🐣 proof of concept for Lookup

.gitignore

@@ -0,0 +1 @@
+/target

Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+
+name = "lookup"
+version = "0.1.0"
+authors = ["_"]
+edition = "2018"
+
+[dependencies]
+
+anyhow = "1.0.43"
+blake3 = "1.0.0"
+clap = "2.33.3"
+reqwest = "0.11.4"
+tokio = { version = "1.10.1", features = ["full"] }

lookup_repo/blake3/03/cf9dcb6677a84ebfe89a3859595e87da2cf07d3b18e6c9d1ea95da25bf9562

@@ -0,0 +1,3 @@
+The first build of Lookup to implement the `edit` subcommand
+
+A debug build for x64 Linux.

src/main.rs

@@ -0,0 +1,126 @@
+use std::{
+	env,
+	fs,
+	io,
+	path::{Path, PathBuf},
+	process,
+	time::SystemTime,
+};
+
+use anyhow::{
+	Context,
+	bail,
+};
+
+#[tokio::main]
+async fn main () -> anyhow::Result <()> {
+	use clap::{Arg, App, SubCommand};
+	
+	let matches = App::new ("ReactorScram/Lookup")
+	.author ("ReactorScram (Trisha)")
+	.about ("Looks up information about a file, based on its hash")
+	.subcommand (SubCommand::with_name ("edit")
+		.about ("Opens the Lookup file with $EDITOR")
+		.arg (
+			Arg::with_name ("INPUT")
+			.help ("Sets the input file to use")
+			.required (true)
+		)
+	)
+	.arg (
+		Arg::with_name ("INPUT")
+		.help ("Sets the input file to use")
+	)
+	.get_matches ();
+	
+	if let Some (matches) = matches.subcommand_matches ("edit") {
+		let input_path = Path::new (matches.value_of ("INPUT").unwrap ());
+		
+		let b3_hash = hash (input_path)?;
+		
+		let local_path = PathBuf::from ("lookup_repo").join (repo_path (&b3_hash));
+		let local_dir = local_path.parent ().unwrap ();
+		
+		let editor = env::var ("EDITOR").unwrap_or_else (|_| String::from ("nano"));
+		
+		fs::create_dir_all (local_dir)?;
+		process::Command::new ("kate")
+		.arg ("-b")
+		.arg (local_path)
+		.status ().context ("while spawning editor")?;
+		return Ok (());
+	}
+	
+	let input_path = Path::new (matches.value_of ("INPUT").unwrap ());
+	
+	let b3_hash = hash (input_path)?;
+	
+	let local_path = PathBuf::from ("lookup_repo").join (repo_path (&b3_hash));
+	
+	println! ("Local path: {:?}", local_path);
+	
+	Ok (())
+}
+
+fn hash (input_path: &Path) -> anyhow::Result <blake3::Hash> 
+{
+	let mut hasher = blake3::Hasher::new ();
+	
+	{
+		let mod_guard = FileModificationGuard::try_new (input_path)?;
+		let mut input_file = fs::File::open (input_path)?;
+		
+		io::copy (&mut input_file, &mut hasher)?;
+		
+		mod_guard.check ().context ("while hashing input file")?;
+	}
+	
+	Ok (hasher.finalize ())
+}
+
+fn repo_path (b3_hash: &blake3::Hash) -> PathBuf {
+	let b3_hex = b3_hash.to_hex ();
+	
+	PathBuf::from ("blake3")
+	.join (&b3_hex [0..2])
+	.join (&b3_hex [2..])
+}
+
+struct FileModificationGuard <'a> {
+	path: &'a Path,
+	metadata_start: CommonFileMetadata,
+}
+
+#[derive (PartialEq)]
+struct CommonFileMetadata {
+	len: u64,
+	modified: SystemTime
+}
+
+impl <'a> FileModificationGuard <'a> {
+	fn try_new (path: &'a Path) -> anyhow::Result <Self> {
+		Ok (Self {
+			path,
+			metadata_start: CommonFileMetadata::try_new (path)?,
+		})
+	}
+	
+	fn check (&self) -> anyhow::Result <()> {
+		let md = CommonFileMetadata::try_new (self.path)?;
+		if md != self.metadata_start {
+			bail! ("File metadata changed");
+		}
+		
+		Ok (())
+	}
+}
+
+impl CommonFileMetadata {
+	fn try_new (path: &Path) -> anyhow::Result <Self> {
+		let md = fs::metadata (path)?;
+		Ok (Self {
+			len: md.len (),
+			modified: md.modified ()?,
+		})
+	}
+}