From 0bc4c3fde2a1e6137b08a9285b7d8f028456b4ae Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@gmail.com>
Date: Fri, 24 May 2024 14:41:07 +0100
Subject: [PATCH] Move StringStream into Parsely

---
 packages/phoenix/packages/parsely/streams.js  | 52 +++++++++++++++++++
 .../puter-shell/coreutils/concept-parser.js   | 35 +------------
 2 files changed, 53 insertions(+), 34 deletions(-)
 create mode 100644 packages/phoenix/packages/parsely/streams.js

diff --git a/packages/phoenix/packages/parsely/streams.js b/packages/phoenix/packages/parsely/streams.js
new file mode 100644
index 00000000..23254b62
--- /dev/null
+++ b/packages/phoenix/packages/parsely/streams.js
@@ -0,0 +1,52 @@
+/**
+ * Base class for input streams.
+ * Defines which methods are expected for any stream implementations.
+ */
+export class ParserStream {
+    value_at (index) { throw new Error(`${this.constructor.name}.value_at() not implemented`); }
+    look () { throw new Error(`${this.constructor.name}.look() not implemented`); }
+    next () { throw new Error(`${this.constructor.name}.next() not implemented`); }
+    fork () { throw new Error(`${this.constructor.name}.fork() not implemented`); }
+    join () { throw new Error(`${this.constructor.name}.join() not implemented`); }
+
+    is_eof () {
+        return this.look().done;
+    }
+}
+
+/**
+ * ParserStream that takes a string, and processes it character by character.
+ */
+export class StringStream extends ParserStream {
+    constructor (str, startIndex = 0) {
+        super();
+        this.str = str;
+        this.i = startIndex;
+    }
+
+    value_at (index) {
+        if ( index >= this.str.length ) {
+            return { done: true, value: undefined };
+        }
+
+        return { done: false, value: this.str[index] };
+    }
+
+    look () {
+        return this.value_at(this.i);
+    }
+
+    next () {
+        const result = this.value_at(this.i);
+        this.i++;
+        return result;
+    }
+
+    fork () {
+        return new StringStream(this.str, this.i);
+    }
+
+    join (forked) {
+        this.i = forked.i;
+    }
+}
diff --git a/packages/phoenix/src/puter-shell/coreutils/concept-parser.js b/packages/phoenix/src/puter-shell/coreutils/concept-parser.js
index 7036fab4..a24b611d 100644
--- a/packages/phoenix/src/puter-shell/coreutils/concept-parser.js
+++ b/packages/phoenix/src/puter-shell/coreutils/concept-parser.js
@@ -1,5 +1,6 @@
 import { GrammarContext, standard_parsers } from '../../../packages/parsely/exports.js';
 import { Parser, UNRECOGNIZED, VALUE } from '../../../packages/parsely/parser.js';
+import { StringStream } from '../../../packages/parsely/streams.js';
 
 class NumberParser extends Parser {
     static data = {
@@ -163,39 +164,6 @@ class StringParser extends Parser {
     }
 }
 
-class StringStream {
-    constructor (str, startIndex = 0) {
-        this.str = str;
-        this.i = startIndex;
-    }
-
-    value_at (index) {
-        if ( index >= this.str.length ) {
-            return { done: true, value: undefined };
-        }
-
-        return { done: false, value: this.str[index] };
-    }
-
-    look () {
-        return this.value_at(this.i);
-    }
-
-    next () {
-        const result = this.value_at(this.i);
-        this.i++;
-        return result;
-    }
-
-    fork () {
-        return new StringStream(this.str, this.i);
-    }
-
-    join (forked) {
-        this.i = forked.i;
-    }
-}
-
 export default {
     name: 'concept-parser',
     args: {
@@ -305,7 +273,6 @@ export default {
             whitespace: _ => {},
         });
 
-        // TODO: What do we want our streams to be like?
         const input = ctx.locals.positionals.shift();
         const stream = new StringStream(input);
         try {