#!/usr/bin/env python3

import os
import sys
import tempfile
import time

# Test create + write + read (passthrough.io=rw)
(fd, filepath) = tempfile.mkstemp(dir=sys.argv[1])

test_data = b"passthrough io test data for create\n" * 100

# Write to newly created file
bytes_written = os.write(fd, test_data)
if bytes_written != len(test_data):
    print("create write failed: expected {} bytes, wrote {}".format(len(test_data), bytes_written))
    sys.exit(1)

# Seek and read back
os.lseek(fd, 0, os.SEEK_SET)
read_data = os.read(fd, len(test_data))
if read_data != test_data:
    print("create read failed: data mismatch")
    sys.exit(1)

os.close(fd)

# Test open existing file + write + read
fd = os.open(filepath, os.O_RDWR)

# Read existing data
os.lseek(fd, 0, os.SEEK_SET)
read_data = os.read(fd, len(test_data))
if read_data != test_data:
    print("open read failed: data mismatch")
    sys.exit(1)

# Write more data at end
os.lseek(fd, 0, os.SEEK_END)
more_data = b"additional passthrough data for open\n" * 50
bytes_written = os.write(fd, more_data)
if bytes_written != len(more_data):
    print("open write failed: expected {} bytes, wrote {}".format(len(more_data), bytes_written))
    sys.exit(1)

# Verify all data
os.lseek(fd, 0, os.SEEK_SET)
all_data = os.read(fd, len(test_data) + len(more_data))
if all_data != test_data + more_data:
    print("open final read failed: data mismatch")
    sys.exit(1)

# Test multiple opens of same file (single backing_id feature)
# When a file is already open with passthrough, subsequent opens
# must reuse the same backing_id rather than creating new ones
fd2 = os.open(filepath, os.O_RDWR)

# Read from second fd - should see same data
os.lseek(fd2, 0, os.SEEK_SET)
read_data2 = os.read(fd2, len(test_data) + len(more_data))
if read_data2 != test_data + more_data:
    print("second open read failed: data mismatch")
    os.close(fd)
    os.close(fd2)
    sys.exit(1)

# Write from second fd
os.lseek(fd2, 0, os.SEEK_END)
extra_data = b"data from second file descriptor\n" * 25
bytes_written = os.write(fd2, extra_data)
if bytes_written != len(extra_data):
    print("second open write failed: expected {} bytes, wrote {}".format(len(extra_data), bytes_written))
    os.close(fd)
    os.close(fd2)
    sys.exit(1)

# Verify write is visible from first fd (shared backing)
os.lseek(fd, 0, os.SEEK_SET)
combined_data = os.read(fd, len(test_data) + len(more_data) + len(extra_data))
expected_data = test_data + more_data + extra_data
if combined_data != expected_data:
    print("cross-fd read failed: data mismatch (writes from fd2 not visible on fd)")
    os.close(fd)
    os.close(fd2)
    sys.exit(1)

# Open a third fd while others are still open
fd3 = os.open(filepath, os.O_RDONLY)
os.lseek(fd3, 0, os.SEEK_SET)
read_data3 = os.read(fd3, len(expected_data))
if read_data3 != expected_data:
    print("third open read failed: data mismatch")
    os.close(fd)
    os.close(fd2)
    os.close(fd3)
    sys.exit(1)

os.close(fd3)
os.close(fd2)
os.close(fd)

# Cleanup
os.unlink(filepath)