commit fda87aae24c0a6adf343c5eaefa379480fd624a0
Author: Malar Kannan <malarkannan.p@gmail.com>
Date:   Mon Jul 17 12:30:45 2017 +0530

    initial version

diff --git a/invoice.py b/invoice.py
new file mode 100644
index 0000000..c9b925e
--- /dev/null
+++ b/invoice.py
@@ -0,0 +1,72 @@
+from threading import Timer
+import json
+import datetime
+
+
+def json_time(x): return datetime.datetime.strptime(x, '%Y-%m-%dT%H:%M:%S.%fZ')
+
+
+def seconds_remaining(r_d): return (
+    r_d - datetime.datetime.now()).total_seconds()
+
+
+class InvoiceData(object):
+    """docstring for InvoiceData."""
+
+    def __init__(self, invoice_data):
+        super(InvoiceData, self).__init__()
+        self.customer_id = invoice_data["customer_id"]
+        self.due_date = json_time(invoice_data["invoice_due_date"])
+        self.amount = invoice_data["invoice_amount"]
+        rem_start = invoice_data["reminder_start"]
+        rem_every = invoice_data["reminder_every"]
+        self.remind_before = datetime.timedelta(0, int(rem_start))
+        self.reminder_interval = datetime.timedelta(0, int(rem_every))
+
+    def __repr__(self):
+        return self.customer_id + "#" + self.due_date
+
+    def print_invoice(self):
+        invoice_str = "INVOICE FOR CUSTOMER ID : {}\nDATE:{}\nAMOUNT:{}\n"
+        print invoice_str.format(self.customer_id, self.due_date, self.amount)
+
+    def print_reminder(self):
+        inv_str = "REMINDER FOR CUSTOMER ID : {}\nINVOICE DUE ON :{}\nAMOUNT:{}\n"
+        print inv_str.format(self.customer_id, self.due_date, self.amount)
+
+    def schedule_reminders(self):
+        current_time = datetime.datetime.now()
+        reminder_start = (self.due_date - self.remind_before)
+        reminder_time = self.due_date - self.reminder_interval
+
+        def closed_reminder():
+            self.print_reminder()
+        while (reminder_time >= reminder_start
+               and reminder_time < self.due_date
+               and seconds_remaining(reminder_time) > 0):
+            inv_timer = Timer(seconds_remaining(
+                reminder_time), closed_reminder)
+            inv_timer.start()
+            reminder_time = reminder_time - self.reminder_interval
+
+    def schedule_invoice(self):
+        self.schedule_reminders()
+
+        def closed_invoice():
+            self.print_invoice()
+        if seconds_remaining(self.due_date) > 0:
+            inv_timer = Timer(seconds_remaining(self.due_date), closed_invoice)
+            inv_timer.start()
+
+    @classmethod
+    def from_json(cls, file_name):
+        invoice_data = json.load(open(file_name, 'rb'))
+        invoice_list = []
+        for inv_d in invoice_data:
+            invoice_list.append(cls(inv_d))
+        return invoice_list
+
+invoices = InvoiceData.from_json("./invoice_data.json")
+for inv in invoices:
+    inv.print_invoice()
+    inv.schedule_invoice()
diff --git a/invoice_data.json b/invoice_data.json
new file mode 100644
index 0000000..39eb254
--- /dev/null
+++ b/invoice_data.json
@@ -0,0 +1,19 @@
+[{
+  "customer_id": "123",
+  "invoice_due_date": "2017-07-17T12:12:00.511Z",
+  "reminder_start": "10",
+  "reminder_every": "5",
+  "invoice_amount": "1000"
+},{
+  "customer_id": "124",
+  "invoice_due_date": "2017-07-17T12:21:00.511Z",
+  "reminder_start": "10",
+  "reminder_every": "5",
+  "invoice_amount": "1000"
+},{
+  "customer_id": "125",
+  "invoice_due_date": "2017-07-17T12:22:00.511Z",
+  "reminder_start": "60",
+  "reminder_every": "20",
+  "invoice_amount": "1000"
+}]