# 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.
#
# Host-specific context that is deliberately NOT in the public project repo:
#   - the domain is fronted by the gateway (143.244.213.108); it forwards everything here
#   - this vhost lists 0.0.0.0 only so it never shares an nginx address group with
#     oc.commoninternet.net (opencode, on the tailscale address, no auth of its own)
#   - /srv/project-orchestrator/projects/notplants-atproto/tools/check-exposure.sh asserts
#     what this host serves publicly; run it after any nginx change
# 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
#   * 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 opened in the firewall
#
# DNS / TLS: point the domain's A record at this host (or at a reverse proxy that
# forwards to it). ACME HTTP-01 needs the challenge to reach this nginx, so if a
# proxy fronts the domain it must forward /.well-known/acme-challenge/ through.
# Until a certificate is issued, NixOS installs a self-signed placeholder so nginx
# still starts.
#
# A proxy in front should preserve the Host header (nginx routes by server_name),
# pass Upgrade/Connection through (the loading page is a websocket) and allow a
# long read timeout (a cold scan can run for minutes).
{ 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";
      # The container runs unprivileged as uid 10001 (see Dockerfile), but the
      # page cache is a host bind mount, so its ownership is the host's business.
      # Without this the app 500s on any actor whose cache files were written by
      # an earlier root-running container.
      ExecStartPre = [
        "${pkgs.coreutils}/bin/mkdir -p ${projectDir}/cache"
        "${pkgs.coreutils}/bin/chown -R 10001:10001 ${projectDir}/cache"
      ];
      ExecStart = "${compose} up -d --build --remove-orphans";
      ExecStop = "${compose} down";
      Restart = "on-failure";
      RestartSec = "30s";
    };
  };

  services.nginx = {
    enable = true;
    recommendedProxySettings = true;
    virtualHosts.${domain} = {
      # addSSL, NOT forceSSL. If a reverse proxy fronts this domain and its
      # back-end hop is plain HTTP, a forced 301 to https://<domain>/ would
      # resolve straight back to that proxy — a redirect loop. Serving both
      # schemes lets whatever is in front decide where TLS terminates.
      addSSL = true;
      enableACME = true;
      # Listens on 0.0.0.0 only, and the reject-everything default server below
      # owns those addresses. nginx groups server blocks by the connection's local
      # address, so keeping this vhost on the public address alone means it never
      # shares an address group with anything else the host may serve on another
      # interface — no other service can be reached by sending this one an
      # unexpected Host header.
      locations."/" = {
        proxyPass = "http://127.0.0.1:${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 any
    # vhost added later silently becomes what answers unmatched, absent or spoofed
    # Host headers from the internet. This closes that door once: only names
    # deliberately served get a response.
    #
    #   port 80  -> 444 (close the connection, no response at all)
    #   port 443 -> ssl_reject_handshake, so an unknown SNI never even gets TLS
    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";   # ACME contact
  };

  # Public HTTP/HTTPS.
  networking.firewall.allowedTCPPorts = [ 80 443 ];
}