From f9f8f326740644f24bcb14132cd37d6c0e3decba Mon Sep 17 00:00:00 2001
From: Jan-Erik Rediger <janerik@fnordig.de>
Date: Thu, 16 May 2024 20:19:07 +0200
Subject: [PATCH] strfry a string

---
 .gitignore |  1 +
 Cargo.lock |  7 +++++++
 Cargo.toml |  8 ++++++++
 LICENSE    | 20 ++++++++++++++++++
 README.md  | 10 +++++++++
 src/lib.rs | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 106 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 LICENSE
 create mode 100644 README.md
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..4d92684
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "strfry"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..d13cb3f
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "strfry"
+version = "0.1.0"
+edition = "2021"
+description = "randomize a string"
+license = "MIT"
+
+[dependencies]
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..e4be788
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,20 @@
+Copyright (c) 2024 Jan-Erik Rediger
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5be10af
--- /dev/null
+++ b/README.md
@@ -0,0 +1,10 @@
+# Randomize a string
+
+Randomizes the contents of string by randomly swapping characters in the string.
+The result is an anagram of string.
+
+```rust
+use strfry::strfry;
+
+let anagram = strfry("i am a weakish speller");
+```
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..9e8356f
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,60 @@
+//! Randomize a string
+//!
+//! Randomizes the contents of string by randomly swapping characters in the string.
+//! The result is an anagram of string.
+//!
+//! ```rust
+//! # use strfry::strfry;
+//! let anagram = strfry("i am a weakish speller");
+//! ```
+
+use std::collections::hash_map::RandomState;
+use std::hash::{BuildHasher, Hasher};
+
+fn random() -> usize {
+    RandomState::new().build_hasher().finish() as usize
+}
+
+/// randomize a string
+///
+/// Randomizes the contents of string by randomly swapping characters in the string.
+/// Panics when the string contains non-ASCII characters.
+/// The result is an anagram of string.
+pub fn strfry(string: &str) -> String {
+    assert!(string.is_ascii());
+
+    let mut output = string.to_string();
+    {
+        // SAFETY: It's all ASCII and we just gonna swap around things.
+        let string = unsafe { output.as_bytes_mut() };
+        let len = string.len();
+
+        for i in 0..len {
+            let j = random() % (len - i) + i;
+            string.swap(i, j);
+        }
+    }
+
+    output
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let input = "hello world!";
+        assert_eq!(input.len(), strfry(&input).len());
+    }
+
+    #[test]
+    fn randomizes() {
+        for _ in 0..100 {
+            assert!(matches!(
+                &*strfry("abc"),
+                "abc" | "acb" | "bac" | "bca" | "cab" | "cba"
+            ));
+        }
+    }
+}