Prototype compressed event listing

5 files changed, 272 insertions, 96 deletions

diff --git a/src/ImmutGrowVector.hs b/src/ImmutGrowVector.hs
index d36209d..ee38bc4 100644
--- a/src/ImmutGrowVector.hs
+++ b/src/ImmutGrowVector.hs
@@ -1,43 +1,47 @@
 module ImmutGrowVector where
 
-import Foreign.Storable
-import Data.Vector.Storable qualified as VS
+import Data.Vector.Unboxed (Unbox)
+import Data.Vector.Unboxed qualified as VU
 
 
 -- | Acts like an immutable storable vector, except that it's split in a long
 -- prefix and a short suffix so that modifications at the end are cheap. If the
 -- suffix gets longer (by appending elements), the suffix elements are promoted
 -- to prefix elements once in a while, resulting in a big copy at those times.
-data ImmutGrowVector a = ImmutGrowVector (VS.Vector a) (VS.Vector a)
+data ImmutGrowVector a = ImmutGrowVector (VU.Vector a) (VU.Vector a)
   deriving (Show)
 
-empty :: Storable a => ImmutGrowVector a
-empty = ImmutGrowVector VS.empty VS.empty
+empty :: Unbox a => ImmutGrowVector a
+empty = ImmutGrowVector VU.empty VU.empty
 
-fromListN :: Storable a => Int -> [a] -> ImmutGrowVector a
+fromListN :: Unbox a => Int -> [a] -> ImmutGrowVector a
 fromListN n l
   | n > 2 =
       let (l1, l2) = splitAt (n - 2) l
-      in ImmutGrowVector (VS.fromListN (n - 2) l1) (VS.fromListN 2 l2)
+      in ImmutGrowVector (VU.fromListN (n - 2) l1) (VU.fromListN 2 l2)
   | otherwise =
-      ImmutGrowVector VS.empty (VS.fromListN n l)
+      ImmutGrowVector VU.empty (VU.fromListN n l)
 
-(!) :: Storable a => ImmutGrowVector a -> Int -> a
+(!) :: Unbox a => ImmutGrowVector a -> Int -> a
 ImmutGrowVector prefix suffix ! i
-  | i < VS.length prefix = prefix VS.! i
-  | otherwise = suffix VS.! (i - VS.length prefix)
+  | i < VU.length prefix = prefix VU.! i
+  | otherwise = suffix VU.! (i - VU.length prefix)
 
-length :: Storable a => ImmutGrowVector a -> Int
-length (ImmutGrowVector prefix suffix) = VS.length prefix + VS.length suffix
+length :: Unbox a => ImmutGrowVector a -> Int
+length (ImmutGrowVector prefix suffix) = VU.length prefix + VU.length suffix
 
-set :: Storable a => ImmutGrowVector a -> Int -> a -> ImmutGrowVector a
+set :: Unbox a => ImmutGrowVector a -> Int -> a -> ImmutGrowVector a
 set (ImmutGrowVector prefix suffix) idx value
-  | idx < VS.length prefix = error "ImmutGrowVector: mutation in slow part"
-  | otherwise = ImmutGrowVector prefix (suffix VS.// [(idx - VS.length prefix, value)])
+  | idx < VU.length prefix = error "ImmutGrowVector: mutation in slow part"
+  | otherwise = ImmutGrowVector prefix (suffix VU.// [(idx - VU.length prefix, value)])
 
