mingo/esm/operators/pipeline/project.js

MongoDB query language for in-memory objects

import { ComputeOptions, computeValue, OpType } from "../../core/_internal";
import {
  assert,
  ensureArray,
  filterMissing,
  has,
  intersection,
  isArray,
  isBoolean,
  isEmpty,
  isNumber,
  isObject,
  isOperator,
  isString,
  merge,
  normalize,
  removeValue,
  resolve,
  resolveGraph,
  setValue,
  unique
} from "../../util/_internal";
const $project = (collection, expr, options) => {
  if (isEmpty(expr)) return collection;
  checkExpression(expr, options);
  return collection.map(createHandler(expr, ComputeOptions.init(options)));
};
function createHandler(expr, options, isRoot = true) {
  const idKey = options.idKey;
  const expressionKeys = Object.keys(expr);
  const excludedKeys = new Array();
  const includedKeys = new Array();
  const handlers = {};
  const positional = {};
  for (const key of expressionKeys) {
    const subExpr = expr[key];
    if (isNumber(subExpr) || isBoolean(subExpr)) {
      if (subExpr) {
        if (isRoot && key.endsWith(".$")) {
          const condition = options?.local?.condition;
          assert(
            condition,
            "positional operator '.$' couldn't find matching element in the array."
          );
          const field = key.slice(0, -2);
          positional[field] = getPositionalFilter(field, condition, options);
          includedKeys.push(field);
        } else {
          includedKeys.push(key);
        }
      } else {
        excludedKeys.push(key);
      }
    } else if (isArray(subExpr)) {
      handlers[key] = (o) => subExpr.map(
        (v) => computeValue(o, v, null, options.update({ root: o })) ?? null
      );
    } else if (isObject(subExpr)) {
      const subExprKeys = Object.keys(subExpr);
      const operator = subExprKeys.length == 1 ? subExprKeys[0] : "";
      const projectFn = options.context.getOperator(
        OpType.PROJECTION,
        operator
      );
      if (projectFn) {
        const foundSlice = operator === "$slice";
        if (foundSlice && !ensureArray(subExpr[operator]).every(isNumber)) {
          handlers[key] = (o) => computeValue(o, subExpr, key, options.update({ root: o }));
        } else {
          handlers[key] = (o) => projectFn(o, subExpr[operator], key, options.update({ root: o }));
        }
      } else if (isOperator(operator)) {
        handlers[key] = (o) => computeValue(o, subExpr[operator], operator, options);
      } else {
        checkExpression(subExpr, options);
        assert(subExprKeys.length > 0, `Invalid empty sub-projection: ${key}`);
        handlers[key] = (o) => {
          if (isRoot) options.update({ root: o });
          const target = resolve(o, key);
          const fn = createHandler(subExpr, options, false);
          if (isArray(target)) return target.map(fn);
          if (isObject(target)) return fn(target);
          const res = fn(o);
          if (has(o, key)) return res;
          return !isObject(res) || Object.keys(res).length ? res : void 0;
        };
      }
    } else {
      handlers[key] = isString(subExpr) && subExpr[0] === "$" ? (o) => computeValue(o, subExpr, key, options) : (_) => subExpr;
    }
  }
  const handlerKeys = Object.keys(handlers);
  const idKeyExcluded = excludedKeys.includes(idKey);
  const idKeyImplicit = isRoot && !idKeyExcluded && !includedKeys.includes(idKey);
  const opts = {
    preserveMissing: true
  };
  return (o) => {
    const newObj = {};
    for (const k of includedKeys) {
      const pathObj = resolveGraph(o, k, opts) ?? {};
      merge(newObj, pathObj);
      if (has(positional, k)) {
        positional[k](newObj);
      }
    }
    if (includedKeys.length) filterMissing(newObj);
    for (const k of handlerKeys) {
      const value = handlers[k](o);
      if (value === void 0) {
        removeValue(newObj, k, { descendArray: true });
      } else {
        setValue(newObj, k, value);
      }
    }
    if (excludedKeys.length === 1 && idKeyExcluded) {
      if (Object.keys(newObj).length === 0) Object.assign(newObj, o);
    } else if (excludedKeys.length) {
      Object.assign(newObj, { ...o, ...newObj });
    }
    for (const k of excludedKeys) {
      removeValue(newObj, k, { descendArray: true });
    }
    if (idKeyImplicit && has(o, idKey)) {
      newObj[idKey] = resolve(o, idKey);
    }
    return newObj;
  };
}
function checkExpression(expr, options) {
  let exclusions = false;
  let inclusions = false;
  let positional = 0;
  for (const [k, v] of Object.entries(expr)) {
    assert(!k.startsWith("$"), "Field names may not start with '$'.");
    if (k.endsWith(".$")) {
      assert(
        ++positional < 2,
        "Cannot specify more than one positional projection per query."
      );
    }
    if (k === options?.idKey) continue;
    if (v === 0 || v === false) {
      exclusions = true;
    } else if (v === 1 || v === true) {
      inclusions = true;
    }
    assert(
      !(exclusions && inclusions),
      "Projection cannot have a mix of inclusion and exclusion."
    );
  }
}
const findMatches = (o, key, leaf, pred) => {
  let arr = resolve(o, key);
  if (!isArray(arr)) arr = resolve(arr, leaf);
  assert(isArray(arr), "must resolve to array");
  const matches = [];
  arr.forEach((e, i) => pred({ [leaf]: [e] }) && matches.push(i));
  return matches;
};
const complement = (p) => (e) => !p(e);
const COMPOUND_OPS = { $and: 1, $or: 1, $nor: 1 };
function getPositionalFilter(field, condition, options) {
  const stack = Object.entries(condition).slice();
  const selectors = { $and: [], $or: [] };
  for (let i = 0; i < stack.length; i++) {
    const [key, val, op] = stack[i];
    if (key === field || key.startsWith(field + ".")) {
      const [operator, expr] = Object.entries(normalize(val)).pop();
      const fn = options.context.getOperator(
        OpType.QUERY,
        operator
      );
      const leaf2 = key.substring(key.lastIndexOf(".") + 1);
      const pred = fn(leaf2, expr, options);
      if (!op || op === "$and") {
        selectors["$and"].push([key, pred, leaf2]);
      } else if (op === "$nor") {
        selectors["$and"].push([key, complement(pred), leaf2]);
      } else if (op === "$or") {
        selectors["$or"].push([key, pred, leaf2]);
      }
    } else if (isOperator(key)) {
      assert(COMPOUND_OPS[key], `${key} is not allowed in this context`);
      for (const item of val) {
        Object.entries(item).forEach(([k, v]) => stack.push([k, v, key]));
      }
    }
  }
  const sep = field.lastIndexOf(".");
  const parent = field.substring(0, sep) || field;
  const leaf = field.substring(sep + 1);
  return (o) => {
    const matches = [];
    for (const [key, pred, leaf2] of selectors["$and"]) {
      matches.push(findMatches(o, key, leaf2, pred));
    }
    if (selectors["$or"].length) {
      const orMatches = [];
      for (const [key, pred, leaf2] of selectors["$or"]) {
        orMatches.push(...findMatches(o, key, leaf2, pred));
      }
      matches.push(unique(orMatches));
    }
    const i = intersection(matches).sort()[0];
    let first = resolve(o, field)[i];
    if (parent != leaf && !isObject(first)) {
      first = { [leaf]: first };
    }
    setValue(o, parent, [first]);
  };
}
export {
  $project
};