From db497bb9950648c056c079c591b239ad4932b5c9 Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Mon, 24 Jan 2022 19:19:15 +0530
Subject: feat(parser): implements min-max quantifier parser

---
 src/eval/index.ts   |  4 +---
 src/parser/index.ts | 21 ++++++++++++++++++++-
 src/types.ts        |  3 +++
 3 files changed, 24 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/eval/index.ts b/src/eval/index.ts
index 8e162b4..ed757e7 100644
--- a/src/eval/index.ts
+++ b/src/eval/index.ts
@@ -1,7 +1,7 @@
 import { identity, pipe } from 'fp-ts/function'
 import { filter, takeLeftWhile, zip, zipWith } from 'fp-ts/Array'
 import * as Option from 'fp-ts/Option'
-import { Expr, ListExpr } from '../types'
+import { index, Expr, ListExpr } from '../types'
 import { match } from '../utils'
 
 export interface MatchGroupIndexed<T = any> {
@@ -18,8 +18,6 @@ const group = <T>(value: T, index: number): MatchGroupIndexed<T> => ({
   index,
 })
 
-type index = number
-
 const indexed = <T>(ls: T[]): Array<[number, T]> => ls.map((x, i) => [i, x])
 
 const accumulateSkip = () => {
diff --git a/src/parser/index.ts b/src/parser/index.ts
index 2db91a4..a336b83 100644
--- a/src/parser/index.ts
+++ b/src/parser/index.ts
@@ -23,7 +23,7 @@ import {
   tuple3,
   whitespaces0,
 } from './utils'
-import { Expr, ListExpr, Literal } from '../types'
+import { Expr, index, ListExpr, Literal } from '../types'
 import * as Option from 'fp-ts/Option'
 import { snd } from 'fp-ts/Tuple'
 
@@ -36,6 +36,13 @@ const anyBool = mapTo(symbol('\\b'), _ => Expr.AnyBool())
 const truthy = mapTo(symbol('\\T'), _ => Expr.Truthy())
 const falsey = mapTo(symbol('\\F'), _ => Expr.Falsey())
 
+const parseQuantifier = (s: Option.Option<string>, def: index): index =>
+  pipe(
+    s,
+    Option.map(s => parseInt(s, 10)),
+    Option.getOrElse(() => def),
+  )
+
 const wrapQuantifiers: (e: ParserResult<Expr>) => ParserResult<Expr> =
   Either.chain(([expr, input]) =>
     pipe(
@@ -44,6 +51,18 @@ const wrapQuantifiers: (e: ParserResult<Expr>) => ParserResult<Expr> =
         mapTo(symbol('*'), _ => Expr.ZeroOrMore({ expr })),
         mapTo(symbol('+'), _ => Expr.OneOrMore({ expr })),
         mapTo(symbol('?'), _ => Expr.Optional({ expr })),
+        mapTo(
+          pair(
+            prefixed(symbol('{'), optional(digits)),
+            delimited(symbol(','), optional(digits), symbol('}')),
+          ),
+          ([min, max]) =>
+            Expr.MinMax({
+              expr,
+              min: parseQuantifier(min, 0),
+              max: parseQuantifier(max, Infinity),
+            }),
+        ),
       ]),
       Either.orElse(_ => Either.right([expr, input])),
     ),
diff --git a/src/types.ts b/src/types.ts
index 473f5e1..dd40ce9 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -3,6 +3,8 @@ import { constructors, Union } from './utils'
 
 type _ = never
 
+export type index = number
+
 export type Literal = Union<{
   String: string
   Number: number
@@ -15,6 +17,7 @@ export type Expr = Union<{
   End: _
   Optional: { expr: Expr }
   OneOrMore: { expr: Expr }
+  MinMax: { expr: Expr, min: index, max: index }
   ZeroOrMore: { expr: Expr }
   AnyItem: _
   Or: { exprs: Expr[] }
-- 
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