-append :: Storable a => ImmutGrowVector a -> a -> ImmutGrowVector a
+append :: Unbox a => ImmutGrowVector a -> a -> ImmutGrowVector a
 append (ImmutGrowVector prefix suffix) value
-  | VS.length suffix < 8 = ImmutGrowVector prefix (suffix `VS.snoc` value)
+  | VU.length suffix < 8 = ImmutGrowVector prefix (suffix `VU.snoc` value)
   | otherwise =
-      let n = VS.length suffix
-      in ImmutGrowVector (prefix <> VS.take (n - 1) suffix) (VS.drop (n - 1) suffix `VS.snoc` value)
+      let n = VU.length suffix
+      in ImmutGrowVector (prefix <> VU.take (n - 1) suffix) (VU.drop (n - 1) suffix `VU.snoc` value)
+
+-- | Transform the vector by mapping the underlying unboxed vectors
+mapUVector :: (VU.Vector a -> VU.Vector b) -> ImmutGrowVector a -> ImmutGrowVector b
+mapUVector f (ImmutGrowVector prefix suffix) = ImmutGrowVector (f prefix) (f suffix)
diff --git a/src/Index.hs b/src/Index.hs
index 94c3f9e..3703f65 100644
--- a/src/Index.hs
+++ b/src/Index.hs
@@ -1,10 +1,17 @@
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE ViewPatterns #-}
 module Index (
   Index,
   EventID,
+  CountKind(..),
   initIndex,
   indexGetEventsLinear,
   findEventIDLinear,
@@ -25,14 +32,19 @@ import Data.ByteString (ByteString)
 import Data.Char (isDigit, chr, ord)
 import Data.Functor ((<&>))
 import Data.IORef
-import Data.List (sort, scanl', foldl', minimumBy)
+import Data.List (sort, scanl', foldl', minimumBy, intercalate)
 import Data.Map.Strict (Map)
 import Data.Map.Strict qualified as Map
 import Data.Maybe (catMaybes)
+import Data.Monoid (Endo(..))
 import Data.Ord (comparing)
 import Data.Text qualified as T
 import Data.Text (Text)
 import Data.Time
+import Data.Vector.Generic qualified as VG
+import Data.Vector.Generic.Mutable qualified as VGM
+import Data.Vector.Unboxed qualified as VU
+import Data.Vector.Unboxed.Base qualified as VU (Vector(V_2))
 import Data.Vector.Storable qualified as VS
 import Data.Word
 import System.Clock qualified as Clock
@@ -52,10 +64,62 @@ import Util
 import ZNC
 
 
+-- This module keeps an index both for the full list of events, as well as a
+-- /compressed/ list of events. Compression here means that sequences of events
+-- with type not in a list of "important" events (see 'isImportant') are
+-- compressed into a single pseudo-event, recording the existence of
+-- unimportant events but not their details. This compression happens within a
+-- single UTC day, so if there is a sequence of unimportant events crossing a
+-- UTC day boundary, the compressed stream will have two compressed events.
+-- Ideally these would also be compressed but that would complicate the code.
+--
+-- The 'Counts' data type represents the number of events in a particular time
+-- period, as counted in each of the tracked ways (two for now).
+
+
+data CountKind = CKAll | CKCompressed
+  deriving (Show, Eq)
+
+data Counts = Counts { coAll :: {-# UNPACK #-} !Int
+                     , coCmpr :: {-# UNPACK #-} !Int }
+  deriving (Show, Eq)
+
+instance Num Counts where
+  Counts a i + Counts a' i' = Counts (a + a') (i + i')
+  Counts a i - Counts a' i' = Counts (a - a') (i - i')
+  (*) = error "(*) on Counts"
+  abs = error "abs on Counts"
+  signum = error "signum on Counts"
+  fromInteger 0 = Counts 0 0
+  fromInteger _ = error "non-zero fromInteger on Counts"
+
+instance VU.IsoUnbox Counts (Int, Int) where
+  toURepr (Counts a i) = (a, i) ; {-# INLINE toURepr #-}
+  fromURepr (a, i) = Counts a i ; {-# INLINE fromURepr #-}
+newtype instance VU.MVector s Counts = MV_Counts (VU.MVector s (Int, Int))
+newtype instance VU.Vector    Counts = V_Counts  (VU.Vector    (Int, Int))
+deriving via (Counts `VU.As` (Int, Int)) instance VGM.MVector VU.MVector Counts
+deriving via (Counts `VU.As` (Int, Int)) instance VG.Vector   VU.Vector  Counts
+instance VU.Unbox Counts
+
+getCount :: CountKind -> Counts -> Int
+getCount CKAll = coAll
+getCount CKCompressed = coCmpr
+
+getCountVector :: CountKind -> VU.Vector Counts -> VU.Vector Int
+getCountVector kind (V_Counts (VU.V_2 _ vAll vCmpr)) =
+  case kind of
+    CKAll -> vAll
+    CKCompressed -> vCmpr
+
+
+-- | The index for a single channel.
 data ChanIndex = ChanIndex
   { ciStartDay :: !Day
-  , ciCountUntil :: !(IGV.ImmutGrowVector Int)  -- ^ number of events up to and /including/ this day
-  , ciTotal :: !Int }
+  , ciCountUntil :: !(IGV.ImmutGrowVector Counts)
+      -- ^ Number of events up to and /including/ this day. Values:
+      -- (all events, compressed events).
+  , ciTotal :: !Counts }
   deriving (Show)
 
