From ecd9f500299f067ce401f31e7a14ea5cae1aaf39 Mon Sep 17 00:00:00 2001
From: martin <me@martials.no>
Date: Sun, 10 Sep 2023 19:46:41 +0200
Subject: [PATCH] Implemented failure function algorithm with a simple
 interface

---
 src/app.tsx                   |  2 ++
 src/pages/failureFunction.tsx | 66 +++++++++++++++++++++++++++++++++++
 src/utils/failureFunction.ts  | 23 ++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 src/pages/failureFunction.tsx
 create mode 100644 src/utils/failureFunction.ts

diff --git a/src/app.tsx b/src/app.tsx
index 1ec60f6..3fb1d92 100644
--- a/src/app.tsx
+++ b/src/app.tsx
@@ -4,11 +4,13 @@ import TruthTablePage from "./pages/truth-table";
 import PageNotFound from "./pages/404";
 import { render } from "solid-js/web";
 import { type Component } from "solid-js";
+import FailureFunctionPage from "./pages/failureFunction";
 
 const App: Component = () => (
     <Routes>
         <Route path={ "/" } element={ <HomePage /> } />
         <Route path={ "/simplify-truths" } element={ <TruthTablePage /> } />
+        <Route path={ "/failure-function" } element={ <FailureFunctionPage /> } />
         <Route path={ "*" } element={ <PageNotFound /> } />
     </Routes>
 );
diff --git a/src/pages/failureFunction.tsx b/src/pages/failureFunction.tsx
new file mode 100644
index 0000000..6129755
--- /dev/null
+++ b/src/pages/failureFunction.tsx
@@ -0,0 +1,66 @@
+/* @refresh reload */
+
+import { Component, createSignal } from "solid-js";
+import { Input } from "../components/input";
+import Layout from "../components/layout";
+import { failureFunction } from "../utils/failureFunction";
+import { For } from "solid-js/web";
+
+type FFProps = { char: string, index: number }
+
+const FailureFunctionPage: Component = () => {
+    let inputRef: HTMLInputElement | undefined = undefined;
+
+    const [result, setResult] = createSignal<ReadonlyArray<FFProps>>()
+
+    function onSubmit(e: Event) {
+        e.preventDefault()
+        if (inputRef) {
+            const input = inputRef.value;
+            const splitInput = input.split("")
+            const output = failureFunction(input)
+
+            if (output.length !== splitInput.length) {
+                console.error("Something went wrong")
+            }
+            else {
+                setResult(output.map((value, index) => {
+                    return { char: splitInput[index], index: value } as FFProps
+                }))
+            }
+        }
+    }
+
+    return (
+        <Layout title={ "Failure function" }>
+            <div class={ "container mx-auto max-w-2xl overflow-auto" }>
+                <p>Failure Function</p>
+                <form onsubmit={ onSubmit }>
+                    <Input ref={ inputRef } inputClass={ "rounded-2xl w-full h-10 px-3" } />
+                </form>
+                <table class={ "mb-3" }>
+                    <thead>
+                        <tr>
+                            <For each={ result() }>
+                                { ({ char }) =>
+                                    <th class={ "border border-black" }>{ char }</th>
+                                }
+                            </For>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        <tr>
+                            <For each={ result() }>
+                                { ({ index }) =>
+                                    <td class={ "border border-black" }>{ index }</td>
+                                }
+                            </For>
+                        </tr>
+                    </tbody>
+                </table>
+            </div>
+        </Layout>
+    );
+}
+
+export default FailureFunctionPage;
diff --git a/src/utils/failureFunction.ts b/src/utils/failureFunction.ts
new file mode 100644
index 0000000..e39b48c
--- /dev/null
+++ b/src/utils/failureFunction.ts
@@ -0,0 +1,23 @@
+export function failureFunction(P: String, m = P.length): number[] {
+    // No proper prefix for string of length 1:
+    const arr = [0]
+    let i = 0, j = 1
+
+    while (j < m) {
+        if (P[i] == P[j]) {
+            i++
+            arr.push(i)
+            j++;
+        }
+        // The first character didn't match:
+        else if (i == 0) {
+            arr.push(0)
+            j++
+        }
+        // Mismatch after at least one matching character:
+        else {
+            i = arr[i - 1]
+        }
+    }
+    return arr
+}