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mingo

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MongoDB query language for in-memory objects

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import { Aggregator } from "../../aggregator"; import { ComputeOptions, computeValue } from "../../core"; import { assert, hashCode, isArray, isString, MingoError, resolve } from "../../util"; import { $mergeObjects } from "../expression"; const $merge = (collection, expr, options) => { const output = isString(expr.into) ? options?.collectionResolver(expr.into) : expr.into; assert( output instanceof Array, `$merge: option 'into' must resolve to an array` ); const onField = expr.on || options.idKey; const getHash = (o) => { const val = isString(onField) ? resolve(o, onField) : onField.map((s) => resolve(o, s)); return hashCode(val, options.hashFunction); }; const hash = {}; for (let i = 0; i < output.length; i++) { const obj = output[i]; const k = getHash(obj); assert( !hash[k], "$merge: 'into' collection must have unique entries for the 'on' field." ); hash[k] = [obj, i]; } const copts = ComputeOptions.init(options); return collection.map((o) => { const k = getHash(o); if (hash[k]) { const [target, i] = hash[k]; const variables = computeValue( target, expr.let || { new: "$$ROOT" }, null, // 'root' is the item from the iteration. copts.update(o) ); if (isArray(expr.whenMatched)) { const aggregator = new Aggregator(expr.whenMatched, { ...options, variables }); output[i] = aggregator.run([target])[0]; } else { switch (expr.whenMatched) { case "replace": output[i] = o; break; case "fail": throw new MingoError( "$merge: failed due to matching as specified by 'whenMatched' option." ); case "keepExisting": break; case "merge": default: output[i] = $mergeObjects( target, [target, o], // 'root' is the item from the iteration. copts.update(o, { variables }) ); break; } } } else { switch (expr.whenNotMatched) { case "discard": break; case "fail": throw new MingoError( "$merge: failed due to matching as specified by 'whenMatched' option." ); case "insert": default: output.push(o); break; } } return o; }); }; export { $merge };