Initial commit

src/main.rs

@@ -0,0 +1,211 @@
+mod config;
+
+use chrono::{DateTime, FixedOffset, Local};
+#[macro_use]
+extern crate log;
+
+use clap::Parser;
+use config::Config;
+use log::LevelFilter;
+use std::collections::{BinaryHeap, HashSet};
+use std::fs;
+use std::io;
+use std::path::PathBuf;
+use thiserror::Error;
+
+type FileName = DateTime<FixedOffset>;
+
+#[derive(Parser)]
+struct Opt {
+    config: PathBuf,
+
+    /// Log more stuff
+    #[clap(long, short, parse(from_occurrences))]
+    verbose: u8,
+
+    /// Do not output anything but errors.
+    #[clap(long, short)]
+    quiet: bool,
+
+    /// Do not delete anything
+    #[clap(long, short)]
+    dry_run: bool,
+}
+
+#[derive(Debug, Error)]
+enum Error {
+    #[error("I/O error: {0}")]
+    IO(#[from] io::Error),
+
+    #[error("Failed to parse config: {0}")]
+    ParseConfig(#[from] toml::de::Error),
+
+    #[error("Managed to overflow a DateTime. What did you do??")]
+    DateTimeOverflow,
+
+    #[error("Failed to delete btrfs subvolume: {0}")]
+    DeleteSubvolume(String),
+}
+
+fn main() {
+    let opt = Opt::parse();
+
+    let log_level = match opt.verbose {
+        0 if opt.quiet => LevelFilter::Error,
+        0 => LevelFilter::Info,
+        1 => LevelFilter::Debug,
+        2.. => LevelFilter::Trace,
+    };
+
+    pretty_env_logger::formatted_builder()
+        .filter(None, log_level)
+        .init();
+
+    if let Err(e) = run(&opt) {
+        println!("{e}");
+    }
+}
+
+fn run(opt: &Opt) -> Result<(), Error> {
+    let config = fs::read_to_string(&opt.config)?;
+    let config: Config = toml::from_str(&config)?;
+    debug!("periods:");
+    for period in &config.periods {
+        debug!(
+            "  length={:?}, chunk_size={:?}",
+            period.period_length, period.chunk_size
+        );
+    }
+
+    info!("scanning directory {:?}", config.path);
+
+    let mut files = BinaryHeap::new();
+    for entry in fs::read_dir(&config.path)? {
+        let name = entry?.file_name();
+        let name = name.to_string_lossy();
+        if let Ok(time) = DateTime::parse_from_rfc3339(&name) {
+            trace!("found \"{name}\"");
+            files.push(time);
+        }
+    }
+    let files = files.into_sorted_vec();
+
+    let keep_files = check_files_to_keep(&config, &files)?;
+
+    info!("final decision:");
+    for &file in &files {
+        let keep_file = keep_files.contains(&file);
+
+        if keep_file {
+            debug!("  {file} KEEP");
+        } else {
+            info!("  {file} DELETE");
+            if opt.dry_run {
+                debug!("dry run enabled, file not deleted");
+            } else {
+                delete_file(&config, file)?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
+fn check_files_to_keep(config: &Config, files: &[FileName]) -> Result<HashSet<FileName>, Error> {
+    let mut files = files.to_vec();
+
+    let mut keep_files = HashSet::new();
+
+    let now = Local::now();
+    let mut cursor = now;
+
+    for period in &config.periods {
+        if files.is_empty() {
+            trace!("no more files, skipping remaining periods");
+            break;
+        }
+
+        let period_length = chrono::Duration::from_std(period.period_length)
+            .map_err(|_| Error::DateTimeOverflow)?;
+        let chunk_size =
+            chrono::Duration::from_std(period.chunk_size).map_err(|_| Error::DateTimeOverflow)?;
+
+        if period_length < chunk_size {
+            panic!("invalid period configuration");
+        }
+
+        // NOTE: we are looking backwards in time, so all checks and additions need to be inverted
+        let period_end = cursor - period_length;
+
+        while cursor > period_end {
+            if files.is_empty() {
+                trace!("no more files, skipping remaining chunks");
+                break;
+            }
+
+            let start_of_chunk = cursor;
+            let end_of_chunk = cursor - chunk_size;
+            cursor = end_of_chunk;
+
+            let mut chunk_file_to_keep = None;
+
+            trace!("processing chunk {end_of_chunk} -> {start_of_chunk}");
+            loop {
+                let file = match files.pop() {
+                    Some(file) => file,
+                    None => break,
+                };
+
+                if file > start_of_chunk {
+                    trace!("{file} outside of chunk bounds. ignoring.");
+                    keep_files.insert(file);
+                } else if file > end_of_chunk {
+                    trace!("{file} is in chunk. beaten by {chunk_file_to_keep:?}");
+                    chunk_file_to_keep.get_or_insert(file);
+                } else {
+                    trace!("reached end of chunk");
+                    files.push(file); // put the file back in the queue
+                    break;
+                }
+            }
+
+            if let Some(file) = chunk_file_to_keep {
+                trace!("keeping files {file}");
+                keep_files.insert(file);
+            }
+        }
+
+        cursor = period_end;
+    }
+
+    Ok(keep_files)
+}
+
+fn delete_file(config: &Config, file: FileName) -> Result<(), Error> {
+    let file_path = config.path.join(file.to_rfc3339());
+
+    if config.btrfs {
+        trace!("btrfs subvolume delete {file_path:?}");
+        use std::process::Command;
+        let output = Command::new("btrfs")
+            .args(["subvolume", "delete"])
+            .arg(file_path)
+            .output()?;
+
+        if !output.status.success() {
+            let msg = String::from_utf8(output.stderr)
+                .unwrap_or_else(|_| "Failed to capture stderr".to_string());
+            return Err(Error::DeleteSubvolume(msg));
+        };
+    } else {
+        if file_path.is_dir() {
+            trace!("rm -r {file_path:?}");
+            fs::remove_dir_all(file_path)?;
+        } else {
+            trace!("rm {file_path:?}");
+            fs::remove_file(file_path)?;
+        }
+    }
+
+    Ok(())
+}