bsl-appcli 3.5.0
A library for adding CLI interfaces to applications in the brightSPARK Labs style.
License: MIT License
Requires Python: >=3.12.3

= BSL Application CLI Library
:toc: left
:toclevels: 4
:sectnums:

https://badge.fury.io/py/bsl-appcli[image:https://badge.fury.io/py/bsl-appcli.svg[PyPI version]]
image:https://github.com/brightsparklabs/appcli/actions/workflows/build_python.yml/badge.svg[Test
Python]
https://github.com/PyCQA/bandit[image:https://img.shields.io/badge/security-bandit-yellow.svg[security: bandit]]

A library for adding CLI interfaces to applications in the brightSPARK Labs style.

== Overview

This library can be leveraged to add a standardised CLI capability to applications to:

* Handle system lifecycle events for services (`service [start|shutdown]`).
* Allow running arbitrary short-lived tasks (`task run`).
* Manage configuration (`configure`).
* Upgrade to a newer version of the application (`upgrade|migrate`).
* And more.

The CLI is designed to run within a Docker container and launch other Docker containers (i.e.
Docker-in-Docker). This is generally managed via a `docker-compose.yml` file.

=== Environment Variables

The library exposes the following environment variables to the `docker-compose.yml` file:

[horizontal]
`APP_VERSION`:: The version of containers to launch.
`<APP_NAME>_CONFIG_DIR`:: The directory containing configuration files.
`<APP_NAME>_DATA_DIR`:: The directory containing data produced/consumed by the system.
`<APP_NAME>_GENERATED_CONFIG_DIR`:: The directory containing configuration files generated from the
templates in `<APP_NAME>_CONFIG_DIR`.
`<APP_NAME>_BACKUP_DIR`:: The directory to use for system backups.
`<APP_NAME>_ENVIRONMENT`:: The deployment environment the system is running in. For example
`production` or `staging`. This allows multiple instances of the application to run on the same
Docker daemon. Defaults to `production`.

NOTE: The `APP_NAME` variable is derived from the `app_name` passed in to the `Configuration`
object in the main python entrypoint to the application. In order for the application to work, the
`app_name` is forced to conform with the shell variable name standard: `[a-zA-Z_][a-zA-Z_0-9]*`.
Any characters that do not fit this regex will be replaced with `_`. See
https://unix.stackexchange.com/questions/428880/list-of-acceptable-initial-characters-for-a-bash-variable[here]
or https://linuxhint.com/bash-variable-name-rules-legal-illegal/[here] for details.

The `docker-compose.yml` can be templated by renaming to `docker-compose.yml.j2`, and setting
variables within the `settings.yml` file as described in the Installation section.

Stack variables can be set within the `stack-settings.yml` file as described in the
`Build configuration template directories` section.

=== Volume Mounts

The following directories are mounted from the host system into the container:

[source,bash]
----
--volume "${INSTALL_DIR}/<environment>/data/cli/home:/root"
--volume "${INSTALL_DIR}/<environment>/conf:/opt/brightsparklabs/<my_app>/<environment>/conf"
--volume "${INSTALL_DIR}/<environment>/conf/.generated:/opt/brightsparklabs/<my_app>/<environment>/conf/.generated"
--volume "${INSTALL_DIR}/<environment>/data:/opt/brightsparklabs/<my_app>/<environment>/data"
--volume "${INSTALL_DIR}/<environment>/backup:/opt/brightsparklabs/<my_app>/<environment>/backup"
----

=== Migration from appcli version &lt;=1.3.6 to version >1.3.6

As a result of supporting application context files, all references to settings in template files
have moved.

All settings in `settings.yml` used in templating are now namespaced under `settings`. All
templates will need to change their references to use this new namespacing scheme. For example, in
templates that refer to settings, change the references like so:

[source]
----
my_app.server.hostname   ->  settings.my_app.server.hostname
my_app.server.http.port  ->  settings.my_app.server.http.port
----

== Quick Start

Refer to the link:QUICKSTART.md[quick start guide] to get a basic application running.

Otherwise refer to the Installation section below to see all options.

