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import { TransformBase, FilterBase } from './transform-base.ts';import { _Transaction, IValue, _Explainer, _ISelection, _SelectExplanation, QueryError, Stats, nil, _IAlias } from '../interfaces-private.ts';import { Evaluator } from '../evaluator.ts';import { Types, RecordCol } from '../datatypes/index.ts';import { ExprRef } from 'https://deno.land/x/pgsql_ast_parser@12.0.1/mod.ts';import { asSingleName, colToStr } from '../utils.ts';import { ColumnNotFound } from '../interfaces.ts';import { RecordType } from '../datatypes/t-record.ts';
export function buildAlias(on: _ISelection, alias?: string): _ISelection {    if (!alias) {        return on as any;    }    if (on instanceof Alias && on.name === alias) {        return on;    }    return new Alias(on, alias);}
export class Alias<T> extends TransformBase<T> implements _IAlias {
    private oldToThis = new Map<IValue, IValue>();    private thisToOld = new Map<IValue, IValue>();    private _columns: IValue<any>[] | null = null;    private asRecord!: IValue;
    get isExecutionWithNoResult(): boolean {        return this.base.isExecutionWithNoResult;    }
    constructor(sel: _ISelection, public name: string) {        super(sel);    }
    *listSelectableIdentities(): Iterable<IValue> {        this.init();        yield* super.listSelectableIdentities();        yield this.asRecord;    }

    rebuild() {        this._columns = null;        this.oldToThis.clear();        this.thisToOld.clear();    }
    selectAlias(alias: string): _IAlias | nil {        if (this.name === alias) {            return this;        }        return null;    }
    listColumns(): Iterable<IValue> {        return this.columns;    }

    get debugId() {        return this.base.debugId;    }
    get columns(): ReadonlyArray<IValue<any>> {        this.init();        return this._columns!;    }    init() {        if (this._columns) {            return;        }        this._columns = this.base.columns.map(x => {            const ret = x.setOrigin(this);            this.oldToThis.set(x, ret);            this.thisToOld.set(ret, x);            return ret;        });
        // how to build a record out of this alias?        this.asRecord = new Evaluator(            RecordType.from(this)            , this.name            , Math.random().toString()            , this._columns            , v => ({ ...v })            , { forceNotConstant: true });    }
    stats(t: _Transaction): Stats | null {        return this.base.stats(t);    }
    enumerate(t: _Transaction): Iterable<T> {        return this.base.enumerate(t);    }
    hasItem(value: T, t: _Transaction): boolean {        return this.base.hasItem(value, t);    }
    getColumn(column: string | ExprRef): IValue;    getColumn(column: string | ExprRef, nullIfNotFound?: boolean): IValue | nil;    getColumn(column: string | ExprRef, nullIfNotFound?: boolean): IValue | nil {        const col = this._getColumn(column);        if (col) {            return col;        }
        if (asSingleName(column) === this.name) {            return this.asRecord;        }
        if (nullIfNotFound) {            return null;        }        throw new ColumnNotFound(colToStr(column));    }
    private _getColumn(column: string | ExprRef): IValue | nil {        if (typeof column !== 'string'            && column.table) {            if (!column.table.schema                && column.table.name !== this.name) {                return null;            }            column = column.name;        }        const got = this.base.getColumn(column, true);        if (!got) {            return got;        }        this.init();        const ret = this.oldToThis.get(got);        if (!ret) {            throw new Error('Corrupted alias');        }        return ret;    }
    explain(e: _Explainer): _SelectExplanation {        // no need to explain an alias... it does nothing.        return this.base.explain(e);        // return {        //     id: e.idFor(this),        //     type: 'alias',        //     alias: this.as,        //     of: this.base.explain(e),        // };    }
    getIndex(...forValue: IValue[]) {        return this.base.getIndex(...forValue.map(v => this.thisToOld.get(v) ?? v));    }
}