# This module is necessary for hosts that are serving through Cloudflare.

# Cloudflare is a CDN service that is used to serve the domain names and
# caching for my websites and services. Since Cloudflare acts as our proxy, we
# must allow access over the Internet from Cloudflare's IP ranges.

# We also want to validate our HTTPS certificates from Caddy. We'll use Caddy's
# DNS validation plugin to connect to Cloudflare and automatically create
# validation DNS records for our generated certificates.

{ config, pkgs, lib, ... }:

let

  cloudflareIpRanges = [

    # Cloudflare IPv4: https://www.cloudflare.com/ips-v4
    "173.245.48.0/20"
    "103.21.244.0/22"
    "103.22.200.0/22"
    "103.31.4.0/22"
    "141.101.64.0/18"
    "108.162.192.0/18"
    "190.93.240.0/20"
    "188.114.96.0/20"
    "197.234.240.0/22"
    "198.41.128.0/17"
    "162.158.0.0/15"
    "104.16.0.0/13"
    "104.24.0.0/14"
    "172.64.0.0/13"
    "131.0.72.0/22"

    # Cloudflare IPv6: https://www.cloudflare.com/ips-v6
    "2400:cb00::/32"
    "2606:4700::/32"
    "2803:f800::/32"
    "2405:b500::/32"
    "2405:8100::/32"
    "2a06:98c0::/29"
    "2c0f:f248::/32"

  ];

in {

  options.cloudflare.enable = lib.mkEnableOption "Use Cloudflare.";

  options.cloudflare.noProxyDomains = lib.mkOption {
    type = lib.types.listOf lib.types.str;
    description = "Domains to use for dyndns without CDN proxying.";
    default = [ ];
  };

  config = lib.mkIf config.cloudflare.enable {

    # Forces Caddy to error if coming from a non-Cloudflare IP
    caddy.cidrAllowlist = cloudflareIpRanges;

    # Tell Caddy to use Cloudflare DNS for ACME challenge validation
    services.caddy.package = pkgs.caddy-cloudflare; # Patched overlay
    caddy.tlsPolicies = [{
      issuers = [{
        module = "acme";
        challenges = {
          dns = {
            provider = {
              name = "cloudflare";
              api_token = "{env.CLOUDFLARE_API_TOKEN}";
            };
            resolvers = [ "1.1.1.1" ];
          };
        };
      }];
    }];
    # Allow Caddy to read Cloudflare API key for DNS validation
    systemd.services.caddy.serviceConfig.EnvironmentFile =
      config.secrets.cloudflare-api.dest;

    # API key must have access to modify Cloudflare DNS records
    secrets.cloudflare-api = {
      source = ../../../private/cloudflare-api.age;
      dest = "${config.secretsDirectory}/cloudflare-api";
      owner = "caddy";
      group = "caddy";
    };

    # Wait for secret to exist
    systemd.services.caddy = {
      after = [ "cloudflare-api-secret.service" ];
      requires = [ "cloudflare-api-secret.service" ];
    };

    # Allows Nextcloud to trust Cloudflare IPs
    services.nextcloud.settings.trusted_proxies = cloudflareIpRanges;

    # Allows Transmission to trust Cloudflare IPs
    services.transmission.settings.rpc-whitelist =
      builtins.concatStringsSep "," ([ "127.0.0.1" ] ++ cloudflareIpRanges);

    services.cloudflare-dyndns = lib.mkIf
      ((builtins.length config.services.cloudflare-dyndns.domains) > 0) {
        enable = true;
        proxied = true;
        deleteMissing = true;
        apiTokenFile = config.secrets.cloudflare-api.dest;
      };

    # Wait for secret to exist to start
    systemd.services.cloudflare-dyndns =
      lib.mkIf config.services.cloudflare-dyndns.enable {
        after = [ "cloudflare-api-secret.service" ];
        requires = [ "cloudflare-api-secret.service" ];
      };

    # Run a second copy of dyn-dns for non-proxied domains
    # Adapted from: https://github.com/NixOS/nixpkgs/blob/nixos-unstable/nixos/modules/services/networking/cloudflare-dyndns.nix
    systemd.services.cloudflare-dyndns-noproxy =
      lib.mkIf ((builtins.length config.cloudflare.noProxyDomains) > 0) {
        description = "CloudFlare Dynamic DNS Client (no proxy)";
        after = [ "network.target" "cloudflare-api-secret.service" ];
        requires = [ "cloudflare-api-secret.service" ];
        wantedBy = [ "multi-user.target" ];
        startAt = "*:0/5";

        environment = {
          CLOUDFLARE_DOMAINS = toString config.cloudflare.noProxyDomains;
        };

        serviceConfig = {
          Type = "simple";
          DynamicUser = true;
          StateDirectory = "cloudflare-dyndns-noproxy";
          EnvironmentFile = config.services.cloudflare-dyndns.apiTokenFile;
          ExecStart = let
            args =
              [ "--cache-file /var/lib/cloudflare-dyndns-noproxy/ip.cache" ]
              ++ (if config.services.cloudflare-dyndns.ipv4 then
                [ "-4" ]
              else
                [ "-no-4" ]) ++ (if config.services.cloudflare-dyndns.ipv6 then
                  [ "-6" ]
                else
                  [ "-no-6" ])
              ++ lib.optional config.services.cloudflare-dyndns.deleteMissing
              "--delete-missing";

          in "${pkgs.cloudflare-dyndns}/bin/cloudflare-dyndns ${toString args}";
        };
      };

  };
}