feat: add IRC wire protocol listener with shared service layer

Add a traditional IRC wire protocol listener (RFC 1459/2812) on
configurable port (default :6667), sharing business logic with
the HTTP API via a new service layer.

- IRC listener: NICK, USER, PASS, JOIN, PART, PRIVMSG, NOTICE,
  TOPIC, MODE, KICK, QUIT, NAMES, LIST, WHOIS, WHO, AWAY, OPER,
  INVITE, LUSERS, MOTD, PING/PONG, CAP
- Service layer: shared logic for both transports including
  channel join (with Tier 2 checks: ban/invite/key/limit),
  message send (with ban + moderation checks), nick change,
  topic, kick, mode, quit broadcast, away, oper, invite
- BroadcastQuit uses FanOut pattern (one insert, N enqueues)
- HTTP handlers delegate to service for all command logic
- Tier 2 mode operations (+b/+i/+s/+k/+l) use service methods

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/ircserver/parser_test.go

@@ -0,0 +1,328 @@
+package ircserver_test
+
+import (
+	"testing"
+
+	"git.eeqj.de/sneak/neoirc/internal/ircserver"
+)
+
+//nolint:funlen // table-driven test
+func TestParseMessage(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		input   string
+		want    *ircserver.Message
+		wantNil bool
+	}{
+		{
+			name:    "empty",
+			input:   "",
+			want:    nil,
+			wantNil: true,
+		},
+		{
+			name:  "simple command",
+			input: "PING",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "PING",
+				Params:  nil,
+			},
+			wantNil: false,
+		},
+		{
+			name:  "command with one param",
+			input: "NICK alice",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "NICK",
+				Params:  []string{"alice"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "command case insensitive",
+			input: "nick Alice",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "NICK",
+				Params:  []string{"Alice"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "privmsg with trailing",
+			input: "PRIVMSG #general :hello world",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "PRIVMSG",
+				Params:  []string{"#general", "hello world"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "with prefix",
+			input: ":server.example.com 001 alice :Welcome to IRC",
+			want: &ircserver.Message{
+				Prefix:  "server.example.com",
+				Command: "001",
+				Params:  []string{"alice", "Welcome to IRC"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "user command",
+			input: "USER alice 0 * :Alice Smith",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "USER",
+				Params: []string{
+					"alice", "0", "*", "Alice Smith",
+				},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "join channel",
+			input: "JOIN #general",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "JOIN",
+				Params:  []string{"#general"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "quit with trailing",
+			input: "QUIT :leaving now",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "QUIT",
+				Params:  []string{"leaving now"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "quit without reason",
+			input: "QUIT",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "QUIT",
+				Params:  nil,
+			},
+			wantNil: false,
+		},
+		{
+			name:  "mode query",
+			input: "MODE #general",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "MODE",
+				Params:  []string{"#general"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "kick with reason",
+			input: "KICK #general bob :misbehaving",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "KICK",
+				Params: []string{
+					"#general", "bob", "misbehaving",
+				},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "empty trailing",
+			input: "PRIVMSG #general :",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "PRIVMSG",
+				Params:  []string{"#general", ""},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "pass command",
+			input: "PASS mysecret",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "PASS",
+				Params:  []string{"mysecret"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "ping with server",
+			input: "PING :irc.example.com",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "PING",
+				Params:  []string{"irc.example.com"},
+			},
+			wantNil: false,
+		},
+		{
+			name:  "topic with trailing spaces",
+			input: "TOPIC #general :Welcome to the channel!",
+			want: &ircserver.Message{
+				Prefix:  "",
+				Command: "TOPIC",
+				Params: []string{
+					"#general",
+					"Welcome to the channel!",
+				},
+			},
+			wantNil: false,
+		},
+	}
+
+	for _, testCase := range tests {
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := ircserver.ParseMessage(testCase.input)
+			if testCase.wantNil {
+				if got != nil {
+					t.Fatalf("expected nil, got %+v", got)
+				}
+
+				return
+			}
+
+			if got == nil {
+				t.Fatal("expected non-nil message")
+			}
+
+			if got.Prefix != testCase.want.Prefix {
+				t.Errorf(
+					"prefix: got %q, want %q",
+					got.Prefix, testCase.want.Prefix,
+				)
+			}
+
+			if got.Command != testCase.want.Command {
+				t.Errorf(
+					"command: got %q, want %q",
+					got.Command, testCase.want.Command,
+				)
+			}
+
+			if len(got.Params) != len(testCase.want.Params) {
+				t.Fatalf(
+					"params length: got %d, want %d (%v vs %v)",
+					len(got.Params),
+					len(testCase.want.Params),
+					got.Params,
+					testCase.want.Params,
+				)
+			}
+
+			for i, p := range got.Params {
+				if p != testCase.want.Params[i] {
+					t.Errorf(
+						"param[%d]: got %q, want %q",
+						i, p, testCase.want.Params[i],
+					)
+				}
+			}
+		})
+	}
+}
+
+func TestFormatMessage(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		prefix  string
+		command string
+		params  []string
+		want    string
+	}{
+		{
+			name:    "simple command",
+			prefix:  "",
+			command: "PING",
+			params:  nil,
+			want:    "PING",
+		},
+		{
+			name:    "with prefix",
+			prefix:  "server",
+			command: "PONG",
+			params:  []string{"server"},
+			want:    ":server PONG server",
+		},
+		{
+			name:    "privmsg with trailing",
+			prefix:  "alice!alice@host",
+			command: "PRIVMSG",
+			params:  []string{"#general", "hello world"},
+			want:    ":alice!alice@host PRIVMSG #general :hello world",
+		},
+		{
+			name:    "numeric reply",
+			prefix:  "server",
+			command: "001",
+			params:  []string{"alice", "Welcome to IRC"},
+			want:    ":server 001 alice :Welcome to IRC",
+		},
+		{
+			name:    "empty trailing",
+			prefix:  "server",
+			command: "PRIVMSG",
+			params:  []string{"#chan", ""},
+			want:    ":server PRIVMSG #chan :",
+		},
+	}
+
+	for _, testCase := range tests {
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := ircserver.FormatMessage(
+				testCase.prefix, testCase.command, testCase.params...,
+			)
+			if got != testCase.want {
+				t.Errorf("got %q, want %q", got, testCase.want)
+			}
+		})
+	}
+}
+
+func TestParseFormatRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	// Round-trip only works for lines where the last
+	// parameter either contains a space (gets ':' prefix
+	// on format) or is a non-trailing single token.
+	lines := []string{
+		"PING",
+		"NICK alice",
+		"PRIVMSG #general :hello world",
+		"JOIN #general",
+		"MODE #general",
+	}
+
+	for _, line := range lines {
+		msg := ircserver.ParseMessage(line)
+		if msg == nil {
+			t.Fatalf("failed to parse: %q", line)
+		}
+
+		formatted := ircserver.FormatMessage(
+			msg.Prefix, msg.Command, msg.Params...,
+		)
+		if formatted != line {
+			t.Errorf(
+				"round-trip failed: input %q, got %q",
+				line, formatted,
+			)
+		}
+	}
+}