devjournal

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2021/09/30 takeshi:

Draft:

Expected usage:

1) starting a sip_mrcp stack:

  const sm_stack = sip_mrcp.create(sip_options, rtp_options, mrcp_options, function new_session_callback(session) {
    if(session.resource_type != "speechsynth") {
      session.refuse(400, "Only speechsynth allowed")
      return
    }
    if(!session.offered_payloads.includes("pcmu")) {
      session.refuse(400, "Only pcmu allowed")
      return
    }

    session.accept("pcmu")

    session.on('SOME_EVENT', msg => {
      // do something
    })
  })

  // sip_options: see kirm/sip.js
  // mrcp_options: {local_port} // local_ip should be the same as sip_options.local_ip (as the mrcp server must be reachable)
  // rtp_options: {local_ip, ports}

2) creating a sip_mrcp client session (function create_client_session will add an entry to sessions dictonary)
  sm_stack.create_client_session(options, function new_session_callback(error, session) {
    if(error) {
      console.error(`failed to create session. error: ${error}`)
      return
    }

    session.on('SOME_EVENT', msg => {
      // do something
    })

    //session.payload will contain the accepted payload

    session.send_request(MRCP_REQUEST)
  })

  /* options: {
      server_ip: 'XXXXXX',
      server_port: YYYY
      payloads: LIST_OF_ACCEPTABLE_PAYLOADS
    }
  */

3) refuse incoming session:
   session.refuse(sip_reply_status, sip_reply_reason)

4) accept incoming session:
   session.accept(accepted_payload)
   // the stack should instantiate an rtp_session and answer the SIP call

5) session events:
  - mrcp_msg
  - error
  - data

Implementation:

We will use an actor library and will process events from 3 sources this way:

sip_stack (actor. Will keep a session dictonary):
  server-side:
    - INVITE: 
      - parse and validate SDP (if not valid, refuse the request at this point)
      - create new session_actor and call new_session_callback if set
    - BYE:
      - notify sip_session_terminated
      
  client-side:
    - INVITE Response:
      - 200 OK:
        - parse SDP and confirm it is OK (if not call create_session_callback(error))
        - create rtp_session. on 'error' notify create_session_callback(error) and termiante other entities)
        - create mrcp_socket. on 'error' notify create_session_callback(error) and terminate other_entities)
        - call create_session_callback(null, session) 
    - XXX SIP ERROR:
      - call create_session_callback(error)
    - BYE: 
      - notify sip_session_terminated

mrcp_socket (:
  - error: notify mrcp_error
  - close: notify mrcp_closed
  - data: notify mrcp_msg

rtp_session:
  - error: notify rtp_error
  - data: notify rtp_data


The events above will be notified to the session actor that will handle the events this way:

session_actor:
  - mrcp_closed:
    - notify on('end') subscribers
    - start timer to shutdown
  - mrcp_error:
    - notify on('error') subscribers
    - start timer to shutdown
  - sip_session_terminated: 
    - notify on('end') subscribers
    - start timer to shutdown
  - mrcp_msg:
    - notify on('mrcp_msg') subscribers
  - rtp_error:
    - notify on('error') subscribers
    - start timer to shutdown
  - rtp_data:
    - notify on('rtp_data') subscribers 

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2021/10/03 takeshi:

Thinking about adding pluggable logger to my modules.

But we might think in something generic like middleware:
  https://thecodebarbarian.com/write-your-own-express-from-scratch

Let's follow this:
  https://stackoverflow.com/questions/22335644/best-practice-to-let-users-inject-a-logger-into-nodejs-modules

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2021/10/03 takeshi:

We are getting this error when trying to use magic-globals:

takeshi:sip-mrcp$ node tests/a.js 
/mnt/ssd/work/src/git/MayamaTakeshi/sip-mrcp/node_modules/magic-globals/magic-globals.js:7
Object.defineProperty(global, '__stack', {
       ^

TypeError: Cannot redefine property: __stack
    at Function.defineProperty (<anonymous>)
    at Object.<anonymous> (/mnt/ssd/work/src/git/MayamaTakeshi/sip-mrcp/node_modules/magic-globals/magic-globals.js:7:8)
    at Module._compile (internal/modules/cjs/loader.js:1015:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1035:10)
    at Module.load (internal/modules/cjs/loader.js:879:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Module.require (internal/modules/cjs/loader.js:903:19)
    at require (internal/modules/cjs/helpers.js:74:18)
    at Object.<anonymous> (/mnt/ssd/work/src/git/MayamaTakeshi/sip-mrcp/lib/sip_mrcp_stack.js:1:1)
    at Module._compile (internal/modules/cjs/loader.js:1015:30)

See: https://github.com/gavinengel/magic-globals/pull/7
The PR was not merged yet so I forked the repo and will use it instead or original magic-globals:
  https://github.com/MayamaTakeshi/magic-globals-MODS