#!/usr/bin/env bash
#
# Summary: Generate a python-build definition for a saved binary archive
#
# Usage: pyenv binary generate-installer <metadata-file> --archive-url <url> [-o <output>]
#
#   Reads a metadata file written by `pyenv binary save' and emits a python-build
#   definition. Dropped into python-build's definition directory, it installs the
#   archive like any other version: `pyenv install' downloads it from <url>,
#   checks the platform and the required system libraries, unpacks it, then
#   rewrites rpaths so the copy runs from its prefix.
#
#   The archive must sit next to the metadata file so its checksum can be baked
#   into the definition; `pyenv binary save' writes the two together.
#
#   <metadata-file>       A .meta file written by `pyenv binary save'.
#                         The corresponsing binary package written by `pyenv binary save'
#                         needs to be present alongside it.
#   --archive-url <url>   The URL for the resulting installation script to download
#                         the package from.
#   -o <output>           Write the definition here (default: stdout).
#
set -e
[ -n "$PYENV_DEBUG" ] && set -x

# Provide pyenv completions
if [ "$1" = "--complete" ]; then
  echo --archive-url
  echo -o
  exit
fi

metadata=""
archive_url=""
output=""

while [ $# -gt 0 ]; do
  case "$1" in
  --archive-url )
    [ $# -ge 2 ] || { echo "pyenv-binary: --archive-url needs a value" >&2; exit 1; }
    archive_url="$2"; shift 2 ;;
  -o )
    [ $# -ge 2 ] || { echo "pyenv-binary: -o needs a value" >&2; exit 1; }
    output="$2"; shift 2 ;;
  -* )
    echo "pyenv-binary: unknown option \`$1'" >&2; exit 1 ;;
  * )
    [ -z "$metadata" ] || { echo "pyenv-binary: unexpected argument \`$1'" >&2; exit 1; }
    metadata="$1"; shift ;;
  esac
done

if [ -z "$metadata" ] || [ -z "$archive_url" ]; then
  pyenv-help --usage binary-generate-installer >&2
  exit 1
fi

version="" os="" arch="" distro="" libc="" archive=""
deps=""
while IFS='=' read -r key value; do
  case "$key" in
  version ) version="$value" ;;
  os ) os="$value" ;;
  arch ) arch="$value" ;;
  distro ) distro="$value" ;;
  libc ) libc="$value" ;;
  archive ) archive="$value" ;;
  dep ) deps="${deps:+$deps }$value" ;;
  esac
done < "$metadata"

# Fail here if the metadata is incomplete, rather than bake a blank into the
# definition where a missing arch would give a confusing platform error.
for field in version os arch archive; do
  if [ -z "${!field}" ]; then
    echo "pyenv-binary: metadata is missing \`${field}'" >&2
    exit 1
  fi
done

# macOS relocation needs install_name_tool and a different rpath scheme, so it is
# not supported yet. Other systems relocate with patchelf.
if [ "$os" = "Darwin" ]; then
  echo "pyenv-binary: macOS archives are not supported yet" >&2
  exit 1
fi

# The glibc floor only applies on Linux; require it there so the definition can
# tell whether the target is new enough to run the binaries.
if [ "$os" = "Linux" ] && [ -z "$libc" ]; then
  echo "pyenv-binary: metadata is missing \`libc'" >&2
  exit 1
fi

# python-build downloads the archive itself, so the checksum has to be baked in.
# The archive sits next to the metadata `save' wrote it alongside.
archive_path="$(dirname "$metadata")/${archive}"
if [ ! -r "$archive_path" ]; then
  echo "pyenv-binary: cannot read the archive \`${archive_path}' to checksum it" >&2
  exit 1
fi
if command -v sha256sum >/dev/null 2>&1; then
  sha256="$(sha256sum "$archive_path")"; sha256="${sha256%% *}"
elif command -v shasum >/dev/null 2>&1; then
  sha256="$(shasum -a 256 "$archive_path")"; sha256="${sha256%% *}"
elif command -v openssl >/dev/null 2>&1; then
  sha256="$(openssl dgst -sha256 "$archive_path")"; sha256="${sha256##* }"
else
  echo "pyenv-binary: need sha256sum, shasum or openssl to checksum the archive" >&2
  exit 1
fi

emit() {
  # The values known now go in as %q-quoted assignments so a stray quote or space
  # in the URL or metadata cannot break the definition or inject into it. The body
  # below is a quoted here-doc, verbatim.
  {
    printf '# python-build definition for prebuilt Python %s (%s/%s%s).\n' \
      "$version" "$os" "$arch" "${distro:+, $distro}"
    echo "# Generated by \`pyenv binary generate-installer'."
    echo
    printf 'EXPECT_OS=%q\n' "$os"
    printf 'EXPECT_ARCH=%q\n' "$arch"
    printf 'EXPECT_LIBC=%q\n' "$libc"
    printf 'VERSION=%q\n' "$version"
    printf 'ARCHIVE_URL=%q\n' "$archive_url"
    printf 'SHA256=%q\n' "$sha256"
    printf 'DEPS=%q\n' "$deps"
  }
  cat <<'EOF'

os="$(uname -s)"
arch="$(uname -m)"
if [ "$os" != "$EXPECT_OS" ] || [ "$arch" != "$EXPECT_ARCH" ]; then
  echo "pyenv-binary: this archive is for ${EXPECT_OS}/${EXPECT_ARCH}, not ${os}/${arch}" >&2
  exit 1
fi

# Refuse a target whose glibc is older than the one the archive was built on;
# the dynamic loader would reject the binaries.
case "$EXPECT_LIBC" in
"glibc "* )
  build_libc="${EXPECT_LIBC#glibc }"
  target_libc="$(getconf GNU_LIBC_VERSION 2>/dev/null || true)"
  case "$target_libc" in
  "glibc "* )
    target_libc="${target_libc#glibc }"
    older="$(printf '%s\n%s\n' "$build_libc" "$target_libc" | sort -V | head -n1)"
    if [ "$older" = "$target_libc" ] && [ "$target_libc" != "$build_libc" ]; then
      echo "pyenv-binary: archive needs glibc ${build_libc} or newer, but this system has ${target_libc}" >&2
      exit 1
    fi
    ;;
  esac
  ;;
esac

# Required system libraries must already be present on the target. ldconfig -p
# lists each library as "<soname> (...) => <path>"; match the soname column
# exactly so a longer name like libc.so.6.1 does not satisfy libc.so.6.
if command -v ldconfig &>/dev/null && cache="$(ldconfig -p)"; then
  missing=""
  for dep in $DEPS; do
    printf '%s\n' "$cache" | awk -v d="$dep" '$1 == d { found = 1 } END { exit !found }' \
      || missing="${missing} ${dep}"
  done
  if [ -n "$missing" ]; then
    echo "pyenv-binary: missing required system libraries:${missing}" >&2
    exit 1
  fi
elif [ -n "$DEPS" ]; then
  echo "pyenv-binary: cannot check required system libraries (ldconfig with -p not found)" >&2
fi

build_package_relocate() {
  pyenv binary relocate "$PREFIX_PATH"
}

install_package "Python-${VERSION}-binary" "${ARCHIVE_URL}#${SHA256}" copy relocate

EOF
}

if [ -n "$output" ]; then
  emit > "$output"
  echo "Wrote definition to ${output}"
else
  emit
fi