# This agent's accounts on external forges, fetched from the swarm secret store
# by the agent itself, into the files `hive-forge -f <label>` reads.
#
# An operator links an account in the swarm UI; `swarm-controller` stores it at
# `swarm/agents/<agent>/forge/<label>` (`swarm_secret_client::forge`). The
# agent's grant lists and reads its own subtree, so this unit lists
# `swarm/agents/<agent>/forge/`, reads each account, and writes
# `<state>/forge-<label>-token` and `<state>/forge-<label>.json`
# (`{"base_url":…}`), the two files `hive-forge`'s `resolve_credentials` reads.
#
# It never deletes. A `forge-<label>` pair for a label not listed is left
# as it is, whoever wrote it, and so is the pair of a label whose read fails.
# A file is replaced by rename, and only when its bytes changed.
{
  pkgs,
  lib,
  config,
  ...
}:
let
  cfg = config.services.hyperhive.agent.bao;

  agentName = config.services.hyperhive.agent.user.name;
  stateDir = "/agents/${agentName}/state";

  # The same three ids ./bao.nix and ./forge-token.nix load.
  certCredential = "hive-agent-bao-cert";
  keyCredential = "hive-agent-bao-key";
  serverCaCredential = "hive-agent-bao-server-ca";

  unitName = "hive-agent-forge-accounts";

  # The nix half of `swarm_secret_client::forge::accounts_dir` plus
  # `path::MOUNT`.
  accountsDir = "secret/swarm/agents/${agentName}/forge";

  runtimeDir = unitName;
  # The store's whole answer for one account, token included: kept in the
  # unit's own `0700` directory, never in the state dir.
  rawFile = "/run/${runtimeDir}/account.json";
  listFile = "/run/${runtimeDir}/list.json";
  errFile = "/run/${runtimeDir}/bao.err";

  configured = cfg.addr != null;

  storeRetry = import ../host-modules/lib/store-retry.nix { };
in
{
  config = lib.mkIf configured {
    systemd.services.${unitName} = {
      description = "fetch this agent's external forge accounts from the secret store";
      after = [
        "network.target"
        "hive-agent-bao-identity.service"
      ];
      wantedBy = [ "multi-user.target" ];
      path = [
        pkgs.openbao
        pkgs.coreutils
        pkgs.diffutils
        pkgs.jq
      ];
      # ../host-modules/lib/store-retry.nix.
      inherit (storeRetry) startLimitBurst startLimitIntervalSec;
      serviceConfig = storeRetry.serviceConfig // {
        Type = "oneshot";
        # Not `RemainAfterExit`, so the timer below can start it again.
        RemainAfterExit = false;
        TimeoutStartSec = 60;
        User = agentName;
        Group = agentName;
        RuntimeDirectory = runtimeDir;
        RuntimeDirectoryMode = "0700";
        # `0600`, the mode the files in the state dir have always had.
        UMask = "0077";
        LoadCredential = [
          certCredential
          keyCredential
          serverCaCredential
        ];
      };
      environment = {
        BAO_ADDR = cfg.addr;
        BAO_CLIENT_CERT = "%d/${certCredential}";
        BAO_CLIENT_KEY = "%d/${keyCredential}";
      };
      script = ''
        set -euo pipefail

        # No identity delivered: ./bao.nix's check reports that.
        for id in ${lib.escapeShellArg certCredential} ${lib.escapeShellArg keyCredential}; do
          if [ ! -s "$CREDENTIALS_DIRECTORY/$id" ]; then
            echo "this agent has no store identity, so it cannot fetch its external forge accounts." >&2
            exit 0
          fi
        done

        if [ -s "$CREDENTIALS_DIRECTORY/${serverCaCredential}" ]; then
          export BAO_CACERT="$CREDENTIALS_DIRECTORY/${serverCaCredential}"
        fi

        err=${lib.escapeShellArg errFile}
        raw=${lib.escapeShellArg rawFile}
        list=${lib.escapeShellArg listFile}
        trap 'rm -f "$err" "$raw" "$list"' EXIT

        if ! BAO_TOKEN="$(bao login -method=cert -token-only 2>"$err")"; then
          echo "the swarm secret store at $BAO_ADDR did not accept this agent's certificate login:" >&2
          if [ -s "$err" ]; then cat "$err" >&2; fi
          exit 1
        fi
        export BAO_TOKEN

        # An empty directory is a 404, which `bao` answers with `{}` on stdout
        # and nothing on stderr; a denial or an unreachable store prints
        # nothing on stdout.
        if ! bao kv list -format=json ${lib.escapeShellArg accountsDir} >"$list" 2>"$err"; then
          if [ ! -s "$err" ] && jq -e '. == {}' "$list" >/dev/null 2>&1; then
            echo "no external forge accounts are linked to this agent (nothing under ${accountsDir})."
            exit 0
          fi
          echo "could not list ${accountsDir}:" >&2
          if [ -s "$err" ]; then cat "$err" >&2; fi
          exit 1
        fi
        if ! jq -e 'arrays' "$list" >/dev/null; then
          echo "listing ${accountsDir} returned no array of names." >&2
          exit 1
        fi

        # Moves $1 over $2 and succeeds when the bytes differ; drops $1 otherwise.
        replace() {
          if cmp -s "$1" "$2"; then
            rm -f "$1"
            return 1
          fi
          mv -f "$1" "$2"
        }

        # One account that cannot be read is logged and skipped. It does not
        # stop the others, and failing the unit would only restart it into the
        # same answer.
        while IFS= read -r label; do
          # The label becomes a file name, and `hive-forge -f` names only these.
          # A key ending in `/` is a directory below this one, not an account.
          if [[ ! "$label" =~ ^[a-z0-9-]+$ ]]; then
            echo "skipping listed key $(printf '%q' "$label"): not a label hive-forge -f can name." >&2
            continue
          fi
          path="${accountsDir}/$label"
          if ! bao kv get -format=json "$path" >"$raw" 2>"$err"; then
            echo "could not read $path; forge-$label files left as they are:" >&2
            if [ -s "$err" ]; then cat "$err" >&2; fi
            continue
          fi

          # ⚠️ The token goes from the store's answer straight into a file;
          # it is never in a variable or an argument.
          token=${lib.escapeShellArg stateDir}/forge-$label-token
          sidecar=${lib.escapeShellArg stateDir}/forge-$label.json
          staged_token=${lib.escapeShellArg stateDir}/.forge-$label-token.new
          staged_sidecar=${lib.escapeShellArg stateDir}/.forge-$label.json.new
          rm -f "$staged_token" "$staged_sidecar"
          if ! jq -er '.data.data.value | strings' "$raw" >"$staged_token" \
            || ! jq -cje '{base_url: (.data.data.url | strings)}' "$raw" >"$staged_sidecar"; then
            echo "$path holds no string value and url; forge-$label files left as they are." >&2
            rm -f "$staged_token" "$staged_sidecar"
            continue
          fi

          changed=
          replace "$staged_token" "$token" && changed=1
          replace "$staged_sidecar" "$sidecar" && changed=1
          if [ -n "$changed" ]; then
            echo "fetched external forge account $label from $path."
          fi
        done < <(jq -r '.[]' "$list")
      '';
    };

    # The same cadence as hive-matrix-daemon's re-listing of its own accounts.
    systemd.timers.${unitName} = {
      description = "re-fetch this agent's external forge accounts from the secret store";
      wantedBy = [ "timers.target" ];
      timerConfig = {
        OnUnitInactiveSec = "2min";
        RandomizedDelaySec = "20s";
      };
    };
  };
}