style: fix all golangci-lint issues and format code (refs #17)

Fix 380 lint violations across all Go source files including wsl_v5,
nlreturn, noinlineerr, errcheck, funlen, funcorder, tagliatelle,
perfsprint, modernize, revive, gosec, ireturn, mnd, forcetypeassert,
cyclop, and others.

Key changes:
- Split large handler/command functions into smaller methods
- Extract scan helpers for database queries
- Reorder exported/unexported methods per funcorder
- Add sentinel errors in models package
- Use camelCase JSON tags per tagliatelle defaults
- Add package comments
- Fix .gitignore to not exclude cmd/chat-cli directory

internal/db/db.go

@@ -88,8 +88,10 @@ func NewTest(dsn string) (*Database, error) {
 	}
 
 	// Item 9: Enable foreign keys
-	if _, err := d.Exec("PRAGMA foreign_keys = ON"); err != nil {
+	_, err = d.Exec("PRAGMA foreign_keys = ON") //nolint:noctx // no context in sql.Open path
+	if err != nil {
 		_ = d.Close()
+
 		return nil, fmt.Errorf("enable foreign keys: %w", err)
 	}
 
@@ -162,7 +164,7 @@ func (s *Database) GetChannelByID(
 	return c, nil
 }
 
-// GetUserByNick looks up a user by their nick.
+// GetUserByNickModel looks up a user by their nick.
 func (s *Database) GetUserByNickModel(
 	ctx context.Context,
 	nick string,
@@ -185,7 +187,7 @@ func (s *Database) GetUserByNickModel(
 	return u, nil
 }
 
-// GetUserByToken looks up a user by their auth token.
+// GetUserByTokenModel looks up a user by their auth token.
 func (s *Database) GetUserByTokenModel(
 	ctx context.Context,
 	token string,
@@ -219,6 +221,7 @@ func (s *Database) DeleteAuthToken(
 	_, err := s.db.ExecContext(ctx,
 		`DELETE FROM auth_tokens WHERE token = ?`, token,
 	)
+
 	return err
 }
 
@@ -231,10 +234,11 @@ func (s *Database) UpdateUserLastSeen(
 		`UPDATE users SET last_seen_at = CURRENT_TIMESTAMP WHERE id = ?`,
 		userID,
 	)
+
 	return err
 }
 
-// CreateUser inserts a new user into the database.
+// CreateUserModel inserts a new user into the database.
 func (s *Database) CreateUserModel(
 	ctx context.Context,
 	id, nick, passwordHash string,
@@ -394,6 +398,7 @@ func (s *Database) DequeueMessages(
 	if err != nil {
 		return nil, err
 	}
+
 	defer func() { _ = rows.Close() }()
 
 	entries := []*models.MessageQueueEntry{}
@@ -423,14 +428,14 @@ func (s *Database) AckMessages(
 	}
 
 	placeholders := make([]string, len(entryIDs))
-	args := make([]interface{}, len(entryIDs))
+	args := make([]any, len(entryIDs))
 
 	for i, id := range entryIDs {
 		placeholders[i] = "?"
 		args[i] = id
 	}
 
-	query := fmt.Sprintf(
+	query := fmt.Sprintf( //nolint:gosec // placeholders are ?, not user input
 		"DELETE FROM message_queue WHERE id IN (%s)",
 		strings.Join(placeholders, ","),
 	)
@@ -549,7 +554,8 @@ func (s *Database) connect(ctx context.Context) error {
 	s.log.Info("database connected")
 
 	// Item 9: Enable foreign keys on every connection
-	if _, err := s.db.ExecContext(ctx, "PRAGMA foreign_keys = ON"); err != nil {
+	_, err = s.db.ExecContext(ctx, "PRAGMA foreign_keys = ON")
+	if err != nil {
 		return fmt.Errorf("enable foreign keys: %w", err)
 	}
 
@@ -676,41 +682,54 @@ func (s *Database) applyMigrations(
 			"version", m.version, "name", m.name,
 		)
 
-		tx, err := s.db.BeginTx(ctx, nil)
+		err = s.executeMigration(ctx, m)
 		if err != nil {
-			return fmt.Errorf(
-				"begin tx for migration %d: %w", m.version, err,
-			)
-		}
-
-		_, err = tx.ExecContext(ctx, m.sql)
-		if err != nil {
-			_ = tx.Rollback()
-
-			return fmt.Errorf(
-				"apply migration %d (%s): %w",
-				m.version, m.name, err,
-			)
-		}
-
-		_, err = tx.ExecContext(ctx,
-			"INSERT INTO schema_migrations (version) VALUES (?)",
-			m.version,
-		)
-		if err != nil {
-			_ = tx.Rollback()
-
-			return fmt.Errorf(
-				"record migration %d: %w", m.version, err,
-			)
-		}
-
-		if err := tx.Commit(); err != nil {
-			return fmt.Errorf(
-				"commit migration %d: %w", m.version, err,
-			)
+			return err
 		}
 	}
 
