#!/usr/bin/env bash
# Test: dirty files are preserved when cache disk is nearly full
#
# Uses a tiny loopback-mounted filesystem as the cache disk to simulate
# a cache-full scenario. Verifies that dirty files are not lost when
# the cache disk has no free space for eviction.
set -euo pipefail
SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
source "$SCRIPT_DIR/../harness/helpers.sh"
source "$SCRIPT_DIR/../harness/mock-nas.sh"

require_root
setup_test_env

# Set up a tiny 5 MB cache disk (loopback ext4)
setup_small_cache_disk 5

trap 'teardown_small_cache_disk; teardown_test_env' EXIT

# Start mock NAS
start_mock_nas

# Generate config with small cache limit and a very long write-back
# so dirty files remain dirty throughout the test
gen_config cache_max_size=4M write_back=300s

# Start warpgate and wait for readiness
start_warpgate
wait_for_mount
wait_for_rc_api

# Sever the network so write-back cannot complete
inject_network_down

# Write several small files through the mount to fill the cache disk.
# Each file is ~256 KB, writing enough to nearly fill the 5 MB disk.
for i in $(seq 1 8); do
    dd if=/dev/urandom bs=1K count=256 2>/dev/null | \
        dd of="$TEST_MOUNT/fill-${i}.dat" bs=1K 2>/dev/null
    sleep 0.5
done

# Allow VFS time to register all dirty writes
sleep 3

# Verify that dirty files exist and are tracked
dirty=$(get_dirty_count)
if [[ "$dirty" -lt 1 ]]; then
    echo "FAIL: expected dirty count > 0, got $dirty" >&2
    inject_network_up
    exit 1
fi

# Verify each previously written dirty file is still accessible
for i in $(seq 1 8); do
    if [[ ! -f "$TEST_MOUNT/fill-${i}.dat" ]]; then
        echo "FAIL: dirty file fill-${i}.dat no longer accessible" >&2
        inject_network_up
        exit 1
    fi
done

# Attempt a 9th write — cache disk should be full, so this should fail
# with ENOSPC or a write error.
write_failed=0
dd if=/dev/urandom bs=1K count=256 2>/dev/null | \
    dd of="$TEST_MOUNT/fill-9.dat" bs=1K 2>/dev/null || write_failed=1

if [[ "$write_failed" -eq 0 ]]; then
    echo "WARN: 9th write succeeded — cache disk may not be truly full" >&2
    echo "  (expected ENOSPC or write error when cache disk is exhausted)" >&2
fi

# Restore the network for clean teardown
inject_network_up

echo "PASS: $(basename "$0" .sh)"