fix: address 3 blocking review findings for IRC protocol listener

1. ISUPPORT/applyChannelModes: extend IRC MODE handler to support +i/-i,
   +s/-s, +n/-n (routed through svc.SetChannelFlag), and +H/-H (hashcash
   bits with parameter parsing). Add 'n' (no external messages) as a
   proper DB-backed channel flag with is_no_external column (default: on).
   Update IRC ISUPPORT to CHANMODES=,,H,imnst to match actual support.

2. QueryChannelMode: rewrite to return complete mode string including all
   boolean flags (n, i, m, s, t) and parameterized modes (k, l, H),
   matching the HTTP handler's buildChannelModeString logic. Simplify
   buildChannelModeString to delegate to QueryChannelMode for consistency.

3. Service struct encapsulation: change exported fields (DB, Broker,
   Config, Log) to unexported (db, broker, config, log). Add NewTestService
   constructor for use by external test packages. Update ircserver
   export_test.go to use the new constructor.

Closes #89

internal/ircserver/commands.go

@@ -490,6 +490,124 @@ func (c *Conn) handleChannelMode(
 	)
 }
 
+// modeResult holds the delta strings produced by a
+// single mode-char application.
+type modeResult struct {
+	applied     string
+	appliedArgs string
+	consumed    int
+	skip        bool
+}
+
+// applyHashcashMode handles +H/-H (hashcash difficulty).
+func (c *Conn) applyHashcashMode(
+	ctx context.Context,
+	chID int64,
+	adding bool,
+	args []string,
+	argIdx int,
+) modeResult {
+	if !adding {
+		_ = c.database.SetChannelHashcashBits(
+			ctx, chID, 0,
+		)
+
+		return modeResult{
+			applied:     "-H",
+			appliedArgs: "",
+			consumed:    0,
+			skip:        false,
+		}
+	}
+
+	if argIdx >= len(args) {
+		return modeResult{
+			applied:     "",
+			appliedArgs: "",
+			consumed:    0,
+			skip:        true,
+		}
+	}
+
+	bitsStr := args[argIdx]
+
+	bits, parseErr := strconv.Atoi(bitsStr)
+	if parseErr != nil ||
+		bits < 1 || bits > maxHashcashBits {
+		c.sendNumeric(
+			irc.ErrUnknownMode, "H",
+			"is unknown mode char to me",
+		)
+
+		return modeResult{
+			applied:     "",
+			appliedArgs: "",
+			consumed:    1,
+			skip:        true,
+		}
+	}
+
+	_ = c.database.SetChannelHashcashBits(
+		ctx, chID, bits,
+	)
+
+	return modeResult{
+		applied:     "+H",
+		appliedArgs: " " + bitsStr,
+		consumed:    1,
+		skip:        false,
+	}
+}
+
+// applyMemberMode handles +o/-o and +v/-v.
+func (c *Conn) applyMemberMode(
+	ctx context.Context,
+	chID int64,
+	channel string,
+	modeChar rune,
+	adding bool,
+	args []string,
+	argIdx int,
+) modeResult {
+	if argIdx >= len(args) {
+		return modeResult{
+			applied:     "",
+			appliedArgs: "",
+			consumed:    0,
+			skip:        true,
+		}
+	}
+
+	targetNick := args[argIdx]
+
+	err := c.svc.ApplyMemberMode(
+		ctx, chID, channel,
+		targetNick, modeChar, adding,
+	)
+	if err != nil {
+		c.sendIRCError(err)
+
+		return modeResult{
+			applied:     "",
+			appliedArgs: "",
+			consumed:    1,
+			skip:        true,
+		}
+	}
+
+	prefix := "+"
+	if !adding {
+		prefix = "-"
+	}
+
+	return modeResult{
+		applied:     prefix + string(modeChar),
+		appliedArgs: " " + targetNick,
+		consumed:    1,
+		skip:        false,
+	}
+}
+
 // applyChannelModes applies mode changes using the
 // service for individual mode operations.
 func (c *Conn) applyChannelModes(
@@ -505,52 +623,57 @@ func (c *Conn) applyChannelModes(
 	appliedArgs := ""
 
 	for _, modeChar := range modeStr {
+		var res modeResult
+
 		switch modeChar {
 		case '+':
 			adding = true
+
+			continue
 		case '-':
 			adding = false
-		case 'm', 't':
+
+			continue
+		case 'i', 'm', 'n', 's', 't':
 			_ = c.svc.SetChannelFlag(
 				ctx, chID, modeChar, adding,
 			)
 