 	return nil
 }
+
+func (s *Database) executeMigration(
+	ctx context.Context,
+	m migration,
+) error {
+	tx, err := s.db.BeginTx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf(
+			"begin tx for migration %d: %w", m.version, err,
+		)
+	}
+
+	_, err = tx.ExecContext(ctx, m.sql)
+	if err != nil {
+		_ = tx.Rollback()
+
+		return fmt.Errorf(
+			"apply migration %d (%s): %w",
+			m.version, m.name, err,
+		)
+	}
+
+	_, err = tx.ExecContext(ctx,
+		"INSERT INTO schema_migrations (version) VALUES (?)",
+		m.version,
+	)
+	if err != nil {
+		_ = tx.Rollback()
+
+		return fmt.Errorf(
+			"record migration %d: %w", m.version, err,
+		)
+	}
+
+	err = tx.Commit()
+	if err != nil {
+		return fmt.Errorf(
+			"commit migration %d: %w", m.version, err,
+		)
+	}
+
+	return nil
+}

internal/db/queries.go

@@ -3,107 +3,144 @@ package db
 import (
 	"context"
 	"crypto/rand"
+	"database/sql"
 	"encoding/hex"
 	"fmt"
 	"time"
 )
 
+const (
+	defaultMessageLimit = 50
+	defaultPollLimit    = 100
+	tokenBytes          = 32
+)
+
 func generateToken() string {
-	b := make([]byte, 32)
+	b := make([]byte, tokenBytes)
 	_, _ = rand.Read(b)
+
 	return hex.EncodeToString(b)
 }
 
-// CreateUser registers a new user with the given nick and returns the user with token.
-func (s *Database) CreateUser(ctx context.Context, nick string) (int64, string, error) {
+// CreateUser registers a new user with the given nick and
+// returns the user with token.
+func (s *Database) CreateUser(
+	ctx context.Context,
+	nick string,
+) (int64, string, error) {
 	token := generateToken()
 	now := time.Now()
+
 	res, err := s.db.ExecContext(ctx,
 		"INSERT INTO users (nick, token, created_at, last_seen) VALUES (?, ?, ?, ?)",
 		nick, token, now, now)
 	if err != nil {
 		return 0, "", fmt.Errorf("create user: %w", err)
 	}
+
 	id, _ := res.LastInsertId()
+
 	return id, token, nil
 }
 
-// GetUserByToken returns user id and nick for a given auth token.
-func (s *Database) GetUserByToken(ctx context.Context, token string) (int64, string, error) {
+// GetUserByToken returns user id and nick for a given auth
+// token.
+func (s *Database) GetUserByToken(
+	ctx context.Context,
+	token string,
+) (int64, string, error) {
 	var id int64
+
 	var nick string
-	err := s.db.QueryRowContext(ctx, "SELECT id, nick FROM users WHERE token = ?", token).Scan(&id, &nick)
+
+	err := s.db.QueryRowContext(
+		ctx,
+		"SELECT id, nick FROM users WHERE token = ?",
+		token,
+	).Scan(&id, &nick)
 	if err != nil {
 		return 0, "", err
 	}
+
 	// Update last_seen
-	_, _ = s.db.ExecContext(ctx, "UPDATE users SET last_seen = ? WHERE id = ?", time.Now(), id)
+	_, _ = s.db.ExecContext(
+		ctx,
+		"UPDATE users SET last_seen = ? WHERE id = ?",
+		time.Now(), id,
+	)
+
 	return id, nick, nil
 }
 
 // GetUserByNick returns user id for a given nick.
-func (s *Database) GetUserByNick(ctx context.Context, nick string) (int64, error) {
+func (s *Database) GetUserByNick(
+	ctx context.Context,
+	nick string,
+) (int64, error) {
 	var id int64
-	err := s.db.QueryRowContext(ctx, "SELECT id FROM users WHERE nick = ?", nick).Scan(&id)
+
+	err := s.db.QueryRowContext(
+		ctx,
+		"SELECT id FROM users WHERE nick = ?",
+		nick,
+	).Scan(&id)
+
 	return id, err
 }
 