 -- | Inclusive.
@@ -87,6 +151,7 @@ initIndex basedir toimport = do
   c_start <- Clock.getTime Clock.Realtime
   items <-
     forM toimport $ \(Channel nwT chT) -> do
+      atomicPrint $ "Indexing " <> nwT <> "/" <> chT
       let nw = T.unpack nwT
           ch = T.unpack chT
       files <- listDirectory (basedir </> nw </> ch)
@@ -98,13 +163,15 @@ initIndex basedir toimport = do
         -- atomicPrintS $ "Parsing " ++ path ++ " (" ++ show date ++ " -> " ++ show (dateToDay date) ++ ")"
         events <- parseLog <$> BS.readFile path
         let !nevents = length events
-        return (uncurry3 fromGregorian date, nevents)
-      let minday = minimum (map fst days)
-          maxday = maximum (map fst days)
+            !ccpr = countCompressed (map snd events)
+        return (uncurry3 fromGregorian date, nevents, ccpr)
+      let minday = minimum [day | (day, _, _) <- days]
+          maxday = maximum [day | (day, _, _) <- days]
           ndays = fromIntegral @Integer @Int (diffDays maxday minday + 1)
       -- traceM $ nw ++ "/" ++ ch ++ ": days = " ++ show [(toFileName (dayToYMD d), i) | (d, i) <- days]
-      let countScan = IGV.fromListN ndays (drop 1 $ scanl' (+) 0 (makeCounts [minday..maxday] days))
-          ntotal = sum (map snd days)
+      let daysEvents = [(day, Counts nev ncompr) | (day, nev, ncompr) <- days]
+          countScan = IGV.fromListN ndays (drop 1 $ scanl' (+) 0 (makeCounts [minday..maxday] daysEvents))
+          ntotal = sum [Counts nev ncompr | (_, nev, ncompr) <- days]
       chanindex <- newIORef $!
         ChanIndex { ciStartDay = minday
                   , ciCountUntil = countScan
@@ -150,7 +217,7 @@ initIndex basedir toimport = do
 
   return index
 
-makeCounts :: [Day] -> [(Day, Int)] -> [Int]
+makeCounts :: Num a => [Day] -> [(Day, a)] -> [a]
 makeCounts [] [] = []
 makeCounts [] _ = error "makeCounts: more entries than days in range"
 makeCounts (d:ds) ents@((d',n):ents')
@@ -159,6 +226,56 @@ makeCounts (d:ds) ents@((d',n):ents')
   | otherwise = error $ "makeCounts: duplicate entry? " ++ show (d, toGregorian d, d', toGregorian d')
 makeCounts (_:ds) [] = 0 : makeCounts ds []
 
