From aa006086f69c827d780e6e0e69947ca7ee6e2c70 Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Sat, 8 Jan 2022 22:27:01 +0530
Subject: feat: adds exposed filter function

---
 TODO.md             |  2 +-
 src/eval/index.ts   |  4 ++--
 src/index.ts        | 17 ++++++++++++++++-
 tests/basic.spec.ts | 12 ++++++++++++
 4 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 tests/basic.spec.ts

diff --git a/TODO.md b/TODO.md
index b471dc5..e1523ba 100644
--- a/TODO.md
+++ b/TODO.md
@@ -6,7 +6,7 @@
   - [ ] Parse: `{2, 5}` quantifiers
   - [ ] Eval: `^$` start-end
   - [ ] Parse, Eval: Not/Inverse
-  - [ ] Func: filter
+  - [X] Func: filter
   - [ ] Func: match
   - [ ] Func: replace
 
diff --git a/src/eval/index.ts b/src/eval/index.ts
index d5c56c2..6656743 100644
--- a/src/eval/index.ts
+++ b/src/eval/index.ts
@@ -1,5 +1,5 @@
 import { pipe } from 'fp-ts/function'
-import {takeLeftWhile} from 'fp-ts/lib/Array'
+import { takeLeftWhile } from 'fp-ts/lib/Array'
 import { Expr, ListExpr } from '../types'
 import { match } from '../utils'
 
@@ -26,7 +26,7 @@ export const find = <T>([startO, exprs, endO]: ListExpr, list: T[]): any => {
               takeLeftWhile(x => check(expr)(x, i, list)),
             )
             console.log(x)
-            
+
             return true
           },
           _: _ => false,
diff --git a/src/index.ts b/src/index.ts
index 82eefe8..691d676 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,2 +1,17 @@
+import { fold, map } from 'fp-ts/lib/Either'
+import { identity, pipe } from 'fp-ts/lib/function'
+import { find } from './eval'
+import { parser } from './parser'
 
-export * from './parser';
+const toSourceString = (r: string | RegExp): string => typeof r === 'string' ? r : r.source
+
+export const filter = <T>(listExp: string | RegExp, list: T[]): T[] =>
+  pipe(
+    listExp,
+    toSourceString,
+    parser,
+    map(([lxp, _]) => find(lxp, list)),
+    fold(([err, _]) => {
+      throw new Error(err)
+    }, identity),
+  )
diff --git a/tests/basic.spec.ts b/tests/basic.spec.ts
new file mode 100644
index 0000000..d964053
--- /dev/null
+++ b/tests/basic.spec.ts
@@ -0,0 +1,12 @@
+import { filter } from '../src'
+
+describe('Basic tests', () => {
+  it('should do it', () => {
+    expect(filter(/\s/, [1, '2', 3, '4'])).toEqual(['2', '4'])
+    expect(filter(/\n/, [1, '2', 3, '4'])).toEqual([1, 3])
+    expect(filter(/\T/, [1, 0, '4', ''])).toEqual([1, '4'])
+    expect(filter(/\F/, [1, 0, '4', ''])).toEqual([0, ''])
+    expect(filter(/\F\T/, [1, 0, '4', ''])).toEqual([])
+    expect(filter(/\s\T/, [1, 0, '4', ''])).toEqual(['4'])
+  })
+})
-- 
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