== Installation

=== Add the library to your python CLI application

[source,bash]
----
pip install git+https://github.com/brightsparklabs/appcli.git@<VERSION>
----

=== Define the CLI for your application `myapp`

[source,python]
----
# filename: myapp.py

#!/usr/bin/env python3
# # -*- coding: utf-8 -*-

# standard libraries
from pathlib import Path

# vendor libraries
from appcli.cli_builder import create_cli
from appcli.models.configuration import Configuration
from appcli.orchestrators import DockerComposeOrchestrator

# ------------------------------------------------------------------------------
# CONSTANTS
# ------------------------------------------------------------------------------

# directory containing this script
BASE_DIR = Path(__file__).parent

# ------------------------------------------------------------------------------
# PRIVATE METHODS
# ------------------------------------------------------------------------------

def main():
    configuration = Configuration(
        app_name='myapp',
        docker_image='brightsparklabs/myapp',
        seed_app_configuration_file=BASE_DIR / 'resources/settings.yml',
        application_context_files_dir=BASE_DIR / 'resources/templates/appcli/context',
        stack_configuration_file=BASE_DIR / 'resources/stack-settings.yml',
        baseline_templates_dir=BASE_DIR / 'resources/templates/baseline',
        configurable_templates_dir=BASE_DIR / 'resources/templates/configurable',
        orchestrator=DockerComposeOrchestrator(
            # NOTE: These paths are relative to 'resources/templates/baseline'.
            docker_compose_file = Path('docker-compose.yml'),
            docker_compose_override_directory = Path('docker-compose.override.d/'),
            docker_compose_task_file = Path('docker-compose.tasks.yml'),
            docker_compose_task_override_directory = Path( 'docker-compose.tasks.override.d/'),
        ),
        mandatory_additional_data_dirs=['EXTRA_DATA',],
        mandatory_additional_env_variables=['ENV_VAR_2',],
    )
    cli = create_cli(configuration)
    cli()

# ------------------------------------------------------------------------------
# ENTRYPOINT
# ------------------------------------------------------------------------------

if __name__ == '__main__':
    main()
----

Most fields in the appcli constructor can be defaulted, resulting in less code.

[source,python]
----
def main():
    configuration = Configuration(
        app_name='myapp',
        docker_image='brightsparklabs/myapp',
    )
    cli = create_cli(configuration)
    cli()
----

=== Choose orchestrator

==== DockerComposeOrchestrator

This is the default orchestrator. It is designed for launching services via a `docker-compose.yml`
file.

==== NullOrchestrator

For applications with no services to orchestrate, the `NullOrchestrator` can be used. This is
useful for appcli applications which consist only of the launcher container containing various
additional CLI command groups. The `NullOrchestrator` disables commands related to managing
services.

[source,python]
----
from appcli.orchestrators import NullOrchestrator

orchestrator = NullOrchestrator()
----

==== HelmOrchestrator

The project also includes a https://helm.sh/docs/intro/quickstart/[helm] orchestrator for deploying
charts to https://kubernetes.io/[kubernetes] clusters.

Create a new `resources` directory as follows:

[source,bash]
----
resources/
├── settings.yml
└── templates/
   ├── baseline/
   │  └── cli/
   │     └── helm/
   │        ├── set-files/
   │        │  ├── baz/
   │        │  │  ├── foo.json
   │        │  │  └── qux.waldo.txt
   │        │  └── thud.bang.yml
   │        ├── set-values/
   │        │  ├── foo.yml
   │        │  └── bar.txt
   │        └── mychart.tgz
   └── configurable/
      └── cli/
         └── home/
            └── .kube/
               └── config  # Overwrite this with a cluster specific config file. ie `~/.kube/config`.
----

You can then configure the orchestrator as folows:

[source,python]
----
from appcli.orchestrators import HelmOrchestrator

orchestrator = HelmOrchestrator(
    # Chart archive path (relative to `conf/templates/`).
    # [Optional] Default is `cli/helm/chart`
    chart_location="cli/helm/mychart.tgz",

    # The directory containing all main `values.yaml` files (relative to `conf/templates/`).
    # [Optional] Default is `cli/helm/set-values`
    helm_set_values_dir="cli/helm/set-values"

    # The directory containing all key-specific files (relative to `conf/templates/`).
    # [Optional] Default is `cli/helm/set-files`
    helm_set_files_dir="cli/helm/set-files"
)
----

===== Values

Values can be supplied either:

[arabic]
. For a set key by placing files in `set-files` directory.
* The name of the key to set is derived from the directory structure and the name of the file (up to
the first dot encountered in the filename).
. Globally for any files dumped in the `set-values` directory.

For example, given the following `cli/helm/` directory structure:

[source,bash]
----
cli/helm/
├── set-files/
│  ├── baz/
│  │  ├── foo.json
│  │  └── qux.waldo.txt
│  └── thud.bang.yml
└── set-values/
   ├── foo.yml
   └── bar.txt
----

This would result in the following arguments being passed to helm:

[source,bash]
----
--set-file baz.foo=cli/helm/set-files/baz/foo.json
--set-file baz.qux=cli/helm/set-files/baz/qux.waldo.yml    # NOTE: Key is `qux` not `qux.waldo`.
--set-file thud=cli/helm/set-files/thud.bang.yml           # NOTE: Key is `thud` not `thud.bang`.
--values cli/helm/set-values/foo.yml
--values cli/helm/set-values/bar.yml
----

===== Dev Mode Chart

During development it would be slow to require packaging up the chart for any changes. Appcli
provides a way to speed up development by allow for the chart to deployed directly from source. This
is done by specifying the dev chart as an environment variable.

