let

pkgs=(import <nixpkgs>{});

# wallpaperOpts should have the following format:

#{

# settings =

# {

# setterProgram = {

# executable = "${pkgs.feh}/bin/feh";

# arguments = [ "--bg-max" "--no-xinerama" ];

# };

# # This is the output hash for fixed output derivation

# hash = "0000000000000000000000000000000000000000000000000000000000000000";

# };

# wallpapers = {

# urls = [

# "url 1"

# "url 2"

# # Mentioning hash prevents redownload of

# # all wallpapers everytime a

# # single is added or deleted

# { url = "url3"; hash = "hash3";}

# ];

# localFiles = [ ... ] ;

# localDirs = [ ... ] ;

# };

#}

addNullHashtoUrls =

urlWithOptionalHash:

if

( builtins.typeOf urlWithOptionalHash == "string" )

then

{

url = urlWithOptionalHash;

hash = "";

}

else

urlWithOptionalHash

;

imageFileFilter = imageFileName:

(

pkgs.lib.hasSuffix "png" imageFileName

|| pkgs.lib.hasSuffix "jpg" imageFileName

)

;

wallpaperOpts = (import ./WallpaperOpts.nix { inherit pkgs; } );

backgroundSetterProgram = wallpaperOpts.settings.setterProgram.executable;

backgroundSetterArguments = wallpaperOpts.settings.setterProgram.arguments;

backgroundSetterArgumentsSingleString = pkgs.lib.concatStringsSep " " backgroundSetterArguments;

allWallpapers = wallpaperOpts.wallpapers;

allUrlWallpapers =

builtins.map

addNullHashtoUrls

allWallpapers.urls

;

singleDirectoryWallpapers =

dirName:

(

builtins.filter

imageFileFilter

(

pkgs.lib.mapAttrsToList

( name: value: name )

( builtins.readDir dirName )

)

)

;

allDirectoryWallpapers =

pkgs.lib.flatten

(

map

singleDirectoryWallpapers

allWallpapers.localDirs

)

;

nix_code_prologue = ''

echo "pkgs: " > $1

echo "[" >> $1

'';

nix_code_generator_script =

pkgs.lib.concatStringsSep

"\n"

(

map

(

{

url,

hash

}:

''

if [ -z "${hash}" ]

then

${pkgs.wget}/bin/wget --no-check-certificate ${url} -O blah 2>/dev/null

hash=$(${pkgs.nix}/bin/nix-hash --type sha256 --flat --base32 blah)

echo ${url}

echo $hash

else

#echo "hash ${hash} already known for ${url}"

hash="${hash}"

fi

if [ ! -z $hash ]

then

cat << XJK >> $1

(

pkgs.fetchurl{

url = "${url}";

sha256="$hash";

}

)

XJK

else

echo "========hash FAILED for ${url}============="

fi

''

)

allUrlWallpapers

)

;

nix_code_epilogue = ''

echo "]" >> $1

echo "" >> $1

'';

bashCreatorOfWallpaperFetcherNixScript = (

pkgs.writeShellScript

"BashCreatorOfWallpaperFetcherNixScript"

(nix_code_prologue nix_code_generator_script nix_code_epilogue)

);

wallpaperFetcherNixScript = (

pkgs.stdenv.mkDerivation

(

{

name = "wallpaper-fetcher.nix";

buildCommand =

''

${bashCreatorOfWallpaperFetcherNixScript} $out

''

;

}

//

(

if (

builtins.all ( url: (builtins.typeOf url) != "string" ) wallpaperOpts.wallpapers.urls

)

then

{}

else

{

outputHashAlgo = "sha256";

outputHashMode = "recursive";

outputHash = wallpaperOpts.settings.hash;

}

)

)

);

downloadedOnlineWallpapers = (import wallpaperFetcherNixScript pkgs);

allWallpapersLocalized = downloadedOnlineWallpapers allWallpapers.localFiles allDirectoryWallpapers;

numWallpapers =

builtins.toString

(

builtins.length

allWallpapersLocalized

)

;

wallpaperBashArray =

"wallpaperArray=(\n"

(

pkgs.lib.concatStringsSep

"\n"

allWallpapersLocalized

)

"\n)"

;

in

pkgs.writeShellScript

"RandomWallpaperSetter"

(

wallpaperBashArray "\n"

"chosenWallpaper=$" "{wallpaperArray[$(( $RANDOM % ${numWallpapers} ))]}\n"

"echo $chosenWallpaper\n"

"${backgroundSetterProgram} ${backgroundSetterArgumentsSingleString} $chosenWallpaper\n"

)