initial version; nixos module untested

.gitignore

@@ -0,0 +1 @@
+/gomod2nix-template

birdtown-visit-counter.go

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+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+	"sync"
+)
+
+type visitsStore struct {
+	m map[string]int
+	*sync.RWMutex
+}
+
+func (s *visitsStore) visit(ending string) int {
+	s.Lock()
+	defer s.Unlock()
+	oldVisits, has := s.m[ending]
+	var newVisits int
+	if has {
+		newVisits = oldVisits + 1
+	} else {
+		newVisits = 1
+	}
+	s.m[ending] = newVisits
+	return newVisits
+}
+
+type visitsHandler struct {
+	store *visitsStore
+}
+
+func (h *visitsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// CORS: this is expected to be called from a different domain,
+	// hoops require jumping
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("Access-Control-Max-Age", "86400")
+	w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS")
+	w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization")
+
+	w.Header().Set("content-type", "application/json")
+
+	if r.Method == http.MethodPost {
+		var s string
+		if err := json.NewDecoder(r.Body).Decode(&s); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("cannot parse data"))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write(([]byte)(strconv.Itoa(h.store.visit(s))))
+		return
+	}
+	if r.Method == http.MethodGet {
+		jsonBytes, err := json.Marshal(h.store.m)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("cannot serialize"))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write(jsonBytes)
+		return
+	}
+	if r.Method == http.MethodOptions {
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+	w.Header().Set("Allow", "POST, GET, OPTIONS")
+	w.WriteHeader(http.StatusMethodNotAllowed)
+}
+
+func main() {
+	addr := flag.String("addr", ":11568", "Listen address")
+	initialFile := flag.String("file", "visits.json", "File with initial data in JSON format")
+	flag.Parse()
+
+	initialVisits := make(map[string]int)
+	initialVisitsJson, err := os.ReadFile(*initialFile)
+	if err == nil {
+		json.Unmarshal(initialVisitsJson, &initialVisits)
+	} else {
+		log.Println("initial file", *initialFile, "could not be read, defaulting to empty data")
+	}
+
+	store := visitsStore{m: initialVisits, RWMutex: &sync.RWMutex{}}
+	visitsH := &visitsHandler{store: &store}
+	http.Handle("/visits", visitsH)
+
+	log.Println("Starting web server...")
+	http.ListenAndServe(*addr, nil)
+}

default.nix

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+{ pkgs ? (
+    let
+      inherit (builtins) fetchTree fromJSON readFile;
+      inherit ((fromJSON (readFile ./flake.lock)).nodes) nixpkgs gomod2nix;
+    in
+    import (fetchTree nixpkgs.locked) {
+      overlays = [
+        (import "${fetchTree gomod2nix.locked}/overlay.nix")
+      ];
+    }
+  )
+, buildGoApplication ? pkgs.buildGoApplication
+}:
+
+buildGoApplication {
+  pname = "birdtown-visit-counter";
+  version = "0.1";
+  pwd = ./.;
+  src = ./.;
+  modules = ./gomod2nix.toml;
+}

flake.lock

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+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "gomod2nix": {
+      "inputs": {
+        "flake-utils": [
+          "flake-utils"
+        ],
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1725515722,
+        "narHash": "sha256-+gljgHaflZhQXtr3WjJrGn8NXv7MruVPAORSufuCFnw=",
+        "owner": "nix-community",
+        "repo": "gomod2nix",
+        "rev": "1c6fd4e862bf2f249c9114ad625c64c6c29a8a08",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "gomod2nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1725983898,
+        "narHash": "sha256-4b3A9zPpxAxLnkF9MawJNHDtOOl6ruL0r6Og1TEDGCE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "1355a0cbfeac61d785b7183c0caaec1f97361b43",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "gomod2nix": "gomod2nix",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "birdtown-visit-counter";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs.gomod2nix.url = "github:nix-community/gomod2nix";
+  inputs.gomod2nix.inputs.nixpkgs.follows = "nixpkgs";
+  inputs.gomod2nix.inputs.flake-utils.follows = "flake-utils";
+
+  outputs = inputs @ { self, nixpkgs, flake-utils, gomod2nix }:
+    (flake-utils.lib.eachDefaultSystem
+      (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+          callPackage = pkgs.darwin.apple_sdk_11_0.callPackage or pkgs.callPackage;
+        in
+        {
+          packages.default = callPackage ./. {
+            inherit (gomod2nix.legacyPackages.${system}) buildGoApplication;
+          };
+          devShells.default = callPackage ./shell.nix {
+            inherit (gomod2nix.legacyPackages.${system}) mkGoEnv gomod2nix;
+          };
+          nixosModules.default = import ./module.nix inputs;
+        })
+    );
+}

