// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.  See the License for the
// specific language governing permissions and limitations
// under the License.

#include "exprs/vsearch.h"

#include <fmt/format.h>

#include <memory>
#include <roaring/roaring.hh>

#include "common/logging.h"
#include "common/status.h"
#include "core/column/column_const.h"
#include "exprs/function/function_search.h"
#include "exprs/vexpr_context.h"
#include "exprs/vliteral.h"
#include "exprs/vslot_ref.h"
#include "glog/logging.h"
#include "runtime/runtime_state.h"
#include "storage/index/inverted/inverted_index_reader.h"
#include "storage/olap_common.h"
#include "storage/segment/segment.h"

namespace doris {
using namespace segment_v2;

namespace {

struct SearchInputBundle {
    std::unordered_map<std::string, IndexIterator*> iterators;
    std::unordered_map<std::string, IndexFieldNameAndTypePair> field_types;
    std::unordered_map<std::string, int> field_name_to_column_id;
    std::vector<int> column_ids;
    ColumnsWithTypeAndName literal_args;
};

void add_search_binding_diagnostic(const IndexExecContext* index_context,
                                   const std::string& diagnostic) {
    VLOG_DEBUG << diagnostic;
    if (index_context == nullptr) {
        return;
    }
    const auto& index_query_context = index_context->get_index_query_context();
    if (index_query_context != nullptr && index_query_context->stats != nullptr) {
        index_query_context->stats->inverted_index_stats.add_binding_diagnostic(diagnostic);
    }
}

Status collect_search_inputs(const VSearchExpr& expr, VExprContext* context,
                             SearchInputBundle* bundle) {
    DCHECK(bundle != nullptr);

    auto index_context = context->get_index_context();
    if (index_context == nullptr) {
        LOG(WARNING) << "collect_search_inputs: No inverted index context available";
        return Status::InternalError("No inverted index context available");
    }

    // Get field bindings for variant subcolumn support
    const auto& search_param = expr.get_search_param();
    const auto& field_bindings = search_param.field_bindings;

    std::unordered_map<std::string, ColumnId> parent_to_base_column_id;
    std::unordered_map<std::string, std::string> parent_to_storage_field_prefix;

    // Resolve and cache the base (parent) column id for a variant field binding.
    // This avoids repeated schema lookups when multiple subcolumns share the same parent column.
    auto resolve_parent_column_id = [&](const std::string& parent_field, ColumnId* column_id) {
        // Guard against invalid inputs: variant bindings may miss parent_field, and callers must
        // provide a valid output pointer to receive the resolved id.
        if (parent_field.empty() || column_id == nullptr) {
            return false;
        }
        auto it = parent_to_base_column_id.find(parent_field);
        if (it != parent_to_base_column_id.end()) {
            *column_id = it->second;
            return true;
        }
        if (index_context == nullptr || index_context->segment() == nullptr) {
            return false;
        }
        const int32_t ordinal =
                index_context->segment()->tablet_schema()->field_index(parent_field);
        if (ordinal < 0) {
            return false;
        }
        ColumnId resolved_id = static_cast<ColumnId>(ordinal);
        parent_to_base_column_id.emplace(parent_field, resolved_id);
        if (auto* storage_name_type = index_context->get_storage_name_and_type_by_id(resolved_id);
            storage_name_type != nullptr) {
            parent_to_storage_field_prefix[parent_field] = storage_name_type->first;
        }
        *column_id = resolved_id;
        return true;
    };

    int child_index = 0; // Index for iterating through children
    for (const auto& child : expr.children()) {
        if (child->is_slot_ref()) {
            auto* column_slot_ref = assert_cast<VSlotRef*>(child.get());
            int column_id = column_slot_ref->column_id();

