#!/usr/bin/env bash

set -euo pipefail

TARGET_VERSION="${1:-3.11}"
IFS="." read -r PYTHON_MAJOR PYTHON_MINOR _ <<< "${TARGET_VERSION}"

if [[ -n "${PYTHON_MINOR:-}" ]]; then
  PYTHON_BIN="python${PYTHON_MAJOR}.${PYTHON_MINOR}"
else
  PYTHON_BIN="python${PYTHON_MAJOR}"
fi

python_matches() {
  local candidate="$1"
  [[ -x "${candidate}" ]] || return 1
  "${candidate}" - "${PYTHON_MAJOR}" "${PYTHON_MINOR:-}" <<'PY'
import sys

expected_major = int(sys.argv[1])
expected_minor = sys.argv[2]
if sys.version_info.major != expected_major:
    raise SystemExit(1)
if expected_minor and sys.version_info.minor != int(expected_minor):
    raise SystemExit(1)
PY
}

python_has_venv() {
  local candidate="$1"
  "${candidate}" -m venv --help >/dev/null 2>&1
}

print_if_usable() {
  local candidate="$1"
  case "${candidate}" in
    "${PWD}/.venv/"*)
      return 1
      ;;
  esac
  if python_matches "${candidate}" && python_has_venv "${candidate}"; then
    printf '%s\n' "${candidate}"
    exit 0
  fi
}

if command -v "${PYTHON_BIN}" >/dev/null 2>&1; then
  print_if_usable "$(command -v "${PYTHON_BIN}")"
fi

TOOLCACHE_DIR="${RUNNER_TOOL_CACHE:-/opt/hostedtoolcache}"
HOME_DIR="${HOME:-/root}"

shopt -s nullglob
# shellcheck disable=SC2140
for candidate in \
  "${TOOLCACHE_DIR}"/Python/"${PYTHON_MAJOR}.${PYTHON_MINOR}"*/x64/bin/python \
  "${TOOLCACHE_DIR}"/Python/"${PYTHON_MAJOR}.${PYTHON_MINOR}"*/x64/bin/python3 \
  "${TOOLCACHE_DIR}"/uv-python/cpython-"${PYTHON_MAJOR}.${PYTHON_MINOR}"*/bin/python \
  "${HOME_DIR}"/.local/share/uv/python/cpython-"${PYTHON_MAJOR}.${PYTHON_MINOR}"*/bin/python \
  "${HOME_DIR}"/.cache/uv/python/cpython-"${PYTHON_MAJOR}.${PYTHON_MINOR}"*/bin/python; do
  print_if_usable "${candidate}"
done
shopt -u nullglob

APT_RUNNER=()
if [[ "$(id -u)" -ne 0 ]]; then
  APT_RUNNER=(sudo)
fi

export DEBIAN_FRONTEND=noninteractive

if "${APT_RUNNER[@]}" apt-get update >&2 \
  && "${APT_RUNNER[@]}" apt-get install -y "${PYTHON_BIN}" "${PYTHON_BIN}-venv" >&2; then
  print_if_usable "$(command -v "${PYTHON_BIN}")"
fi

install_uv_standalone() {
  if command -v uv >/dev/null 2>&1; then
    command -v uv
    return 0
  fi

  local uv_dir
  uv_dir="$(mktemp -d)"
  local install_url="https://astral.sh/uv/${UV_VERSION:-0.7.2}/install.sh"
  if ! curl -LsSf "${install_url}" | env UV_INSTALL_DIR="${uv_dir}/bin" sh >&2; then
    curl -LsSf "https://astral.sh/uv/install.sh" | env UV_INSTALL_DIR="${uv_dir}/bin" sh >&2
  fi
  printf '%s\n' "${uv_dir}/bin/uv"
}

UV_BIN="$(install_uv_standalone)"
UV_PYTHON_INSTALL_DIR="${TOOLCACHE_DIR:-${HOME_DIR}/.cache}/uv-python" \
  "${UV_BIN}" python install "${TARGET_VERSION}" --no-progress >&2

UV_PYTHON_CANDIDATE="$(
  UV_PYTHON_INSTALL_DIR="${TOOLCACHE_DIR:-${HOME_DIR}/.cache}/uv-python" \
    "${UV_BIN}" python find "${TARGET_VERSION}" --managed-python
)"
print_if_usable "${UV_PYTHON_CANDIDATE}"

if "${APT_RUNNER[@]}" apt-get install -y software-properties-common >&2 \
  && "${APT_RUNNER[@]}" add-apt-repository -y ppa:deadsnakes/ppa >&2 \
  && "${APT_RUNNER[@]}" apt-get update >&2 \
  && "${APT_RUNNER[@]}" apt-get install -y "${PYTHON_BIN}" "${PYTHON_BIN}-venv" >&2; then
  print_if_usable "$(command -v "${PYTHON_BIN}")"
fi

printf 'Unable to install a usable Python %s with venv support\n' "${TARGET_VERSION}" >&2
exit 1