# ============================================================
# File: scraper/tasks/download_tasks.py
# Purpose:
#   Download chapter HTML into payload["html"].
#   Updated for book_idx unified ID model.
# ============================================================

from celery_app import celery_app
from scraper.utils.utils import get_save_path
from scraper.abort import abort_requested, chapter_started, mark_chapter_started

# Unified repository façade
from db.repository import (
    set_status,
    inc_download_done,
    inc_download_skipped,
)

from logbus.publisher import log
from scraper.ui_log import push_ui
from scraper.logger_decorators import logcall

import requests
import redis
import os
import time
from datetime import datetime


print(">>> [IMPORT] download_tasks.py loaded")


# -----------------------------------------------------------
# TIMESTAMPED LOG WRAPPER
# -----------------------------------------------------------
def log_msg(book_idx: str, message: str):
    ts = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    full = f"{ts} [{book_idx}] {message}"
    log(full)
    push_ui(full)


# -----------------------------------------------------------
# ENV CONFIG
# -----------------------------------------------------------
MAX_RETRIES = int(os.getenv("DOWNLOAD_MAX_RETRIES", "7"))
BASE_DELAY = int(os.getenv("DOWNLOAD_BASE_DELAY", "2"))
BACKOFF = int(os.getenv("DOWNLOAD_BACKOFF_MULTIPLIER", "2"))
DELAY_429 = int(os.getenv("DOWNLOAD_429_DELAY", "10"))

MAX_CONCURRENCY = int(os.getenv("DOWNLOAD_MAX_GLOBAL_CONCURRENCY", "1"))
GLOBAL_DELAY = int(os.getenv("DOWNLOAD_GLOBAL_MIN_DELAY", "1"))

REDIS_URL = os.getenv("REDIS_BROKER", "redis://redis:6379/0")
redis_client = redis.Redis.from_url(REDIS_URL)

SEM_KEY = "download:active"
DELAY_KEY = "download:delay_lock"


# -----------------------------------------------------------
# DELAY + CONCURRENCY HELPERS
# -----------------------------------------------------------
def wait_for_global_delay():
    if GLOBAL_DELAY <= 0:
        return
    while redis_client.exists(DELAY_KEY):
        time.sleep(0.1)


def set_global_delay():
    if GLOBAL_DELAY <= 0:
        return
    redis_client.set(DELAY_KEY, "1", nx=True, ex=GLOBAL_DELAY)


def acquire_global_slot(max_slots: int, retry_delay: float = 0.5):
    while True:
        current = redis_client.incr(SEM_KEY)
        if current <= max_slots:
            return
        redis_client.decr(SEM_KEY)
        time.sleep(retry_delay)


def release_global_slot():
    redis_client.decr(SEM_KEY)


# ============================================================
# CELERY TASK — Payload v3 (book_idx model)
# ============================================================
@celery_app.task(bind=True, queue="download", ignore_result=False)
@logcall
def download_chapter(self, payload: dict):
    """
    Payload format:

    {
        "book_idx": str,
        "chapter": {
            "num": int,
            "title": str,
            "url": str,
            "volume_path": str
        },
        "book_meta": dict,

        # fields filled during pipeline:
        "html": None | str,
        "parsed": None | str,
        "skipped": bool,
        "path": None | str
    }
    """

    if not payload:
        raise ValueError("download_chapter received empty payload")

    book_idx = payload["book_idx"]
    chapter = payload["chapter"]
    book_meta = payload.get("book_meta") or {}

    chapter_num = chapter["num"]
    chapter_url = chapter["url"]
    chapter_title = chapter.get("title") or f"Chapter {chapter_num}"
    volume_path = chapter["volume_path"]

    # -----------------------------------------------------------
    # STATUS UPDATE (book is now in 'downloading')
    # -----------------------------------------------------------
    set_status(book_idx, "downloading")

    # -----------------------------------------------------------
    # ABORT CHECK (skip if not yet started)
    # -----------------------------------------------------------
    if abort_requested(book_idx) and not chapter_started(book_idx, chapter_num):
        log_msg(book_idx, f"[ABORT] Skip chapter {chapter_num}")

        inc_download_skipped(book_idx)

        payload["html"] = None
        payload["skipped"] = True
        payload["path"] = None
        return payload

    mark_chapter_started(book_idx, chapter_num)

    # -----------------------------------------------------------
    # SKIP IF FILE ALREADY EXISTS
    # -----------------------------------------------------------
    save_path = get_save_path(chapter_num, volume_path)

    if os.path.exists(save_path):
        log_msg(book_idx, f"[DL] SKIP {chapter_num} → {save_path}")
        inc_download_skipped(book_idx)

        payload["html"] = None
        payload["skipped"] = True
        payload["path"] = save_path
        return payload

    # -----------------------------------------------------------
    # GLOBAL DELAY + CONCURRENCY
    # -----------------------------------------------------------
    if GLOBAL_DELAY > 0:
        time.sleep(GLOBAL_DELAY)

    wait_for_global_delay()
    acquire_global_slot(MAX_CONCURRENCY)

    # -----------------------------------------------------------
    # HTTP DOWNLOAD
    # -----------------------------------------------------------
    try:
        log_msg(book_idx, f"[DL] Downloading {chapter_num} ({chapter_title})")

        resp = requests.get(
            chapter_url,
            headers={"User-Agent": "Mozilla/5.0"},
            timeout=20,
        )
        resp.raise_for_status()

        resp.encoding = resp.apparent_encoding or "gb2312"
        html = resp.text

        log_msg(book_idx, f"[DL] OK {chapter_num}: {len(html)} bytes")

        payload["html"] = html
        payload["skipped"] = False
        payload["path"] = save_path
        return payload

    except Exception as exc:
        attempt = self.request.retries
        delay = BASE_DELAY * (BACKOFF**attempt)

        # Handle 429
        if getattr(getattr(exc, "response", None), "status_code", None) == 429:
            log_msg(book_idx, f"[DL] 429 → WAIT {DELAY_429}s")
            time.sleep(DELAY_429)
            set_global_delay()
            raise self.retry(exc=exc, countdown=0, max_retries=MAX_RETRIES)

        # General retry with backoff
        log_msg(book_idx, f"[DL] ERROR {chapter_num}: {exc} → retry {delay}s")
        raise self.retry(exc=exc, countdown=delay, max_retries=MAX_RETRIES)

    finally:
        set_global_delay()
        release_global_slot()