# atproto-likes — the "most-liked accounts" web UI, run as a docker-compose stack
#
# ⚠️  COPY. Canonical source:
#     /srv/project-orchestrator/projects/notplants-atproto/nix/atproto-likes.nix
#     Pure evaluation cannot import a path outside the flake tree. Re-copy after editing.
# behind the host's nginx.
#
# Import this from the host configuration:
#   imports = [ /srv/project-orchestrator/projects/notplants-atproto/nix/atproto-likes.nix ];
#
# What it sets up:
#   * the Docker daemon (this host had none before)
#   * a systemd unit that builds and runs docker-compose.yml from the project checkout
#   * an nginx vhost for atproto.commoninternet.net with a Let's Encrypt cert,
#     proxying to the container on 127.0.0.1:8731
#   * ports 80/443 open (they were closed — only 22 was public)
#
# DNS: atproto.commoninternet.net resolves to 143.244.213.108 — the operator's
# gateway (tailnet peer `gateway-server-aug2-9pm`, 100.80.66.110), which fronts this
# host rather than pointing at it directly. So what arrives here is the gateway's
# back-end hop. It must point at
#
#     http://168.119.126.100     (the PUBLIC address — never 100.84.190.30)
#
# because the tailscale address is where the opencode UI lives and is that address
# group's default server; a hop there with a missing or wrong Host header would be
# served opencode. See the listen comments below. The gateway should also pass
# Upgrade/Connection through (the loading page is a websocket) and allow a long
# read timeout (a cold scan runs minutes).
#
# The gateway forwards everything, including /.well-known/acme-challenge/, so ACME
# HTTP-01 here will start succeeding as soon as the gateway has a route for this
# hostname. Until then nginx serves the self-signed placeholder NixOS installs.
{ config, pkgs, lib, ... }:

let
  projectDir = "/srv/project-orchestrator/projects/notplants-atproto";
  domain = "atproto.commoninternet.net";
  hostPort = 8731;                        # must match the ports: mapping in docker-compose.yml
  compose = "${pkgs.docker-compose}/bin/docker-compose";
in
{
  virtualisation.docker = {
    enable = true;
    # Reclaim dangling images from repeated `--build` runs.
    autoPrune = { enable = true; dates = "weekly"; };
  };

  # Build + run the compose stack. Type=oneshot with RemainAfterExit: compose
  # detaches, and the containers' own restart policy keeps them alive.
  systemd.services.atproto-likes = {
    description = "atproto-likes — most-liked-accounts web UI (docker compose)";
    wantedBy = [ "multi-user.target" ];
    after = [ "docker.service" "docker.socket" "network-online.target" ];
    requires = [ "docker.service" ];
    wants = [ "network-online.target" ];
    path = [ pkgs.docker pkgs.docker-compose ];
    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = true;
      WorkingDirectory = projectDir;
      # A cold `--build` pulls python:3.12-slim and installs pip deps.
      TimeoutStartSec = "1800";
      ExecStart = "${compose} up -d --build --remove-orphans";
      ExecStop = "${compose} down";
      Restart = "on-failure";
      RestartSec = "30s";
    };
  };

  services.nginx = {
    enable = true;
    recommendedProxySettings = true;
    virtualHosts.${domain} = {
      # addSSL, NOT forceSSL. DNS for this domain points at the gateway
      # (143.244.213.108), which fronts this host — so the request that actually
      # arrives here is the gateway's back-end hop. If that hop is plain HTTP and
      # we answered with a 301 to https://atproto.commoninternet.net/, it would
      # resolve straight back to the gateway: a redirect loop. Serve both schemes
      # and let the gateway decide where TLS terminates.
      addSSL = true;
      # The gateway forwards everything, so once it has a route for this hostname
      # the HTTP-01 challenge reaches us and this starts succeeding on its own.
      # Until then the acme-atproto… unit sits in `failed` and nginx uses the
      # self-signed placeholder; nothing else on the host is affected.
      enableACME = true;
      # PUBLIC INTERFACE ONLY — deliberately not the tailscale address.
      #
      # nginx groups servers by the connection's local address and prefers the most
      # specific listen. `oc.commoninternet.net` (the opencode UI) binds explicitly
      # to 100.84.190.30:80, so that address has its own group in which oc is the
      # DEFAULT server. Anything arriving there without a matching Host — a proxy
      # that drops the header, or sends `Host: 100.84.190.30` — is served opencode.
      # So the gateway must hop to the PUBLIC address, never the tailscale one:
      # this vhost lives on 0.0.0.0, where the only servers are itself and the
      # reject-everything default below. Keeping the two names on disjoint
      # addresses is what makes "opencode cannot leak publicly" structural rather
      # than a matter of getting a Host header right.
      locations."/" = {
        proxyPass = "http://127.0.0.1:${toString hostPort}";
        # The loading page streams scan progress over a websocket.
        proxyWebsockets = true;
        # A cold scan can run for minutes with the socket open; the default 60s
        # proxy read timeout would cut the loading page off mid-flower.
        extraConfig = ''
          proxy_read_timeout 1800s;
          proxy_send_timeout 1800s;
        '';
      };
    };

    # Strict default server for the PUBLIC addresses. Without an explicit
    # default_server, nginx promotes the first server block in the group — so
    # every future vhost added to 0.0.0.0 silently becomes the thing that answers
    # unmatched/absent/spoofed Host headers from the internet. This closes that
    # door once: only names we deliberately serve get a response here.
    #
    #   port 80  -> 444 (close the connection, no response at all)
    #   port 443 -> ssl_reject_handshake, so an unknown SNI never even gets TLS
    #
    # It listens only on 0.0.0.0, so the tailscale address group is untouched and
    # oc.commoninternet.net keeps behaving exactly as before on the tailnet.
    virtualHosts."public-default-reject" = {
      default = true;
      serverName = null;
      rejectSSL = true;
      listen = [
        { addr = "0.0.0.0"; port = 80;  ssl = false; }
        { addr = "0.0.0.0"; port = 443; ssl = true;  }
      ];
      extraConfig = "return 444;";
    };
  };

  security.acme = {
    acceptTerms = true;
    defaults.email = "mfowler.email@protonmail.com";
  };

  # Public HTTP/HTTPS. Before this, only 22 was open on the public interface.
  networking.firewall.allowedTCPPorts = [ 80 443 ];
}