+countCompressed :: [Event] -> Int
+countCompressed = goI 0
+  where
+    goI !n [] = n
+    goI n (e:es)
+      | isImportant e = goI (n+1) es
+      | otherwise = goU n es
+
+    goU !n [] = n + 1  -- 1 for the unimportant sequence
+    goU n (e:es)
+      | isImportant e = goI (n+2) es  -- 1 for the unimportant sequence, 1 for this important event
+      | otherwise = goU n es
+
+-- | Compresses every sequence of unimportant events down to one event, with
+-- the tag of the first in the sequence.
+compressEvents :: [(a, Event)] -> [(a, Event)]
+compressEvents [] = []
+compressEvents events =
+  let (evsU, evs1) = break (isImportant . snd) events
+      (evsI, evs2) = span (isImportant . snd) evs1
+      tl = evsI ++ compressEvents evs2
+  in case evsU of
+       (tag, e) : ps -> (tag, compress (e : map snd ps)) : tl
+       [] -> tl
+  where
+    compress :: [Event] -> Event
+    compress = Compressed . describe . (`appEndo` CompressedCount 0 0 0 0) . foldMap (Endo . collect)
+
+    collect :: Event -> CompressedCount -> CompressedCount
+    collect Join{} = \cc -> cc { ccJoins = ccJoins cc + 1 }
+    collect Part{} = \cc -> cc { ccLeaves = ccLeaves cc + 1 }
+    collect Quit{} = \cc -> cc { ccLeaves = ccLeaves cc + 1 }
+    collect Mode{} = \cc -> cc { ccModes = ccModes cc + 1 }
+    collect ParseError{} = \cc -> cc { ccParseErrors = ccParseErrors cc + 1 }
+    collect _ = id
+
+    describe :: CompressedCount -> Text
+    describe (CompressedCount nj nl nm np) =
+      T.pack $ intercalate ", " $
+        [show nj ++ " joined" | nj > 0] ++
+        [show nl ++ " left" | nl > 0] ++
+        [show nm ++ " set a mode" | nm > 0] ++
+        [show np ++ " parse errors" | np > 0]
+
+data CompressedCount = CompressedCount
+  { ccJoins :: Int
+  , ccLeaves :: Int
+  , ccModes :: Int
+  , ccParseErrors :: Int }
+
 indexUpdateImport :: Index -> Channel -> IO ()
 indexUpdateImport index@(Index _ mp _) chan = do
   let ciRef = mp Map.! chan
@@ -172,50 +289,55 @@ indexUpdateImport index@(Index _ mp _) chan = do
         dayidx = fromIntegral @Integer @Int (day `diffDays` ciStartDay ci)
 
     loadDay index chan ymd >>= \case
-      Just (_bs, lineStarts) -> return (Just (dayidx, VS.length lineStarts))
+      Just (bs, lineStarts) ->
+        return (Just (dayidx, Counts (VS.length lineStarts) (countCompressed (map snd (parseLog bs)))))
       Nothing -> return Nothing
 
   atomicPrint $ "Update import for " <> prettyChannel chan <> ": " <> T.show readCounts <> " (len = " <> T.show (IGV.length (ciCountUntil ci)) <> ")"
 
   when (not (null readCounts)) $
     atomicModifyIORef' ciRef $ \ci' ->
-      let ciRes = foldl' (\ci2 (dayidx, count) -> recordCount ci2 dayidx count) ci' readCounts
+      let ciRes = foldl' (\ci2 (dayidx, counts) -> recordCounts ci2 dayidx counts) ci' readCounts
       in (ciRes, ())
   where
     -- | How many events do we already have on this day?
-    eventsOnDayIdx :: ChanIndex -> Int -> Int
+    eventsOnDayIdx :: ChanIndex -> Int -> Counts
     eventsOnDayIdx ci dayidx
       | dayidx == 0 = scan IGV.! 0
       | dayidx < IGV.length scan = scan IGV.! dayidx - scan IGV.! (dayidx - 1)
       | otherwise = 0
       where scan = ciCountUntil ci
 
-    recordCount :: ChanIndex -> Int -> Int -> ChanIndex
-    recordCount ci dayidx count
-      | count <= alreadyHave = ci
+    recordCounts :: ChanIndex -> Int -> Counts -> ChanIndex
+    recordCounts ci dayidx counts
+      | counts == alreadyHave = ci
       | otherwise =
-          let ciExt =  -- Ensure that there is space in the scan vector for our record
-                let nExtraDays = dayidx - IGV.length (ciCountUntil ci) + 1
-                    lastCount | IGV.length (ciCountUntil ci) == 0 = 0
-                              | otherwise = ciCountUntil ci IGV.! (IGV.length (ciCountUntil ci) - 1)
+          let ciExt =
+                -- Ensure that there is space in the scan vector for our record
+                -- by copying the last entry a few times
+                let currentLen = IGV.length (ciCountUntil ci)
+                    nExtraDays = dayidx - currentLen + 1
+                    lastCount | currentLen == 0 = 0
+                              | otherwise = ciCountUntil ci IGV.! (currentLen - 1)
                 in ci { ciCountUntil = iterate (`IGV.append` lastCount) (ciCountUntil ci) !! nExtraDays }
-              addFrom di n vec
-                | di < IGV.length vec = addFrom (di + 1) n (IGV.set vec di (vec IGV.! di + n))
-                | otherwise = vec
-          in ciExt { ciCountUntil = addFrom dayidx (count - alreadyHave) (ciCountUntil ciExt)
-                   , ciTotal = ciTotal ciExt + count - alreadyHave }
+              addFrom di n vec =
+                foldl' (\vec' di' -> IGV.set vec' di' (vec' IGV.! di' + n))
+                       vec [di .. IGV.length vec - 1]
+          in ciExt { ciCountUntil = addFrom dayidx (counts - alreadyHave) (ciCountUntil ciExt)
+                   , ciTotal = ciTotal ciExt + counts - alreadyHave }
       where alreadyHave = eventsOnDayIdx ci dayidx
 
