args: with args; with stringsWithDeps; with lib;
let inherit (builtins) head tail trace; in
(rec
{
        inherit writeScript; 

        src = attrByPath ["src"] "" args;

        addSbinPath = attrByPath ["addSbinPath"] false args;

        forceShare = if args ? forceShare then args.forceShare else ["man" "doc" "info"];
        forceCopy = ["COPYING" "LICENSE" "DISTRIBUTION" "LEGAL" 
          "README" "AUTHORS" "ChangeLog" "CHANGES" "LICENCE" "COPYRIGHT"] ++ 
          (optional (attrByPath ["forceCopyDoc"] true args) "doc"); 

        hasSuffixHack = a: b: hasSuffix (a+(substring 0 0 b)) ((substring 0 0 a)+b);
        
        archiveType = s: 
                (if hasSuffixHack ".tar" s then "tar"
                else if (hasSuffixHack ".tar.gz" s) || (hasSuffixHack ".tgz" s) then "tgz" 
                else if (hasSuffixHack ".tar.bz2" s) || (hasSuffixHack ".tbz2" s) || 
			(hasSuffixHack ".tbz" s) then "tbz2"
                else if (hasSuffixHack ".tar.Z" s) then "tZ" 
                else if (hasSuffixHack ".tar.lzma" s) then "tar.lzma"
                else if (hasSuffixHack ".tar.xz" s) then "tar.xz"
                else if (hasSuffixHack ".zip" s) || (hasSuffixHack ".ZIP" s) then "zip"
                else if (hasSuffixHack "-cvs-export" s) then "cvs-dir"
                else if (hasSuffixHack ".nar.bz2" s) then "narbz2"

                # Mostly for manually specified directories..
                else if (hasSuffixHack "/" s) then "dir"

                # Last block - for single files!! It should be always after .tar.*
                else if (hasSuffixHack ".bz2" s) then "plain-bz2"
                else if (hasSuffixHack ".gz" s) then "plain-gz"

                else (abort "unknown archive type : ${s}"));

        # changing this ? see [1]
        defAddToSearchPath = fullDepEntry ("
                addToSearchPathWithCustomDelimiter() {
                        local delimiter=\$1
                        local varName=\$2
                        local needDir=\$3
                        local addDir=\${4:-\$needDir}
                        local prefix=\$5
                        if [ -d \$prefix\$needDir ]; then
                                if [ -z \${!varName} ]; then
                                        eval export \${varName}=\${prefix}\$addDir
                                else
                                        eval export \${varName}=\${!varName}\${delimiter}\${prefix}\$addDir
                                fi
                        fi
                }

                addToSearchPath()
                {
                        addToSearchPathWithCustomDelimiter \"\${PATH_DELIMITER}\" \"\$@\"
                }
        ") ["defNest"];

        # changing this ? see [1]
        defNest = noDepEntry ("
                nestingLevel=0

                startNest() {
                        nestingLevel=\$((\$nestingLevel + 1))
                                echo -en \"\\e[\$1p\"
                }

                stopNest() {
                        nestingLevel=\$((\$nestingLevel - 1))
                                echo -en \"\\e[q\"
                }

                header() {
                        startNest \"\$2\"
                                echo \"\$1\"
                }

                # Make sure that even when we exit abnormally, the original nesting
                # level is properly restored.
                closeNest() {
                        while test \$nestingLevel -gt 0; do
                                stopNest
                                        done
                }

                trap \"closeNest\" EXIT
        ");


        # changing this ? see [1]
        minInit = fullDepEntry ("
                set -e
                NIX_GCC=${stdenv.gcc}
                export SHELL=${stdenv.shell}
                PATH_DELIMITER=':'
        " + (if stdenv ? preHook && stdenv.preHook != null && toString stdenv.preHook != "" then 
                "
                param1=${stdenv.param1}
                param2=${stdenv.param2}
                param3=${stdenv.param3}
                param4=${stdenv.param4}
                param5=${stdenv.param5}
                source ${stdenv.preHook}
        " +         
                "
                # Set up the initial path.
                PATH=
                for i in \$NIX_GCC ${toString stdenv.initialPath}; do
                    PATH=\$PATH\${PATH:+\"\${PATH_DELIMITER}\"}\$i/bin
                done

                export TZ=UTC

                prefix=${if args ? prefix then (toString args.prefix) else "\$out"}

                "
        else "")) ["defNest" "defAddToSearchPath"];
                
