import {Collection, Iterable} from '../../../util'
import {Connection} from '../../connection/Connection'
import {AbstractBuilder} from '../AbstractBuilder'

/**
 * Base Iterable class that generates the results of a Builder query.
 */
export abstract class AbstractResultIterable<T> extends Iterable<T> {
    protected constructor(
        /** The builder whose results should be iterated */
        public readonly builder: AbstractBuilder<T>,

        /** The connection on which to execute the builder. */
        public readonly connection: Connection,
    ) {
        super()
    }

    /**
     * Get the SQL string for the SELECT query for this iterable.
     */
    public abstract get selectSQL(): string

    /**
     * Get the result at index i.
     * @param i
     */
    public abstract at(i: number): Promise<T | undefined>

    /**
     * Get the results starting at index `start` and ending at index `end`.
     * @param start
     * @param end
     */
    public abstract range(start: number, end: number): Promise<Collection<T>>

    /**
     * Count the number of results of the query.
     */
    public abstract count(): Promise<number>

    /**
     * Return all items resulting from this query.
     */
    public abstract all(): Promise<Collection<T>>

    /**
     * Create a new iterable based on this query.
     */
    public abstract clone(): AbstractResultIterable<T>
}