#!/usr/bin/env bash

set -eu -o pipefail

set -x

source common.sh

export NIX_CONFIG='build-users-group = '

# Creating testing directories

storeA="$TEST_ROOT/store-a"
storeBTop="$TEST_ROOT/store-b"
storeB="local-overlay?root=$TEST_ROOT/merged-store&lower-store=$storeA&upper-layer=$storeBTop"

mkdir -p "$TEST_ROOT"/{store-a,store-b,merged-store/nix/store,workdir}

# Mounting Overlay Store

# Init lower store with some stuff
nix-store --store "$storeA" --add dummy

# Build something in lower store
drvPath=$(nix-instantiate --store $storeA ./hermetic.nix --arg busybox "$busybox" --arg seed 1)
path=$(nix-store --store "$storeA" --realise $drvPath)

mount -t overlay overlay \
  -o lowerdir="$storeA/nix/store" \
  -o upperdir="$storeBTop" \
  -o workdir="$TEST_ROOT/workdir" \
  "$TEST_ROOT/merged-store/nix/store" \
  || skipTest "overlayfs is not supported"

cleanupOverlay () {
  umount "$TEST_ROOT/merged-store/nix/store"
  rm -r $TEST_ROOT/workdir
}
trap cleanupOverlay EXIT

toRealPath () {
  storeDir=$1; shift
  storePath=$1; shift
  echo $storeDir$(echo $storePath | sed "s^$NIX_STORE_DIR^^")
}

### Check status

# Checking for path in lower layer
stat $(toRealPath "$storeA/nix/store" "$path")

# Checking for path in upper layer (should fail)
expect 1 stat $(toRealPath "$storeBTop" "$path")

# Checking for path in overlay store matching lower layer
diff $(toRealPath "$storeA/nix/store" "$path") $(toRealPath "$TEST_ROOT/merged-store/nix/store" "$path")

# Verifying path in lower layer
nix-store --verify-path --store "$storeA" "$path"

# Verifying path in merged-store
nix-store --verify-path --store "$storeB" "$path"

[[ \
  $(nix-store --store $storeA --query --outputs $drvPath) \
  == \
  $(nix-store --store $storeB --query --outputs $drvPath) \
  ]]

hashPart=$(echo $path | sed "s^$NIX_STORE_DIR/^^" | sed 's/-.*//')

# Lower store can find from hash part
[[ $(nix store --store $storeA path-from-hash-part $hashPart) == $path ]]

# merged store can find from hash part
[[ $(nix store --store $storeB path-from-hash-part $hashPart) == $path ]]

### Do a redundant add

# upper layer should not have it
expect 1 stat $(toRealPath "$storeBTop/nix/store" "$path")

path=$(nix-store --store "$storeB" --add dummy)

# lower store should have it from before
stat $(toRealPath "$storeA/nix/store" "$path")

# upper layer should still not have it (no redundant copy)
expect 1 stat $(toRealPath "$storeB/nix/store" "$path")

### Do a build in overlay store

path=$(nix-build ./hermetic.nix --arg busybox $busybox --arg seed 2 --store "$storeB" --no-out-link)

# Checking for path in lower layer (should fail)
expect 1 stat $(toRealPath "$storeA/nix/store" "$path")

# Checking for path in upper layer
stat $(toRealPath "$storeBTop" "$path")

# Verifying path in overlay store
nix-store --verify-path --store "$storeB" "$path"