const assert = require("assert");
const {Suite} = require("benchmark");
const pad = require("pad");

// Implementations

function loop(array, index) {
    for (let i = index; i < array.length - 1; i++) {
        array[i] = array[i + 1];
    }
    array.pop();
}

function splice(array, index) {
    array.splice(index, 1);
}

function memcpy(array, index) {
    array.copyWithin(index, index + 1);
    array.pop();
}

const fns = [loop, splice, memcpy];


// Correctness check

function randint(min, max) {
    return min + Math.floor(Math.random() * (max - min));
}

for (const f of fns) {
    const arr = sampleArray(100);
    for (let len = arr.length; len > 0; len--) {
        const i = randint(0, len);
        const em = arr[i];
        assert(arr.indexOf(em) !== -1);
        f(arr, i);
        assert(arr.indexOf(em) === -1);
        assert.equal(arr.length, len - 1);
    }
}


// Test helpers

function sampleArray(N) {
    const arr = new Array(N);
    for (let i = 0; i < N; i++) {
        arr[i] = i;
    }
    return arr;
}

function testFront(n, remove) {
    const arr = sampleArray(n);
    for (let len = arr.length; len > 0; len--) {
        remove(arr, 0);
        assert(arr.length === len - 1);
    }
}

function testRear(n, remove) {
    const arr = sampleArray(n);
    for (let len = arr.length; len > 0; len--) {
        remove(arr, len - 1);
        assert(arr.length === len - 1);
    }
}


// Perf test

function test(makeSuite) {
    const suite = new Suite();
    makeSuite(suite);
    suite.on("complete", function() {
        this.forEach(({name, stats}) => {
            console.log(`${name}: ${stats.mean * 1000}ms`);
        });
    });
    suite.on("error", error => {
        throw error.target.error;
    });
    suite.run();
}

test(suite => {
    for (const test of [testFront, testRear]) {
        for (const n of [10, 100, 1000]) {
            for (const f of fns) {
                suite.add(`${pad(9, test.name)} ${pad(4, n)} ${pad(6, f.name)}`, () => test(n, f));
            }
        }
    }
});

testFront   10   loop: 0.00028075305868859946ms
testFront   10 splice: 0.0024167716220477586ms
testFront   10 memcpy: 0.003104232232456715ms

testFront  100   loop: 0.014285475240188552ms
testFront  100 splice: 0.023001260699088717ms
testFront  100 memcpy: 0.28665747186761226ms

testFront 1000   loop: 1.1882795027214252ms
testFront 1000 splice: 0.23387040256038646ms
testFront 1000 memcpy: 26.856770945312498ms

 testRear   10   loop: 0.0001227723598808805ms
 testRear   10 splice: 0.002122261221082299ms
 testRear   10 memcpy: 0.0004173716600574439ms

 testRear  100   loop: 0.001598535853706533ms
 testRear  100 splice: 0.021219825430875625ms
 testRear  100 memcpy: 0.0037203930576036157ms

 testRear 1000   loop: 0.015465716346486885ms
 testRear 1000 splice: 0.21165966573636746ms
 testRear 1000 memcpy: 0.03714556813039422ms