@uwdata/mosaic-sql/dist/src/ast/case.js

SQL query construction and analysis.

import { CASE, WHEN } from '../constants.js';
import { asNode } from '../util/ast.js';
import { ExprNode, SQLNode } from './node.js';
export class CaseNode extends ExprNode {
    /** The optional base expression. */
    expr;
    /** An array of WHEN/THEN expression nodes. */
    _when;
    /** An ELSE expression. */
    _else;
    /**
     * Instantiate a case node.
     * @param expr An optional base expression, that comes
     *  immediately after the CASE keyword. If specified, this case statement
     *  acts like a switch statement, with WHEN expressions as values to
     *  match against the switch value rather than boolean conditions.
     * @param when An array of WHEN/THEN expression nodes.
     * @param elseExpr An ELSE expression.
     */
    constructor(expr = undefined, when = [], elseExpr = undefined) {
        super(CASE);
        this.expr = expr;
        this._when = when;
        this._else = elseExpr;
    }
    /**
     * Return a new case node with the given conditional added as
     * the last WHEN / THEN pair.
     * @param cond The WHEN condition expression.
     * @param value The THEN value expression.
     */
    when(cond, value) {
        return new CaseNode(this.expr, this._when.concat(new WhenNode(asNode(cond), asNode(value))), this._else);
    }
    /**
     * Return a new case node with the given ELSE expression.
     * @param expr The ELSE expression.
     */
    else(expr) {
        return new CaseNode(this.expr, this._when, asNode(expr));
    }
    /**
     * Generate a SQL query string for this node.
     */
    toString() {
        return 'CASE '
            + (this.expr ? `${this.expr} ` : '')
            + this._when.join(' ')
            + (this._else ? ` ELSE ${this._else}` : '')
            + ' END';
    }
}
export class WhenNode extends SQLNode {
    /** The condition expression. */
    when;
    /** The value expression. */
    then;
    /**
     * Instantiate a case node.
     * @param when The WHEN condition expression.
     * @param then The THEN value expression.
     */
    constructor(when, then) {
        super(WHEN);
        this.when = when;
        this.then = then;
    }
    /**
     * Generate a SQL query string for this node.
     */
    toString() {
        return `WHEN ${this.when} THEN ${this.then}`;
    }
}
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