feat: initially working export command

src/backup/delta.rs

@@ -1,5 +1,6 @@
 use super::State;
 use serde::{Deserialize, Serialize};
+use std::borrow::Borrow;
 use std::fmt;
 
 /// Represents the changes relative to the previous backup
@@ -26,7 +27,6 @@ impl Delta {
     ///
     /// The union of two deltas is a delta that produces the same state as if you were to apply
     /// both deltas in-order. Note that this operation is not commutative.
-    #[allow(dead_code)]
     pub fn union(&self, delta: &Self) -> Self {
         let mut out = self.clone();
 
@@ -110,20 +110,35 @@ impl Delta {
         out
     }
 
-    pub fn contributions(deltas: &[Self]) -> Vec<State> {
-        let mut contributions: Vec<State> = Vec::with_capacity(deltas.len());
-        // contributions[deltas.len() - 1] = deltas[deltas.len() - 1].added.clone();
+    /// Given a chain of deltas, ordered from last to first, calculate the "contribution" for each
+    /// state.
+    ///
+    /// The contribution of a delta in a given chain is defined as the parts of the state produced
+    /// by this chain that are actually provided by this delta. This comes down to calculating the
+    /// strict difference of this delta and all of its successive deltas.
+    pub fn contributions<I>(deltas: I) -> Vec<State>
+    where
+        I: IntoIterator,
+        I::Item: Borrow<Delta>,
+    {
+        let mut contributions: Vec<State> = Vec::new();
 
-        // for (i, delta) in deltas.iter().enumerate() {
-        //     // The base case for the contributions is every added file
-        //     let mut contribution = delta.clone();
+        let mut deltas = deltas.into_iter();
 
-        //     for other_delta in &deltas[i + 1..] {
-        //         contribution = contribution.difference(other_delta);
-        //     }
+        if let Some(first_delta) = deltas.next() {
+            // From last to first, we calculate the strict difference of the delta with the union of all its
+            // following deltas. The list of added files of this difference is the contribution for
+            // that delta.
+            contributions.push(first_delta.borrow().added.clone());
+            let mut union_future = first_delta.borrow().clone();
 
-        //     contributions.push(contribution);
-        // }
+            for delta in deltas {
+                contributions.push(delta.borrow().strict_difference(&union_future).added);
+                union_future = union_future.union(delta.borrow());
+            }
+        }
+
+        // contributions.reverse();
 
         contributions
     }

src/backup/manager/meta.rs

@@ -4,7 +4,7 @@ use serde::Deserialize;
 use serde::Serialize;
 use std::collections::HashMap;
 use std::io;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 /// Manages a collection of backup layers, allowing them to be utilized as a single object.
 pub struct MetaManager<T>
@@ -129,6 +129,17 @@ where
             .map(|manager| manager.restore_backup(start_time, dirs))
     }
 
+    pub fn export_backup<P: AsRef<Path>>(
+        &self,
+        layer: &str,
+        start_time: chrono::DateTime<Utc>,
+        output_path: P,
+    ) -> Option<io::Result<()>> {
+        self.managers
+            .get(layer)
+            .map(|manager| manager.export_backup(start_time, output_path))
+    }
+
     pub fn managers(&self) -> &HashMap<String, Manager<T>> {
         &self.managers
     }

src/backup/manager/mod.rs

@@ -4,15 +4,17 @@ mod meta;
 pub use config::ManagerConfig;
 pub use meta::MetaManager;
 
-use super::{Backup, State};
+use super::{Backup, Delta, State};
 use crate::other;
 use chrono::SubsecRound;
 use chrono::Utc;
+use flate2::write::GzEncoder;
+use flate2::Compression;
 use serde::Deserialize;
 use serde::Serialize;
-use std::fs::File;
+use std::fs::{File, OpenOptions};
 use std::io;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 /// Manages a single backup layer consisting of one or more chains of backups.
 pub struct Manager<T>
@@ -187,6 +189,47 @@ where
         Err(other("Unknown backup."))
     }
 
+    pub fn export_backup<P: AsRef<Path>>(
+        &self,
+        start_time: chrono::DateTime<Utc>,
+        output_path: P,
+    ) -> io::Result<()> {
+        // Iterate over each chain, skipping elements until the element with the given start time
+        // is possibly found.
+        for chain in &self.chains {
+            // If we find the element in the chain, restore the entire chain up to and including
+            // the element
+            if let Some(index) = chain
+                .iter()
+                .position(|b| b.start_time.trunc_subsecs(0) == start_time)
+            {
+                let contributions =
+                    Delta::contributions(chain.iter().take(index + 1).map(|b| &b.delta).rev());
+
+                let tar_gz = OpenOptions::new()
+                    .write(true)
+                    .create(true)
+                    .open(output_path.as_ref())?;
+                let enc = GzEncoder::new(tar_gz, Compression::default());
+                let mut ar = tar::Builder::new(enc);
+
+                for (contribution, backup) in
+                    contributions.iter().rev().zip(chain.iter().take(index + 1))
+                {
+                    backup.append(&self.backup_dir, contribution, &mut ar)?;
+                }
+
+                let mut enc = ar.into_inner()?;
+                enc.try_finish()?;
+                enc.finish()?;
+
+                return Ok(());
+            }
+        }
+
+        Err(other("Unknown backup."))
+    }
+
     /// Get a reference to the underlying chains
     pub fn chains(&self) -> &Vec<Vec<Backup<T>>> {
         &self.chains

