ufc readme update

README.md

@@ -1,12 +1,105 @@
-# Eppo SDK for Ruby
+# Eppo Ruby SDK
 
-## Getting Started
+[![Test and lint SDK](https://github.com/Eppo-exp/node-server-sdk/actions/workflows/lint-test-sdk.yml/badge.svg)](https://github.com/Eppo-exp/node-server-sdk/actions/workflows/lint-test-sdk.yml)
 
-Refer to our [SDK documentation](https://docs.geteppo.com/feature-flags/sdks/ruby) for how to install and use the SDK.
+[Eppo](https://www.geteppo.com/) is a modular flagging and experimentation analysis tool. Eppo's Node SDK is built to make assignments in multi-user server side contexts, compatible with Ruby 3.0.6 and above. Before proceeding you'll need an Eppo account.
 
-## Supported Ruby Versions
-This version of the SDK is compatible with Ruby 3.0.6 and above.
+## Features
 
-## Note for installation for SDK development
+- Feature gates
+- Kill switches
+- Progressive rollouts
+- A/B/n experiments
+- Mutually exclusive experiments (Layers)
+- Dynamic configuration
 
-We recommend developing in Docker: run `docker run --rm -v "$PWD":/usr/src/app -it $(docker build -q .) sh` from the root directory of this project and then the Rakefile commands can be run from the shell, e.g. `rake install` or `rake test`.
+## Installation
+
+```shell
+gem install eppo-server-sdk
+```
+
+## Quick start
+
+Begin by initializing a singleton instance of Eppo's client. Once initialized, the client can be used to make assignments anywhere in your app.
+
+#### Initialize once
+
+```ruby
+require 'eppo_client'
+
+config = EppoClient::Config.new('SDK-KEY-FROM-DASHBOARD')
+client = EppoClient::init(config)
+```
+
+
+#### Assign anywhere
+
+```ruby
+require 'eppo_client'
+
+client = EppoClient::Client.instance
+
+variation = client.get_string_assignment(
+  'new-user-onboarding', 
+  user.id, 
+  { country => user.country }, 
+  'control'
+)
+```
+
+## Assignment functions
+
+Every Eppo flag has a return type that is set once on creation in the dashboard. Once a flag is created, assignments in code should be made using the corresponding typed function: 
+
+```ruby
+get_boolean_assignment(...)
+get_numeric_assignment(...)
+get_integer_assignment(...)
+get_string_assignment(...)
+get_json_assignment(...)
+```
+
+Each function has the same signature, but returns the type in the function name. For booleans use `getBooleanAssignment`, which has the following signature:
+
+```ruby
+getBoolAssignment: (
+  flagKey: string,
+  subjectKey: string,
+  subjectAttributes: Record<string, any>,
+  defaultValue: boolean,
+) => boolean
+  ```
+
+## Assignment logger 
+
+To use the Eppo SDK for experiments that require analysis, pass in a callback logging function to the `init` function on SDK initialization. The SDK invokes the callback to capture assignment data whenever a variation is assigned. The assignment data is needed in the warehouse to perform analysis.
+
+The code below illustrates an example implementation of a logging callback using [Segment](https://segment.com/), but you can use any system you'd like. The only requirement is that the SDK receives a `logAssignment` callback function. Here we define an implementation of the Eppo `IAssignmentLogger` interface containing a single function named `logAssignment`:
+
+```ruby
+require 'segment/analytics'
+
+# Connect to Segment (or your own event-tracking system)
+Analytics = Segment::Analytics.new({ write_key: 'SEGMENT_WRITE_KEY' })
+
+class CustomAssignmentLogger < EppoClient::AssignmentLogger
+  def log_assignment(assignment)
+    Analytics.track(assignment["subject"], "Eppo Assignment", assignment)
+  end
+end
+
+config = EppoClient::Config.new(
+  'SDK-KEY-FROM-DASHBOARD',
+  assignment_logger: CustomAssignmentLogger.new
+)
+cli
+```
+
+## Philosophy
+
+Eppo's SDKs are built for simplicity, speed and reliability. Flag configurations are compressed and distributed over a global CDN (Fastly), typically reaching your servers in under 15ms. Server SDKs continue polling Eppo’s API at 30-second intervals. Configurations are then cached locally, ensuring that each assignment is made instantly. Evaluation logic within each SDK consists of a few lines of simple numeric and string comparisons. The typed functions listed above are all developers need to understand, abstracting away the complexity of the Eppo's underlying (and expanding) feature set.
+
+## SDK Development
+
+In development, we recommend Docker: run `docker run --rm -v "$PWD":/usr/src/app -it $(docker build -q .) sh` from the root directory of this project and then the Rakefile commands can be run from the shell, e.g. `rake install` or `rake test`.