 -- search
 
 -- | Returns proper lazy list of events. Reading the files happens strictly,
 -- but parsing the events happens lazily.
-indexGetEventsLinear :: Index -> Channel -> Int -> Int -> IO [(YMDHMS, EventID, Event)]
-indexGetEventsLinear index@(Index _ mp _) chan from count = do
+indexGetEventsLinear :: Index -> Channel -> CountKind -> Int -> Int -> IO [(YMDHMS, EventID, Event)]
+indexGetEventsLinear index@(Index _ mp _) chan kind from count = do
+  atomicPrintS $ "indexGetEventsLinear " ++ show chan ++ " " ++ show kind ++ " " ++ show from ++ " " ++ show count
   ci <- readIORef (mp Map.! chan)
-  if from + count < 0 || from >= ciTotal ci
+  if from + count < 0 || from >= getCount kind (ciTotal ci)
     then return []
-    else go ci (ciCountUntil ci)
+    else go ci (IGV.mapUVector (getCountVector kind) (ciCountUntil ci))
   where
     go ci scan = do
       let day1idx = binSearch scan from
@@ -241,34 +363,36 @@ indexGetEventsLinear index@(Index _ mp _) chan from count = do
                         nOnDay2 = scan IGV.! day2idx - nbefore
                 in loop (day1idx + 1) (neventBeforeDay1 + neventOnDay1) (neventOnDay1 - off1)
 
-      -- traceM ("ci = " ++ show ci)
-      -- traceM ("binSearch " ++ show from ++ " =")
-      -- traceM ("  " ++ show day1idx)
-      -- traceM ("day1 = " ++ show day1)
-      -- traceM ("off1 = " ++ show off1)
-      -- traceM ("neventOnDay1 = " ++ show neventOnDay1)
-      -- traceM ("count = " ++ show count)
-      -- traceM ("day2 = " ++ show day2)
-      -- traceM ("off2 = " ++ show off2)
+      -- atomicPrintS ("ci = " ++ show ci)
+      -- atomicPrintS ("binSearch " ++ show from ++ " =")
+      -- atomicPrintS ("  " ++ show day1idx)
+      -- atomicPrintS ("day1 = " ++ show day1)
+      -- atomicPrintS ("off1 = " ++ show off1)
+      -- atomicPrintS ("neventOnDay1 = " ++ show neventOnDay1)
+      -- atomicPrintS ("count = " ++ show count)
+      -- atomicPrintS ("day2 = " ++ show day2)
+      -- atomicPrintS ("off2 = " ++ show off2)
       evs <- forM (zip [day1 .. day2] [day1idx..]) $ \(day, dayidx) ->
-               let neventsOnDay | dayidx == 0 = scan IGV.! 0
-                                | otherwise = scan IGV.! dayidx - scan IGV.! (dayidx - 1)
-                   range
-                     | day == day1 =
-                         if day1 == day2
-                           then (off1, Just (off2 - off1))
-                           else (off1, Just (neventsOnDay - off1))
-                     | day == day2 = (0, Just off2)
-                     | otherwise = (0, Just neventsOnDay)
-                   ymd = ymdFromGregorian (toGregorian day)
-               in if neventsOnDay > 0
-                    then loadDay index chan ymd <&> \case
-                           Just (bs, lineStarts) ->
-                             let events = parseLogRange range lineStarts bs
-                             in zipWith (\(hms, ev) off -> (YMDHMS ymd hms, genEventID (YMDHMS ymd hms) off, ev))
-                                        events [fst range ..]
-                           Nothing -> error $ "events on day " ++ show (dayToYMD day) ++ " but no file"
-                    else return []
+        let neventsOnDay | dayidx == 0 = scan IGV.! 0
+                         | otherwise = scan IGV.! dayidx - scan IGV.! (dayidx - 1)
+            rangeStart = if day == day1 then off1 else 0
+            rangeEnd = if day == day2 then off2 else neventsOnDay
+            range = (rangeStart, Just (rangeEnd - rangeStart))
+            ymd = ymdFromGregorian (toGregorian day)
+        in if neventsOnDay > 0
+             then loadDay index chan ymd <&> \case
+                    Just (bs, lineStarts) -> case kind of
+                      CKAll ->
+                        let events = parseLogRange range lineStarts bs
+                        in [(YMDHMS ymd hms, genEventID (YMDHMS ymd hms) off, ev)
+                           | ((hms, ev), off) <- zip events [rangeStart ..]]
+                      CKCompressed ->
+                        let events = parseLog bs
+                            events' = take (rangeEnd - rangeStart) $ drop rangeStart $
+                                        compressEvents [((hms, off), ev) | ((hms, ev), off) <- zip events [0..]]
+                        in [(YMDHMS ymd hms, genEventID (YMDHMS ymd hms) off, ev) | ((hms, off), ev) <- events']
+                    Nothing -> error $ "events on day " ++ show (dayToYMD day) ++ " but no file"
+             else return []
 
