Transformations

Transformations is like a shell pipe defined in App Builder. We have a number of transformations and using them is entirely optional - often a shell pipe would be much better.

The reason for adding transformations like jq to App Builder itself is to have it function in places where that 3rd party dependency is not met. Rather than require everyone to install JQ - and handle that dependency, we just add a JQ dialect directly to App Builder.

A basic example of transformations can be seen here:

name: ghd
description: Gets the description of a Github Repo
type: exec
command: |
    curl -s -H "Accept: application/vnd.github.v3+json" https://api.github.com/repos/choria-io/appbuilder

transform:
  jq:
    query: .description

Here we call out a REST API that returns JSON payload using curl and then extract the description field from the result using a JQ transform

$ demo ghd
Tool to create friendly wrapping command lines over operations tools

Not every command supports transforms, so the individual command documentation will call out it out.

JQ Transform

The jq transform uses a dialect of JQ called GoJQ, most of your JQ knowledge is transferable with only slight changes/additions. This is probably the most used transform so there’s a little short cut to make using it a bit easier:

transform:
  query: .description

Is the same as (added in 0.2.0):

transform:
  jq:
    query: .description

The query parameter is all that is supported. The query supports Templating.

Bar Graph Transform

This transform takes a JSON document like {"x": 1, "y": 2} as input and renders bars for the values.

Version Hint

Added in version 0.2.0

Here is an example that draws the sizes of the assets of the latest release:

name: bargraph
description: Draws an ASCII bar graph
type: exec
transform:
  pipeline:
    - jq:
        query: |
                    .assets|map({(.name): .size})|reduce .[] as $a ({}; . + $a)

    - bar_graph:
        caption: "Release asset sizes"
        bytes: true
script: |
    curl -s https://api.github.com/repos/choria-io/appbuilder/releases/latest

This uses a pipeline (see below) to transform a GitHub API request into a hash and then a bar_graph to render it:

$ demo bargraph
Latest release asset sizes

    appbuilder-0.1.1-windows-arm64.zip: ▏ (2.0 MiB)
            appbuilder-0.1.1-arm64.rpm: ██ (2.0 MiB)
   appbuilder-0.1.1-linux-arm64.tar.gz: ███ (2.0 MiB)
            appbuilder-0.1.1-arm64.deb: ███ (2.0 MiB)
     appbuilder-0.1.1-windows-arm7.zip: █████████████ (2.1 MiB)
     appbuilder-0.1.1-windows-arm6.zip: ██████████████ (2.1 MiB)
             appbuilder-0.1.1-arm7.rpm: ██████████████ (2.1 MiB)
             appbuilder-0.1.1-arm7.deb: ███████████████ (2.1 MiB)
    appbuilder-0.1.1-linux-arm7.tar.gz: ███████████████ (2.1 MiB)
             appbuilder-0.1.1-arm6.rpm: ███████████████ (2.1 MiB)
             appbuilder-0.1.1-arm6.deb: ███████████████ (2.1 MiB)
    appbuilder-0.1.1-linux-arm6.tar.gz: ███████████████ (2.1 MiB)
    appbuilder-0.1.1-windows-amd64.zip: ███████████████████████ (2.2 MiB)
  appbuilder-0.1.1-darwin-arm64.tar.gz: █████████████████████████ (2.2 MiB)
           appbuilder-0.1.1-x86_64.rpm: ███████████████████████████ (2.2 MiB)
   appbuilder-0.1.1-linux-amd64.tar.gz: ███████████████████████████ (2.2 MiB)
            appbuilder-0.1.1-amd64.deb: ███████████████████████████ (2.2 MiB)
  appbuilder-0.1.1-darwin-amd64.tar.gz: ████████████████████████████████████████ (2.3 MiB)

The transform supports a few options, all are optional:

OptionDescription
widthThe width of the bar, defaults to 40
captionThe cpation to show above the graph, supports Templating
bytesWhen set to true indicates that the numbers rendered after the bars will be bytes like in the example

Line Graph

This transform takes input of floats per line or a JSON document (array of floats) and turns it into a line graph.

Version Hint

Added in version 0.2.0

Here we find the hourly forecast for our location and graph it:

description: Hourly weather forecast
type: exec
transform:
  pipeline:
    - jq:
        query: |
                    .weather[0].hourly|.[]|.FeelsLikeC
    - line_graph:
        width: 40
        height: 10
        caption: Hourly weather forecast (C)
command: |
    curl -s wttr.in/?format=j1

When run this produces:

$ demo linegraph
 30.00 ┤                      ╭─────╮
 29.90 ┤                     ╭╯     │
 29.80 ┤                    ╭╯      ╰╮
 29.70 ┤                    │        │
 29.60 ┤                   ╭╯        ╰╮
 29.50 ┤                   │          │
 29.40 ┤                  ╭╯          ╰╮
 29.30 ┤                  │            ╰╮
 29.20 ┤                 ╭╯             │
 29.10 ┤                ╭╯              ╰╮
 29.00 ┼────────────────╯                ╰─────
              Hourly weather forecast (C)

The transform supports a few options, all are optional:

OptionDescription
widthThe width of the graph, defaults to 40
heightThe height of the graph, defaults to 20
precisionThe decimal precision to consider and render
jsonWhen true expects JSON input like [1,2,3,4] rather than a float per line
captionThe caption to show above the graph, supports Templating

Templates

The template transform uses Golang templates and the sprig functions to facilitate creation of text output using a template language.

