library: io: implement client type and I/O methods

Path discovery is ported directly from Discord's C++ example, Windows has a crazy looking socket path that needs special syscall magic to dial, so we'll put that off for the time being.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

io.go

@@ -0,0 +1,91 @@
+package rpcfetch
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"net"
+	"os"
+	"strconv"
+)
+
+type Client struct {
+	id string
+
+	dialed bool
+	active bool
+	net.Conn
+}
+
+// Raw wraps around the Raw method to provide generic json parsing
+func Raw[T any](d *Client, opcode uint32, payload any) (uint32, T, error) {
+	var p T
+
+	opcodeResp, payloadResp, err := d.Raw(opcode, payload)
+	if err != nil {
+		return opcodeResp, p, err
+	}
+
+	return opcodeResp, p, json.Unmarshal(payloadResp, &p)
+}
+
+// Raw writes a raw payload to Discord and returns the response opcode and payload
+func (d *Client) Raw(opcode uint32, payload any) (uint32, []byte, error) {
+	if err := binary.Write(d.Conn, binary.LittleEndian, opcode); err != nil {
+		return 0, nil, err
+	}
+
+	if p, err := json.Marshal(payload); err != nil {
+		return 0, nil, err
+	} else {
+		if err = binary.Write(d.Conn, binary.LittleEndian, uint32(len(p))); err != nil {
+			return 0, nil, err
+		}
+
+		if _, err = d.Conn.Write(p); err != nil {
+			return 0, nil, err
+		}
+	}
+
+	var (
+		opcodeResp uint32
+		lengthResp uint32
+	)
+
+	if err := binary.Read(d.Conn, binary.LittleEndian, &opcodeResp); err != nil {
+		return 0, nil, err
+	}
+
+	if err := binary.Read(d.Conn, binary.LittleEndian, &lengthResp); err != nil {
+		return 0, nil, err
+	}
+
+	payloadResp := make([]byte, lengthResp)
+	_, err := d.Read(payloadResp)
+	return opcodeResp, payloadResp, err
+}
+
+// New sets up and returns the reference to a new Client
+func New(id string) *Client {
+	d := &Client{
+		id: id,
+	}
+
+	return d
+}
+
+func sockPath() string {
+	snap := "/run/user/" + strconv.Itoa(os.Getuid()) + "/snap.discord"
+
+	if _, err := os.Stat(snap); err == nil {
+		return snap
+	}
+
+	for _, env := range []string{"XDG_RUNTIME_DIR", "TMPDIR", "TMP", "TEMP"} {
+		if val, ok := os.LookupEnv(env); ok {
+			return val
+		}
+	}
+
+	// fallback
+	return "/tmp"
+}

io_unix.go

@@ -0,0 +1,20 @@
+package rpcfetch
+
+import (
+	"net"
+	"time"
+)
+
+func (d *Client) dial() error {
+	if d.dialed {
+		panic("attempted to dial on open client")
+	}
+
+	if conn, err := net.DialTimeout("unix", sockPath()+"/discord-ipc-0", 5*time.Second); err != nil {
+		return err
+	} else {
+		d.Conn = conn
+		d.dialed = true
+	}
+	return nil
+}