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https://github.com/amancevice/terraform-aws-slackbot

Serverless Extensible Slackbot
https://github.com/amancevice/terraform-aws-slackbot

aws nodejs serverless slack terraform

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Serverless Extensible Slackbot

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# Serverless Slackbot

![arch](./docs/arch.png)

[![terraform](https://img.shields.io/github/v/tag/amancevice/terraform-aws-slackbot?color=62f&label=version&logo=terraform&style=flat-square)](https://registry.terraform.io/modules/amancevice/slackbot/aws)
[![build](https://img.shields.io/github/actions/workflow/status/amancevice/terraform-aws-slackbot/test-validate.yml?logo=github&style=flat-square)](https://github.com/amancevice/terraform-aws-slackbot/actions/workflows/test-validate.yml)

[![ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/smallweirdnumber)

A simple, serverless back end for your Slack app.

> ⚠️ NOTE — `v25` of this module is a complete architectural redesign and is not compatible with previous versions.

## Use Case

The application intentionally does very little, leaving room for you to customize your app.

Out of the box, it will:

- Receive an event from Slack in the form of an HTTP request
- Verify the request's signature headers
- Publish the JSON-ified payload to EventBridge where it can be processed asynchronously
- And, finally, send a response back to Slack (usually an empty 200)

Adding asynchronous features to your slackbot is as simple as adding the appropriate EventBridge rule/target, and some kind of handler function. See the section on [responding to events asynchronously](#responding-to-events-asynchronously) for details. See the [EventBridge documentation](https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-event-patterns.html) for more info on event pattern matching.

In some cases, you may want your Slack app to send a custom, synchronous, response to Slack instead of an empty `200` OK. External select menus and some callbacks, for example, need to respond to Slack with custom data and cannot be processed asyncronously. See the section on [responding to events synchronously](#responding-to-events-synchronously) for details.

## Prerequisites

Before applying this module you should have created the following resources:

- Route53 Hosted Zone (eg, `example.com`)
- An available subdomain for your app's REST API (eg, `slack.example.com`)
- ACM Certificate covering your app's subdomain (eg, `*.example.com`, `slack.example.com`)
- A [Slack App](https://api.slack.com/apps) with a signing secret, OAuth client keys, and a default web API token

## SnapStart

AWS Lambda supports [SnapStart](https://docs.aws.amazon.com/lambda/latest/dg/snapstart.html) for functions using Python v3.12+ or greater.

Enabling SnapStart will improve (decrease) the latency for your app's HTTP responses but it is not free, so it is disabled by default.

## Example Usage

See the [example](./example) project for detailed usage.

```terraform
data "aws_acm_certificate" "cert" {
domain = "example.com"
types = ["AMAZON_ISSUED"]
}

data "aws_route53_zone" "zone" {
name = "example.com."
}

module "slackbot" {
source = "amancevice/slackbot/aws"
version = "~> 25.0"

# App Name
name = "slackbot"

# DNS
domain_name = "slack.example.com"
domain_certificate_arn = data.aws_acm_certificate.cert.arn
domain_zone_id = data.aws_route53_zone.zone.id

# LAMBDA CONFIG
lambda_snap_start_enabled = true

# SLACK
slack_client_id = var.slack_client_id
slack_client_secret = var.slack_client_secret
slack_error_uri = "https://example.com/slack/error.html"
slack_scope = "app_mentions:read,chat:write"
slack_signing_secret = var.slack_signing_secret
slack_success_uri = "slack://app?team={TEAM_ID}&id={APP_ID}"
slack_user_scope = ""
slack_token = var.slack_token

# TAGS
tags = {
# ...
}
}
```

