|
1
|
|
|
<?php |
|
2
|
|
|
|
|
3
|
|
|
declare(strict_types = 1); |
|
4
|
|
|
|
|
5
|
|
|
namespace Kauri\Loan\PaymentAmountCalculator; |
|
6
|
|
|
|
|
7
|
|
|
use Kauri\Loan\PaymentAmountCalculatorInterface; |
|
8
|
|
|
|
|
9
|
|
|
class EqualPrincipalPaymentAmountCalculator implements PaymentAmountCalculatorInterface |
|
10
|
|
|
{ |
|
11
|
|
|
/** |
|
12
|
|
|
* @param array $periods |
|
13
|
|
|
* @param float $presentValue |
|
14
|
|
|
* @param float $interestRate |
|
15
|
|
|
* @param float $futureValue |
|
16
|
|
|
* @return array |
|
17
|
|
|
*/ |
|
18
|
3 |
|
public function getPaymentAmounts( |
|
19
|
|
|
array $periods, |
|
20
|
|
|
float $presentValue, |
|
21
|
|
|
float $interestRate, |
|
22
|
|
|
float $futureValue |
|
23
|
|
|
): array { |
|
24
|
3 |
|
$paymentAmounts = array(); |
|
25
|
|
|
|
|
26
|
3 |
|
$principalLeft = $presentValue; |
|
27
|
3 |
|
$noOfPayments = count($periods); |
|
28
|
3 |
|
$principal = $this->getPrincipalPart($presentValue, $futureValue, $noOfPayments); |
|
29
|
|
|
|
|
30
|
3 |
|
foreach ($periods as $sequenceNo => $periodLength) { |
|
31
|
3 |
|
$ratePerPeriod = $this->getPeriodInterestRate($interestRate, $periodLength); |
|
32
|
3 |
|
$noOfRemainingPeriods = $noOfPayments - $sequenceNo + 1; |
|
33
|
|
|
|
|
34
|
3 |
|
$paymentAmount = $this->getPaymentAmount($principalLeft, $futureValue, $ratePerPeriod, |
|
35
|
|
|
$noOfRemainingPeriods); |
|
36
|
|
|
|
|
37
|
3 |
|
$principalLeft = $this->decreasePrincipalLeft($principalLeft, $principal); |
|
38
|
|
|
|
|
39
|
3 |
|
$paymentAmounts[$sequenceNo] = $paymentAmount; |
|
40
|
|
|
} |
|
41
|
|
|
|
|
42
|
3 |
|
return $paymentAmounts; |
|
43
|
|
|
} |
|
44
|
|
|
|
|
45
|
|
|
/** |
|
46
|
|
|
* @param float $presentValue |
|
47
|
|
|
* @param float $discount |
|
48
|
|
|
* @return float |
|
49
|
|
|
*/ |
|
50
|
3 |
|
private function decreasePrincipalLeft(float $presentValue, float $discount) |
|
51
|
|
|
{ |
|
52
|
3 |
|
return (float) ($presentValue - $discount); |
|
53
|
|
|
} |
|
54
|
|
|
|
|
55
|
|
|
/** |
|
56
|
|
|
* @param $interestRate |
|
57
|
|
|
* @param $periodLength |
|
58
|
|
|
* @return float |
|
59
|
|
|
*/ |
|
60
|
3 |
|
private function getPeriodInterestRate(float $interestRate, float $periodLength): float |
|
61
|
|
|
{ |
|
62
|
3 |
|
$periodRate = $interestRate / 360 * $periodLength; |
|
63
|
3 |
|
return (float) $periodRate; |
|
64
|
|
|
} |
|
65
|
|
|
|
|
66
|
|
|
/** |
|
67
|
|
|
* @param float $presentValue |
|
68
|
|
|
* @param float $futureValue |
|
69
|
|
|
* @param int $noOfPeriods |
|
70
|
|
|
* @return float |
|
71
|
|
|
*/ |
|
72
|
3 |
|
private function getPrincipalPart(float $presentValue, float $futureValue, int $noOfPeriods): float |
|
73
|
|
|
{ |
|
74
|
3 |
|
$principal = ($presentValue - $futureValue) / $noOfPeriods; |
|
75
|
|
|
|
|
76
|
3 |
|
return (float) $principal; |
|
77
|
|
|
} |
|
78
|
|
|
|
|
79
|
|
|
/** |
|
80
|
|
|
* @param float $presentValue |
|
81
|
|
|
* @param float $futureValue |
|
82
|
|
|
* @param float $ratePerPeriod |
|
83
|
|
|
* @param int $numberOfPeriods |
|
84
|
|
|
* @return float |
|
85
|
|
|
*/ |
|
86
|
3 |
|
private function getPaymentAmount( |
|
87
|
|
|
float $presentValue, |
|
88
|
|
|
float $futureValue, |
|
89
|
|
|
float $ratePerPeriod, |
|
90
|
|
|
int $numberOfPeriods |
|
91
|
|
|
): float { |
|
92
|
3 |
|
$principal = $this->getPrincipalPart($presentValue, $futureValue, $numberOfPeriods); |
|
93
|
|
|
|
|
94
|
3 |
|
if ($ratePerPeriod > 0) { |
|
95
|
|
|
$payment = $principal + $presentValue * ($ratePerPeriod / 100); |
|
96
|
|
|
} else { |
|
97
|
3 |
|
$payment = $principal; |
|
98
|
|
|
} |
|
99
|
|
|
|
|
100
|
3 |
|
return (float) $payment; |
|
101
|
|
|
} |
|
102
|
|
|
} |
|
103
|
|
|
|
kaurikk /
loan-amount-calculator
