From 0f6546b5c2d93c84e07fa4f7201ef18daa560734 Mon Sep 17 00:00:00 2001
From: Vincent Ollivier <v@vinc.cc>
Date: Sun, 15 Sep 2024 10:41:36 +0200
Subject: [PATCH] Add diff command

---
 src/usr/diff.rs  | 121 +++++++++++++++++++++++++++++++++++++++++++++++
 src/usr/mod.rs   |   1 +
 src/usr/shell.rs |  11 +++--
 3 files changed, 128 insertions(+), 5 deletions(-)
 create mode 100644 src/usr/diff.rs

diff --git a/src/usr/diff.rs b/src/usr/diff.rs
new file mode 100644
index 00000000..1253d2e3
--- /dev/null
+++ b/src/usr/diff.rs
@@ -0,0 +1,121 @@
+use crate::api::console::Style;
+use crate::api::fs;
+use crate::api::process::ExitCode;
+
+use core::cmp;
+use alloc::string::String;
+use alloc::vec::Vec;
+use alloc::vec;
+
+#[derive(Debug, PartialEq)]
+enum Diff {
+    Equal(String),
+    Insert(String),
+    Delete(String),
+}
+
+fn diff(old: &str, new: &str) -> Vec<Diff> {
+    let old: Vec<&str> = old.lines().collect();
+    let new: Vec<&str> = new.lines().collect();
+    backtrack(&old, &new, &lcs(&old, &new))
+}
+
+fn lcs(old: &[&str], new: &[&str]) -> Vec<Vec<usize>> {
+    let n = old.len();
+    let m = new.len();
+    let mut lcs = vec![vec![0; m + 1]; n + 1];
+
+    for i in 0..n {
+        for j in 0..m {
+            if old[i] == new[j] {
+                lcs[i + 1][j + 1] = lcs[i][j] + 1;
+            } else {
+                lcs[i + 1][j + 1] = cmp::max(lcs[i][j + 1], lcs[i + 1][j]);
+            }
+        }
+    }
+
+    lcs
+}
+
+fn backtrack(old: &[&str], new: &[&str], lcs: &[Vec<usize>]) -> Vec<Diff> {
+    let mut diff = Vec::new();
+    let mut i = old.len();
+    let mut j = new.len();
+
+    while i > 0 && j > 0 {
+        if old[i - 1] == new[j - 1] {
+            diff.push(Diff::Equal(old[i - 1].into()));
+            i -= 1;
+            j -= 1;
+        } else if lcs[i][j - 1] > lcs[i - 1][j] {
+            diff.push(Diff::Insert(new[j - 1].into()));
+            j -= 1;
+        } else {
+            diff.push(Diff::Delete(old[i - 1].into()));
+            i -= 1;
+        }
+    }
+
+    while i > 0 {
+        diff.push(Diff::Delete(old[i - 1].into()));
+        i -= 1;
+    }
+
+    while j > 0 {
+        diff.push(Diff::Insert(new[j - 1].into()));
+        j -= 1;
+    }
+
+    diff.reverse();
+    diff
+}
+
+pub fn main(args: &[&str]) -> Result<(), ExitCode> {
+    let csi_insert = Style::color("green");
+    let csi_delete = Style::color("red");
+    let csi_reset = Style::reset();
+    if let Ok(old) = fs::read_to_string(args[1]) {
+        if let Ok(new) = fs::read_to_string(args[2]) {
+            for op in diff(&old, &new) {
+                match op {
+                    Diff::Equal(line) => {
+                        println!(" {}", line);
+                    }
+                    Diff::Delete(line) => {
+                        println!("{}-{}{}", csi_delete, line, csi_reset);
+                    }
+                    Diff::Insert(line) => {
+                        println!("{}+{}{}", csi_insert, line, csi_reset);
+                    }
+                }
+            }
+        }
+    }
+    Ok(())
+}
+
+#[test_case]
+fn test_diff() {
+    assert_eq!(
+        diff("a", "a"),
+        vec![
+            Diff::Equal("a".into())
+        ]
+    );
+    assert_eq!(
+        diff("a", "b"),
+        vec![
+            Diff::Insert("b".into()),
+            Diff::Delete("a".into())
+        ]
+    );
+    assert_eq!(
+        diff("a\nb\nc\n", "a\nc\n"),
+        vec![
+            Diff::Equal("a".into()),
+            Diff::Delete("b".into()),
+            Diff::Equal("c".into())
+        ]
+    );
+}
diff --git a/src/usr/mod.rs b/src/usr/mod.rs
index 2b87ec87..df7b1458 100644
--- a/src/usr/mod.rs
+++ b/src/usr/mod.rs
@@ -6,6 +6,7 @@ pub mod date;
 pub mod decode;
 pub mod delete;
 pub mod dhcp;
+pub mod diff;
 pub mod disk;
 pub mod edit;
 pub mod elf;
diff --git a/src/usr/shell.rs b/src/usr/shell.rs
index d3736eeb..cf535bef 100644
--- a/src/usr/shell.rs
+++ b/src/usr/shell.rs
@@ -14,12 +14,12 @@ use alloc::vec::Vec;
 use core::sync::atomic::{fence, Ordering};
 
 // TODO: Scan /bin
-const AUTOCOMPLETE_COMMANDS: [&str; 39] = [
+const AUTOCOMPLETE_COMMANDS: [&str; 40] = [
     "2048", "calc", "chess", "copy", "date", "decode", "delete", "dhcp",
-    "disk", "edit", "elf", "encode", "env", "goto", "hash", "help", "hex",
-    "host", "http", "httpd", "install", "keyboard", "life", "lisp", "list",
-    "memory", "move", "net", "pci", "quit", "read", "shell", "socket", "tcp",
-    "time", "user", "vga", "view", "write",
+    "diff", "disk", "edit", "elf", "encode", "env", "goto", "hash", "help",
+    "hex", "host", "http", "httpd", "install", "keyboard", "life", "lisp",
+    "list", "memory", "move", "net", "pci", "quit", "read", "shell", "socket",
+    "tcp", "time", "user", "vga", "view", "write",
 ];
 
 struct Config {
@@ -524,6 +524,7 @@ fn dispatch(args: &[&str], config: &mut Config) -> Result<(), ExitCode> {
         "decode"   => usr::decode::main(args),
         "delete"   => usr::delete::main(args),
         "dhcp"     => usr::dhcp::main(args),
+        "diff"     => usr::diff::main(args),
         "disk"     => usr::disk::main(args),
         "edit"     => usr::edit::main(args),
         "elf"      => usr::elf::main(args),