{ lib, pkgs, cfg, models, allPhones, backgroundEntries }:

let
  hasTrunk = cfg.sipTrunks != {};

  # Page extensions for the intercom button auto-dial
  pageExtension =
    let pages = lib.attrNames (lib.filterAttrs (_: e: e.mode == "page") cfg.extensions);
    in if pages != [] then lib.head pages else null;

  hasIntercomButton = cfg.intercomPrefix != null && pageExtension != null;

  # Collect all internal extension numbers to generate exact-match patterns.
  # This tells the phone "this number is complete" so it dials immediately
  # rather than waiting for the timeout or firing on the first digit.
  allExtensions = lib.unique (
    lib.mapAttrsToList (_: p: p.extension) cfg.sharedPhones
    ++ lib.mapAttrsToList (_: p: p.extension) cfg.persons
  );

  # Star extensions: intercom prefix + each extension, plus custom extensions.
  allStarExtensions =
    (lib.optionals (cfg.intercomPrefix != null)
      (map (ext: "${cfg.intercomPrefix}${ext}") allExtensions))
    ++ lib.attrNames cfg.extensions
    ++ lib.optional (cfg.sharedMailbox != null) cfg.sharedMailbox.checkExtension;

  # Generate the dial template for a phone, given its intercom lineIndex.
  # The lineIndex is derived from familyLineEnabled — the same condition used
  # in the Cisco template for button layout, so both are always in sync.
  #
  # Pattern evaluation: the phone tests templates top-to-bottom and dials as
  # soon as digits match a pattern with timeout="0", or after the timeout
  # elapses for patterns with timeout > 0.  Explicit patterns must come before
  # the catch-all "." so the phone doesn't fire early on a partial match.
  mkDialplanXml = key: intercomLineIndex:
    let
      # Stable UUID derived from a hash of all inputs that affect this dialplan.
      # Changes whenever extensions, trunk config, or intercom config changes,
      # causing phones to reload the file. Format: 8-4-4-4-12 hex chars.
      h = builtins.hashString "sha256" (builtins.toJSON {
        inherit key allExtensions allStarExtensions hasTrunk hasIntercomButton intercomLineIndex;
      });
      versionStamp = "${builtins.substring 0 8 h}-${builtins.substring 8 4 h}-${builtins.substring 12 4 h}-${builtins.substring 16 4 h}-${builtins.substring 20 12 h}";

      # Exact-match a complete extension number — dial immediately.
      extTemplate  = ext: "  <TEMPLATE match=\"${ext}\" timeout=\"0\" />";
    in ''
    <dialTemplate>
      <versionStamp>${versionStamp}</versionStamp>
    ${lib.optionalString hasIntercomButton
      "  <TEMPLATE match=\"\" timeout=\"0\" rewrite=\"${pageExtension}\" line=\"${toString intercomLineIndex}\" />"}
    ${lib.concatMapStrings (ext: extTemplate ext + "\n") allExtensions}
    ${lib.concatMapStrings (ext: extTemplate ext + "\n") allStarExtensions}
      <TEMPLATE match=".." timeout="5" />
    </dialTemplate>
  '';

in
pkgs.linkFarm "voip-tftp-root" (
  lib.concatLists (lib.mapAttrsToList (key: phone:
    let m = models.${phone.model}; in
    lib.optionals m.hasProvisioning (
      let
        upperKey          = lib.toUpper key;
        familyLineEnabled = hasTrunk && phone.personKey != null;
        intercomLineIndex = if familyLineEnabled then 3 else 2;
        dialplanFilename  = "dialplan-${upperKey}.xml";

        xml = m.template ({
          mac           = key;
          inherit (phone) label password displayName;
          serverAddress = cfg.serverAddress;
          ntpServer     = cfg.ntpServer;
          sipPort       = cfg.sipPort;
          directoryPort = cfg.directoryPort;
          dialplanFile  = dialplanFilename;
        } // lib.optionalAttrs (cfg.intercomPrefix != null) {
          intercomEnabled  = true;
          intercomPassword = phone.password;
        } // lib.optionalAttrs familyLineEnabled {
          inherit familyLineEnabled;
          familyLineLabel    =
            if cfg.sharedMailbox != null
              then cfg.sharedMailbox.displayName
              else "Familie";
          familyLinePassword = phone.password;
        });
      in [
        { name = "SEP${upperKey}.cnf.xml";
          path = pkgs.writeText "SEP${upperKey}.cnf.xml" xml; }
        { name = dialplanFilename;
          path = pkgs.writeText dialplanFilename (mkDialplanXml key intercomLineIndex); }
      ]
    )
  ) allPhones)
  ++ backgroundEntries
)