[source,bash]
----
MYAPP_DEV_MODE=true MYAPP_DEV_MODE_HELM_CHART=/path/to/mychart python3 -m myapp service start
----

===== Kubeconfig

A custom `kubeconfig` file can be used by specifying the `KUBECONFIG` environment variable.

[source,bash]
----
KUBECONFIG=/opt/brightsparklabs/myapp/conf/.generated/config ./myapp ...
----

NOTE: The `KUBECONFIG` file must be at a location which is mounted into the launch container. Refer
to link:#volume-mounts[Volume Mounts] for details on what volumes are mounted into the launch
container.

=== Add configuration files

Any configuration files used by your services can be templated using the Jinja2 templating engine.

* Store any Jinja2 variable definitions you wish to use in your configuration template files in
`resources/settings.yml`.
* Store any application context files in `resources/templates/appcli/context/`.
* Store any appcli stack specific keys in `resources/stack-settings.yml`.
* Store your `docker-compose.yml`/`docker-compose.yml.j2` file in
`resources/templates/baseline/`.
* Configuration files (Jinja2 compatible templates or otherwise) can be stored in one of two
locations:
** `resources/templates/baseline` - for templates which the end user *is not* expected to modify.
** `resources/templates/configurable` - for templates which the end user is expected to modify.

==== Application context files

Template files are templated with Jinja2. The '`data`' passed into the templating engine is a
combination of the `settings.yml` and all application context files (stored in
`resources/templates/appcli/context`, and referenced in the `Configuration` object as
`application_context_files_dir`). Application context files that have the extension `.j2` are
templated using the settings from `settings.yml`.

These are combined to make the data for templating as follows:

[source,json]
----
{
  "settings": {
    ... all settings from `settings.yml`
  },
  "application": {
    <app_context_file_1>: {
      ... settings from `app_context_file_1.yml`, optionally jinja2 templated using settings from `settings.yml`
    },
    ... additional app_context_files
  }
}
----

As a minimal example with the following YAML files:

[source,yaml]
----
# ./settings.yml
main_settings:
  abc: 123

# ./resources/templates/appcli/context/app_constants.yml
other_settings:
  hello: world

# ./resources/templates/appcli/context/app_variables.yml.j2
variables:
  main_abc_setting: {{ settings.main_settings.abc }}
----

The data for Jinja2 templating engine will be:

[source,json]
----
{
  "settings": {
    "main_settings": {
      "abc": 123
    }
  },
  "application": {
    "app_constants": {
      "other_settings": {
        "hello": "world"
      }
    },
    "app_variables": {
      "variables": {
        "main_abc_setting": 123
      }
    }
  }
}
----

==== Schema validation

Configuration files will be automatically validated against provided schema files whenever
`configure apply` is run. Validation is done with https://json-schema.org/[jsonschema] and is only
available for `yaml/yml` and `json/jsn` files. The JSON schema file must match the name of the
file to validate with a suffix of `.schema.json.`. It must be placed in the same directory as the
file to validate, The `settings.yml`, `stack_settings.yml` file, and any files in the
`resource/templates` or `resources/overrides` directory can be validated.

[source,yaml]
----
# resources/templates/configurable/my-config.yml
foobar: 5
----

[source,json]
----
# resources/templates/configurable/my-config.yml.schema.json
{
    "$schema": "http://json-schema.org/schema",
    "type": "object",
    "properties" : {
        "foobar" : {"type": "number"}
    }
}
----

To stop a schema file from being copied across to the `generated` config directory, add
`.appcli` as an infix.

[source,bash]
----
$ ls -1
bar.json                     # -> Config-file ; Copy-on-apply
bar.json.schema.json         # -> Schema-file ; Copy-on-apply
foo.yaml                     # -> Config-file ; Copy-on-apply
foo.yaml.appcli.schema.json  # -> Schema-file ; Ignore-on-apply
----

==== Secrets management

IMPORTANT: Currently only supported for the `DockerComposeOrchestrator`. Secret management is
currently not available for the `HelmOrchestrator`. Any secret objects should be pre-loaded in the
Kubernetes cluster.

Sensitive values can be encrypted inside the `settings.yml` file and then decrypted during
deployment within the `docker-compose.yml`.

