#!/usr/bin/env python3
"""
Douban Collection Full Export via Frodo API (Mobile App Backend)

Exports all book/movie/music/game collections to CSV files.
No login or cookies required — uses HMAC-SHA1 signature auth.

The API key and HMAC secret are Douban's mobile app credentials, extracted from
the public APK. They are the same for all users and do not identify you. No
personal credentials are used or stored. Data is fetched only from frodo.douban.com.

Usage:
    DOUBAN_USER=<user_id> python3 douban-frodo-export.py
    DOUBAN_USER=<user_id> DOUBAN_OUTPUT_DIR=/custom/path python3 douban-frodo-export.py

Environment:
    DOUBAN_USER (required): Douban user ID from profile URL
    DOUBAN_OUTPUT_DIR (optional): Override output directory
"""

import hmac
import hashlib
import base64
import csv
import json
import os
import platform
import re
import socket
import sys
import time
import urllib.parse
import urllib.request
import urllib.error

# --- Frodo API Auth ---
# Public credentials from the Douban Android APK, shared by all app users.
API_KEY = '0dad551ec0f84ed02907ff5c42e8ec70'
HMAC_SECRET = b'bf7dddc7c9cfe6f7'
BASE_URL = 'https://frodo.douban.com'
USER_AGENT = (
    'api-client/1 com.douban.frodo/7.22.0.beta9(231) Android/23 '
    'product/Mate40 vendor/HUAWEI model/Mate40 brand/HUAWEI '
    'rom/android network/wifi platform/AndroidPad'
)

# --- Rate Limiting ---
# 1.5s between pages, 2s between categories. Tested with 1200+ items.
PAGE_DELAY = 1.5
CATEGORY_DELAY = 2.0
ITEMS_PER_PAGE = 50
MAX_PAGES_SAFETY = 500  # Guard against infinite pagination loops

# --- Category Definitions ---
CATEGORIES = [
    ('book',  'done',  '读过', '书.csv'),
    ('book',  'doing', '在读', '书.csv'),
    ('book',  'mark',  '想读', '书.csv'),
    ('movie', 'done',  '看过', '影视.csv'),
    ('movie', 'doing', '在看', '影视.csv'),
    ('movie', 'mark',  '想看', '影视.csv'),
    ('music', 'done',  '听过', '音乐.csv'),
    ('music', 'doing', '在听', '音乐.csv'),
    ('music', 'mark',  '想听', '音乐.csv'),
    ('game',  'done',  '玩过', '游戏.csv'),
    ('game',  'doing', '在玩', '游戏.csv'),
    ('game',  'mark',  '想玩', '游戏.csv'),
]

URL_PREFIX = {
    'book':  'https://book.douban.com/subject/',
    'movie': 'https://movie.douban.com/subject/',
    'music': 'https://music.douban.com/subject/',
    'game':  'https://www.douban.com/game/',
}

CSV_FIELDS = ['title', 'url', 'date', 'rating', 'status', 'comment']


def get_download_dir():
    """Get the platform-appropriate Downloads directory."""
    system = platform.system()
    if system == 'Darwin':
        return os.path.expanduser('~/Downloads')
    elif system == 'Windows':
        return os.path.join(os.environ.get('USERPROFILE', os.path.expanduser('~')), 'Downloads')
    else:
        return os.path.expanduser('~/Downloads')


def get_output_dir(user_id):
    """Determine output directory from env or platform default."""
    base = os.environ.get('DOUBAN_OUTPUT_DIR')
    if not base:
        base = os.path.join(get_download_dir(), 'douban-sync')
    return os.path.join(base, user_id)


def compute_signature(url_path, timestamp):
    """Compute Frodo API HMAC-SHA1 signature.

    Signs: METHOD & url_encoded_path & timestamp (path only, no query params).
    """
    raw = '&'.join(['GET', urllib.parse.quote(url_path, safe=''), timestamp])
    sig = hmac.new(HMAC_SECRET, raw.encode(), hashlib.sha1)
    return base64.b64encode(sig.digest()).decode()


def fetch_json(url, params):
    """Make an authenticated GET request to the Frodo API.

    Returns (data_dict, status_code). Catches HTTP errors, network errors,
    and timeouts — all return a synthetic error dict so the caller can retry.
    """
    query = urllib.parse.urlencode(params)
    full_url = f'{url}?{query}'
    req = urllib.request.Request(full_url, headers={'User-Agent': USER_AGENT})
    try:
        with urllib.request.urlopen(req, timeout=15) as resp:
            return json.loads(resp.read().decode('utf-8')), resp.status
    except urllib.error.HTTPError as e:
        body = e.read().decode('utf-8', errors='replace')[:200]
        return {'error': body, 'code': e.code}, e.code
    except urllib.error.URLError as e:
        return {'error': f'Network error: {e.reason}'}, 0
    except socket.timeout:
        return {'error': 'Request timed out'}, 0
    except json.JSONDecodeError as e:
        return {'error': f'Invalid JSON response: {e}'}, 0


def preflight_check(user_id):
    """Verify user exists by fetching one page of book interests.

    Returns True if the user has any data, False if the user ID appears invalid.
    Prints a warning and continues if the check itself fails (network issue).
    """
    api_path = f'/api/v2/user/{user_id}/interests'
    ts = str(int(time.time()))
    sig = compute_signature(api_path, ts)
    params = {
        'type': 'book', 'status': 'done', 'start': 0, 'count': 1,
        'apiKey': API_KEY, '_ts': ts, '_sig': sig, 'os_rom': 'android',
    }
    data, code = fetch_json(f'{BASE_URL}{api_path}', params)
    if code == 0:
        print(f'Warning: Could not verify user ID (network issue). Proceeding anyway.')
        return True
    if code != 200:
        print(f'Error: API returned HTTP {code} for user "{user_id}".')
        print(f'  Check that the user ID is correct (from douban.com/people/<ID>/).')
        return False
    total = data.get('total', -1)
    if total == -1:
        print(f'Warning: Unexpected API response. Proceeding anyway.')
        return True
    return True


def fetch_all_interests(user_id, type_name, status):
    """Fetch all items for a given type+status combination.

