live-elements-web-server: Added ValueOrError class.

Author: dinusv

packages/live-elements-web-server/shared/core/value-or-error.mjs

@@ -0,0 +1,67 @@
+import StandardError from "../errors/standard-error.mjs";
+
+export default class ValueOrError{
+    constructor(value, error){
+        this._value = value
+        this._error = error
+    }
+
+    get value(){ return this._value }
+    get error(){ return this._error }
+
+    get hasValue(){ return this._value !== undefined }
+    get hasError(){ return this._error !== undefined }
+
+    unwrapOrThrow(){
+        if ( this._error ){
+            throw this._error
+        }
+        return this._value
+    }
+
+    unwrapAnd(cb){
+        if ( this._error ){
+            cb(this._error)
+        }
+        return this._value
+    }
+
+    toJSON(valueCb, errorCb){
+        if ( this._value ){
+            return valueCb 
+                ? { value: valueCb(this._value ) }
+                : { value: this._value }
+        } else {
+            return errorCb
+                ? { error: errorCb(this._error) }
+                : { error: this._error instanceof StandardError ? this._error.toJSON() : this._error.message }
+        }
+    }
+
+    static errorObject(error){
+        return { error: error instanceof StandardError ? error.toJSON() : error.message }
+    }
+    static valueObject(value){
+        return { value: value }
+    }
+
+    static fromError(error){
+        return new ValueOrError(undefined, error)
+    }
+    static fromValue(value){
+        return new ValueOrError(value, undefined)
+    }
+
+    static fromJSON(ob, valueCb, errorCb){
+        if ( ob.hasOwnProperty('value') ){
+            return valueCb
+                ? new ValueOrError(valueCb(ob.value))
+                : new ValueOrError(ob.value)
+        } else if ( ob.hasOwnProperty('error') ){
+            return errorCb
+                ? new ValueOrError(undefined, errorCb(ob.error))
+                : new ValueOrError(undefined, ob.error)
+        }
+        return new ValueOrError(undefined, new Error('ValueOrError: Object missing value or error key.'))
+    }
+}