go_workshop/chapter_03/activity_3.02/main.go

package main

import (
  "errors"
  "fmt"
)

const (
  goodScore      = 450
  lowScoreRation = 10
  goodScoreRatio = 20
)

var (
  ErrCreditScore = errors.New("invalid credit score")
  ErrIncome      = errors.New("income invalid")
  ErrLoanAmount  = errors.New("loan amount invalid")
  ErrLoanTerm    = errors.New("loan term not a multiple of 12")
)

func checkLoan(creditScore int, income float64,
  loanAmount float64, loanTerm float64) error {

  interest := 20.0

  if creditScore >= goodScore {
    interest = 15
  }

  if creditScore < 1 {
    return ErrCreditScore
  }

  if income < 1 {
    return ErrIncome
  }

  if loanAmount < 1 {
    return ErrLoanAmount
  }

  if loanTerm < 1 || int(loanTerm)%12 != 0 {
    return ErrLoanTerm
  }

  rate := interest / 100

  payment := ((loanAmount * rate) / loanTerm) + (loanAmount / loanTerm)
  totalInterest := (payment * loanTerm) - loanAmount

  approved := false

  if income > payment {
    ratio := (payment / income) * 100
    if creditScore >= goodScore && ratio < goodScoreRatio {
      approved = true
    } else if ratio < lowScoreRation {
      approved = true
    }
  }

  fmt.Println("Credit Score    :", creditScore)
  fmt.Println("Income          :", income)
  fmt.Println("Loan Amount     :", loanAmount)
  fmt.Println("Loan Term       :", loanTerm)
  fmt.Println("Monthly Payment :", payment)
  fmt.Println("Rate            :", interest)
  fmt.Println("Total Cost      :", totalInterest)
  fmt.Println("Approved        :", approved)
  fmt.Println("")

  return nil

}

func main() {

  // Approved
  fmt.Println("Applicant 1")
  fmt.Println("-----------")
  err := checkLoan(500, 1000, 1000, 24)
  if err != nil {
    fmt.Println("Error:", err)
  }

  // Denied
  fmt.Println("Applicant 2")
  fmt.Println("-----------")
  err = checkLoan(350, 1000, 10000, 12)
  if err != nil {
    fmt.Println("Error:", err)
  }

}