mecano/src/render.coffee.md

Common functions for system deployment.

`render([goptions], options, callback)`
---------------------------------------

Render a template file At the moment, only the
[ECO](http://github.com/sstephenson/eco) templating engine is integrated.

    fs = require 'ssh2-fs'
    each = require 'each'
    misc = require './misc'
    conditions = require './misc/conditions'
    child = require './misc/child'
    write = require './write'

`options`           Command options include:
*   `engine`        Template engine to use, default to "eco"
*   `content`       Templated content, bypassed if source is provided.
*   `source`        File path where to extract content from.
*   `destination`   File path where to write content to or a callback.
*   `context`       Map of key values to inject into the template.
*   `local_source`  Treat the source as local instead of remote, only apply with "ssh" option.
*   `uid`           File user name or user id
*   `gid`           File group name or group id
*   `mode`          File mode (permission and sticky bits), default to `0666`, in the for of `{mode: 0o744}` or `{mode: "744"}`

`callback`          Received parameters are:
*   `err`           Error object if any.
*   `rendered`      Number of rendered files.

If destination is a callback, it will be called multiple times with the
generated content as its first argument.

    module.exports = (goptions, options, callback) ->
      [goptions, options, callback] = misc.args arguments
      misc.options options, (err, options) ->
        return callback err if err
        rendered = 0
        each( options )
        .parallel(goptions.parallel)
        .on 'item', (options, next) ->
          # Validate parameters
          return next new Error 'Missing source or content' unless options.source or options.content
          return next new Error 'Missing destination' unless options.destination
          # Start real work
          do_read_source = ->
            return do_write() unless options.source
            ssh = if options.local_source then null else options.ssh
            fs.exists ssh, options.source, (err, exists) ->
              return next new Error "Invalid source, got #{JSON.stringify(options.source)}" unless exists
              fs.readFile ssh, options.source, 'utf8', (err, content) ->
                return next err if err
                options.content = content
                do_write()
          do_write = ->
            options.source = null
            write options, (err, written) ->
              return next err if err
              rendered++ if written
              next()
          conditions.all options, next, do_read_source
        .on 'both', (err) ->
          callback err, rendered