[source,bash]
----
# Automatically encrypt and set (spaces to prevent shell history retention).
$   ./myapp configure set -e 'path.to.field' 'my-secret-value'

# Manually encrypt and set (spaces to prevent shell history retention).
$  ./myapp encrypt 'my-secret-value'
enc:id=X:...

# Set the above value to the field.
./myapp configure set 'path.to.field' 'enc:id=X:...'
----

On template generation, the encrypted values from the `settings.yaml` file are used verbatim in
the generated files (i.e. the generated files will contain `enc:id=X:...`). Thus, any encrypted
value comes through verbatim in the file present on disk (i.e. remains encrypted on disk).

In the appcli container, the `DockerComposeOrchestrator` has special handling when it processes
the `docker-compose.yml` file:

. The `docker-compose.yml` file (and any override files) are decrypted and written to a temporary
file WITHIN the container.
. These decrypted files and then used in the context of any `docker-compose` commands to manage
the stack.
. So relevant env vars / secrets will go through into any containers as defined in the
`docker-compose.yml` file.
. The decrypted docker compose file disappears when the container shuts down.

IMPORTANT: The secrets are only decrypted in the `docker-compose.yml` (and overrides) files. If
they are used in any other configuration file, they will not be decrypted.

The pattern is to pass secret values into required containers using the `docker-compose.yml` file
via environment variables:

[source,bash]
----
$ cat docker-compose.yml

...

services:
    postgres:
        image: postgres:lastest
        environment:
            - POSTGRES_DB=mydatbase
            - POSTGRES_USER=myuser
            - POSTGRES_PASSWORD={{ myapp.postgres.password }}
        ...


$  ./myapp configure set -e 'myapp.postgres.password' 'my-secret-value'
----

There might be some use cases where secrets need to be printed to the terminal (development for example).
`appcli` provides a logging function to accomodate this, which provides the following benefits.

- The secret value is encoded in base 64.
- It will not be written to a log file, even if a handler is attached.

[source,python]
----
from appcli.logger import logger

some_password = os.getenv("SOME_PASSWORD")
logger.sensitive("Password", some_password)
----

This will print the following message to `stderr`:

[source,bash]
----
$ ./myapp log-secret
[SENSITIVE] Password: "cEBzc3dvcmQxMjM="  # "p@ssword123" encoded as Base64
----

IMPORTANT: This function will not protect against Linux shell redirects.

[source,bash]
----
./myapp log-secret 2> file.log  # Secret value will be written to file!!!
----

=== Configure application backup

Appcli’s `backup` command creates backups of configuration and data of an application, stored
locally in the backup directory. The settings for backups are configured through entries in a
`backups` block in `stack-settings.yml`.

The available keys for entries in the `backups` block are:

[horizontal]
name:: The name of the backup. Must be unique between backup definitions and use `kebab-case`.
backup_limit:: The number of local backups to keep. Set to `0` to disable rolling deletion.
file_filter:: The file_filter contains lists of glob patterns used to specify what files to include
or exclude from the backup.
frequency:: The cron-like frequency at which backups will execute.
+
IMPORTANT: The `minute` and `hour` portions of the cron expression are omitted, as that level of
granularity is not supported. Refer to <<Frequency>> for details.
remote_backups:: The list of remote backup strategies.


[source,yaml]
----
# filename: stack-settings.yml

backups:
  - name: "full"
    backup_limit: 0
    file_filter:
      data_dir:
        include_list:
        exclude_list:
      conf_dir:
        include_list:
        exclude_list:
    frequency: "* * *"
    remote_backups:
----

==== Backup name

The backup `name` is a short descriptive name for the backup definition. To avoid problems, we
_highly_ recommend `name` be:

* Unique between items in the `backups` list.
* Use `kebab-case`.

Examples of good names:

* `full`
* `conf-only`
* `audit-logs`

Without a unique `name`, backups from different items in `backups` will overwrite each other
without warning.

Using `kebab-case` is necessary to avoid some issues with `click` and filesystem naming issues.

When using the `backup` command, you are able to supply the name of the backup to run. If you have
a backup `name` with a space in it, the `click` library cannot interpret the name as a whole
string (even with quotes), so you will be unable to run the backup individually.

If the backup `name` doesn’t use `kebab-case`, it may use some characters that are incompatible
with file and directory naming conventions. Appcli will automatically slugify the name to something
compatible, but this may cause collisions in the folder names of backups to be taken which will lead
to backups being overwritten. e.g. `s3#1` and `s3&1` will both translate internally to `s3-1`.

==== Backup limit

A rolling deletion strategy is used to remove local backups, in order to keep `backup_limit`
number of backups.

