From 7eda8bb721bab2ec4c00517a2eadd07f0a5ddac8 Mon Sep 17 00:00:00 2001
From: emma <emma@tebibyte.media>
Date: Wed, 27 Dec 2023 15:44:19 -0700
Subject: [PATCH] fop(1): working prototype

---
 GNUmakefile |  3 +++
 src/fop.rs  | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 src/fop.rs

diff --git a/GNUmakefile b/GNUmakefile
index ca38f5c..35da1d9 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -60,6 +60,9 @@ test: build
 false: src/false.rs build_dir
 	$(RUSTC) $(RUSTCFLAGS) -o build/bin/false src/false.rs
 
+fop: src/fop.rs build_dir
+	$(RUSTC) $(RUSTCFLAGS) -o build/bin/fop src/fop.rs
+
 intcmp: src/intcmp.c build_dir
 	$(CC) $(CFLAGS) -o build/bin/intcmp src/intcmp.c
 
diff --git a/src/fop.rs b/src/fop.rs
new file mode 100644
index 0000000..9c25463
--- /dev/null
+++ b/src/fop.rs
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2023 Emma Tebibyte <emma@tebibyte.media>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU Affero General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option) any
+ * later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/.
+ */
+
+use std::{
+	env::args,
+	io::{ Read, stdin, Write },
+	process::{ Command, exit, Stdio },
+};
+
+fn main() {
+	let argv = args().collect::<Vec<String>>();
+
+	let index = match argv.get(1) {
+		Some(i) => {
+			i.parse::<usize>().unwrap_or_else(|_| {
+				eprintln!("{}: {}: Not an integer.", argv[0], i);
+				exit(1);
+			})
+		},
+		None => {
+			eprintln!("Usage: {} index command args...", argv[0]);
+			exit(1);
+		},
+	};
+
+	let mut buf = String::new();
+	stdin().read_to_string(&mut buf).unwrap();
+	let mut fields = buf.split('␞').collect::<Vec<&str>>();
+
+	argv.get(2).unwrap_or_else(|| {
+		eprintln!("Usage: {} index command args...", argv[0]);
+		exit(1);
+	});
+
+	let opts = argv.iter().clone().skip(3).collect::<Vec<&String>>();
+
+	let mut spawned = Command::new(argv.get(2).unwrap())
+		.args(opts)
+		.stdin(Stdio::piped())
+		.stdout(Stdio::piped())
+		.spawn()
+		.unwrap();
+
+	let field = fields.get(index).unwrap_or_else(|| {
+		eprintln!("{}: {}: No such index in input.", argv[0], index.to_string());
+		exit(1);
+	});
+
+	if let Some(mut child_stdin) = spawned.stdin.take() {
+		child_stdin.write_all(field.as_bytes()).unwrap();
+		drop(child_stdin);
+	}
+
+	let output = spawned.wait_with_output().unwrap();
+
+	let new_field = String::from_utf8(output.stdout).unwrap();
+
+	fields[index] = &new_field;
+
+	print!("{}", fields.join("␞"));
+}