# This runs in a new shell
builtin emulate -L zsh -o EXTENDED_GLOB
readonly -i PRINTLEVEL=${1} SUBMODULES=${8}
readonly ACTION=${2} MODULE=${3} DIR=${4} URL=${5} REV=${7} ONPULL=${9} TEMP=.zdegit_${RANDOM}
readonly TARBALL_TARGET=${DIR}/${TEMP}_tarball.tar.gz INFO_TARGET=${DIR}/.zdegit

print_error() {
  print -u2 -PlR <%= clear_line %>"%F{red}<%= error %>%B${MODULE}:%b ${1}%f" ${2:+${(F):-  ${(f)^2}}}
}

print_okay() {
  if (( PRINTLEVEL > 0 )); then
    local -r log=${2:+${(F):-  ${(f)^2}}}
    if [[ ${SUBMODULES} -ne 0 && -e ${DIR}/.gitmodules ]]; then
      print -u2 -PlR <%= clear_line %>"%F{yellow}<%= warn %>%B${MODULE}:%b ${1}. Module contains git submodules, which are not supported by Zim's degit. Use zmodule option %B--no-submodules%b to disable this warning.%f" ${log}
    else
      print -PlR <%= clear_line %>"<%= okay %>%B${MODULE}:%b ${1}" ${log}
    fi
  fi
}

handle() {
  if [[ -n ${ONPULL} ]]; then
    if ! ERR=$(builtin cd -q ${DIR} 2>&1 && builtin eval ${ONPULL} 2>&1); then
      print_error 'Error during on-pull' ${ERR}
      return 1
    elif [[ ${PRINTLEVEL} -gt 1 && -n ${ERR} ]]; then
      builtin set ${1} ${2:+${2}$'\n'}"On-pull output:"$'\n'${ERR}
    fi
  fi
  print_okay "${@}"
}

download_tarball() {
  local host repo
  if [[ ${URL} =~ <%= url_regex %> ]]; then
    host=${match[3]}
    repo=${match[4]%.git}
  fi
  if [[ ${host} != github.com || -z ${repo} ]]; then
    print_error "${URL} is not a valid GitHub URL. Will not try to ${ACTION}."
    return 1
  fi
  local -r headers_target=${DIR}/${TEMP}_headers
  {
    local info_header header etag
    if [[ -r ${INFO_TARGET} ]]; then
      local -r info=("${(@f)"$(<${INFO_TARGET})"}")
      if [[ ${URL} != ${info[1]} ]]; then
        print_error "URL does not match. Expected ${URL}. Will not try to ${ACTION}."
        return 1
      fi
      # Previous REV is in line 2, reserved for future use.
      info_header=${info[3]}
    fi
    local -r tarball_url=https://api.github.com/repos/${repo}/tarball/${REV}
    if (( ${+commands[curl]} )); then
      if ! ERR=$(command curl -fsSL ${info_header:+-H} ${info_header} -o ${TARBALL_TARGET} -D ${headers_target} ${tarball_url} 2>&1); then
        print_error "Error downloading ${tarball_url} with curl" ${ERR}
        return 1
      fi
    else
      # wget returns 8 when 304 Not Modified, so we cannot use wget's error codes
      command wget -q ${info_header:+--header=${info_header}} -O ${TARBALL_TARGET} -S ${tarball_url} 2>${headers_target}
    fi
    local -i http_code
    while IFS= read -r header; do
      header=${${header## ##}%%$'\r'##}
      if [[ ${header} == HTTP/* ]]; then
        http_code=${${(s: :)header}[2]}
      elif [[ ${${(L)header%%:*}%% ##} == etag ]]; then
        etag=${${header#*:}## ##}
      fi
    done < ${headers_target}
    if (( http_code == 304 )); then
      # Not Modified
      command rm -f ${TARBALL_TARGET} 2>/dev/null
      return 0
    elif (( http_code != 200 )); then
      print_error "Error downloading ${tarball_url}, HTTP code ${http_code}"
      return 1
    fi
    if [[ -z ${etag} ]]; then
      print_error "Error downloading ${tarball_url}, no ETag header found in response"
      return 1
    fi
    if ! print -lR "${URL}" "${REV}" "If-None-Match: ${etag}" >! ${INFO_TARGET} 2>/dev/null; then
      print_error "Error creating or updating ${INFO_TARGET}"
      return 1
    fi
  } always {
    command rm -f ${headers_target} 2>/dev/null
  }
}

untar_tarball() {
  if ! ERR=$(command tar -C ${1} --strip=1 -xzf ${TARBALL_TARGET} 2>&1); then
    print_error "Error extracting ${TARBALL_TARGET}" ${ERR}
    return 1
  fi
}

create_dir() {
  if ! ERR=$(command mkdir -p ${1} 2>&1); then
    print_error "Error creating ${1}" ${ERR}
    return 1
  fi
}

case ${ACTION} in
  install)
    {
      create_dir ${DIR} && download_tarball && untar_tarball ${DIR} && handle Installed
    } always {
      # return 1 does not change ${TRY_BLOCK_ERROR}, only changes ${?}
      (( TRY_BLOCK_ERROR = ? ))
      command rm -f ${TARBALL_TARGET} 2>/dev/null
      if (( TRY_BLOCK_ERROR )) command rm -rf ${DIR} 2>/dev/null
    }
    ;;
  update)
    if [[ ! -r ${INFO_TARGET} ]]; then
      if (( PRINTLEVEL > 0 )); then
        print -u2 -PR <%= clear_line %>"%F{yellow}<%= warn %>%B${MODULE}:%b Module was not installed using Zim's degit. Will not try to update. Use zmodule option %B-z%b|%B--frozen%b to disable this warning.%f"
      fi
      return 0
    fi
    readonly DIR_NEW=${DIR}${TEMP}
    {
      download_tarball || return 1
      if [[ ! -e ${TARBALL_TARGET} ]]; then
        handle 'Already up to date'
        return ${?}
      fi
      create_dir ${DIR_NEW} && untar_tarball ${DIR_NEW} || return 1
      if (( ${+commands[diff]} )); then
        LOG=$(command diff -x '.zdegit*' -x '*.zwc' -x '*.zwc.old' -qr ${DIR} ${DIR_NEW} 2>/dev/null)
        LOG=${${LOG//${DIR_NEW}/new}//${DIR}/old}
      fi
      if ! ERR=$({ command cp -f ${INFO_TARGET} ${DIR_NEW} && \
          command rm -rf ${DIR} && command mv -f ${DIR_NEW} ${DIR} } 2>&1); then
        print_error "Error updating ${DIR}" ${ERR}
        return 1
      fi
      handle Updated ${LOG}
    } always {
      command rm -f ${TARBALL_TARGET} 2>/dev/null
      command rm -rf ${DIR_NEW} 2>/dev/null
    }
    ;;
esac