#!/usr/bin/env bash
# install.sh — install dmigrate to /usr/local/bin/dmigrate
#
# Usage:
#   curl -fsSL <INSTALL_SCRIPT_URL> | bash
#
# Environment:
#   DMIGRATE_URL   Override download URL for dmigrate.sh

set -Eeuo pipefail

INSTALL_TARGET="/usr/local/bin/dmigrate"
INSTALL_SCRIPT_URL="https://gist.githubusercontent.com/mewisme/dd46a582b6131d6543f4336ac7087454/raw/install.sh"
DMIGRATE_URL="${DMIGRATE_URL:-https://gist.githubusercontent.com/mewisme/dd46a582b6131d6543f4336ac7087454/raw/dmigrate.sh}"

DRY_RUN=false

supports_color() {
  [ -t 1 ] && command -v tput >/dev/null 2>&1 && [ "$(tput colors 2>/dev/null || echo 0)" -ge 8 ]
}

if supports_color; then
  C_RESET="$(tput sgr0)"
  C_RED="$(tput setaf 1)"
  C_GREEN="$(tput setaf 2)"
  C_YELLOW="$(tput setaf 3)"
  C_BLUE="$(tput setaf 4)"
  C_BOLD="$(tput bold)"
else
  C_RESET=""
  C_RED=""
  C_GREEN=""
  C_YELLOW=""
  C_BLUE=""
  C_BOLD=""
fi

info() { printf '%s\n' "${C_BLUE}INFO${C_RESET}  $*"; }
ok() { printf '%s\n' "${C_GREEN}OK${C_RESET}    $*"; }
warn() { printf '%s\n' "${C_YELLOW}WARN${C_RESET}  $*"; }
fail() { printf '%s\n' "${C_RED}ERROR${C_RESET} $*" >&2; }

on_error() {
  local exit_code=$?
  fail "command failed at line ${1}: ${BASH_COMMAND}"
  exit "$exit_code"
}
trap 'on_error $LINENO' ERR

run() {
  if [ "$DRY_RUN" = true ]; then
    printf '[DRY] '
    printf '%q ' "$@"
    printf '\n'
  else
    "$@"
  fi
}

usage() {
  cat <<EOF
${C_BOLD}dmigrate installer${C_RESET}

USAGE
  curl -fsSL ${INSTALL_SCRIPT_URL} | bash
  curl -fsSL ${INSTALL_SCRIPT_URL} | bash -s -- [options]

OPTIONS
  --dry-run                   Print install steps without changing the system
  -h, --help                  Show this help

ENVIRONMENT
  DMIGRATE_URL                Download URL for dmigrate.sh
                              (default: ${DMIGRATE_URL})

EOF
}

need_cmd() {
  if ! command -v "$1" >/dev/null 2>&1; then
    fail "missing command: $1"
    exit 1
  fi
}

need_download_cmd() {
  if command -v curl >/dev/null 2>&1; then
    echo "curl"
    return 0
  fi
  if command -v wget >/dev/null 2>&1; then
    echo "wget"
    return 0
  fi
  fail "missing command: curl or wget"
  exit 1
}

fetch_url() {
  local url="$1"
  local dest="$2"
  local tool
  tool="$(need_download_cmd)"

  case "$tool" in
    curl) curl -fsSL "$url" -o "$dest" ;;
    wget) wget -qO "$dest" "$url" ;;
  esac
}

read_script_version() {
  local file="$1"
  grep -E '^VERSION=' "$file" | head -n 1 | cut -d= -f2- | tr -d '"' | tr -d "'"
}

validate_downloaded_script() {
  local file="$1"

  if [ ! -s "$file" ]; then
    fail "downloaded script is empty"
    return 1
  fi

  if ! head -n 1 "$file" | grep -q '^#!/usr/bin/env bash'; then
    fail "downloaded file is not a bash script"
    return 1
  fi

  if ! grep -q 'dmigrate' "$file"; then
    fail "downloaded file does not look like dmigrate"
    return 1
  fi

  if [ -z "$(read_script_version "$file")" ]; then
    fail "downloaded file is missing VERSION"
    return 1
  fi

  if ! tail -n 1 "$file" | tr -d '\r' | grep -Fxq 'main "$@"'; then
    fail "downloaded file has invalid ending (expected: main \"\$@\")"
    return 1
  fi

  if [ "$(tr -d '\r' < "$file" | grep -cFx 'main "$@"' || true)" -ne 1 ]; then
    fail "downloaded file must contain exactly one main entrypoint"
    return 1
  fi

  return 0
}

parse_args() {
  while [ $# -gt 0 ]; do
    case "$1" in
      --dry-run)
        DRY_RUN=true
        ;;
      -h|--help)
        usage
        exit 0
        ;;
      *)
        fail "unknown option: $1"
        usage >&2
        exit 1
        ;;
    esac
    shift
  done
}

main() {
  local tmp version

  parse_args "$@"

  need_cmd sudo
  need_cmd mktemp

  if [ -e "$INSTALL_TARGET" ]; then
    warn "overwriting existing install at $INSTALL_TARGET"
  fi

  tmp="$(mktemp)"
  trap "rm -f -- '${tmp}'" EXIT

  info "downloading dmigrate from $DMIGRATE_URL"
  if ! fetch_url "$DMIGRATE_URL" "$tmp"; then
    fail "failed to download dmigrate from $DMIGRATE_URL"
    exit 1
  fi

  if ! validate_downloaded_script "$tmp"; then
    exit 1
  fi

  version="$(read_script_version "$tmp")"
  info "installing dmigrate v${version} -> $INSTALL_TARGET"
  run sudo bash -c 'cat "$1" > "$2"' _ "$tmp" "$INSTALL_TARGET"
  run sudo chmod 755 "$INSTALL_TARGET"

  if [ "$DRY_RUN" = true ]; then
    ok "dry run complete"
  else
    if ! validate_downloaded_script "$INSTALL_TARGET"; then
      fail "install wrote an invalid script to $INSTALL_TARGET"
      exit 1
    fi
    ok "installed: $INSTALL_TARGET"
    echo "Run: dmigrate help"
  fi
}

main "$@"