#
#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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#  limitations under the License.
#
"""
Document Metadata Service

Manages document-level metadata storage in ES/Infinity.
This is the SOLE source of truth for document metadata - MySQL meta_fields column has been removed.
"""

import json
import logging
import re
from copy import deepcopy
from typing import Dict, List, Optional

from api.db.db_models import DB, Document
from common import settings
from common.metadata_utils import dedupe_list
from api.db.db_models import Knowledgebase
from common.doc_store.doc_store_base import OrderByExpr


class DocMetadataService:
    """Service for managing document metadata in ES/Infinity"""

    @staticmethod
    def _get_doc_meta_index_name(tenant_id: str) -> str:
        """
        Get the index name for document metadata.

        Args:
            tenant_id: Tenant ID

        Returns:
            Index name for document metadata
        """
        return f"ragflow_doc_meta_{tenant_id}"

    @staticmethod
    def _extract_metadata(flat_meta: Dict) -> Dict:
        """
        Extract metadata from ES/Infinity document format.

        Args:
            flat_meta: Raw document from ES/Infinity with meta_fields field

        Returns:
            Simple metadata dictionary
        """
        if not flat_meta or not isinstance(flat_meta, dict):
            return {}

        meta_fields = flat_meta.get('meta_fields')
        if not meta_fields:
            return {}

        # Parse JSON string if needed
        if isinstance(meta_fields, str):
            import json
            try:
                return json.loads(meta_fields)
            except json.JSONDecodeError:
                return {}

        # Already a dict, return as-is
        if isinstance(meta_fields, dict):
            return meta_fields

        return {}

    @staticmethod
    def _extract_doc_id(doc: Dict, hit: Dict = None) -> str:
        """
        Extract document ID from various formats.

        Args:
            doc: Document dictionary (from DataFrame or list format)
            hit: Hit dictionary (from ES format with _id field)

        Returns:
            Document ID or empty string
        """
        if hit:
            # ES format: doc is in _source, id is in _id
            return hit.get('_id', '')
        # DataFrame or list format: check multiple possible fields
        return doc.get("doc_id") or doc.get("_id") or doc.get("id", "")

    @classmethod
    def _iter_search_results(cls, results):
        """
        Iterate over search results in various formats (DataFrame, ES, OceanBase, list).

        Yields:
            Tuple of (doc_id, doc_dict) for each document

        Args:
            results: Search results from ES/Infinity/OceanBase in any format
        """
        # Handle tuple return from Infinity: (DataFrame, int)
        # Check this FIRST because pandas DataFrames also have __getitem__
        if isinstance(results, tuple) and len(results) == 2:
            results = results[0]  # Extract DataFrame from tuple

        # Check if results is a pandas DataFrame (from Infinity)
        if hasattr(results, 'iterrows'):
            # Handle pandas DataFrame - use iterrows() to iterate over rows
            for _, row in results.iterrows():
                doc = dict(row)  # Convert Series to dict
                doc_id = cls._extract_doc_id(doc)
                if doc_id:
                    yield doc_id, doc

        # Check if ES format (has 'hits' key)
        # Note: ES returns ObjectApiResponse which is dict-like but not isinstance(dict)
        elif hasattr(results, 'get') and 'hits' in results:
            # ES format: {"hits": {"hits": [{"_source": {...}, "_id": "..."}]}}
            hits = results.get('hits', {}).get('hits', [])
            for hit in hits:
                doc = hit.get('_source', {})
                doc_id = cls._extract_doc_id(doc, hit)
                if doc_id:
                    yield doc_id, doc

        # Handle list of dicts or other formats
        elif isinstance(results, list):
            for res in results:
                if isinstance(res, dict):
                    docs = [res]
                else:
                    docs = res

                for doc in docs:
                    doc_id = cls._extract_doc_id(doc)
                    if doc_id:
                        yield doc_id, doc

        # Check if OceanBase SearchResult format
        elif hasattr(results, 'chunks') and hasattr(results, 'total'):
            # OceanBase format: SearchResult(total=int, chunks=[{...}, {...}])
            for doc in results.chunks:
                doc_id = cls._extract_doc_id(doc)
                if doc_id:
                    yield doc_id, doc

    @classmethod
    def _search_metadata(cls, kb_id: str, condition: Dict = None):
        """
        Common search logic for metadata queries.
        Uses pagination internally to retrieve data from the index.

        Args:
            kb_id: Knowledge base ID
            condition: Optional search condition (defaults to {"kb_id": kb_id})

        Returns:
            Search results from ES/Infinity, or empty list if index doesn't exist
        """
        kb = Knowledgebase.get_by_id(kb_id)
        if not kb:
            return []

        tenant_id = kb.tenant_id
        index_name = cls._get_doc_meta_index_name(tenant_id)

        # Check if metadata index exists, create if it doesn't
        if not settings.docStoreConn.index_exist(index_name, ""):
            logging.debug(f"Metadata index {index_name} does not exist, creating it")
            result = settings.docStoreConn.create_doc_meta_idx(index_name)
            if result is False:
                logging.error(f"Failed to create metadata index {index_name}")
                return []
            logging.debug(f"Successfully created metadata index {index_name}")

        if condition is None:
            condition = {"kb_id": kb_id}

        # Add sort by id for ES to enable search_after on large data
        order_by = OrderByExpr()
        if not settings.DOC_ENGINE_INFINITY:
            order_by.asc("id")

        page_size = 1000
        all_results = []
        page = 0

        while True:
            results = settings.docStoreConn.search(
                select_fields=["*"],
                highlight_fields=[],
                condition=condition,
                match_expressions=[],
                order_by=order_by,
                offset=page * page_size,
                limit=page_size,
                index_names=index_name,
                knowledgebase_ids=[kb_id]
            )

