Ledger with Expiration

require 'date'

points_ledger = [
    { amount: 5, expires_at: DateTime.new(2020,8,1)},
    { amount: 10, expires_at: DateTime.new(2020,8,2)},
    { amount: 2, expires_at: DateTime.new(2020,8,3)},
]

def add_points(ledger, amount, exp_date)
  puts "Adding #{amount} points"
  ledger.push({ amount: amount, expires_at: exp_date})
end

def debit_points(ledger, amount)
  puts "Debiting #{amount} points"
  ledger.push({ amount: -amount, exp_date: nil})
end

def ledger_balance(ledger)
  ledger.map { |item| item[:amount] }.sum
end

def expired_credits_amount(ledger, exp_date)
  ledger.filter { |item| item[:amount] > 0 && item[:expires_at] < exp_date }.map { |item| item[:amount] }.sum
end

def expire_points(ledger, exp_date)
  balance = ledger_balance(ledger)
  expired_credits = expired_credits_amount(ledger, exp_date)
  debit_amount = [balance, expired_credits].min

  puts
  puts "Expires At: #{exp_date}"
  puts "Ledger Balance: #{balance}"
  puts "Expired Credits: #{expired_credits}"
  puts "Debiting #{debit_amount}"

  if debit_amount > 0
    debit_points(ledger, debit_amount)
  end
end

def display_balance(ledger)
  puts
  puts "Ledger Balance: #{ledger_balance(ledger)}"
end

display_balance(points_ledger)

debit_points(points_ledger, 7)
display_balance(points_ledger)

add_points(points_ledger, 8, DateTime.new(2020,8,5))
display_balance(points_ledger)

expire_points(points_ledger, DateTime.new(2020,8,2))
display_balance(points_ledger)

debit_points(points_ledger, 4)
display_balance(points_ledger)

debit_points(points_ledger, 3)
display_balance(points_ledger)

expire_points(points_ledger, DateTime.new(2020,8,5))
display_balance(points_ledger)

add_points(points_ledger, 5, DateTime.new(2020,8,8))
display_balance(points_ledger)

add_points(points_ledger, 2, DateTime.new(2020,8,9))
display_balance(points_ledger)

expire_points(points_ledger, DateTime.new(2020,8,9))
display_balance(points_ledger)

add_points(points_ledger, 12, DateTime.new(2020,8,10))
display_balance(points_ledger)

debit_points(points_ledger, 8)
display_balance(points_ledger)

add_points(points_ledger, 5, DateTime.new(2020,8,12))
display_balance(points_ledger)

add_points(points_ledger, 5, DateTime.new(2020,8,13))
display_balance(points_ledger)