From 01e3de22a53d30f21a829bf5d7cebc45c4d61ea8 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Sun, 24 Jan 2021 00:12:26 +0100
Subject: Initial task queue

---
 .gitignore   |  1 +
 Cargo.lock   |  5 ++++
 Cargo.toml   |  9 ++++++
 rustfmt.toml |  1 +
 src/main.rs  | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 113 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 rustfmt.toml
 create mode 100644 src/main.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..e64fc04
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,5 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "rebel"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..7712670
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "rebel"
+version = "0.1.0"
+authors = ["Matthias Schiffer <mschiffer@universe-factory.net>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000..218e203
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1 @@
+hard_tabs = true
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..98d1b8d
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,97 @@
+use std::collections::{HashMap, HashSet};
+// use std::io::{self, Write};
+use std::io;
+// use std::process::Command;
+
+struct Task {
+	// action: String,
+	deps: Vec<String>,
+}
+
+// impl Task {
+// 	fn run(&self) -> io::Result<()> {
+// 		let output = Command::new("sh").arg("-c").arg(&self.action).output()?;
+
+// 		let stdout = io::stdout();
+// 		let mut handle = stdout.lock();
+// 		handle.write_all(&output.stdout)?;
+
+// 		Ok(())
+// 	}
+// }
+
+fn collect_subtasks<'a>(
+	queued: &HashSet<&'a str>,
+	tasks: &'a HashMap<String, Task>,
+	id: &str,
+) -> io::Result<HashSet<&'a str>> {
+	let (task_id, task) = match tasks.get_key_value(id) {
+		Some(t) => t,
+		None => {
+			return Err(io::Error::new(io::ErrorKind::NotFound, "Task not found"));
+		}
+	};
+
+	if queued.contains(id) {
+		return Err(io::Error::new(
+			io::ErrorKind::InvalidData,
+			"Dependency cycle",
+		));
+	}
+
+	let mut queued_sub = queued.clone();
+	queued_sub.insert(task_id);
+
+	let mut subtasks: HashSet<&'a str> = HashSet::new();
+	subtasks.insert(task_id);
+
+	for dep in &task.deps {
+		let deptasks = collect_subtasks(&queued_sub, tasks, dep)?;
+		subtasks = subtasks.union(&deptasks).copied().collect();
+	}
+
+	Ok(subtasks)
+}
+
+fn collect_tasks<'a>(tasks: &'a HashMap<String, Task>, id: &str) -> io::Result<HashSet<&'a str>> {
+	collect_subtasks(&HashSet::new(), tasks, id)
+}
+
+fn main() -> io::Result<()> {
+	let mut tasks = HashMap::new();
+	tasks.insert(
+		String::from("ls"),
+		Task {
+			// action: String::from("ls"),
+			deps: vec!["foo".to_owned(), "bar".to_owned()],
+		},
+	);
+	tasks.insert(
+		String::from("foo"),
+		Task {
+			// action: String::from("echo foo"),
+			deps: vec!["bar".to_owned()],
+		},
+	);
+	tasks.insert(
+		String::from("bar"),
+		Task {
+			// action: String::from("echo bar"),
+			deps: vec![],
+		},
+	);
+
+	let queue = collect_tasks(&tasks, "ls")?;
+	let (runnable, queued) = queue
+		.into_iter()
+		.partition::<HashSet<_>, _>(|id| tasks.get(*id).unwrap().deps.is_empty());
+
+	for t in &runnable {
+		println!("Runnable: {}", t);
+	}
+	for t in &queued {
+		println!("Queued: {}", t);
+	}
+
+	Ok(())
+}
-- 
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