-// GetOrCreateChannel returns the channel id, creating it if needed.
-func (s *Database) GetOrCreateChannel(ctx context.Context, name string) (int64, error) {
+// GetOrCreateChannel returns the channel id, creating it if
+// needed.
+func (s *Database) GetOrCreateChannel(
+	ctx context.Context,
+	name string,
+) (int64, error) {
 	var id int64
-	err := s.db.QueryRowContext(ctx, "SELECT id FROM channels WHERE name = ?", name).Scan(&id)
+
+	err := s.db.QueryRowContext(
+		ctx,
+		"SELECT id FROM channels WHERE name = ?",
+		name,
+	).Scan(&id)
 	if err == nil {
 		return id, nil
 	}
+
 	now := time.Now()
+
 	res, err := s.db.ExecContext(ctx,
 		"INSERT INTO channels (name, created_at, updated_at) VALUES (?, ?, ?)",
 		name, now, now)
 	if err != nil {
 		return 0, fmt.Errorf("create channel: %w", err)
 	}
+
 	id, _ = res.LastInsertId()
+
 	return id, nil
 }
 
 // JoinChannel adds a user to a channel.
-func (s *Database) JoinChannel(ctx context.Context, channelID, userID int64) error {
+func (s *Database) JoinChannel(
+	ctx context.Context,
+	channelID, userID int64,
+) error {
 	_, err := s.db.ExecContext(ctx,
 		"INSERT OR IGNORE INTO channel_members (channel_id, user_id, joined_at) VALUES (?, ?, ?)",
 		channelID, userID, time.Now())
+
 	return err
 }
 
 // PartChannel removes a user from a channel.
-func (s *Database) PartChannel(ctx context.Context, channelID, userID int64) error {
+func (s *Database) PartChannel(
+	ctx context.Context,
+	channelID, userID int64,
+) error {
 	_, err := s.db.ExecContext(ctx,
 		"DELETE FROM channel_members WHERE channel_id = ? AND user_id = ?",
 		channelID, userID)
-	return err
-}
 
-// ListChannels returns all channels the user has joined.
-func (s *Database) ListChannels(ctx context.Context, userID int64) ([]ChannelInfo, error) {
-	rows, err := s.db.QueryContext(ctx,
-		`SELECT c.id, c.name, c.topic FROM channels c
-		 INNER JOIN channel_members cm ON cm.channel_id = c.id
-		 WHERE cm.user_id = ? ORDER BY c.name`, userID)
-	if err != nil {
-		return nil, err
-	}
-	defer rows.Close()
-	var channels []ChannelInfo
-	for rows.Next() {
-		var ch ChannelInfo
-		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Topic); err != nil {
-			return nil, err
-		}
-		channels = append(channels, ch)
-	}
-	if channels == nil {
-		channels = []ChannelInfo{}
-	}
-	return channels, nil
+	return err
 }
 
 // ChannelInfo is a lightweight channel representation.
@@ -113,28 +150,44 @@ type ChannelInfo struct {
 	Topic string `json:"topic"`
 }
 
-// ChannelMembers returns all members of a channel.
-func (s *Database) ChannelMembers(ctx context.Context, channelID int64) ([]MemberInfo, error) {
+// ListChannels returns all channels the user has joined.
+func (s *Database) ListChannels(
+	ctx context.Context,
+	userID int64,
+) ([]ChannelInfo, error) {
 	rows, err := s.db.QueryContext(ctx,
-		`SELECT u.id, u.nick, u.last_seen FROM users u
-		 INNER JOIN channel_members cm ON cm.user_id = u.id
-		 WHERE cm.channel_id = ? ORDER BY u.nick`, channelID)
+		`SELECT c.id, c.name, c.topic FROM channels c
+		 INNER JOIN channel_members cm ON cm.channel_id = c.id
+		 WHERE cm.user_id = ? ORDER BY c.name`, userID)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-	var members []MemberInfo
+
+	defer func() { _ = rows.Close() }()
+
+	var channels []ChannelInfo
+
 	for rows.Next() {
-		var m MemberInfo
-		if err := rows.Scan(&m.ID, &m.Nick, &m.LastSeen); err != nil {
+		var ch ChannelInfo
+
+		err := rows.Scan(&ch.ID, &ch.Name, &ch.Topic)
+		if err != nil {
 			return nil, err
 		}
-		members = append(members, m)
+
+		channels = append(channels, ch)
 	}
-	if members == nil {
-		members = []MemberInfo{}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
 	}
-	return members, nil
+
+	if channels == nil {
+		channels = []ChannelInfo{}
+	}
+
+	return channels, nil
 }
 
 // MemberInfo represents a channel member.
@@ -144,6 +197,46 @@ type MemberInfo struct {
 	LastSeen time.Time `json:"lastSeen"`
 }
 