        # if you change this rewrite using '' instead of "" to get rid of indentation in builder scripts
        addInputs = fullDepEntry ("
                # Recursively find all build inputs.
                findInputs()
                {
                    local pkg=\$1

                    case \$pkgs in
                        *\\ \$pkg\\ *)
                            return 0
                            ;;
                    esac
                    
                    pkgs=\"\$pkgs \$pkg \"

                        echo \$pkg
                    if test -f \$pkg/nix-support/setup-hook; then
                        source \$pkg/nix-support/setup-hook
                    fi
                }

                pkgs=\"\"
                for i in \$NIX_GCC ${toString realBuildInputs}; do
                    findInputs \$i
                done


                # Set the relevant environment variables to point to the build inputs
                # found above.
                addToEnv()
                {
                    local pkg=\$1
                "+
                (if !((args ? ignoreFailedInputs) && (args.ignoreFailedInputs == 1)) then "
                    if [ -e \$1/nix-support/failed ]; then
                        echo \"failed input \$1\" >&2
                        fail
                    fi
                " else "")
                +(if addSbinPath then "
                    if test -d \$1/sbin; then
                        export _PATH=\$_PATH\${_PATH:+\"\${PATH_DELIMITER}\"}\$1/sbin
                    fi
                " else "")
                +"
                    if test -d \$1/bin; then
                        export _PATH=\$_PATH\${_PATH:+\"\${PATH_DELIMITER}\"}\$1/bin
                    fi

                    for i in \"\${envHooks[@]}\"; do
                        \$i \$pkg
                    done
                }

                for i in \$pkgs; do
                    addToEnv \$i
                done


                # Add the output as an rpath.
                if test \"\$NIX_NO_SELF_RPATH\" != \"1\"; then
                    export NIX_LDFLAGS=\"-rpath \$out/lib \$NIX_LDFLAGS\"
                fi

                PATH=\$_PATH\${_PATH:+\"\${PATH_DELIMITER}\"}\$PATH
        ") ["minInit"];
        
        # changing this ? see [1]
        defEnsureDir = fullDepEntry ("
                # Ensure that the given directories exists.
                ensureDir() {
                    local dir
                    for dir in \"\$@\"; do
                        if ! test -x \"\$dir\"; then mkdir -p \"\$dir\"; fi
                    done
                }
        ") ["minInit"];

        # changing this ? see [1]
        toSrcDir = s : fullDepEntry ((if (archiveType s) == "tar" then "
                tar xvf '${s}'
                cd \"\$(tar tf '${s}' | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "tgz" then "
                tar xvzf '${s}'
                cd \"\$(tar tzf '${s}' | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "tbz2" then "
                tar xvjf '${s}'
                cd \"\$(tar tjf '${s}' | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "tZ" then "
                uncompress < '${s}' | tar x
                cd \"\$(uncompress < '${s}' | tar t | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "tar.lzma" then "
                unlzma -d -c <'${s}' | tar xv
                cd \"\$(unlzma -d -c <'${s}' | tar t | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "tar.xz" then "
                xz -d -c <'${s}' | tar xv
                cd \"\$(xz -d -c <'${s}' | tar t | head -1 | sed -e 's@/.*@@' )\"
        " else if (archiveType s) == "zip" then "
                unzip '${s}'
                cd \"$( unzip -lqq '${s}' | tail -1 | 
                        sed -e 's@^\\(\\s\\+[-0-9:]\\+\\)\\{3,3\\}\\s\\+\\([^/]\\+\\)/.*@\\2@' )\"
        " else if (archiveType s) == "cvs-dir" then "
                cp -r '${s}' .
                cd \$(basename ${s})
                chmod u+rwX -R .
        " else if (archiveType s) == "dir" then "
                cp -r '${s}' .
                cd \$(basename ${s})
                chmod u+rwX -R .
        " else if (archiveType s) == "narbz2" then "
                bzip2 <${s} | nix-store --restore \$PWD/\$(basename ${s} .nar.bz2)
                cd \$(basename ${s} .nar.bz2)
        " else if (archiveType s) == "plain-bz2" then "
                mkdir \$PWD/\$(basename ${s} .bz2)
                NAME=\$(basename ${s} .bz2)
                bzip2 -d <${s} > \$PWD/\$(basename ${s} .bz2)/\${NAME#*-}
                cd \$(basename ${s} .bz2)
        " else if (archiveType s) == "plain-gz" then "
                mkdir \$PWD/\$(basename ${s} .gz)
                NAME=\$(basename ${s} .gz)
                gzip -d <${s} > \$PWD/\$(basename ${s} .gz)/\${NAME#*-}
                cd \$(basename ${s} .gz)
        " else (abort "unknown archive type : ${s}"))+
                # goSrcDir is typically something like "cd mysubdir" .. but can be anything else 
                (if args ? goSrcDir then args.goSrcDir else "")
        ) ["minInit"];

        configureCommand = attrByPath ["configureCommand"] "./configure" args;