Version Hint

Added in version 0.3.0

name: template
type: exec
description: Demonstrates template processing of JSON input
command: |
    echo '{"name": "James", "surname":"Bond"}'
transform:
  template:
    contents: |
            Hello {{ .Input.name }} {{ .Input.surname | swapcase }}
OptionDescription
contentsThe body of the template embedded in the application yaml file
sourceThe file name holding the template, the file name is parsed using Templating

Writing to a file

Data entering a the write_file transform is written to disk and also returned, but optionally a message can be returned.

name: template
type: exec
description: Demonstrates template processing of JSON input
command: |
    echo '{"name": "James", "surname":"Bond"}'
transform:
  pipeline:
    - write_file:
        file: /tmp/name.txt
        replace: true

    - template:
      contents: |
                Hello {{ .Input.name }} {{ .Input.surname | swapcase }}

Above the /tmp/name.txt would hold the initial JSON data.

If the write_file is the only transform or in a pipeline like here the data received is simply passed on to the next step, this can be annoying when writing large files as they will be dumped to the screen.

transform:
  - write_file:
    file: /tmp/report.txt
    replace: true
    message: Wrote {{.IBytes}} to {{.Target}}

In this case the message Wrote 1.8 KiB to /tmp/report.txt would be printed. You can use .Bytes, .IBytes, .Target and .Contents in the message.

OptionDescription
fileThe file to write, the file name is parsed using Templating
messageA message to emit from the transform instead of the contents recieved by it
replaceSet to true to always overwrite the file

Row orientated Reports

These reports allow you to produce text reports for data found in JSON files. It reports on Array data and produce paginated reports with optional headers and footers.

Version Hint

Added in version 0.3.0

name: report
type: exec
description: Demonstrates using a report writer transform
command: curl -s https://api.github.com/repos/choria-io/appbuilder/releases/latest
transform:
  report:
    name: Asset Report
    initial_query: assets
    header: |+
      @|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
      data.name
      --------------------------------------------------------------------------------      

    body: |
      Name: @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Size: @B###### Downloads: @##
      row.name, row.size,              row.download_count      
    footer: |+2
      
                                                                  ====================
                                                                  Total Downloads: @##
      report.summary.download_count

Here we fetch the latest release information from GitHub and produce a report with header, footer and body. Since the JSON data from GitHub is a object we use the assets GJSON query to find the rows of data to report on.

See the goform project for a full reference to the formatting language.

                                 Release 0.2.1                                  
--------------------------------------------------------------------------------

Name: appbuilder-0.2.1-amd64.deb                   Size: 2.3 MiB  Downloads: 2  
Name: appbuilder-0.2.1-arm6.deb                    Size: 2.2 MiB  Downloads: 0  
Name: appbuilder-0.2.1-arm6.rpm                    Size: 2.1 MiB  Downloads: 0  
....
Name: appbuilder-0.2.1-windows-arm7.zip            Size: 2.1 MiB  Downloads: 0  
Name: appbuilder-0.2.1-x86_64.rpm                  Size: 2.2 MiB  Downloads: 2    

                                                            ====================
                                                            Total Downloads: 20 
OptionDescription
nameThe name of the report, parsed using Templating
headerThe report header
bodyThe report body
footerThe report footer
rows_per_pageHow many rows to print per page, pages each have header and footer
initial_queryThe initial GJSON query to use to find the row orientated data to report
source_fileA file holding the report rather than inline, name, header, body and footer are read from here. File name parsed using Templating

Pipelines

We’ve seen a few example transform pipelines above, like this one here:

Version Hint

Added in version 0.2.0

type: exec
transform:
  pipeline:
    - jq:
        query: |
                    .weather[0].hourly|.[]|.FeelsLikeC
    - line_graph:
        width: 80
        caption: Hourly weather forecast (C)
command: |
    curl -s wttr.in/?format=j1

This runs the output of the curl command (JSON weather forecast data) through a jq transform that produce results like:

29
29
29
29
30
30
29
29

We then feed that data into a line_graph and render it, the output from the jq transform is used as input to the line_graph.

Any failure in the pipeline will terminate processing.