Implemented the period parser.

accounting/utils.py

@@ -18,6 +18,13 @@
 """The utilities of the accounting application.
 
 """
+import re
+from datetime import date
+
+from django.template import defaultfilters
+from django.utils import dateformat
+from django.utils.timezone import localdate, timedelta
+from django.utils.translation import pgettext, gettext
 
 
 class PeriodParser:
@@ -27,14 +34,192 @@ class PeriodParser:
         period_spec (str): The period specification.
 
     Attributes:
-        start (str): The start of the period.
-        end (str): The end of the period.
+        spec (str): The period specification.
+        start (date): The start of the period.
+        end (date): The end of the period.
+        description (str): The text description of the period.
+        error (str): The period specification format error, or
+                     None on success.
     """
+    spec = None
     start = None
     end = None
+    description = None
+    error = None
 
     def __init__(self, period_spec):
-        self.start = period_spec + "-01"
-        self.end = period_spec + "-30"
+        self.spec = period_spec
+        # A specific month
+        m = re.match("^([0-9]{4})-([0-9]{2})$", period_spec)
+        if m is not None:
+            try:
+                year = int(m.group(1))
+                month = int(m.group(2))
+                self.set_month_range(year, month)
+                self.description = self.get_month_description(
+                    year, month)
+            except ValueError:
+                self.invalid_period()
+            return
+        # From a specific month
+        m = re.match("^([0-9]{4})-([0-9]{2})-$", period_spec)
+        if m is not None:
+            try:
+                year = int(m.group(1))
+                month = int(m.group(2))
+                self.start = date(year, month, 1)
+                self.end = self.get_month_last_day(localdate())
+                self.description = gettext(
+                    "Since %s") % self.get_month_description(
+                    year, month)
+            except ValueError:
+                self.invalid_period()
+            return
+        # A specific year
+        m = re.match("^([0-9]{4})$", period_spec)
+        if m is not None:
+            try:
+                year = int(m.group(1))
+                self.start = date(year, 1, 1)
+                self.end = date(year, 12, 31)
+                today = localdate()
+                if year == today.year:
+                    self.description = gettext("This Year")
+                elif year == today.year - 1:
+                    self.description = gettext("Last Year")
+                else:
+                    self.description = str(year)
+            except ValueError:
+                self.invalid_period()
+            return
+        # All time
+        if period_spec == "-":
+            self.start = date(2000, 1, 1)
+            self.end = self.get_month_last_day(localdate())
+            self.description = gettext("All")
+            return
+        # A specific date
+        m = re.match("^([0-9]{4})-([0-9]{2})-([0-9]{2})$",
+                     period_spec)
+        if m is not None:
+            try:
+                self.start = date(
+                    int(m.group(1)), int(m.group(2)), int(m.group(3)))
+                self.end = self.start
+                today = localdate()
+                if self.start == today:
+                    self.description = gettext("Today")
+                elif self.start == today - timedelta(days=1):
+                    self.description = gettext("Yesterday")
+                elif self.start.year != today.year:
+                    self.description = defaultfilters.date(
+                        self.start, "Y/n/j")
+                else:
+                    self.description = defaultfilters.date(
+                        self.start, "n/j")
+            except ValueError:
+                self.invalid_period()
+            return
+        # A specific date period
+        m = re.match(("^([0-9]{4})-([0-9]{2})-([0-9]{2})"
+                      "-([0-9]{4})-([0-9]{2})-([0-9]{2})$"),
+                     period_spec)
+        if m is not None:
+            try:
+                self.start = date(
+                    int(m.group(1)), int(m.group(2)), int(m.group(3)))
+                self.end = date(
+                    int(m.group(4)), int(m.group(5)), int(m.group(6)))
+                today = localdate()
+                if self.start.year != self.end.year:
+                    self.description = "%s-%s" % (
+                        defaultfilters.date(self.start, "Y/n/j"),
+                        defaultfilters.date(self.end, "Y/n/j"))
+                elif self.start.month != self.end.month:
+                    if self.start.year != today.year:
+                        self.description = "%s-%s" % (
+                            defaultfilters.date(self.start, "Y/n/j"),
+                            defaultfilters.date(self.end, "n/j"))
+                    else:
+                        self.description = "%s-%s" % (
+                            defaultfilters.date(self.start, "n/j"),
+                            defaultfilters.date(self.end, "n/j"))
+                else:
+                    if self.start.year != today.year:
+                        self.description = "%s-%s" % (
+                            defaultfilters.date(self.start, "Y/n/j"),
+                            defaultfilters.date(self.end, "j"))
+                    else:
+                        self.description = "%s-%s" % (
+                            defaultfilters.date(self.start, "n/j"),
+                            defaultfilters.date(self.end, "j"))
+            except ValueError:
+                self.invalid_period()
+        # Wrong period format
+        self.invalid_period()
 
+    def invalid_period(self):
+        """Sets the period when the period specification is invalid.
+        """
+        self.error = pgettext("Accounting|", "Invalid period.")
+        today = localdate()
+        self.spec = dateformat.format(localdate(), "Y-m")
+        self.set_month_range(today.year, today.month)
+        self.description = gettext("This Month")
 
+    def set_month_range(self, year, month):
+        """Calculates and returns the date range of a month.
+
+        Args:
+            year (int): The year.
+            month (int): The month.
+
+        Returns:
+            tuple(date): The date range of the month.
+
+        Throws:
+            ValueError: When the year and month are invalid
+        """
+        self.start = date(year, month, 1)
+        self.end = self.get_month_last_day(self.start)
+
+    @staticmethod
+    def get_month_last_day(day):
+        """Calculates and returns the last day of a month.
+
+        Args:
+            day (date): A day in the month.
+
+        Returns:
+            date: The last day in the month
+        """
+        next_month = day.month + 1
+        next_year = day.year
+        if next_month > 12:
+            next_month = 1
+            next_year = next_year + 1
+        return date(next_year, next_month, 1) - timedelta(days=1)
+
+    @staticmethod
+    def get_month_description(year, month):
+        """Returns the text description of a month.
+
+        Args:
+            year (int): The year.
+            month (int): The month.
+
+        Returns:
+            str: The description of the month
+        """
+        today = localdate()
+        if year == today.year and month == today.month:
+            return gettext("This Month")
+        prev_month = today.month - 1
+        prev_year = today.year
+        if prev_month < 1:
+            prev_month = 12
+            prev_year = prev_year - 1
+        prev = date(prev_year, prev_month, 1)
+        if year == prev.year and month == prev.month:
+            return gettext("Last Month")
+        return "%d/%d" % (year, month)