package app

import (
	"context"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"database/sql"
	"encoding/base64"
	"encoding/json"
	"encoding/pem"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"golang.org/x/crypto/bcrypt"
	_ "modernc.org/sqlite"
)

type App struct {
	cfg          Config
	db           *sql.DB
	log          *slog.Logger
	now          func() time.Time
	policy       *HTMLPolicy
	workerCancel context.CancelFunc
}

func New(cfg Config, logger *slog.Logger) (*App, error) {
	if logger == nil {
		logger = slog.Default()
	}
	if err := os.MkdirAll(filepath.Dir(cfg.DBPath), 0o755); err != nil {
		return nil, fmt.Errorf("create db dir: %w", err)
	}
	if err := os.MkdirAll(filepath.Join(cfg.DataDir, "attachments"), 0o755); err != nil {
		return nil, fmt.Errorf("create data dir: %w", err)
	}

	db, err := sql.Open("sqlite", cfg.DBPath)
	if err != nil {
		return nil, err
	}
	db.SetMaxOpenConns(1)

	a := &App{cfg: cfg, db: db, log: logger, now: time.Now, policy: NewHTMLPolicy()}
	if err := a.configureSQLite(context.Background()); err != nil {
		db.Close()
		return nil, err
	}
	if err := a.migrate(context.Background()); err != nil {
		db.Close()
		return nil, err
	}
	if err := a.ensureDefaultMailTemplates(context.Background()); err != nil {
		db.Close()
		return nil, err
	}
	if err := a.loadPersistedSystemSettings(context.Background()); err != nil {
		db.Close()
		return nil, err
	}
	if err := a.seed(context.Background()); err != nil {
		db.Close()
		return nil, err
	}
	if strings.TrimSpace(cfg.MaildirRoot) != "" {
		workerCtx, cancel := context.WithCancel(context.Background())
		a.workerCancel = cancel
		go a.maildirWorker(workerCtx)
	}
	return a, nil
}

func (a *App) Close() error {
	if a == nil || a.db == nil {
		return nil
	}
	if a.workerCancel != nil {
		a.workerCancel()
	}
	return a.db.Close()
}

func (a *App) configureSQLite(ctx context.Context) error {
	pragmas := []string{
		"PRAGMA foreign_keys = ON",
		"PRAGMA journal_mode = WAL",
		"PRAGMA busy_timeout = 5000",
	}
	for _, q := range pragmas {
		if _, err := a.db.ExecContext(ctx, q); err != nil {
			return err
		}
	}
	return nil
}

