#!/bin/sh
# Install Prismix on a Raspberry Pi running Raspberry Pi OS (64-bit), or bring it up to date, and
# run it in auto mode from boot (docs/installer.md). Run on the Pi as root:
#
#   curl https://cli.prismix.cymant.com | sudo sh
#
# Settings, as environment variables (after sudo): PRISMIX_RELEASES, where the releases are (the
# folder scripts/release.sh writes, served over HTTP(S); https://cli.prismix.cymant.com if unset, until cli.getprismix.com);
# PRISMIX_INTERFACE, the players' interface (eth0 if unset); PRISMIX_LOG, the log level (info if
# unset). PRISMIX_ROOT puts every installed file under another folder, for scripts/test-install.sh
# only.
#
# The script is only definitions until its last line, so a download cut off anywhere runs nothing.
# It reads nothing from its input, which is the script itself.

set -eu

fail() {
  echo "$*" >&2
  exit 1
}

# One URL to a file, with curl or else wget.
fetch() {
  if command -v curl >/dev/null 2>&1; then
    curl -fsSL -o "$2" "$1" </dev/null
  elif command -v wget >/dev/null 2>&1; then
    wget -q -O "$2" "$1" </dev/null
  else
    fail "Neither curl nor wget is installed: install one with apt-get install curl."
  fi
}

check_machine() {
  [ "$(uname -m)" = aarch64 ] ||
    fail "Prismix runs on 64-bit Raspberry Pi OS; this is $(uname -m)."
  [ "$(id -u)" = 0 ] ||
    fail "The installer must run as root: put sudo before sh."
  command -v systemctl >/dev/null 2>&1 ||
    fail "Prismix needs systemd, which this system does not have."
  # Raspberry Pi OS before Trixie (Debian 13) has no link-local fallback for the players' Ethernet
  # (set_ethernet), so it is refused. The founder, 2026-10-31: "old OS, just, yeah, refuse it."
  if [ -r "$root/etc/os-release" ]; then
    system=$(sed -n 's/^ID=//p' "$root/etc/os-release" | tr -d '"')
    version=$(sed -n 's/^VERSION_ID=//p' "$root/etc/os-release" | tr -d '"')
    codename=$(sed -n 's/^VERSION_CODENAME=//p' "$root/etc/os-release" | tr -d '"')
    case "$system" in
      debian | raspbian)
        [ "${version:-0}" -ge 13 ] 2>/dev/null ||
          fail "Prismix needs Raspberry Pi OS Trixie or later; this Pi runs ${codename:-an older one}. Write Raspberry Pi OS Lite (64-bit) to its card with Raspberry Pi Imager, then run this again."
        ;;
    esac
  fi
}

# The release the pointer names, downloaded and checked, unpacked into $work/release.
download() {
  fetch "$releases/latest" "$work/latest" ||
    fail "Could not download the release pointer from $releases/latest."
  commit=$(sed -n 's/^commit //p' "$work/latest")
  archive=$(sed -n 's/^archive //p' "$work/latest")
  sha256=$(sed -n 's/^sha256 //p' "$work/latest")
  case "$archive" in
    '' | *[!A-Za-z0-9._-]*) fail "The release pointer at $releases/latest is not one Prismix wrote." ;;
  esac
  [ -n "$commit" ] && [ -n "$sha256" ] ||
    fail "The release pointer at $releases/latest is not one Prismix wrote."
  echo "Downloading Prismix $commit."
  fetch "$releases/$archive" "$work/$archive" ||
    fail "Could not download $releases/$archive."
  [ "$(sha256sum "$work/$archive" | cut -d ' ' -f 1)" = "$sha256" ] ||
    fail "The download of Prismix $commit is damaged (its SHA-256 does not match): nothing was changed."
  mkdir "$work/release"
  tar -xzf "$work/$archive" -C "$work/release" prismix record-network.sh 2>/dev/null ||
    fail "The archive of Prismix $commit is damaged: nothing was changed."
}

# tcpdump records the players' network; without it Prismix runs and the recorder waits.
install_tcpdump() {
  command -v tcpdump >/dev/null 2>&1 && return 0
  echo "Installing tcpdump, to record the players' network."
  DEBIAN_FRONTEND=noninteractive apt-get install -y tcpdump </dev/null >/dev/null 2>&1 ||
    echo "Recording the players' network waits for tcpdump (no internet for apt?)."
}

# Each file is copied next to its place, the one there kept as .previous, then renamed in: a link
# at the place is replaced, never written through.
place() {
  install -D -m 755 "$1" "$2.new"
  if [ -e "$2" ] || [ -L "$2" ]; then
    mv -f "$2" "$2.previous"
  else
    rm -f "$2.previous"
  fi
  mv -f "$2.new" "$2"
}

restore() {
  if [ -e "$1.previous" ] || [ -L "$1.previous" ]; then
    mv -f "$1.previous" "$1"
  fi
}

