From c1342bdac6d7c2f603bb69f1c9012833e88e32d6 Mon Sep 17 00:00:00 2001
From: ivaosthu <ivar.conradi.osthus@finn.no>
Date: Wed, 11 Jan 2017 15:51:24 +0100
Subject: [PATCH] WIP client specification #201

---
 docs/client-spec.md          |  11 ----
 docs/client-specification.md | 106 +++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+), 11 deletions(-)
 delete mode 100644 docs/client-spec.md
 create mode 100644 docs/client-specification.md

diff --git a/docs/client-spec.md b/docs/client-spec.md
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--- a/docs/client-spec.md
+++ /dev/null
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-# Client Specification 1.0
-
-This document describes the client contract. 
-
-**TODO:**
-- fetch and cache toggles (etag headers etc)
-- provide strategies implementations
-- evaluate if a feature toggle is enabled or not with the given activation strategies and configurations.
-- backup features
-- registration
-- send metrics
\ No newline at end of file
diff --git a/docs/client-specification.md b/docs/client-specification.md
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+# Client Specification 1.0
+
+This document describes the client contract. 
+
+## The basics
+All client implementations should strive to have a simple and consistent user API. 
+It should be a simple method, called isEnabled, to check if a feature toggle is enabled 
+or not. The method should return a `boolean` value, true or false. 
+
+```
+unleash.isEnabled("myAwesomeToggle")
+```
+
+The basic `isEnabled` method should also accept a default value. This should be used if 
+the client does not know anything about that that toggle name. If the user does not specify
+a default value, false should be returned for unknown feature toggles. 
+
+Example:
+
+``` 
+boolean value = unleash.isEnabled("unknownFeatureToggle", false);
+//value==false because default value was used. 
+```
+
+### Implementation of isEnabled
+A feature toggle is defined as: 
+
+```json
+{
+      "name": "Feature.B",
+      "description": "lorem ipsum",
+      "enabled": true,
+      "strategies": [
+        {
+          "name": "ActiveForUserWithId",
+          "parameters": {
+            "userIdList": "123,221,998"
+          }
+        },
+        {
+          "name": "GradualRolloutRandom",
+          "parameters": {
+            "percentage": "10"
+          }
+        }
+      ],
+      "strategy": "ActiveForUserWithId",
+      "parameters": {
+        "userIdList": "123,221,998"
+      }
+    }
+```
+
+A simple demo of the isEnable function in JavaScript-style (most implementation will probalby be more functional):
+
+```javascript
+function isEnabled(name, defaultValue) {
+    const toggle = toggleRepository.get(name);
+    let enabled = false;
+    
+    if ( !toggle ) {
+        return defaultValue;
+    } else if ( ! toggle.isEnabled) {
+        return false;
+    } else {
+        for(let i=0;i<toggle.strategies.length;i++) {
+            let strategyDef = toggle.strategies[i];
+            let strategyImpl = strategyImplRepository.get(strategyDef.name);
+            if(strategyImpl.isEnabled) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+}
+
+```
+
+
+## Actication Strategies
+Activation strategies are defined and confured in the unleash-service. It is up to the client
+to provide the actual implementation of each actication strategy. Client implementation should 
+also provide a defined interface to make it easier for the user to implement their own 
+activation strategies, and register those in the unleash client. 
+
+
+## Fetching feature toggles (polling)
+The client implementation should fetch toggles in the background, as regular polling. 
+In thread based environment (e.g. Java) this needs to be done on a sparate thread. 
+The default poll interval should be **15 seconds**, and it should be configurable. 
+
+
+## Client registration
+Client implementation should at initialization register with the unleash-server. 
+The should send a registration as specified in the [api documentation](https://github.com/Unleash/unleash/blob/master/docs/api/metrics-api.md#client-registration).
+The registration must include all fields specified.
+
+
+
+
+## Metrics
+
+## Backup feature toggles
+
+