/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * 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.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "process/ProductFilter.h"

#include <algorithm>

#include "ResourceTable.h"
#include "trace/TraceBuffer.h"

namespace aapt {

std::optional<ProductFilter::ResourceConfigValueIter> ProductFilter::SelectProductToKeep(
    const ResourceNameRef& name, ResourceConfigValueIter begin, ResourceConfigValueIter end,
    android::IDiagnostics* diag) {
  ResourceConfigValueIter default_product_iter = end;
  ResourceConfigValueIter selected_product_iter = end;

  for (ResourceConfigValueIter iter = begin; iter != end; ++iter) {
    ResourceConfigValue* config_value = iter->get();
    if (products_.find(config_value->product) != products_.end()) {
      if (selected_product_iter != end) {
        // We have two possible values for this product!
        diag->Error(android::DiagMessage(config_value->value->GetSource())
                    << "selection of product '" << config_value->product << "' for resource "
                    << name << " is ambiguous");

        ResourceConfigValue* previously_selected_config_value = selected_product_iter->get();
        diag->Note(android::DiagMessage(previously_selected_config_value->value->GetSource())
                   << "product '" << previously_selected_config_value->product
                   << "' is also a candidate");
        return std::nullopt;
      }

      // Select this product.
      selected_product_iter = iter;
    }

    if (config_value->product.empty() || config_value->product == "default") {
      if (default_product_iter != end) {
        // We have two possible default values.
        diag->Error(android::DiagMessage(config_value->value->GetSource())
                    << "multiple default products defined for resource " << name);

        ResourceConfigValue* previously_default_config_value = default_product_iter->get();
        diag->Note(android::DiagMessage(previously_default_config_value->value->GetSource())
                   << "default product also defined here");
        return std::nullopt;
      }

      // Mark the default.
      default_product_iter = iter;
    }
  }

  if (remove_default_config_values_) {
    // If we are leaving only a specific product, return early here instead of selecting the default
    // value. Returning end here will cause this value set to be skipped, and will be removed with
    // ClearEmptyValues method.
    return selected_product_iter;
  }

  if (default_product_iter == end) {
    diag->Error(android::DiagMessage() << "no default product defined for resource " << name);
    return std::nullopt;
  }

  if (selected_product_iter == end) {
    selected_product_iter = default_product_iter;
  }
  return selected_product_iter;
}

bool ProductFilter::Consume(IAaptContext* context, ResourceTable* table) {
  TRACE_NAME("ProductFilter::Consume");
  bool error = false;
  for (auto& pkg : table->packages) {
    for (auto& type : pkg->types) {
      for (auto& entry : type->entries) {
        std::vector<std::unique_ptr<ResourceConfigValue>> new_values;

        ResourceConfigValueIter iter = entry->values.begin();
        ResourceConfigValueIter start_range_iter = iter;
        while (iter != entry->values.end()) {
          ++iter;
          if (iter == entry->values.end() || (*iter)->config != (*start_range_iter)->config) {
            // End of the array, or we saw a different config,
            // so this must be the end of a range of products.
            // Select the product to keep from the set of products defined.
            ResourceNameRef name(pkg->name, type->named_type, entry->name);
            auto value_to_keep =
                SelectProductToKeep(name, start_range_iter, iter, context->GetDiagnostics());
            if (!value_to_keep.has_value()) {
              // An error occurred, we could not pick a product.
              error = true;
            } else if (auto val = value_to_keep.value(); val != iter) {
              // We selected a product to keep. Move it to the new array.
              if (remove_default_config_values_) {
                // We are filtering values with the given product. The selected value here will be
                // a new default value, and all other values will be removed.
                new_values.push_back(
                    std::make_unique<ResourceConfigValue>((*val)->config, android::StringPiece{}));
                new_values.back()->value = std::move((*val)->value);
              } else {
                new_values.push_back(std::move(*val));
              }
            }

            // Start the next range of products.
            start_range_iter = iter;
          }
        }

        // Now move the new values in to place.
        entry->values = std::move(new_values);
      }
    }
  }

  if (remove_default_config_values_) {
    ClearEmptyValues(table);
  }

  return !error;
}

void ProductFilter::ClearEmptyValues(ResourceTable* table) {
  // Clear any empty packages/types/entries, as remove_default_config_values_ may remove an entire
  // value set.
  CHECK(remove_default_config_values_)
      << __func__ << " should only be called when remove_default_config_values_ is set";

  for (auto& pkg : table->packages) {
    for (auto& type : pkg->types) {
      std::erase_if(type->entries, [](auto& entry) { return entry->values.empty(); });
    }
    std::erase_if(pkg->types, [](auto& type) { return type->entries.empty(); });
  }
  std::erase_if(table->packages, [](auto& package) { return package->types.empty(); });
}

}  // namespace aapt