func (a *App) migrate(ctx context.Context) error {
	stmts := []string{
		`CREATE TABLE IF NOT EXISTS users (
			id TEXT PRIMARY KEY,
			email TEXT NOT NULL UNIQUE,
			display_name TEXT NOT NULL,
			role TEXT NOT NULL CHECK(role IN ('admin','user')),
			password_hash TEXT NOT NULL,
			two_factor_secret TEXT NOT NULL DEFAULT '',
			two_factor_enabled INTEGER NOT NULL DEFAULT 0,
			disabled INTEGER NOT NULL DEFAULT 0,
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS sessions (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			token_hash TEXT NOT NULL UNIQUE,
			expires_at TEXT NOT NULL,
			created_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS login_challenges (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			token_hash TEXT NOT NULL UNIQUE,
			expires_at TEXT NOT NULL,
			created_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS system_settings (
			key TEXT PRIMARY KEY,
			value TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS mail_templates (
			key TEXT PRIMARY KEY,
			name TEXT NOT NULL,
			subject TEXT NOT NULL,
			body_text TEXT NOT NULL,
			body_html TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS domains (
			id TEXT PRIMARY KEY,
			name TEXT NOT NULL UNIQUE,
			status TEXT NOT NULL DEFAULT 'active',
			dkim_selector TEXT NOT NULL,
			dkim_public_key TEXT NOT NULL,
			dkim_private_key TEXT NOT NULL,
			dns_status TEXT NOT NULL DEFAULT 'unchecked',
			dns_checked_at TEXT,
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS mailboxes (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			domain_id TEXT NOT NULL REFERENCES domains(id) ON DELETE CASCADE,
			local_part TEXT NOT NULL,
			address TEXT NOT NULL UNIQUE,
			display_name TEXT NOT NULL,
			password_hash TEXT NOT NULL,
			quota_mb INTEGER NOT NULL DEFAULT 1024,
			status TEXT NOT NULL DEFAULT 'active',
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL,
			UNIQUE(domain_id, local_part)
		)`,
		`CREATE TABLE IF NOT EXISTS aliases (
			id TEXT PRIMARY KEY,
			domain_id TEXT NOT NULL REFERENCES domains(id) ON DELETE CASCADE,
			source TEXT NOT NULL UNIQUE,
			destination TEXT NOT NULL,
			enabled INTEGER NOT NULL DEFAULT 1,
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS folders (
			id TEXT PRIMARY KEY,
			mailbox_id TEXT NOT NULL REFERENCES mailboxes(id) ON DELETE CASCADE,
			name TEXT NOT NULL,
			role TEXT NOT NULL,
			created_at TEXT NOT NULL,
			UNIQUE(mailbox_id, name)
		)`,
		`CREATE TABLE IF NOT EXISTS messages (
			id TEXT PRIMARY KEY,
			mailbox_id TEXT REFERENCES mailboxes(id) ON DELETE CASCADE,
			folder_id TEXT REFERENCES folders(id) ON DELETE CASCADE,
			recipient_addr TEXT NOT NULL DEFAULT '',
			message_uid TEXT NOT NULL,
			message_id TEXT NOT NULL,
			subject TEXT NOT NULL,
			from_addr TEXT NOT NULL,
			to_addrs TEXT NOT NULL,
			cc_addrs TEXT NOT NULL DEFAULT '[]',
			bcc_addrs TEXT NOT NULL DEFAULT '[]',
			sent_at TEXT NOT NULL,
			received_at TEXT NOT NULL,
			snippet TEXT NOT NULL,
			body_text TEXT NOT NULL,
			body_html TEXT NOT NULL,
			is_read INTEGER NOT NULL DEFAULT 0,
			is_starred INTEGER NOT NULL DEFAULT 0,
			has_attachments INTEGER NOT NULL DEFAULT 0,
			size_bytes INTEGER NOT NULL DEFAULT 0,
			raw_path TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE INDEX IF NOT EXISTS idx_messages_mailbox_folder_received ON messages(mailbox_id, folder_id, received_at DESC)`,
		`CREATE INDEX IF NOT EXISTS idx_messages_search ON messages(mailbox_id, subject, from_addr, snippet)`,
		`CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_mailbox_raw_path ON messages(mailbox_id, raw_path) WHERE raw_path <> '' AND mailbox_id IS NOT NULL`,
		`CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_unregistered_raw_path ON messages(raw_path) WHERE raw_path <> '' AND mailbox_id IS NULL`,
		`CREATE TABLE IF NOT EXISTS attachments (
			id TEXT PRIMARY KEY,
			message_id TEXT NOT NULL REFERENCES messages(id) ON DELETE CASCADE,
			filename TEXT NOT NULL,
			content_type TEXT NOT NULL,
			size_bytes INTEGER NOT NULL,
			storage_path TEXT NOT NULL,
			created_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS contacts (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			name TEXT NOT NULL,
			email TEXT NOT NULL,
			note TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL,
			UNIQUE(user_id, email)
		)`,
		`CREATE TABLE IF NOT EXISTS mail_signatures (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			mailbox_id TEXT NOT NULL DEFAULT '',
			name TEXT NOT NULL,
			content TEXT NOT NULL,
			is_default INTEGER NOT NULL DEFAULT 0,
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS mail_rules (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			mailbox_id TEXT NOT NULL DEFAULT '',
			name TEXT NOT NULL,
			match_mode TEXT NOT NULL DEFAULT 'all',
			conditions_json TEXT NOT NULL DEFAULT '[]',
			actions_json TEXT NOT NULL DEFAULT '[]',
			from_contains TEXT NOT NULL DEFAULT '',
			subject_contains TEXT NOT NULL DEFAULT '',
			action TEXT NOT NULL,
			apply_to_existing INTEGER NOT NULL DEFAULT 0,
			stop_processing INTEGER NOT NULL DEFAULT 0,
			enabled INTEGER NOT NULL DEFAULT 1,
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL
		)`,
		`CREATE TABLE IF NOT EXISTS blocked_senders (
			id TEXT PRIMARY KEY,
			user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
			mailbox_id TEXT NOT NULL DEFAULT '',
			email TEXT NOT NULL,
			reason TEXT NOT NULL DEFAULT '',
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL,
			UNIQUE(user_id, mailbox_id, email)
		)`,
		`CREATE TABLE IF NOT EXISTS mail_labels (
			id TEXT PRIMARY KEY,
			mailbox_id TEXT NOT NULL REFERENCES mailboxes(id) ON DELETE CASCADE,
			name TEXT NOT NULL,
			color TEXT NOT NULL DEFAULT '#64748b',
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL,
			UNIQUE(mailbox_id, name)
		)`,
		`CREATE TABLE IF NOT EXISTS message_labels (
			message_id TEXT NOT NULL REFERENCES messages(id) ON DELETE CASCADE,
			label_id TEXT NOT NULL REFERENCES mail_labels(id) ON DELETE CASCADE,
			created_at TEXT NOT NULL,
			PRIMARY KEY(message_id, label_id)
		)`,
		`CREATE INDEX IF NOT EXISTS idx_contacts_user ON contacts(user_id, email)`,
		`CREATE INDEX IF NOT EXISTS idx_mail_signatures_user_mailbox ON mail_signatures(user_id, mailbox_id, is_default)`,
		`CREATE INDEX IF NOT EXISTS idx_mail_rules_user_mailbox ON mail_rules(user_id, mailbox_id, enabled)`,
		`CREATE INDEX IF NOT EXISTS idx_blocked_senders_user_mailbox ON blocked_senders(user_id, mailbox_id, email)`,
		`CREATE INDEX IF NOT EXISTS idx_mail_labels_mailbox ON mail_labels(mailbox_id, name)`,
		`CREATE INDEX IF NOT EXISTS idx_message_labels_label ON message_labels(label_id, message_id)`,
	}
	for _, stmt := range stmts {
		if _, err := a.db.ExecContext(ctx, stmt); err != nil {
			return err
		}
	}
	if err := a.migrateMessagesForUnregistered(ctx); err != nil {
		return err
	}
	if err := a.migrateUsersForTwoFactor(ctx); err != nil {
		return err
	}
	if err := a.migrateMailRulesBuilder(ctx); err != nil {
		return err
	}
	if err := a.migrateLegacyBootstrapMailbox(ctx); err != nil {
		return err
	}
	return nil
}

