package database

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

// returns true in case of successful deletion
func (db *DB) DeleteState(path string) (bool, error) {
	result, err := db.Exec(`DELETE FROM states WHERE path = ?;`, path)
	if err != nil {
		return false, err
	}
	n, err := result.RowsAffected()
	if err != nil {
		return false, err
	}
	return n == 1, nil
}

func (db *DB) GetState(path string) ([]byte, error) {
	var encryptedData []byte
	err := db.QueryRow(
		`SELECT versions.data
           FROM versions
           JOIN states ON states.id = versions.state_id
           WHERE states.path = ?
           ORDER BY versions.id DESC
           LIMIT 1;`,
		path).Scan(&encryptedData)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return []byte{}, nil
		}
		return nil, err
	}
	if encryptedData == nil {
		return []byte{}, nil
	}
	return db.dataEncryptionKey.DecryptAES256(encryptedData)
}

// returns true in case of id mismatch
func (db *DB) SetState(path string, accountID int, data []byte, lockID string) (bool, error) {
	encryptedData, err := db.dataEncryptionKey.EncryptAES256(data)
	if err != nil {
		return false, err
	}
	ret := false
	return ret, db.WithTransaction(func(tx *sql.Tx) error {
		var (
			stateID  int64
			lockData []byte
		)
		if err = tx.QueryRowContext(db.ctx, `SELECT id, lock->>'ID' FROM states WHERE path = ?;`, path).Scan(&stateID, &lockData); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				var result sql.Result
				result, err = tx.ExecContext(db.ctx, `INSERT INTO states(path) VALUES (?)`, path)
				if err != nil {
					return err
				}
				stateID, err = result.LastInsertId()
				if err != nil {
					return err
				}
			} else {
				return err
			}
		}

		if lockID != "" && slices.Compare([]byte(lockID), lockData) != 0 {
			err = fmt.Errorf("failed to update state, lock ID does not match")
			ret = true
			return err
		}
		_, err = tx.ExecContext(db.ctx,
			`INSERT INTO versions(account_id, state_id, data, lock)
           SELECT :accountID, :stateID, :data, lock
             FROM states
             WHERE states.id = :stateID;`,
			sql.Named("accountID", accountID),
			sql.Named("stateID", stateID),
			sql.Named("data", encryptedData))
		if err != nil {
			return err
		}
		_, err = tx.ExecContext(db.ctx,
			`DELETE FROM versions
           WHERE state_id = (SELECT id
                               FROM states
                               WHERE path = :path)
             AND id < (SELECT MIN(id)
                         FROM(SELECT versions.id
                                FROM versions
                                JOIN states ON states.id = versions.state_id
                                WHERE states.path = :path
                                ORDER BY versions.id DESC
                                LIMIT :limit));`,
			sql.Named("limit", db.versionsHistoryLimit),
			sql.Named("path", path),
		)
		return err
	})
}