From 807e74c8cb04b834e82d73da036ca9585b559201 Mon Sep 17 00:00:00 2001
From: Runxi Yu <me@runxiyu.org>
Date: Wed, 15 Jan 2025 01:48:18 +0800
Subject: Add an IMAP stub

---
 main.go       |  1 +
 serve_imap.go | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 serve_imap.go

diff --git a/main.go b/main.go
index 51540f9..60082da 100644
--- a/main.go
+++ b/main.go
@@ -18,6 +18,7 @@ func main() {
 	}
 
 	go serve_mx()
+	go serve_imap()
 
 	deadlock := make(chan struct{})
 	deadlock <- struct{}{}
diff --git a/serve_imap.go b/serve_imap.go
new file mode 100644
index 0000000..742bb0f
--- /dev/null
+++ b/serve_imap.go
@@ -0,0 +1,79 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"crypto/tls"
+	"net"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"go.lindenii.runxiyu.org/lindenii-common/clog"
+)
+
+type imap_server_state_t uint
+
+const (
+	imap_server_state_begin imap_server_state_t = iota
+	imap_server_state_helo
+	imap_server_state_mail
+	imap_server_state_rcpt
+)
+
+type imap_recv_session struct {
+	buf_conn       *bufio.ReadWriter
+	net_conn       net.Conn
+	tls_conn       *tls.Conn
+	my_server_name string
+	db             *pgxpool.Pool
+}
+
+func (session *imap_recv_session) handle(ctx context.Context) error {
+	session.buf_conn = bufio.NewReadWriter(bufio.NewReader(session.net_conn), bufio.NewWriter(session.net_conn))
+	session.buf_conn.WriteString("Not implemented\r\n")
+	session.buf_conn.Flush()
+	return nil
+}
+
+func imap_new_session(ctx context.Context, net_conn net.Conn) error {
+	session := imap_recv_session{
+		net_conn: net_conn,
+	}
+	return session.handle(ctx)
+}
+
+func serve_imap() {
+	var imap_net, imap_addr string
+	config_consistent_run(func() {
+		imap_net = config.IMAP.Net
+		imap_addr = config.IMAP.Addr
+	})
+	listener, err := net.Listen(imap_net, imap_addr)
+	if err != nil {
+		clog.Fatal(1, "IMAP: Cannot listen: "+err.Error())
+	}
+	defer listener.Close()
+	clog.Info("IMAP: Listening via " + imap_net + " on " + imap_addr)
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			clog.Error("IMAP: Cannot accept connection: " + err.Error())
+		}
+		clog.Info("IMAP: Accepted connection from " + conn.RemoteAddr().String())
+
+		go func() {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			err := imap_new_session(ctx, conn)
+			if err != nil {
+				if err == err_connection_handler_eof {
+					clog.Info("IMAP: Connection for " + conn.RemoteAddr().String() + " closed with EOF")
+				} else {
+					clog.Error("IMAP: Connection handler for " + conn.RemoteAddr().String() + " returned error: " + err.Error())
+				}
+			} else {
+				clog.Info("IMAP: Connection for " + conn.RemoteAddr().String() + " closed gracefully")
+			}
+		}()
+	}
+}
-- 
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