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# PhoenixKit.Modules.Storage.FileServer (phoenix_kit v1.7.87)

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File serving logic with multi-location failover support.

Handles retrieving files from storage locations with automatic failover, CDN integration, and proper HTTP header management.

## Features

- Query file locations from database
- Priority-based location ordering
- Automatic failover to next location on failure
- CDN redirect support
- HTTP header generation for streaming
- Range request support (HTTP 206) for video streaming

## Examples

    iex> {:ok, file_info} = PhoenixKit.Modules.Storage.FileServer.get_file_location(
    ...>   "018e3c4a-9f6b-7890",
    ...>   "thumbnail"
    ...> )
    iex> file_info.path
    "/path/018e3c4a-9f6b-7890-thumbnail.jpg"
    iex> file_info.bucket.cdn_url
    "https://cdn.example.com"

## Summary

### Functions

get_file_location(file_uuid, instance_name)

Get file location with priority-ordered failover list.

http_headers(file_instance, options \\ [])

Generate HTTP headers for file serving.

location_accessible?(arg1)

Check if a file location is accessible (has a path).

parse_range_header(range_header, file_size)

Handle range request for partial file serving (video streaming).

## Functions

# get_file_location(file_uuid, instance_name)

Get file location with priority-ordered failover list.

Queries the database for all active locations of a file instance, ordered by bucket priority and location priority for automatic failover.

## Arguments

- `file_uuid` (binary) - File UUID v7
- `instance_name` (binary) - Variant name (e.g., "thumbnail", "medium")

## Returns

- `{:ok, file_info}` - Contains file metadata and location options
- `{:error, :not_found}` - File instance or locations not found
- `{:error, :no_active_locations}` - No active storage locations available

## Example Response

    {:ok, %{
      instance: %FileInstance{...},
      locations: [
        %FileLocation{
          path: "/path/018e3c4a-thumbnail.jpg",
          bucket: %Bucket{
            name: "Local SSD",
            provider: "local",
            cdn_url: nil,
            priority: 1
          },
          priority: 0,
          status: "active"
        },
        %FileLocation{
          path: "/path/018e3c4a-thumbnail.jpg",
          bucket: %Bucket{
            name: "Backblaze B2",
            provider: "b2",
            cdn_url: "https://cdn.example.com",
            priority: 2
          },
          priority: 0,
          status: "active"
        }
      ]
    }}

# http_headers(file_instance, options \\ [])

Generate HTTP headers for file serving.

Creates proper response headers including Content-Type, Content-Length, Cache-Control, and ETag for file streaming.

## Arguments

- `file_instance` (FileInstance) - File instance record with mime_type and size
- `options` (keyword) - Options for header generation
  - `:cache_control` - Cache-Control header (default: "max-age=31536000, public, immutable")
  - `:etag` - Include ETag header (default: true)

## Returns

Keyword list of HTTP headers.

## Example

    iex> headers = PhoenixKit.Modules.Storage.FileServer.http_headers(file_instance)
    iex> headers[:content_type]
    "image/jpeg"
    iex> headers[:cache_control]
    "max-age=31536000, public, immutable"

# location_accessible?(arg1)

Check if a file location is accessible (has a path).

Verifies that a file location record contains a valid storage path.

## Arguments

- `location` (FileLocation) - File location record with preloaded bucket

## Returns

Boolean indicating if location has a path.

# parse_range_header(range_header, file_size)

Handle range request for partial file serving (video streaming).

Parses Range header and returns start/end positions for 206 Partial Content response.

## Arguments

- `range_header` (binary) - Range header value (e.g., "bytes=0-1023")
- `file_size` (integer) - Total file size in bytes

## Returns

- `{:ok, start, end, headers}` - Valid range with response headers
- `{:error, :invalid_range}` - Malformed range header
- `{:error, :range_out_of_bounds}` - Range exceeds file size

## Example

    iex> PhoenixKit.Modules.Storage.FileServer.parse_range_header(
    ...>   "bytes=0-1023",
    ...>   5000
    ...> )
    {:ok, 0, 1023, [content_range: "bytes 0-1023/5000"]}

    iex> PhoenixKit.Modules.Storage.FileServer.parse_range_header(
    ...>   "bytes=1000-",
    ...>   5000
    ...> )
    {:ok, 1000, 4999, [content_range: "bytes 1000-4999/5000"]}