"""Adapt readable WeChat 4 tables to the workbench's normalized import format."""
import hashlib
import re
import sqlite3
import xml.etree.ElementTree as ET
from pathlib import Path


def quote(name):
    return '"' + name.replace('"', '""') + '"'


def open_db(path):
    db = sqlite3.connect(Path(path).resolve().as_uri() + '?mode=ro&immutable=1', uri=True)
    db.row_factory = sqlite3.Row
    return db


def tables(db):
    return [r[0] for r in db.execute("SELECT name FROM sqlite_master WHERE type='table'")]


def decode(value):
    if value is None:
        return ''
    if not isinstance(value, bytes):
        return str(value)
    if value.startswith(b'\x28\xb5\x2f\xfd'):
        try:
            import zstandard
            value = zstandard.ZstdDecompressor().decompress(value, max_output_size=16*1024**2)
        except ImportError:
            raise ValueError('缺少压缩文本支持，请在连接页面点击“安装文本解压支持”') from None
    try:
        return value.decode('utf-8')
    except UnicodeError:
        raise ValueError('正文含未识别编码，已拒绝把二进制内容当文本') from None


def contacts(root):
    names = {}
    path = root / 'contact/contact.db'
    if not path.exists():
        raise ValueError('缺少联系人库，无法可靠关联会话身份')
    db = open_db(path)
    try:
        for table in tables(db):
            cols = {r[1] for r in db.execute('PRAGMA table_info(' + quote(table) + ')')}
            user = next((v for v in ('username', 'user_name', 'UserName') if v in cols), None)
            if not user:
                continue
            labels = [v for v in ('remark', 'remark_name', 'nick_name', 'nickname', 'NickName') if v in cols]
            for row in db.execute('SELECT ' + ','.join(quote(v) for v in [user]+labels) + ' FROM ' + quote(table)):
                uid = decode(row[0])
                if uid:
                    names[uid] = next((decode(row[v]) for v in labels if row[v]), uid)
    finally:
        db.close()
    if not names:
        raise ValueError('联系人库结构未识别；需要为这个版本适配字段')
    return names


def message_rows(root, account, include_biz=False):
    names = contacts(root)
    chats = {hashlib.md5(uid.encode()).hexdigest(): uid for uid in names}
    files = sorted((root / 'message').glob('message_[0-9]*.db'))
    if include_biz:
        files += sorted((root / 'message').glob('biz_message_[0-9]*.db'))
    if not files:
        raise ValueError('没有找到可读消息分片')
    for path in files:
        db = open_db(path)
        try:
            all_tables = tables(db)
            ids = {}
            for table in all_tables:
                if table.lower() == 'name2id':
                    cols = {r[1] for r in db.execute('PRAGMA table_info(' + quote(table) + ')')}
                    field = next((c for c in ('user_name', 'username') if c in cols), None)
                    if field:
                        for row in db.execute('SELECT rowid,' + quote(field) + ' FROM ' + quote(table)):
                            uid = decode(row[1])
                            ids[row[0]] = uid
                            chats[hashlib.md5(uid.encode()).hexdigest()] = uid
            for table in all_tables:
                match = re.fullmatch(r'(?:Msg|Chat)_([a-fA-F0-9]{32})', table)
                if not match:
                    if table.startswith(('Msg_', 'Chat_')):
                        raise ValueError('消息表名称格式未识别，需要版本适配；没有静默跳过')
                    continue
                uid = chats.get(match[1].lower())
                if not uid:
                    raise ValueError('有消息表无法关联会话身份；请补充完整的联系人/Name2Id 数据后重试')
                cols = {r[1] for r in db.execute('PRAGMA table_info(' + quote(table) + ')')}
                required = {'create_time', 'message_content', 'local_type', 'real_sender_id'}
                if not required <= cols:
                    raise ValueError('消息表字段与支持的微信 4.x 格式不同，需要版本适配')
                for raw in db.execute('SELECT rowid AS _rowid_, * FROM ' + quote(table)):
                    row = dict(raw)
                    typ = int(row['local_type']) & 0xffffffff
                    sender = ids.get(row['real_sender_id'])
                    if not sender:
                        raise ValueError('消息发送人 ID 无法关联，已停止导入，避免错误归属')
                    content = decode(row['message_content'])
                    if not content and row.get('compress_content'):
                        content = decode(row['compress_content'])
                    ref = ''
                    is_text = typ == 1
                    if uid.endswith('@chatroom') and content.startswith(sender + ':\n'):
                        content = content[len(sender)+2:]
                    if content.startswith('<') and typ == 49:
                        try:
                            xml = ET.fromstring(content)
                            title = xml.findtext('.//appmsg/title') or ''
                            ref = xml.findtext('.//refermsg/content') or ''
                            is_text = xml.findtext('.//appmsg/type') == '57'
                            if title:
                                content = title
                        except ET.ParseError:
                            pass
                    source_id = row.get('server_id') or f"{path.name}:{table}:{row.get('local_id',row['_rowid_'])}"
                    yield dict(id=str(source_id), conversation=names.get(uid, uid), conversation_id=account+'::'+uid,
                               kind='group' if uid.endswith('@chatroom') else 'private', sender=names.get(sender, sender),
                               sender_id=sender, timestamp=row['create_time'], content=content or f'［非文字消息 {typ}］',
                               message_type='text' if is_text else str(typ), quote=ref)
        finally:
            db.close()