Optimize the Store::entries() interface

The previous iterator was implemented to simply fetch _all_ pathes from
the filesystem, no matter what.

With this implementation, this changes. The iterator now has
functionality to optimize the iteration, if only a subdirectory of the
store is required, for example `$STORE/foo`.

This is done via functionality where the underlying iterator gets
altered.

First of all, the interface was changed to return a `Entries` object,
which itself only covers the libimagstore-internal `PathIterator` type.
This type was changed so that the backend implementation provides an
"PathIterBuilder`, which builds the actual iterator object for the
`PathIterator` type.

The intermediate `StoreIdConstructingIterator` was merged into
`PathIterator` for simplicity.

The `Entries` type got functionality similar to the
`StoreIdIteratorWithStore` type for easier transition to the new API.
This should probably be removed at a later point, though.

As the `walkdir::WalkDir` type is not as nice as it could be, iterators
for two collections in the store could be built like this (untested):

    store
        .entries()?
        .in_collection("foo")
        .chain(store.entries()?.in_collection("bar"))

Functionality to exclude subdirectories is not possible with the current
`walkdir::WalkDir` implementation and has to be done during iteration,
with filtering (as usual).

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

lib/core/libimagstore/src/file_abstraction/fs.rs

@@ -20,6 +20,7 @@
 use std::fs::{File, OpenOptions, create_dir_all, remove_file, copy, rename};
 use std::io::{Seek, SeekFrom, Read};
 use std::path::{Path, PathBuf};
+use std::sync::Arc;
 
 use error::{StoreError as SE, StoreErrorKind as SEK};
 use error::ResultExt;
@@ -30,6 +31,9 @@ use super::Drain;
 use store::Entry;
 use storeid::StoreId;
 use file_abstraction::iter::PathIterator;
+use file_abstraction::iter::PathIterBuilder;
+
+use walkdir::WalkDir;
 
 #[derive(Debug)]
 pub struct FSFileAbstractionInstance(PathBuf);
@@ -133,18 +137,34 @@ impl FileAbstraction for FSFileAbstraction {
             })
     }
 
-    fn pathes_recursively(&self, basepath: PathBuf) -> Result<PathIterator, SE> {
-        use walkdir::WalkDir;
+    fn pathes_recursively(&self,
+                          basepath: PathBuf,
+                          storepath: PathBuf,
+                          backend: Arc<FileAbstraction>)
+        -> Result<PathIterator, SE>
+    {
+        trace!("Building PathIterator object");
+        Ok(PathIterator::new(Box::new(WalkDirPathIterBuilder { basepath }), storepath, backend))
+    }
+}
 
-        let i = WalkDir::new(basepath)
+pub(crate) struct WalkDirPathIterBuilder {
+    basepath: PathBuf
+}
+
+impl PathIterBuilder for WalkDirPathIterBuilder {
+    fn build_iter(&self) -> Box<Iterator<Item = Result<PathBuf, SE>>> {
+        Box::new(WalkDir::new(self.basepath.clone())
             .min_depth(1)
             .max_open(100)
             .into_iter()
             .map(|r| {
                 r.map(|e| PathBuf::from(e.path())).chain_err(|| SE::from_kind(SEK::FileError))
-            });
+            }))
+    }
 
-        Ok(PathIterator::new(Box::new(i)))
+    fn in_collection(&mut self, c: &str) {
+        self.basepath.push(c);
     }
 }
 

lib/core/libimagstore/src/file_abstraction/inmemory.rs

@@ -33,6 +33,7 @@ use super::Drain;
 use store::Entry;
 use storeid::StoreId;
 use file_abstraction::iter::PathIterator;
+use file_abstraction::iter::PathIterBuilder;
 
 type Backend = Arc<Mutex<RefCell<HashMap<PathBuf, Entry>>>>;
 
@@ -181,9 +182,9 @@ impl FileAbstraction for InMemoryFileAbstraction {
         Ok(())
     }
 