src/backup/mod.rs

@@ -244,6 +244,31 @@ impl<T: Clone> Backup<T> {
         let enc = GzDecoder::new(tar_gz);
         Ok(tar::Archive::new(enc))
     }
+
+    /// Open this backup's archive and append all its files that are part of the provided state to
+    /// the archive file.
+    pub fn append<P: AsRef<Path>>(
+        &self,
+        backup_dir: P,
+        state: &State,
+        ar: &mut tar::Builder<GzEncoder<File>>,
+    ) -> io::Result<()> {
+        let mut own_ar = self.open(backup_dir)?;
+        // println!("{:?}", &state);
+
+        for entry in own_ar.entries()? {
+            let entry = entry?;
+            let entry_path_in_tar = entry.path()?.to_path_buf();
+
+            if state.contains(&entry_path_in_tar) {
+                println!("{:?}", &entry_path_in_tar);
+                let header = entry.header().clone();
+                ar.append(&header, entry)?;
+            }
+        }
+
+        Ok(())
+    }
 }
 
 impl<T: Clone> fmt::Display for Backup<T> {

src/backup/state.rs

@@ -3,7 +3,7 @@ use serde::{Deserialize, Serialize};
 use std::borrow::Borrow;
 use std::collections::{HashMap, HashSet};
 use std::ops::{Deref, DerefMut};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 /// Struct that represents a current state for a backup. This struct acts as a smart pointer around
 /// a HashMap.
@@ -32,6 +32,15 @@ impl State {
             }
         }
     }
+
+    /// Returns whether the provided relative path is part of the given state.
+    pub fn contains<P: AsRef<Path>>(&self, path: P) -> bool {
+        let path = path.as_ref();
+
+        self.0.iter().any(|(dir, files)| {
+            path.starts_with(dir) && files.contains(path.strip_prefix(dir).unwrap())
+        })
+    }
 }
 
 impl<T> From<T> for State

src/cli/backup.rs

@@ -14,6 +14,8 @@ pub enum BackupCommands {
     Create(BackupCreateArgs),
     /// Restore a backup
     Restore(BackupRestoreArgs),
+    /// Export a backup into a full archive
+    Export(BackupExportArgs),
 }
 
 #[derive(Args)]
@@ -36,13 +38,13 @@ pub struct BackupListArgs {
 
 #[derive(Args)]
 pub struct BackupRestoreArgs {
-    /// Path to the backup inside the backup directory
+    /// Path to the backup inside the backup directory to restore
     path: PathBuf,
     /// Directory to store config in
     output_config: PathBuf,
     /// Directory to store worlds in
     output_worlds: PathBuf,
-    /// Whether to overwrite the contents of the existing directories
+    /// Whether to overwrite the contents of the output directories
     #[arg(short, long, default_value_t = false)]
     force: bool,
     /// Create output directories if they don't exist
@@ -50,12 +52,24 @@ pub struct BackupRestoreArgs {
     make: bool,
 }
 
+#[derive(Args)]
+pub struct BackupExportArgs {
+    /// Path to the backup inside the backup directory to export
+    path: PathBuf,
+    /// Path to store the exported archive
+    output: PathBuf,
+    /// Create output directories if they don't exist
+    #[arg(short, long, default_value_t = false)]
+    make: bool,
+}
+
 impl BackupArgs {
     pub fn run(&self, cli: &Cli) -> io::Result<()> {
         match &self.command {
             BackupCommands::Create(args) => args.run(cli),
             BackupCommands::List(args) => args.run(cli),
             BackupCommands::Restore(args) => args.run(cli),
+            BackupCommands::Export(args) => args.run(cli),
         }
     }
 }
@@ -171,3 +185,48 @@ impl BackupListArgs {
         Ok(())
     }
 }
+
+impl BackupExportArgs {
+    pub fn run(&self, cli: &Cli) -> io::Result<()> {
+        let backup_dir = cli.backup.canonicalize()?;
+
+        if self.make {
+            if let Some(parent) = &self.output.parent() {
+                std::fs::create_dir_all(parent)?;
+            }
+        }
+
+        // Parse input path
+        let path = self.path.canonicalize()?;
+
+        if !path.starts_with(&backup_dir) {
+            return Err(other("Provided file is not inside the backup directory."));
+        }
+
+        let layer = if let Some(parent) = path.parent() {
+            // Backup files should be stored nested inside a layer's folder
+            if parent != backup_dir {
+                parent.file_name().unwrap().to_string_lossy()
+            } else {
+                return Err(other("Invalid path."));
+            }
+        } else {
+            return Err(other("Invalid path."));
+        };
+
+        let timestamp = if let Some(filename) = path.file_name() {
+            Utc.datetime_from_str(&filename.to_string_lossy(), Backup::FILENAME_FORMAT)
+                .map_err(|_| other("Invalid filename."))?
+        } else {
+            return Err(other("Invalid filename."));
+        };
+
+        let meta = cli.meta()?;
+
+        if let Some(res) = meta.export_backup(&layer, timestamp, &self.output) {
+            res
+        } else {
+            Err(other("Unknown layer"))
+        }
+    }
+}