#!/usr/bin/env bash
#
# Upload a repo/ tree -- signed APKs plus the signed index -- to an
# S3-compatible bucket.
#
#     AWS_ACCESS_KEY_ID=... AWS_SECRET_ACCESS_KEY=... \
#       bash publish.sh <repo-root>/repo <bucket> <endpoint-url> [<prefix>]
#
# Bucket, endpoint and prefix are all arguments, never baked in here: this
# repo does not know, and per fdroid-repo-ci#1 must never come to know, which
# bucket or host any consumer publishes to. Credentials come from the
# standard AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY/AWS_SESSION_TOKEN
# environment variables that `aws` itself reads -- nothing here parses or
# forwards them as arguments.
#
# Region is required by the `aws` CLI even against a non-AWS S3-compatible
# backend that ignores it; set AWS_DEFAULT_REGION if the endpoint cares,
# otherwise the placeholder below is never actually consulted.
#
# ## Ordering (fdroid-repo-ci#5)
#
# An F-Droid repo is a signed index plus the files it names. A partial
# upload can leave them disagreeing in two ways: the index lands first and
# names files that still 404 (breaks the repo for every client until the
# upload finishes or is rolled back), or the files land first and the index
# is not yet updated (harmless -- the new build is merely not visible yet).
# Only the first is dangerous, and `aws s3 sync` walking a tree in its own
# order gives no protection against it. So this script uploads in two
# passes, unconditionally: every non-index file first, the index itself
# last. The repo is therefore always internally consistent -- before a
# publish it still describes the old state, after it describes the new one,
# and an interruption anywhere in pass 1 simply leaves it describing the old
# state a little longer, never a mixture.
#
# "The index" here is index-v1.json(.asc), index-v2.json, entry.json and
# entry.jar -- fdroidserver's actual top-level index/entry file names,
# matched only at the top level of the tree (a nested path like
# diff/<ts>.json is not "the index" and travels with the ordinary files;
# it is only ever reached by a client that already has last publish's index
# and is willing to look for it).
#
# ## Credentials are verified before anything is uploaded (fdroid-repo-ci#5)
#
# Checking that AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY are merely *set* does
# not mean they are *usable* -- an unusable-but-present credential failing
# halfway through is exactly how a partial (and, per the ordering point
# above, potentially index-first) upload happens. So before pass 1 this
# script makes one real authenticated call (`head-bucket`) and aborts if it
# fails, rather than discovering that the credentials do not work partway
# through a sync.
#
# ## Refusing to overwrite an existing APK (fdroid-repo-ci#6)
#
# next-version-code.sh's clamp is monotonic against *observed* state, not
# monotonic by construction -- it does not close the race where two jobs
# start in the same minute, both read the same `published` value, both
# compute the same next versionCode, and both build and publish. The window
# is the whole build, not just the clock read, because the version code is
# baked into the APK before it exists. Nothing in this script can prevent
# that wasted build. What it CAN do -- and is required to do, fdroid-repo-ci#6
# -- is turn the collision from a silent, permanent wrong state (two
# different APKs