{
  lib,
  config,
  pkgs,
  ...
}:
let
  cfg = config.services.hyperhive.tls;
  hyperhiveCfg = config.services.hyperhive;
  gatewayCfg = config.services.hyperhive.gateway;
  domain = hyperhiveCfg.domain;

  # The host-managed hive CA is the trust anchor for self-signed mode.
  # It is only stood up when the gateway actually serves a self-signed
  # cert: the gateway must be in self-signed mode. `domain` is required
  # (asserted in hive-network.nix), so the leaf SANs always have a
  # domain to derive from. The self-signed condition is the gateway
  # module's single source of truth (`gateway.useSelfSigned`): true when
  # neither an operator cert (`tls.certDir`) nor ACME is set.
  active = hyperhiveCfg.enable && gatewayCfg.useSelfSigned;
in
{
  # Host-side TLS trust root for the self-signed gateway mode.
  #
  # `gateway.selfSignedTls` historically generated a *bare* self-signed
  # leaf inside the gateway container at first boot. A bare leaf is its
  # own trust anchor, so every regeneration is a new anchor and every
  # consumer (agents, federation peers) would have to re-trust on each
  # rotation — and a runtime-generated, in-container cert can't be wired
  # into an agent's build-time trust store at all.
  #
  # This module moves the anchor to a long-lived **hive CA** held on the
  # host. The gateway serves a **leaf** signed by that CA (via the
  # existing `tls.certDir` bind-mount path); agents and federation peers
  # trust the *CA* once, and leaf rotation never re-breaks them. See
  # `docs/gateway.md` ("Self-signed TLS") and issue-tracker discussion of
  # agent web-UI reachability.

  options.services.hyperhive.tls = {
    stateDir = lib.mkOption {
      type = lib.types.str;
      default = "/var/lib/hive-tls";
      description = ''
        Host directory holding the hive CA + gateway leaf cert for the
        self-signed gateway mode. `ca.pem` (the anchor agents and
        federation peers trust), `ca-key.pem` (0600, never leaves the
        host), `gateway.pem` / `gateway-key.pem` (the leaf the gateway
        container bind-mounts and nginx serves). Persistent so the CA
        survives reboots — re-deriving it would re-break every consumer.
      '';
    };

    caValidityDays = lib.mkOption {
      type = lib.types.int;
      default = 7300;
      description = ''
        Validity window of the hive CA in days (default ~20y). Kept long
        and well beyond `leafValidityDays` so the CA outlives many leaf
        rotations — the whole point of the CA is to be a stable anchor
        that consumers trust once. The CA is regenerated only if missing
        or already expired.
      '';
    };

    leafValidityDays = lib.mkOption {
      type = lib.types.int;
      default = 30;
      description = ''
        Validity window of the gateway leaf cert in days (default 30).
        Short-lived by design — ahead of the CA/Browser-Forum's move
        toward ~47-day max lifetimes — which bounds the blast radius of a
        leaf-key compromise. The leaf is re-signed by the (stable) CA
        when it is missing or near expiry; because it shares the CA
        anchor, a rotation does not disturb consumer trust. Agents and
        federation peers validate against the CA, not browser CA/B-forum
        limits. The weekly `hive-tls-resign` timer re-signs the leaf once
        it is within half its validity of expiry and propagates the new
        leaf into the running gateway, so a long-uptime host renews
        automatically without a reboot.
      '';
    };
  };

  config = lib.mkIf active {
    # Generate (and rotate) the hive CA + gateway leaf before the gateway
    # container starts. Idempotent: the CA is created once and reused; the
    # leaf is re-signed on expiry under the same CA so the anchor is stable.
    systemd.services.hive-tls-ca = {
      description = "Generate hive CA + gateway leaf TLS cert (self-signed mode)";
      wantedBy = [ "multi-user.target" ];
      # Gateway nginx reads the leaf from the bind-mount, so the cert must
      # exist before the container starts. Declarative nixos-containers are
      # instances of the `container@.service` template.
      before = [ "container@hive-gateway.service" ];
      requiredBy = [ "container@hive-gateway.service" ];
      path = [ pkgs.openssl ];
      serviceConfig = {
        Type = "oneshot";
        RemainAfterExit = true;
        UMask = "0077";
        # Pin the journal identity (else it's the `script` store-path wrapper).
        SyslogIdentifier = "hive-tls-ca";
      };
      script = ''
        set -euo pipefail
        d=${lib.escapeShellArg cfg.stateDir}
        install -d -m 0755 "$d"

        ca="$d/ca.pem"
        cak="$d/ca-key.pem"
        leaf="$d/gateway.pem"
        leafk="$d/gateway-key.pem"