            # Handle different result formats
            if results is None:
                break

            # Extract docs from results
            page_docs = []
            total_count = None  # Used for Infinity to determine if more results exist

            # Check for Infinity format first (DataFrame, total) tuple
            if isinstance(results, tuple) and len(results) == 2:
                df, total_count = results
                if hasattr(df, 'iterrows'):
                    # Pandas DataFrame from Infinity
                    page_docs = df.to_dict('records')
                else:
                    page_docs = list(df) if df else []
            # Check for ES format (dict with 'hits' key)
            elif hasattr(results, 'get') and 'hits' in results:
                hits_obj = results.get('hits', {})
                hits = hits_obj.get('hits', [])
                page_docs = []
                for hit in hits:
                    doc = hit.get('_source', {})
                    doc['id'] = hit.get('_id', '')  # Add _id as 'id' for _extract_doc_id to work
                    page_docs.append(doc)
                # Extract total count from ES response
                total_hits = hits_obj.get('total', {})
                if isinstance(total_hits, dict):
                    total_count = total_hits.get('value', len(page_docs))
                else:
                    total_count = total_hits if total_hits else len(page_docs)
            # Handle list/iterable results
            elif hasattr(results, '__iter__') and not isinstance(results, dict):
                page_docs = list(results)
            else:
                page_docs = []

            if not page_docs:
                break

            all_results.extend(page_docs)
            page += 1

            # Determine if there are more results to fetch
            # For Infinity: use total_count if available
            if total_count is not None:
                if len(all_results) >= total_count:
                    break
            else:
                # For ES or other: check if we got fewer than page_size
                if len(page_docs) < page_size:
                    break

        logging.debug(f"[_search_metadata] Retrieved {len(all_results)} total results for kb_id: {kb_id}")
        return all_results

    @classmethod
    def _split_combined_values(cls, meta_fields: Dict) -> Dict:
        """
        Post-process metadata to split combined values by common delimiters.

        For example: "关羽、孙权、张辽" -> ["关羽", "孙权", "张辽"]
        This fixes LLM extraction where multiple values are extracted as one combined value.
        Also removes duplicates after splitting.

        Args:
            meta_fields: Metadata dictionary

        Returns:
            Processed metadata with split values
        """
        if not meta_fields or not isinstance(meta_fields, dict):
            return meta_fields

        processed = {}
        for key, value in meta_fields.items():
            if isinstance(value, list):
                # Process each item in the list
                new_values = []
                for item in value:
                    if isinstance(item, str):
                        # Split by common delimiters: Chinese comma (、), regular comma (,), pipe (|), semicolon (;), Chinese semicolon (；)
                        # Also handle mixed delimiters and spaces
                        split_items = re.split(r'[、,，;；|]+', item.strip())
                        # Trim whitespace and filter empty strings
                        split_items = [s.strip() for s in split_items if s.strip()]
                        if split_items:
                            new_values.extend(split_items)
                        else:
                            # Keep original if no split happened
                            new_values.append(item)
                    else:
                        new_values.append(item)
                # Remove duplicates while preserving order.
                # Use string-based dedupe to support unhashable values (e.g. dict entries).
                processed[key] = dedupe_list(new_values)
            else:
                processed[key] = value

        if processed != meta_fields:
            logging.debug(f"[METADATA SPLIT] Split combined values: {meta_fields} -> {processed}")
        return processed

    @classmethod
    @DB.connection_context()
    def insert_document_metadata(cls, doc_id: str, meta_fields: Dict) -> bool:
        """
        Insert document metadata into ES/Infinity.

        Args:
            doc_id: Document ID
            meta_fields: Metadata dictionary

        Returns:
            True if successful, False otherwise
        """
        try:
            # Get document with tenant_id (need to join with Knowledgebase)
            doc_query = Document.select(Document, Knowledgebase.tenant_id).join(
                Knowledgebase, on=(Knowledgebase.id == Document.kb_id)
            ).where(Document.id == doc_id)

            doc = doc_query.first()
            if not doc:
                logging.warning(f"Document {doc_id} not found for metadata insertion")
                return False

            # Extract document fields
            doc_obj = doc  # This is the Document object
            tenant_id = doc.knowledgebase.tenant_id  # Get tenant_id from joined Knowledgebase
            kb_id = doc_obj.kb_id

            # Prepare metadata document
            doc_meta = {
                "id": doc_obj.id,
                "kb_id": kb_id,
            }

            # Store metadata as JSON object in meta_fields column (same as MySQL structure)
            if meta_fields:
                # Post-process to split combined values by common delimiters
                meta_fields = cls._split_combined_values(meta_fields)
                doc_meta["meta_fields"] = meta_fields
            else:
                doc_meta["meta_fields"] = {}

            # Ensure index/table exists (per-tenant for both ES and Infinity)
            index_name = cls._get_doc_meta_index_name(tenant_id)

            # Check if table exists
            table_exists = settings.docStoreConn.index_exist(index_name, kb_id)
            logging.debug(f"Metadata table exists check: {index_name} -> {table_exists}")

