80 lines
3.2 KiB
JavaScript
80 lines
3.2 KiB
JavaScript
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/*
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Copyright 2016 OpenMarket Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* For two objects of the form { key: [val1, val2, val3] }, work out the added/removed
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* values. Entirely new keys will result in the entire value array being added.
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* @param {Object} before
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* @param {Object} after
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* @return {Object[]} An array of objects with the form:
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* { key: $KEY, val: $VALUE, place: "add|del" }
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*/
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module.exports.getKeyValueArrayDiffs = function(before, after) {
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var results = [];
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var delta = {};
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Object.keys(before).forEach(function(beforeKey) {
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delta[beforeKey] = delta[beforeKey] || 0; // init to 0 initially
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delta[beforeKey]--; // keys present in the past have -ve values
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});
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Object.keys(after).forEach(function(afterKey) {
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delta[afterKey] = delta[afterKey] || 0; // init to 0 initially
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delta[afterKey]++; // keys present in the future have +ve values
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});
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Object.keys(delta).forEach(function(muxedKey) {
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switch (delta[muxedKey]) {
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case 1: // A new key in after
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after[muxedKey].forEach(function(afterVal) {
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results.push({ place: "add", key: muxedKey, val: afterVal });
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});
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break;
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case -1: // A before key was removed
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before[muxedKey].forEach(function(beforeVal) {
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results.push({ place: "del", key: muxedKey, val: beforeVal });
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});
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break;
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case 0: // A mix of added/removed keys
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// compare old & new vals
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var itemDelta = {};
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before[muxedKey].forEach(function(beforeVal) {
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itemDelta[beforeVal] = itemDelta[beforeVal] || 0;
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itemDelta[beforeVal]--;
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});
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after[muxedKey].forEach(function(afterVal) {
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itemDelta[afterVal] = itemDelta[afterVal] || 0;
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itemDelta[afterVal]++;
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});
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Object.keys(itemDelta).forEach(function(item) {
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if (itemDelta[item] === 1) {
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results.push({ place: "add", key: muxedKey, val: item });
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} else if (itemDelta[item] === -1) {
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results.push({ place: "del", key: muxedKey, val: item });
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} else {
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// itemDelta of 0 means it was unchanged between before/after
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}
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});
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break;
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default:
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console.error("Calculated key delta of " + delta[muxedKey] +
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" - this should never happen!");
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break;
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}
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});
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return results;
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};
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