#! /bin/sh
set -euf

main() {
  case "$1" in
    (deploy)
      "$@"
      ;;
    (*)
      echo "$0: unknown command: $1" >&2
      exit 23
  esac
}

# deploy : nix-file x hostname -> ()
deploy() {(
  main=$1
  target=$2

  hosts=$(list_hosts)
  imports=$(set -euf; list_imports "$main")
  secrets=$(echo "$imports" | xargs cat | quoted_strings | filter_secrets)

  abs_deps=$(
    echo "$hosts"
    echo "$imports"
    echo "$secrets"
  )

  rel_deps=$(echo "$abs_deps" | make_relative_to "$PWD")
  filter=$(echo "$rel_deps" | make_rsync_whitelist)

  echo "$filter" \
    | rsync -f '. -' -zvrlptD --delete-excluded ./ "$target":/etc/nixos/
  ssh "$target" nixos-rebuild switch -I nixos-config=/etc/nixos/"$main"
)}

# list_imports : nix-file -> lines nix-file
list_imports() {
  if echo "$1" | grep -q ^/; then
    :
  else
    set -- "./$1"
  fi
  imports=$(nix-instantiate \
      --strict \
      --json \
      --eval \
      -E \
      "with builtins; with import ./lib/modules.nix; map toString (list-imports $1)")
  echo "$imports" \
    | jq -r .[]
}

# list_hosts : lines tinc-host-file
# Precondition: $PWD/hosts is the correct repository :)
list_hosts() {
  git -C hosts ls-tree --name-only HEAD \
    | awk '{print ENVIRON["PWD"]"/hosts/"$$0}'
}

# filter_secrets : lines string |> lines secrets-file-candidate
# Notice how false positives are possible.
filter_secrets() {
  sed -n 's:^\(.*/\)\?\(secrets/.*\):'"${PWD//:/\\:}"'/\2:p'
}


# quoted_strings : lines string |> lines string
# Extract all (double-) quoted strings from stdin.
#
# 0. find begin of string or skip line
# 1. find end of string or skip line
# 2. print string and continue after string
quoted_strings() {
  sed '
        s:[^"]*"::                  ;t1;d
    :1; s:\(\([^"]\|\\"\)*\)":\1\n: ;t2;d
    :2; P;D
  ' \
    | sed 's:\\":":g'
}

# bre_escape : lines string |> lines bre-escaped-string
bre_escape() {
  sed 's:[\.\[\\\*\^\$]:\\&:g'
}

# ls_bre : directory -> BRE
# Create a BRE from the files in a directory.
ls_bre() {
  ls "$1" \
    | tr \\n / \
    | sed '
        s:[\.\[\\\*\^\$]:\\&:g
        s:/$::
        s:/:\\|:g
      '
}

# make_relative_to : lines path |> directory -> lines path
# Non-matching paths won't get altered.
make_relative_to() {
  sed "s:^$(echo "$1/" | bre_escape | sed 's/:/\\:/g')::"
}

# make_rsync_whitelist : lines rel-path |> liens rsync-filter
make_rsync_whitelist() {
  set -- "$(cat)"

  # include all files in stdin and their directories
  {
    echo "$1"
    echo "$1" | make_parent_dirs | sort | uniq
  } \
    | sed 's|^|+ /|'

  # exclude everything else
  echo '- *'
}

# make_parent_dirs : lines path |> lines directory
# List all parent directories of a path.
make_parent_dirs() {
  set -- "$(sed -n 's|/[^/]*$||p' | grep . | sort | uniq)"
  if echo "$1" | grep -q .; then
    echo "$1"
    echo "$1" | make_parent_dirs
  fi
}

if [ "${noexec-}" != 1 ]; then
  main "$@"
fi