+// ChannelMembers returns all members of a channel.
+func (s *Database) ChannelMembers(
+	ctx context.Context,
+	channelID int64,
+) ([]MemberInfo, error) {
+	rows, err := s.db.QueryContext(ctx,
+		`SELECT u.id, u.nick, u.last_seen FROM users u
+		 INNER JOIN channel_members cm ON cm.user_id = u.id
+		 WHERE cm.channel_id = ? ORDER BY u.nick`, channelID)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() { _ = rows.Close() }()
+
+	var members []MemberInfo
+
+	for rows.Next() {
+		var m MemberInfo
+
+		err := rows.Scan(&m.ID, &m.Nick, &m.LastSeen)
+		if err != nil {
+			return nil, err
+		}
+
+		members = append(members, m)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	if members == nil {
+		members = []MemberInfo{}
+	}
+
+	return members, nil
+}
+
 // MessageInfo represents a chat message.
 type MessageInfo struct {
 	ID        int64     `json:"id"`
@@ -155,11 +248,18 @@ type MessageInfo struct {
 	CreatedAt time.Time `json:"createdAt"`
 }
 
-// GetMessages returns messages for a channel, optionally after a given ID.
-func (s *Database) GetMessages(ctx context.Context, channelID int64, afterID int64, limit int) ([]MessageInfo, error) {
+// GetMessages returns messages for a channel, optionally
+// after a given ID.
+func (s *Database) GetMessages(
+	ctx context.Context,
+	channelID int64,
+	afterID int64,
+	limit int,
+) ([]MessageInfo, error) {
 	if limit <= 0 {
-		limit = 50
+		limit = defaultMessageLimit
 	}
+
 	rows, err := s.db.QueryContext(ctx,
 		`SELECT m.id, c.name, u.nick, m.content, m.created_at
 		 FROM messages m
@@ -170,128 +270,288 @@ func (s *Database) GetMessages(ctx context.Context, channelID int64, afterID int
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+
+	defer func() { _ = rows.Close() }()
+
 	var msgs []MessageInfo
+
 	for rows.Next() {
 		var m MessageInfo
-		if err := rows.Scan(&m.ID, &m.Channel, &m.Nick, &m.Content, &m.CreatedAt); err != nil {
+
+		err := rows.Scan(
+			&m.ID, &m.Channel, &m.Nick,
+			&m.Content, &m.CreatedAt,
+		)
+		if err != nil {
 			return nil, err
 		}
+
 		msgs = append(msgs, m)
 	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
 	if msgs == nil {
 		msgs = []MessageInfo{}
 	}
+
 	return msgs, nil
 }
 
 // SendMessage inserts a channel message.
-func (s *Database) SendMessage(ctx context.Context, channelID, userID int64, content string) (int64, error) {
+func (s *Database) SendMessage(
+	ctx context.Context,
+	channelID, userID int64,
+	content string,
+) (int64, error) {
 	res, err := s.db.ExecContext(ctx,
 		"INSERT INTO messages (channel_id, user_id, content, is_dm, created_at) VALUES (?, ?, ?, 0, ?)",
 		channelID, userID, content, time.Now())
 	if err != nil {
 		return 0, err
 	}
+
 	return res.LastInsertId()
 }
 
 // SendDM inserts a direct message.
-func (s *Database) SendDM(ctx context.Context, fromID, toID int64, content string) (int64, error) {
+func (s *Database) SendDM(
+	ctx context.Context,
+	fromID, toID int64,
+	content string,
+) (int64, error) {
 	res, err := s.db.ExecContext(ctx,
 		"INSERT INTO messages (user_id, content, is_dm, dm_target_id, created_at) VALUES (?, ?, 1, ?, ?)",
 		fromID, content, toID, time.Now())
 	if err != nil {
 		return 0, err
 	}
+
 	return res.LastInsertId()
 }
 
