{- This Source Code Form is subject to the terms of the Mozilla Public License,
   v. 2.0. If a copy of the MPL was not distributed with this file, You can
   obtain one at https://mozilla.org/MPL/2.0/. -}

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE LambdaCase #-}

-- | Outputs information about a font as text.
module Graphics.Fountainhead.Dumper
    ( ParseErrorOrDump
    , dumpCmap
    , dumpTrueType
    , dumpOffsetTable
    ) where

import Data.ByteString (ByteString)
import Data.Int (Int64)
import qualified Data.IntMap as IntMap
import qualified Data.Text.Encoding as Text
import qualified Data.Text.Lazy as Text.Lazy
import qualified Data.Text.Lazy.Builder as Text.Builder
import qualified Data.Text.Lazy.Builder.Int as Text.Builder
import qualified Data.Vector as Vector
import Data.Void
import GHC.Records (HasField(..))
import Graphics.Fountainhead.TrueType
    ( CmapTable(..)
    , FontDirectory(..)
    , OffsetSubtable(..)
    , TableDirectory(..)
    , CmapEncoding(..)
    , CmapSubtable(..)
    , CmapFormat4Table(..)
    )
import qualified Text.Megaparsec as Megaparsec
import Graphics.Fountainhead.Parser
    ( fontDirectoryP
    , parseTable
    , cmapTableP
    )

type ParseErrorOrDump
    = Either (Megaparsec.ParseErrorBundle ByteString Void) Text.Builder.Builder

paddedHexadecimal :: Integral a => a -> Text.Builder.Builder
paddedHexadecimal = ("0x" <>)
    . Text.Builder.fromLazyText
    . Text.Lazy.justifyRight 8 '0'
    . Text.Builder.toLazyText
    . Text.Builder.hexadecimal

justifyNumber :: Integral a => Int64 -> a -> Text.Builder.Builder
justifyNumber count = Text.Builder.fromLazyText
    . Text.Lazy.justifyRight count ' '
    . Text.Builder.toLazyText
    . Text.Builder.decimal

newlineBuilder :: Text.Builder.Builder
newlineBuilder = Text.Builder.singleton '\n'

dumpHead :: String -> Text.Builder.Builder
dumpHead headline = Text.Builder.fromString headline
    <> newlineBuilder
    <> Text.Builder.fromLazyText (Text.Lazy.replicate headlineLength "-")
    <> newlineBuilder
  where
    headlineLength = fromIntegral $ Prelude.length headline

dumpOffsetTable :: FontDirectory -> Text.Builder.Builder
dumpOffsetTable directory
    = dumpHead "Offset Table"
    <> "         sfnt version:           1.0\n         number of tables: "
    <> Text.Builder.decimal (numTables $ offsetSubtable directory)
    <> newlineBuilder
    <> dumpOffsetSummary (tableDirectory directory)
  where
    dumpOffsetSummary = mconcat . fmap dumpOffsetRow . zip [0 :: Int ..]
    dumpOffsetRow (index, table) = justifyNumber 4 index
        <> ". '"
        <> Text.Builder.fromText (Text.decodeASCII $ tag table)
        <> "' - checksum = "
        <> paddedHexadecimal (getField @"checkSum" table)
        <> ", offset = "
        <> paddedHexadecimal (getField @"offset" table)
        <> ", len = "
        <> justifyNumber 9 (getField @"length" table)
        <> newlineBuilder