// migrateLegacyBootstrapMailbox removes mailboxes created by an older version of seed()
// that implicitly created an admin mailbox with display_name "LanQin Admin".
// Current seed() creates mailboxes with display_name = admin email, so this migration
// has no effect on fresh installs. It only cleans up after upgrades from pre-v1.0 schema.
func (a *App) migrateLegacyBootstrapMailbox(ctx context.Context) error {
	adminEmail := normalizeEmail(a.cfg.AdminEmail)
	if adminEmail == "" || !strings.Contains(adminEmail, "@") {
		return nil
	}
	rows, err := a.db.QueryContext(ctx, `
		SELECT mb.id, mb.domain_id
		FROM mailboxes mb
		JOIN users u ON u.id=mb.user_id
		WHERE mb.address=?
		  AND mb.display_name='LanQin Admin'
		  AND u.email=?
		  AND u.role='admin'`, adminEmail, adminEmail)
	if err != nil {
		return err
	}
	type legacyMailbox struct {
		id       string
		domainID string
	}
	items := []legacyMailbox{}
	for rows.Next() {
		var item legacyMailbox
		if err := rows.Scan(&item.id, &item.domainID); err != nil {
			rows.Close()
			return err
		}
		items = append(items, item)
	}
	if err := rows.Err(); err != nil {
		rows.Close()
		return err
	}
	if err := rows.Close(); err != nil {
		return err
	}
	for _, item := range items {
		messageRows, err := a.db.QueryContext(ctx, `SELECT id FROM messages WHERE mailbox_id=?`, item.id)
		if err != nil {
			return err
		}
		messageIDs := []string{}
		for messageRows.Next() {
			var messageID string
			if err := messageRows.Scan(&messageID); err != nil {
				messageRows.Close()
				return err
			}
			messageIDs = append(messageIDs, messageID)
		}
		if err := messageRows.Err(); err != nil {
			messageRows.Close()
			return err
		}
		if err := messageRows.Close(); err != nil {
			return err
		}
		for _, messageID := range messageIDs {
			a.deleteMessageFiles(ctx, messageID)
		}
		if _, err := a.db.ExecContext(ctx, `DELETE FROM mailboxes WHERE id=?`, item.id); err != nil {
			return err
		}
		if _, err := a.db.ExecContext(ctx, `
			DELETE FROM domains
			WHERE id=?
			  AND NOT EXISTS (SELECT 1 FROM mailboxes WHERE domain_id=domains.id)
			  AND NOT EXISTS (SELECT 1 FROM aliases WHERE domain_id=domains.id)`, item.domainID); err != nil {
			return err
		}
	}
	return nil
}