            # Create index if it doesn't exist
            if not table_exists:
                logging.debug(f"Creating metadata table: {index_name}")
                # Both ES and Infinity now use per-tenant metadata tables
                result = settings.docStoreConn.create_doc_meta_idx(index_name)
                logging.debug(f"Table creation result: {result}")
                if result is False:
                    logging.error(f"Failed to create metadata table {index_name}")
                    return False
            else:
                logging.debug(f"Metadata table already exists: {index_name}")

            # Insert into ES/Infinity
            result = settings.docStoreConn.insert(
                [doc_meta],
                index_name,
                kb_id
            )

            if result:
                logging.error(f"Failed to insert metadata for document {doc_id}: {result}")
                return False
            # Force refresh so metadata is immediately searchable.
            # Both Elasticsearch and OpenSearch backends expose refresh_idx;
            # Infinity does not need a manual refresh.
            if not settings.DOC_ENGINE_INFINITY:
                refresh_idx = getattr(settings.docStoreConn, "refresh_idx", None)
                if callable(refresh_idx):
                    if refresh_idx(index_name):
                        logging.debug(f"Refreshed metadata index: {index_name}")
                    else:
                        # A failed refresh can leave just-inserted metadata
                        # invisible to subsequent reads; surface it so operators
                        # can correlate stale-read complaints with the cause.
                        logging.warning(
                            f"Failed to refresh metadata index {index_name} on backend "
                            f"{type(settings.docStoreConn).__name__}; "
                            f"metadata may not be immediately searchable"
                        )
                else:
                    logging.debug(f"Backend {type(settings.docStoreConn).__name__} has no refresh_idx; skipping")

            logging.debug(f"Successfully inserted metadata for document {doc_id}")
            return True

        except Exception as e:
            logging.error(f"Error inserting metadata for document {doc_id}: {e}")
            return False

    @classmethod
    @DB.connection_context()
    def update_document_metadata(cls, doc_id: str, meta_fields: Dict) -> bool:
        """
        Update document metadata in ES/Infinity.

        For Elasticsearch: Uses partial update to directly update the meta_fields field.
        For Infinity: Falls back to delete+insert (Infinity doesn't support partial updates well).

        Args:
            doc_id: Document ID
            meta_fields: Metadata dictionary

        Returns:
            True if successful, False otherwise
        """
        try:
            # Get document with tenant_id
            doc_query = Document.select(Document, Knowledgebase.tenant_id).join(
                Knowledgebase, on=(Knowledgebase.id == Document.kb_id)
            ).where(Document.id == doc_id)

            doc = doc_query.first()
            if not doc:
                logging.warning(f"Document {doc_id} not found for metadata update")
                return False

            # Extract fields
            doc_obj = doc
            tenant_id = doc.knowledgebase.tenant_id
            kb_id = doc_obj.kb_id
            index_name = cls._get_doc_meta_index_name(tenant_id)

            # Post-process to split combined values
            processed_meta = cls._split_combined_values(meta_fields)

            logging.debug(
                f"[update_document_metadata] Updating doc_id: {doc_id}, kb_id: {kb_id}, meta_fields: {processed_meta}")

            # For Elasticsearch, use efficient partial update
            if not settings.DOC_ENGINE_INFINITY and not settings.DOC_ENGINE_OCEANBASE:
                # Check if index exists first
                index_exists = settings.docStoreConn.index_exist(index_name, "")
                if not index_exists:
                    # Index doesn't exist - create it and insert directly
                    logging.debug(
                        f"[update_document_metadata] Index {index_name} does not exist, creating and inserting")
                    result = settings.docStoreConn.create_doc_meta_idx(index_name)
                    if result is False:
                        logging.error(f"Failed to create metadata index {index_name}")
                        return False
                    return cls.insert_document_metadata(doc_id, processed_meta)

                # Index exists - check if document exists
                try:
                    doc_exists = settings.docStoreConn.get(
                        doc_id,
                        index_name,
                        [kb_id]
                    )
                    if doc_exists:
                        # Document exists - replace meta_fields entirely.
                        # Using update with a `doc` body would deep-merge the meta_fields
                        # object and retain old keys that should be removed, so we delegate
                        # to a backend-provided scripted assignment that fully overwrites it.
                        replace_meta_fields = getattr(settings.docStoreConn, "replace_meta_fields", None)
                        if callable(replace_meta_fields) and replace_meta_fields(index_name, doc_id, processed_meta):
                            logging.debug(
                                f"Successfully updated metadata for document {doc_id} via {type(settings.docStoreConn).__name__}.replace_meta_fields")
                            return True
                        logging.warning(
                            f"replace_meta_fields unavailable or failed on backend "
                            f"{type(settings.docStoreConn).__name__}; falling back to delete+insert"
                        )
                        # Mirror the Infinity fallback below so a failed scripted
                        # replace still guarantees full overwrite semantics rather
                        # than leaking through the "document not found" branch.
                        cls.delete_document_metadata(doc_id, kb_id, tenant_id)
                        return cls.insert_document_metadata(doc_id, processed_meta)
                except Exception as e:
                    logging.debug(f"Document {doc_id} not found in index, will insert: {e}")

                # Document doesn't exist - insert new
                logging.debug(f"[update_document_metadata] Document {doc_id} not found, inserting new")
                return cls.insert_document_metadata(doc_id, processed_meta)

            # For Infinity or as fallback: use delete+insert
            logging.debug(f"[update_document_metadata] Using delete+insert method for doc_id: {doc_id}")
            cls.delete_document_metadata(doc_id, kb_id, tenant_id)
            return cls.insert_document_metadata(doc_id, processed_meta)

        except Exception as e:
            logging.error(f"Error updating metadata for document {doc_id}: {e}")
            return False

    @classmethod
    @DB.connection_context()
    def delete_document_metadata(cls, doc_id: str, kb_id: str, tenant_id: str = None) -> bool:
        """
        Delete document metadata from ES/Infinity.
        Also drops the metadata table if it becomes empty (efficiently).
        If document has no metadata in the table, this is a no-op.

