From 6b732e2aaa08d14eea408bfc5bbfc1d740597c1e Mon Sep 17 00:00:00 2001
From: Anand Chowdhary <mail@anandchowdhary.com>
Date: Thu, 22 Oct 2020 19:05:18 +0530
Subject: [PATCH] :sparkles: Add support for cursor

---
 src/helpers/parse-object-literal.ts | 76 +++++++++++++++++++++++++++++
 src/modules/user/user.controller.ts |  2 +
 src/pipes/cursor.pipe.ts            | 14 +++---
 3 files changed, 86 insertions(+), 6 deletions(-)
 create mode 100644 src/helpers/parse-object-literal.ts

diff --git a/src/helpers/parse-object-literal.ts b/src/helpers/parse-object-literal.ts
new file mode 100644
index 000000000..687b8f46c
--- /dev/null
+++ b/src/helpers/parse-object-literal.ts
@@ -0,0 +1,76 @@
+/**
+ * Parse a string like "a: 1, b: 2" to { a: 1, b: 2 }
+ * @param objectLiteralString - String to parse
+ * @source https://github.com/mbest/js-object-literal-parse
+ */
+export const parseObjectLiteral = (
+  objectLiteralString: string,
+): [string, string | undefined][] => {
+  const stringDouble = '"(?:[^"\\\\]|\\\\.)*"';
+  const stringSingle = "'(?:[^'\\\\]|\\\\.)*'";
+  const stringRegexp = '/(?:[^/\\\\]|\\\\.)*/w*';
+  const specials = ',"\'{}()/:[\\]';
+  const everyThingElse = '[^\\s:,/][^' + specials + ']*[^\\s' + specials + ']';
+  const oneNotSpace = '[^\\s]';
+  const token = RegExp(
+    stringDouble +
+      '|' +
+      stringSingle +
+      '|' +
+      stringRegexp +
+      '|' +
+      everyThingElse +
+      '|' +
+      oneNotSpace,
+    'g',
+  );
+  const divisionLookBehind = /[\])"'A-Za-z0-9_$]+$/;
+  const keywordRegexLookBehind = { in: 1, return: 1, typeof: 1 };
+  let str = objectLiteralString.trim();
+  if (str.charCodeAt(0) === 123) str = str.slice(1, -1);
+  const result: [string, string | undefined][] = [];
+  let toks = str.match(token);
+  let key: string | undefined = undefined;
+  let values = [];
+  let depth = 0;
+  if (toks) {
+    toks.push(',');
+    for (let i = 0, tok: string; (tok = toks[i]); ++i) {
+      const c = tok.charCodeAt(0);
+      if (c === 44) {
+        if (depth <= 0) {
+          if (!key && values.length === 1) {
+            key = values.pop();
+          }
+          result.push([key, values.length ? values.join('') : undefined]);
+          key = undefined;
+          values = [];
+          depth = 0;
+          continue;
+        }
+      } else if (c === 58) {
+        if (!depth && !key && values.length === 1) {
+          key = values.pop();
+          continue;
+        }
+      } else if (c === 47 && i && tok.length > 1) {
+        const match = toks[i - 1].match(divisionLookBehind);
+        if (match && !keywordRegexLookBehind[match[0]]) {
+          str = str.substr(str.indexOf(tok) + 1);
+          toks = str.match(token);
+          toks.push(',');
+          i = -1;
+          tok = '/';
+        }
+      } else if (c === 40 || c === 123 || c === 91) {
+        ++depth;
+      } else if (c === 41 || c === 125 || c === 93) {
+        --depth;
+      } else if (!key && !values.length && (c === 34 || c === 39)) {
+        tok = tok.slice(1, -1);
+      }
+      values.push(tok);
+    }
+  }
+  return result;
+};
diff --git a/src/modules/user/user.controller.ts b/src/modules/user/user.controller.ts
index 40ddf4016..f9fab78a9 100644
--- a/src/modules/user/user.controller.ts
+++ b/src/modules/user/user.controller.ts
@@ -1,6 +1,7 @@
 import { Controller, Get, Param, ParseIntPipe, Query } from '@nestjs/common';
 import { users } from '@prisma/client';
 import { OmitSecrets } from 'src/modules/prisma/prisma.interface';
+import { CursorPipe } from 'src/pipes/cursor.pipe';
 import { OptionalIntPipe } from 'src/pipes/optional-int.pipe';
 import { OrderByPipe } from 'src/pipes/order-by.pipe';
 import { UsersService } from './user.service';
@@ -13,6 +14,7 @@ export class UserController {
   async getAll(
     @Query('skip', OptionalIntPipe) skip?: number,
     @Query('take', OptionalIntPipe) take?: number,
+    @Query('cursor', CursorPipe) cursor?: Record<string, number | string>,
     @Query('orderBy', OrderByPipe) orderBy?: Record<string, 'asc' | 'desc'>,
   ): Promise<OmitSecrets<users>[]> {
     return this.usersService.users({ skip, take, orderBy });
diff --git a/src/pipes/cursor.pipe.ts b/src/pipes/cursor.pipe.ts
index 75414b93b..b6264e5d7 100644
--- a/src/pipes/cursor.pipe.ts
+++ b/src/pipes/cursor.pipe.ts
@@ -5,8 +5,9 @@ import {
   HttpStatus,
   ArgumentMetadata,
 } from '@nestjs/common';
+import { parseObjectLiteral } from 'src/helpers/parse-object-literal';
 
-/** Convert a string like "id 12, name Anand" to { id: 12, name: "Anand" } */
+/** Convert a string like "id: 12, b: 'Anand'" to { id: 12, name: "Anand" } */
 @Injectable()
 export class CursorPipe implements PipeTransform {
   transform(
@@ -15,13 +16,14 @@ export class CursorPipe implements PipeTransform {
   ): Record<string, number | string> | undefined {
     if (value == null) return undefined;
     try {
-      const rules = value.split(' ').map(val => val.trim());
-      const cursor: Record<string, number | string> = {};
+      const rules = parseObjectLiteral(value);
+      const items: Record<string, number | string> = {};
       rules.forEach(rule => {
-        const [key, val] = rule.split(' ', 1);
-        rules[key] = val;
+        const num = Number(rule[1]);
+        if (!isNaN(num)) items[rule[0]] = num;
+        else items[rule[0]] = rule[1];
       });
-      return cursor;
+      return items;
     } catch (_) {
       throw new HttpException(
         `"${metadata.data}" should be like "id 12, name Anand", provided "${value}"`,