svitak/app/Types.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

-- | Shared types for the whole reader. The parser ('EpubParser') produces a
-- 'BookStructure' cheaply and renders each 'Chapter' on demand; the UI
-- consumes both through the 'BookInfo' interface.
module Types
  ( -- * Identifiers
    ChapterIndex (..),
    InternalPath (..),

    -- * Book content
    Chapter (..),
    ChapterRef (..),
    TocEntry (..),
    BookStructure (..),

    -- * The book interface the UI talks to
    BookInfo (..),

    -- * UI state
    AppState (..),
    UserAction (..),

    -- * EPUB environment
    EpubEnv (..),
    EpubAction,
    ReadMode(..),
    Html(..),
    PlainText(..),
  )
where

import Codec.Archive.Zip (Archive)
import qualified Codec.Epub.Data.Manifest as DMan
import qualified Codec.Epub.Data.Metadata as DMeta
import Control.Monad.Except (ExceptT)
import Control.Monad.Reader (ReaderT)
import qualified Data.Map.Strict as M
import qualified Data.Text as T
-- | Position of a chapter within the linear reading order (the spine).
newtype ChapterIndex = ChapterIndex Int
  deriving (Show, Eq, Ord, Num)

-- | A fully-resolved path to a file inside the EPUB zip.
newtype InternalPath = InternalPath FilePath
  deriving (Show, Eq, Ord)

-- | A lightweight pointer to a chapter: enough to navigate and label it in the
-- sidebar without having rendered its (potentially large) content yet.
data ChapterRef = ChapterRef
  { refPath :: InternalPath,
    refTitle :: T.Text,
    refIndex :: ChapterIndex
  }
  deriving (Show)

-- | A chapter rendered to self-contained HTML, ready for WebKit.
data Chapter = Chapter
  { chapterPath :: InternalPath,
    chapterTitle :: T.Text,
    chapterHtml :: Html,
    chapterIndex :: ChapterIndex
  }
  deriving (Show)

newtype Html = Html T.Text deriving (Show, Eq)
newtype PlainText = PlainText T.Text deriving (Show, Eq)

-- | A node in the (possibly nested) table of contents. @tocTarget@ is the
-- resolved chapter path; @tocFragment@ is the optional in-page anchor.
data TocEntry = TocEntry
  { tocLabel :: T.Text,
    tocTarget :: InternalPath,
    tocFragment :: T.Text,
    tocChildren :: [TocEntry]
  }
  deriving (Show)

-- | The cheap-to-compute skeleton of a book: reading order + navigation tree.
data BookStructure = BookStructure
  { structRefs :: [ChapterRef],
    structToc :: [TocEntry]
  }

-- | The UI only ever sees a book through this interface, so it stays
-- format-agnostic. The single instance ('EpubEnv') lives in 'EpubParser'.
class BookInfo a where
  bookTitle :: a -> T.Text
  bookAuthors :: a -> [T.Text]
  bookFilePath :: a -> FilePath

  -- | Resolve the spine and TOC. Fast: does not render chapter bodies.
  loadStructure :: a -> IO (Either String BookStructure)

  -- | Render a single chapter's body to self-contained HTML, on demand.
  renderChapter :: a -> ChapterRef -> IO (Either String Chapter)

  -- | Extract a single chapter's plain text (tags stripped), for search.
  chapterText :: a -> ChapterRef -> IO (Either String PlainText)

-- | Mutable application state, held in a 'Control.Concurrent.STM.TVar'.
-- Rendered chapters accumulate in 'stCache' as the reader visits them.
data AppState = AppState
  { stRefs :: [ChapterRef],
    stToc :: [TocEntry],
    stCache :: M.Map ChapterIndex Chapter,
    stIndex :: ChapterIndex,
    stZoom :: Double,
    stTitle :: T.Text,
    stBookPath :: FilePath,
    stGen :: Int,
    stUse :: M.Map ChapterIndex Int,
    stTick :: Int,
    stSearchIndex :: M.Map ChapterIndex PlainText,
    stMode :: ReadMode
  }

-- Enable toggling between paginated (2 pages on the screen) or scrolling (single, flowing page)
data ReadMode = Paginated | Scrolling
  deriving (Eq)

-- | A user request, produced by the keyboard / sidebar and handled centrally.
-- 'GoToChapter' carries an optional anchor to scroll to within the chapter.
data UserAction
  = NextChapter
  | PrevChapter
  | ZoomIn
  | ZoomOut
  | GoToChapter ChapterIndex T.Text
  | NextPage
  | PrevPage
  | ToggleMode
  | SearchFocus

-- | Parsed EPUB, carried through the parser as a reader environment.
data EpubEnv = EpubEnv
  { archive :: Archive,
    opfXml :: String,
    baseDir :: FilePath,
    bookPath :: FilePath,
    eMetadata :: DMeta.Metadata,
    eManifest :: DMan.Manifest,
    eVersion :: T.Text
  }

-- | The parser monad: read-only access to the 'EpubEnv', with string errors.
type EpubAction a = ReaderT EpubEnv (ExceptT String IO) a