## HTTP Routes

Endpoints are provided for the following routes:

| Route | Event Published? | Custom Response? | Purpose |
| :--------------- | ---------------: | ---------------: | :------------------------------------------------------------------------------------------------------- |
| `GET /install` | `No` | `No` | Helper to begin Slack's OAuth flow |
| `GET /oauth` | `Yes` | `No` | Complete Slack's [OAuth2](https://api.slack.com/docs/oauth) workflow (v2) |
| `POST /callback` | `Yes` | `Yes` | Handle Slack's [interactive messages](https://api.slack.com/messaging/interactivity) |
| `POST /event` | `Yes` | `No` | Handle events from Slack's [Events API](https://api.slack.com/events-api) |
| `POST /menu` | `Yes` | `Yes` | Handle [external select menus](https://api.slack.com/reference/block-kit/block-elements#external_select) |
| `POST /slash` | `Yes` | `Yes` | Handle Slack's [slash commands](https://api.slack.com/slash-commands) |

## Responding to Events Synchronously

For some events (external select menus, for example) you will need to respond to Slack with a JSON payload.
This can be accomplished by deploying a specially named Lambda function that returns a proxy-like response.

When your app receives an event that supports a synchronous response it will attempt to call a Lambda function with the naming convention:

```plaintext
-
```

This function should return a JSON object with `statusCode` and `body` fields.
The `statusCode` field should be `200` and the `body` field should be the response payload encoded as a JSON string.

### Example Synchronous Function

The following Python block is a crude example of a Lambda function that provides options for an external menu:

```python
import json

def handler(event, _):
return {
"statusCode": 200,
"body": json.dumps({
"options": [
{"value": "option1", "text": {"type": "plain_text", "text": "Option 1"}},
{"value": "option2", "text": {"type": "plain_text", "text": "Option 2"}},
{"value": "option3", "text": {"type": "plain_text", "text": "Option 2"}},
]
}),
}
```

Assuming our app is named `slackbot` we would then deploy this function with the name `slackbot-block_suggestion` since it is intended to be invoked for Slack events with the type of `block_suggestion`.

See the [example](./example) project for more advanced usage.

## Responding to Events Asynchronously

EventBridge events are actionable through [event patterns](https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-event-patterns.html).
You can filter events using a bus name, source value, detail-type, and even parts of the event payload.

The following table shows the mapping of route-key : event

| Route Key | Event Bus | Source | Detail Type |
| :--------------- | :----------- | :-------------- | :--------------- |
| `GET /oauth` | `` | `` | `GET /oauth` |
| `POST /callback` | `` | `` | `POST /callback` |
| `POST /event` | `` | `` | `POST /event` |
| `POST /menu` | `` | `` | `POST /menu` |
| `POST /slash` | `` | `` | `POST /slash` |

### Example Event Patterns

In order to process a given event you will need to create an EventBridge rule with a pattern that targets a specific event.

The following examples show how a subscription might me made in Terraform:

#### Callbacks

```terraform
resource "aws_cloudwatch_event_rule" "block_actions" {
event_bus_name = ""
# …

event_pattern = jsonencode({
source = [""]
detail-type = ["POST /callback"]
detail = {
type = ["block_actions"]
actions = {
action_id = ["your_action_id"]
}
}
})
}
```

```terraform
resource "aws_cloudwatch_event_rule" "view_submission" {
event_bus_name = ""
# …

event_pattern = jsonencode({
source = [""]
detail-type = ["POST /callback"]
detail = {
type = ["view_submission"]
view = {
callback_id = ["your_view_callback_id"]
}
}
})
}
```

#### Event

```terraform
resource "aws_cloudwatch_event_rule" "app_home_opened" {
event_bus_name = ""
# …

event_pattern = jsonencode({
source = [""]
detail-type = ["POST /callback"]
detail = {
type = ["event_callback"]
event = {
type = ["app_home_opened"]
}
}
})
}
```

#### OAuth

```terraform
resource "aws_cloudwatch_event_rule" "oauth" {
event_bus_name = ""
# …

event_pattern = jsonencode({
source = [""]
detail-type = ["GET /oauth"]
})
}
```

#### Slash Command

```terraform
resource "aws_cloudwatch_event_rule" "slash" {
event_bus_name = ""
# …

event_pattern = jsonencode({
source = [""]
detail-type = ["POST /slash"]
detail = {
type = ["slash_command"]
command = ["/your-command"]
}
})
}
```