package store

import (
	"database/sql"
	"errors"
	"fmt"

	"git.dcglab.co.uk/steve/emcli/internal/crypto"
)

var ErrAccountNotFound = errors.New("account not found")

// Account is the decrypted, in-memory view of a configured account.
type Account struct {
	ID                  int64
	Name                string
	Mode                string // RO | RW
	IMAPHost            string
	IMAPPort            int
	IMAPSecurity        string // tls | starttls
	SMTPHost            string // nullable for RO accounts
	SMTPPort            int
	SMTPSecurity        string // tls | starttls
	AuthType            string // password | oauth2
	Username            string
	Password            string // decrypted; empty in ListAccounts
	WhitelistInEnabled  bool
	WhitelistOutEnabled bool
	SubjectRegex        string
	ProcessBacklog      bool
}

func (s *Store) AddAccount(a Account) (int64, error) {
	var encPw []byte
	if a.Password != "" {
		b, err := crypto.Seal(s.key, []byte(a.Password))
		if err != nil {
			return 0, err
		}
		encPw = b
	}
	res, err := s.db.Exec(`
		INSERT INTO accounts
		  (name,mode,imap_host,imap_port,imap_security,smtp_host,smtp_port,smtp_security,
		   auth_type,username,
		   enc_password,whitelist_in_enabled,whitelist_out_enabled,subject_regex,process_backlog)
		VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`,
		a.Name, a.Mode, a.IMAPHost, a.IMAPPort, a.IMAPSecurity,
		nullStr(a.SMTPHost), nullInt(a.SMTPPort), nullStr(a.SMTPSecurity),
		a.AuthType, a.Username,
		encPw, b2i(a.WhitelistInEnabled), b2i(a.WhitelistOutEnabled),
		nullStr(a.SubjectRegex), b2i(a.ProcessBacklog))
	if err != nil {
		return 0, fmt.Errorf("insert account: %w", err)
	}
	return res.LastInsertId()
}

func (s *Store) GetAccount(name string) (Account, error) {
	row := s.db.QueryRow(`
		SELECT id,name,mode,imap_host,imap_port,imap_security,smtp_host,smtp_port,smtp_security,
		       auth_type,username,
		       enc_password,whitelist_in_enabled,whitelist_out_enabled,subject_regex,process_backlog
		FROM accounts WHERE name = ?`, name)
	a, encPw, err := scanAccount(row)
	if errors.Is(err, sql.ErrNoRows) {
		return Account{}, ErrAccountNotFound
	}
	if err != nil {
		return Account{}, err
	}
	if len(encPw) > 0 {
		pw, err := crypto.Open(s.key, encPw)
		if err != nil {
			return Account{}, fmt.Errorf("decrypt password (wrong EMCLI_KEY?): %w", err)
		}
		a.Password = string(pw)
	}
	return a, nil
}

func (s *Store) ListAccounts() ([]Account, error) {
	rows, err := s.db.Query(`
		SELECT id,name,mode,imap_host,imap_port,imap_security,smtp_host,smtp_port,smtp_security,
		       auth_type,username,
		       enc_password,whitelist_in_enabled,whitelist_out_enabled,subject_regex,process_backlog
		FROM accounts ORDER BY name`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []Account
	for rows.Next() {
		a, _, err := scanAccount(rows) // secrets discarded
		if err != nil {
			return nil, err
		}
		out = append(out, a)
	}
	return out, rows.Err()
}

// UpdateAccount updates an existing account's mutable fields, matched by Name.
// The password and OAuth secrets are re-encrypted only when a non-empty value is
// supplied; a blank value preserves whatever is already stored. Returns
// ErrAccountNotFound if no account has that name.
func (s *Store) UpdateAccount(a Account) error {
	// Build the SET clause, conditionally including secret columns.
	set := `mode=?, imap_host=?, imap_port=?, imap_security=?,
	        smtp_host=?, smtp_port=?, smtp_security=?,
	        auth_type=?, username=?,
	        whitelist_in_enabled=?, whitelist_out_enabled=?, subject_regex=?, process_backlog=?`
	args := []any{
		a.Mode, a.IMAPHost, a.IMAPPort, a.IMAPSecurity,
		nullStr(a.SMTPHost), nullInt(a.SMTPPort), nullStr(a.SMTPSecurity),
		a.AuthType, a.Username,
		b2i(a.WhitelistInEnabled), b2i(a.WhitelistOutEnabled),
		nullStr(a.SubjectRegex), b2i(a.ProcessBacklog),
	}
	if a.Password != "" {
		enc, err := crypto.Seal(s.key, []byte(a.Password))
		if err != nil {
			return err
		}
		set += ", enc_password=?"
		args = append(args, enc)
	}
	args = append(args, a.Name)
	res, err := s.db.Exec("UPDATE accounts SET "+set+" WHERE name=?", args...)
	if err != nil {
		return fmt.Errorf("update account: %w", err)
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrAccountNotFound
	}
	return nil
}

func (s *Store) DeleteAccount(name string) error {
	res, err := s.db.Exec("DELETE FROM accounts WHERE name = ?", name)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrAccountNotFound
	}
	return nil
}

// scanner is satisfied by *sql.Row and *sql.Rows.
type scanner interface{ Scan(dest ...any) error }

func scanAccount(sc scanner) (Account, []byte, error) {
	var (
		a                       Account
		encPw                   []byte
		subj, smtpHost, smtpSec sql.NullString
		smtpPort                sql.NullInt64
		wlIn, wlOut             int
		backlog                 int
	)
	err := sc.Scan(&a.ID, &a.Name, &a.Mode, &a.IMAPHost, &a.IMAPPort, &a.IMAPSecurity,
		&smtpHost, &smtpPort, &smtpSec,
		&a.AuthType, &a.Username, &encPw, &wlIn, &wlOut, &subj, &backlog)
	if err != nil {
		return Account{}, nil, err
	}
	a.SMTPHost = smtpHost.String
	a.SMTPPort = int(smtpPort.Int64)
	a.SMTPSecurity = smtpSec.String
	a.WhitelistInEnabled = wlIn != 0
	a.WhitelistOutEnabled = wlOut != 0
	a.ProcessBacklog = backlog != 0
	a.SubjectRegex = subj.String
	return a, encPw, nil
}

func b2i(b bool) int {
	if b {
		return 1
	}
	return 0
}

func nullStr(s string) any {
	if s == "" {
		return nil
	}
	return s
}

func nullInt(n int) any {
	if n == 0 {
		return nil
	}
	return n
}