From 821151baeceb598d0ffd650e3332d57b6c1af794 Mon Sep 17 00:00:00 2001
From: Runxi Yu <me@runxiyu.org>
Date: Wed, 02 Apr 2025 02:30:35 +0800
Subject: [PATCH] BROKEN

---
 go.mod               |  1 +
 go.sum               |  2 ++
 lmtp_handle_patch.go | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 lmtp_server.go       |  3 ++-

diff --git a/go.mod b/go.mod
index 6555e3b99749e3abd1cecea00c3a6275b59d4f3a..2ee258f25001a23f4d67598742b490de4f63663c 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@
 require (
 	github.com/alecthomas/chroma/v2 v2.15.0
 	github.com/alexedwards/argon2id v1.0.0
+	github.com/bluekeyes/go-gitdiff v0.8.1
 	github.com/dgraph-io/ristretto/v2 v2.1.0
 	github.com/dustin/go-humanize v1.0.1
 	github.com/gliderlabs/ssh v0.3.8
diff --git a/go.sum b/go.sum
index 70aa113c54c0f6a6727f003345ea7e5f1240359c..593a0f6acb84feb0d0c192169fc379c45bc2ac6a 100644
--- a/go.sum
+++ b/go.sum
@@ -19,6 +19,8 @@ github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5 h1:0CwZNZbxp69SHPdPJAN/hZIm0C4OItdklCFmMRWYpio=
 github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5/go.mod h1:wHh0iHkYZB8zMSxRWpUBQtwG5a7fFgvEO+odwuTv2gs=
 github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuPk=
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
+github.com/bluekeyes/go-gitdiff v0.8.1 h1:lL1GofKMywO17c0lgQmJYcKek5+s8X6tXVNOLxy4smI=
+github.com/bluekeyes/go-gitdiff v0.8.1/go.mod h1:WWAk1Mc6EgWarCrPFO+xeYlujPu98VuLW3Tu+B/85AE=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cloudflare/circl v1.6.0 h1:cr5JKic4HI+LkINy2lg3W2jF8sHCVTBncJr5gIIq7qk=
diff --git a/lmtp_handle_patch.go b/lmtp_handle_patch.go
index a3064d1a45bf6a482bdd268123f12ca6b6d7d2ac..ed47e25651dfc9541910b4efbd08897119f9e447 100644
--- a/lmtp_handle_patch.go
+++ b/lmtp_handle_patch.go
@@ -4,12 +4,88 @@
 package main
 
 import (
-	"log/slog"
+	"crypto/rand"
+	"fmt"
 
+	"github.com/bluekeyes/go-gitdiff/gitdiff"
 	"github.com/emersion/go-message"
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/config"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/object"
 )
 
-func lmtpHandlePatch(groupPath []string, repoName string, email *message.Entity) (err error) {
-	slog.Info("Pretend like I'm handling a patch!")
+func lmtpHandlePatch(session *lmtpSession, groupPath []string, repoName string, email *message.Entity) (err error) {
+	var diffFiles []*gitdiff.File
+	var preamble string
+	if diffFiles, preamble, err = gitdiff.Parse(email.Body); err != nil {
+		return
+	}
+
+	var repo *git.Repository
+	repo, _, _, err = openRepo(session.ctx, groupPath, repoName)
+	if err != nil {
+		return
+	}
+
+	var headRef *plumbing.Reference
+	if headRef, err = repo.Head(); err != nil {
+		return
+	}
+
+	var headCommit *object.Commit
+	if headCommit, err = repo.CommitObject(headRef.Hash()); err != nil {
+		return
+	}
+
+	var headTree *object.Tree
+	if headTree, err = headCommit.Tree(); err != nil {
+		return
+	}
+
+	// What's left to do: apply the patch on a separate branch.
+	// I'm not sure how to do this in go-git. I have a few thoughts:
+	// Method 1. Create a copy of the tree object; then iterate through
+	//           diffFiles, traversing the tree accordingly, then hash
+	//           blobs, insert them into the repo, replace the entry in
+	//           the tree, then commit the tree onto a new branch.
+	//           Perhaps storer can help with this?
+	// Method 2. Create an index, run the patch on it, and commit the
+	//           index.
+	// I think Method 1 technically suffers from a race if the repo is
+	// garbage collected between the time that the blob is created and
+	// the time it is committed to a branch. We could just prevent
+	// external GCs and lock GCs ourselves though, so it's no big deal.
+	// Method 2 is a bit annoying and I have this impression that
+	// worktrees/indexes are fragile and bloated.
+
+	myTree := *headTree
+	// TODO: Check if it's actually safe to modify myTree. We don't
+	// own these slices, so this might interfere with go-git's internal
+	// state.
+
+	for _, diffFile := range diffFiles {
+		blobObject := plumbing.EncodedObject
+		var blobHash plumbing.Hash
+		if blobHash, err = repo.Storer.SetEncodedObject(blobObject); err != nil {
+			return
+		}
+	}
+
+	/*
+		contribBranchName := rand.Text()
+
+		if err = repo.CreateBranch(&config.Branch{ Name: contribBranchName, }); err != nil {
+			return
+		}
+
+		var contribRef *plumbing.Reference
+		if contribRef, err = repo.Reference(plumbing.NewBranchReferenceName(contribBranchName, true); err != nil {
+			return
+		}
+	*/
+
+	fmt.Println(repo, diffFiles, preamble)
+
 	return nil
 }
diff --git a/lmtp_server.go b/lmtp_server.go
index 998b53c810fa0c5f30f9ccf46c0d189980576be3..44dc8d41db3ee1fa38a8520db2b25ae3c7a6cb7e 100644
--- a/lmtp_server.go
+++ b/lmtp_server.go
@@ -163,8 +163,9 @@ 		moduleType := segments[sepIndex+1]
 		moduleName := segments[sepIndex+2]
 		switch moduleType {
 		case "repos":
-			err = lmtpHandlePatch(groupPath, moduleName, email)
+			err = lmtpHandlePatch(session, groupPath, moduleName, email)
 			if err != nil {
+				slog.Error("error handling patch", "error", err)
 				goto end
 			}
 		default:

-- 
2.48.1