seperate state handling logic

app/EpubParser.hs

@@ -3,15 +3,12 @@
 module EpubParser
     ( EpubAction
     , EpubEnv(..)
-    , AppState(..)
     , openEpub
     , getOpfPath
     , resolveSpine
     , getChapter
     , getChapterTitle
     , Tag(..)
-    , prepareView
-    , ChapterView(..)
     ) where
 
 import Codec.Archive.Zip (Archive, findEntryByPath, fromEntry, toArchive)
@@ -23,8 +20,7 @@ import Control.Monad.Reader (ReaderT, MonadReader(ask), liftIO)
 import Control.Monad.Except (runExceptT)
 import System.FilePath (takeDirectory, (</>), normalise)
 import Data.List (find)
-import Text.HTML.TagSoup (parseTags, innerText, Tag(..), renderTags)
-import Control.Concurrent.Async (Async)
+import Text.HTML.TagSoup (parseTags, innerText, Tag(..))
 import Codec.Epub.Parse (getSpine, getMetadata, getManifest)
 import qualified Codec.Epub.Data.Metadata as DMeta
 import qualified Codec.Epub.Data.Manifest as DMan
@@ -33,18 +29,6 @@ import qualified Data.ByteString.Base64 as B64
 
 type EpubAction a = ReaderT EpubEnv IO a
 
-data AppState = AppState
-  { cEnv    :: EpubEnv
-  , cIdx    :: Int
-  , zoomlvl :: Double
-  , cSpine  :: [FilePath]
-  , bTitle  :: T.Text
-  , cTags   :: Maybe [Tag T.Text]
-  , activeTask :: Maybe (Async ())
-  , cAllChapters :: [[Tag T.Text]]
-  , taskVersion :: Integer
-  }
-
 data EpubEnv = EpubEnv
   { archive   :: Archive
   , opfXml    :: String
@@ -54,12 +38,6 @@ data EpubEnv = EpubEnv
   , eManifest :: DMan.Manifest
   }
 
-data ChapterView = ChapterView
-    { viewTitle :: T.Text
-    , viewHtml  :: T.Text
-    , viewIdx   :: Int
-    }
-
 openEpub :: FilePath -> IO (Either String EpubEnv)
 openEpub path = do
   rawZip <- B.readFile path
@@ -172,13 +150,3 @@ getChapterTitle tags =
     ishding _                = False
     isclose n  (TagClose n') = n == n'
     isclose _ _              = False
-
-prepareView :: AppState -> Int -> Maybe ChapterView
-prepareView st index
-  | index < 0 || index >= length (cAllChapters st) = Nothing
-  | otherwise = Just $ ChapterView
-    { viewTitle = bTitle st <> " - " <> getChapterTitle tags
-    , viewHtml  = renderTags tags
-    , viewIdx   = index
-    }
-  where tags = cAllChapters st !! index

app/State.hs

@@ -0,0 +1,55 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module State where
+
+import qualified Data.Text as T
+import Text.HTML.TagSoup (Tag, renderTags)
+import Control.Concurrent.Async (Async)
+import EpubParser (EpubEnv, getChapterTitle)
+
+data ChapterView = ChapterView
+  { viewTitle :: T.Text,
+    viewHtml :: T.Text,
+    viewIdx :: Int
+  }
+
+data AppState = AppState
+  { cEnv :: EpubEnv,
+    cIdx :: Int,
+    zoomlvl :: Double,
+    cSpine :: [FilePath],
+    bTitle :: T.Text,
+    cAllChapters :: [[Tag T.Text]],
+    activeTask :: Maybe (Async ()),
+    taskVersion :: Integer,
+    cTags :: Maybe [Tag T.Text]
+  }
+
+-- loading template
+initialState :: EpubEnv -> AppState
+initialState env =
+  AppState
+    { cEnv = env,
+      cIdx = 0,
+      cTags = Nothing,
+      cSpine = [],
+      bTitle = "Svitak - Loading...",
+      zoomlvl = 1.0,
+      activeTask = Nothing,
+      cAllChapters = [],
+      taskVersion = 0
+    }
+
+-- prepare the data for the UI
+prepareView :: AppState -> Int -> Maybe ChapterView
+prepareView st index
+  | null (cAllChapters st) = Nothing
+  | index < 0 || index >= length (cAllChapters st) = Nothing
+  | otherwise =
+      let tags = cAllChapters st !! index
+       in Just $
+            ChapterView
+              { viewTitle = bTitle st <> " - " <> getChapterTitle tags,
+                viewHtml = renderTags tags,
+                viewIdx = index
+              }

app/UI.hs

@@ -17,8 +17,9 @@ import Control.Monad.Reader (runReaderT)
 import Control.Concurrent.STM (newTVarIO, readTVar, atomically, modifyTVar)
 import Control.Concurrent.Async (async)
 import Codec.Epub.Data.Metadata (metaTitles, titleType, titleText)
-import EpubParser (EpubEnv(..), AppState(..), resolveSpine, getChapter, prepareView, ChapterView(..))
+import EpubParser (EpubEnv(..), resolveSpine, getChapter)
 import Persistence (saveLastRead, loadLastRead)
+import State (AppState(..), ChapterView(..), initialState, prepareView)
 
 runApp :: EpubEnv -> IO ()
 runApp env' = do
@@ -26,19 +27,7 @@ runApp env' = do
 
     _ <- Gtk.on app #activate $ do
 
-        let loadingState = AppState 
-                { cEnv         = env'
-                , cIdx          = 0
-                , cTags        = Nothing
-                , cSpine       = [] 
-                , bTitle       = "Svitak - Loading..."
-                , zoomlvl      = 1.0 
-                , activeTask   = Nothing
-                , cAllChapters = [] 
-                , taskVersion  = 0
-                }
-
-        stateTVar <- newTVarIO loadingState
+        stateTVar <- newTVarIO (initialState env')
 
         window <- Gtk.applicationWindowNew app
         webView <- WebKit.webViewNew

svitak.cabal

@@ -53,7 +53,8 @@ executable svitak
 
     other-modules:    EpubParser,
                       UI,
-                      Persistence
+                      Persistence,
+                      State
 
     build-depends:    base ^>=4.21.0.0,
                       base64-bytestring,