{
  description = "AVR";

  inputs = {
    nixpkgs.url = "nixpkgs/nixos-21.11";
  };

  outputs = { self, nixpkgs }:
    let 
      version = builtins.string 0 8 self.lastModifiedDate;
      supportedSystems = [ "x86_64-linux" "avr-none" ];
      mcu_cflags = { mcu, chip_select, f_cpu }: ''-O -finline-functions -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Werror -Wstrict-prototypes -DF_CPU=${f_cpu} -std=gnu99 -D__${chip_select}__=1 -mmcu=${mcu}'';

      attiny85 = { mcu = "attiny85"; chip_select = "AVR_ATtiny85"; f_cpu = "8000000"; };
      atmega32u4 = { mcu = "atmega32u4"; chip_select = "AVR_ATmega32u4"; f_cpu = "8000000"; };

      mkLibrary = { pkgs, gcc, cflags, pname, psrc, pbuildInputs ? [] }:
      pkgs.stdenv.mkDerivation rec {
        name = pname;
        src = psrc;

        buildInputs = pbuildInputs;

        include_dirs = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}/include") buildInputs);
        object_files = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

        dontUnpack = true;
        dontConfigure = true;

        buildPhase = ''
          for source in ${src}/*.c; do
              if [ -e $source ]; then
                  ${gcc} ${cflags} ${include_dirs} -c $source
              fi
          done
          cp ${src}/*.h . || true
          '';

        installPhase = ''
          mkdir -p $out/include $out/lib
          cp *.h $out/include || true
          cp *.o $out/lib || true
          '';
      };

      mkProgram = { pkgs, gcc, cflags, pname, psrc, pbuildInputs ? [], avr ? false }:
      let
        AVR = if avr == true then "1" else "";
      in pkgs.stdenv.mkDerivation rec {
        name = pname;
        src = psrc;

        buildInputs = pbuildInputs;

        include_dirs = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}/include") buildInputs);
        object_files = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/lib/*.o") buildInputs);

        dontUnpack = true;
        dontConfigure = true;

        buildPhase = ''
          for source in ${src}/*.c; do
              if [ -e $source ]; then
                  ${gcc} ${cflags} ${include_dirs} -c $source
              fi
          done

          ${gcc} -o ${name}.elf ${cflags} ${object_files} *.o
          if $AVR; then
            $OBJCOPY -O ihex ${name}.elf ${name}.hex
          fi
          '';

        installPhase = ''
          mkdir -p $out/bin
          cp ${name}.elf ${name}.hex $out/bin
          '';
      };

    in rec
    {
      defaultPackage."x86_64-linux" = 
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.symlinkJoin {
          name = "avr-monorepo";
          paths = [
            (packages."x86_64-linux"."prime-tx" { gcc = "${avr.gcc}/bin/avr-gcc"; cflags = mcu_cflags atmega32u4; })
            (packages."x86_64-linux"."radio-rx" { gcc = "${avr.gcc}/bin/avr-gcc"; cflags = mcu_cflags atmega32u4; })
            (packages."x86_64-linux"."lantern" { gcc = "${avr.gcc}/bin/avr-gcc"; cflags = mcu_cflags atmega32u4; avr = true; })
          ];
        };

      packages."x86_64-linux"."dio" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "dio";
          psrc = ./dio;
        };

      packages."x86_64-linux"."animation" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "animation";
          psrc = ./animation;
        };

      packages."x86_64-linux"."sk9822" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "sk9822";
          psrc = ./sk9822;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."shift-register" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "shift-register";
          psrc = ./shift-register;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."spi" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "spi";
          psrc = ./spi;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."rfm" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "rfm";
          psrc = ./rfm69hcw;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
            (packages."x86_64-linux"."spi" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."display" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkLibrary {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "display";
          psrc = ./display;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
            (packages."x86_64-linux"."shift-register" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."prime-tx" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkProgram {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "prime-tx";
          psrc = ./prime-tx;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
            (packages."x86_64-linux"."spi" { inherit gcc cflags; })
            (packages."x86_64-linux"."shift-register" { inherit gcc cflags; })
            (packages."x86_64-linux"."rfm" { inherit gcc cflags; })
            (packages."x86_64-linux"."display" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."radio-rx" =
        { gcc, cflags }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkProgram {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "radio-rx";
          psrc = ./radio-rx;
          pbuildInputs = [
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
            (packages."x86_64-linux"."spi" { inherit gcc cflags; })
            (packages."x86_64-linux"."shift-register" { inherit gcc cflags; })
            (packages."x86_64-linux"."rfm" { inherit gcc cflags; })
            (packages."x86_64-linux"."display" { inherit gcc cflags; })
          ];
        };

      packages."x86_64-linux"."lantern_" = 
      let
        pkgs = import nixpkgs { system = "x86_64-linux"; };
        avr = pkgs.pkgsCross.avr.buildPackages;
      in packages."x86_64-linux"."lantern" { gcc = "${avr.gcc}/bin/avr-gcc"; cflags = mcu_cflags atmega32u4; };
      packages."x86_64-linux"."lantern" =
        { gcc, cflags, avr }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in mkProgram {
          pkgs = pkgs;
          gcc = gcc;
          cflags = cflags;
          pname = "lantern";
          psrc = ./lantern;
          inherit avr;

          pbuildInputs = [
            (packages."x86_64-linux"."animation" { inherit gcc cflags; })
            (packages."x86_64-linux"."dio" { inherit gcc cflags; })
            (packages."x86_64-linux"."display" { inherit gcc cflags; })
            (packages."x86_64-linux"."shift-register" { inherit gcc cflags; })
            (packages."x86_64-linux"."sk9822" { inherit gcc cflags; })
          ];
        };

      devShell."x86_64-linux" =
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = with pkgs.pkgsCross.avr.buildPackages; [
            binutils
            gcc
            gdb
            avrdude
            simavr
            gtkwave
          ];
        in
        pkgs.mkShell {
          name = "avr-shell";
          buildInputs = avr;

          GCC = pkgs.pkgsCross.avr.buildPackages.gcc;
          SIMAVR = pkgs.pkgsCross.avr.buildPackages.simavr;
        };
    };
}