import asyncio
import datetime
import random
from pathlib import Path, PurePath
from typing import Optional

from ..conductor import TerminalConductor
from ..config import Config
from ..crawler import Crawler, CrawlerSection, anoncritical


class LocalCrawlerSection(CrawlerSection):
    def target(self) -> Path:
        value = self.s.get("target")
        if value is None:
            self.missing_value("target")
        return Path(value).expanduser()

    def crawl_delay(self) -> float:
        value = self.s.getfloat("crawl_delay", fallback=0.0)
        if value < 0:
            self.invalid_value("crawl_delay", value,
                               "Must not be negative")
        return value

    def download_delay(self) -> float:
        value = self.s.getfloat("download_delay", fallback=0.0)
        if value < 0:
            self.invalid_value("download_delay", value,
                               "Must not be negative")
        return value

    def download_speed(self) -> Optional[int]:
        value = self.s.getint("download_speed")
        if value is not None and value <= 0:
            self.invalid_value("download_speed", value,
                               "Must be greater than 0")
        return value


class LocalCrawler(Crawler):
    def __init__(
            self,
            name: str,
            section: LocalCrawlerSection,
            config: Config,
            conductor: TerminalConductor,
    ):
        super().__init__(name, section, config, conductor)

        self._target = config.working_dir / section.target()
        self._crawl_delay = section.crawl_delay()
        self._download_delay = section.download_delay()
        self._download_speed = section.download_speed()

        if self._download_speed:
            self._block_size = self._download_speed // 10
        else:
            self._block_size = 1024**2  # 1 MiB

    async def crawl(self) -> None:
        await self._crawl_path(self._target, PurePath())
        if self.error_free:
            await self.cleanup()

    @anoncritical
    async def _crawl_path(self, path: Path, pure: PurePath) -> None:
        if path.is_dir():
            await self._crawl_dir(path, pure)
        elif path.is_file():
            await self._crawl_file(path, pure)

    async def _crawl_dir(self, path: Path, pure: PurePath) -> None:
        tasks = []

        async with self.crawl_bar(pure):
            await asyncio.sleep(random.uniform(
                0.5 * self._crawl_delay,
                self._crawl_delay,
            ))

            for child in path.iterdir():
                pure_child = pure / child.name
                if self.should_crawl(child):
                    tasks.append(self._crawl_path(child, pure_child))

        await asyncio.gather(*tasks)

    async def _crawl_file(self, path: Path, pure: PurePath) -> None:
        stat = path.stat()
        mtime = datetime.datetime.fromtimestamp(stat.st_mtime)
        dl = await self.download(pure, mtime=mtime)
        if not dl:
            return

        async with self.download_bar(path) as bar:
            await asyncio.sleep(random.uniform(
                0.5 * self._download_delay,
                self._download_delay,
            ))

            bar.set_total(stat.st_size)

            async with dl as sink:
                with open(path, "rb") as f:
                    while True:
                        data = f.read(self._block_size)
                        if len(data) == 0:
                            break

                        sink.file.write(data)
                        bar.advance(len(data))

                        if self._download_speed:
                            delay = self._block_size / self._download_speed
                            delay = random.uniform(0.8 * delay, 1.2 * delay)
                            await asyncio.sleep(delay)

                    sink.done()