go.mod

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+module git.akho.name/akho/birdtown-visit-counter
+
+go 1.22

gomod2nix.toml

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+schema = 3
+
+[mod]

module.nix

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+inputs:
+{ config, lib, pkgs, ... }:
+let
+  inherit (pkgs.stdenv.hostPlatform) system;
+  cfg = config.services.birdtown-visit-counter;
+  inherit (lib) types mkOption mkIf;
+  package = inputs.self.packages."${system}".birdtown-visit-counter;
+in {
+  options.services.birdtown-visit-counter = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+      };
+      listenPort = mkOption {
+        type = types.int;
+        default = 11567;
+      };
+    };
+  config = {
+    users.users.birdtown-visit-counter = {
+        group = "birdtown-visit-counter";
+        home = "/var/lib/birdtown-visit-counter";
+        isSystemUser = true;
+        createHome = true;
+      };
+      users.groups.birdtown-visit-counter = { };
+
+      systemd.services.birdtown-visit-counter = {
+        after = [ "network.target" ];
+        wantedBy = [ "multi-user.target" ];
+        serviceConfig = {
+          ExecStart = "${package}/bin/birdtown-visit-counter -addr :${cfg.listenPort} -file visits.json";
+          User = "birdtown-visit-counter";
+          Group = "birdtown-visit-counter";
+          WorkingDirectory = "/var/lib/birdtown-visit-counter";
+        };
+      };
+
+      systemd.timers.birdtown-visits-saver = {
+        wantedBy = [ "timers.target" ];
+        timerConfig = {
+          OnBootSec = "10m";
+          OnUnitActiveSec = "10m";
+          Unit = "birdtown-visits-saver.service";
+        };
+      };
+
+      systemd.services.birdtown-visits-saver = {
+        script = ''
+          set -eu
+          if ${pkgs.curl}/bin/curl http://localhost:${cfg.listenPort}/visits > visits-new.json; then
+             cp visits-new.json "$(date +"%Y-%m-%d-%H-%M").json"
+             mv visits-new.json visits.json
+           fi
+        '';
+        serviceConfig = {
+          Type = "oneshot";
+          User = "birdtown-visit-counter";
+          Group = "birdtown-visit-counter";
+          WorkingDirectory = "/var/lib/birdtown-visit-counter";
+        };
+      };
+  };
+}

shell.nix

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+{ pkgs ? (
+    let
+      inherit (builtins) fetchTree fromJSON readFile;
+      inherit ((fromJSON (readFile ./flake.lock)).nodes) nixpkgs gomod2nix;
+    in
+    import (fetchTree nixpkgs.locked) {
+      overlays = [
+        (import "${fetchTree gomod2nix.locked}/overlay.nix")
+      ];
+    }
+  )
+, mkGoEnv ? pkgs.mkGoEnv
+, gomod2nix ? pkgs.gomod2nix
+}:
+
+let
+  goEnv = mkGoEnv { pwd = ./.; };
+in
+pkgs.mkShell {
+  packages = [
+    goEnv
+    pkgs.go-tools
+    pkgs.gopls
+    gomod2nix
+  ];
+}