-// GetDMs returns direct messages between two users after a given ID.
-func (s *Database) GetDMs(ctx context.Context, userA, userB int64, afterID int64, limit int) ([]MessageInfo, error) {
+// GetDMs returns direct messages between two users after a
+// given ID.
+func (s *Database) GetDMs(
+	ctx context.Context,
+	userA, userB int64,
+	afterID int64,
+	limit int,
+) ([]MessageInfo, error) {
 	if limit <= 0 {
-		limit = 50
+		limit = defaultMessageLimit
 	}
+
 	rows, err := s.db.QueryContext(ctx,
 		`SELECT m.id, u.nick, m.content, t.nick, m.created_at
 		 FROM messages m
 		 INNER JOIN users u ON u.id = m.user_id
 		 INNER JOIN users t ON t.id = m.dm_target_id
 		 WHERE m.is_dm = 1 AND m.id > ?
-		 AND ((m.user_id = ? AND m.dm_target_id = ?) OR (m.user_id = ? AND m.dm_target_id = ?))
-		 ORDER BY m.id ASC LIMIT ?`, afterID, userA, userB, userB, userA, limit)
+		 AND ((m.user_id = ? AND m.dm_target_id = ?)
+		   OR (m.user_id = ? AND m.dm_target_id = ?))
+		 ORDER BY m.id ASC LIMIT ?`,
+		afterID, userA, userB, userB, userA, limit)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+
+	defer func() { _ = rows.Close() }()
+
 	var msgs []MessageInfo
+
 	for rows.Next() {
 		var m MessageInfo
-		if err := rows.Scan(&m.ID, &m.Nick, &m.Content, &m.DMTarget, &m.CreatedAt); err != nil {
+
+		err := rows.Scan(
+			&m.ID, &m.Nick, &m.Content,
+			&m.DMTarget, &m.CreatedAt,
+		)
+		if err != nil {
 			return nil, err
 		}
+
 		m.IsDM = true
+
 		msgs = append(msgs, m)
 	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
 	if msgs == nil {
 		msgs = []MessageInfo{}
 	}
+
 	return msgs, nil
 }
 
-// PollMessages returns all new messages (channel + DM) for a user after a given ID.
-func (s *Database) PollMessages(ctx context.Context, userID int64, afterID int64, limit int) ([]MessageInfo, error) {
+// PollMessages returns all new messages (channel + DM) for
+// a user after a given ID.
+func (s *Database) PollMessages(
+	ctx context.Context,
+	userID int64,
+	afterID int64,
+	limit int,
+) ([]MessageInfo, error) {
 	if limit <= 0 {
-		limit = 100
+		limit = defaultPollLimit
 	}
+
 	rows, err := s.db.QueryContext(ctx,
-		`SELECT m.id, COALESCE(c.name, ''), u.nick, m.content, m.is_dm, COALESCE(t.nick, ''), m.created_at
+		`SELECT m.id, COALESCE(c.name, ''), u.nick, m.content,
+		        m.is_dm, COALESCE(t.nick, ''), m.created_at
 		 FROM messages m
 		 INNER JOIN users u ON u.id = m.user_id
 		 LEFT JOIN channels c ON c.id = m.channel_id
 		 LEFT JOIN users t ON t.id = m.dm_target_id
 		 WHERE m.id > ? AND (
-		   (m.is_dm = 0 AND m.channel_id IN (SELECT channel_id FROM channel_members WHERE user_id = ?))
-		   OR (m.is_dm = 1 AND (m.user_id = ? OR m.dm_target_id = ?))
+		   (m.is_dm = 0 AND m.channel_id IN
+		     (SELECT channel_id FROM channel_members
+		      WHERE user_id = ?))
+		   OR (m.is_dm = 1
+		     AND (m.user_id = ? OR m.dm_target_id = ?))
 		 )
-		 ORDER BY m.id ASC LIMIT ?`, afterID, userID, userID, userID, limit)
+		 ORDER BY m.id ASC LIMIT ?`,
+		afterID, userID, userID, userID, limit)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-	var msgs []MessageInfo
+
+	defer func() { _ = rows.Close() }()
+
+	msgs := make([]MessageInfo, 0)
+
 	for rows.Next() {
-		var m MessageInfo
-		var isDM int
-		if err := rows.Scan(&m.ID, &m.Channel, &m.Nick, &m.Content, &isDM, &m.DMTarget, &m.CreatedAt); err != nil {
+		var (
+			m    MessageInfo
+			isDM int
+		)
+
+		err := rows.Scan(
+			&m.ID, &m.Channel, &m.Nick, &m.Content,
+			&isDM, &m.DMTarget, &m.CreatedAt,
+		)
+		if err != nil {
 			return nil, err
 		}
+
 		m.IsDM = isDM == 1
 		msgs = append(msgs, m)
 	}
-	if msgs == nil {
-		msgs = []MessageInfo{}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
 	}
+
 	return msgs, nil
 }
 
