{
  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" ];
      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"; };
      processor = atmega32u4;
    in rec
    {
      defaultPackage."x86_64-linux" = 
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
        in pkgs.symlinkJoin {
          name = "avr-monorepo";
          paths = [
            (packages."x86_64-linux"."flame" processor)
            (packages."x86_64-linux"."prime-tx" processor)
            (packages."x86_64-linux"."radio-rx" processor)
          ];
        };

      packages."x86_64-linux"."base-attiny85" = (packages."x86_64-linux"."base" attiny85);

      packages."x86_64-linux"."base" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "base";
          src = ./.;

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };

          installPhase = ''
            mkdir $out
            cp base/base.h $out/
            '';
        };

      packages."x86_64-linux"."rng" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "rng";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o rng.o -c ${src}/rng/rng.c
            '';

          installPhase = ''
            mkdir $out
            cp rng/rng.h rng.o $out/
            '';
        };

      packages."x86_64-linux"."animation" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "animation";
          src = ./.;

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} -o animation.o -c ${src}/animation/animation.c
            '';

          installPhase = ''
            mkdir $out
            cp animation/animation.h animation.o $out/
            '';
        };

      packages."x86_64-linux"."sk9822" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "sk9822";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o sk9822.o -c ${src}/sk9822/sk9822.c
            '';
          installPhase = ''
            mkdir $out
            cp sk9822/sk9822.h sk9822.o $out/
            '';
        };

      packages."x86_64-linux"."shift-register" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "shift-register";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o shift_register.o -c ${src}/shift_register/shift_register.c
            '';
          installPhase = ''
            mkdir $out
            cp shift_register/shift_register.h shift_register.o $out/
            '';
        };

      packages."x86_64-linux"."spi" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "spi";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o spi.o -c ${src}/spi/spi.c
            '';
          installPhase = ''
            mkdir $out
            cp spi/spi.h spi.o $out/
            '';
        };

      packages."x86_64-linux"."rfm" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "rfm";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."spi" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o rfm.o -c ${src}/rfm69hcw/rfm.c
            '';
          installPhase = ''
            mkdir $out
            cp rfm69hcw/rfm.h rfm.o $out/
            '';
        };

      packages."x86_64-linux"."display" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "display";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."shift-register" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o display.o -c ${src}/display/display.c
            '';
          installPhase = ''
            mkdir $out
            cp display/display.h display.o $out/
            '';
        };

      packages."x86_64-linux"."flame" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          lib = pkgs.lib;
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "flame";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."sk9822" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."rng" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."animation" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o main.o -c ${src}/flame/main.c
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o flame.elf main.o ${OBJECT_FILES}
            $OBJCOPY -O ihex flame.elf flame.hex
            '';
          installPhase = ''
            mkdir $out
            cp flame.elf flame.hex $out
            '';
        };

      packages."x86_64-linux"."prime-tx" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          lib = pkgs.lib;
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "prime-tx";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."spi" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."shift-register" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."rfm" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."display" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);


          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o main.o -c ${src}/prime-tx/main.c
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} -o prime-tx.elf main.o ${OBJECT_FILES}
            $OBJCOPY -O ihex prime-tx.elf prime-tx.hex
            '';

          installPhase = ''
            mkdir $out
            cp prime-tx.elf prime-tx.hex $out
            '';
        };

      packages."x86_64-linux"."radio-rx" =
        { mcu, chip_select, f_cpu }:
        let
          pkgs = import nixpkgs { system = "x86_64-linux"; };
          lib = pkgs.lib;
          avr = pkgs.pkgsCross.avr.buildPackages;
        in pkgs.stdenv.mkDerivation rec {
          name = "prime-tx";
          src = ./.;

          buildInputs = [
            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."spi" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."shift-register" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."rfm" { inherit mcu chip_select f_cpu; })
            (packages."x86_64-linux"."display" { inherit mcu chip_select f_cpu; })
          ];

          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);

          buildPhase = ''
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o main.o -c ${src}/radio-rx/main.c
            ${avr.gcc}/bin/avr-gcc ${CFLAGS} -o radio-rx.elf main.o ${OBJECT_FILES}
            $OBJCOPY -O ihex radio-rx.elf radio-rx.hex
            '';
          installPhase = ''
            mkdir $out
            cp radio-rx.elf radio-rx.hex $out
            '';
        };

      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;
        };
    };
}