        Args:
            doc_id: Document ID
            kb_id: Knowledge base ID
            tenant_id: Tenant ID, if not provided, get it from kb_id

        Returns:
            True if successful (or no metadata to delete), False otherwise
        """
        try:
            logging.debug(f"[METADATA DELETE] Starting metadata deletion for document: {doc_id}")

            # Get tenant_id from kb_id if not provided
            if tenant_id is None:
                kb = Knowledgebase.get_or_none(Knowledgebase.id == kb_id)
                if not kb:
                    logging.warning(f"Knowledgebase {kb_id} not found for metadata deletion")
                    return False
                tenant_id = kb.tenant_id

            index_name = cls._get_doc_meta_index_name(tenant_id)
            logging.debug(f"[delete_document_metadata] Deleting doc_id: {doc_id}, kb_id: {kb_id}, index: {index_name}")

            # Check if metadata table exists before attempting deletion
            # This is the key optimization - no table = no metadata = nothing to delete
            if not settings.docStoreConn.index_exist(index_name, ""):
                logging.debug(
                    f"Metadata table {index_name} does not exist, skipping metadata deletion for document {doc_id}")
                return True  # No metadata to delete is considered success

            # Try to get the metadata to confirm it exists before deleting
            # This is more efficient than attempting delete on non-existent records
            try:
                existing_metadata = settings.docStoreConn.get(
                    doc_id,
                    index_name,
                    [""]  # Empty list for metadata tables
                )
                logging.debug(f"[METADATA DELETE] Get result: {existing_metadata is not None}")
                if not existing_metadata:
                    logging.debug(f"[METADATA DELETE] Document {doc_id} has no metadata in table, skipping deletion")
                    return True  # No metadata to delete is success
            except Exception as e:
                # If get fails, document might not exist in metadata table, which is fine
                logging.error(f"[METADATA DELETE] Get failed: {e}")
                # Continue to check/drop table if needed

            # Delete from ES/Infinity (only if metadata exists)
            # For metadata tables, pass kb_id for the delete operation
            # The delete() method will detect it's a metadata table and skip the kb_id filter
            logging.debug(f"[METADATA DELETE] Deleting metadata with condition: {{'id': '{doc_id}'}}")
            deleted_count = settings.docStoreConn.delete(
                {"id": doc_id},
                index_name,
                kb_id  # Pass actual kb_id (delete() will handle metadata tables correctly)
            )
            logging.debug(f"[METADATA DELETE] Deleted count: {deleted_count}")
            return True

        except Exception as e:
            logging.error(f"Error deleting metadata for document {doc_id}: {e}")
            return False

    @classmethod
    def _drop_empty_metadata_table(cls, index_name: str, tenant_id: str) -> None:
        """
        Check if metadata table is empty and drop it if so.
        Uses optimized count query instead of full search.
        This prevents accumulation of empty metadata tables.

        Args:
            index_name: Metadata table/index name
            tenant_id: Tenant ID
        """
        try:
            logging.debug(f"[DROP EMPTY TABLE] Starting empty table check for: {index_name}")

            # Check if table exists first (cheap operation)
            if not settings.docStoreConn.index_exist(index_name, ""):
                logging.debug(f"[DROP EMPTY TABLE] Metadata table {index_name} does not exist, skipping")
                return

            logging.debug(f"[DROP EMPTY TABLE] Table {index_name} exists, checking if empty...")

            # Use the backend-native count primitive when available (ES + OS).
            # No need to refresh since delete operation already uses refresh=True.
            # The invocation lives inside the try/except so a future backend
            # whose count_idx raises (instead of returning the -1 sentinel)
            # still falls through to the search-based empty-table check.
            count_idx = getattr(settings.docStoreConn, "count_idx", None)
            try:
                count_value = count_idx(index_name) if callable(count_idx) else -1
                if count_value < 0:
                    raise RuntimeError("native count_idx unavailable or failed")
                logging.debug(f"[DROP EMPTY TABLE] count_idx API result: {count_value} documents")
                is_empty = (count_value == 0)
            except Exception as e:
                logging.warning(f"[DROP EMPTY TABLE] Count API failed, falling back to search: {e}")
                # Fallback to search if count fails
                results = settings.docStoreConn.search(
                    select_fields=["id"],
                    highlight_fields=[],
                    condition={},
                    match_expressions=[],
                    order_by=OrderByExpr(),
                    offset=0,
                    limit=1,  # Only need 1 result to know if table is non-empty
                    index_names=index_name,
                    knowledgebase_ids=[""]  # Metadata tables don't filter by KB
                )

                logging.debug(f"[DROP EMPTY TABLE] Search results type: {type(results)}, results: {results}")

