var equal = require('deep-equal');
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var extend = require('extend');
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var lib = {
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attributes: {
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compose: function (a, b, keepNull) {
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if (typeof a !== 'object') a = {};
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if (typeof b !== 'object') b = {};
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var attributes = extend(true, {}, b);
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if (!keepNull) {
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attributes = Object.keys(attributes).reduce(function (copy, key) {
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if (attributes[key] != null) {
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copy[key] = attributes[key];
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}
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return copy;
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}, {});
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}
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for (var key in a) {
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if (a[key] !== undefined && b[key] === undefined) {
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attributes[key] = a[key];
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}
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}
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return Object.keys(attributes).length > 0 ? attributes : undefined;
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},
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diff: function(a, b) {
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if (typeof a !== 'object') a = {};
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if (typeof b !== 'object') b = {};
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var attributes = Object.keys(a).concat(Object.keys(b)).reduce(function (attributes, key) {
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if (!equal(a[key], b[key])) {
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attributes[key] = b[key] === undefined ? null : b[key];
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}
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return attributes;
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}, {});
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return Object.keys(attributes).length > 0 ? attributes : undefined;
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},
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transform: function (a, b, priority) {
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if (typeof a !== 'object') return b;
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if (typeof b !== 'object') return undefined;
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if (!priority) return b; // b simply overwrites us without priority
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var attributes = Object.keys(b).reduce(function (attributes, key) {
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if (a[key] === undefined) attributes[key] = b[key]; // null is a valid value
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return attributes;
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}, {});
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return Object.keys(attributes).length > 0 ? attributes : undefined;
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}
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},
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iterator: function (ops) {
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return new Iterator(ops);
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},
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length: function (op) {
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if (typeof op['delete'] === 'number') {
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return op['delete'];
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} else if (typeof op.retain === 'number') {
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return op.retain;
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} else {
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return typeof op.insert === 'string' ? op.insert.length : 1;
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}
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}
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};
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function Iterator(ops) {
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this.ops = ops;
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this.index = 0;
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this.offset = 0;
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};
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Iterator.prototype.hasNext = function () {
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return this.peekLength() < Infinity;
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};
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Iterator.prototype.next = function (length) {
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if (!length) length = Infinity;
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var nextOp = this.ops[this.index];
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if (nextOp) {
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var offset = this.offset;
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var opLength = lib.length(nextOp)
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if (length >= opLength - offset) {
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length = opLength - offset;
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this.index += 1;
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this.offset = 0;
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} else {
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this.offset += length;
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}
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if (typeof nextOp['delete'] === 'number') {
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return { 'delete': length };
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} else {
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var retOp = {};
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if (nextOp.attributes) {
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retOp.attributes = nextOp.attributes;
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}
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if (typeof nextOp.retain === 'number') {
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retOp.retain = length;
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} else if (typeof nextOp.insert === 'string') {
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retOp.insert = nextOp.insert.substr(offset, length);
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} else {
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// offset should === 0, length should === 1
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retOp.insert = nextOp.insert;
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}
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return retOp;
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}
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} else {
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return { retain: Infinity };
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}
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};
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Iterator.prototype.peek = function () {
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return this.ops[this.index];
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};
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Iterator.prototype.peekLength = function () {
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if (this.ops[this.index]) {
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// Should never return 0 if our index is being managed correctly
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return lib.length(this.ops[this.index]) - this.offset;
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} else {
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return Infinity;
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}
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};
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Iterator.prototype.peekType = function () {
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if (this.ops[this.index]) {
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if (typeof this.ops[this.index]['delete'] === 'number') {
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return 'delete';
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} else if (typeof this.ops[this.index].retain === 'number') {
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return 'retain';
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} else {
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return 'insert';
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}
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}
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return 'retain';
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};
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Iterator.prototype.rest = function () {
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if (!this.hasNext()) {
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return [];
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} else if (this.offset === 0) {
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return this.ops.slice(this.index);
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} else {
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var offset = this.offset;
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var index = this.index;
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var next = this.next();
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var rest = this.ops.slice(this.index);
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this.offset = offset;
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this.index = index;
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return [next].concat(rest);
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}
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};
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module.exports = lib;
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