Add paginate to koalambda

lib/manipulation.d.ts

@@ -4,3 +4,13 @@ export declare const putEventToState: (variableName: string) => (ctx: any, next?
 export declare const filterProperty: (variableName: string, filterFunction: (record: any) => boolean) => (ctx: any, next?: any) => Promise<void>;
 export declare const putEnvVariableToState: (envVariableName: string, variableStatePath?: string) => (ctx: any, next?: any) => Promise<void>;
 export declare const executeInOrder: (stopCondition: (ctx: any) => boolean, ...functions: any[]) => (ctx: any, next?: any) => Promise<void>;
+/** This function requiers to have two properties specified in the state:
+ *  - 'offset' - number of skipped elemnets,
+ *  - 'count' - number of elements per page
+ *  - 'apiPaginationEndpoint' - the base url (ex. www.a.eu) for pages, result will look like http://www.a.eu/test?offest=1&count=2
+ *
+ * It also requires response to have properties:
+ *  - items - The acctual items to return
+ *  - totalCount - total amount of items available
+ */
+export declare const paginateResponse: (ctx: any, next: any) => Promise<void>;

package.json

@@ -55,6 +55,7 @@
   },
   "dependencies": {
     "@types/aws-lambda": "0.0.30",
+    "api-pagination": "^1.0.6",
     "chai-as-promised": "^7.1.1",
     "koa-compose": "^4.0.0",
     "lodash": "^4.17.4",

src/manipulation.ts

@@ -3,6 +3,10 @@ import get from 'lodash/get'
 import set from 'lodash/set'
 import isArray from 'lodash/isArray';
 import isFunction from 'lodash/isFunction';
+import * as apiPagination from 'api-pagination'
+import isNumber from 'lodash/isNumber';
+import * as isString from 'lodash/isString';
+
 
 export const mapPropertyDown = (source: string, target: string, defaultValue?: any) => async (ctx, next?) => {
     let value = get(ctx.state, source, defaultValue || null)
@@ -73,4 +77,54 @@ export const executeInOrder = (stopCondition: (ctx) => boolean, ...functions) =>
             }
         }
     }
+}
+
+/** This function requiers to have two properties specified in the state:
+ *  - 'offset' - number of skipped elemnets,
+ *  - 'count' - number of elements per page
+ *  - 'apiPaginationEndpoint' - the base url (ex. www.a.eu) for pages, result will look like http://www.a.eu/test?offest=1&count=2
+ * 
+ * It also requires response to have properties:
+ *  - items - The acctual items to return
+ *  - totalCount - total amount of items available
+ */
+export const paginateResponse = async (ctx, next) => {
+    let offset = ctx.state.offset
+    let count = ctx.state.count
+    let apiPaginationEndpoint = ctx.state.apiPaginationEndpoint
+    let response = ctx.state.response
+
+    // Checking input 
+
+    if(!isNumber(offset) || offset < 0)
+        throw Error('Missing property "offset" in state object or "offset" <= 0')
+
+    if(!isNumber(count) || count <= 0) 
+        throw Error('Missing property "count" in state object or "count" <= 0')
+
+    if(!isString(apiPaginationEndpoint))
+        throw Error('Missing property "apiPaginationEndpoint" in state object or proprty is not string')
+
+    if(!response)
+        throw Error('The response object is null or undefined')
+
+    if(!isArray(response.items) || response.items.length === 0)
+        throw Error('Items should be non empty array')
+
+    if(!isNumber(response.totalCount) || response.totalCount < 0)
+        throw Error('totalCount should be a number > 0')
+
+
+    //Paginate
+
+    let pagination: any = {
+        items: response.items,
+        requestOffset: offset,
+        requestCount: count,
+        totalCount: response.totalCount
+    }
+
+    ctx.state.response = apiPagination.toRest(pagination, apiPaginationEndpoint)
+
+    next && await next()
 }