{ lib, stdenv, runCommand, fetchzip, fetchurl, fetchpatch, fetchFromGitHub
, cmake, pkgconfig, zlib, libpng, makeWrapper
, enableGSL ? true, gsl
, enableGhostScript ? true, ghostscript
, enableMuPDF ? true, mupdf_1_17
, enableDJVU ? true, djvulibre
, enableGOCR ? false, gocr # Disabled by default due to crashes
, enableTesseract ? true, leptonica, tesseract4
}:

with lib;

# k2pdfopt is a pain to package. It requires modified versions of mupdf,
# leptonica, and tesseract.  Instead of shipping patches for these upstream
# packages, k2pdfopt includes just the modified source files for these
# packages.  The individual files from the {mupdf,leptonica,tesseract}_mod/
# directories are intended to replace the corresponding source files in the
# upstream packages, for a particular version of that upstream package.
#
# There are a few ways we could approach packaging these modified versions of
# mupdf, leptonica, and mupdf:
# 1) Override the upstream source with a new derivation that involves copying
# the modified source files from k2pdfopt and replacing the corresponding
# source files in the upstream packages. Since the files are intended for a
# particular version of the upstream package, this would not allow us to easily
# use updates to those packages in nixpkgs.
# 2) Manually produce patches which can be applied against the upstream
# project, and have the same effect as replacing those files.  This is what I
# believe k2pdfopt should do this for us anyway.  The benefit of creating and
# applying patches in this way is that minor updates (esp. security fixes) to
# upstream packages might still allow these patches to apply successfully.
# 3) Automatically produce these patches inside a nix derivation. This is the
# approach taken here, using the "mkPatch" provided below.  This has the
# benefit of easier review and should hopefully be simpler to update in the
# future.

let
  # Create a patch against src based on changes applied in patchCommands
  mkPatch = { name, src, patchCommands }: runCommand "${name}-k2pdfopt.patch" { inherit src; } ''
    source $stdenv/setup
    unpackPhase

    orig=$sourceRoot
    new=$sourceRoot-modded
    cp -r $orig/. $new/

    pushd $new >/dev/null
    ${patchCommands}
    popd >/dev/null

    diff -Naur $orig $new > $out || true
  '';

  pname = "k2pdfopt";
  version = "2.53";
  k2pdfopt_src = fetchzip {
    url = "http://www.willus.com/${pname}/src/${pname}_v${version}_src.zip";
    sha256 = "1fna8bg3pascjfc3hmc6xn0xi2yh7f1qp0d344mw9hqanbnykyy8";
  };
in stdenv.mkDerivation rec {
  inherit pname version;
  src = k2pdfopt_src;

  patches = [
    ./0001-Fix-CMakeLists.patch
  ];

  postPatch = ''
    substituteInPlace willuslib/bmpdjvu.c \
      --replace "<djvu.h>" "<libdjvu/ddjvuapi.h>"
  '';

  nativeBuildInputs = [ cmake pkgconfig makeWrapper ];

  buildInputs =
  let
    # We use specific versions of these sources below to match the versions
    # used in the k2pdfopt source. Note that this does _not_ need to match the
    # version used elsewhere in nixpkgs, since it is only used to create the
    # patch that can then be applied to the version in nixpkgs.
    mupdf_patch = mkPatch {
      name = "mupdf";
      src = fetchurl {
        url = "https://mupdf.com/downloads/archive/mupdf-1.17.0-source.tar.gz";
        sha256 = "13nl9nrcx2awz9l83mlv2psi1lmn3hdnfwxvwgwiwbxlkjl3zqq0";
      };
      patchCommands = ''
        cp ${k2pdfopt_src}/mupdf_mod/{filter-basic,font,stext-device,string}.c ./source/fitz/
        cp ${k2pdfopt_src}/mupdf_mod/pdf-* ./source/pdf/
      '';
    };
    mupdf_modded = mupdf_1_17.overrideAttrs ({ patches ? [], ... }: {
      patches = patches ++ [ mupdf_patch ];
      # This function is missing in font.c, see font-win32.c
      postPatch = ''
        echo "void pdf_install_load_system_font_funcs(fz_context *ctx) {}" >> source/fitz/font.c
      '';
    });

