5 files changed, 281 insertions, 0 deletions
diff --git a/forged/internal/git2c/client.go b/forged/internal/git2c/client.go
new file mode 100644
index 0000000..ed9390c
--- /dev/null
+++ b/forged/internal/git2c/client.go
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+// Package git2c provides routines to interact with the git2d backend daemon.
+package git2c
+
+import (
+	"fmt"
+	"net"
+
+	"go.lindenii.runxiyu.org/forge/forged/internal/bare"
+)
+
+// Client represents a connection to the git2d backend daemon.
+type Client struct {
+	socketPath string
+	conn       net.Conn
+	writer     *bare.Writer
+	reader     *bare.Reader
+}
+
+// NewClient establishes a connection to a git2d socket and returns a new Client.
+func NewClient(socketPath string) (*Client, error) {
+	conn, err := net.Dial("unix", socketPath)
+	if err != nil {
+		return nil, fmt.Errorf("git2d connection failed: %w", err)
+	}
+
+	writer := bare.NewWriter(conn)
+	reader := bare.NewReader(conn)
+
+	return &Client{
+		socketPath: socketPath,
+		conn:       conn,
+		writer:     writer,
+		reader:     reader,
+	}, nil
+}
+
+// Close terminates the underlying socket connection.
+func (c *Client) Close() error {
+	if c.conn != nil {
+		return c.conn.Close()
+	}
+	return nil
+}
diff --git a/forged/internal/git2c/cmd_index.go b/forged/internal/git2c/cmd_index.go
new file mode 100644
index 0000000..8862b2c
--- /dev/null
+++ b/forged/internal/git2c/cmd_index.go
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+package git2c
+
+import (
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// CmdIndex requests a repository index from git2d and returns the list of commits
+// and the contents of a README file if available.
+func (c *Client) CmdIndex(repoPath string) ([]Commit, *FilenameContents, error) {
+	if err := c.writer.WriteData([]byte(repoPath)); err != nil {
+		return nil, nil, fmt.Errorf("sending repo path failed: %w", err)
+	}
+	if err := c.writer.WriteUint(1); err != nil {
+		return nil, nil, fmt.Errorf("sending command failed: %w", err)
+	}
+
+	status, err := c.reader.ReadUint()
+	if err != nil {
+		return nil, nil, fmt.Errorf("reading status failed: %w", err)
+	}
+	if status != 0 {
+		return nil, nil, fmt.Errorf("git2d error: %d", status)
+	}
+
+	// README
+	readmeRaw, err := c.reader.ReadData()
+	if err != nil {
+		readmeRaw = nil
+	}
+
+	readmeFilename := "README.md" // TODO
+	readme := &FilenameContents{Filename: readmeFilename, Content: readmeRaw}
+
+	// Commits
+	var commits []Commit
+	for {
+		id, err := c.reader.ReadData()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			}
+			return nil, nil, fmt.Errorf("reading commit ID failed: %w", err)
+		}
+		title, _ := c.reader.ReadData()
+		authorName, _ := c.reader.ReadData()
+		authorEmail, _ := c.reader.ReadData()
+		authorDate, _ := c.reader.ReadData()
+
+		commits = append(commits, Commit{
+			Hash:    hex.EncodeToString(id),
+			Author:  string(authorName),
+			Email:   string(authorEmail),
+			Date:    string(authorDate),
+			Message: string(title),
+		})
+	}
+
+	return commits, readme, nil
+}
diff --git a/forged/internal/git2c/cmd_treeraw.go b/forged/internal/git2c/cmd_treeraw.go
new file mode 100644
index 0000000..492cb84
--- /dev/null
+++ b/forged/internal/git2c/cmd_treeraw.go
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+package git2c
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+// CmdTreeRaw queries git2d for a tree or blob object at the given path within the repository.
+// It returns either a directory listing or the contents of a file.