        # changing this ? see [1]
        doConfigure = fullDepEntry ("
                ${configureCommand} --prefix=\"\$prefix\" ${toString configureFlags}
        ") ["minInit" "addInputs" "doUnpack"];

        # changing this ? see [1]
	doIntltool = fullDepEntry ("
		mkdir -p config
		intltoolize --copy --force
	") ["minInit" "addInputs" "doUnpack"];

        # changing this ? see [1]
        doAutotools = fullDepEntry ("
                mkdir -p config
                libtoolize --copy --force
                aclocal --force
                #Some packages do not need this
                autoheader || true; 
                automake --add-missing --copy
                autoconf
        ")["minInit" "addInputs" "doUnpack"];

        # changing this ? see [1]
        doMake = fullDepEntry ("        
                make ${toString makeFlags}
        ") ["minInit" "addInputs" "doUnpack"];

        doUnpack = toSrcDir (toString src);

        # changing this ? see [1]
        installPythonPackage = fullDepEntry ("
                python setup.py install --prefix=\"\$prefix\" 
                ") ["minInit" "addInputs" "doUnpack"];

        doPythonConfigure = fullDepEntry ('' 
          pythonVersion=$(toPythonPath "$prefix")
          pythonVersion=''${pythonVersion#*/lib/python}
          pythonVersion=''${pythonVersion%%/site-packages}
          ${if args ? extraPythonConfigureCommand then 
            args.extraPythonConfigureCommand 
          else ""}
          python configure.py -b "$prefix/bin" -d "$(toPythonPath "$prefix")" -v "$prefix/share/sip" ${toString configureFlags}
        '') ["minInit" "addInputs" "doUnpack"]; 

        # changing this ? see [1]
        doMakeInstall = fullDepEntry ("
                make ${toString (attrByPath ["makeFlags"] "" args)} "+
                        "${toString (attrByPath ["installFlags"] "" args)} install") ["doMake"];

        # changing this ? see [1]
        doForceShare = fullDepEntry (" 
                ensureDir \"\$prefix/share\"
                for d in ${toString forceShare}; do
                        if [ -d \"\$prefix/\$d\" -a ! -d \"\$prefix/share/\$d\" ]; then
                                mv -v \"\$prefix/\$d\" \"\$prefix/share\"
                                ln -sv share/\$d \"\$prefix\"
                        fi;
                done;
        ") ["minInit" "defEnsureDir"];

        doForceCopy = fullDepEntry (''
                name="$(basename $out)"
                name="''${name#*-}"
                ensureDir "$prefix/share/$name"
                for f in ${toString forceCopy}; do
                        cp -r "$f" "$prefix/share/$name/$f" || true
                done;
        '') ["minInit" "defEnsureDir"];

        doDump = n: noDepEntry "echo Dump number ${n}; set";

	doDumpBuildInputs = noDepEntry (''
	  echo "${toString realBuildInputs}"
	'');

        patchFlags = if args ? patchFlags then args.patchFlags else "-p1";

        patches = attrByPath ["patches"] [] args;

        toPatchCommand = s: "cat ${s} | patch ${toString patchFlags}";

        doPatch = fullDepEntry (concatStringsSep ";"
                (map toPatchCommand patches)
        ) ["minInit" "doUnpack"];

        envAdderInner = s: x: if x==null then s else y: 
                a: envAdderInner (s+"echo export ${x}='\"'\"\$${x}:${y}\";'\"'\n") a;

        envAdder = envAdderInner "";

        envAdderList = l:  if l==[] then "" else 
        "echo export ${head l}='\"'\"\\\$${head l}:${head (tail l)}\"'\"';\n" +
                envAdderList (tail (tail l));

