import sys
import re

## run CreditLine.py with -u flag (unbuffered )
## 		python -u CreditLine.py
## -a flag : set APR, will read in input as decimal unless '%' specified
## 		default APR is 35%
## -l flag : set Credit Limit, will read in input as decimal
##		default Credit Limit is 1000

## TO IMPLEMENT FURTHER:
## - Better way for two decimal point rounding or treat money as integers (dollars & cents)
## - clean up transaction_list and add further functionality (e.g. show payments and draws)
## - don't use global variables

## Default APR and Credit Limit
APR = .35
CREDIT_LIMIT = 1000
DAY = 0

BALANCE = 0

## transactions_list = [[Day, 'Drew'/'Paid', amount, Remaining Credit, Principial Balance], [...], ...]
transactions_list = []


## TO IMPLEMENT FURTHER FUNCTIONALITY:
## instead of ending program after payment period end, start a new period
# def start(usrInput):
# 	APR = .35
# 	CREDIT_LIMIT = 1000
# 	DAY = 0
# 	BALANCE = 0

## input: Boolean for end of period
## Function: Prints transactions and current results
def print_summary(end):
	print_results(end)
	if not transactions_list:
		print("You have not made any transactions!")
		return
	for item in transactions_list:
		print("Day " + str(item[0]) + ": " + item[1] + " $" + str(item[2]) +
			  "\n> Remaining Credit Limit: $" + str(item[3]) + "\n> Principal Balance: $" + str(item[4]))

## input: Boolean for end of period
## Function: Prints current results
def print_results(end):
	global DAY, CREDIT_LIMIT, BALANCE, transactions_list
	print("Today is Day " + str(DAY))
	if (end):
		interest = calc_interest()
		print("> Principal Balance: $%.2f" % BALANCE)
		print("> Total Interest Payment: $%.2f" % interest)
		print("> Total Payment: $%.2f" % (BALANCE + interest))
		sys.exit(">>> Credit Line quitting")
	else:
		print("> Remaining Credit Limit: $%.2f" % CREDIT_LIMIT)
		print("> Principal Balance: $%.2f" % BALANCE)
		print("> Current Total Interest: $%.2f" % calc_interest())

## Function: Calculates interest
## transactions_lust = [[Day, 'Drew'/'Paid', amount, Remaining Credit, Principial Balance],
##						[...],
## 						 ...
## 						[...]]
def calc_interest():
	global DAY, transactions_list, APR, BALANCE
	interest = 0
	for i in xrange(1, len(transactions_list)):
		## for each day period, calculates interest
		interest += transactions_list[i-1][4] * APR/(float(365)) * (transactions_list[i][0] - transactions_list[i-1][0])
	## adds interest for final balance
	if (len(transactions_list) == 0):
		return interest
	interest += BALANCE * APR/(float(365)) * (DAY - transactions_list[len(transactions_list) - 1][0])
	return interest

def draw_fun(amount):
	global DAY, CREDIT_LIMIT, BALANCE, transactions_list
	if (amount < CREDIT_LIMIT):
		CREDIT_LIMIT -= amount
		BALANCE += amount
		transactions_list.append([DAY, 'Drew', amount, CREDIT_LIMIT, BALANCE])
	else:
		print(">>> You can't draw more than credit limit!")
	print_results(False)

def pay_fun(amount):
	global DAY, CREDIT_LIMIT, BALANCE, transactions_list
	if (amount < BALANCE):
		BALANCE -= amount
		CREDIT_LIMIT += amount
		transactions_list.append([DAY, 'Paid', amount, CREDIT_LIMIT, BALANCE])
	else:
		print(">>> You don't owe that much money!")
	print_results(False)

def is_number(s):
    try:
        float(s)
    except ValueError:
        return False
    return (float(s) >= 0.01)

if __name__ == "__main__":

	## Sets the APR and Credit Limit
	for i in xrange(1,len(sys.argv)):
		if sys.argv[i] == '-a':
			APR = float(re.sub(r'[^\d.]+', '', sys.argv[i+1])) # strips to leave decimal
			if ('%' in sys.argv[i+1]):
				APR = APR * 0.01
		if sys.argv[i] == '-l':
			CREDIT_LIMIT = float(re.sub(r'[^\d.]+', '', sys.argv[i+1]))

	print ("APR: %.2f" % (APR*100) + '%')
	print ("Line of Credit: $%.2f" % CREDIT_LIMIT)
	print ("Type 'h' for help and list of commands")


	## Implemented some basic typechecking
	while True:
		if (DAY == 30):
			print_summary(True)
		usrInput = sys.stdin.readline().rstrip('\n').split()

		for i in xrange(0, len(usrInput)):

			if (usrInput[i] in ['quit', 'Quit', 'q']):
				print_summary(True)
				sys.exit(">>> Credit Line quitting")

			elif (usrInput[i] in ["Next", "next", 'n']): # Next DAY
				if (DAY < 30):
					DAY += 1
					print_results(False)
				else:
					print(">>> End of Period, cannot go to next day")

			elif (usrInput[i] in ["Day", 'day']): # Skips to that DAY
				if is_number(usrInput[i+1]) == False:
					print("Please input a valid integer number for Day")
				elif (int(usrInput[i+1]) > DAY) and (int(usrInput[i+1]) <= 30):
					DAY = int(usrInput[i+1])
					print_results(False)
				else:
					DAY = 30
					print_summary(True)

			elif (usrInput[i] in ["Draw", "draw", 'd']):
				if is_number(usrInput[i+1]) == False:
					print("Please input a valid two decimal point number for draw amount")
				else:
					draw_fun(float(re.sub(r'[^\d.]+', '', usrInput[i+1])))

			elif (usrInput[i] in ["Pay", "pay", 'p']):
				if is_number(usrInput[i+1]) == False:
					print("Please input a valid two decimal point number for pay amount")
				else:
					pay_fun(float(re.sub(r'[^\d.]+', '', usrInput[i+1])))

			elif (usrInput[i] in ["Summary", "summary", 's']):
				print_summary(False)

			elif (usrInput[i] in ["Help", "help", 'h']):
				print("This program calculates your total payment at the end of the 30-day period.")
				print("Commands are not case sensitive. Separate commands by spaces or press enter")
				print("Type 'q' or 'quit' to quit the program")
				print("Type 's' or 'summary' for a Transaction Summary")
				print("Type 'n' or 'next' to proceed to the Next Day or 'day' followed by a space and integer value to jump to a specific day")
				print("Type 'd' or 'draw' to draw money")
				print("Type 'p' or 'pay' to pay money")