-    fn pathes_recursively(&self, _basepath: PathBuf) -> Result<PathIterator, SE> {
-        debug!("Getting all pathes");
-        let keys : Vec<Result<PathBuf, SE>> = self
+    fn pathes_recursively(&self, _basepath: PathBuf, storepath: PathBuf, backend: Arc<FileAbstraction>) -> Result<PathIterator, SE> {
+        trace!("Building PathIterator object (inmemory implementation)");
+        let keys : Vec<PathBuf> = self
             .backend()
             .lock()
             .map_err(|_| SE::from_kind(SEK::FileError))?
@@ -191,9 +192,21 @@ impl FileAbstraction for InMemoryFileAbstraction {
             .keys()
             .map(PathBuf::from)
             .map(Ok)
-            .collect(); // we have to collect() because of the lock() above.
+            .collect::<Result<_, SE>>()?; // we have to collect() because of the lock() above.
 
-        Ok(PathIterator::new(Box::new(keys.into_iter())))
+        Ok(PathIterator::new(Box::new(InMemPathIterBuilder(keys)), storepath, backend))
+    }
+}
+
+pub(crate) struct InMemPathIterBuilder(Vec<PathBuf>);
+
+impl PathIterBuilder for InMemPathIterBuilder {
+    fn build_iter(&self) -> Box<Iterator<Item = Result<PathBuf, SE>>> {
+        Box::new(self.0.clone().into_iter().map(Ok))
+    }
+
+    fn in_collection(&mut self, c: &str) {
+        self.0.retain(|p| p.starts_with(c));
     }
 }
 

lib/core/libimagstore/src/file_abstraction/iter.rs

@@ -24,48 +24,63 @@ use error::Result;
 use storeid::StoreId;
 use file_abstraction::FileAbstraction;
 
+/// See documentation for PathIterator
+pub trait PathIterBuilder {
+    fn build_iter(&self) -> Box<Iterator<Item = Result<PathBuf>>>;
+    fn in_collection(&mut self, c: &str);
+}
+
 /// A wrapper for an iterator over `PathBuf`s
-pub struct PathIterator(Box<Iterator<Item = Result<PathBuf>>>);
+///
+/// As the backend defines how "iterating over all entries" is implemented, this type holds a
+/// `PathIterBuilder` internally. This type is used to create new iterator instances every time the
+/// "settings" for how the iterator behaves are changed. This basically means: If the PathIterator
+/// is requested to not iterate over a directory "a" but rather its subdirectory "a/b", the
+/// implementation asks the `PathIterBuilder` to create a new iterator for that.
+///
+/// The `PathIterBuilder` can then yield a new iterator instance which is optimized for the new
+/// requirements (which basically means: Construct a new WalkDir object which does traverse the
+/// subdirectory instead of the parent).
+///
+/// This means quite a few allocations down the road, as the PathIterator itself is not generic, but
+/// this seems to be the best way to implement this.
+pub struct PathIterator {
+    iter_builder: Box<PathIterBuilder>,
+    iter:         Box<Iterator<Item = Result<PathBuf>>>,
+    storepath:    PathBuf,
+    backend:      Arc<FileAbstraction>,
+}
 
 impl PathIterator {
 
-    pub fn new(iter: Box<Iterator<Item = Result<PathBuf>>>) -> PathIterator {
-        PathIterator(iter)
+    pub fn new(iter_builder: Box<PathIterBuilder>,
+               storepath: PathBuf,
+               backend: Arc<FileAbstraction>)
+        -> PathIterator
+    {
+        trace!("Generating iterator object with PathIterBuilder");
+        let iter = iter_builder.build_iter();
+        PathIterator { iter_builder, iter, storepath, backend }
     }
 
-    pub fn store_id_constructing(self, storepath: PathBuf, backend: Arc<FileAbstraction>)
-        -> StoreIdConstructingIterator
-    {
-        StoreIdConstructingIterator(self, storepath, backend)
+    pub fn in_collection(mut self, c: &str) -> Self {
+        trace!("Generating iterator object for collection: {}", c);
+        self.iter_builder.in_collection(c);
+        self
     }
 