        # changing this ? see [1]
        wrapEnv = cmd: env: "
                mv \"${cmd}\" \"${cmd}-orig\";
                touch \"${cmd}\";
                chmod a+rx \"${cmd}\";
                (${envAdderList env}
                echo '\"'\"${cmd}-orig\"'\"' '\"'\\\$@'\"' \n)  > \"${cmd}\"";

        doWrap = cmd: fullDepEntry (wrapEnv cmd (attrByPath ["wrappedEnv"] [] args)) ["minInit"];

        makeManyWrappers = wildcard : wrapperFlags : fullDepEntry (''
          for i in ${wildcard}; do
            wrapProgram "$i" ${wrapperFlags}
          done
        '') ["minInit" "addInputs" "defEnsureDir"];

        wrapBinContentsPython = (makeManyWrappers 
          ''$out/bin/*'' 
          pythonWrapperArguments
        );

        pythonWrapperArguments = 
          (''--prefix PYTHONPATH : $(toPythonPath $out)'' +
          ''''${PYTHONPATH:+ --prefix PYTHONPATH : $PYTHONPATH}'');

        preservePathWrapperArguments = ''''${PATH:+ --prefix PATH : $PATH }'';

        doPropagate = fullDepEntry ("
                ensureDir \$out/nix-support
                echo '${toString (attrByPath ["propagatedBuildInputs"] [] args)}' >\$out/nix-support/propagated-build-inputs
        ") ["minInit" "defEnsureDir"];

        /*debug = x:(trace x x);
        debugX = x:(trace (toXML x) x);*/

        makeNest = x: if x == defNest.text then x else "startNest\n" + x + "\nstopNest\n";
        textClosure = a: steps: textClosureMap makeNest a (["defNest"] ++ steps);

        inherit noDepEntry fullDepEntry packEntry;

        defList = attrByPath ["defList"] [] args;
        getVal = getValue args defList;
        check = checkFlag args;
        reqsList = attrByPath ["reqsList"] [] args;
        buildInputsNames = filter (x: null != getVal x)
                (uniqList {inputList = 
                  (concatLists (map 
                    (x: if x==[] then [] else builtins.tail x) 
                  reqsList));});
        configFlags = attrByPath ["configFlags"] [] args;
        buildFlags = attrByPath ["buildFlags"] [] args;
        nameSuffixes = attrByPath ["nameSuffixes"] [] args;
        autoBuildInputs = assert (checkReqs args defList reqsList);
                filter (x: x!=null) (map getVal buildInputsNames);
        autoConfigureFlags = condConcat "" configFlags check;
        autoMakeFlags = condConcat "" buildFlags check;
        useConfig = attrByPath ["useConfig"] false args;
        realBuildInputs = 
                lib.closePropagation ((if useConfig then 
                        autoBuildInputs else 
                        attrByPath ["buildInputs"] [] args)++
                        (attrByPath ["propagatedBuildInputs"] [] args));
        configureFlags = if useConfig then autoConfigureFlags else 
            attrByPath ["configureFlags"] "" args;
        makeFlags = if useConfig then autoMakeFlags else attrByPath ["makeFlags"] "" args;

        inherit lib;

        surroundWithCommands = x : before : after : {deps=x.deps; text = before + "\n" +
                x.text + "\n" + after ;};

	createDirs = fullDepEntry (concatStringsSep ";"
		(map (x: "ensureDir ${x}") (attrByPath ["neededDirs"] [] args))
	) ["minInit" "defEnsureDir"];

	copyExtraDoc = fullDepEntry (''
          name="$(basename $out)"
          name="''${name#*-}"
          ensureDir "$out/share/doc/$name"
	'' + (concatStringsSep ";"
               (map 
	         (x: ''cp "${x}" "$out/share/doc/$name" || true;'') 
		 (attrByPath ["extraDoc"] [] args)))) ["minInit" "defEnsureDir" "doUnpack"];

        realPhaseNames = 
	  (optional ([] != attrByPath ["neededDirs"] [] args) "createDirs")
	  ++
	  args.phaseNames 
	  ++ 
          ["doForceShare" "doPropagate" "doForceCopy"]
	  ++
	  (optional ([] != attrByPath ["extraDoc"] [] args) "copyExtraDoc")
          ++
          (optional (attrByPath ["doCheck"] false args) "doMakeCheck")
          ++
          (optional (attrByPath ["alwaysFail"] false args) "doFail")
          ;

        doFail = noDepEntry "
          echo 'Failing to keep builddir (and to invalidate result).'
          a() { return 127; } ; a ;
        ";

        doMakeCheck = fullDepEntry (''
          make check
        '') ["minInit"];

        extraDerivationAttrs = lib.attrByPath ["extraDerivationAttrs"] {} args;