    leptonica_patch = mkPatch {
      name = "leptonica";
      src = fetchurl {
        url = "http://www.leptonica.org/source/leptonica-1.79.0.tar.gz";
        sha256 = "1n004gv1dj3pq1fcnfdclvvx5nang80336aa67nvs3nnqp4ncn84";
      };
      patchCommands = "cp -r ${k2pdfopt_src}/leptonica_mod/. ./src/";
    };
    leptonica_modded = leptonica.overrideAttrs ({ patches ? [], ... }: {
      patches = patches ++ [ leptonica_patch ];
    });

    tesseract_patch = mkPatch {
      name = "tesseract";
      src = fetchFromGitHub {
        owner = "tesseract-ocr";
        repo = "tesseract";
        rev = "4.1.1";
        sha256 = "1ca27zbjpx35nxh9fha410z3jskwyj06i5hqiqdc08s2d7kdivwn";
      };
      patchCommands = ''
        cp ${k2pdfopt_src}/tesseract_mod/{baseapi,tesscapi,tesseract}.* src/api/
        cp ${k2pdfopt_src}/tesseract_mod/{tesscapi,tessedit,tesseract}.* src/ccmain/
        cp ${k2pdfopt_src}/tesseract_mod/dotproduct{avx,fma,sse}.* src/arch/
        cp ${k2pdfopt_src}/tesseract_mod/{intsimdmatrixsse,simddetect}.* src/arch/
        cp ${k2pdfopt_src}/tesseract_mod/{errcode,genericvector,mainblk,params,serialis,tessdatamanager,tess_version,tprintf,unicharset}.* src/ccutil/
        cp ${k2pdfopt_src}/tesseract_mod/{input,lstmrecognizer}.* src/lstm/
        cp ${k2pdfopt_src}/tesseract_mod/openclwrapper.* src/opencl/
      '';
    };
    tesseract_modded = tesseract4.override {
      tesseractBase = tesseract4.tesseractBase.overrideAttrs ({ patches ? [], ... }: {
        patches = patches ++ [ tesseract_patch ];
        # Additional compilation fixes
        postPatch = ''
          echo libtesseract_api_la_SOURCES += tesscapi.cpp >> src/api/Makefile.am
          substituteInPlace src/api/tesseract.h \
            --replace "#include <leptonica.h>" "//#include <leptonica.h>"
        '';
      });
    };
  in
    [ zlib libpng ] ++
    optional enableGSL gsl ++
    optional enableGhostScript ghostscript ++
    optional enableMuPDF mupdf_modded ++
    optional enableDJVU djvulibre ++
    optional enableGOCR gocr ++
    optionals enableTesseract [ leptonica_modded tesseract_modded ];

  dontUseCmakeBuildDir = true;

  cmakeFlags = [ "-DCMAKE_C_FLAGS=-I${src}/include_mod" ];

  NIX_LDFLAGS = "-lpthread";

  installPhase = ''
    install -D -m 755 k2pdfopt $out/bin/k2pdfopt
  '';

  preFixup = optionalString enableTesseract ''
    wrapProgram $out/bin/k2pdfopt --set-default TESSDATA_PREFIX ${tesseract4}/share/tessdata
  '';

  meta = with lib; {
    description = "Optimizes PDF/DJVU files for mobile e-readers (e.g. the Kindle) and smartphones";
    homepage = "http://www.willus.com/k2pdfopt";
    license = licenses.gpl3;
    platforms = platforms.linux;
    maintainers = with maintainers; [ bosu danielfullmer ];
  };
}