Add ability to expose derived state apis (#39)

* Add ability to expose derived state apis

* rename API and arguments based on code review suggestions

Co-authored-by: Eric Alas <alas.eric@gmail.com>

src/common/interfaces/global.store.interface.ts

@@ -21,5 +21,8 @@ export interface IGlobalStore {
     SubscribeToPartnerState(source: string, partner: string, callback: (state: any) => void, eager: boolean): () => void;
     SubscribeToGlobalState(source: string, callback: (state: any) => void): () => void;
 
+    AddSelectors(source: string, selectors: Record<string, any>, mergeSelectors?: boolean): void;
+    SelectPartnerState(partner: string, selector: string, defaultReturn?: any): any;
+
     SetLogger(logger: ILogger): void;
 };

src/global.store.ts

@@ -22,6 +22,7 @@ export class GlobalStore implements IGlobalStore {
     private _eagerPartnerStoreSubscribers: { [key: string]: { [key: string]: (state) => void } }
     private _eagerUnsubscribers: { [key: string]: { [key: string]: () => void } }
     private _actionLogger: ActionLogger = null;
+    private _selectors: { [key: string]: any };
 
     private constructor(private _logger: ILogger = null) {
         this._stores = {};
@@ -30,6 +31,7 @@ export class GlobalStore implements IGlobalStore {
         this._eagerPartnerStoreSubscribers = {};
         this._eagerUnsubscribers = {};
         this._actionLogger = new ActionLogger(_logger);
+        this._selectors = {};
     }
 
     /**
@@ -334,6 +336,48 @@ export class GlobalStore implements IGlobalStore {
         this._actionLogger.SetLogger(logger);
     }
 
+    /**
+     * Summary: Expose a collection of Selecotrs from a Partner-level that other partners can later consume. This allows partners to derive data without forcing partners to know the state structure.
+     * 
+     * @access public
+     * 
+     * @param {string} source Name of the application exposing an derived state API
+     * @param {Record<string, any>} selectors The collection of APIs of derived state selectors.
+     * @param {boolean} mergeSelectors If the source application already exposed an API set, merge the new API being passed in.
+     * 
+     */
+     AddSelectors(source: string, selectors: Record<string, any>, mergeSelectors = false) {
+        if (this._selectors[source] == undefined) {
+            this._selectors[source] = selectors;
+        }
+
+        if (this._selectors[source] != undefined && mergeSelectors) {
+            this._selectors[source] = Object.assign({}, this._selectors[source], selectors);
+        }
+    }
+
+    /**
+     * Summary: Select derived state from a partner app using the selector name
+     * 
+     * @access public
+     * 
+     * @param {string} partner Name of the partner application to select derived data from
+     * @param {string} selector The name of the API to select
+     * @param {any} defaultReturn If the partner app does not have that API exposed, return this default value instead of undefined.
+     * 
+     */
+     SelectPartnerState(partner: string, selector: string, defaultReturn?: any) {
+        if (this._selectors[partner] == undefined) {
+            throw new Error(`ERROR: ${partner} not exposed any selectors.`);
+        }
+        if (this._selectors[partner][selector] == undefined) {
+            console.warn(`${partner} has not exposed a selector with the name: ${selector}`);
+            return defaultReturn;
+        }
+
+        return this._selectors[partner][selector]();
+    }
+
     private RegisterEagerSubscriptions(appName: string) {
         let eagerCallbacksRegistrations = this._eagerPartnerStoreSubscribers[appName];
         if (eagerCallbacksRegistrations === undefined || eagerCallbacksRegistrations === undefined)

