError);
}

Read more in docs/api.md

The language

Short tutorial

simplest

on => off;

• smcat automatically declares the states. You can explicitly declare
  them if you want them to have more than a name only - see state
  declarations below.

labels

on => off: switch;

UML prescribes to place conditions after events, to place
conditions within squares and to place actions
after a /: from => to: event [conditions]/ actions, e.g. on => off: switch flicked [not an emergency]/ light off;.

You're free to do so, but smcat doesn't check for it. It internally takes
the notation into account, though and if you choose to export to json, scxml
or scjson you'll see them nicely split out.

on => off: switch flicked/
           light off;
off => on: switch flicked/
           light on;

You note that smcat rendered the states in this chart top down instead of
left to right. It did that because we told it so. You can do that too
with --direction on the command line, or in atom by direction -> left to right or direction -> top down from the chart's submenu.

notes

# this is a note
on => off;

state declarations

If you need to define activities (e.g. entry or exit triggers) on
a state, you can explicitly declare the state and put the activites
after a colon:

# yep, notes get rendered here as well
# multiple notes translate into multiple
# lines in notes in the diagram
doing:
  entry/ make a feature branch
  exit/ deploy code on production
  ...;

smcat recognizes the entry/ and exit/ keywords and treats
everything after it on the same line to be the 'body' of the
trigger.

Here too: you're free to use them, but you don't have to.
smcat takes them into account in its internal representation
and uses them in exports to json, scxml and scjson.

state display names

If you want to use a display names that differ from how you
name the states (e.g. if the display names are long),
you can do so by adding a label to them:

on [label="Lamp aan"],
off [label="Lamp uit"];

off => on: on pushed;
on => off: off pushed;

initial and final

When initial or final, is part of a state's name smcat treats
it as the UML 'pseudo states' initial and final respectively:

initial => todo;
todo    => doing;
doing   => done;
done    => final;

history

smcat recognizes states with history in their name als history states:

initial,
"power off",
running {
  running.history;

  washing -> rinsing: 20 min;
  rinsing -> spinning: 20 min;
  spinning -> final: 20 min;
},
final;

initial => washing;
running => "power off": power out;
"power off" => running.history: restore power;

History states are shallow by default. If you want a history state to
be deep just put that somewhere in the name (e.g. "running deep history"
or running.history.deep) - and smcat will render them as such.

Choice - ^

smcat treats states starting with ^ as UML pseudo state choice. Strictly
speaking 'choice' is a superfluous element of the UML state machine
specification, but it is there and sometimes it makes diagrams easier to read.

^fraud?: transaction fraudulent?;

initial -> reserved;
reserved -> quoted:
    quote
    requested;
quoted -> ^fraud?: payment;
^fraud? -> ticketed: [no];
^fraud? -> removed: [yes];
ticketed -> final;
removed -> final;

Forks, joins and junctions - ]

In UML you can fork state transitions into multiple or join them into one
with the fork (one to many) join (many to one) and junction (many to many)
pseudo states. Fork and join are represented by a black bar, junction
by a filled circle.
To make a join, fork or junction pseudo state, start its
name with a ].
Here's an example of a join:

a => ]join;
b => ]join;
]join => c;

State machine cat automatically derives which of the three types
you meant by counting the number of incoming and the number of
outgoing connections:

• one incoming and multiple outgoing: it's a fork
• multiple incoming and one outgoing: it's a join
• all other cases: it's a junction

If you want to defy UML semantics you can do that with
explicit type overrides .

a => ]junction;
b => ]junction;
]junction => c;
]junction => d;

Terminate

UML has a special pseudo state to indicate your state machine didn't
exit properly: terminate. If you want to use it, declare it
explicitly:

Aahnohd [type=terminate label="Terminated"];

a => Aahnohd: [hit by meteorite];

For proper exits you'd typically use the final state.

