package account

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/google/uuid"
)

// UserListItem is the admin user-list projection: a small subset of the account plus
// whether it is a robot (derived from its identities), so the console can label the kind
// without a per-row identity query.
type UserListItem struct {
	ID                uuid.UUID
	DisplayName       string
	PreferredLanguage string
	IsGuest           bool
	IsRobot           bool
	CreatedAt         time.Time
}

// UserFilter narrows the admin user list: Robots selects robot accounts (otherwise the
// non-robot "people"); NameMask and ExternalIDMask are glob masks ('*' = any run, '?' =
// one char) matched case-insensitively against the display name / any identity's external
// id. An empty mask means no filter on that field.
type UserFilter struct {
	Robots         bool
	NameMask       string
	ExternalIDMask string
}

// robotExists is the correlated subquery testing whether account a is a robot.
const robotExists = `EXISTS (SELECT 1 FROM backend.identities i WHERE i.account_id = a.account_id AND i.kind = 'robot')`

// IsRobot reports whether the account is a robot pool member (it carries a robot
// identity). The admin console uses it to label a game's robot seats.
func (s *Store) IsRobot(ctx context.Context, accountID uuid.UUID) (bool, error) {
	var ok bool
	err := s.db.QueryRowContext(ctx,
		`SELECT EXISTS (SELECT 1 FROM backend.identities WHERE account_id = $1 AND kind = 'robot')`,
		accountID).Scan(&ok)
	if err != nil {
		return false, fmt.Errorf("account: is-robot %s: %w", accountID, err)
	}
	return ok, nil
}

// userListWhere builds the shared WHERE clause and its positional args (from $1).
func userListWhere(f UserFilter) (string, []any) {
	args := []any{f.Robots}
	where := robotExists + ` = $1`
	if name := LikePattern(f.NameMask); name != "" {
		args = append(args, name)
		where += fmt.Sprintf(` AND a.display_name ILIKE $%d ESCAPE '\'`, len(args))
	}
	if ext := LikePattern(f.ExternalIDMask); ext != "" {
		args = append(args, ext)
		where += fmt.Sprintf(` AND EXISTS (SELECT 1 FROM backend.identities i WHERE i.account_id = a.account_id AND i.external_id ILIKE $%d ESCAPE '\')`, len(args))
	}
	return where, args
}

// ListUsers returns the filtered admin user list, newest first, paginated.
func (s *Store) ListUsers(ctx context.Context, f UserFilter, limit, offset int) ([]UserListItem, error) {
	where, args := userListWhere(f)
	q := `SELECT a.account_id, a.display_name, a.preferred_language, a.is_guest, a.created_at, ` + robotExists + ` AS is_robot
FROM backend.accounts a WHERE ` + where +
		fmt.Sprintf(` ORDER BY a.created_at DESC LIMIT $%d OFFSET $%d`, len(args)+1, len(args)+2)
	args = append(args, limit, offset)
	rows, err := s.db.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, fmt.Errorf("account: list users: %w", err)
	}
	defer rows.Close()
	var out []UserListItem
	for rows.Next() {
		var it UserListItem
		if err := rows.Scan(&it.ID, &it.DisplayName, &it.PreferredLanguage, &it.IsGuest, &it.CreatedAt, &it.IsRobot); err != nil {
			return nil, fmt.Errorf("account: scan user: %w", err)
		}
		out = append(out, it)
	}
	return out, rows.Err()
}

// CountUsers counts the filtered admin user list, for pagination.
func (s *Store) CountUsers(ctx context.Context, f UserFilter) (int, error) {
	where, args := userListWhere(f)
	var n int
	if err := s.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM backend.accounts a WHERE `+where, args...).Scan(&n); err != nil {
		return 0, fmt.Errorf("account: count users: %w", err)
	}
	return n, nil
}

// LikePattern converts a glob mask ('*' any run, '?' one char) to an ILIKE pattern,
// escaping the SQL wildcards already in the input first. An empty/blank mask returns "".
func LikePattern(mask string) string {
	mask = strings.TrimSpace(mask)
	if mask == "" {
		return ""
	}
	escaped := strings.NewReplacer(`\`, `\\`, `%`, `\%`, `_`, `\_`).Replace(mask)
	escaped = strings.ReplaceAll(escaped, "*", "%")
	return strings.ReplaceAll(escaped, "?", "_")
}