            // Determine the field_name from field_bindings (for variant subcolumns)
            // field_bindings and children should have the same order
            std::string field_name;
            const TSearchFieldBinding* binding = nullptr;
            if (child_index < field_bindings.size()) {
                // Use field_name from binding (may include "parent.subcolumn" for variant)
                binding = &field_bindings[child_index];
                field_name = binding->field_name;
            } else {
                // Fallback to column_name if binding not found
                field_name = column_slot_ref->column_name();
            }

            bundle->field_name_to_column_id[field_name] = column_id;

            auto* iterator = index_context->get_inverted_index_iterator_by_column_id(column_id);
            const auto* storage_name_type =
                    index_context->get_storage_name_and_type_by_column_id(column_id);
            bool field_added = false;
            // For variant subcolumns, slot_ref might not map to a real indexed column in the scan schema.
            // Fall back to the parent variant column's iterator and synthesize lucene field name.
            if (iterator == nullptr && binding != nullptr &&
                binding->__isset.is_variant_subcolumn && binding->is_variant_subcolumn &&
                binding->__isset.parent_field_name && !binding->parent_field_name.empty()) {
                ColumnId base_column_id = 0;
                if (resolve_parent_column_id(binding->parent_field_name, &base_column_id)) {
                    iterator = index_context->get_inverted_index_iterator_by_id(base_column_id);
                    const auto* base_storage_name_type =
                            index_context->get_storage_name_and_type_by_id(base_column_id);
                    if (iterator != nullptr && base_storage_name_type != nullptr) {
                        std::string prefix = base_storage_name_type->first;
                        if (auto pit =
                                    parent_to_storage_field_prefix.find(binding->parent_field_name);
                            pit != parent_to_storage_field_prefix.end() && !pit->second.empty()) {
                            prefix = pit->second;
                        } else {
                            parent_to_storage_field_prefix[binding->parent_field_name] = prefix;
                        }

                        std::string sub_path;
                        if (binding->__isset.subcolumn_path) {
                            sub_path = binding->subcolumn_path;
                        }
                        if (sub_path.empty()) {
                            // Fallback: strip "parent." prefix from logical field name
                            std::string pfx = binding->parent_field_name + ".";
                            if (field_name.starts_with(pfx)) {
                                sub_path = field_name.substr(pfx.size());
                            }
                        }
                        if (!sub_path.empty()) {
                            bundle->iterators[field_name] = iterator;
                            bundle->field_types[field_name] =
                                    std::make_pair(prefix + "." + sub_path, nullptr);
                            int base_column_index =
                                    index_context->column_index_by_id(base_column_id);
                            if (base_column_index >= 0) {
                                bundle->column_ids.emplace_back(base_column_index);
                            }
                            add_search_binding_diagnostic(
                                    index_context.get(),
                                    fmt::format("[VariantSearchBinding] phase=collect_inputs "
                                                "result=parent_fallback logical_field={} "
                                                "parent_field={} sub_path={} base_column_id={} "
                                                "stored_field={} reason=slot_iterator_missing",
                                                field_name, binding->parent_field_name, sub_path,
                                                base_column_id, prefix + "." + sub_path));
                            field_added = true;
                        }
                    }
                } else {
                    add_search_binding_diagnostic(
                            index_context.get(),
                            fmt::format("[VariantSearchBinding] phase=collect_inputs "
                                        "result=reject logical_field={} parent_field={} "
                                        "reason=parent_column_not_found",
                                        field_name, binding->parent_field_name));
                }
            }

            // Only collect fields that have iterators (materialized columns with indexes)
            if (!field_added && iterator != nullptr) {
                if (storage_name_type == nullptr) {
                    return Status::InternalError("storage_name_type not found for column {} in {}",
                                                 column_id, expr.expr_name());
                }

                bundle->iterators.emplace(field_name, iterator);
                bundle->field_types.emplace(field_name, *storage_name_type);
                bundle->column_ids.emplace_back(column_id);
                if (binding != nullptr && binding->__isset.is_variant_subcolumn &&
                    binding->is_variant_subcolumn) {
                    add_search_binding_diagnostic(
                            index_context.get(),
                            fmt::format("[VariantSearchBinding] phase=collect_inputs "
                                        "result=direct_iterator logical_field={} column_id={} "
                                        "stored_field={}",
                                        field_name, column_id, storage_name_type->first));
                }
            }