       return (concat evs)
 
@@ -299,8 +423,8 @@ binSearch vec needle
 -- - Timestamp of the event
 -- - Index in the linear list of events for this channel
 -- - Index in the list of events in the channel on that day
-findEventIDLinear :: Index -> Channel -> EventID -> IO (Maybe (YMDHMS, Int, Int))
-findEventIDLinear index@(Index _ mp _) chan eid = runMaybeT $ do
+findEventIDLinear :: Index -> Channel -> CountKind -> EventID -> IO (Maybe (YMDHMS, Int, Int))
+findEventIDLinear index@(Index _ mp _) chan kind eid = runMaybeT $ do
   (ymdhms@(YMDHMS ymd hms), idoff) <- hoistMaybe (parseEventID eid)
   day <- hoistMaybe (uncurry3 fromGregorianValid (ymdToGregorian ymd))
 
@@ -308,24 +432,29 @@ findEventIDLinear index@(Index _ mp _) chan eid = runMaybeT $ do
   guard (ciStartDay ci <= day && day <= ciEndDay ci)
 
   (bs, lineStarts) <- MaybeT $ loadDay index chan ymd
-  let candidates =
+  let candidates =  -- [(event offset, index in possibly compressed event list)]
         map snd $
         takeWhile ((== hms) . fst) $
         dropWhile ((< hms) . fst) $
-        zip (parseLogTimesOnly lineStarts bs) [0..]
+        case kind of
+          CKAll -> zip (parseLogTimesOnly lineStarts bs) (zip [0..] [0..])
+          CKCompressed ->
+            let compressed = compressEvents [((hms', off), ev)
+                                            | ((hms', ev), off) <- zip (parseLog bs) [0..]]
+            in [(hms', (off, idx)) | (((hms', off), _ev), idx) <- zip compressed [0..]]
   case candidates of
     [] -> empty
     _ -> do
       let dayidx = fromIntegral @Integer @Int (day `diffDays` ciStartDay ci)
           eventsBeforeDay | dayidx == 0 = 0
-                          | otherwise = ciCountUntil ci IGV.! (dayidx - 1)
-      let dayoff = minimumBy (comparing (\off -> abs (off - idoff))) candidates
-      return (ymdhms, eventsBeforeDay + dayoff, dayoff)
+                          | otherwise = getCount kind (ciCountUntil ci IGV.! (dayidx - 1))
+      let (_dayoff, daylistidx) = minimumBy (comparing (\(off, _listidx) -> abs (off - idoff))) candidates
+      return (ymdhms, eventsBeforeDay + daylistidx, daylistidx)
 
