import Diff from './base';

import {lineDiff} from './line';

const objectPrototypeToString = Object.prototype.toString;

export const jsonDiff = new Diff();

// Discriminate between two lines of pretty-printed, serialized JSON where one of them has a

// dangling comma and the other doesn't. Turns out including the dangling comma yields the nicest output:

jsonDiff.useLongestToken = true;

jsonDiff.tokenize = lineDiff.tokenize;

jsonDiff.castInput = function(value) {

return typeof value === 'string' ? value : JSON.stringify(canonicalize(value), undefined, ' ');

};

jsonDiff.equals = function(left, right) {

return Diff.prototype.equals(left.replace(/,([\r\n])/g, '$1'), right.replace(/,([\r\n])/g, '$1'));

};

export function diffJson(oldObj, newObj, callback) { return jsonDiff.diff(oldObj, newObj, callback); }

// This function handles the presence of circular references by bailing out when encountering an

// object that is already on the "stack" of items being processed.

export function canonicalize(obj, stack, replacementStack) {

stack = stack || [];

replacementStack = replacementStack || [];

let i;

for (i = 0; i < stack.length; i += 1) {

if (stack[i] === obj) {

return replacementStack[i];

}

}

let canonicalizedObj;

if ('[object Array]' === objectPrototypeToString.call(obj)) {

stack.push(obj);

canonicalizedObj = new Array(obj.length);

replacementStack.push(canonicalizedObj);

for (i = 0; i < obj.length; i += 1) {

canonicalizedObj[i] = canonicalize(obj[i], stack, replacementStack);

}

stack.pop();

replacementStack.pop();

} else if (typeof obj === 'object' && obj !== null) {

stack.push(obj);

canonicalizedObj = {};

replacementStack.push(canonicalizedObj);

let sortedKeys = [],

key;

for (key in obj) {

/* istanbul ignore else */

if (obj.hasOwnProperty(key)) {

sortedKeys.push(key);

}

}

sortedKeys.sort();

for (i = 0; i < sortedKeys.length; i += 1) {

key = sortedKeys[i];

canonicalizedObj[key] = canonicalize(obj[key], stack, replacementStack);

}

stack.pop();

replacementStack.pop();

} else {

canonicalizedObj = obj;

}

return canonicalizedObj;

}