claiming one versionCode, with clients pinned to whichever
# they happened to fetch first) into a loud failure of the second job, at
# the last moment when the information is finally reliable: immediately
# before that job would otherwise upload over the first job's APK. An
# F-Droid repo names an APK `<applicationId>_<versionCode>.apk`, so the
# collision this guards against is exactly a name collision -- every local
# *.apk file's destination key is checked with `head-object` before pass 1,
# and the whole publish aborts if any of them is already there. This runs
# for every *.apk regardless of whether it actually collides, because there
# is no cheaper way to know in advance which ones might.
#
# Note this also means retrying a publish that already got partway through
# uploading its own APKs (e.g. pass 1 died mid-sync from a network drop)
# will now itself be refused on retry, indistinguishable at the object level
# from a genuine concurrent collision. That is an accepted cost of the same
# trade: this check cannot tell "the same job resuming" from "a different
# job that computed the same versionCode" without hashing every object,
# which was judged not worth the added complexity here. Recovering from that
# case is a fresh publish with a new versionCode, or deleting the partial
# upload by hand.
#
# Uses `aws s3 sync`, not `cp --recursive`: re-publishing re-uploads only
# what changed. Does **not** pass `--delete` by default -- an F-Droid repo
# normally keeps every APK it has ever served (older index entries can still
# point at them), so silently pruning the remote on every publish is the
# wrong default. Pass `--delete` as an extra argument if a caller genuinely
# wants the remote pruned to match local; it is forwarded to *both* passes,
# which is safe because `aws s3 sync --delete` never deletes anything that
# was excluded by that pass's own --exclude/--include filters -- so the
# files-pass never touches an index object and the index-pass never touches
# a file object, regardless of --delete.
#
# `fdroid update` needs no network; this is the one script in this repo that
# does (fdroid-repo-ci#1), and is accordingly the one script whose happy path
# the test suite cannot exercise against a real bucket. `--dry-run` prints
# the exact two commands this script would run, in order -- including the
# `with-nixpkgs.sh` pin -- and exits without touching the network at all: no
# credential check, no APK-existence check, no sync. That is what the test
# suite asserts against for command construction and ordering. (A
# PATH-stubbed `aws` cannot do this job: `nix shell` puts the packages it was
# asked for at the *front* of PATH, ahead of anything already there, so a
# stub earlier on the caller's PATH would simply be shadowed by the real
# `aws` from awscli2.) The credential check, the APK-existence check and the
# two-pass ordering are each proven separately: a real invocation against a
# closed local port for "fails on the network, and fails during the
# credential check specifically, before any upload is attempted"; a tiny
# local HEAD-only HTTP stub for "an existing APK is refused, and only an
# existing APK", offline; and the opt-in live round trip against a real
# bucket for the actual upload path plus a real head-to-head APK collision.
#
# Pins awscli2 via with-nixpkgs.sh/nixpkgs-pin, next to this script.
set -euo pipefail

