Committing all the libgit2 progress before throwing it away

I don't think libgit2 is the way forward to make any of this work.
There's so much work involved in parsing the git k-v store, and the
library itself is essentially of zero help for most of the heavy
lifting.

4 files changed, 229 insertions, 0 deletions

diff --git a/src/git/log.rs b/src/git/log.rs
new file mode 100644
index 0000000..dab9e69
--- /dev/null
+++ b/src/git/log.rs
@@ -0,0 +1,61 @@
+//! libgit2 log parsing
+
+use crate::git::{self, tree::FileNode};
+use git2::{Oid, Repository};
+use std::collections::{BTreeMap, BTreeSet};
+
+/// A file-commit referenced graph thing
+///
+/// git is _weird_!  It's essentially just a glorified key-value store
+/// and it shows.  There's no utilities to figure out how thing are
+/// related, and all the actual graph things in git are sugar on top
+/// of this store.
+///
+/// In order to make sense of anything in a repo we need to quite
+/// heavily parse the log.  This type here is the result of this
+/// parsing: you can ask it smart questions like "when did this file
+/// change" and it will tell you (sort of).
+#[derive(Default)]
+pub(crate) struct CommitGraph {
+    order: Vec<String>,
+    file_refs: BTreeMap<String, BTreeSet<String>>,
+    commit_refs: BTreeMap<String, CommitNode>,
+}
+
+pub(crate) struct CommitNode {
+    id: String,
+    author: String,
+    touches: BTreeSet<String>,
+    date: String,
+}
+
+fn build_diff_log(repo: &Repository, log: Vec<(String, Vec<FileNode>)>) -> Vec<CommitNode> {
+    todo!()
+}
+
+/// Walk through all commits from a given ref and build a commit graph
+pub(crate) fn create_commit_log(id: String, repo: &Repository) -> CommitGraph {
+    let mut walker = repo.revwalk().unwrap();
+    walker.push(Oid::from_str(id.as_str()).unwrap()).unwrap();
+    let mut v = walker
+        .into_iter()
+        .map(|oid| {
+            let oid = oid.unwrap();
+            repo.find_commit(oid).unwrap()
+        })
+        .collect::<Vec<_>>();
+    v.reverse();
+
+    let log: Vec<_> = v
+        .into_iter()
+        .map(|commit| {
+            let id = format!("{}", commit.id());
+            let tree_u = git::repo::get_tree(&repo, id.as_str());
+            let tree = git::tree::parse_tree(tree_u, &repo);
+            (id, tree.flatten())
+        })
+        .collect();
+
+    let diffs = build_diff_log(&repo, log);
+    todo!()
+}
diff --git a/src/git/mod.rs b/src/git/mod.rs
new file mode 100644
index 0000000..1cd9057
--- /dev/null
+++ b/src/git/mod.rs
@@ -0,0 +1,5 @@
+//! Wrappers for libgit2
+
+pub mod log;
+pub mod repo;
+pub mod tree;
diff --git a/src/git/repo.rs b/src/git/repo.rs
new file mode 100644
index 0000000..0d04b0d
--- /dev/null
+++ b/src/git/repo.rs
@@ -0,0 +1,19 @@
+use crate::templ_data::repo::RepoData;
+use git2::{Oid, Repository, Tree};
+
+/// Represents a repo in libgit2
+pub(crate) struct Repo {
+    pub(crate) inner: Repository,
+}
+
+impl Repo {
+    pub(crate) fn new(path: &str) -> Self {
+        Self {
+            inner: Repository::open(path).expect(&format!("`{}` is not a valid git repo", path)),
+        }
+    }
+}
+
+pub(crate) fn get_tree<'r>(repo: &'r Repository, rev: &str) -> Tree<'r> {
+    repo.revparse_single(rev).unwrap().peel_to_tree().unwrap()
+}
diff --git a/src/git/tree.rs b/src/git/tree.rs
new file mode 100644
index 0000000..457eb40
--- /dev/null
+++ b/src/git/tree.rs
@@ -0,0 +1,144 @@
+//! Tree handling utilities
+//!
+//! The way that libgit2 handles trees is super low-level and overkill
+//! for what we need.  In this module we knock it down a notch or two.
+//!
+//! This code takes a tree returned by
+//! `crate::git::repo::Repo::get_tree()`, and transforms it into a
+//! `TreeData` type that the template engine can render.
+
+use crate::templ_data::repo::{CommitData, FileData, TreeData};
