from __future__ import annotations
from typing import Dict, Generator, List, Optional, Tuple
import argparse
import asyncio
import contextlib
import json
import os
import subprocess
import sys
import tempfile

class CalledProcessError(Exception):
    process: asyncio.subprocess.Process

def eprint(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)

async def check_subprocess(*args, **kwargs):
    """
    Emulate check argument of subprocess.run function.
    """
    process = await asyncio.create_subprocess_exec(*args, **kwargs)
    returncode = await process.wait()

    if returncode != 0:
        error = CalledProcessError()
        error.process = process

        raise error

    return process

async def run_update_script(merge_lock: asyncio.Lock, temp_dir: Optional[Tuple[str, str]], package: Dict, keep_going: bool):
    worktree: Optional[str] = None

    if temp_dir is not None:
        worktree, _branch = temp_dir

    eprint(f" - {package['name']}: UPDATING ...")

    try:
        update_process = await check_subprocess(*package['updateScript'], stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.PIPE, cwd=worktree)
        update_info = await update_process.stdout.read()

        await merge_changes(merge_lock, package, update_info, temp_dir)
    except KeyboardInterrupt as e:
        eprint('Cancelling…')
        raise asyncio.exceptions.CancelledError()
    except CalledProcessError as e:
        eprint(f" - {package['name']}: ERROR")
        eprint()
        eprint(f"--- SHOWING ERROR LOG FOR {package['name']} ----------------------")
        eprint()
        stderr = await e.process.stderr.read()
        eprint(stderr.decode('utf-8'))
        with open(f"{package['pname']}.log", 'wb') as logfile:
            logfile.write(stderr)
        eprint()
        eprint(f"--- SHOWING ERROR LOG FOR {package['name']} ----------------------")

        if not keep_going:
            raise asyncio.exceptions.CancelledError()

@contextlib.contextmanager
def make_worktree() -> Generator[Tuple[str, str], None, None]:
    with tempfile.TemporaryDirectory() as wt:
        branch_name = f'update-{os.path.basename(wt)}'
        target_directory = f'{wt}/nixpkgs'

        subprocess.run(['git', 'worktree', 'add', '-b', branch_name, target_directory])
        yield (target_directory, branch_name)
        subprocess.run(['git', 'worktree', 'remove', '--force', target_directory])
        subprocess.run(['git', 'branch', '-D', branch_name])

async def commit_changes(merge_lock: asyncio.Lock, worktree: str, branch: str, update_info: str) -> None:
    changes = json.loads(update_info)
    for change in changes:
        # Git can only handle a single index operation at a time
        async with merge_lock:
            await check_subprocess('git', 'add', *change['files'], cwd=worktree)
            commit_message = '{attrPath}: {oldVersion} → {newVersion}'.format(**change)
            await check_subprocess('git', 'commit', '--quiet', '-m', commit_message, cwd=worktree)
            await check_subprocess('git', 'cherry-pick', branch)

async def merge_changes(merge_lock: asyncio.Lock, package: Dict, update_info: str, temp_dir: Optional[Tuple[str, str]]) -> None:
    if temp_dir is not None:
        worktree, branch = temp_dir
        await commit_changes(merge_lock, worktree, branch, update_info)
    eprint(f" - {package['name']}: DONE.")

async def updater(temp_dir: Optional[Tuple[str, str]], merge_lock: asyncio.Lock, packages_to_update: asyncio.Queue[Optional[Dict]], keep_going: bool, commit: bool):
    while True:
        package = await packages_to_update.get()
        if package is None:
            # A sentinel received, we are done.
            return

        if not ('commit' in package['supportedFeatures']):
            temp_dir = None

        await run_update_script(merge_lock, temp_dir, package, keep_going)

async def start_updates(max_workers: int, keep_going: bool, commit: bool, packages: List[Dict]):
    merge_lock = asyncio.Lock()
    packages_to_update: asyncio.Queue[Optional[Dict]] = asyncio.Queue()

    with contextlib.ExitStack() as stack:
        temp_dirs: List[Optional[Tuple[str, str]]] = []

        # Do not create more workers than there are packages.
        num_workers = min(max_workers, len(packages))

        # Set up temporary directories when using auto-commit.
        for i in range(num_workers):
            temp_dir = stack.enter_context(make_worktree()) if commit else None
            temp_dirs.append(temp_dir)

        # Fill up an update queue,
        for package in packages:
            await packages_to_update.put(package)

        # Add sentinels, one for each worker.
        # A workers will terminate when it gets sentinel from the queue.
        for i in range(num_workers):
            await packages_to_update.put(None)

        # Prepare updater workers for each temp_dir directory.
        # At most `num_workers` instances of `run_update_script` will be running at one time.
        updaters = asyncio.gather(*[updater(temp_dir, merge_lock, packages_to_update, keep_going, commit) for temp_dir in temp_dirs])

        try:
            # Start updater workers.
            await updaters
        except asyncio.exceptions.CancelledError as e:
            # When one worker is cancelled, cancel the others too.
            updaters.cancel()

def main(max_workers: int, keep_going: bool, commit: bool, packages_path: str) -> None:
    with open(packages_path) as f:
        packages = json.load(f)

    eprint()
    eprint('Going to be running update for following packages:')
    for package in packages:
        eprint(f" - {package['name']}")
    eprint()

    confirm = input('Press Enter key to continue...')
    if confirm == '':
        eprint()
        eprint('Running update for:')

        asyncio.run(start_updates(max_workers, keep_going, commit, packages))

        eprint()
        eprint('Packages updated!')
        sys.exit()
    else:
        eprint('Aborting!')
        sys.exit(130)

parser = argparse.ArgumentParser(description='Update packages')
parser.add_argument('--max-workers', '-j', dest='max_workers', type=int, help='Number of updates to run concurrently', nargs='?', default=4)
parser.add_argument('--keep-going', '-k', dest='keep_going', action='store_true', help='Do not stop after first failure')
parser.add_argument('--commit', '-c', dest='commit', action='store_true', help='Commit the changes')
parser.add_argument('packages', help='JSON file containing the list of package names and their update scripts')

if __name__ == '__main__':
    args = parser.parse_args()

    try:
        main(args.max_workers, args.keep_going, args.commit, args.packages)
    except KeyboardInterrupt as e:
        # Let’s cancel outside of the main loop too.
        sys.exit(130)