package db

import (
	"crypto/rand"
	"database/sql"
	"encoding/hex"
	"errors"
	"time"

	"github.com/bluesky-social/indigo/atproto/syntax"
)

var (
	ErrInviteNotFound = errors.New("invite code is unknown, spent or expired")
	ErrInviteBanned   = errors.New("invite redeemer is banned")
)

const InviteTTL = 2 * 24 * time.Hour

// minting sweeps the expired codes, so nothing else has to
func (d *DB) MintInvite(createdBy string, now time.Time) (string, time.Time, error) {
	raw := make([]byte, 16)
	if _, err := rand.Read(raw); err != nil {
		return "", time.Time{}, err
	}
	code := hex.EncodeToString(raw)
	expires := now.Add(InviteTTL)

	tx, err := d.Begin()
	if err != nil {
		return "", time.Time{}, err
	}
	defer tx.Rollback()
	if _, err := tx.Exec(`delete from invite_codes where expires_at <= ?`, now.Unix()); err != nil {
		return "", time.Time{}, err
	}
	if _, err := tx.Exec(
		`insert into invite_codes (code, created_by, expires_at) values (?, ?, ?)`,
		code, createdBy, expires.Unix(),
	); err != nil {
		return "", time.Time{}, err
	}
	return code, expires, tx.Commit()
}

// the delete is the spend, so of any number of racing redeems only one sees a row
func (d *DB) RedeemInvite(code string, did syntax.DID, now time.Time) error {
	tx, err := d.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	var banned bool
	if err := tx.QueryRow(`select exists(select 1 from bans where subject_did = ?)`, did).Scan(&banned); err != nil {
		return err
	}
	if banned {
		return ErrInviteBanned
	}
	var spent string
	err = tx.QueryRow(`delete from invite_codes where code = ? and expires_at > ? returning code`, code, now.Unix()).Scan(&spent)
	if errors.Is(err, sql.ErrNoRows) {
		return ErrInviteNotFound
	}
	if err != nil {
		return err
	}
	if err := AddToAllowlist(tx, did); err != nil {
		return err
	}
	return tx.Commit()
}