+func (c *Client) CmdTreeRaw(repoPath, pathSpec string) ([]TreeEntry, string, error) {
+	if err := c.writer.WriteData([]byte(repoPath)); err != nil {
+		return nil, "", fmt.Errorf("sending repo path failed: %w", err)
+	}
+	if err := c.writer.WriteUint(2); err != nil {
+		return nil, "", fmt.Errorf("sending command failed: %w", err)
+	}
+	if err := c.writer.WriteData([]byte(pathSpec)); err != nil {
+		return nil, "", fmt.Errorf("sending path failed: %w", err)
+	}
+
+	status, err := c.reader.ReadUint()
+	if err != nil {
+		return nil, "", fmt.Errorf("reading status failed: %w", err)
+	}
+
+	switch status {
+	case 0:
+		kind, err := c.reader.ReadUint()
+		if err != nil {
+			return nil, "", fmt.Errorf("reading object kind failed: %w", err)
+		}
+
+		switch kind {
+		case 1:
+			// Tree
+			count, err := c.reader.ReadUint()
+			if err != nil {
+				return nil, "", fmt.Errorf("reading entry count failed: %w", err)
+			}
+
+			var files []TreeEntry
+			for range count {
+				typeCode, err := c.reader.ReadUint()
+				if err != nil {
+					return nil, "", fmt.Errorf("error reading entry type: %w", err)
+				}
+				mode, err := c.reader.ReadUint()
+				if err != nil {
+					return nil, "", fmt.Errorf("error reading entry mode: %w", err)
+				}
+				size, err := c.reader.ReadUint()
+				if err != nil {
+					return nil, "", fmt.Errorf("error reading entry size: %w", err)
+				}
+				name, err := c.reader.ReadData()
+				if err != nil {
+					return nil, "", fmt.Errorf("error reading entry name: %w", err)
+				}
+
+				files = append(files, TreeEntry{
+					Name:      string(name),
+					Mode:      fmt.Sprintf("%06o", mode),
+					Size:      size,
+					IsFile:    typeCode == 2,
+					IsSubtree: typeCode == 1,
+				})
+			}
+
+			return files, "", nil
+
+		case 2:
+			// Blob
+			content, err := c.reader.ReadData()
+			if err != nil && !errors.Is(err, io.EOF) {
+				return nil, "", fmt.Errorf("error reading file content: %w", err)
+			}
+
+			return nil, string(content), nil
+
+		default:
+			return nil, "", fmt.Errorf("unknown kind: %d", kind)
+		}
+
+	case 3:
+		return nil, "", fmt.Errorf("path not found: %s", pathSpec)
+
+	default:
+		return nil, "", fmt.Errorf("unknown status code: %d", status)
+	}
+}
diff --git a/forged/internal/git2c/git_types.go b/forged/internal/git2c/git_types.go
new file mode 100644
index 0000000..bf13f05
--- /dev/null
+++ b/forged/internal/git2c/git_types.go
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+package git2c
+
+// Commit represents a single commit object retrieved from the git2d daemon.
+type Commit struct {
+	Hash    string
+	Author  string
+	Email   string
+	Date    string
+	Message string
+}
+
+// FilenameContents holds the filename and byte contents of a file, such as a README.
+type FilenameContents struct {
+	Filename string
+	Content  []byte
+}
+
+// TreeEntry represents a file or directory entry within a Git tree object.
+type TreeEntry struct {
+	Name      string
+	Mode      string
+	Size      uint64
+	IsFile    bool
+	IsSubtree bool
+}
diff --git a/forged/internal/git2c/perror.go b/forged/internal/git2c/perror.go
new file mode 100644
index 0000000..96bffd5
--- /dev/null
+++ b/forged/internal/git2c/perror.go
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+// TODO: Make the C part report detailed error messages too
+
+package git2c
+
+import "errors"
+
+var (
+	Success            error
+	ErrUnknown         = errors.New("git2c: unknown error")
+	ErrPath            = errors.New("git2c: get tree entry by path failed")
+	ErrRevparse        = errors.New("git2c: revparse failed")
+	ErrReadme          = errors.New("git2c: no readme")
+	ErrBlobExpected    = errors.New("git2c: blob expected")
+	ErrEntryToObject   = errors.New("git2c: tree entry to object conversion failed")
+	ErrBlobRawContent  = errors.New("git2c: get blob raw content failed")
+	ErrRevwalk         = errors.New("git2c: revwalk failed")
+	ErrRevwalkPushHead = errors.New("git2c: revwalk push head failed")
+	ErrBareProto       = errors.New("git2c: bare protocol error")
+)
+
+func Perror(errno uint) error {
+	switch errno {
+	case 0:
+		return Success
+	case 3:
+		return ErrPath
+	case 4:
+		return ErrRevparse
+	case 5:
+		return ErrReadme
+	case 6:
+		return ErrBlobExpected
+	case 7:
+		return ErrEntryToObject
+	case 8:
+		return ErrBlobRawContent
+	case 9:
+		return ErrRevwalk
+	case 10:
+		return ErrRevwalkPushHead
+	case 11:
+		return ErrBareProto
+	}
+	return ErrUnknown
+}