Gotchas

• when you need ;, ,, {, [ or spaces as part of a state - place em in quotes
  "a state"
• Activities have the same restriction, except they allow spaces.
• Labels have the same restriction as activities, except they allow for , too.
• State declaration precedence is: deep wins from shallow; explicit wins from
  implicit
• It's possible to declare the same state multiple times on the same level, buts
  smcat will take the last declaration into account only. For example:

This

# first declaration of "cool state"
"cool state",
"other state",
# second declaration of "cool state"
"cool state": cool down;

results in (/ is equivalent to):

# second declaration of "cool state"
"cool state": cool down,
"other state";

nested state machines

It's possible to have state machines within states.
the states stopped, playing and pause can only occur when
the tape player is on:

initial,
"tape player off",
"tape player on" {
  stopped => playing : play;
  playing => stopped : stop;
  playing => paused  : pause;
  paused  => playing : pause;
  paused  => stopped : stop;
};

initial           => "tape player off";
"tape player off" => stopped           : power;
"tape player on"  => "tape player off" : power;

parallel states

If stuff is happening in parallel within a state you can express
that too. Just make sure the state has the word "parallel" in there:

initial,
bla.parallel {
    first{
        first.thing -> first.thang;
    },
    second{
        second.thing -> second.thang;
        second.thang -> second.thing;
    };
},
final;

initial -> ]split;
]split  -> first.thing;
]split  -> second.thing;
first.thang  -> ]merge;
second.thang -> ]merge;
]merge  -> final;

internal and external transitions

If you need to mark a transition in a nested state machine as either internal
or external - use the type attribute. The default type for a transition
is external - just like it is in SCXML.

playing {
  resting => walking;
  walking => resting;

};

playing => playing: ingest food;
playing => playing [type=internal]: ingest drink;

marking states active

You can mark one or more states as active by adding active as an
attribute for that state. E.g. to make the do state an active one
in the demming circle, do this:

do [active];

initial -> plan;
plan    -> do;
do      -> study;
study   -> act;
act     -> plan;

which will result in

colors

As of version 4.2.0 state-machine-cat has (experimental) support for colors on both
states and transitions.

For example, this ...

eat   [color="#008800"],
sleep [color="blue" active],
meow  [color="red"],
play  [color="purple"];

sleep -> meow  [color="red"]    : wake up;
meow  -> meow  [color="red"]    : no response from human;
meow  -> eat   [color="#008800"]: human gives food;
meow  -> play  [color="purple"] : human gives toy;
play  -> sleep [color="blue"]   : tired or bored;
eat   -> sleep [color="blue"]   : belly full;

... would yield this diagram:

What does 'experimental' mean?

The color attribute is probably here to stay.

However, I haven't found the balance between ease of use
and expressiveness yet. Should the text in a state be rendered in the same color?
should the background color automatically be rendered as well? In the same color,
or in a shade smartly derived? Or should I include a bunch of color attributes
(e.g. fillcolor, textcolor, textbgcolor) for ultimate control?

overriding the type of a state

As you read above, state machine cat derives the type of a state from its name.
In some cases that might not be what you want. In those cases, you can
override the type with the type attribute, like in this example for the
initialized state.

initial,
starting,
initialized [color="red" type=regular],
running,
final;

initial     => starting;
starting    => initialized;
initialized => running;
initialized => stopped;
running     => stopped;
stopped     => final;

The values you can use for the type of a state:, type, example, -------------, ------------------------------------------------------------------------------------, regular, , initial, , final, , history, , deephistory, , choice, , fork, , join, , forkjoin, , junction, , parallel, , terminate, , #### grammar

I made the parser with pegjs - you can find it at
src/parse/peg/smcat-parser.pegjs

Status

• Thoroughly tested and good enough for public use.
• Despite this you might bump into the occasional issue - don't hesitate to
  report it, either on GitLab
  or on GitHub.
• Runs on latest versions of firefox, safari and chrome and node versions >= 8.
  Although it might run on other environments, it's not tested there. I will
  reject issues on these other environments, unless they're accompanied with
  sufficient enticement to make it worth my while.