-// GetMessagesBefore returns channel messages before a given ID (for history scrollback).
-func (s *Database) GetMessagesBefore(ctx context.Context, channelID int64, beforeID int64, limit int) ([]MessageInfo, error) {
-	if limit <= 0 {
-		limit = 50
+func scanChannelMessages(
+	rows *sql.Rows,
+) ([]MessageInfo, error) {
+	var msgs []MessageInfo
+
+	for rows.Next() {
+		var m MessageInfo
+
+		err := rows.Scan(
+			&m.ID, &m.Channel, &m.Nick,
+			&m.Content, &m.CreatedAt,
+		)
+		if err != nil {
+			return nil, err
+		}
+
+		msgs = append(msgs, m)
 	}
+
+	err := rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	if msgs == nil {
+		msgs = []MessageInfo{}
+	}
+
+	return msgs, nil
+}
+
+func scanDMMessages(
+	rows *sql.Rows,
+) ([]MessageInfo, error) {
+	var msgs []MessageInfo
+
+	for rows.Next() {
+		var m MessageInfo
+
+		err := rows.Scan(
+			&m.ID, &m.Nick, &m.Content,
+			&m.DMTarget, &m.CreatedAt,
+		)
+		if err != nil {
+			return nil, err
+		}
+
+		m.IsDM = true
+
+		msgs = append(msgs, m)
+	}
+
+	err := rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	if msgs == nil {
+		msgs = []MessageInfo{}
+	}
+
+	return msgs, nil
+}
+
+func reverseMessages(msgs []MessageInfo) {
+	for i, j := 0, len(msgs)-1; i < j; i, j = i+1, j-1 {
+		msgs[i], msgs[j] = msgs[j], msgs[i]
+	}
+}
+
+// GetMessagesBefore returns channel messages before a given
+// ID (for history scrollback).
+func (s *Database) GetMessagesBefore(
+	ctx context.Context,
+	channelID int64,
+	beforeID int64,
+	limit int,
+) ([]MessageInfo, error) {
+	if limit <= 0 {
+		limit = defaultMessageLimit
+	}
+
 	var query string
+
 	var args []any
+
 	if beforeID > 0 {
-		query = `SELECT m.id, c.name, u.nick, m.content, m.created_at
+		query = `SELECT m.id, c.name, u.nick, m.content,
+		                m.created_at
 			FROM messages m
 			INNER JOIN users u ON u.id = m.user_id
 			INNER JOIN channels c ON c.id = m.channel_id
-			WHERE m.channel_id = ? AND m.is_dm = 0 AND m.id < ?
+			WHERE m.channel_id = ? AND m.is_dm = 0
+			  AND m.id < ?
 			ORDER BY m.id DESC LIMIT ?`
 		args = []any{channelID, beforeID, limit}
 	} else {
-		query = `SELECT m.id, c.name, u.nick, m.content, m.created_at
+		query = `SELECT m.id, c.name, u.nick, m.content,
+		                m.created_at
 			FROM messages m
 			INNER JOIN users u ON u.id = m.user_id
 			INNER JOIN channels c ON c.id = m.channel_id
@@ -299,116 +559,153 @@ func (s *Database) GetMessagesBefore(ctx context.Context, channelID int64, befor
 			ORDER BY m.id DESC LIMIT ?`
 		args = []any{channelID, limit}
 	}
+
 	rows, err := s.db.QueryContext(ctx, query, args...)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-	var msgs []MessageInfo
-	for rows.Next() {
-		var m MessageInfo
-		if err := rows.Scan(&m.ID, &m.Channel, &m.Nick, &m.Content, &m.CreatedAt); err != nil {
-			return nil, err
-		}
-		msgs = append(msgs, m)
-	}
-	if msgs == nil {
-		msgs = []MessageInfo{}
-	}
-	// Reverse to ascending order
-	for i, j := 0, len(msgs)-1; i < j; i, j = i+1, j-1 {
-		msgs[i], msgs[j] = msgs[j], msgs[i]
+
+	defer func() { _ = rows.Close() }()
+
+	msgs, scanErr := scanChannelMessages(rows)
+	if scanErr != nil {
+		return nil, scanErr
 	}
+
+	// Reverse to ascending order.
+	reverseMessages(msgs)
+
 	return msgs, nil
 }
 