            child_index++;
        } else if (child->is_literal()) {
            auto* literal = assert_cast<VLiteral*>(child.get());
            bundle->literal_args.emplace_back(literal->get_column_ptr(), literal->get_data_type(),
                                              literal->expr_name());
        } else {
            // Check if this is ElementAt expression (for variant subcolumn access)
            if (child->expr_name() == "element_at" && child_index < field_bindings.size() &&
                field_bindings[child_index].__isset.is_variant_subcolumn &&
                field_bindings[child_index].is_variant_subcolumn) {
                // Variant subcolumn not materialized - skip, will create empty BitSetQuery in function_search
                add_search_binding_diagnostic(
                        index_context.get(),
                        fmt::format("[VariantSearchBinding] phase=collect_inputs "
                                    "result=unmaterialized_element_at logical_field={} "
                                    "parent_field={} sub_path={} reason=no_slot_ref",
                                    field_bindings[child_index].field_name,
                                    field_bindings[child_index].__isset.parent_field_name
                                            ? field_bindings[child_index].parent_field_name
                                            : "",
                                    field_bindings[child_index].__isset.subcolumn_path
                                            ? field_bindings[child_index].subcolumn_path
                                            : ""));
                child_index++;
                continue;
            }

            // Not a supported child type
            return Status::InvalidArgument("Unsupported child node type: {}", child->expr_name());
        }
    }

    return Status::OK();
}

} // namespace

VSearchExpr::VSearchExpr(const TExprNode& node) : VExpr(node) {
    if (node.__isset.search_param) {
        _search_param = node.search_param;
        _original_dsl = _search_param.original_dsl;
    }
}

Status VSearchExpr::prepare(RuntimeState* state, const RowDescriptor& row_desc,
                            VExprContext* context) {
    RETURN_IF_ERROR(VExpr::prepare(state, row_desc, context));
    const auto& query_options = state->query_options();
    if (query_options.__isset.enable_inverted_index_query_cache) {
        _enable_cache = query_options.enable_inverted_index_query_cache;
    }
    return Status::OK();
}

const std::string& VSearchExpr::expr_name() const {
    static const std::string name = "VSearchExpr";
    return name;
}

Status VSearchExpr::execute_column_impl(VExprContext* context, const Block* block,
                                        const Selector* selector, size_t count,
                                        ColumnPtr& result_column) const {
    if (fast_execute(context, selector, count, result_column)) {
        return Status::OK();
    }

    return Status::InternalError("SearchExpr should not be executed without inverted index");
}

Status VSearchExpr::evaluate_inverted_index(VExprContext* context, uint32_t segment_num_rows) {
    if (_search_param.original_dsl.empty()) {
        return Status::InvalidArgument("search DSL is empty");
    }

    auto index_context = context->get_index_context();
    if (!index_context) {
        LOG(WARNING) << "VSearchExpr: No inverted index context available";
        return Status::OK();
    }

    SearchInputBundle bundle;
    RETURN_IF_ERROR(collect_search_inputs(*this, context, &bundle));

    VLOG_DEBUG << "VSearchExpr: bundle.iterators.size()=" << bundle.iterators.size();

    const bool is_nested_query = _search_param.root.clause_type == "NESTED";
    if (bundle.iterators.empty() && !is_nested_query) {
        LOG(WARNING) << "VSearchExpr: No indexed columns available for evaluation, DSL: "
                     << _original_dsl;
        add_search_binding_diagnostic(
                index_context.get(),
                fmt::format("[VariantSearchBinding] phase=evaluate_search result=no_iterator "
                            "dsl={} reason=no_indexed_columns",
                            _original_dsl));
        auto empty_bitmap = InvertedIndexResultBitmap(std::make_shared<roaring::Roaring>(),
                                                      std::make_shared<roaring::Roaring>());
        index_context->set_index_result_for_expr(this, std::move(empty_bitmap));
        return Status::OK();
    }

    auto index_query_context = index_context->get_index_query_context();

    auto function = std::make_shared<FunctionSearch>();
    auto result_bitmap = InvertedIndexResultBitmap();
    auto status = function->evaluate_inverted_index_with_search_param(
            _search_param, bundle.field_types, bundle.iterators, segment_num_rows, result_bitmap,
            _enable_cache, index_context.get(), bundle.field_name_to_column_id,
            index_query_context);

    if (!status.ok()) {
        LOG(WARNING) << "VSearchExpr: Function evaluation failed: " << status.to_string();
        return status;
    }

    index_context->set_index_result_for_expr(this, result_bitmap);
    for (int column_id : bundle.column_ids) {
        index_context->set_true_for_index_status(this, column_id);
    }

    return Status::OK();
}

} // namespace doris