        # --- CA: generate once, reuse across leaf rotations. Regenerate
        # only if missing or already expired (checkend 0). A new CA means
        # every consumer must re-trust, so the leaf is dropped to force a
        # re-sign under the fresh CA.
        if [ ! -s "$ca" ] || [ ! -s "$cak" ] \
            || ! openssl x509 -in "$ca" -noout -checkend 0 >/dev/null 2>&1; then
          echo "generating fresh hive CA at $ca"
          openssl req -x509 -newkey rsa:4096 -nodes -sha256 \
            -days ${toString cfg.caValidityDays} \
            -keyout "$cak" -out "$ca" \
            -subj "/CN=hive-ca ${domain}" \
            -addext "basicConstraints=critical,CA:TRUE,pathlen:0" \
            -addext "keyUsage=critical,keyCertSign,cRLSign"
          chmod 0600 "$cak"
          chmod 0644 "$ca"
          rm -f "$leaf" "$leafk"
        fi

        # --- Leaf: (re)sign when missing or within 30 days of expiry,
        # always under the current (stable) CA.
        if [ ! -s "$leaf" ] || [ ! -s "$leafk" ] \
            || ! openssl x509 -in "$leaf" -noout -checkend 2592000 >/dev/null 2>&1; then
          echo "signing fresh gateway leaf at $leaf"
          csr="$(mktemp "$d/gateway.csr.XXXXXX")"
          ext="$(mktemp "$d/leaf.ext.XXXXXX")"
          trap 'rm -f "$csr" "$ext"' EXIT

          openssl req -newkey rsa:4096 -nodes -sha256 \
            -keyout "$leafk" -out "$csr" \
            -subj "/CN=${domain}"

          # printf (not a heredoc) so the ext-file lines carry no leading
          # whitespace once nix has stripped the indented-string indent.
          {
            printf 'subjectAltName=DNS:%s,DNS:forge.%s,DNS:matrix.%s,DNS:*.%s\n' \
              ${lib.escapeShellArg domain} ${lib.escapeShellArg domain} \
              ${lib.escapeShellArg domain} ${lib.escapeShellArg domain}
            printf 'basicConstraints=critical,CA:FALSE\n'
            printf 'keyUsage=critical,digitalSignature,keyEncipherment\n'
            printf 'extendedKeyUsage=serverAuth\n'
          } > "$ext"

          openssl x509 -req -in "$csr" -CA "$ca" -CAkey "$cak" \
            -CAcreateserial -days ${toString cfg.leafValidityDays} -sha256 \
            -extfile "$ext" -out "$leaf"
          chmod 0600 "$leafk"
          chmod 0644 "$leaf"
        fi
      '';
    };

    # Weekly re-sign of the gateway leaf so short-lived leaves renew
    # without depending on a reboot.
    #
    # `hive-tls-ca` only re-signs at service activation (boot/rebuild); a
    # long-uptime host would otherwise let a 30-day leaf lapse silently.
    # This service re-signs the leaf directly (not by bouncing hive-tls-ca)
    # and propagates the new leaf into the running gateway container when
    # the file actually changed.
    #
    # Propagation mechanism: nginx in the gateway container serves a *copy*
    # of the leaf written by `hive-gateway-self-signed-cert` (which runs at
    # container start). A host-side `systemctl -M hive-gateway` call
    # triggers the re-import + reload, mirroring how hive-c0re reloads the
    # gateway after each agents.conf write. A path unit *inside* the
    # container was tried first but does not work: IN_MOVED_TO from an
    # atomic rename on the host does not propagate across the nspawn
    # mount-namespace boundary.
    #
    # `|| true` on propagation so a stopped gateway never fails the unit —
    # its next boot will import the already-rotated leaf anyway.
    systemd.services.hive-tls-resign = {
      description = "Re-sign the gateway TLS leaf and propagate it into the gateway container";
      # hive-tls-ca must have run first so the CA key exists before we try
      # to re-sign under it. On first boot `Persistent=true` on the weekly
      # timer fires immediately; without this ordering the resign could race
      # the CA initialisation and fail with "no such file" on the CA key.
      after = [ "hive-tls-ca.service" ];
      path = [
        pkgs.openssl
        pkgs.coreutils
        pkgs.systemd
      ];
      serviceConfig = {
        Type = "oneshot";
        UMask = "0077";
        SyslogIdentifier = "hive-tls-resign";
      };
      script = ''
        set -euo pipefail
        d=${lib.escapeShellArg cfg.stateDir}
        ca="$d/ca.pem"
        cak="$d/ca-key.pem"
        leaf="$d/gateway.pem"
        leafk="$d/gateway-key.pem"