-// GetDMsBefore returns DMs between two users before a given ID (for history scrollback).
-func (s *Database) GetDMsBefore(ctx context.Context, userA, userB int64, beforeID int64, limit int) ([]MessageInfo, error) {
+// GetDMsBefore returns DMs between two users before a given
+// ID (for history scrollback).
+func (s *Database) GetDMsBefore(
+	ctx context.Context,
+	userA, userB int64,
+	beforeID int64,
+	limit int,
+) ([]MessageInfo, error) {
 	if limit <= 0 {
-		limit = 50
+		limit = defaultMessageLimit
 	}
+
 	var query string
+
 	var args []any
+
 	if beforeID > 0 {
-		query = `SELECT m.id, u.nick, m.content, t.nick, m.created_at
+		query = `SELECT m.id, u.nick, m.content, t.nick,
+		                m.created_at
 			FROM messages m
 			INNER JOIN users u ON u.id = m.user_id
 			INNER JOIN users t ON t.id = m.dm_target_id
 			WHERE m.is_dm = 1 AND m.id < ?
-			AND ((m.user_id = ? AND m.dm_target_id = ?) OR (m.user_id = ? AND m.dm_target_id = ?))
+			AND ((m.user_id = ? AND m.dm_target_id = ?)
+			  OR (m.user_id = ? AND m.dm_target_id = ?))
 			ORDER BY m.id DESC LIMIT ?`
-		args = []any{beforeID, userA, userB, userB, userA, limit}
+		args = []any{
+			beforeID, userA, userB, userB, userA, limit,
+		}
 	} else {
-		query = `SELECT m.id, u.nick, m.content, t.nick, m.created_at
+		query = `SELECT m.id, u.nick, m.content, t.nick,
+		                m.created_at
 			FROM messages m
 			INNER JOIN users u ON u.id = m.user_id
 			INNER JOIN users t ON t.id = m.dm_target_id
 			WHERE m.is_dm = 1
-			AND ((m.user_id = ? AND m.dm_target_id = ?) OR (m.user_id = ? AND m.dm_target_id = ?))
+			AND ((m.user_id = ? AND m.dm_target_id = ?)
+			  OR (m.user_id = ? AND m.dm_target_id = ?))
 			ORDER BY m.id DESC LIMIT ?`
 		args = []any{userA, userB, userB, userA, limit}
 	}
+
 	rows, err := s.db.QueryContext(ctx, query, args...)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-	var msgs []MessageInfo
-	for rows.Next() {
-		var m MessageInfo
-		if err := rows.Scan(&m.ID, &m.Nick, &m.Content, &m.DMTarget, &m.CreatedAt); err != nil {
-			return nil, err
-		}
-		m.IsDM = true
-		msgs = append(msgs, m)
-	}
-	if msgs == nil {
-		msgs = []MessageInfo{}
-	}
-	// Reverse to ascending order
-	for i, j := 0, len(msgs)-1; i < j; i, j = i+1, j-1 {
-		msgs[i], msgs[j] = msgs[j], msgs[i]
+
+	defer func() { _ = rows.Close() }()
+
+	msgs, scanErr := scanDMMessages(rows)
+	if scanErr != nil {
+		return nil, scanErr
 	}
+
+	// Reverse to ascending order.
+	reverseMessages(msgs)
+
 	return msgs, nil
 }
 
 // ChangeNick updates a user's nickname.
-func (s *Database) ChangeNick(ctx context.Context, userID int64, newNick string) error {
+func (s *Database) ChangeNick(
+	ctx context.Context,
+	userID int64,
+	newNick string,
+) error {
 	_, err := s.db.ExecContext(ctx,
-		"UPDATE users SET nick = ? WHERE id = ?", newNick, userID)
+		"UPDATE users SET nick = ? WHERE id = ?",
+		newNick, userID)
+
 	return err
 }
 
 // SetTopic sets the topic for a channel.
-func (s *Database) SetTopic(ctx context.Context, channelName string, _ int64, topic string) error {
+func (s *Database) SetTopic(
+	ctx context.Context,
+	channelName string,
+	_ int64,
+	topic string,
+) error {
 	_, err := s.db.ExecContext(ctx,
-		"UPDATE channels SET topic = ? WHERE name = ?", topic, channelName)
+		"UPDATE channels SET topic = ? WHERE name = ?",
+		topic, channelName)
+
 	return err
 }
 
-// GetServerName returns the server name (unused, config provides this).
+// GetServerName returns the server name (unused, config
+// provides this).
 func (s *Database) GetServerName() string {
 	return ""
 }
 
 // ListAllChannels returns all channels.
-func (s *Database) ListAllChannels(ctx context.Context) ([]ChannelInfo, error) {
+func (s *Database) ListAllChannels(
+	ctx context.Context,
+) ([]ChannelInfo, error) {
 	rows, err := s.db.QueryContext(ctx,
 		"SELECT id, name, topic FROM channels ORDER BY name")
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+
+	defer func() { _ = rows.Close() }()
+
 	var channels []ChannelInfo
+
 	for rows.Next() {
 		var ch ChannelInfo
-		if err := rows.Scan(&ch.ID, &ch.Name, &ch.Topic); err != nil {
+
+		err := rows.Scan(
+			&ch.ID, &ch.Name, &ch.Topic,
+		)
+		if err != nil {
 			return nil, err
 		}
+
 		channels = append(channels, ch)
 	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, err
+	}
+
 	if channels == nil {
 		channels = []ChannelInfo{}
 	}
+
 	return channels, nil
 }

internal/models/auth_token.go

@@ -2,7 +2,6 @@ package models
 
 import (
 	"context"
-	"fmt"
 	"time"
 )
 
@@ -23,5 +22,5 @@ func (t *AuthToken) User(ctx context.Context) (*User, error) {
 		return ul.GetUserByID(ctx, t.UserID)
 	}
 
