From e8322ca988fc20baf7892915e6ccb069b11c608e Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Sat, 8 Jan 2022 18:14:59 +0530
Subject: feat(parser): implements or syntax

---
 src/parser/index.ts | 14 +++++++++++++-
 src/parser/utils.ts | 13 ++++++++-----
 2 files changed, 21 insertions(+), 6 deletions(-)

(limited to 'src/parser')

diff --git a/src/parser/index.ts b/src/parser/index.ts
index ec29099..b8e6764 100644
--- a/src/parser/index.ts
+++ b/src/parser/index.ts
@@ -8,6 +8,7 @@ import {
   or,
   Parser,
   ParserResult,
+  prefixed,
   symbol,
   tuple3,
 } from './utils'
@@ -36,6 +37,17 @@ export const wrapQuantifiers: (e: ParserResult<Expr>) => ParserResult<Expr> =
     ),
   )
 
+export const wrapAlt: (e: ParserResult<Expr>) => ParserResult<Expr> = chain(
+  ([expr, input]) =>
+    pipe(
+      input,
+      mapTo(prefixed(symbol('|'), many1(expressionP)), rest =>
+        Expr.Or({ left: expr, right: rest }),
+      ),
+      orElse(_ => right([expr, input])),
+    ),
+)
+
 export const expressionP: Parser<Expr> = (input: string) =>
   pipe(
     input,
@@ -52,6 +64,7 @@ export const expressionP: Parser<Expr> = (input: string) =>
       falsey,
     ]),
     wrapQuantifiers,
+    wrapAlt,
   )
 
 export const parser = tuple3(optional(start), many1(expressionP), optional(end))
@@ -62,7 +75,6 @@ export const parser = tuple3(optional(start), many1(expressionP), optional(end))
 (> 5) => number greater than
 (< 5) => number less than
 [name x] => apply x on property `name`
-| => or
 /x/ => match regular expression (string values in list)
 
 */
diff --git a/src/parser/utils.ts b/src/parser/utils.ts
index a06b6c9..debff22 100644
--- a/src/parser/utils.ts
+++ b/src/parser/utils.ts
@@ -78,7 +78,7 @@ export const delimited = <T>(
   p: Parser<any>,
   a: Parser<T>,
   s: Parser<any>,
-): Parser<T> => suffixed(prefixed(p, a), s)
+): Parser<T> => recoverInput(suffixed(prefixed(p, a), s))
 
 export const satifyChar =
   (f: (c: char) => boolean): Parser<char> =>
@@ -150,13 +150,16 @@ export const optional = <T>(p: Parser<T>): Parser<Option<T>> =>
   )
 
 export const pair = <A, B>(a: Parser<A>, b: Parser<B>): Parser<[A, B]> =>
-  pipe(
-    a,
-    andThen(ra => mapTo(b, rb => [ra, rb])),
+  recoverInput(
+    pipe(
+      a,
+      andThen(ra => mapTo(b, rb => [ra, rb])),
+    ),
   )
 
 export const tuple3 = <A, B, C>(
   a: Parser<A>,
   b: Parser<B>,
   c: Parser<C>,
-): Parser<[A, B, C]> => mapTo(pair(pair(a, b), c), ([[a, b], c]) => [a, b, c])
+): Parser<[A, B, C]> =>
+  recoverInput(mapTo(pair(pair(a, b), c), ([[a, b], c]) => [a, b, c]))
-- 
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