commit 0647ac4c48068e5d516c1e7a3970c108bf51f1a7
Author: Adrian Wannenmacher <tfld@tfld.dev>
Date:   Sun Sep 24 05:38:22 2023 +0200

    initial implementation

diff --git a/.gitignore b/.gitignore
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+name = "windows_x86_64_gnullvm"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+
+[[package]]
+name = "winnow"
+version = "0.5.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c2e3184b9c4e92ad5167ca73039d0c42476302ab603e2fec4487511f38ccefc"
+dependencies = [
+ "memchr",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..655020c
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "tree-owners"
+version = "0.1.0"
+edition = "2021"
+authors = ["Adrian Wannenmacher <tfld@tfld.dev>"]
+description = "Find all owners (user and group) inside a directory tree."
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.75"
+clap = { version = "4.4.4", features = ["derive", "cargo", "wrap_help"] }
+file-owner = "0.1.2"
+human-panic = "1.2.0"
+serde = { version = "1.0.188", features = ["derive"] }
+serde_json = "1.0.107"
diff --git a/src/id.rs b/src/id.rs
new file mode 100644
index 0000000..395f3a1
--- /dev/null
+++ b/src/id.rs
@@ -0,0 +1,27 @@
+use std::{collections::BTreeSet, fmt::Display};
+
+use serde::Serialize;
+
+#[derive(Debug, Default, Serialize)]
+pub struct Ids {
+    pub users: BTreeSet<u32>,
+    pub groups: BTreeSet<u32>,
+}
+
+impl Display for Ids {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "users:")?;
+        for user in &self.users {
+            writeln!(f, "    {user}")?;
+        }
+
+        writeln!(f, "")?;
+
+        writeln!(f, "groups:")?;
+        for group in &self.groups {
+            writeln!(f, "    {group}")?;
+        }
+
+        Ok(())
+    }
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..e012313
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,75 @@
+use std::{
+    fs::read_dir,
+    os::linux::fs::MetadataExt,
+    path::{Path, PathBuf},
+};
+
+use anyhow::{ensure, Context, Result};
+use clap::Parser;
+
+use crate::{id::Ids, name::Names, output::Output};
+
+mod id;
+mod name;
+mod output;
+
+fn main() -> Result<()> {
+    human_panic::setup_panic!();
+    let args = Args::parse();
+
+    let mut ids = Ids::default();
+    for root in args.roots {
+        fs_entry(&root, &mut ids)?;
+    }
+
+    let output: Box<dyn Output> = match args.raw {
+        false => Box::new(Names::try_from(ids).context("failed to get names")?),
+        true => Box::new(ids),
+    };
+    let output = match args.json {
+        false => output.human_readable(),
+        true => output.json().context("failed json serialization")?,
+    };
+    println!("{output}");
+
+    Ok(())
+}
+
+#[derive(Debug, Parser)]
+#[clap(author, about, version)]
+struct Args {
+    /// Whether to output data as json.
+    #[clap(long)]
+    pub json: bool,
+
+    /// Whether to output raw uid and gid numbers.
+    #[clap(long)]
+    pub raw: bool,
+
+    /// The roots to use for discovery.
+    pub roots: Vec<PathBuf>,
+}
+
+fn fs_entry(entry: &Path, summary: &mut Ids) -> Result<()> {
+    let display = entry.display();
+    ensure!(
+        entry.is_symlink() || entry.exists(),
+        format!("{} doesn't exist", display)
+    );
+
+    let meta = entry
+        .symlink_metadata()
+        .context(format!("failed to get metadata for {}", display))?;
+    summary.users.insert(meta.st_uid());
+    summary.groups.insert(meta.st_gid());
+
+    if entry.is_dir() {
+        let children = read_dir(entry).context(format!("failed to read dir {}", display))?;
+        for e in children {
+            let e = e.context(format!("invalid child for {}", display))?;
+            fs_entry(&e.path(), summary).context(format!("failed to read child of {}", display))?;
+        }
+    }
+
+    Ok(())
+}
diff --git a/src/name.rs b/src/name.rs
new file mode 100644
index 0000000..b46709f
--- /dev/null
+++ b/src/name.rs
@@ -0,0 +1,58 @@
+use std::{collections::BTreeSet, fmt::Display};
+
+use anyhow::{anyhow,Error, Result};
+use file_owner::{Owner, Group};
+use serde::Serialize;
+
+use crate::id::Ids;
+
+#[derive(Debug, Default, Serialize)]
+pub struct Names {
+    pub users: BTreeSet<String>,
+    pub groups: BTreeSet<String>,
+}
+
+impl Display for Names {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "users:")?;
+        for user in &self.users {
+            writeln!(f, "    {user}")?;
+        }
+
+        writeln!(f, "")?;
+
+        writeln!(f, "groups:")?;
+        for group in &self.groups {
+            writeln!(f, "    {group}")?;
+        }
+
+        Ok(())
+    }
+}
+
+impl TryFrom<Ids> for Names {
+    type Error = Error;
+
+    fn try_from(value: Ids) -> Result<Self> {
+        Ok(Self {
+            users: value
+                .users
+                .into_iter()
+                .map(|u| match Owner::from_uid(u).name() {
+                    Ok(Some(name)) => Ok(name),
+                    Ok(None) => Err(anyhow!("no name for user {u}")),
+                    Err(_) => Err(anyhow!("failed to get name for user {u}")),
+                })
+                .collect::<Result<_>>()?,
+            groups: value
+                .groups
+                .into_iter()
+                .map(|g| match Group::from_gid(g).name() {
+                    Ok(Some(name)) => Ok(name),
+                    Ok(None) => Err(anyhow!("no name for group {g}")),
+                    Err(_) => Err(anyhow!("failed to get name for group {g}")),
+                })
+                .collect::<Result<_>>()?,
+        })
+    }
+}
diff --git a/src/output.rs b/src/output.rs
new file mode 100644
index 0000000..dbe76f0
--- /dev/null
+++ b/src/output.rs
@@ -0,0 +1,19 @@
+use serde::Serialize;
+
+pub trait Output {
+    fn human_readable(&self) -> String;
+    fn json(&self) -> Result<String, serde_json::Error>;
+}
+
+impl<T> Output for T
+where
+    T: ToString + Serialize,
+{
+    fn human_readable(&self) -> String {
+        self.to_string()
+    }
+
+    fn json(&self) -> Result<String, serde_json::Error> {
+        serde_json::to_string_pretty(&self)
+    }
+}