-	return nil, fmt.Errorf("user lookup not available")
+	return nil, ErrUserLookupNotAvailable
 }

internal/models/channel_member.go

@@ -2,7 +2,6 @@ package models
 
 import (
 	"context"
-	"fmt"
 	"time"
 )
 
@@ -23,7 +22,7 @@ func (cm *ChannelMember) User(ctx context.Context) (*User, error) {
 		return ul.GetUserByID(ctx, cm.UserID)
 	}
 
-	return nil, fmt.Errorf("user lookup not available")
+	return nil, ErrUserLookupNotAvailable
 }
 
 // Channel returns the full Channel for this membership.
@@ -32,5 +31,5 @@ func (cm *ChannelMember) Channel(ctx context.Context) (*Channel, error) {
 		return cl.GetChannelByID(ctx, cm.ChannelID)
 	}
 
-	return nil, fmt.Errorf("channel lookup not available")
+	return nil, ErrChannelLookupNotAvailable
 }

internal/models/model.go

@@ -6,6 +6,7 @@ package models
 import (
 	"context"
 	"database/sql"
+	"errors"
 )
 
 // DB is the interface that models use to query the database.
@@ -24,6 +25,12 @@ type ChannelLookup interface {
 	GetChannelByID(ctx context.Context, id string) (*Channel, error)
 }
 
+// Sentinel errors for model lookup methods.
+var (
+	ErrUserLookupNotAvailable    = errors.New("user lookup not available")
+	ErrChannelLookupNotAvailable = errors.New("channel lookup not available")
+)
+
 // Base is embedded in all model structs to provide database access.
 type Base struct {
 	db DB
@@ -40,7 +47,7 @@ func (b *Base) GetDB() *sql.DB {
 }
 
 // GetUserLookup returns the DB as a UserLookup if it implements the interface.
-func (b *Base) GetUserLookup() UserLookup {
+func (b *Base) GetUserLookup() UserLookup { //nolint:ireturn // interface return is intentional
 	if ul, ok := b.db.(UserLookup); ok {
 		return ul
 	}
@@ -49,7 +56,7 @@ func (b *Base) GetUserLookup() UserLookup {
 }
 
 // GetChannelLookup returns the DB as a ChannelLookup if it implements the interface.
-func (b *Base) GetChannelLookup() ChannelLookup {
+func (b *Base) GetChannelLookup() ChannelLookup { //nolint:ireturn // interface return is intentional
 	if cl, ok := b.db.(ChannelLookup); ok {
 		return cl
 	}

internal/models/session.go

@@ -2,7 +2,6 @@ package models
 
 import (
 	"context"
-	"fmt"
 	"time"
 )
 
@@ -23,5 +22,5 @@ func (s *Session) User(ctx context.Context) (*User, error) {
 		return ul.GetUserByID(ctx, s.UserID)
 	}
 
-	return nil, fmt.Errorf("user lookup not available")
+	return nil, ErrUserLookupNotAvailable
 }

internal/server/routes.go

@@ -71,17 +71,37 @@ func (s *Server) SetupRoutes() {
 		s.log.Error("failed to get web dist filesystem", "error", err)
 	} else {
 		fileServer := http.FileServer(http.FS(distFS))
+
 		s.router.Get("/*", func(w http.ResponseWriter, r *http.Request) {
-			// Try to serve the file; if not found, serve index.html for SPA routing
-			f, err := distFS.(fs.ReadFileFS).ReadFile(r.URL.Path[1:])
-			if err != nil || len(f) == 0 {
-				indexHTML, _ := distFS.(fs.ReadFileFS).ReadFile("index.html")
-				w.Header().Set("Content-Type", "text/html; charset=utf-8")
-				w.WriteHeader(http.StatusOK)
-				_, _ = w.Write(indexHTML)
-				return
-			}
-			fileServer.ServeHTTP(w, r)
+			s.serveSPA(distFS, fileServer, w, r)
 		})
 	}
 }
+
+func (s *Server) serveSPA(
+	distFS fs.FS,
+	fileServer http.Handler,
+	w http.ResponseWriter,
+	r *http.Request,
+) {
+	readFS, ok := distFS.(fs.ReadFileFS)
+	if !ok {
+		http.Error(w, "filesystem error", http.StatusInternalServerError)
+
+		return
+	}
+
+	// Try to serve the file; fall back to index.html for SPA routing.
+	f, err := readFS.ReadFile(r.URL.Path[1:])
+	if err != nil || len(f) == 0 {
+		indexHTML, _ := readFS.ReadFile("index.html")
+
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write(indexHTML)
+
+		return
+	}
+
+	fileServer.ServeHTTP(w, r)
+}