1 files changed, 133 insertions, 0 deletions
diff --git a/internal/unsorted/lmtp_handle_patch.go b/internal/unsorted/lmtp_handle_patch.go
new file mode 100644
index 0000000..1a23422
--- /dev/null
+++ b/internal/unsorted/lmtp_handle_patch.go
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+package unsorted
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+
+	"github.com/bluekeyes/go-gitdiff/gitdiff"
+	"github.com/go-git/go-git/v5"
+	"go.lindenii.runxiyu.org/forge/internal/misc"
+)
+
+func (s *Server) lmtpHandlePatch(session *lmtpSession, groupPath []string, repoName string, mbox io.Reader) (err error) {
+	var diffFiles []*gitdiff.File
+	var preamble string
+	if diffFiles, preamble, err = gitdiff.Parse(mbox); err != nil {
+		return fmt.Errorf("failed to parse patch: %w", err)
+	}
+
+	var header *gitdiff.PatchHeader
+	if header, err = gitdiff.ParsePatchHeader(preamble); err != nil {
+		return fmt.Errorf("failed to parse patch headers: %w", err)
+	}
+
+	var repo *git.Repository
+	var fsPath string
+	repo, _, _, fsPath, err = s.openRepo(session.ctx, groupPath, repoName)
+	if err != nil {
+		return fmt.Errorf("failed to open repo: %w", err)
+	}
+
+	headRef, err := repo.Head()
+	if err != nil {
+		return fmt.Errorf("failed to get repo head hash: %w", err)
+	}
+	headCommit, err := repo.CommitObject(headRef.Hash())
+	if err != nil {
+		return fmt.Errorf("failed to get repo head commit: %w", err)
+	}
+	headTree, err := headCommit.Tree()
+	if err != nil {
+		return fmt.Errorf("failed to get repo head tree: %w", err)
+	}
+
+	headTreeHash := headTree.Hash.String()
+
+	blobUpdates := make(map[string][]byte)
+	for _, diffFile := range diffFiles {
+		sourceFile, err := headTree.File(diffFile.OldName)
+		if err != nil {
+			return fmt.Errorf("failed to get file at old name %#v: %w", diffFile.OldName, err)
+		}
+		sourceString, err := sourceFile.Contents()
+		if err != nil {
+			return fmt.Errorf("failed to get contents: %w", err)
+		}
+
+		sourceBuf := bytes.NewReader(misc.StringToBytes(sourceString))
+		var patchedBuf bytes.Buffer
+		if err := gitdiff.Apply(&patchedBuf, sourceBuf, diffFile); err != nil {
+			return fmt.Errorf("failed to apply patch: %w", err)
+		}
+
+		var hashBuf bytes.Buffer
+
+		// It's really difficult to do this via go-git so we're just
+		// going to use upstream git for now.
+		// TODO
+		cmd := exec.CommandContext(session.ctx, "git", "hash-object", "-w", "-t", "blob", "--stdin")
+		cmd.Env = append(os.Environ(), "GIT_DIR="+fsPath)
+		cmd.Stdout = &hashBuf
+		cmd.Stdin = &patchedBuf
+		if err := cmd.Run(); err != nil {
+			return fmt.Errorf("failed to run git hash-object: %w", err)
+		}
+
+		newHashStr := strings.TrimSpace(hashBuf.String())
+		newHash, err := hex.DecodeString(newHashStr)
+		if err != nil {
+			return fmt.Errorf("failed to decode hex string from git: %w", err)
+		}
+
+		blobUpdates[diffFile.NewName] = newHash
+		if diffFile.NewName != diffFile.OldName {
+			blobUpdates[diffFile.OldName] = nil // Mark for deletion.
+		}
+	}
+
+	newTreeSha, err := buildTreeRecursive(session.ctx, fsPath, headTreeHash, blobUpdates)
+	if err != nil {
+		return fmt.Errorf("failed to recursively build a tree: %w", err)
+	}
+
+	commitMsg := header.Title
+	if header.Body != "" {
+		commitMsg += "\n\n" + header.Body
+	}
+
+	env := append(os.Environ(),
+		"GIT_DIR="+fsPath,
+		"GIT_AUTHOR_NAME="+header.Author.Name,
+		"GIT_AUTHOR_EMAIL="+header.Author.Email,
+		"GIT_AUTHOR_DATE="+header.AuthorDate.Format(time.RFC3339),
+	)
+	commitCmd := exec.CommandContext(session.ctx, "git", "commit-tree", newTreeSha, "-p", headCommit.Hash.String(), "-m", commitMsg)
+	commitCmd.Env = env
+
+	var commitOut bytes.Buffer
+	commitCmd.Stdout = &commitOut
+	if err := commitCmd.Run(); err != nil {
+		return fmt.Errorf("failed to commit tree: %w", err)
+	}
+	newCommitSha := strings.TrimSpace(commitOut.String())
+
+	newBranchName := rand.Text()
+
+	refCmd := exec.CommandContext(session.ctx, "git", "update-ref", "refs/heads/contrib/"+newBranchName, newCommitSha) //#nosec G204
+	refCmd.Env = append(os.Environ(), "GIT_DIR="+fsPath)
+	if err := refCmd.Run(); err != nil {
+		return fmt.Errorf("failed to update ref: %w", err)
+	}
+
+	return nil
+}