If more than `backup_limit` number of backups exist in the backup directory, the oldest backups
will be deleted.

Set this value to `0` to keep all backups.

==== File filter

The `file_filter` block enables filtering of files to backup from `conf` and `data`
directories. For more details including examples, see link:README_BACKUP_FILE_FILTER.adoc[here].

[source,yaml]
----
# filename: stack-settings.yml

# Includes all log files from data dir only.
backups:
  - name: "full"
    backup_limit: 0
    file_filter:
      data_dir:
        include_list:
          - "**/*.log"
        exclude_list:
        conf_dir:
          include_list:
          exclude_list:
            - "**/*"
    frequency: "* * *"
    remote_backups:
----

==== Frequency

Appcli supports limiting individual backups to run on only specific days using a cron-like frequency
filter.

When the `backup` command is run, each backup strategy will check if the `frequency` pattern
matches today’s date. Only strategies whose `frequency` pattern match today’s date will execute.

The input pattern `pattern` is prefixed with `"* * "` and is used as a standard cron expression
to check for a match. i.e. `"* * $pattern"`. This is because `minute` and `hour` granularity are not
configurable.

Examples:

* `"* * *"` (cron equivalent `"* * * * *"`) will always run.
* `"* * 0"` (cron equivalent `"* * * * 0"`) will only run on Sunday.
* `"1 */3 *"` (cron equivalent `"* * 1 */3 *"`) will only run on the first day-of-month of every
3rd month.

==== Remote backup

Appcli supports pushing local backups to remote storage. The list of strategies for pushing to
remote storage are defined within the `remote_backups` block.

The available keys for every remote backup strategy are:

[horizontal]
name:: A short name or description used to describe this backup.
strategy_type:: The type of this backup, must match an implemented remote backup strategy.
frequency:: The cron-like frequency at which remote backups will execute. Behaves the same as local
backup `frequency`.
configuration:: Custom configuration block that is specific to each remote backup strategy.

IMPORTANT:: Remote backups will only run for a local backup that has run. Therefore the `frequency`
of the local backup will apply first, followed by the `frequency` of the remote backup. This means
that it’s possible to write a remote backup frequency that will never execute. e.g. Local `* * 0`
and remote `* * 1`.

===== Strategies

====== AWS S3 remote strategy

To use S3 remote backup, set `strategy_type` to `S3`. The available configuration keys for an S3
backup are:

[horizontal]
bucket_name:: The name of the bucket to upload to.
access_key:: The AWS Access key ID for the account to upload with.
secret_key:: The AWS Secret access key for the account to upload with. The value _must_ be encrypted
using the appcli `encrypt` command.
bucket_path:: The path in the S3 bucket to upload to. Set this to an empty string to upload to the
root of the bucket.
tags:: Key value pairs of tags to set on the backup object.

[source,yaml]
----
# filename: stack-settings.yml

backups:
  - name: "full_backup"
    backup_limit: 0
    remote_backups:
    - name: "weekly_S3"
      strategy_type: "S3"
      frequency: "* * 0"
      configuration:
        bucket_name: "aws.s3.bucket"
        access_key: "aws_access_key"
        secret_key: "enc:id=1:encrypted_text:end"
        bucket_path: "bucket/path"
        tags:
          frequency: "weekly"
          type: "data"
----

==== Restoring a remote backup

To restore from a remote backup:

. Acquire the remote backup (`.tgz` file) that you wish to restore. For S3 this can be done by
downloading the backup from the specified bucket.
. Place the backup `myapp_date.tgz` file in the backup directory. By default this will be
`/opt/brightsparklabs/${APP_NAME}/production/backup/`
. Confirm that appcli can access the backup by running the `view-backups` command
. Run the restore command `./myapp restore BACKUP_FILE.tgz` e.g.
`./myapp restore APP_2021-02-02T10:55:48+00:00.tgz`. The restore process will trigger a backup.

=== (Optional) Define Custom Commands

You can specify some custom top-level commands by adding click commands or command groups to the
configuration object. Assuming '`web`' is the name of the service in the docker-compose.yml file
which you wish to exec against, we can create three custom commands in the following example:

* `myapp ls-root` which lists the contents of the root directory within the `web` service
container and prints it out.
* `myapp ls-root-to-file` which lists the contents of the root directory within the `web`
service container and dumps to file within the container.
* `myapp tee-file` which takes some text and `tee`s it into another file the `web` service
container.