test/global.store.tests.ts

@@ -480,4 +480,169 @@ describe("Global Store", () => {
             expect(isGlobalStateChanged).toBe(true);
         });
     });
+
+    describe("AddSelectors", () => {
+        let dummyPartnerReducer: Reducer<any, any> = (state: string = "Default", action: IAction<any>) => {
+            switch (action.type) {
+                case "Local": return "Local";
+                case "Global": return "Global";
+            }
+        };
+
+        it("Should successfully expose derived state API", () => {
+            let partnerAppName = "SamplePartner-2022";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            // Arrange
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+                selectStateLowerCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toLowerCase()
+                }
+            });
+
+            // Assert
+            const api = (<any>globalStore)._selectors[partnerAppName];
+            expect(api.selectStateUpperCased).toBeDefined();
+            expect(api.selectStateLowerCased).toBeDefined();
+        });
+
+        it("Should successfully merge derived state API", () => {
+            let partnerAppName = "SamplePartner-2023";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            // Arrange
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+            });
+
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateLowerCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toLowerCase()
+                }
+            }, true);
+
+            // Assert
+            const api = (<any>globalStore)._selectors[partnerAppName];
+            expect(api.selectStateUpperCased).toBeDefined();
+            expect(api.selectStateLowerCased).toBeDefined();
+        });
+
+        it("Should not merge derived state API", () => {
+            let partnerAppName = "SamplePartner-2024";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            // Arrange
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+            });
+
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateLowerCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toLowerCase()
+                }
+            });
+
+            // Assert
+            const api = (<any>globalStore)._selectors[partnerAppName];
+            expect(api.selectStateUpperCased).toBeDefined();
+            expect(api.selectStateLowerCased).toBeUndefined();
+        })
+    })
+
+    describe("SelectPartnerState", () => {
+        let dummyPartnerReducer: Reducer<any, any> = (state: string = "Default", action: IAction<any>) => {
+            switch (action.type) {
+                case "Local": return "Local";
+                case "Global": return "Global";
+                default:
+                    return state;
+            }
+        };
+
+        it("Should be able to request a piece of derived state with valid key", () => {
+            // Arrange
+            let partnerAppName = "SamplePartner-2012";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+                selectStateLowerCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toLowerCase()
+                }
+            });
+
+            // Act
+            const partnerStateComputedUpperCase = globalStore.SelectPartnerState(partnerAppName, "selectStateUpperCased");
+            expect(partnerStateComputedUpperCase).toEqual("DEFAULT");
+            const partnerStateComputedLowerCase = globalStore.SelectPartnerState(partnerAppName, "selectStateLowerCased");
+            expect(partnerStateComputedLowerCase).toEqual("default");
+        });
+
+        it("Should be return undefined if derived state key is not defined", () => {
+            // Arrange
+            let partnerAppName = "SamplePartner-2013";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+            });
+
+            // Act
+            const partnerStateComputedLowerCase = globalStore.SelectPartnerState(partnerAppName, "selectStateLowerCased");
+            expect(partnerStateComputedLowerCase).toEqual(undefined);
+        });
+
+        it("Should be return default value if derived state key is not defined", () => {
+            // Arrange
+            let partnerAppName = "SamplePartner-2013";
+            const partnerStore = globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            globalStore.AddSelectors(partnerAppName, {
+                selectStateUpperCased: () => {
+                    const state = partnerStore.getState();
+                    return state.toUpperCase()
+                },
+            });
+
+            // Act
+            const partnerStateComputedLowerCase = globalStore.SelectPartnerState(partnerAppName, "selectStateLowerCased", "I am a default value");
+            expect(partnerStateComputedLowerCase).toEqual("I am a default value");
+        });
+
+        it("Should throw error if partner has not exposed any derived", () => {
+            // Arrange
+            let partnerAppName = "SamplePartner-2014";
+            let exceptionThrown = false;
+            globalStore.CreateStore(partnerAppName, dummyPartnerReducer, [], ["Global"], false, false);
+
+            try {
+                globalStore.SelectPartnerState(partnerAppName, "selectStateLowerCased");
+            } catch {
+                exceptionThrown = true;
+            }
+
+            // Assert
+            expect(exceptionThrown).toBeTruthy();
+        });
+    });
 });