# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1439672339 -7200
# Node ID e43d62cc38328842e051624fc7b669e2fc677d39
# Parent  7a2cf3dead31215aa0c328657c0e661922cb2bd3
Added functions for coalescing and inverting free/busy information.
Made separate functions for obtaining periods before and from a given point.

diff -r 7a2cf3dead31 -r e43d62cc3832 imiptools/period.py
--- a/imiptools/period.py	Sat Aug 15 22:57:17 2015 +0200
+++ b/imiptools/period.py	Sat Aug 15 22:58:59 2015 +0200
@@ -348,6 +348,20 @@
 
         found += 1
 
+def periods_from(freebusy, period):
+
+    "Return the entries in 'freebusy' at or after 'period'."
+
+    first = bisect_left(freebusy, period)
+    return freebusy[first:]
+
+def periods_until(freebusy, period):
+
+    "Return the entries in 'freebusy' before 'period'."
+
+    last = bisect_right(freebusy, Period(period.get_end(), period.get_end(), period.get_tzid()))
+    return freebusy[:last]
+
 def get_overlapping(freebusy, period):
 
     """
@@ -358,8 +372,7 @@
     # Find the range of periods potentially overlapping the period in the
     # free/busy collection.
 
-    last = bisect_right(freebusy, Period(period.get_end(), period.get_end(), period.tzid))
-    startpoints = freebusy[:last]
+    startpoints = periods_until(freebusy, period)
 
     # Find the range of periods potentially overlapping the period in a version
     # of the free/busy collection sorted according to end datetimes.
@@ -415,6 +428,62 @@
     for replacement in replacements:
         insert_period(freebusy, replacement)
 
+def get_free_periods(freebusy, period, overlapping=False):
+
+    """
+    Return periods from 'freebusy' within which the given 'period' could be
+    inserted. If 'overlapping' is true, only return free periods that overlap
+    'period'.
+    """
+
+    free = invert_freebusy(freebusy)
+    if not free:
+        return None
+
+    if overlapping:
+        return get_overlapping(free, period)
+    else:
+        return free
+
+def coalesce_freebusy(freebusy):
+
+    "Coalesce the periods in 'freebusy'."
+
+    if not freebusy:
+        return freebusy
+
+    fb = []
+    start = freebusy[0].get_start_point()
+    end = freebusy[0].get_end_point()
+
+    for period in freebusy[1:]:
+        if period.get_start_point() > end:
+            fb.append(FreeBusyPeriod(start, end))
+            start = period.get_start_point()
+            end = period.get_end_point()
+        else:
+            end = max(end, period.get_end_point())
+
+    fb.append(FreeBusyPeriod(start, end))
+    return fb
+
+def invert_freebusy(freebusy):
+
+    "Return the free periods from 'freebusy'."
+
+    if not freebusy:
+        return None
+
+    fb = coalesce_freebusy(freebusy)
+    free = []
+    start = fb[0].get_end_point()
+
+    for period in fb[1:]:
+        free.append(FreeBusyPeriod(start, period.get_start_point()))
+        start = period.get_end_point()
+
+    return free
+
 # Period layout.
 
 def get_scale(periods, tzid):