[source,python]
----
def get_ls_root_command(orchestrator: DockerComposeOrchestrator):
    @click.command(
        help="List files in the root directory",
    )
    @click.pass_context
    def ls_root(ctx: click.Context):

        # Equivalent command within the container:
        # `ls -alh`
        cli_context: CliContext = ctx.obj
        output: CompletedProcess = orchestrator.exec(cli_context, "web", ["ls", "-alh", "/"])
        print(output.stdout.decode())

    return ls_root

def get_tee_file_command(orchestrator: DockerComposeOrchestrator):
    @click.command(
        help="Tee some text into a file",
    )
    @click.pass_context
    def tee_file(ctx: click.Context):

        # Equivalent command within the container:
        # `echo "Some data to tee into the custom file" | tee /ls-root.txt`
        cli_context: CliContext = ctx.obj
        output: CompletedProcess = orchestrator.exec(cli_context, "web", ["tee", "/my_custom_file.txt"], stdin_input="Some data to tee into the custom file")

    return tee_file

def get_ls_root_to_file_command(orchestrator: DockerComposeOrchestrator):
    @click.command(
        help="List files in the root directory and tee to file",
    )
    @click.pass_context
    def ls_root_to_file(ctx: click.Context):

        # Equivalent command within the container:
        # `ls -alh | tee /ls-root.txt`
        cli_context: CliContext = ctx.obj
        output: CompletedProcess = orchestrator.exec(cli_context, "web", ["ls", "-alh", "/"])
        data = output.stdout.decode()
        orchestrator.exec(cli_context, "web", ["tee", "/ls-root.txt"], stdin_input=data)

    return ls_root_to_file

def main():
    orchestrator = DockerComposeOrchestrator(Path("docker-compose.yml"))
    configuration = Configuration(
        app_name="appcli_nginx",
        docker_image="thomas-anderson-bsl/appcli-nginx",
        seed_app_configuration_file=Path(BASE_DIR, "resources/settings.yml"),
        stack_configuration_file=Path(BASE_DIR, "resources/stack-settings.yml"),
        baseline_templates_dir=Path(BASE_DIR, "resources/templates/baseline"),
        configurable_templates_dir=Path(BASE_DIR, "resources/templates/configurable"),
        orchestrator=orchestrator,
        custom_commands={get_tee_file_command(orchestrator),get_ls_root_command(orchestrator),get_ls_root_to_file_command(orchestrator)}
    )
    cli = create_cli(configuration)
    cli()
----

=== (Optional) Define hooks

Custom logic can be inserted into the lifecycle by defining the `hooks` parameter in the
`Configuration` object:

[source,python]
----
from secrets import token_urlsafe
from appcli.models.configuration import Hooks


def get_hooks() -> Hooks:
    def post_configure_init(ctx: click.Context):
    """Automatically generate random passwords after `configure init` runs."""

    cli_context = ctx.obj
    configure_cli = cli_context.commands["configure"]

    for setting in [
        "myapp.services.api.password",
        "myapp.services.database.password",
        "myapp.services.cache.password",
    ]:
        logger.info(f"Generating random password for: {setting}")
        ctx.invoke(
            configure_cli.commands["set"],
            type="str",
            encrypted=True,
            setting=setting,
            value=token_urlsafe(20),
        )

    def migrate_variables(
        cli_context: CliContext,
        current_variables: Dict[str, Any],
        previous_version: str,
        clean_new_version_variables: Dict[str, Any],
    ) -> Dict[str, Any]:
        logger.info(
            f"Migrating myapp `{previous_version}` to `{cli_context.app_version}` ..."
        )

        # Handle migration from schema v1 to v2.
        if current_variables['metadata']['schema_version'] == 1:
            current_variables['metadata']['schema_version'] = 2
            # `proxy` key was added in v2.
            current_variables['myapp']['proxy'] = clean_new_version_variables['myapp']['proxy']

        return current_variables

    ...

    return Hooks(
        post_configure_init=post_configure_init,
        migrate_variables=migrate_variables,
        ...
    )

...

def main():
    configuration = Configuration(
        app_name="myapp",
        docker_image="brightsparklabs/myapp',
        hooks=get_hooks()
    )
    cli = create_cli(configuration)
    cli()
----

The various hooks are documented in the `Hooks` class within
link:appcli/models/configuration.py[the configuration.py] file.

They generally allow for code to be run pre/post various lifecycle steps. E.g.
`pre_configure_init` would run the hook prior to the `configure init` stage.

Two hooks of note are:

. `migrate_variables` - Used to handle schema migrations of the `settings.yml` file.
. `is_valid_variables` - Used to validate whether a current `settings.yml` file can be used by
the current version of the system.

=== (Optional) Preset Configurations

The `configure init` command initialises the install location with the configuration templates
from the `configurable_templates_dir`.

In some instances, it is useful to be able to tweak these files for various preset scenarios. E.g.
If a system is deployed on-premise it might enable a set of local services which are not needed if
the system if deployed to a cloud environment.

