diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..a57a1e6
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1681389457,
+        "narHash": "sha256-Z6TRJ2aI1eRd+kICdrkNyL2aH7XKw8ogzLdtGz1Q9qI=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c58e6fbf258df1572b535ac1868ec42faf7675dd",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
index e69de29..78bf446 100644
--- a/flake.nix
+++ b/flake.nix
@@ -0,0 +1,14 @@
+{
+  description = "Kefla POC";
+
+  outputs = { self, nixpkgs }:
+  let
+    kefla = import ./kefla nixpkgs;
+  in {
+    packages = kefla {
+      package-all = ./package-all.nix;
+      package-darwin = ./package-darwin.nix;
+      package-linux = ./package-linux.nix;
+    };
+  };
+}
diff --git a/kefla/default.nix b/kefla/default.nix
new file mode 100644
index 0000000..895331a
--- /dev/null
+++ b/kefla/default.nix
@@ -0,0 +1,2 @@
+nixpkgs: packages:
+(import ./internal.nix nixpkgs).kefla packages
diff --git a/kefla/fixtures/test-drv-darwin.nix b/kefla/fixtures/test-drv-darwin.nix
new file mode 100644
index 0000000..a056d9f
--- /dev/null
+++ b/kefla/fixtures/test-drv-darwin.nix
@@ -0,0 +1,29 @@
+{ lib
+, stdenv
+, fetchurl
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "hello";
+  version = "2.12.1";
+
+  src = fetchurl {
+    url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
+    sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
+  };
+
+  doCheck = true;
+
+  meta = with lib; {
+    description = "A program that produces a familiar, friendly greeting";
+    longDescription = ''
+      GNU Hello is a program that prints "Hello, world!" when you run it.
+      It is fully customizable.
+    '';
+    homepage = "https://www.gnu.org/software/hello/manual/";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${finalAttrs.version}";
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.eelco ];
+    platforms = platforms.darwin;
+  };
+})
diff --git a/kefla/fixtures/test-drv.nix b/kefla/fixtures/test-drv.nix
new file mode 100644
index 0000000..b8344f1
--- /dev/null
+++ b/kefla/fixtures/test-drv.nix
@@ -0,0 +1,29 @@
+{ lib
+, stdenv
+, fetchurl
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "hello";
+  version = "2.12.1";
+
+  src = fetchurl {
+    url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
+    sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
+  };
+
+  doCheck = true;
+
+  meta = with lib; {
+    description = "A program that produces a familiar, friendly greeting";
+    longDescription = ''
+      GNU Hello is a program that prints "Hello, world!" when you run it.
+      It is fully customizable.
+    '';
+    homepage = "https://www.gnu.org/software/hello/manual/";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${finalAttrs.version}";
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.eelco ];
+    platforms = platforms.all;
+  };
+})
diff --git a/kefla/internal.nix b/kefla/internal.nix
new file mode 100644
index 0000000..75f162c
--- /dev/null
+++ b/kefla/internal.nix
@@ -0,0 +1,71 @@
+nixpkgs:
+let
+  dummyPkgs = import nixpkgs { system = "x86_64-linux"; };
+  lib = dummyPkgs.lib;
+in rec {
+  # Collects all the supported for drv leveraging the meta.platforms
+  # Nixpkgs attribute.
+  #
+  # We callPackage the derivation with a dummy Nixpkgs x86_64
+  # instance, regardless of the underlying arch. It doesn't matter
+  # much, we won't build anything here, we just need callPackage to
+  # evaluate the meta attributes.
+  collectPlatformsForDrv = drv: (dummyPkgs.callPackage drv {}).meta.platforms;
+
+  # Generates the flake outputs for PATH for each PLATFORMS platform.
+  # IE. from
+  # {
+  #  path = /tmp/dummy/path;
+  #  pathName = "hello";
+  #  platforms = [ "x86_64-linux""aarch64-linux"];
+  # };
+  #
+  #  We get:
+  #
+  # {
+  #   aarch64-linux = { hello = /tmp/dummy/path; };
+  #   x86_64-linux = { hello = /tmp/dummy/path; };
+  # }
+  genFlakeOutputForPlatforms = { path, name, platforms }:
+    lib.genAttrs platforms (platform: { ${name} = path; });
+
+  # Goes through a flake-like packages output attrs to inject the
+  # relevant callPackage function call. Obviously, this callPackage
+  # function is platform-dependant, we'll instantiate a different one
+  # for each platform subtree.
+  injectCallPackage = packages:
+    let
+      injectPlatformCallPackage = { attrs, platform }:
+      let
+        pkgs = import nixpkgs { system = platform; };
+        callPackage = pkgs.lib.callPackageWith pkgs;
+      in builtins.mapAttrs (_name: value: callPackage value {}) attrs;
+    in builtins.mapAttrs (name: value:
+         injectPlatformCallPackage { attrs = value; platform = name; }) packages;
+
+  #
+
+  kefla = packagesOutput:
+  let
+    packagesWithoutCallPackage = lib.foldlAttrs
+      (acc: name: path:
+        let
+          platforms = collectPlatformsForDrv path;
+          packageOutput =  genFlakeOutputForPlatforms { inherit path platforms name; };
+        in lib.recursiveUpdate acc packageOutput)
+      { }
+      packagesOutput;
+    in injectCallPackage packagesWithoutCallPackage;
+}
+
+#   lib.foldlAttrs
+#   (acc: name: value:
+#   let
+#       platforms = (dummyPkgs.callPackage value {}).meta.platforms;
+#       # TODO: découper ça avec des tests intermediaires.