                # Check if empty based on return type (fallback search only)
                if isinstance(results, tuple) and len(results) == 2:
                    # Infinity returns (DataFrame, int)
                    df, total = results
                    logging.debug(
                        f"[DROP EMPTY TABLE] Infinity format - total: {total}, df length: {len(df) if hasattr(df, '__len__') else 'N/A'}")
                    is_empty = (total == 0 or (hasattr(df, '__len__') and len(df) == 0))
                elif hasattr(results, 'get') and 'hits' in results:
                    # ES format - MUST check this before hasattr(results, '__len__')
                    # because ES response objects also have __len__
                    total = results.get('hits', {}).get('total', {})
                    hits = results.get('hits', {}).get('hits', [])

                    # ES 7.x+: total is a dict like {'value': 0, 'relation': 'eq'}
                    # ES 6.x: total is an int
                    if isinstance(total, dict):
                        total_count = total.get('value', 0)
                    else:
                        total_count = total

                    logging.debug(f"[DROP EMPTY TABLE] ES format - total: {total_count}, hits count: {len(hits)}")
                    is_empty = (total_count == 0 or len(hits) == 0)
                elif hasattr(results, '__len__'):
                    # DataFrame or list (check this AFTER ES format)
                    result_len = len(results)
                    logging.debug(f"[DROP EMPTY TABLE] List/DataFrame format - length: {result_len}")
                    is_empty = result_len == 0
                else:
                    logging.warning(f"[DROP EMPTY TABLE] Unknown result format: {type(results)}")
                    is_empty = False

            if is_empty:
                logging.debug(f"[DROP EMPTY TABLE] Metadata table {index_name} is empty, dropping it")
                drop_result = settings.docStoreConn.delete_idx(index_name, "")
                logging.debug(f"[DROP EMPTY TABLE] Drop result: {drop_result}")
            else:
                logging.debug(f"[DROP EMPTY TABLE] Metadata table {index_name} still has documents, keeping it")

        except Exception as e:
            # Log but don't fail - metadata deletion was successful
            logging.error(f"[DROP EMPTY TABLE] Failed to check/drop empty metadata table {index_name}: {e}")

    @classmethod
    @DB.connection_context()
    def get_document_metadata(cls, doc_id: str) -> Dict:
        """
        Get document metadata from ES/Infinity.

        Args:
            doc_id: Document ID

        Returns:
            Metadata dictionary, empty dict if not found
        """
        try:
            # Get document with tenant_id
            doc_query = Document.select(Document, Knowledgebase.tenant_id).join(
                Knowledgebase, on=(Knowledgebase.id == Document.kb_id)
            ).where(Document.id == doc_id)

            doc = doc_query.first()
            if not doc:
                logging.warning(f"Document {doc_id} not found")
                return {}

            # Extract fields
            doc_obj = doc
            tenant_id = doc.knowledgebase.tenant_id
            kb_id = doc_obj.kb_id
            index_name = cls._get_doc_meta_index_name(tenant_id)

            # Try to get metadata from ES/Infinity
            metadata_doc = settings.docStoreConn.get(
                doc_id,
                index_name,
                [kb_id]
            )

            if metadata_doc:
                # Extract and unflatten metadata
                return cls._extract_metadata(metadata_doc)

            return {}

        except Exception as e:
            logging.error(f"Error getting metadata for document {doc_id}: {e}")
            return {}

    @classmethod
    @DB.connection_context()
    def get_flatted_meta_by_kbs(cls, kb_ids: List[str]) -> Dict:
        """
        Get flattened metadata for documents in knowledge bases.

        - Parses stringified JSON meta_fields when possible and skips non-dict or unparsable values.
        - Expands list values into individual entries.
          Example: {"tags": ["foo","bar"], "author": "alice"} ->
            meta["tags"]["foo"] = [doc_id], meta["tags"]["bar"] = [doc_id], meta["author"]["alice"] = [doc_id]
        Prefer for metadata_condition filtering and scenarios that must respect list semantics.

        Args:
            kb_ids: List of knowledge base IDs

        Returns:
            Metadata dictionary in format: {field_name: {value: [doc_ids]}}
        """
        try:
            # Get tenant_id from first KB
            kb = Knowledgebase.get_by_id(kb_ids[0])
            if not kb:
                return {}

            tenant_id = kb.tenant_id
            index_name = cls._get_doc_meta_index_name(tenant_id)

            condition = {"kb_id": kb_ids}
            order_by = OrderByExpr()

            # Query with large limit
            results = settings.docStoreConn.search(
                select_fields=["*"],  # Get all fields
                highlight_fields=[],
                condition=condition,
                match_expressions=[],
                order_by=order_by,
                offset=0,
                limit=10000,
                index_names=index_name,
                knowledgebase_ids=kb_ids
            )

            logging.debug(f"[get_flatted_meta_by_kbs] index_name: {index_name}, kb_ids: {kb_ids}")
            logging.debug(f"[get_flatted_meta_by_kbs] results type: {type(results)}")

            # Aggregate metadata
            meta = {}
            doc_count = 0

            # Use helper to iterate over results in any format
            for doc_id, doc in cls._iter_search_results(results):
                doc_count += 1
                # Extract metadata fields (exclude system fields)
                doc_meta = cls._extract_metadata(doc)

                for k, v in doc_meta.items():
                    if k not in meta:
                        meta[k] = {}

                    values = v if isinstance(v, list) else [v]
                    for vv in values:
                        if vv is None:
                            continue
                        sv = str(vv)
                        if sv not in meta[k]:
                            meta[k][sv] = []
                        meta[k][sv].append(doc_id)

            if doc_count >= 10000:
                logging.warning(f"[get_flatted_meta_by_kbs] Results hit the 10000 limit for KBs {kb_ids}.")

            logging.debug(f"[get_flatted_meta_by_kbs] KBs: {kb_ids}, Returning metadata: {meta}")
            return meta

        except Exception as e:
            logging.error(f"Error getting flattened metadata for KBs {kb_ids}: {e}")
            return {}

    @classmethod
    def filter_doc_ids_by_meta_pushdown(
            cls,
            kb_ids: List[str],
            filters: List[Dict],
            logic: str = "and",
            limit: int = 10000,
    ) -> Optional[List[str]]:
        """Run a metadata filter directly against ES or Infinity, returning matching doc IDs.

