Add nix package

.gitignore

@@ -1,8 +1,6 @@
 # Files and directories created by pub
 .dart_tool/
 .packages
-# Remove the following pattern if you wish to check in your lock file
-pubspec.lock
 
 # Conventional directory for build outputs
 build/

README.md

@@ -68,6 +68,15 @@ Or, if you have the Flutter SDK installed:
 You might need to follow instructions that `pub` gives you, but after that,
 you can just run `unsure` as a regular command line program from anywhere.
 
+Run it with `nix`:
+```shell
+nix run github:/filiph/unsure
+```
+
+Or when in the directory:
+```shell
+nix run .#unsure
+```
 
 ## Package
 
@@ -146,4 +155,4 @@ probabilities with untrained statisticians (such as myself).
 
 [webapp]: https://filiph.github.io/unsure
 [Build Status - Cirrus]: https://api.cirrus-ci.com/github/filiph/unsure.svg
-[Build status]: https://cirrus-ci.com/github/filiph/unsure/master
+[Build status]: https://cirrus-ci.com/github/filiph/unsure/master

flake.nix

@@ -0,0 +1,50 @@
+{
+  description = "Unsure is used to calculate with numbers you're not sure about";
+
+  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:
+        with nixpkgs; let
+          pkgs = import nixpkgs {
+            inherit system;
+          };
+          unsure = nixpkgs.outputs.legacyPackages.${system}.buildDartApplication rec {
+            pname = "unsure";
+            name = pname;
+            version = "0.4.0";
+
+            src = ./.;
+
+            # Convert lockfile with `yq . pubspec.lock >"pubspec.lock.json"`
+            pubspecLock = lib.importJSON ./pubspec.lock.json;
+          };
+        in {
+          packages = {
+            default = unsure;
+            unsure = unsure;
+          };
+          apps = rec {
+            unsure = flake-utils.lib.mkApp {
+              drv = self.packages.${system}.unsure;
+            };
+            default = unsure;
+          };
+          devShells.default = pkgs.mkShell {
+            buildInputs = with pkgs; [
+              dart
+              yq # To convert the lockfile to json
+            ];
+          };
+        }
+    );
+}