From 35efa2a9c96f6f6660e8f1ed5b964141ced9995b Mon Sep 17 00:00:00 2001
From: Runxi Yu <me@runxiyu.org>
Date: Wed, 02 Apr 2025 03:06:54 +0800
Subject: [PATCH] LMTP: Stub patch application

---
 .golangci.yaml       |  2 ++
 go.mod               |  1 +
 go.sum               |  2 ++
 lmtp_handle_patch.go | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 lmtp_server.go       |  3 ++-

diff --git a/.golangci.yaml b/.golangci.yaml
index 00ba1ea7cafe82c9c91607f24365b136daf1c5b7..7edd4c30bd1dba973d6558c92cee7b8803dca30e 100644
--- a/.golangci.yaml
+++ b/.golangci.yaml
@@ -16,6 +16,8 @@     - nonamedreturns   # i like named returns
     - wrapcheck        # wrapping all errors is just not necessary
     - varnamelen       # "from" and "to" are very valid
     - stylecheck
+    - containedctx
+    - godot
     - maintidx    # e
     - nestif      # e
     - gocognit    # e
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..4e49d555d62e467e6b4ea404ffbe0a330fbd756f 100644
--- a/lmtp_handle_patch.go
+++ b/lmtp_handle_patch.go
@@ -4,12 +4,85 @@
 package main
 
 import (
-	"log/slog"
+	"bytes"
+	// "crypto/rand"
+	// "fmt"
+	"os"
+	"os/exec"
 
+	"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/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
+	var fsPath string
+	repo, _, _, fsPath, 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
+	}
+
+	// TODO: Try to not shell out
+
+	for _, diffFile := range diffFiles {
+		var sourceFile *object.File
+		if sourceFile, err = headTree.File(diffFile.OldName); err != nil {
+			return err
+		}
+		var sourceString string
+		if sourceString, err = sourceFile.Contents(); err != nil {
+			return err
+		}
+		hashBuf := bytes.Buffer{}
+		patchedBuf := bytes.Buffer{}
+		sourceBuf := bytes.NewReader(stringToBytes(sourceString))
+		if err = gitdiff.Apply(&patchedBuf, sourceBuf, diffFile); err != nil {
+			return err
+		}
+		proc := exec.CommandContext(session.ctx, "git", "hash-object", "w", "-t", "blob", "--stdin")
+		proc.Env = append(os.Environ(), "GIT_DIR="+fsPath)
+		proc.Stdout = &hashBuf
+		proc.Stdin = &patchedBuf
+		if err = proc.Start(); err != nil {
+			return err
+		}
+		newHash := hashBuf.Bytes()
+		if len(newHash) != 20*2+1 { // TODO: Hardcoded from the size of plumbing.Hash
+			panic("unexpected hash size")
+		}
+		// TODO: Add to tree
+	}
+
+	// contribBranchName := rand.Text()
+
+	// TODO: Store the branch
+
+	// fmt.Println(repo, diffFiles, preamble)
+	_ = 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