        Returns ``None`` to signal "push-down not viable, use the in-memory
        ``meta_filter`` fallback". Reasons for ``None``:

        - kb_ids or filters is empty
        - One of the user filters cannot be expressed in ES DSL or Infinity SQL
        - The request itself failed (network, mapping, missing index)

        On success returns the deduplicated, ordered list of document IDs the
        query matched. Callers can union or intersect this with their own
        base ``doc_ids`` rather than fetching the entire metadata table.
        """
        if not kb_ids or not filters:
            logging.debug("Metadata filter skipped: empty kb_ids or filters")
            return None

        try:
            kb = Knowledgebase.get_by_id(kb_ids[0])
        except Exception as e:
            logging.warning(f"Metadata filter cannot resolve tenant for kb {kb_ids[0]}: {e}")
            return None
        if not kb:
            return None

        tenant_id = kb.tenant_id
        index_name = cls._get_doc_meta_index_name(tenant_id)

        if not settings.docStoreConn.index_exist(index_name, ""):
            return []

        if settings.DOC_ENGINE_INFINITY:
            return cls._filter_doc_ids_by_metadata_infinity(
                index_name, kb_ids, filters, logic
            )
        else:
            return cls._filter_doc_ids_by_metadata_es(
                index_name, kb_ids, filters, logic, limit
            )

    @classmethod
    def _filter_doc_ids_by_metadata_es(
            cls,
            index_name: str,
            kb_ids: List[str],
            filters: List[Dict],
            logic: str,
            limit: int,
    ) -> Optional[List[str]]:
        """ES push-down path for metadata filtering."""
        from common.metadata_es_filter import (
            UnsupportedMetaFilter,
            build_meta_filter_query,
            extract_doc_ids,
            is_pushdown_supported,
        )

        es_client = getattr(settings.docStoreConn, "es", None)
        if es_client is None:
            return None

        if not is_pushdown_supported(filters):
            return None

        try:
            query_body = build_meta_filter_query(filters, logic, kb_ids)
        except UnsupportedMetaFilter as e:
            logging.error(f"ES build query failed: {e.reason}, filters={filters}")
            return None

        request_body = {
            **query_body,
            "size": limit,
            "_source": ["id"],
        }

        try:
            response = es_client.search(index=index_name, body=request_body)
        except Exception as e:
            logging.error(f"ES metadata filter failed for {index_name}: {e}")
            return None

        doc_ids = extract_doc_ids(response if isinstance(response, dict) else dict(response))
        seen: set[str] = set()
        unique: List[str] = []
        for did in doc_ids:
            if did in seen:
                continue
            seen.add(did)
            unique.append(did)

        if len(unique) >= limit:
            logging.warning(
                f"ES metadata filter hit limit {limit} for KBs {kb_ids}"
            )

        logging.debug(f"ES metadata filter returned {len(unique)} matches for KBs {kb_ids}")
        return unique

    @classmethod
    def _filter_doc_ids_by_metadata_infinity(
            cls,
            index_name: str,
            kb_ids: List[str],
            filters: List[Dict],
            logic: str,
    ) -> Optional[List[str]]:
        """Infinity push-down path for metadata filtering."""
        from common.metadata_infinity_filter import (
            build_infinity_filter,
            extract_doc_ids,
            is_pushdown_supported,
        )

        if not is_pushdown_supported(filters):
            return None

        try:
            sql_filter = build_infinity_filter(filters, logic)
            escaped_kb_ids = [k.replace("'", "''") for k in kb_ids]
            kb_filter = "kb_id IN (" + ", ".join([f"'{k}'" for k in escaped_kb_ids]) + ")"
            where_clause = f"{kb_filter} AND {sql_filter}"
            logging.debug(f"Infinity metadata filter: {where_clause}")

            inf_conn = settings.docStoreConn.connPool.get_conn()
            try:
                db_instance = inf_conn.get_database(settings.docStoreConn.dbName)
                table_instance = db_instance.get_table(index_name)
                df, _ = table_instance.output(["id"]).filter(where_clause).to_df()
                doc_ids = extract_doc_ids(df)
                logging.debug(
                    f"Infinity metadata filter returned {len(doc_ids)} doc IDs for kb_ids={kb_ids}, logic={logic}")
                return doc_ids
            finally:
                settings.docStoreConn.connPool.release_conn(inf_conn)
        except Exception:
            logging.warning("Metadata filter push-down failed; falling back to in-memory filter", exc_info=True)
            return None

    @classmethod
    def get_metadata_keys_by_kbs(cls, kb_ids: List[str]) -> List[str]:
        """
        Get unique metadata field names across multiple knowledge bases.