`appcli` support defining `presets` to support this use case. This is done by having configuring
the `PresetConfiguration` block of the project.

[source,python]
----
configuration = Configuration(
    ...
    auto_configure_on_install=False,
    presets=PresetsConfiguration(
        is_mandatory=True,  # [Optional] Whether to support/enforce presets.
        templates_directory="resources/templates/presets",  # [Optional] Path to the preset dirs.  
        default_preset="onprem", # [Optional] The preset to apply when not is specified.
    ),
)
----

The `templates_directory` must contain a directory for each preset, and contain any files which
should be overriden from the default `configurable` directory. E.g. the below would ensure the
various presets all override the default `environment.txt` file.

[source,bash]
----
resources/templates/
├── baseline/
├── configurable/
│  ├── basefile.yml
│  └── environment.txt
└── presets/
   ├── aws/
   │  ├── additional_dir/
   │  │  └── nested_file.yml
   │  ├── additional_file.yml
   │  └── environment.txt
   ├── azure/
   │  └── environment.txt
   └── onprem/
      └── environment.txt
----

The `preset` can the be specified when initialising the configuration directory:

[source,bash]
----
./myapp configure init --preset aws
----

This will do the following:

[arabic]
. All the files in the `configurable_templates_dir` (e.g. `resources/templates/configurable/`)
will be copied to the installation directory as per usual.
. All files from the `aws` preset will be copied over to the installation directory, overwriting
any existing files with the same name.

[source,bash]
----
/opt/brightsparklabs/myapp/production/conf/templates/
├── basefile.yml           # Comes from `configurable/`.
├── additional_dir/        # Comes from `presets/aws/`.
│  └── nested_file.yml     # Comes from `presets/aws/`.
├── additional_file.yml    # Comes from `presets/aws/`.
└── environment.txt        # Comes from `presets/aws/`.
----

==== Configure Init Hooks

Any `{pre,post}_configure_init` hooks will inherit the profile parameter supplied at runtime.

[source,python]
----
def post_configure_init_hook(ctx: click.Context, preset: Optional[str]):
  # `preset` will be `--preset <value>` or `None` if no parameter was supplied.
  pass
----

=== Define a container for your CLI application

[source]
----
# filename: Dockerfile

FROM brightsparklabs/appcli-docker-compose:<version>

ENTRYPOINT ["./myapp.py"]
WORKDIR /app

# install compose if using it as the orchestrator
RUN pip install docker-compose

COPY requirements.txt .
RUN pip install --requirement requirements.txt
COPY src .

ARG APP_VERSION=latest
ENV APP_VERSION=${APP_VERSION}
----

==== Build the container

[source,bash]
----
# sh
docker build -t brightsparklabs/myapp --build-arg APP_VERSION=latest .
----

==== (Optional) Login to private Docker registries and pass through credentials

It is possible to login to private Docker registries on the host, and pass through credentials to
the CLI container run by the launcher script. This enables pulling and running Docker images from
private Docker registries.

Login using:

[source,bash]
----
docker login ${REGISTRY_URL}
----

The credentials file path can be passed as an option via `--docker-credentials-file` or `-p` to
the `myapp` container.

==== View the installer script

[source,bash]
----
# sh
docker run --rm brightsparklabs/myapp:<version> install

# or if using a private registry for images
docker run --rm brightsparklabs/myapp:<version> \
  --docker-credentials-file ~/.docker/config.json \
  install
----

While it is not mandatory to view the script before running, it is highly recommended.

==== Run the installer script

[source,bash]
----
# sh
docker run --rm brightsparklabs/myapp:<version> install | sudo bash
----

The above will use the following defaults:

* `environment` => `production`.
* `install-dir` => `/opt/brightsparklabs/${APP_NAME}/production/`.
* `configuration-dir` => `/opt/brightsparklabs/${APP_NAME}/production/conf/`.
* `data-dir` => `/opt/brightsparklabs/${APP_NAME}/production/data/`.
* `backup-dir` => `/opt/brightsparklabs/${APP_NAME}/production/backup/`.

You can modify any of the above if desired. E.g.