 -- other methods
 
-indexNumEvents :: Index -> Channel -> IO Int
-indexNumEvents (Index _ mp _) chan = ciTotal <$> readIORef (mp Map.! chan)
+indexNumEvents :: Index -> Channel -> CountKind -> IO Int
+indexNumEvents (Index _ mp _) chan kind = getCount kind . ciTotal <$> readIORef (mp Map.! chan)
 
 indexCalendar :: Index -> Channel -> IO ((Day, Day), [Int])
 indexCalendar (Index _ mp _) chan = do
@@ -333,12 +462,12 @@ indexCalendar (Index _ mp _) chan = do
   let scan = ciCountUntil ci
   return ((ciStartDay ci, ciEndDay ci)
          ,[if i == 0
-             then scan IGV.! 0
-             else scan IGV.! i - scan IGV.! (i - 1)
+             then coAll (scan IGV.! 0)
+             else coAll (scan IGV.! i) - coAll (scan IGV.! (i - 1))
           | i <- [0 .. IGV.length scan - 1]])
 
-indexGetEventsDay :: Index -> Channel -> Day -> IO [(HMS, EventID, Event)]
-indexGetEventsDay index@(Index _ mp _) chan day = do
+indexGetEventsDay :: Index -> Channel -> CountKind -> Day -> IO [(HMS, EventID, Event)]
+indexGetEventsDay index@(Index _ mp _) chan kind day = do
   ci <- readIORef (mp Map.! chan)
   let ymd = dayToYMD day
   if day < ciStartDay ci || day > ciEndDay ci
@@ -346,8 +475,14 @@ indexGetEventsDay index@(Index _ mp _) chan day = do
     else loadDay index chan ymd <&> \case
            Just (bs, _lineStarts) ->
              let events = parseLog bs
-             in zipWith (\(hms, ev) off -> (hms, genEventID (YMDHMS ymd hms) off, ev))
-                        events [0..]
+             in case kind of
+                  CKAll ->
+                    [(hms, genEventID (YMDHMS ymd hms) off, ev)
+                    | ((hms, ev), off) <- zip events [0..]]
+                  CKCompressed ->
+                    [(hms, genEventID (YMDHMS ymd hms) off, ev)
+                    | ((hms, off), ev) <- compressEvents [((hms, off), ev)
+                                                         | ((hms, ev), off) <- zip events [0..]]]
            Nothing -> []  -- if the file doesn't exist, there ain't no events
 
 -- utilities
@@ -364,6 +499,22 @@ loadDay (Index basedir _ cache) chan@(Channel network channel) ymd = do
         Nothing -> return Nothing  -- file didn't exist
     Just (bs, lineStarts) -> return (Just (bs, lineStarts))
 
+isImportant :: Event -> Bool
+isImportant ReNick{} = True
+isImportant Talk{} = True
+isImportant Notice{} = True
+isImportant Act{} = True
+isImportant Kick{} = True
+isImportant Topic{} = True
+
+isImportant Join{} = False
+isImportant Part{} = False
+isImportant Quit{} = False
+isImportant Mode{} = False
+isImportant ParseError{} = False
+
+isImportant Compressed{} = error "isImportant: why am I getting a compressed event"
+
 -- | Takes the index of the event in the day's log (the "offset") in addition
 -- to the timestamp, in order to disambiguate in case there are multiple events
 -- with the same timestamp.
diff --git a/src/Main.hs b/src/Main.hs
index 5739065..246b5d3 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE ViewPatterns #-}
 module Main (main) where
 
