Promise queue

gistfile1.coffee

i = 0
queue = []

rs_command = (cmd) -> -> new Promise (resolve, reject) ->
    post(uri: RSWS_URI, json: cmd)
    .then (result) ->
        errors = get_errors(result[0].body)
        if errors.length
            return reject(errors)
        resolve(result[0].body)
    .catch (err) ->
        reject(err)

consume = ->
    next = ->
        [promise, [resolve, reject]] = queue[0]
        promise()
        .then (result) ->
            resolve(result)
        .catch (err) ->
            reject(err)
        .then ->
            queue.shift()
            if queue.length then next()            
    next()

create: (method, params={}) ->
    method  : method
    params  : params
    jsonrpc : "2.0"
    id      : i++

add = (method, params) ->
    should_consume = not queue.length
    resolver = new Promise (resolve, reject) ->
        queue.push([rs_command(create(method, params)), [resolve, reject]])
    if should_consume then consume()
    resolver

### ----

add("one")
add("two").then (result) ->
    console.log("Care about result? Here's #{result}")
    setTimeout ->
        add("three")
    , 1000