[source,bash]
----
# sh
docker run --rm brightsparklabs/myapp:<version> \
    --environment "uat" \
    --configuration-dir /etc/myapp \
    --data-dir /mnt/data/myapp \
    install --install-dir ${HOME}/apps/myapp \
| sudo bash
----

Where::
--environment::: defines the environment name for the deployment. This allows multiple instances
of the application to be present on the same host. Defaults to `production`.
--install-dir::: defines the base path under which each environment is deployed. It will contain
a directory for each `environment` installed on the system (see above). Each environment directory
will contain the launcher, configuration directory and data directory (unless overridden, see
below). Defaults to `/opt/brightsparklabs/${APP_NAME}/`.
--configuration-dir::: defines the path to the configuration directory. Defaults to
`${INSTALL_DIR}/<environment>/conf/` (`${INSTALL_DIR}` is defined by `--install-dir` above).
--data-dir::: defines the path to the data directory. Defaults to
`${INSTALL_DIR}/<environment>/data/` (`${INSTALL_DIR}` is defined by `--install-dir` above).

The installation script will generate a launcher script for controlling the application. The script
location will be printed out when running the install script. This script should now be used as the
main entrypoint to all appcli functions for managing your application.

== Usage

This section details what commands and options are available.

=== Top-level Commands

To be used in conjunction with your application `./myapp <command>`

E.g. `./myapp configure init`

Commands::
--
[horizontal]
backup::: Create a backup of application data and configuration.
configure::: Configures the application.
encrypt::: Encrypts the specified string.
init::: Initialises the application.
launcher::: Outputs an appropriate launcher bash script.
migrate::: Migrates the configuration of the application to a newer version.
orchestrator::: Perform docker orchestration
restore::: Restore a backup of application data and configuration.
service::: Lifecycle management commands for application services.
task::: Commands for application tasks.
version::: Fetches the version of the app being managed with appcli.
view-backups::: View a list of locally-available backups.
--

Options::
--
-–debug::: Enables debug level logging.
-c, -–configuration-dir PATH::: Directory containing configuration files. [This is required unless
subcommand is one of: `install`.
-d, -–data-dir PATH::: Directory containing data produced/consumed by the system. This is required
unless subcommand is one of: `install`.
-t, -–environment TEXT::: Deployment environment the system is running in. Defaults to `production`.
-p, -–docker-credentials-file PATH::: Path to the Docker credentials file (config.json) on the host
for connecting to private Docker registries.
-a, -–additional-data-dir TEXT::: Additional data directory to expose to launcher container. Can be
specified multiple times.
-e, -–additional-env-var TEXT::: Additional environment variables to expose to launcher container.
Can be specified multiple times.
-–help::: Show the help message and exit.
--

==== Command: `backup`

Creates a backup `.tgz` file in the backup directory that contains files from the configuration
and data directory, as configured in `stack-settings.yml`. After the backup is taken, remote
backup strategies will be executed (if applicable).

Usage: `./myapp backup [OPTIONS] [ARGS]`

Options::
-–pre-stop-services/-–no-pre-stop-services::: Whether to stop services before performing backup.
-–post-start-services/-–no-post-start-services::: Whether to start services after performing backup.
-–help::: Show the help message and exit.

The `backup` command optionally takes an argument corresponding to the `name` of the backup to
run. If no `name` is provided, all backups will attempt to run.

==== Command Group: `configure`

Configures the application.

Usage: `./myapp configure [OPTIONS] COMMAND [ARGS]`

Commands::
apply::: Applies the settings from the configuration.
diff::: Get the differences between current and default configuration settings.
get::: Reads a setting from the configuration.
get-secure::: Reads a setting from the configuration, decrypting if it is encrypted. This will
prompt for the setting key.
init::: Initialises the configuration directory.
set::: Saves a setting to the configuration. Allows setting the type of value with option `--type`,
and defaults to string type. Use `-e` to encrypt the value when setting.
template::: Configures the baseline templates.
edit::: Open the settings file for editing with vim-tiny.

Options::
-–help::: Show the help message and exit.

==== Command: `encrypt`

Encrypts the specified string.

Usage: `./myapp encrypt [OPTIONS] TEXT`

Options::
-–help::: Show the help message and exit.

==== Command Group: `init`

Initialises the application.

Usage: `./myapp init [OPTIONS] COMMAND [ARGS]`

Commands::
keycloak::: Initialises a Keycloak instance with BSL-specific initial configuration.

Options::
-–help::: Show the help message and exit.

==== Command: `launcher`

Outputs an appropriate launcher bash script to stdout.

Usage: `./myapp launcher [OPTIONS]`

Options::
-–help::: Show the help message and exit.

==== Command: `migrate`

Migrates the application configuration to work with the current application version.

Usage: `./myapp migrate [OPTIONS]`

Options::
-–help::: Show the help message and exit.

==== Command Group: `orchestrator`

Perform tasks defined by the orchestrator.

Usage: `./myapp orchestrator [OPTIONS] COMMAND [ARGS]`

All commands are defined within the orchestrators themselves. Run `./myapp orchestrator` to list
available commands.

For example, the following commands are availabl