total-order/any

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src/index.js

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1 day
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import assert from 'assert';
import {prop} from '@total-order/key';
import {quasilexicographical} from '@total-order/lex';
import {increasing as compare} from '@total-order/primitive';
import {MemoryEfficientPairs as Pairs} from '@collection-abstraction/pairs';

const deepCompare = (a, b) => {
    if (a === b) return 0;

    const left = [[a]];
    const right = [[b]];
    const pos = [0];
    const pendingOrChecked = Pairs.from([]);

    while (left.length > 0) {
        assert(left.length === right.length);
        assert(left.length === pos.length);

        const last = left.length - 1;
        const array_a = left[last];
        const array_b = right[last];
        const i = pos[last];

        assert(array_a.length === array_b.length);
        assert(i >= 0 && i <= array_a.length);
        if (i === array_a.length) {
            left.pop();
            right.pop();
            pos.pop();
            continue;
        }

        ++pos[last];

        const _a = array_a[i];
        const _b = array_b[i];
        const typeof_a = typeof _a;
        const typeof_b = typeof _b;

        const delta_type = compare(typeof_a, typeof_b);
        if (delta_type !== 0) return delta_type;

        if (typeof_a !== 'object') {
            const delta_primitive = comparePrimitives(typeof_a, _a, _b);
            if (delta_primitive !== 0) return delta_primitive;
            continue;
        }

        assert(typeof_a === 'object');

        if (_a === null) {
            if (_b === null) continue;
            return -1;
        }

        if (_b === null) {
            return 1;
        }

        if (pendingOrChecked.has([_a, _b])) continue;
        pendingOrChecked.add([_a, _b]);
        pendingOrChecked.add([_b, _a]);

        const constructor_a = a.constructor;
        const constructor_b = b.constructor;

        if (constructor_a !== constructor_b)
            return compare(constructor_a.name, constructor_b.name);

        // TODO typed arrays
        // TODO other built-ins, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects
        switch (constructor_a) {
            case RegExp:
                const delta_regexp = compare(_a.toString(), _b.toString());
                if (delta_regexp !== 0) return delta_regexp;
                continue;
            case Date:
                const delta_date = compare(_a.getTime(), _b.getTime());
                if (delta_date !== 0) return delta_date;
                continue;
            case Array:
                if (_a.length !== _b.length) return _a.length - _b.length;
                left.push(_a);
                right.push(_b);
                pos.push(0);
                continue;
            case Object:
                const keys_a = Object.keys(_a).sort(compare);
                const keys_b = Object.keys(_b).sort(compare);

                const delta_keys = compareStringArrays(keys_a, keys_b);
                if (delta_keys !== 0) return delta_keys;

                const values_a = Object.entries(_a)
                    .sort(compareEntries)
                    .map((x) => x[1]);
                const values_b = Object.entries(_b)
                    .sort(compareEntries)
                    .map((x) => x[1]);

                left.push(values_a);
                right.push(values_b);
                pos.push(0);
                continue;
            default:
                throw new Error(
                    `deepCompare: unhandled constructor '${constructor_a.name}'`,
                );
        }
    }

    return 0;
};

const comparePrimitives = (kind, _a, _b) => {
    assert(kind !== 'object');
    switch (kind) {
        case 'number':
            if (Number.isNaN(_a)) {
                if (Number.isNaN(_b)) return 0;
                return 1;
            }

            if (Number.isNaN(_b)) {
                return -1;
            }

        case 'boolean':
        case 'string':
        case 'bigint':
            return compare(_a, _b);
        case 'function':
            return compare(_a.toString(), _b.toString());
        default:
            throw new Error(`deepCompare: unhandled primitive type '${kind}'`);
    }
};

const compareEntries = prop(compare, 0);
// Const compareArrays = quasilexicographical(deepCompare);
const compareStringArrays = quasilexicographical(compare);
// Const compareObjects = (a, b) => {
// const keys_a = Object.keys(a).sort(compare);
// const keys_b = Object.keys(b).sort(compare);

// const delta_keys = compareStringArrays(keys_a, keys_b);
// if (delta_keys !== 0) return delta_keys;

// const values_a = Object.entries(a)
// .sort(compareEntries)
// .map((x) => x[1]);
// const values_b = Object.entries(b)
// .sort(compareEntries)
// .map((x) => x[1]);

// return compareArrays(values_a, values_b);
// };

export default deepCompare;