+#       entries = lib.genAttrs platforms (platform: )
+#   in builtins.trace platforms (lib.recursiveUpdate acc { hello = platforms; }))
+#   {}
+#   packages
+
+#   }
diff --git a/kefla/test b/kefla/test
new file mode 100755
index 0000000..db6922a
--- /dev/null
+++ b/kefla/test
@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+nix-instantiate --eval --strict test.nix
diff --git a/kefla/test.nix b/kefla/test.nix
new file mode 100644
index 0000000..828c4aa
--- /dev/null
+++ b/kefla/test.nix
@@ -0,0 +1,27 @@
+let
+  nixpkgs = <nixpkgs>;
+  pkgs = import nixpkgs { };
+  internal = import ./internal.nix nixpkgs;
+  fixtures = {
+    testDrv = import ./fixtures/test-drv.nix;
+    testDrvDarwin = import ./fixtures/test-drv-darwin.nix;
+  };
+in pkgs.lib.runTests {
+  # CollectPlatforms
+  ##################
+  testCollectPlatformsAllDrv = {
+    expr = internal.collectPlatformsForDrv fixtures.testDrv ;
+    expected = [ "i686-cygwin" "x86_64-cygwin" "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" "i686-freebsd13" "x86_64-freebsd13" "aarch64-genode" "i686-genode" "x86_64-genode" "x86_64-solaris" "javascript-ghcjs" "aarch64-linux" "armv5tel-linux" "armv6l-linux" "armv7a-linux" "armv7l-linux" "i686-linux" "m68k-linux" "microblaze-linux" "microblazeel-linux" "mipsel-linux" "mips64el-linux" "powerpc64-linux" "powerpc64le-linux" "riscv32-linux" "riscv64-linux" "s390-linux" "s390x-linux" "x86_64-linux" "mmix-mmixware" "aarch64-netbsd" "armv6l-netbsd" "armv7a-netbsd" "armv7l-netbsd" "i686-netbsd" "m68k-netbsd" "mipsel-netbsd" "powerpc-netbsd" "riscv32-netbsd" "riscv64-netbsd" "x86_64-netbsd" "aarch64_be-none" "aarch64-none" "arm-none" "armv6l-none" "avr-none" "i686-none" "microblaze-none" "microblazeel-none" "msp430-none" "or1k-none" "m68k-none" "powerpc-none" "powerpcle-none" "riscv32-none" "riscv64-none" "rx-none" "s390-none" "s390x-none" "vc4-none" "x86_64-none" "i686-openbsd" "x86_64-openbsd" "x86_64-redox" "wasm64-wasi" "wasm32-wasi" "x86_64-windows" "i686-windows" ];
+  };
+  testCollectPlatformsDarwinDrv = {
+    expr = internal.collectPlatformsForDrv fixtures.testDrvDarwin ;
+    expected = [ "x86_64-darwin" "i686-darwin" "aarch64-darwin" "armv7a-darwin" ];
+  };
+
+  # genFlakeOutputForPlatforms
+  ############################
+  testGenFlakeOutputForPlatforms = {
+    expr = internal.genFlakeOutputForPlatforms { path = /tmp/dummy/path; name = "hello"; platforms = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux"]; };
+    expected = { aarch64-linux = { hello = /tmp/dummy/path; }; x86_64-darwin = { hello = /tmp/dummy/path; }; x86_64-linux = { hello = /tmp/dummy/path; };};
+  };
+}
diff --git a/package-all.nix b/package-all.nix
new file mode 100644
index 0000000..b8344f1
--- /dev/null
+++ b/package-all.nix
@@ -0,0 +1,29 @@
+{ lib
+, stdenv
+, fetchurl
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "hello";
+  version = "2.12.1";
+
+  src = fetchurl {
+    url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
+    sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
+  };
+
+  doCheck = true;
+
+  meta = with lib; {
+    description = "A program that produces a familiar, friendly greeting";
+    longDescription = ''
+      GNU Hello is a program that prints "Hello, world!" when you run it.
+      It is fully customizable.
+    '';
+    homepage = "https://www.gnu.org/software/hello/manual/";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${finalAttrs.version}";
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.eelco ];
+    platforms = platforms.all;
+  };
+})
diff --git a/package-darwin.nix b/package-darwin.nix
new file mode 100644
index 0000000..a056d9f
--- /dev/null
+++ b/package-darwin.nix
@@ -0,0 +1,29 @@
+{ lib
+, stdenv
+, fetchurl
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "hello";
+  version = "2.12.1";
+
+  src = fetchurl {
+    url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
+    sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
+  };
+
+  doCheck = true;
+
+  meta = with lib; {
+    description = "A program that produces a familiar, friendly greeting";
+    longDescription = ''
+      GNU Hello is a program that prints "Hello, world!" when you run it.
+      It is fully customizable.
+    '';
+    homepage = "https://www.gnu.org/software/hello/manual/";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${finalAttrs.version}";
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.eelco ];
+    platforms = platforms.darwin;
+  };
+})
diff --git a/package-linux.nix b/package-linux.nix
new file mode 100644
index 0000000..b8344f1
--- /dev/null
+++ b/package-linux.nix
@@ -0,0 +1,29 @@
+{ lib
+, stdenv
+, fetchurl
+}:
+
+stdenv.mkDerivation (finalAttrs: {
+  pname = "hello";
+  version = "2.12.1";
+
+  src = fetchurl {
+    url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
+    sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
+  };
+
+  doCheck = true;
+
+  meta = with lib; {
+    description = "A program that produces a familiar, friendly greeting";
+    longDescription = ''
+      GNU Hello is a program that prints "Hello, world!" when you run it.
+      It is fully customizable.
+    '';
+    homepage = "https://www.gnu.org/software/hello/manual/";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${finalAttrs.version}";
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.eelco ];
+    platforms = platforms.all;
+  };
+})