        Args:
            kb_ids: List of knowledge base IDs

        Returns:
            Sorted list of unique metadata field names
        """
        if not kb_ids:
            return []

        logging.debug(f"get_metadata_keys_by_kbs start: n_kbs={len(kb_ids)}")
        keys: set[str] = set()
        try:
            for kb_id in kb_ids:
                results = cls._search_metadata(kb_id, condition={"kb_id": kb_id})
                for _doc_id, doc in cls._iter_search_results(results):
                    doc_meta = cls._extract_metadata(doc)
                    if not isinstance(doc_meta, dict):
                        continue
                    keys.update(str(k) for k in doc_meta.keys())
            logging.debug(f"get_metadata_keys_by_kbs end: n_keys={len(keys)}, kb_ids={kb_ids}")
            return sorted(keys)
        except Exception as e:
            logging.error(f"Error getting metadata keys for KBs {kb_ids}: {e}")
            return []

    @classmethod
    def get_metadata_for_documents(cls, doc_ids: Optional[List[str]], kb_id: str) -> Dict[str, Dict]:
        """
        Get metadata fields for specific documents.
        Returns a mapping of doc_id -> meta_fields

        Args:
            doc_ids: List of document IDs (if None, gets all documents with metadata for the KB)
            kb_id: Knowledge base ID

        Returns:
            Dictionary mapping doc_id to meta_fields dict
        """
        try:
            condition = {"kb_id": kb_id}
            if doc_ids:
                condition["id"] = doc_ids
            results = cls._search_metadata(kb_id, condition=condition)
            if not results:
                return {}

            # Build mapping: doc_id -> meta_fields
            meta_mapping = {}

            # Use helper to iterate over results
            for doc_id, doc in cls._iter_search_results(results):

                # Extract metadata (handles both JSON strings and dicts)
                doc_meta = cls._extract_metadata(doc)
                if doc_meta:
                    meta_mapping[doc_id] = doc_meta

            logging.debug(
                f"[get_metadata_for_documents] Found metadata for {len(meta_mapping)}/{len(doc_ids) if doc_ids else 'all'} documents")
            return meta_mapping

        except Exception as e:
            logging.error(f"Error getting metadata for documents: {e}")
            return {}

    @classmethod
    @DB.connection_context()
    def get_metadata_summary(cls, kb_id: str, doc_ids=None) -> Dict:
        """
        Get metadata summary for documents in a knowledge base.

        Args:
            kb_id: Knowledge base ID
            doc_ids: Optional list of document IDs to filter by

        Returns:
            Dictionary with metadata field statistics in format:
            {
                "field_name": {
                    "type": "string" | "number" | "list" | "time",
                    "values": [("value1", count1), ("value2", count2), ...]  # sorted by count desc
                }
            }
        """

        def _is_time_string(value: str) -> bool:
            """Check if a string value is an ISO 8601 datetime (e.g., '2026-02-03T00:00:00')."""
            if not isinstance(value, str):
                return False
            return bool(re.match(r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}$', value))

        def _meta_value_type(value):
            """Determine the type of a metadata value."""
            if value is None:
                return None
            if isinstance(value, list):
                return "list"
            if isinstance(value, bool):
                return "string"
            if isinstance(value, (int, float)):
                return "number"
            if isinstance(value, str) and _is_time_string(value):
                return "time"
            return "string"

        try:
            condition = {"kb_id": kb_id}
            if doc_ids:
                condition["id"] = doc_ids
            results = cls._search_metadata(kb_id, condition=condition)
            if not results:
                return {}

            # Aggregate metadata
            summary = {}
            type_counter = {}

            logging.debug(f"[METADATA SUMMARY] KB: {kb_id}, doc_ids: {doc_ids}")

            # Use helper to iterate over results in any format
            for doc_id, doc in cls._iter_search_results(results):

                doc_meta = cls._extract_metadata(doc)

                for k, v in doc_meta.items():
                    # Track type counts for this field
                    value_type = _meta_value_type(v)
                    if value_type:
                        if k not in type_counter:
                            type_counter[k] = {}
                        type_counter[k][value_type] = type_counter[k].get(value_type, 0) + 1

                    # Aggregate value counts
                    values = v if isinstance(v, list) else [v]
                    for vv in values:
                        if vv is None:
                            continue
                        sv = str(vv)
                        if k not in summary:
                            summary[k] = {}
                        summary[k][sv] = summary[k].get(sv, 0) + 1

            # Build result with type information and sorted values
            result = {}
            for k, v in summary.items():
                values = sorted([(val, cnt) for val, cnt in v.items()], key=lambda x: x[1], reverse=True)
                type_counts = type_counter.get(k, {})
                value_type = "string"
                if type_counts:
                    value_type = max(type_counts.items(), key=lambda item: item[1])[0]
                result[k] = {"type": value_type, "values": values}

            logging.debug(f"[METADATA SUMMARY] Final result: {result}")
            return result

        except Exception as e:
            logging.error(f"Error getting metadata summary for KB {kb_id}: {e}")
            return {}

    @classmethod
    @DB.connection_context()
    def batch_update_metadata(cls, kb_id: str, doc_ids: List[str], updates=None, deletes=None) -> int:
        """
        Batch update metadata for documents in a knowledge base.

