Allows you to create software components that you can register, lookup, and combine together at run-time.

Install

npm install scm

Using

Define a scm-config.json file and run scm from the command line (or a boot script).

Some initial documentation can be found here.

About

Simple Component Manager (SCM) is an Inversion of Control framework for node.js that enables late binding through service locator injection and generic-type injection.

Whew. That's a mouthfull. What does it actually mean?

Normally you have to do includes in node.js using require(). If I want to use a database, I have to decide whether I want to require("mongodb") or require("mysql") when I'm writing my code. And if I want to give the user the choice, I have to write some logic around that and include all the options the user might want to use.

SCM turns that upside-down. Rather than doing require() you define components, such as a database component and register them with the ComponentManager (typically things are registered automatically through the scm-config.json). Things that use databases could then call ComponentManager.get("database") and then use the database withouth caring which database is underneath.

This is great for databases, loggers, communication protocols, etc. where there are so many choices, so many religions, and no right answers that the only solution is to offer flexibility.

scm-config.json

The scm-config.json can be located in the local directory, or globally in /etc/scm.

The most important section of the scm-config.json is the components list, which says which components are needed. Each component object in the list has a name, a type, a package and optionally pre-config and post-config settings. Here is an example of a single component declaration:

{
    "name": "http",
    "type": "generic",
    "package": "component-web",
    "pre-config": [{
        "set-port": 8888
    }]
}

This component declares that it is using the component-web component, which we will name "http" (that's the name other components will use to find it). It will install the npm package component-web (any valid package name should work, including package@version and /path/to/a/package). Before the init() function of the component is called, the pre-config says that we should call set-port with 8888.

Here is an example of a full scm-config.json.

// scm-config
//
// this is a JSON file that allows JavaScript-style comments
{
    // setuid and setgid are only required if running with sudo
    // you can delete these lines and run without sudo if your http/https ports don't require special privledges
    // "setuid": 1,
    // "setgid": 1,
    "components": [{
        "name": "http",
        "type": "generic",
        "package": "component-web",
        "pre-config": [{
            "set-port": 8888
        }],
        "post-config": [{
            "set-redirect": {
                "destProtocol": "https",
                "destPort": 8443,
                "destTemporary": false
            }
        }]
    }, {
        "name": "https",
        "type": "generic",
        "package": "component-web",
        "pre-config": [{
            "set-port": 8443,
            "set-https": true,
            "set-domain": "localhost",
            "set-body-parser": "json",
            "set-enable-session": true
        }, { // demo UI for WebAuthn
            "add-static": {
                "path": "/",
                "dir": "webauthn-yubiclone"
            }
        }, { // serve up swagger UI
            "add-static": {
                "path": "/swagger",
                "dir": "fido2-swagger"
            }
        }]
    }, {
        "name": "cert-manager",
        "type": "generic",
        "package": "component-certs-static",
        "pre-config": [{
            "set-cert-file": "data/node_modules/component-certs-static/test/helpers/certs/cert.pem",
            "set-key-file": "data/node_modules/component-certs-static/test/helpers/certs/key.pem"
        }]
    }, {
        "name": "fido2",
        "type": "generic",
        "package": "/Users/apowers/Projects/fido2-stack/component-fido2",
        "pre-config": [{
            "enable-dangerous-open-registration": true,
            "enable-dangerous-xmit-debug-info": true,
            "set-service-name": "WebAuthn.org"
        }]
    }, {
        "name": "uds",
        "type": "generic",
        "package": "/Users/apowers/Projects/components/component-uds-json"
    }, {
        "name": "logger",
        "type": "logger",
        "package": "component-logger-winston",
        "pre-config": [{
            "set-level": "silly",
            "add-transport": [{
                // log to the screen...
                "type": "console",
                "colorize": true
            }, {
                // ...and log to a file
                // see winston's npm page for more transport configuration options
                "type": "file",
                "filename": "scm.log"
            }]
        }]
    }]
}

Custom Components

You can define your own components, which can be really anything (even plain-ole Objects or Functions). For convenience functions, you can use the component-class which also includes a template that shows how to use other components.