func (a *App) migrateMailRulesBuilder(ctx context.Context) error {
	rows, err := a.db.QueryContext(ctx, `PRAGMA table_info(mail_rules)`)
	if err != nil {
		return err
	}
	defer rows.Close()
	columns := map[string]bool{}
	for rows.Next() {
		var cid int
		var name, typ string
		var notNull, pk int
		var dflt any
		if err := rows.Scan(&cid, &name, &typ, &notNull, &dflt, &pk); err != nil {
			return err
		}
		columns[name] = true
	}
	alter := []struct {
		name string
		sql  string
	}{
		{"match_mode", `ALTER TABLE mail_rules ADD COLUMN match_mode TEXT NOT NULL DEFAULT 'all'`},
		{"conditions_json", `ALTER TABLE mail_rules ADD COLUMN conditions_json TEXT NOT NULL DEFAULT '[]'`},
		{"actions_json", `ALTER TABLE mail_rules ADD COLUMN actions_json TEXT NOT NULL DEFAULT '[]'`},
		{"apply_to_existing", `ALTER TABLE mail_rules ADD COLUMN apply_to_existing INTEGER NOT NULL DEFAULT 0`},
		{"stop_processing", `ALTER TABLE mail_rules ADD COLUMN stop_processing INTEGER NOT NULL DEFAULT 0`},
	}
	for _, item := range alter {
		if !columns[item.name] {
			if _, err := a.db.ExecContext(ctx, item.sql); err != nil {
				return err
			}
		}
	}
	existing, err := a.db.QueryContext(ctx, `SELECT id,from_contains,subject_contains,action,conditions_json,actions_json FROM mail_rules`)
	if err != nil {
		return err
	}
	defer existing.Close()
	type update struct {
		id         string
		conditions string
		actions    string
	}
	updates := []update{}
	for existing.Next() {
		var id, fromContains, subjectContains, action, conditionsJSON, actionsJSON string
		if err := existing.Scan(&id, &fromContains, &subjectContains, &action, &conditionsJSON, &actionsJSON); err != nil {
			return err
		}
		if conditionsJSON != "" && conditionsJSON != "[]" && actionsJSON != "" && actionsJSON != "[]" {
			continue
		}
		conditions := []MailRuleCondition{}
		if strings.TrimSpace(fromContains) != "" {
			conditions = append(conditions, MailRuleCondition{Field: "from", Operator: "contains", Value: strings.TrimSpace(fromContains)})
		}
		if strings.TrimSpace(subjectContains) != "" {
			conditions = append(conditions, MailRuleCondition{Field: "subject", Operator: "contains", Value: strings.TrimSpace(subjectContains)})
		}
		actions := []MailRuleAction{}
		if strings.TrimSpace(action) != "" {
			actions = append(actions, MailRuleAction{Type: strings.TrimSpace(action)})
		}
		condBytes, err := json.Marshal(conditions)
		if err != nil {
			return err
		}
		actionBytes, err := json.Marshal(actions)
		if err != nil {
			return err
		}
		updates = append(updates, update{id: id, conditions: string(condBytes), actions: string(actionBytes)})
	}
	for _, item := range updates {
		if _, err := a.db.ExecContext(ctx, `UPDATE mail_rules SET conditions_json=?, actions_json=? WHERE id=?`, item.conditions, item.actions, item.id); err != nil {
			return err
		}
	}
	return existing.Err()
}

func (a *App) migrateUsersForTwoFactor(ctx context.Context) error {
	rows, err := a.db.QueryContext(ctx, `PRAGMA table_info(users)`)
	if err != nil {
		return err
	}
	defer rows.Close()
	columns := map[string]bool{}
	for rows.Next() {
		var cid int
		var name, typ string
		var notnull int
		var dflt any
		var pk int
		if err := rows.Scan(&cid, &name, &typ, &notnull, &dflt, &pk); err != nil {
			return err
		}
		columns[name] = true
	}
	if err := rows.Err(); err != nil {
		return err
	}
	if !columns["two_factor_secret"] {
		if _, err := a.db.ExecContext(ctx, `ALTER TABLE users ADD COLUMN two_factor_secret TEXT NOT NULL DEFAULT ''`); err != nil {
			return err
		}
	}
	if !columns["two_factor_enabled"] {
		if _, err := a.db.ExecContext(ctx, `ALTER TABLE users ADD COLUMN two_factor_enabled INTEGER NOT NULL DEFAULT 0`); err != nil {
			return err
		}
	}
	return nil
}

