@nerdware/ddb-single-table/dist/esm/Expressions/UpdateExpression/generateUpdateExpression.js

A schema-based DynamoDB modeling tool, high-level API, and type-generator built to supercharge single-table designs!⚡

import { isObjectLike, isDate, isBuffer, isArray } from "@nerdware/ts-type-safety-utils";
import { buildAttrPathTokens } from "./buildAttrPathTokens.js";
/**
 * This function uses the provided `itemAttributes` to generate the following `updateItem` args:
 *
 * - `UpdateExpression` (may include `"SET"` and/or `"REMOVE"` clauses)
 * - `ExpressionAttributeNames`
 * - `ExpressionAttributeValues`
 *
 * `UpdateExpression` Clauses:
 * - The `"SET"` clause includes all attributes which are _not_ explicitly `undefined`.
 * - The `"REMOVE"` clause includes all attributes which are explicitly set to `undefined`.
 * - If {@link GenerateUpdateExpressionOpts|nullHandling} is `"REMOVE"` (default), then
 *   attributes with `null` values are added to the `"REMOVE"` clause, otherwise they are
 *   added to the `"SET"` clause.
 */
export const generateUpdateExpression = (itemAttributes, { nullHandling } = {}) => {
    const shouldAddToRemoveClause = nullHandling !== "SET"
        ? (value) => value === undefined || value === null
        : (value) => value === undefined;
    const updateExpressionClauses = { SET: [], REMOVE: [] };
    const ExpressionAttributeNames = {};
    const ExpressionAttributeValues = {};
    const recurse = (value, path) => {
        if (isObjectLike(value)
            && !isDate(value)
            && !isBuffer(value)
            && !(value instanceof Set) //
        ) {
            if (isArray(value)) {
                value.forEach((arrayElement, index) => {
                    recurse(arrayElement, [...path, index]);
                });
            }
            else {
                for (const key of Object.keys(value)) {
                    const keyValue = value[key];
                    recurse(keyValue, [...path, key]);
                }
            }
        }
        else {
            const { namePath, valueToken } = buildAttrPathTokens(path, ExpressionAttributeNames);
            // Derive and append the appropriate UpdateExpression clause
            if (shouldAddToRemoveClause(value)) {
                updateExpressionClauses.REMOVE.push(namePath);
            }
            else {
                updateExpressionClauses.SET.push(`${namePath} = ${valueToken}`);
                ExpressionAttributeValues[valueToken] = value;
            }
        }
    };
    recurse(itemAttributes, []);
    // Combine the clauses into UpdateExpression
    const UpdateExpression = [
        ...(updateExpressionClauses.SET.length > 0
            ? [`SET ${updateExpressionClauses.SET.join(", ")}`]
            : []),
        ...(updateExpressionClauses.REMOVE.length > 0
            ? [`REMOVE ${updateExpressionClauses.REMOVE.join(", ")}`]
            : []),
    ].join(" ");
    return {
        UpdateExpression,
        ExpressionAttributeNames,
        ExpressionAttributeValues,
    };
};