fsm

Finite State Machine library Uses node-graph to work with state graph. Usage info and other docs will follow.

Meanwhile, you can look at test/test.js to see usage example.

Installation

npm install node-fsm

Usage

###new FSM(machineSpec, routerFunc)

machineSpec should contain state graph (nodes and edges like in node-graph). Additional properties are currentState that contains name of current machine state. data contains your arbitrary data tied with fsm.

routerFunc(edge, callback) is async function that checks, whether we made our transition successfully, or not. First argument is an edge object represents state graph edge we attempt to follow (hint: here you can process any arbitrary data you put on edge object in state graph). At the routerFunc completion you should call callback, passing err object, if you encountered any errors, and boolean variable that indicates whether we made transition or not. routerFunc is bound to fsm instance, so you can use this variable to access machine object.

var machineSpec = {
    nodes: [
        {
            name: 'A'
        },
        {
            name: 'B',
            youCanPutArbitraryDataOnYourNodes: { ... }
        }
    ],
    edges: [
        {
            name: 'A->B',
            from: 'A',
            to: 'B',
            youCanPutArbitraryDataOnYourEdgesToo: { ... }
        }
    ],
    currentState: 'A',
    data: { … }
}

var routerFunc = function (edge, callback) {
    // Make any external calls to determine,
    // whether our transition is succesfull or not
    // …
    callback(null, true);
}

var fsm = new FSM(machineSpec, routerFunc);

###availableEdges()

Returns array of edges, that can be followed from current machine state.

    var edges = fsm.availableEdges();
    
    // Returns:
    [
        {
            name: 'A->B',
            from: 'A',
            to: 'B',
            youCanPutArbitraryDataOnYourEdgesToo: { ... }
        }
    ]

###follow(edgeName, callback)

Attempt to change machine state following edge specified by edgeName. Callback should take two arguments (err, status), where err will contain any errors encountered during attempt to change state, and status will contain boolean value indication whether attempt was successful, or not.

Events

emit('state', edge)

When we successfully made a transition to a new state, fsm instance emits 'state' event, passing edge we followed as argument. While edge object contains both from and to fields, you can figure out, what was previous state.

emit('terminal', edge)

When we successfully made a transition to a new state, and this state is terminal (there is no edges outbound for current state) fsm instance emits 'terminal' event, passing edge we followed as argument.