+use git2::{self, ObjectType, TreeWalkMode};
+use std::collections::BTreeMap;
+
+/// A cache of a repository tree
+#[derive(Default, Debug, Clone)]
+pub(crate) struct Tree {
+    inner: BTreeMap<String, TreeNode>,
+}
+
+impl Tree {
+    /// Insert a node into a subtree with it's full path
+    fn insert_to_subtree(&mut self, mut path: Vec<String>, name: String, node: TreeNode) {
+        // If we are given a path, resolve it first
+        let curr = if path.len() > 0 {
+            let rest = path.split_off(1);
+            let mut curr = self.inner.get_mut(&path[0]).unwrap();
+
+            for dir in rest {
+                match curr {
+                    TreeNode::Dir(ref mut d) => {
+                        curr = d.children.inner.get_mut(&dir).unwrap();
+                    }
+                    _ => panic!("Not a tree!"),
+                }
+            }
+
+            match curr {
+                TreeNode::Dir(ref mut d) => &mut d.children,
+                TreeNode::File(_) => panic!("Not a tree!"),
+            }
+        } else {
+            // If no path was given, we assume the root is meant
+            self
+        };
+
+        curr.inner.insert(name, node);
+    }
+
+    /// Walk through the tree and only return filenode objects
+    pub(crate) fn flatten(&self) -> Vec<FileNode> {
+        self.inner.values().fold(vec![], |mut vec, node| {
+            match node {
+                TreeNode::File(f) => vec.push(f.clone()),
+                TreeNode::Dir(d) => vec.append(&mut d.children.flatten()),
+            }
+
+            vec
+        })
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum TreeNode {
+    File(FileNode),
+    Dir(DirNode),
+}
+
+impl TreeNode {
+    fn name(&self) -> String {
+        match self {
+            Self::File(f) => f.name.clone(),
+            Self::Dir(d) => d.name.clone(),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct FileNode {
+    pub id: String,
+    pub path: Vec<String>,
+    pub name: String,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct DirNode {
+    pub path: Vec<String>,
+    pub name: String,
+    pub children: Tree,
+}
+
+impl DirNode {
+    fn append(&mut self, node: TreeNode) {
+        self.children.inner.insert(node.name(), node);
+    }
+}
+
+/// Take a series of path-segments and render a tree at that location
+pub(crate) fn parse_tree(tree: git2::Tree, repo: &git2::Repository) -> Tree {
+    let mut root = Tree::default();
+
+    tree.walk(TreeWalkMode::PreOrder, |path, entry| {
+        let path: Vec<String> = path
+            .split("/")
+            .filter_map(|seg| match seg {
+                "" => None,
+                val => Some(val.into()),
+            })
+            .collect();
+        let name = entry.name().unwrap().to_string();
+
+        match entry.kind() {
+            // For every tree in the tree we create a new TreeNode with the path we know about
+            Some(ObjectType::Tree) => {
+                root.insert_to_subtree(
+                    path.clone(),
+                    name.clone(),
+                    TreeNode::Dir(DirNode {
+                        path,
+                        name,
+                        children: Tree::default(),
+                    }),
+                );
+            }
+            // If we encounter a blob, this is a file that we can simply insert into the tree
+            Some(ObjectType::Blob) => {
+                root.insert_to_subtree(
+                    path.clone(),
+                    name.clone(),
+                    TreeNode::File(FileNode {
+                        id: format!("{}", entry.id()),
+                        path,
+                        name,
+                    }),
+                );
+            }
+            _ => {}
+        }
+
+        0
+    })
+    .unwrap();
+
+    root
+}