# A build that does not stay running is undone: the previous one runs again.
check_running() {
  sleep 5
  systemctl is-active --quiet prismix </dev/null && return 0
  if [ ! -e "$binary.previous" ] && [ ! -L "$binary.previous" ]; then
    fail "The new Prismix did not start (journalctl -u prismix shows why)."
  fi
  restore "$binary"
  restore "$recorder"
  systemctl restart prismix prismix-record </dev/null || true
  fail "The new Prismix did not start; the previous one is running again (journalctl -u prismix shows why)."
}

# The services, as scripts/pi.sh autostart on and deploy write them.
write_units() {
  units=$root/etc/systemd/system
  mkdir -p "$units"
  printf '%s\n' \
    '[Unit]' \
    'Description=Prismix auto mode: serves the library on any USB drive plugged in' \
    'After=network.target' \
    '' \
    '[Service]' \
    "ExecStart=/usr/local/bin/prismix auto --interface $interface" \
    "Environment=PRISMIX_LOG=$log" \
    'Restart=always' \
    'RestartSec=2' \
    '' \
    '[Install]' \
    'WantedBy=multi-user.target' >"$units/prismix.service"
  printf '%s\n' \
    '[Unit]' \
    "Description=Prismix: record the players' network when enabled" \
    'After=network.target' \
    '' \
    '[Service]' \
    "ExecStart=/usr/local/lib/prismix/record-network.sh $interface" \
    'Restart=always' \
    'RestartSec=5' \
    '' \
    '[Install]' \
    'WantedBy=multi-user.target' >"$units/prismix-record.service"
}

# The players' interface takes an address from a router if there is one, or else picks its own
# link-local one (169.254.x.x), as the players do: so Prismix works on a switch with no router, the
# usual DJ booth, and on a network with one. The founder, 2026-10-31: "Yeah, fallback sounds good."
# Fallback needs NetworkManager 1.52 (Raspberry Pi OS Trixie). It keeps asking for a router: with
# NetworkManager's 45-second limit, the connection fails each time no router answers, and after
# four failures it gives up and drops the link-local address too.
set_ethernet() {
  if ! command -v nmcli >/dev/null 2>&1; then
    echo "NetworkManager is not installed: $interface is left as it is."
    return 0
  fi
  name=$(nmcli -t -f NAME,DEVICE connection show </dev/null | sed -n "s/:$interface\$//p" | head -n 1)
  if [ -z "$name" ]; then
    name=$(nmcli -t -f NAME,TYPE connection show </dev/null | sed -n 's/:802-3-ethernet$//p' | head -n 1)
  fi
  if [ -z "$name" ]; then
    echo "$interface has no network connection to set: it is left as it is."
    return 0
  fi
  before=$(nmcli -g ipv4.method,ipv4.link-local,ipv4.dhcp-timeout connection show "$name" </dev/null)
  case "$before" in
    manual*)
      echo "$interface keeps the address set for it by hand."
      return 0
      ;;
  esac
  if ! nmcli connection modify "$name" ipv4.method auto ipv4.link-local fallback \
    ipv4.dhcp-timeout infinity </dev/null >/dev/null 2>&1; then
    echo "This Raspberry Pi OS is older than Trixie: $interface is left as it is, so players on a switch with no router may not find Prismix."
    return 0
  fi
  [ "$(nmcli -g ipv4.method,ipv4.link-local,ipv4.dhcp-timeout connection show "$name" </dev/null)" != "$before" ] || return 0
  echo "$interface now takes an address from a router if there is one, or picks its own (169.254.x.x) as players do."
  nmcli --wait 0 connection up "$name" </dev/null >/dev/null 2>&1 ||
    echo "$interface takes its address when its cable is in."
}

start() {
  systemctl daemon-reload </dev/null
  systemctl enable --quiet prismix prismix-record </dev/null
  systemctl restart prismix prismix-record </dev/null
}

main() {
  releases=${PRISMIX_RELEASES:-https://cli.prismix.cymant.com}
  interface=${PRISMIX_INTERFACE:-eth0}
  log=${PRISMIX_LOG:-info}
  root=${PRISMIX_ROOT:-}
  check_machine
  # A connection to the Pi through the players' interface may drop when it is set: the install
  # goes on without it.
  trap '' HUP

  work=$(mktemp -d)
  trap 'rm -rf "$work"' EXIT
  download
  install_tcpdump

  binary=$root/usr/local/bin/prismix
  recorder=$root/usr/local/lib/prismix/record-network.sh
  place "$work/release/prismix" "$binary"
  place "$work/release/record-network.sh" "$recorder"
  write_units
  set_ethernet
  start
  check_running
  echo "Prismix $commit is installed and running."
}

main "$@"