here=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)

if [ "$#" -lt 3 ]; then
  cat >&2 <<'USAGE'
usage: publish.sh [--dry-run] <local-repo-dir> <bucket> <endpoint-url> [<prefix>] [extra aws s3 sync args...]

Credentials: AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (and optionally
AWS_SESSION_TOKEN) must already be exported -- never passed as arguments.
USAGE
  exit 2
fi

dry_run=false
if [ "$1" = "--dry-run" ]; then
  dry_run=true
  shift
fi

local_dir=$1
bucket=$2
endpoint=$3
shift 3

prefix=""
if [ "$#" -gt 0 ] && [[ $1 != -* ]]; then
  prefix=$1
  shift
fi

extra_args=("$@")

[ -d "$local_dir" ] || { echo "publish.sh: no such directory: $local_dir" >&2; exit 2; }
: "${AWS_ACCESS_KEY_ID:?publish.sh: AWS_ACCESS_KEY_ID is not set}"
: "${AWS_SECRET_ACCESS_KEY:?publish.sh: AWS_SECRET_ACCESS_KEY is not set}"

dest="s3://$bucket"
if [ -n "$prefix" ]; then
  dest="$dest/${prefix#/}"
fi
region="${AWS_DEFAULT_REGION:-us-east-1}"

# awscli2 2.23+ attaches a checksum algorithm to every PutObject by default.
# Garage rejects it outright -- measured against a real bucket:
#
#     An error occurred (InvalidRequest) when calling the PutObject
#     operation: Bad request: invalid checksum algorithm
#
# with aws-cli/2.34.24. Every upload fails, and it reads as a permissions
# problem until you notice that reads succeed and that writes fail the same
# way against a bucket the same credentials demonstrably can write.
#
# Set here rather than documented, because a caller should not have to know
# about a client-side default to publish to the object store this script
# exists for -- and leaving it to the environment means it works on one
# machine and not another. `when_required` keeps checksums where the protocol
# actually needs them, so this is narrower than switching them off.
export AWS_REQUEST_CHECKSUM_CALCULATION="${AWS_REQUEST_CHECKSUM_CALCULATION:-when_required}"
export AWS_RESPONSE_CHECKSUM_VALIDATION="${AWS_RESPONSE_CHECKSUM_VALIDATION:-when_required}"

aws_base=(bash "$here/with-nixpkgs.sh" awscli2 aws --endpoint-url "$endpoint" --region "$region")

# Top-level index/entry file names only -- see the "Ordering" comment above
# for why a nested path such as diff/<ts>.json is deliberately not matched.
index_exclude_filters=(--exclude "index*" --exclude "entry.*")
index_only_filters=(--exclude "*" --include "index*" --include "entry.*")

cmd_files=("${aws_base[@]}" s3 sync "$local_dir" "$dest"
           "${index_exclude_filters[@]}" "${extra_args[@]}")
cmd_index=("${aws_base[@]}" s3 sync "$local_dir" "$dest"
           "${index_only_filters[@]}" "${extra_args[@]}")

if [ "$dry_run" = true ]; then
  printf '%q ' "${cmd_files[@]}"
  printf '\n'
  printf '%q ' "${cmd_index[@]}"
  printf '\n'
  exit 0
fi

echo "publish.sh: verifying credentials against $endpoint"
if ! verify_out=$("${aws_base[@]}" s3api head-bucket --bucket "$bucket" 2>&1); then
  echo "publish.sh: credentials rejected (or bucket unreachable) -- nothing was uploaded:" >&2
  echo "$verify_out" >&2
  exit 1
fi

# Refuse to overwrite an existing APK -- see the comment block above for why
# this exists and what it does and does not close. Every local *.apk is
# checked, regardless of nesting, since fdroidserver's binary-repo layout
# keeps them under repo/ directly but nothing here should assume that.
while IFS= read -r -d '' apk; do
  rel=${apk#"$local_dir"/}
  key="$rel"
  if [ -n "$prefix" ]; then
    key="${prefix#/}/$rel"
  fi
  if head_out=$("${aws_base[@]}" s3api head-object --bucket "$bucket" --key "$key" 2>&1); then
    echo "publish.sh: refusing to publish -- $key already exists in s3://$bucket (would overwrite an existing APK, fdroid-repo-ci#6)" >&2
    exit 1
  elif echo "$head_out" | grep -qi '404\|not found\|NoSuchKey'; then
    : # does not exist yet -- fine, this is the common case
  else
    echo "publish.sh: could not check whether $key already exists -- refusing to guess:" >&2
    echo "$head_out" >&2
    exit 1
  fi
done < <(find "$local_dir" -type f -name '*.apk' -print0)

# Test-only synchronization point: if set, run it after the APK-existence
# check and before pass 1, and again between the two passes. Lets the test
# suite observe/assert real bucket state at the one moment that actually
# matters for the ordering guarantee (fdroid-repo-ci#5) -- files present,
# index not yet -- without racing a real background upload from outside.
# Never set by a real caller; not part of the documented interface above.
run_test_hook() {
  local hook_var=$1
  local hook_value="${!hook_var:-}"
  [ -n "$hook_value" ] && eval "$hook_value"
  return 0
}

run_test_hook PUBLISH_SH_TEST_HOOK_BEFORE_UPLOAD

echo "publish.sh: pass 1/2: uploading files (index deferred) $local_dir -> $dest"
"${cmd_files[@]}"

run_test_hook PUBLISH_SH_TEST_HOOK_BETWEEN_PASSES

echo "publish.sh: pass 2/2: uploading the index $local_dir -> $dest"
"${cmd_index[@]}"

echo "publish.sh: done"