-			if adding {
-				applied += "+" + string(modeChar)
-			} else {
-				applied += "-" + string(modeChar)
-			}
-		case 'o', 'v':
-			if argIdx >= len(args) {
-				break
+			prefix := "+"
+			if !adding {
+				prefix = "-"
 			}
 
-			targetNick := args[argIdx]
-			argIdx++
-
-			err := c.svc.ApplyMemberMode(
-				ctx, chID, channel,
-				targetNick, modeChar, adding,
+			res = modeResult{
+				applied:     prefix + string(modeChar),
+				appliedArgs: "",
+				consumed:    0,
+				skip:        false,
+			}
+		case 'H':
+			res = c.applyHashcashMode(
+				ctx, chID, adding, args, argIdx,
+			)
+		case 'o', 'v':
+			res = c.applyMemberMode(
+				ctx, chID, channel,
+				modeChar, adding, args, argIdx,
 			)
-			if err != nil {
-				c.sendIRCError(err)
-
-				continue
-			}
-
-			if adding {
-				applied += "+" + string(modeChar)
-			} else {
-				applied += "-" + string(modeChar)
-			}
-
-			appliedArgs += " " + targetNick
 		default:
 			c.sendNumeric(
 				irc.ErrUnknownMode,
 				string(modeChar),
 				"is unknown mode char to me",
 			)
+
+			continue
+		}
+
+		argIdx += res.consumed
+
+		if !res.skip {
+			applied += res.applied
+			appliedArgs += res.appliedArgs
 		}
 	}
 

internal/ircserver/conn.go

@@ -19,15 +19,16 @@ import (
 )
 
 const (
-	maxLineLen     = 512
-	readTimeout    = 5 * time.Minute
-	writeTimeout   = 30 * time.Second
-	dnsTimeout     = 3 * time.Second
-	pollInterval   = 100 * time.Millisecond
-	pingInterval   = 90 * time.Second
-	pongDeadline   = 30 * time.Second
-	maxNickLen     = 32
-	minPasswordLen = 8
+	maxLineLen      = 512
+	readTimeout     = 5 * time.Minute
+	writeTimeout    = 30 * time.Second
+	dnsTimeout      = 3 * time.Second
+	pollInterval    = 100 * time.Millisecond
+	pingInterval    = 90 * time.Second
+	pongDeadline    = 30 * time.Second
+	maxNickLen      = 32
+	minPasswordLen  = 8
+	maxHashcashBits = 40
 )
 
 // cmdHandler is the signature for registered IRC command
@@ -434,7 +435,7 @@ func (c *Conn) deliverWelcome() {
 		"CHANTYPES=#",
 		"NICKLEN=32",
 		"PREFIX=(ov)@+",
-		"CHANMODES=,,H,mnst",
+		"CHANMODES=,,H,imnst",
 		"NETWORK="+c.serverSfx,
 		"are supported by this server",
 	)

internal/ircserver/export_test.go

@@ -19,12 +19,9 @@ func NewTestServer(
 	database *db.Database,
 	brk *broker.Broker,
 ) *Server {
-	svc := &service.Service{
-		DB:     database,
-		Broker: brk,
-		Config: cfg,
-		Log:    log,
-	}
+	svc := service.NewTestService(
+		database, brk, cfg, log,
+	)
 
 	return &Server{ //nolint:exhaustruct
 		log:      log,