#!/bin/python3
"""
Parallel rsync launcher.

Requires rsync on PATH (e.g. via MSYS/Cygwin on Windows).
Runs multiple rsync invocations in parallel (one per file/entry).
"""

import argparse
import subprocess
import sys
from concurrent.futures import ThreadPoolExecutor, as_completed
from pathlib import Path
from typing import List

#DEFAULT_RSYNC_ARGS = ["-av", "--partial", "--compress", "--info=progress2"]
DEFAULT_RSYNC_ARGS = ["-avP", "--partial"]


def build_file_list(src: str) -> List[Path]:
    p = Path(src)
    if p.is_dir():
        # sync each top-level entry separately (files and immediate subdirs)
        return [x for x in p.iterdir()]
    # allow glob patterns
    if any(ch in src for ch in ["*", "?"]):
        return list(Path(".").glob(src))
    # single file
    return [p]


def run_rsync(item: Path, dest: str, rsync_args: List[str], dry_run: bool) -> (Path, int, str, str):
    cmd = ["rsync", *rsync_args]
    if dry_run:
        cmd.append("--dry-run")
    # preserve relative path by sending the item name, not its parent
    cmd += [str(item), dest]
    try:
        proc = subprocess.run(cmd, capture_output=True, text=True)
        return item, proc.returncode, proc.stdout, proc.stderr
    except FileNotFoundError:
        return item, 127, "", "rsync not found on PATH"


def main():
    ap = argparse.ArgumentParser(description="Transfer files using rsync in parallel.")
    ap.add_argument("src", help="Source file, directory or glob pattern")
    ap.add_argument("dest", help="Rsync destination (local path or user@host:/path)")
    ap.add_argument("-w", "--workers", type=int, default=4, help="Parallel rsync workers")
    ap.add_argument("-r", "--rsync-args", default=" ".join(DEFAULT_RSYNC_ARGS),
                    help="Additional rsync args (quoted). Default: -a --partial --compress --progress")
    ap.add_argument("--dry-run", action="store_true", help="Don't transfer, just show what would happen")
    args = ap.parse_args()

    items = build_file_list(args.src)
    if not items:
        print("No files found for:", args.src, file=sys.stderr)
        sys.exit(2)

    rsync_args = args.rsync_args.split()
    results = []
    print(f"Starting {len(items)} rsync tasks with {args.workers} workers...")

    with ThreadPoolExecutor(max_workers=args.workers) as ex:
        futures = {ex.submit(run_rsync, item, args.dest, rsync_args, args.dry_run): item for item in items}
        for fut in as_completed(futures):
            item, code, out, err = fut.result()
            results.append((item, code, out, err))
            status = "OK" if code == 0 else f"ERR({code})"
            print(f"[{status}] {item}")

    # summary
    failed = [r for r in results if r[1] != 0]
    print(f"\nCompleted: {len(results)} tasks, {len(failed)} failed.")
    if failed:
        print("Failures detail:")
        for item, code, out, err in failed:
            print(f"--- {item} (exit {code}) ---")
            if out:
                print(out.strip())
            if err:
                print(err.strip())

    sys.exit(1 if failed else 0)


if __name__ == "__main__":
    main()