    Paginates through the API, checking against the reported total
    (not page size) to handle pages with fewer items due to delisted content.
    """
    api_path = f'/api/v2/user/{user_id}/interests'
    all_items = []
    start = 0
    total = None
    retries = 0
    max_retries = 3
    page_count = 0

    while page_count < MAX_PAGES_SAFETY:
        page_count += 1
        ts = str(int(time.time()))
        sig = compute_signature(api_path, ts)
        params = {
            'type': type_name, 'status': status,
            'start': start, 'count': ITEMS_PER_PAGE,
            'apiKey': API_KEY, '_ts': ts, '_sig': sig, 'os_rom': 'android',
        }

        data, status_code = fetch_json(f'{BASE_URL}{api_path}', params)

        if status_code != 200:
            retries += 1
            if retries > max_retries:
                print(f'  Error: HTTP {status_code} after {max_retries} retries, stopping.')
                print(f'  See references/troubleshooting.md for common errors.')
                break
            delay = 5 * (2 ** (retries - 1))
            print(f'  HTTP {status_code}, retry {retries}/{max_retries}, waiting {delay}s...')
            time.sleep(delay)
            continue

        retries = 0

        if total is None:
            total = data.get('total', 0)
            if total == 0:
                return []
            print(f'  Total: {total}')

        interests = data.get('interests', [])
        if not interests:
            break

        all_items.extend(interests)
        print(f'  Fetched {start}-{start + len(interests)} ({len(all_items)}/{total})')

        if len(all_items) >= total:
            break
        start += len(interests)
        time.sleep(PAGE_DELAY)

    return all_items


def extract_rating(interest):
    """Convert Frodo API rating to star string.

    Frodo returns {value: N, max: 5} where N is 1-5.
    Some older entries may use max=10 scale (value 2-10).
    API values are typically integers; round() handles any edge cases.
    """
    r = interest.get('rating')
    if not r or not isinstance(r, dict):
        return ''
    val = r.get('value', 0)
    max_val = r.get('max', 5)
    if not val:
        return ''
    stars = round(val) if max_val <= 5 else round(val / 2)
    return '★' * max(0, min(5, stars))


def interest_to_row(interest, type_name, status_cn):
    """Convert a single Frodo API interest object to a CSV row dict."""
    subject = interest.get('subject', {})
    sid = subject.get('id', '')
    prefix = URL_PREFIX.get(type_name, 'https://www.douban.com/subject/')
    url = f'{prefix}{sid}/' if sid else subject.get('url', '')

    date_raw = interest.get('create_time', '') or ''
    date = date_raw[:10] if re.match(r'\d{4}-\d{2}-\d{2}', date_raw) else ''

    return {
        'title': subject.get('title', ''),
        'url': url,
        'date': date,
        'rating': extract_rating(interest),
        'status': status_cn,
        'comment': interest.get('comment', ''),
    }


def write_csv(filepath, rows):
    """Write rows to a CSV file with UTF-8 BOM for Excel compatibility."""
    with open(filepath, 'w', newline='', encoding='utf-8-sig') as f:
        writer = csv.DictWriter(f, fieldnames=CSV_FIELDS)
        writer.writeheader()
        writer.writerows(rows)


def main():
    user_id = os.environ.get('DOUBAN_USER', '').strip()
    if not user_id:
        print('Error: DOUBAN_USER environment variable is required')
        print('Usage: DOUBAN_USER=<your_douban_id> python3 douban-frodo-export.py')
        sys.exit(1)

    # Extract ID from URL if user pasted a full profile URL
    url_match = re.search(r'douban\.com/people/([A-Za-z0-9._-]+)', user_id)
    if url_match:
        user_id = url_match.group(1)

    if not re.match(r'^[A-Za-z0-9._-]+$', user_id):
        print(f'Error: DOUBAN_USER contains invalid characters: {user_id}')
        sys.exit(1)

    output_dir = get_output_dir(user_id)
    os.makedirs(output_dir, exist_ok=True)
    print(f'Douban Export for user: {user_id}')
    print(f'Output directory: {output_dir}\n')

    # Pre-flight: verify user ID is valid before spending time on full export
    if not preflight_check(user_id):
        sys.exit(1)

    # Collect data grouped by output file, then write all at the end.
    file_data = {}
    grand_total = 0

    for type_name, status, status_cn, outfile in CATEGORIES:
        print(f'=== {status_cn} ({type_name}) ===')
        items = fetch_all_interests(user_id, type_name, status)

        if outfile not in file_data:
            file_data[outfile] = []

        for item in items:
            file_data[outfile].append(interest_to_row(item, type_name, status_cn))

        count = len(items)
        grand_total += count
        if count > 0:
            print(f'  Collected: {count}\n')
        else:
            print(f'  (empty)\n')

        time.sleep(CATEGORY_DELAY)

    # Write CSV files
    print('--- Writing CSV files ---')
    for filename, rows in file_data.items():
        filepath = os.path.join(output_dir, filename)
        write_csv(filepath, rows)
        print(f'  {filename}: {len(rows)} rows')

    print(f'\nDone! {grand_total} total items exported to {output_dir}')


if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        print('\n\nExport interrupted by user.')
        sys.exit(130)