+import Control.Applicative ((<|>))
 import Control.Monad (guard, forM_)
 import Data.ByteString (ByteString)
 import Data.ByteString qualified as BS
@@ -63,12 +64,17 @@ pageLog conf index req alias =
   case econfAlias2Chan conf Map.!? alias of
     Nothing -> sendText404 "Channel not found"
     Just chan -> do
-      numEvents <- indexNumEvents index chan
+      let (kind, kindCookie) =
+            case query req "ef" <|> cookie req "ef" of  -- event filter
+              Just "all" -> (CKAll, Just "ef=all")
+              Just "compr" -> (CKCompressed, Just "ef=compr")
+              _ -> (CKAll, Nothing)
+      numEvents <- indexNumEvents index chan kind
       let npages = (numEvents + numPerPage - 1) `div` numPerPage
       (mcurpage, mpagehighlight) <-
         if | Just (readMaybe . BS8.unpack -> Just pg) <- query req "page" -> return (Just (min npages (max 1 pg)), Nothing)
            | Just (TE.decodeASCII' -> Just eventID) <- query req "eid" -> do
-               mevidx <- findEventIDLinear index chan eventID
+               mevidx <- findEventIDLinear index chan kind eventID
                case mevidx of
                  Just (_, evidx, _) -> return (Just (evidx `div` numPerPage + 1), Just (evidx `mod` numPerPage))
                  Nothing -> return (Nothing, Nothing)
@@ -79,13 +85,17 @@ pageLog conf index req alias =
           let ntoleft = min 5 (curpage - 1)
               ntoright = min 5 (npages - curpage)
           -- traceShowM (indexNumEvents index chan, npages, curpage, ntoleft, ntoright)
-          events <- indexGetEventsLinear index chan ((curpage - 1) * numPerPage) numPerPage
-          sendHtml200 $
+          events <- indexGetEventsLinear index chan kind ((curpage - 1) * numPerPage) numPerPage
+          let headers = [("Content-Type", "text/html")] ++
+                        maybe [] (\s -> [("Set-Cookie", s)]) kindCookie
+          return $ responseBS status200 headers $
             renderPageLog LogData
               { network = chanNetwork chan
               , channel = chanChannel chan
               , alias = alias
               , totalevents = renderLargeNumber numEvents
+              , efAll = kind == CKAll
+              , efCompr = kind == CKCompressed
               , picker = PickerData
                   { prevpage = if curpage > 1 then Just (curpage - 1) else Nothing
                   , nextpage = if curpage < npages then Just (curpage + 1) else Nothing
@@ -130,10 +140,14 @@ pageCalendarDay conf index req alias datestr =
     (Nothing, _) -> sendText404 "Channel not found"
     (_, Nothing) -> sendText404 "Invalid date"
     (Just chan, Just day) -> do
-      events <- indexGetEventsDay index chan day
+      let kind = case query req "ef" of
+                   Just "all" -> CKAll
+                   Just "compr" -> CKCompressed
+                   _ -> CKAll
+      events <- indexGetEventsDay index chan kind day
       mpagehighlight <-
         if | Just (TE.decodeASCII' -> Just eventID) <- query req "eid" -> do
-               mevidx <- findEventIDLinear index chan eventID
+               mevidx <- findEventIDLinear index chan kind eventID
                case mevidx of
                  Just (YMDHMS ymd _, _, evdayidx)
                    | ymd == ymdFromGregorian (toGregorian day) ->
@@ -184,6 +198,9 @@ classListAdd (Just l) t = l <> " " <> t
 query :: Request -> ByteString -> Maybe ByteString
 query req key = lookup key (reqQuery req)
 
+cookie :: Request -> ByteString -> Maybe ByteString
+cookie req name = lookup name (reqCookies req)
+
 -- Returns: (classlist, (nickwrap1, nick, nickwrap2), message)
 renderEvent :: Event -> (Maybe Text, (Maybe Text, Text, Maybe Text), Text)
 renderEvent = \case
@@ -198,6 +215,7 @@ renderEvent = \case
   Mode n m         -> (j "ev-meta",   (no, n, no),       "sets mode " <> m)
   Topic n m        -> (j "ev-meta",   (no, n, no),       "sets topic to \"" <> m <> "\"")
   ParseError       -> (j "ev-parseerror", (no, "", no),  "<parse error>")
+  Compressed text  -> (j "ev-meta",   (no, "", no),      text)
   where no = Nothing; j = Just
 
 pageCalendar :: Config -> Index -> Text -> IO Response
diff --git a/src/Pages.hs b/src/Pages.hs
index 4e85cae..7b114a6 100644
--- a/src/Pages.hs
+++ b/src/Pages.hs
@@ -59,6 +59,8 @@ data LogData = LogData
   , channel :: Text
   , alias :: Text
   , totalevents :: Text
+  , efAll :: Bool
+  , efCompr :: Bool
   , picker :: PickerData
   , events :: [EventData () Text]
   }
diff --git a/src/ZNC.hs b/src/ZNC.hs
index 7cfeb72..502b272 100644
--- a/src/ZNC.hs
+++ b/src/ZNC.hs
@@ -39,6 +39,7 @@ data Event
   | Mode   Nick      Text  -- ^ User set mode on the channel.
   | Topic  Nick      Text  -- ^ Topic change.
   | ParseError
+  | Compressed Text  -- ^ Fake event generated when compressing multiple meta events in "Index"
   deriving (Show)
 
 -- | Returned vector has one entry for each line in the file, excepting the