#!/bin/bash
# Perplexity ships its desktop app from its own Debian repository. The
# per-architecture package index carries the filename and SHA256 of every deb,
# so an update costs two small HTTP requests instead of a 175 MB download. The
# index's Version field drops the build number the pool filename carries, and
# upstream rebuilds under the same marketing version, so the version of record
# here is the full string embedded in the filename.
set -euo pipefail

BASE_URL="https://packages.perplexity.ai/deb"
declare -A DEB_ARCHES=([x86_64]=amd64 [aarch64]=arm64)

# Print "<version> <sha256>" for the newest stanza in a Packages index, version
# meaning the full string from the pool filename. Newest is vercmp's opinion,
# which is the one bin/sync-upstream and pacman both use; sort -V disagrees
# with it over versions like 1.0a.
newest_release() {
  local index="$1"
  local debarch="$2"
  local filename sha256 version best_version="" best_sha256=""
  local prefix="pool/main/p/perplexity/perplexity_"
  local suffix="_${debarch}.deb"

  while read -r filename sha256; do
    # The PKGBUILD reconstructs the pool URL from pkgver alone, so a stanza
    # naming anything else -- a rename, or a new pool layout -- has to stop
    # the sync rather than pin a checksum to a URL nobody will fetch.
    if [[ "$filename" != "${prefix}"*"${suffix}" ]]; then
      echo "Unexpected pool filename in the upstream index: $filename" >&2
      return 1
    fi
    version="${filename#"$prefix"}"
    version="${version%"$suffix"}"

    if [[ -z "$best_version" ]] || [[ "$(vercmp "$version" "$best_version")" -gt 0 ]]; then
      best_version="$version"
      best_sha256="$sha256"
    fi
  done < <(awk '
    { sub(/\r$/, "") }
    /^Filename:/ { filename = $2 }
    /^SHA256:/   { sha256 = $2 }
    /^$/         { if (filename && sha256) print filename, sha256; filename = sha256 = "" }
    END          { if (filename && sha256) print filename, sha256 }
  ' <<<"$index")

  [[ -n "$best_version" ]] || return 1
  echo "$best_version $best_sha256"
}

versions=()
declare -A checksums=()

for arch in "${!DEB_ARCHES[@]}"; do
  index=$(curl -fsSL "$BASE_URL/dists/stable/main/binary-${DEB_ARCHES[$arch]}/Packages")

  read -r version sha256 <<<"$(newest_release "$index" "${DEB_ARCHES[$arch]}")"
  if [[ -z "${version:-}" || -z "${sha256:-}" ]]; then
    echo "No usable release found for $arch in the upstream package index" >&2
    exit 1
  fi

  versions+=("$version")
  checksums[$arch]="$sha256"
done

# A release lands one architecture at a time, and a single pkgver has to cover
# both -- including the build number, since that is what the download URLs are
# built from. Report no update until they agree; the next run picks it up.
for version in "${versions[@]}"; do
  if [[ "$version" != "${versions[0]}" ]]; then
    echo "Upstream architectures are mid-release (${versions[*]}); skipping" >&2
    echo '{}'
    exit 0
  fi
done

jq -n \
  --arg pkgver "${versions[0]}" \
  --arg x86_64 "${checksums[x86_64]}" \
  --arg aarch64 "${checksums[aarch64]}" \
  '{pkgver: $pkgver, sha256sums: {x86_64: [$x86_64], aarch64: [$aarch64]}}'