 }
 
 impl Iterator for PathIterator {
-    type Item = Result<PathBuf>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.0.next()
-    }
-
-}
-
-
-/// Helper type for constructing StoreIds from a PathIterator.
-///
-/// Automatically ignores non-files.
-pub struct StoreIdConstructingIterator(PathIterator, PathBuf, Arc<FileAbstraction>);
-
-impl Iterator for StoreIdConstructingIterator {
     type Item = Result<StoreId>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        while let Some(next) = self.0.next() {
+        while let Some(next) = self.iter.next() {
             match next {
                 Err(e)   => return Some(Err(e)),
-                Ok(next) => match self.2.is_file(&next) {
+                Ok(next) => match self.backend.is_file(&next) {
                     Err(e)    => return Some(Err(e)),
-                    Ok(true)  => return Some(StoreId::from_full_path(&self.1, next)),
+                    Ok(true)  => return Some(StoreId::from_full_path(&self.storepath, next)),
                     Ok(false) => { continue },
                 }
             }

lib/core/libimagstore/src/file_abstraction/mod.rs

@@ -20,6 +20,7 @@
 use std::path::PathBuf;
 use std::fmt::Debug;
 use std::collections::HashMap;
+use std::sync::Arc;
 
 use error::StoreError as SE;
 use store::Entry;
@@ -50,7 +51,7 @@ pub trait FileAbstraction : Debug {
     fn drain(&self) -> Result<Drain, SE>;
     fn fill<'a>(&'a mut self, d: Drain) -> Result<(), SE>;
 
-    fn pathes_recursively(&self, basepath: PathBuf) -> Result<PathIterator, SE>;
+    fn pathes_recursively(&self, basepath: PathBuf, storepath: PathBuf, backend: Arc<FileAbstraction>) -> Result<PathIterator, SE>;
 }
 
 /// An abstraction trait over actions on files

lib/core/libimagstore/src/iter.rs

@@ -144,3 +144,81 @@ mod compile_test {
     }
 }
 
+use storeid::StoreId;
+use storeid::StoreIdIterator;
+use self::delete::StoreDeleteIterator;
+use self::get::StoreGetIterator;
+use self::retrieve::StoreRetrieveIterator;
+use file_abstraction::iter::PathIterator;
+use store::Store;
+use error::StoreError;
+use error::Result;
+
+/// Iterator for iterating over all (or a subset of all) entries
+///
+/// The iterator now has functionality to optimize the iteration, if only a subdirectory of the
+/// store is required, for example `$STORE/foo`.
+///
+/// This is done via functionality where the underlying iterator gets
+/// altered.
+///
+/// As the (for the filesystem backend underlying) `walkdir::WalkDir` type is not as nice as it
+/// could be, iterating over two subdirectories with one iterator is not possible. Thus, iterators
+/// for two collections in the store should be build like this (untested):
+///
+/// ```ignore
+///     store
+///         .entries()?
+///         .in_collection("foo")
+///         .chain(store.entries()?.in_collection("bar"))
+/// ```
+///
+/// Functionality to exclude subdirectories is not possible with the current implementation and has
+/// to be done during iteration, with filtering (as usual).
+pub struct Entries<'a>(PathIterator, &'a Store);
+
+impl<'a> Entries<'a> {
+
+    pub(crate) fn new(pi: PathIterator, store: &'a Store) -> Self {
+        Entries(pi, store)
+    }
+
+    pub fn in_collection(self, c: &str) -> Self {
+        Entries(self.0.in_collection(c), self.1)
+    }
+
+    pub fn without_store(self) -> StoreIdIterator {
+        StoreIdIterator::new(Box::new(self.0))
+    }
+
+    /// Transform the iterator into a StoreDeleteIterator
+    ///
+    /// This immitates the API from `libimagstore::iter`.
+    pub fn into_delete_iter(self) -> StoreDeleteIterator<'a, StoreError> {
+        StoreDeleteIterator::new(Box::new(self.0), self.1)
+    }
+
+    /// Transform the iterator into a StoreGetIterator
+    ///
+    /// This immitates the API from `libimagstore::iter`.
+    pub fn into_get_iter(self) -> StoreGetIterator<'a, StoreError> {
+        StoreGetIterator::new(Box::new(self.0), self.1)
+    }
+
+    /// Transform the iterator into a StoreRetrieveIterator
+    ///
+    /// This immitates the API from `libimagstore::iter`.
+    pub fn into_retrieve_iter(self) -> StoreRetrieveIterator<'a, StoreError> {
+        StoreRetrieveIterator::new(Box::new(self.0), self.1)
+    }
+
+}
+
+impl<'a> Iterator for Entries<'a> {
+    type Item = Result<StoreId>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+

