chore: Nixify local devshell!

.gitignore

@@ -1,2 +1,8 @@
 /target
 .idea/
+
+.env*
+
+# Nix stuff
+.direnv/
+result*

flake.nix

@@ -0,0 +1,160 @@
+{
+  description = "A Nix-flake-based Rust development environment";
+
+  inputs = {
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
+  };
+
+  outputs = {
+    self,
+    crane,
+    flake-utils,
+    nixpkgs,
+    rust-overlay,
+  }:
+    flake-utils.lib.eachDefaultSystem (system: let
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [(import rust-overlay)];
+      };
+
+      # # Target musl when building on 64-bit linux
+      # buildTarget =
+      #   {"x86_64-linux" = "x86_64-unknown-linux-musl";}.${system}
+      #   or (pkgs.rust.toRustTargetSpec pkgs.stdenv.hostPlatform);
+      # rustToolchain = pkgs.rust-bin.stable.latest.default.override {
+      #   targets = [
+      #     buildTarget
+      #     (pkgs.rust.toRustTargetSpec pkgs.stdenv.hostPlatform)
+      #   ];
+      # };
+      rustToolchain = pkgs.rust-bin.stable.latest.default;
+
+      # Set-up build dependencies and configure rust
+      craneLib = (crane.mkLib pkgs).overrideToolchain rustToolchain;
+
+      inherit (pkgs) lib;
+      # Shamelessly stolen from:
+      # https://github.com/fedimint/fedimint/blob/66519d5e978e22bb10a045f406101891e1bb7eb5/flake.nix#L99
+      filterSrcWithRegexes = regexes: src: let
+        basePath = toString src + "/";
+      in
+        lib.cleanSourceWith {
+          filter = (
+            path: type: let
+              relPath = lib.removePrefix basePath (toString path);
+              includePath =
+                (type == "directory")
+                || lib.any
+                (re: builtins.match re relPath != null)
+                regexes;
+            in
+              # uncomment to debug:
+              # builtins.trace "${relPath}: ${lib.boolToString includePath}"
+              includePath
+          );
+          inherit src;
+        };
+
+      cargo-details = lib.importTOML ./Cargo.toml;
+      pname = cargo-details.package.name;
+      commonArgs = {
+        nativeBuildInputs = with pkgs; [
+          glib
+          openssl
+          pkg-config
+        ];
+        # CARGO_BUILD_TARGET = buildTarget;
+      };
+
+      # Compile and cache only cargo dependencies
+      dep-files-filter = ["Cargo.lock" "Cargo.toml" ".*/Cargo.toml"];
+      cargo-deps = craneLib.buildDepsOnly (commonArgs
+        // {
+          src = filterSrcWithRegexes dep-files-filter ./.;
+          inherit pname;
+        });
+
+      # Compile and cache only workspace code (seperately from 3rc party dependencies)
+      package-file-filter =
+        dep-files-filter
+        ++ [
+          ".*\.rs"
+        ];
+      cargo-package = craneLib.buildPackage (commonArgs
+        // {
+          inherit cargo-deps pname;
+          src = filterSrcWithRegexes package-file-filter ./.;
+        });
+    in {
+      checks = {
+        # inherit # Comment in when you want tests to run on every new shell
+        #   cargo-package
+        #   ;
+      };
+      devShells.default = pkgs.mkShell {
+        packages =
+          (with pkgs; [
+            # rust specific
+            cargo-audit
+            cargo-auditable
+            cargo-cross
+            cargo-deny
+            cargo-outdated
+            rust-analyzer
+
+            # Editor stuffs
+            helix
+            lldb
+            rust-analyzer
+
+            # Nix stuff
+            nix-output-monitor
+          ])
+          ++ commonArgs.nativeBuildInputs
+          ++ [
+            # Packages made in this flake
+            rustToolchain
+            # cargo-package # Comment in when you want tests to run on every new shell
+          ]
+          ++ lib.optionals (pkgs.stdenv.isLinux) (with pkgs; [cargo-watch]); # Currently broken on macOS
+
+        shellHook = ''
+          ${rustToolchain}/bin/cargo --version
+          ${pkgs.helix}/bin/hx --version
+          ${pkgs.helix}/bin/hx --health rust
+        '';
+      };
+      packages = {
+        rust = cargo-package;
+        docker = pkgs.dockerTools.buildImage {
+          name = pname;
+          tag = "v${cargo-details.package.version}";
+          extraCommands = ''mkdir -p data'';
+          config = {
+            Cmd = "--help";
+            Entrypoint = ["${cargo-package}/bin/${pname}"];
+          };
+        };
+      };
+      packages.default = cargo-package;
+
+      # Now `nix fmt` works!
+      formatter = pkgs.nixfmt;
+    });
+}