        # for overrides..
	builderDefsArgs = args;

        innerBuilderDefsPackage = bd: args: (
        let localDefs = bd.passthru.function args; in

        stdenv.mkDerivation ((rec {
          inherit (localDefs) name;
          buildCommand = textClosure localDefs localDefs.realPhaseNames;
          meta = localDefs.meta;
	  passthru = localDefs.passthru // {inherit (localDefs) src; };
        }) // (if localDefs ? propagatedBuildInputs then {
          inherit (localDefs) propagatedBuildInputs;
        } else {}) // extraDerivationAttrs)
        );

	builderDefsPackage = bd: func:
	  if (builtins.isFunction func) then 
	    (foldArgs 
	      (x: y: ((func (bd // x // y)) // y))
              (innerBuilderDefsPackage bd)
	      {})
	  else
	    (builderDefsPackage bd (import (toString func)))
	    ;

   generateFontsFromSFD = fullDepEntry (''
           for i in *.sfd; do
                fontforge -c \
                        'Open($1);
                        ${optionalString (args ? extraFontForgeCommands) args.extraFontForgeCommands
                        }Reencode("unicode");
                         ${optionalString (attrByPath ["createTTF"] true args) ''Generate($1:r + ".ttf");''}
                         ${optionalString (attrByPath ["createOTF"] true args) ''Generate($1:r + ".otf");''}
                         Reencode("TeX-Base-Encoding");
                         ${optionalString (attrByPath ["createAFM"] true args) ''Generate($1:r + ".afm");''}
                         ${optionalString (attrByPath ["createPFM"] true args) ''Generate($1:r + ".pfm");''}
                         ${optionalString (attrByPath ["createPFB"] true args) ''Generate($1:r + ".pfb");''}
                         ${optionalString (attrByPath ["createMAP"] true args) ''Generate($1:r + ".map");''}
                         ${optionalString (attrByPath ["createENC"] true args) ''Generate($1:r + ".enc");''}
                        ' $i; 
        done
   '') ["minInit" "addInputs" "doUnpack"];

   installFonts = fullDepEntry (''
           ensureDir $out/share/fonts/truetype/public/${args.name}
           ensureDir $out/share/fonts/opentype/public/${args.name}
           ensureDir $out/share/fonts/type1/public/${args.name}
           ensureDir $out/share/texmf/fonts/enc/${args.name}
           ensureDir $out/share/texmf/fonts/map/${args.name}

        cp *.ttf $out/share/fonts/truetype/public/${args.name} || echo No TrueType fonts
        cp *.otf $out/share/fonts/opentype/public/${args.name} || echo No OpenType fonts
           cp *.{pfm,afm,pfb} $out/share/fonts/type1/public/${args.name} || echo No Type1 Fonts
           cp *.enc $out/share/texmf/fonts/enc/${args.name} || echo No fontenc data
           cp *.map $out/share/texmf/fonts/map/${args.name} || echo No fontmap data
   '') ["minInit" "defEnsureDir"];

   simplyShare = shareName: fullDepEntry (''
     ensureDir $out/share
     cp -r . $out/share/${shareName}
   '') ["doUnpack" "defEnsureDir"];

   doPatchShebangs = dir: fullDepEntry (''
     patchShebangFun() {
     # Rewrite all script interpreter file names (`#! /path') under the
     # specified  directory tree to paths found in $PATH.  E.g.,
     # /bin/sh will be rewritten to /nix/store/<hash>-some-bash/bin/sh.
     # Interpreters that are already in the store are left untouched.
         echo "patching script interpreter paths"
         local f
         for f in $(find "${dir}" -type f -perm +0100); do
             local oldPath=$(sed -ne '1 s,^#![ ]*\([^ ]*\).*$,\1,p' "$f")
             if test -n "$oldPath" -a "''${oldPath:0:''${#NIX_STORE}}" != "$NIX_STORE"; then
                 local newPath=$(type -P $(basename $oldPath) || true)
                 if test -n "$newPath" -a "$newPath" != "$oldPath"; then
                     echo "$f: interpreter changed from $oldPath to $newPath"
                     sed -i "1 s,$oldPath,$newPath," "$f"
                 fi
             fi
         done
     }
     patchShebangFun;
   '') ["minInit"];

   createPythonInstallationTarget = fullDepEntry (''
     ensureDir $(toPythonPath $out)
     export PYTHONPATH=$PYTHONPATH''${PYTHONPATH:+:}$(toPythonPath $out)
   '') ["minInit" "addInputs" "defEnsureDir"];

   fetchUrlFromSrcInfo = srcInfo: fetchurl {
     url = srcInfo.url;
     sha256 = srcInfo.hash;
   };

   fetchGitFromSrcInfo = srcInfo: fetchgit {
     url = srcInfo.url;
     rev = srcInfo.rev;
     sha256 = srcInfo.hash;
   };
}) // args

# [1]: rewrite using '' instead of " so that indentation gets stripped. It's
# only about some spaces but in the end they will sum up