stockholm/lib/git.nix

{ lib, pkgs, ... }:

let
  inherit (lib) addNames escapeShellArg makeSearchPath;

  commands = addNames {
    git-receive-pack = {};
    git-upload-pack = {};
  };

  receive-modes = addNames {
    fast-forward = {};
    non-fast-forward = {};
    create = {};
    delete = {};
    merge = {}; # TODO implement in git.nix
  };

  permissions = {
    fetch = {
      allow-commands = [
        commands.git-upload-pack
      ];
    };

    push = ref: extra-modes: {
      allow-commands = [
        commands.git-receive-pack
        commands.git-upload-pack
      ];
      allow-receive-ref = ref;
      allow-receive-modes = [ receive-modes.fast-forward ] ++ extra-modes;
    };
  };

  refs = {
    master = "refs/heads/master";
    all-heads = "refs/heads/*";
  };

  irc-announce-script = pkgs.writeScript "irc-announce-script" ''
    #! /bin/sh
    set -euf

    export PATH=${makeSearchPath "bin" (with pkgs; [
      coreutils
      gawk
      gnused
      netcat
    ])}

    IRC_SERVER="$1"
    IRC_PORT="$2"
    IRC_NICK="$3"
    IRC_CHANNEL="$4"
    message=$5

    export IRC_CHANNEL # for privmsg_cat

    # echo2 and cat2 are used output to both, stdout and stderr
    # This is used to see what we send to the irc server. (debug output)
    echo2() { echo "$*"; echo "$*" >&2; }
    cat2() { tee /dev/stderr; }

    # privmsg_cat transforms stdin to a privmsg
    privmsg_cat() { awk '{ print "PRIVMSG "ENVIRON["IRC_CHANNEL"]" :"$0 }'; }

    # ircin is used to feed the output of netcat back to the "irc client"
    # so we can implement expect-like behavior with sed^_^
    # XXX mkselfdestructingtmpfifo would be nice instead of this cruft
    tmpdir="$(mktemp -d irc-announce_XXXXXXXX)"
    cd "$tmpdir"
    mkfifo ircin
    trap "
      rm ircin
      cd '$OLDPWD'
      rmdir '$tmpdir'
      trap - EXIT INT QUIT
    " EXIT INT QUIT

    {
      echo2 "USER $LOGNAME 0 * :$LOGNAME@$(hostname)"
      echo2 "NICK $IRC_NICK"

      # wait for MODE message
      sed -n '/^:[^ ]* MODE /q'

      echo2 "JOIN $IRC_CHANNEL"

      printf '%s' "$message" \
        | privmsg_cat \
        | cat2

      echo2 "PART $IRC_CHANNEL"

      # wait for PART confirmation
      sed -n '/:'"$IRC_NICK"'![^ ]* PART /q'

      echo2 'QUIT :Gone to have lunch'
    } < ircin \
      | nc "$IRC_SERVER" "$IRC_PORT" | tee -a ircin
  '';

  hooks = {
    # TODO make this a package?
    irc-announce = { nick, channel, server, port ? 6667 }: ''
      #! /bin/sh
      set -euf

      export PATH=${makeSearchPath "bin" (with pkgs; [
        coreutils
        git
        gnused
      ])}

      nick=${escapeShellArg nick}
      channel=${escapeShellArg channel}
      server=${escapeShellArg server}
      port=${toString port}

      empty=0000000000000000000000000000000000000000

      unset message
      while read oldrev newrev ref; do

        if [ $oldrev = $empty ]; then
          receive_mode=create
        elif [ $newrev = $empty ]; then
          receive_mode=delete
        elif [ "$(git merge-base $oldrev $newrev)" = $oldrev ]; then
          receive_mode=fast-forward
        else
          receive_mode=non-fast-forward
        fi

        h=$(echo $ref | sed 's:^refs/heads/::')

        # empty_tree=$(git hash-object -t tree /dev/null
        empty_tree=4b825dc6

        id=$(echo $newrev | cut -b-7)
        id2=$(echo $oldrev | cut -b-7)
        if [ $newrev = $empty ]; then id=$empty_tree; fi
        if [ $oldrev = $empty ]; then id2=$empty_tree; fi

        case $receive_mode in
          create)
            #git log --oneline $id2
            link="http://cd/cgit/$GIT_SSH_REPO/"
            ;;
          fast-forward|non-fast-forward)
            #git diff --stat $id..$id2
            link="http://cd/cgit/$GIT_SSH_REPO/diff/?h=$h&id=$id&id2=$id2"
            ;;
        esac

        #host=$nick
        #$host $GIT_SSH_REPO $ref $link
        message="''${message+$message
      }$GIT_SSH_USER $receive_mode pushed $link"
      done

      if test -n "''${message-}"; then
        exec ${irc-announce-script} \
          "$server" \
          "$port" \
          "$nick" \
          "$channel" \
          "$message"
      fi
    '';
  };

in
commands // receive-modes // permissions // refs // hooks