func (a *App) migrateMessagesForUnregistered(ctx context.Context) error {
	rows, err := a.db.QueryContext(ctx, `PRAGMA table_info(messages)`)
	if err != nil {
		return err
	}
	defer rows.Close()
	hasRecipientAddr := false
	mailboxNullable := false
	folderNullable := false
	for rows.Next() {
		var cid int
		var name, typ string
		var notnull int
		var dflt any
		var pk int
		if err := rows.Scan(&cid, &name, &typ, &notnull, &dflt, &pk); err != nil {
			return err
		}
		switch name {
		case "recipient_addr":
			hasRecipientAddr = true
		case "mailbox_id":
			mailboxNullable = notnull == 0
		case "folder_id":
			folderNullable = notnull == 0
		}
	}
	if err := rows.Err(); err != nil {
		return err
	}
	if hasRecipientAddr && mailboxNullable && folderNullable {
		return nil
	}

	if _, err := a.db.ExecContext(ctx, `PRAGMA foreign_keys = OFF`); err != nil {
		return err
	}
	defer a.db.ExecContext(context.Background(), `PRAGMA foreign_keys = ON`)

	tx, err := a.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	for _, stmt := range []string{
		`DROP INDEX IF EXISTS idx_messages_mailbox_folder_received`,
		`DROP INDEX IF EXISTS idx_messages_search`,
		`DROP INDEX IF EXISTS idx_messages_mailbox_raw_path`,
		`DROP INDEX IF EXISTS idx_messages_unregistered_raw_path`,
	} {
		if _, err := tx.ExecContext(ctx, stmt); err != nil {
			return err
		}
	}
	if _, err := tx.ExecContext(ctx, `CREATE TABLE messages_new (
		id TEXT PRIMARY KEY,
		mailbox_id TEXT REFERENCES mailboxes(id) ON DELETE CASCADE,
		folder_id TEXT REFERENCES folders(id) ON DELETE CASCADE,
		recipient_addr TEXT NOT NULL DEFAULT '',
		message_uid TEXT NOT NULL,
		message_id TEXT NOT NULL,
		subject TEXT NOT NULL,
		from_addr TEXT NOT NULL,
		to_addrs TEXT NOT NULL,
		cc_addrs TEXT NOT NULL DEFAULT '[]',
		bcc_addrs TEXT NOT NULL DEFAULT '[]',
		sent_at TEXT NOT NULL,
		received_at TEXT NOT NULL,
		snippet TEXT NOT NULL,
		body_text TEXT NOT NULL,
		body_html TEXT NOT NULL,
		is_read INTEGER NOT NULL DEFAULT 0,
		is_starred INTEGER NOT NULL DEFAULT 0,
		has_attachments INTEGER NOT NULL DEFAULT 0,
		size_bytes INTEGER NOT NULL DEFAULT 0,
		raw_path TEXT NOT NULL DEFAULT '',
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL
	)`); err != nil {
		return err
	}
	if _, err := tx.ExecContext(ctx, `INSERT INTO messages_new(id,mailbox_id,folder_id,recipient_addr,message_uid,message_id,subject,from_addr,to_addrs,cc_addrs,bcc_addrs,sent_at,received_at,snippet,body_text,body_html,is_read,is_starred,has_attachments,size_bytes,raw_path,created_at,updated_at)
		SELECT id,mailbox_id,folder_id,'',message_uid,message_id,subject,from_addr,to_addrs,cc_addrs,bcc_addrs,sent_at,received_at,snippet,body_text,body_html,is_read,is_starred,has_attachments,size_bytes,raw_path,created_at,updated_at FROM messages`); err != nil {
		return err
	}
	if _, err := tx.ExecContext(ctx, `DROP TABLE messages`); err != nil {
		return err
	}
	if _, err := tx.ExecContext(ctx, `ALTER TABLE messages_new RENAME TO messages`); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	for _, stmt := range messageIndexes() {
		if _, err := a.db.ExecContext(ctx, stmt); err != nil {
			return err
		}
	}
	return nil
}