lib/core/libimagstore/src/store.rs

@@ -37,7 +37,8 @@ use toml_query::read::TomlValueReadTypeExt;
 
 use error::{StoreError as SE, StoreErrorKind as SEK};
 use error::ResultExt;
-use storeid::{IntoStoreId, StoreId, StoreIdIteratorWithStore};
+use storeid::{IntoStoreId, StoreId};
+use iter::Entries;
 use file_abstraction::FileAbstractionInstance;
 
 // We re-export the following things so tests can use them
@@ -642,12 +643,11 @@ impl Store {
     }
 
     /// Get _all_ entries in the store (by id as iterator)
-    pub fn entries(&self) -> Result<StoreIdIteratorWithStore> {
+    pub fn entries<'a>(&'a self) -> Result<Entries<'a>> {
+        trace!("Building 'Entries' iterator");
         self.backend
-            .pathes_recursively(self.path().clone())
-            .map(|i| i.store_id_constructing(self.path().clone(), self.backend.clone()))
-            .map(Box::new)
-            .map(|it| StoreIdIteratorWithStore::new(it, self))
+            .pathes_recursively(self.path().clone(), self.path().clone(), self.backend.clone())
+            .map(|i| Entries::new(i, self))
     }
 
     /// Gets the path where this store is on the disk

lib/domain/libimaghabit/src/store.rs

@@ -48,11 +48,11 @@ pub trait HabitStore {
 impl HabitStore for Store {
     /// Get an iterator over all habits
     fn all_habit_templates(&self) -> Result<HabitTemplateStoreIdIterator> {
-        self.entries().map(HabitTemplateStoreIdIterator::from).map_err(From::from)
+        Ok(HabitTemplateStoreIdIterator::from(self.entries()?.without_store()))
     }
 
     fn all_habit_instances(&self) -> Result<HabitInstanceStoreIdIterator> {
-        self.entries().map(HabitInstanceStoreIdIterator::from).map_err(From::from)
+        Ok(HabitInstanceStoreIdIterator::from(self.entries()?.without_store()))
     }
 }
 

lib/domain/libimagtimetrack/src/iter/get.rs

@@ -17,18 +17,18 @@
 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 //
 
-use libimagstore::storeid::StoreIdIteratorWithStore;
+use libimagstore::iter::Entries;
 use libimagstore::store::Store;
 use libimagstore::store::Result as StoreResult;
 use libimagstore::store::FileLockEntry;
 
 use constants::*;
 
-pub struct TimeTrackingsGetIterator<'a>(StoreIdIteratorWithStore<'a>, &'a Store);
+pub struct TimeTrackingsGetIterator<'a>(Entries<'a>, &'a Store);
 
 impl<'a> TimeTrackingsGetIterator<'a> {
-    pub fn new(sit: StoreIdIteratorWithStore<'a>, store: &'a Store) -> Self {
-        TimeTrackingsGetIterator(sit, store)
+    pub fn new(entries: Entries<'a>, store: &'a Store) -> Self {
+        TimeTrackingsGetIterator(entries, store)
     }
 }
 

lib/domain/libimagwiki/src/wiki.rs

@@ -95,7 +95,7 @@ impl<'a, 'b> Wiki<'a, 'b> {
 
     pub fn all_ids(&self) -> Result<WikiIdIterator> {
         let filter = IdIsInWikiFilter(self.1);
-        Ok(WikiIdIterator(self.0.entries()?, filter))
+        Ok(WikiIdIterator(self.0.entries()?.without_store().with_store(self.0), filter))
     }
 
     pub fn delete_entry<EN: AsRef<str>>(&self, entry_name: EN) -> Result<()> {