# -*- coding: utf-8 -*-
"""`_podcast_stream_download` 的行为契约。

为什么：这是播客单集下载的**唯一落盘路径**（单集 worker 与整台打包的首集都走它），
却零测试覆盖。把 63 行 / 嵌套 10 层的实现拆成「拿名额 → 流式写 → 改名 → 校验」
四步后，需要行为级测试钉住可观察契约：返回字节数、半成品文件名、失败时是否清掉
已落地的坏文件、取消语义、进度消息写到哪。

断言只看「调用后世界里发生了什么」（文件系统 + 任务表），不引用私有函数名，
故可跨后续重构复用。
"""
import threading

import pytest

from core.state import DOWNLOAD_TASKS, DOWNLOAD_TASKS_LOCK
from music_downloader import DownloadCanceled, DownloadException
from services import podcast as podcast_svc


class _FakeResp:
    """`_stream_open` 的替身：可控状态码、Content-Length 与分块序列。

    注意不能用 list(chunks) 归一化——那会把传入的生成器**立即求值**，使「迭代中
    才触发的副作用」（如中途置取消位）提前到构造时刻，测出来的就不是想测的路径。
    """

    def __init__(self, chunks, status=200, content_length=None):
        self._chunks = chunks
        self.status = status
        self.headers = {} if content_length is None else {'Content-Length': str(content_length)}

    def __enter__(self):
        return self

    def __exit__(self, *exc):
        return False

    def iter_content(self, chunk_size=0):
        yield from self._chunks


class _CancelAfterFirstChunk:
    """迭代器：吐第一块后置取消位，再吐第二块。

    这样取消发生在**迭代过程中**（下载已开始、.part 已建立），与「开始前取消」
    是两条不同的路径。
    """

    def __init__(self, cancel):
        self._cancel = cancel
        self._n = 0

    def __iter__(self):
        return self

    def __next__(self):
        self._n += 1
        if self._n == 1:
            return b'x' * 10
        if self._n == 2:
            self._cancel.set()
            return b'y' * 10
        raise StopIteration


@pytest.fixture()
def fake_stream(monkeypatch):
    """替换 _stream_open；测试通过 holder['resp'] 指定本次响应。"""
    holder: dict = {}

    def _open(url, timeout=60):
        assert url == holder.get('url', url)
        return holder['resp']

    monkeypatch.setattr(podcast_svc, '_stream_open', _open)
    return holder


@pytest.fixture()
def task_table():
    """在全局任务表里放一条任务，测试结束清理（该表是跨模块共享的进程内状态）。"""
    tid = 'stream-test-task'

    def _put(**kw):
        task = {'id': tid, 'status': 'running', 'type': 'single', 'msg': ''}
        task.update(kw)
        with DOWNLOAD_TASKS_LOCK:
            DOWNLOAD_TASKS[tid] = task
        return task

    yield _put
    with DOWNLOAD_TASKS_LOCK:
        DOWNLOAD_TASKS.pop(tid, None)


# ============ 正常路径 ============


def test_writes_target_and_renames_part(tmp_path, fake_stream):
    """正常下载：返回实际字节数，落地 target，不残留 .part。"""
    fake_stream['resp'] = _FakeResp([b'a' * 600, b'b' * 400])
    target = tmp_path / 'ep.mp3'
    done = podcast_svc._podcast_stream_download('http://u', target, 1000, threading.Event())
    assert done == 1000
    assert target.read_bytes() == b'a' * 600 + b'b' * 400
    assert not target.with_name('ep.mp3.part').exists()


def test_empty_chunks_are_skipped(tmp_path, fake_stream):
    """空分块不计入字节数（上游偶发发空 chunk）。"""
    fake_stream['resp'] = _FakeResp([b'', b'x' * 50, b''])
    target = tmp_path / 'ep.mp3'
    assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event()) == 50


def test_content_length_used_when_total_unknown(tmp_path, fake_stream):
    """未传期望大小时用 Content-Length 兜底，并据此校验完整性。"""
    fake_stream['resp'] = _FakeResp([b'x' * 30], content_length=30)
    target = tmp_path / 'ep.mp3'
    assert podcast_svc._podcast_stream_download('http://u', target, 0, threading.Event()) == 30