func messageIndexes() []string {
	return []string{
		`CREATE INDEX IF NOT EXISTS idx_messages_mailbox_folder_received ON messages(mailbox_id, folder_id, received_at DESC)`,
		`CREATE INDEX IF NOT EXISTS idx_messages_search ON messages(mailbox_id, subject, from_addr, snippet)`,
		`CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_mailbox_raw_path ON messages(mailbox_id, raw_path) WHERE raw_path <> '' AND mailbox_id IS NOT NULL`,
		`CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_unregistered_raw_path ON messages(raw_path) WHERE raw_path <> '' AND mailbox_id IS NULL`,
	}
}

func (a *App) seed(ctx context.Context) error {
	var count int
	if err := a.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM users`).Scan(&count); err != nil {
		return err
	}
	if count > 0 {
		return nil
	}

	adminPassword := a.cfg.AdminPassword
	if adminPassword == "" {
		buf := make([]byte, 16)
		if _, err := rand.Read(buf); err != nil {
			return err
		}
		adminPassword = base64.RawURLEncoding.EncodeToString(buf)
		a.log.Warn("LANQIN_ADMIN_PASSWORD not set; generated random password", "password", adminPassword)
	}
	passwordHash, err := bcrypt.GenerateFromPassword([]byte(adminPassword), bcrypt.DefaultCost)
	if err != nil {
		return err
	}
	now := a.now().UTC().Format(time.RFC3339Nano)
	userID := newID("usr")
	adminEmail := normalizeEmail(a.cfg.AdminEmail)
	if adminEmail == "" || !strings.Contains(adminEmail, "@") {
		return errors.New("invalid admin email")
	}
	if _, err := a.db.ExecContext(ctx, `INSERT INTO users(id,email,display_name,role,password_hash,disabled,created_at,updated_at)
		VALUES(?,?,?,?,?,?,?,?)`, userID, adminEmail, "LanQin Admin", "admin", string(passwordHash), 0, now, now); err != nil {
		return err
	}
	a.log.Warn("created default administrator; change LANQIN_ADMIN_PASSWORD in production", "email", adminEmail)

	// Create domain from admin email
	parts := strings.SplitN(adminEmail, "@", 2)
	localPart := parts[0]
	domainName := normalizeDomain(parts[1])
	var domainID string
	if err := a.db.QueryRowContext(ctx, `SELECT id FROM domains WHERE name=?`, domainName).Scan(&domainID); err != nil {
		domainID, err = a.createDomainTx(ctx, nil, domainName)
		if err != nil {
			return err
		}
		a.log.Info("created domain for administrator", "domain", domainName)
	} else {
		a.log.Info("domain already exists for administrator", "domain", domainName)
	}

	// Create mailbox for admin
	mailboxID, err := a.createMailboxWithPasswordHash(ctx, userID, domainID, localPart, adminEmail, string(passwordHash), 1024, "active")
	if err != nil {
		return err
	}
	a.log.Info("created mailbox for administrator", "address", adminEmail)

	// Send welcome message
	if err := a.seedWelcomeMessage(ctx, mailboxID); err != nil {
		a.log.Warn("failed to create welcome message", "error", err)
	}
	return nil
}

func (a *App) createDomainTx(ctx context.Context, tx *sql.Tx, name string) (string, error) {
	name = normalizeDomain(name)
	if name == "" || !strings.Contains(name, ".") {
		return "", errors.New("invalid domain")
	}
	selector := "lanqin"
	publicKey, privateKey, err := generateDKIMMaterial()
	if err != nil {
		return "", err
	}
	id := newID("dom")
	now := a.now().UTC().Format(time.RFC3339Nano)
	query := `INSERT INTO domains(id,name,status,dkim_selector,dkim_public_key,dkim_private_key,dns_status,created_at,updated_at)
		VALUES(?,?,?,?,?,?,?,?,?)`
	args := []any{id, name, "active", selector, publicKey, privateKey, "unchecked", now, now}
	if tx != nil {
		_, err = tx.ExecContext(ctx, query, args...)
	} else {
		_, err = a.db.ExecContext(ctx, query, args...)
	}
	if err != nil {
		return "", err
	}
	return id, nil
}