        # Re-sign only when the leaf is within half its validity of expiry.
        # The weekly cadence catches this window well before the leaf lapses.
        halflife=$(( ${toString cfg.leafValidityDays} * 86400 / 2 ))
        if [ -s "$leaf" ] && \
            openssl x509 -in "$leaf" -noout -checkend "$halflife" >/dev/null 2>&1; then
          echo "gateway leaf valid for more than half its lifetime — no resign needed"
          exit 0
        fi

        echo "gateway leaf missing or near expiry — re-signing under current CA"
        before="$(sha256sum "$leaf" 2>/dev/null || true)"

        csr="$(mktemp "$d/gateway.csr.XXXXXX")"
        ext="$(mktemp "$d/leaf.ext.XXXXXX")"
        trap 'rm -f "$csr" "$ext"' EXIT

        openssl req -newkey rsa:4096 -nodes -sha256 \
          -keyout "$leafk" -out "$csr" \
          -subj "/CN=${domain}"

        {
          printf 'subjectAltName=DNS:%s,DNS:forge.%s,DNS:matrix.%s,DNS:*.%s\n' \
            ${lib.escapeShellArg domain} ${lib.escapeShellArg domain} \
            ${lib.escapeShellArg domain} ${lib.escapeShellArg domain}
          printf 'basicConstraints=critical,CA:FALSE\n'
          printf 'keyUsage=critical,digitalSignature,keyEncipherment\n'
          printf 'extendedKeyUsage=serverAuth\n'
        } > "$ext"

        openssl x509 -req -in "$csr" -CA "$ca" -CAkey "$cak" \
          -CAcreateserial -days ${toString cfg.leafValidityDays} -sha256 \
          -extfile "$ext" -out "$leaf"
        chmod 0600 "$leafk"
        chmod 0644 "$leaf"

        after="$(sha256sum "$leaf" 2>/dev/null || true)"
        if [ "$before" != "$after" ]; then
          echo "gateway leaf rotated — propagating into hive-gateway"
          systemctl -M hive-gateway restart hive-gateway-self-signed-cert.service || true
          systemctl -M hive-gateway reload nginx.service || true
        else
          echo "gateway leaf unchanged (already up to date)"
        fi
      '';
    };

    systemd.timers.hive-tls-resign = {
      description = "Weekly gateway-leaf re-sign and propagation";
      wantedBy = [ "timers.target" ];
      timerConfig = {
        # Run weekly; Persistent=true fires a missed run on next boot if
        # the timer was not active (e.g. the host was off on the scheduled
        # day), preventing a dormant timer from letting the leaf lapse.
        OnCalendar = "weekly";
        Persistent = true;
      };
    };

    # Signal the hive-c0re lifecycle that a hive CA exists: it bind-mounts
    # this file (read-only, the CA cert ONLY — never the key) into each
    # agent container so agents + their tools can trust the gateway's
    # self-signed leaf, and the meta flake wires the per-agent trust
    # bundle. Only the `ca.pem` path is exposed; `ca-key.pem` stays on the
    # host (an agent that could read it could mint trusted certs).
    systemd.services.hive-c0re.environment.HIVE_TLS_CA_PATH = "${cfg.stateDir}/ca.pem";
  };
}