dumpCmap :: CmapTable -> Text.Builder.Builder
dumpCmap CmapTable{..}
    = dumpHead "'cmap' Table - Character to Glyph Index Mapping Table"
    <> "        'cmap' version: " <> Text.Builder.decimal version <> newlineBuilder
    <> "        number of encodings: " <> Text.Builder.decimal encodingsLength <> newlineBuilder
    <> "        number of subtables: " <> Text.Builder.decimal (Prelude.length subtables) <> newlineBuilder
    <> newlineBuilder
    <> snd (foldr dumpCmapEncoding (pred encodingsLength, "") encodings) <> newlineBuilder
    <> snd (foldr dumpCmapSubTable (pred subTablesLength, "") subtables) <> newlineBuilder
  where
    encodingsLength = Prelude.length encodings
    subTablesLength = IntMap.size subtables
    dumpCmapEncoding CmapEncoding{..} (index, accumulator) =
        let findSubTableIndex = Text.Builder.decimal
                . Prelude.length
                . filter ((< offset) . fromIntegral)
                . IntMap.keys
            summary = "Encoding   " <> Text.Builder.decimal index
                <> ".    PlatformID:  " <> Text.Builder.decimal platformID <> newlineBuilder
                <> "                 EcodingID:   " <> Text.Builder.decimal platformSpecificID <> newlineBuilder
                <> "                 SubTable: " <> findSubTableIndex subtables
                <> ", Offset: " <> paddedHexadecimal offset <> newlineBuilder
         in (pred index, summary <> newlineBuilder <> accumulator)
    dumpCmapSubTable currentSubTable (index, accumulator) =
        let contents = "SubTable   " <> Text.Builder.decimal index
                <> ".    " <> dumpCmapSubTableFormat currentSubTable
         in (pred index, contents <> accumulator)
    dumpCmapSubTableFormat = \case
        (CmapFormat0 _) -> "Format 0"
        (CmapFormat2 _) -> "Format 2"
        (CmapFormat4 CmapFormat4Table{..}) ->
            "Format 4 - Segment mapping to delta values\n\
            \                 Length:     994\n\
            \                 Version:      0\n\
            \                 segCount:       "
            <> Text.Builder.decimal (Vector.length startCode)
            <> newlineBuilder <> "                 searchRange:    "
            <> Text.Builder.decimal searchRange
            <> newlineBuilder <> "                 entrySelector:  "
            <> Text.Builder.decimal entrySelector
            <> newlineBuilder <> "                 rangeShift:     "
            <> Text.Builder.decimal (Vector.length startCode * 2 - fromIntegral searchRange)
        (CmapFormat6 _) -> "Format 6"
        (CmapFormat8 _) -> "Format 8"
        (CmapFormat10 _) -> "Format 10"
        (CmapFormat12 _) -> "Format 12"
        (CmapFormat13 _) -> "Format 13"
        (CmapFormat14 _) -> "Format 14"

dumpTables
    :: Megaparsec.State ByteString Void
    -> FontDirectory
    -> ParseErrorOrDump
dumpTables processedState directory@FontDirectory{..}
    = foldr go (Right $ dumpOffsetTable directory) tableDirectory
  where
    go :: TableDirectory -> ParseErrorOrDump -> ParseErrorOrDump
    go _ (Left accumulator) = Left accumulator
    go tableEntry (Right accumulator)
        = maybe (Right accumulator) (concatDump accumulator)
        $ dumpSubTable tableEntry
    concatDump accumulator builderDump = ((accumulator <> newlineBuilder) <>)
        <$> builderDump
    dumpSubTable tableEntry =
        case getField @"tag" tableEntry of
            "cmap" -> Just $ dumpCmap <$> parseTable tableEntry cmapTableP processedState
            _ -> Nothing

dumpTrueType :: ByteString -> FilePath -> ParseErrorOrDump
dumpTrueType ttfContents fontFile =
    let initialState = Megaparsec.State
            { stateInput = ttfContents
            , stateOffset = 0
            , statePosState = Megaparsec.PosState
                { pstateInput = ttfContents
                , pstateOffset = 0
                , pstateSourcePos = Megaparsec.initialPos fontFile
                , pstateTabWidth = Megaparsec.defaultTabWidth
                , pstateLinePrefix = ""
                }
            , stateParseErrors = []
            }
        (processedState, initialResult) = Megaparsec.runParser' fontDirectoryP initialState 

     in initialResult >>= dumpTables processedState