This is it

Squashed commit of all the exploration history. Development starts here.

Signed-off-by: Kim Altintop <kim@eagain.io>

1 files changed, 165 insertions, 0 deletions

diff --git a/src/patches/traits.rs b/src/patches/traits.rs
new file mode 100644
index 0000000..ef9ae61
--- /dev/null
+++ b/src/patches/traits.rs
@@ -0,0 +1,165 @@
+// Copyright © 2022 Kim Altintop <kim@eagain.io>
+// SPDX-License-Identifier: GPL-2.0-only WITH openvpn-openssl-exception
+
+use std::{
+    io,
+    path::{
+        Path,
+        PathBuf,
+    },
+};
+
+use super::error;
+use crate::git::{
+    self,
+    if_not_found_none,
+};
+
+pub trait BlobData: Sized {
+    type Error;
+
+    const MAX_BYTES: usize;
+
+    fn from_blob(data: &[u8]) -> Result<Self, Self::Error>;
+    fn write_blob<W: io::Write>(&self, writer: W) -> io::Result<()>;
+}
+
+pub trait TreeData: BlobData {
+    const BLOB_NAME: &'static str;
+}
+
+pub struct Blob<T> {
+    pub oid: git2::Oid,
+    pub content: T,
+}
+
+impl<T> Blob<T>
+where
+    T: TreeData,
+    T::Error: Into<crate::Error>,
+{
+    pub fn from_tree<'a>(
+        repo: &'a git2::Repository,
+        tree: &git2::Tree<'a>,
+    ) -> Result<Blob<T>, error::FromTree> {
+        use error::FromTree::NotFound;
+
+        let entry = tree
+            .get_name(T::BLOB_NAME)
+            .ok_or(NotFound { name: T::BLOB_NAME })?;
+        Self::from_entry(repo, entry)
+    }
+
+    pub fn from_entry<'a>(
+        repo: &'a git2::Repository,
+        entry: git2::TreeEntry<'a>,
+    ) -> Result<Self, error::FromTree> {
+        use error::FromTree::{
+            BlobSize,
+            TypeConversion,
+            TypeMismatch,
+        };
+
+        let blob = entry
+            .to_object(repo)?
+            .into_blob()
+            .map_err(|obj| TypeMismatch {
+                name: T::BLOB_NAME,
+                kind: obj.kind(),
+            })?;
+        let sz = blob.size();
+        if sz > T::MAX_BYTES {
+            return Err(BlobSize {
+                max: T::MAX_BYTES,
+                found: sz,
+            });
+        }
+        let content = T::from_blob(blob.content())
+            .map_err(Into::into)
+            .map_err(TypeConversion)?;
+
+        Ok(Self {
+            oid: entry.id(),
+            content,
+        })
+    }
+}
+
+pub trait Foldable {
+    fn folded_name(&self) -> String;
+}
+
+pub trait Seen {
+    fn in_odb(&self, odb: &git2::Odb) -> git::Result<bool>;
+    fn in_tree(&self, tree: &git2::Tree) -> git::Result<bool>;
+}
+
+impl<T> Seen for T
+where
+    T: BlobData + Foldable,
+{
+    fn in_odb(&self, odb: &git2::Odb) -> git::Result<bool> {
+        let hash = blob_hash(self)?;
+        Ok(odb.exists(hash))
+    }
+
+    fn in_tree(&self, tree: &git2::Tree) -> git::Result<bool> {
+        let path = shard_path(&self.folded_name());
+        Ok(if_not_found_none(tree.get_path(&path))?.is_some())
+    }
+}
+
+pub fn to_tree<T: TreeData>(
+    repo: &git2::Repository,
+    tree: &mut git2::TreeBuilder,
+    data: &T,
+) -> git::Result<()> {
+    tree.insert(
+        T::BLOB_NAME,
+        to_blob(repo, data)?,
+        git2::FileMode::Blob.into(),
+    )?;
+    Ok(())
+}
+
+pub fn to_blob<T: BlobData>(repo: &git2::Repository, data: &T) -> git::Result<git2::Oid> {
+    let mut writer = repo.blob_writer(None)?;
+    data.write_blob(&mut writer).map_err(|e| {
+        git2::Error::new(
+            git2::ErrorCode::GenericError,
+            git2::ErrorClass::Object,
+            e.to_string(),
+        )
+    })?;
+    writer.commit()
+}
+
+pub fn blob_hash<T: BlobData>(data: &T) -> git::Result<git2::Oid> {
+    let mut buf = Vec::new();
+    data.write_blob(&mut buf).unwrap();
+    git::blob_hash(&buf)
+}
+
+pub fn write_sharded<F: Foldable>(
+    repo: &git2::Repository,
+    root: &mut git2::TreeBuilder,
+    item: &F,
+    blob: git2::Oid,
+) -> git::Result<()> {
+    let name = item.folded_name();
+    let (pre, suf) = name.split_at(2);
+    let shard = root
+        .get(pre)?
+        .map(|entry| entry.to_object(repo))
+        .transpose()?;
+    let mut sub = repo.treebuilder(shard.as_ref().and_then(git2::Object::as_tree))?;
+    sub.insert(suf, blob, git2::FileMode::Blob.into())?;
+    root.insert(pre, sub.write()?, git2::FileMode::Tree.into())?;
+
+    Ok(())
+}
+
+pub fn shard_path(name: &str) -> PathBuf {
+    let (pre, suf) = name.split_at(2);
+    Path::new(pre).join(suf)
+}