        Args:
            kb_id: Knowledge base ID
            doc_ids: List of document IDs to update
            updates: List of update operations, each with:
                - key: field name to update
                - value: new value
                - match (optional): only update if current value matches this
            deletes: List of delete operations, each with:
                - key: field name to delete from
                - value (optional): specific value to delete (if not provided, deletes the entire field)

        Returns:
            Number of documents updated

        Examples:
            updates = [{"key": "author", "value": "John"}]
            updates = [{"key": "tags", "value": "new", "match": "old"}]  # Replace "old" with "new" in tags list
            deletes = [{"key": "author"}]  # Delete entire author field
            deletes = [{"key": "tags", "value": "obsolete"}]  # Remove "obsolete" from tags list
        """
        updates = updates or []
        deletes = deletes or []
        if not doc_ids:
            return 0

        def _normalize_meta(meta):
            """Normalize metadata to a dict."""
            if isinstance(meta, str):
                try:
                    meta = json.loads(meta)
                except Exception:
                    return {}
            if not isinstance(meta, dict):
                return {}
            return deepcopy(meta)

        def _str_equal(a, b):
            """Compare two values as strings."""
            return str(a) == str(b)

        def _apply_updates(meta):
            """Apply update operations to metadata."""
            changed = False
            for upd in updates:
                key = upd.get("key")
                if not key:
                    continue

                new_value = upd.get("value")
                match_value = upd.get("match", None)
                match_provided = match_value is not None and match_value != ""

                if key not in meta:
                    if match_provided:
                        continue
                    meta[key] = dedupe_list(new_value) if isinstance(new_value, list) else new_value
                    changed = True
                    continue

                if isinstance(meta[key], list):
                    if not match_provided:
                        # No match provided, append new_value to the list
                        if isinstance(new_value, list):
                            meta[key] = dedupe_list(meta[key] + new_value)
                        else:
                            meta[key] = dedupe_list(meta[key] + [new_value])
                        changed = True
                    else:
                        # Replace items matching match_value with new_value
                        replaced = False
                        new_list = []
                        for item in meta[key]:
                            if _str_equal(item, match_value):
                                new_list.append(new_value)
                                replaced = True
                            else:
                                new_list.append(item)
                        if replaced:
                            meta[key] = dedupe_list(new_list)
                            changed = True
                else:
                    if not match_provided:
                        meta[key] = new_value
                        changed = True
                    else:
                        if _str_equal(meta[key], match_value):
                            meta[key] = new_value
                            changed = True
            return changed

        def _apply_deletes(meta):
            """Apply delete operations to metadata."""
            changed = False
            for d in deletes:
                key = d.get("key")
                if not key or key not in meta:
                    continue
                value = d.get("value", None)
                if isinstance(meta[key], list):
                    if value is None:
                        del meta[key]
                        changed = True
                        continue
                    new_list = [item for item in meta[key] if not _str_equal(item, value)]
                    if len(new_list) != len(meta[key]):
                        if new_list:
                            meta[key] = new_list
                        else:
                            del meta[key]
                        changed = True
                else:
                    if value is None or _str_equal(meta[key], value):
                        del meta[key]
                        changed = True
            return changed

        try:
            results = cls._search_metadata(kb_id, condition={"kb_id": kb_id, "id": doc_ids})
            if not results:
                results = []  # Treat as empty list if None

            updated_docs = 0
            found_doc_ids = set()

            logging.debug(f"[batch_update_metadata] Searching for doc_ids: {doc_ids}")

            # Use helper to iterate over results
            for doc_id, doc in cls._iter_search_results(results):
                found_doc_ids.add(doc_id)

                # Get current metadata
                current_meta = cls._extract_metadata(doc)
                meta = _normalize_meta(current_meta)
                original_meta = deepcopy(meta)

                logging.debug(f"[batch_update_metadata] Doc {doc_id}: current_meta={current_meta}, meta={meta}")
                logging.debug(f"[batch_update_metadata] Updates to apply: {updates}, Deletes: {deletes}")

                # Apply updates and deletes
                changed = _apply_updates(meta)
                logging.debug(f"[batch_update_metadata] After _apply_updates: changed={changed}, meta={meta}")
                changed = _apply_deletes(meta) or changed
                logging.debug(f"[batch_update_metadata] After _apply_deletes: changed={changed}, meta={meta}")

                # Update if changed
                if changed and meta != original_meta:
                    logging.debug(f"[batch_update_metadata] Updating doc_id: {doc_id}, meta: {meta}")
                    # If metadata is empty, delete the row entirely instead of keeping empty metadata
                    if not meta:
                        cls.delete_document_metadata(doc_id, kb_id, tenant_id=None)
                    else:
                        cls.update_document_metadata(doc_id, meta)
                    updated_docs += 1

            # Handle documents that don't have metadata rows yet
            # These documents weren't in the search results, so we need to insert new metadata for them
            doc_ids_set = set(doc_ids)
            missing_doc_ids = doc_ids_set - found_doc_ids
            if missing_doc_ids and updates:
                logging.debug(
                    f"[batch_update_metadata] Inserting new metadata for documents without metadata rows: {missing_doc_ids}")
                for doc_id in missing_doc_ids:
                    # Apply updates to create new metadata
                    meta = {}
                    _apply_updates(meta)
                    if meta:
                        # Only insert if there's actual metadata to add
                        cls.update_document_metadata(doc_id, meta)
                        updated_docs += 1
                        logging.debug(f"[batch_update_metadata] Inserted metadata for doc_id: {doc_id}, meta: {meta}")

            logging.debug(f"[batch_update_metadata] KB: {kb_id}, doc_ids: {doc_ids}, updated: {updated_docs}")
            return updated_docs

        except Exception as e:
            logging.error(f"Error in batch_update_metadata for KB {kb_id}: {e}")
            return 0