func generateDKIMMaterial() (string, string, error) {
	key, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		return "", "", err
	}
	pubDER, err := x509.MarshalPKIXPublicKey(&key.PublicKey)
	if err != nil {
		return "", "", err
	}
	privDER := x509.MarshalPKCS1PrivateKey(key)
	privPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: privDER})
	return base64.StdEncoding.EncodeToString(pubDER), base64.StdEncoding.EncodeToString(privPEM), nil
}

func defaultFolderDefs() []struct{ name, role string } {
	return []struct{ name, role string }{
		{"Inbox", "inbox"},
		{"Sent", "sent"},
		{"Drafts", "drafts"},
		{"Archive", "archive"},
		{"Spam", "spam"},
		{"Trash", "trash"},
	}
}

func (a *App) createMailbox(ctx context.Context, userID, domainID, localPart, displayName, password string, quotaMB int, status string) (string, error) {
	passwordHash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}
	return a.createMailboxWithPasswordHash(ctx, userID, domainID, localPart, displayName, string(passwordHash), quotaMB, status)
}

func (a *App) createMailboxWithPasswordHash(ctx context.Context, userID, domainID, localPart, displayName, passwordHash string, quotaMB int, status string) (string, error) {
	localPart = normalizeLocalPart(localPart)
	if localPart == "" {
		return "", errors.New("invalid local part")
	}
	if quotaMB <= 0 {
		quotaMB = 1024
	}
	if status == "" {
		status = "active"
	}
	var domain string
	if err := a.db.QueryRowContext(ctx, `SELECT name FROM domains WHERE id=?`, domainID).Scan(&domain); err != nil {
		return "", err
	}
	address := localPart + "@" + domain
	if displayName == "" {
		displayName = address
	}

	tx, err := a.db.BeginTx(ctx, nil)
	if err != nil {
		return "", err
	}
	defer tx.Rollback()

	id := newID("mbx")
	now := a.now().UTC().Format(time.RFC3339Nano)
	_, err = tx.ExecContext(ctx, `INSERT INTO mailboxes(id,user_id,domain_id,local_part,address,display_name,password_hash,quota_mb,status,created_at,updated_at)
		VALUES(?,?,?,?,?,?,?,?,?,?,?)`, id, userID, domainID, localPart, address, displayName, passwordHash, quotaMB, status, now, now)
	if err != nil {
		return "", err
	}
	for _, f := range defaultFolderDefs() {
		_, err = tx.ExecContext(ctx, `INSERT INTO folders(id,mailbox_id,name,role,created_at) VALUES(?,?,?,?,?)`, newID("fld"), id, f.name, f.role, now)
		if err != nil {
			return "", err
		}
	}
	if err := tx.Commit(); err != nil {
		return "", err
	}
	return id, nil
}

func (a *App) seedWelcomeMessage(ctx context.Context, mailboxID string) error {
	folderID, err := a.ensureFolder(ctx, mailboxID, "Inbox")
	if err != nil {
		return err
	}
	now := a.now().UTC()
	subject := "欢迎使用 LanQin Email"
	bodyText := "你的自建邮箱 Webmail 已经初始化完成。请尽快修改默认管理员密码，并配置 MX/SPF/DKIM/DMARC。"
	bodyHTML := "<p>你的自建邮箱 Webmail 已经初始化完成。</p><p>请尽快修改默认管理员密码，并配置 MX/SPF/DKIM/DMARC。</p>"
	if tpl, err := a.mailTemplate(ctx, "welcome"); err == nil {
		rendered := renderMailTemplate(tpl, templateRenderData{
			To:             a.cfg.AdminEmail,
			From:           "system@lanqin.local",
			PublicHostname: a.cfg.PublicHostname,
			PublicBaseURL:  a.cfg.PublicBaseURL,
			Time:           now,
		})
		subject, bodyText, bodyHTML = rendered.Subject, rendered.Text, rendered.HTML
	}
	msg := storedMessage{
		MailboxID:  mailboxID,
		FolderID:   folderID,
		MessageUID: newID("uid"),
		MessageID:  fmt.Sprintf("<%s@lanqin.local>", newID("msg")),
		Subject:    subject,
		From:       "system@lanqin.local",
		To:         []string{a.cfg.AdminEmail},
		SentAt:     now,
		ReceivedAt: now,
		Snippet:    snippetFrom(bodyText, bodyHTML),
		BodyText:   bodyText,
		BodyHTML:   bodyHTML,
		IsRead:     false,
	}
	_, err = a.insertMessage(ctx, msg, nil)
	return err
}