# Retrieving Static Content from the Boost Amazon S3 Bucket 

The `StaticContentTemplateView` class (in the `core/` app) is a Django view that handles requests for static content. 

Its URL path is the very last path in our list of URL patterns (see `config/urls.py`) because it functions as the fallback URL pattern. If a user enters a URL that doesn't match anything else defined in our URL patterns, this view will attempt to retrieve the request as static content from S3 using the URL path.

The `StaticContentTemplateView` calls S3 using the URL pattern and generates a list of potential keys to check. It then checks the specified S3 bucket for each of those keys and returns the first match it finds, along with the file content type. Passing the content type with the bucket contents allows the content to be delivered appropriately to the user (so HTML files will be rendered as HTML, etc.)

Boost uses the AWS SDK for Python (boto3) to connect to an S3 bucket and retrieve the static content. If no bucket name is provided, pur process uses the `STATIC_CONTENT_BUCKET_NAME` setting from the Django project settings.

## How we decide which S3 keys to try 

The JSON config file `{env}_static_config.json` is used to map site paths to corresponding paths in the Amazon S3 bucket where static content is stored. This mapping is used to create shortcuts to static content files in the S3 bucket, which can be accessed using URLs that correspond to the site paths.

The `{env}_static_config.json` file is a list of objects, where each object represents a mapping between a site path and an S3 path. Each object has two properties: `site_path` and `s3_path`.

The `site_path` property is the path to the static content file as it appears in the web application. For example, if the static content file is located at `/static/js/main.js`, the site path would be `/static/js/`.

The `s3_path` property is the path to the static content file in the S3 bucket. For example, if the S3 bucket is named `my-bucket` and the static content file is located at `my-bucket/site/develop/js/main.js`, the S3 path would be `/site/develop/js/`.

When a request is made to a URL that corresponds to a site path, the get_content_from_s3() function looks up the site path in the `{env}_static_config.json` file to find the corresponding S3 path. It then uses the S3 path to retrieve the static content from the S3 bucket.

Take a look at this sample `{env}_static_config.json` file: 

```javascript
[
    {
        "site_path": "/develop/libs/",
        "s3_path": "/site/develop/libs/"
    },
    {
        "site_path": "/develop/doc/",
        "s3_path": "/site/develop/doc/html/"
    },
    {
        "site_path": "/",
        "s3_path": "/site/develop/"
    }
]
```

**Example 1**: If the URL request is for `/develop/libs/index.html`, the S3 keys that we would try are:

- `/site/develop/libs/index.html`
  
**Example 2**: If the URL request is for `/develop/doc/index.html`, the S3 keys that the function would try are:

- `/site/develop/doc/html/index.html`
- `/site/develop/doc/index.html`
  
**Example 3**: If the URL request is for `/index.html`, the S3 keys that the function would try are:

- `/site/develop/index.html`
- `/site/index.html`

We first try to retrieve the static content using the exact S3 key specified in the site-to-S3 mapping. If we can't find the content using that key, we will try alternative S3 keys based on the `site_path` and `s3_path` properties in the `{env}_static_config.json` file.