serverless-offline-edge-lambda
=================================
A plugin for the [Serverless Framework](https://serverless.com/framework/) that simulates
the behavior of AWS CloudFront Edge Lambdas while developing offline.

### Setup

```bash
npm install --save-dev serverless
npm install --save-dev serverless-offline-edge-lambda
```

_serverless.yml_
```yaml
service:
  name: edge-lambdas

plugins:
  - serverless-offline-edge-lambda

provider:
  name: aws
  runtime: nodejs12.x

functions:
  lambda:
    handler: src/handlers.onViewerRequest
    lambdaAtEdge:
      distribution: 'WebsiteDistribution'
      eventType: 'viewer-request'
      pathPattern: '/lambda'

resources:
  Resources:
    WebsiteDistribution:
      Type: 'AWS::CloudFront::Distribution'
      Properties:
        DistributionConfig:
          DefaultCacheBehavior:
```

```bash
npx serverless offline start --port=<port>
```

#### Use with `serverless-offline`
The plugin should not be used in conjunction with `serverless-offline` because both plugins define the `offline` command.

#### Use with `serverless-plugin-cloudfront-lambda-edge`
This plugin does not handle packaging and deploying edge lambdas to the cloud. Therefore
this plugin can be used with `serverless-plugin-cloudfront-lambda-edge`. Again, doing so
is optional. The schema in _serverless.yml_ derives from that used by `serverless-plugin-cloudfront-lambda-edge`.

#### Use with Transpilers
This plugin can also be used with transpilers such as `serverless-plugin-typescript`. In the
cases where the transpiler outputs built files to a path that differs from the path
specified for the handlers (e.g. _.build/src/handers.onViewerRequest_), this plugin accepts
a configuration option `path` that it uses to resolve function handlers.

```yaml
plugins:
  - serverless-plugin-typescript

custom:
  offlineEdgeLambda:
    path: '.build'
```

For usage with `serverless-webpack` and `serverless-bundle` the config is similar but the build path changes.
```yaml
plugins:
  - serverless-webpack # or serverless-bundle

custom:
  offlineEdgeLambda:
    path: './.webpack/service/'
```

### Hot Reload Support

Hot reload for serverless-esbuild and serverless-plugin-typescript are available with extra configuration.

The watch/reload mechanism is available form serverless-webpack, but is disabled by default for esbuild and typescript.

The flag "watchReload: true" will turn on the watcher so that typescript and esbuild solutions use the watcher to hot reload the handlers.
The path to the built handlers must be specified for the watcher to work correctly.

example:
```yaml
custom:
  offlineEdgeLambda:
    path: '.esbuild/service'
    watchReload: true
```

Additional options can be used to modify the behavior of the file watcher and debounce logic (ignoreInitial, awaitWriteFinish, interval, debounce, and any other chokidar option).

example:

```yaml
custom:
  offlineEdgeLambda:
    path: '.dist/service'
    watchReload: true
    ignoreInitial: true
    awaitWriteFinish: true
    interval: 500,
    debounce: 750
```

### Options

#### `--headersFile`

Default: _undefined_

CloudFront [injects some headers](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/using-cloudfront-headers.html) into the request. You can set these by creating a JSON file and passing its path as an option.

Example:

```json
// .cf-headers.json
{
    "CloudFront-Viewer-Country": "us",
    "CloudFront-Viewer-Country-Region": "tx"
}
```

```bash
npx serverless offline start --headersFile .cf-headers.json
```