meta: have a actually nix flake shell

Signed-off-by: Vincenzo Palazzo <[email protected]>

flake.nix

@@ -0,0 +1,47 @@
+{
+  description = "BTCPay nix flake";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        dotnet-combined = (with pkgs.dotnetCorePackages;
+          combinePackages [ sdk_8_0 sdk_7_0 ]).overrideAttrs
+          (finalAttrs: previousAttrs: {
+            # This is needed to install workload in $HOME
+            # https://discourse.nixos.org/t/dotnet-maui-workload/20370/2
+
+            postBuild = (previousAttrs.postBuild or "") + ''
+               for i in $out/sdk/*
+               do
+                 i=$(basename $i)
+                 length=$(printf "%s" "$i" | wc -c)
+                 substring=$(printf "%s" "$i" | cut -c 1-$(expr $length - 2))
+                 i="$substring""00"
+                 mkdir -p $out/metadata/workloads/''${i/-*}
+                 touch $out/metadata/workloads/''${i/-*}/userlocal
+              done
+            '';
+          });
+      in rec {
+        packages = { dotnet = pkgs.dotnet-sdk; };
+
+        default = packages.dotnet;
+
+        DOTNET_ROOT = "${dotnet-combined}";
+
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [ dotnet-combined docker docker-compose ];
+
+          mkShellHook = ''
+            export DOTNET_ROOT=$HOME/.dotnet
+            export PATH=$PATH:$DOTNET_ROOT:$DOTNET_ROOT/tools
+          '';
+        };
+      });
+}