# ============ 完整性校验 ============


def test_size_mismatch_removes_delivered_file(tmp_path, fake_stream):
    """字节数不符：删掉已落地的文件并报错（不交付截断的坏文件）。"""
    fake_stream['resp'] = _FakeResp([b'x' * 100])
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadException) as ei:
        podcast_svc._podcast_stream_download('http://u', target, 200, threading.Event())
    assert '下载不完整' in str(ei.value)
    assert not target.exists(), '坏文件必须被清掉'


def test_empty_download_raises_and_removes(tmp_path, fake_stream):
    """期望大小未知且一个字节都没拿到 → 报「下载内容为空」。"""
    fake_stream['resp'] = _FakeResp([])
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadException) as ei:
        podcast_svc._podcast_stream_download('http://u', target, 0, threading.Event())
    assert '下载内容为空' in str(ei.value)
    assert not target.exists()


def test_known_size_does_not_tolerate_partial(tmp_path, fake_stream):
    """已知期望大小时要求精确相等——95% 容差会放行截断的坏文件。"""
    fake_stream['resp'] = _FakeResp([b'x' * 95])
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadException):
        podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event())


# ============ 上游与取消 ============


def test_upstream_error_status_raises(tmp_path, fake_stream):
    fake_stream['resp'] = _FakeResp([], status=404)
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadException) as ei:
        podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event())
    assert '上游返回 404' in str(ei.value)
    assert not target.exists()


def test_cancel_before_first_chunk(tmp_path, fake_stream):
    """取消已置位：抛 DownloadCanceled，不发布 target。"""
    cancel = threading.Event()
    cancel.set()
    fake_stream['resp'] = _FakeResp([b'x' * 10])
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadCanceled):
        podcast_svc._podcast_stream_download('http://u', target, 10, cancel)
    assert not target.exists()


def test_cancel_midway_leaves_part_file(tmp_path, fake_stream):
    """下载中途取消：.part 残留（不删）——改名不发生，下次同名下载直接覆盖。"""
    cancel = threading.Event()
    fake_stream['resp'] = _FakeResp(_CancelAfterFirstChunk(cancel))
    target = tmp_path / 'ep.mp3'
    with pytest.raises(DownloadCanceled):
        podcast_svc._podcast_stream_download('http://u', target, 20, cancel)
    assert not target.exists()
    assert target.with_name('ep.mp3.part').exists(), '既有行为：取消时 .part 留存'


# ============ 进度消息 ============


def test_progress_written_for_running_single_task(tmp_path, fake_stream, task_table):
    """running 的单集任务：写 msg，并按字节级口径写 live_percent。

    单块即完成 → 百分比被 min(99, ...) 封在 99（进度条不预支 100%，收尾靠终态）。
    """
    task = task_table()
    fake_stream['resp'] = _FakeResp([b'x' * 100])
    target = tmp_path / 'ep.mp3'
    podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event(),
                                         task_id=task['id'], progress_label='下载中')
    assert '下载中' in task['msg'] and '99%' in task['msg']
    assert task['live_percent'] == 99.0


def test_progress_not_written_for_finished_task(tmp_path, fake_stream, task_table):
    """已终态的任务不再被写进度（避免覆盖终态消息），但下载照常完成。"""
    task = task_table(status='done', msg='原消息')
    fake_stream['resp'] = _FakeResp([b'x' * 50])
    target = tmp_path / 'ep.mp3'
    assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event(),
                                                task_id=task['id']) == 50
    assert task['msg'] == '原消息'


def test_progress_skipped_without_task_id(tmp_path, fake_stream):
    """task_id 为空时只下载不写任务表（不得因缺 id 而报错）。"""
    fake_stream['resp'] = _FakeResp([b'x' * 50])
    target = tmp_path / 'ep.mp3'
    assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event()) == 50