/*
 * Copyright 2022 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.
 */

package android.app.appsearch;

import android.annotation.IntDef;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.app.appsearch.annotation.CanIgnoreReturnValue;
import android.app.appsearch.util.BundleUtil;
import android.os.Bundle;
import android.util.ArrayMap;
import android.util.ArraySet;

import com.android.internal.util.Preconditions;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

/**
 * This class represents the specification logic for AppSearch. It can be used to set the filter and
 * settings of search a suggestions.
 *
 * @see AppSearchSession#searchSuggestion
 */
public final class SearchSuggestionSpec {
    static final String NAMESPACE_FIELD = "namespace";
    static final String SCHEMA_FIELD = "schema";
    static final String PROPERTY_FIELD = "property";
    static final String DOCUMENT_IDS_FIELD = "documentIds";
    static final String MAXIMUM_RESULT_COUNT_FIELD = "maximumResultCount";
    static final String RANKING_STRATEGY_FIELD = "rankingStrategy";
    private final Bundle mBundle;
    private final int mMaximumResultCount;

    /** @hide */
    public SearchSuggestionSpec(@NonNull Bundle bundle) {
        Objects.requireNonNull(bundle);
        mBundle = bundle;
        mMaximumResultCount = bundle.getInt(MAXIMUM_RESULT_COUNT_FIELD);
        Preconditions.checkArgument(
                mMaximumResultCount >= 1, "MaximumResultCount must be positive.");
    }

    /**
     * Ranking Strategy for {@link SearchSuggestionResult}.
     *
     * @hide
     */
    @IntDef(
            value = {
                SUGGESTION_RANKING_STRATEGY_NONE,
                SUGGESTION_RANKING_STRATEGY_DOCUMENT_COUNT,
                SUGGESTION_RANKING_STRATEGY_TERM_FREQUENCY,
            })
    @Retention(RetentionPolicy.SOURCE)
    public @interface SuggestionRankingStrategy {}

    /**
     * Ranked by the document count that contains the term.
     *
     * <p>Suppose the following document is in the index.
     *
     * <pre>Doc1 contains: term1 term2 term2 term2</pre>
     *
     * <pre>Doc2 contains: term1</pre>
     *
     * <p>Then, suppose that a search suggestion for "t" is issued with the DOCUMENT_COUNT, the
     * returned {@link SearchSuggestionResult}s will be: term1, term2. The term1 will have higher
     * score and appear in the results first.
     */
    public static final int SUGGESTION_RANKING_STRATEGY_DOCUMENT_COUNT = 0;
    /**
     * Ranked by the term appear frequency.
     *
     * <p>Suppose the following document is in the index.
     *
     * <pre>Doc1 contains: term1 term2 term2 term2</pre>
     *
     * <pre>Doc2 contains: term1</pre>
     *
     * <p>Then, suppose that a search suggestion for "t" is issued with the TERM_FREQUENCY, the
     * returned {@link SearchSuggestionResult}s will be: term2, term1. The term2 will have higher
     * score and appear in the results first.
     */
    public static final int SUGGESTION_RANKING_STRATEGY_TERM_FREQUENCY = 1;

    /** No Ranking, results are returned in arbitrary order. */
    public static final int SUGGESTION_RANKING_STRATEGY_NONE = 2;

    /**
     * Returns the {@link Bundle} populated by this builder.
     *
     * @hide
     */
    @NonNull
    public Bundle getBundle() {
        return mBundle;
    }

    /**
     * Returns the maximum number of wanted suggestion that will be returned in the result object.
     */
    public int getMaximumResultCount() {
        return mMaximumResultCount;
    }

    /**
     * Returns the list of namespaces to search over.
     *
     * <p>If empty, will search over all namespaces.
     */
    @NonNull
    public List<String> getFilterNamespaces() {
        List<String> namespaces = mBundle.getStringArrayList(NAMESPACE_FIELD);
        if (namespaces == null) {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(namespaces);
    }

    /** Returns the ranking strategy. */
    @SuggestionRankingStrategy
    public int getRankingStrategy() {
        return mBundle.getInt(RANKING_STRATEGY_FIELD);
    }

    /**
     * Returns the list of schema to search the suggestion over.
     *
     * <p>If empty, will search over all schemas.
     */
    @NonNull
    public List<String> getFilterSchemas() {
        List<String> schemaTypes = mBundle.getStringArrayList(SCHEMA_FIELD);
        if (schemaTypes == null) {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(schemaTypes);
    }

    /**
     * Returns the map of schema and target properties to search over.
     *
     * <p>The keys of the returned map are schema types, and the values are the target property path
     * in that schema to search over.
     *
     * <p>If {@link Builder#addFilterPropertyPaths} was never called, returns an empty map. In this
     * case AppSearch will search over all schemas and properties.
     *
     * <p>Calling this function repeatedly is inefficient. Prefer to retain the Map returned by this
     * function, rather than calling it multiple times.
     *
     * @hide
     */
    // TODO(b/228240987) migrate this API when we support property restrict for multiple terms
    @NonNull
    public Map<String, List<String>> getFilterProperties() {
        Bundle typePropertyPathsBundle = Objects.requireNonNull(mBundle.getBundle(PROPERTY_FIELD));
        Set<String> schemas = typePropertyPathsBundle.keySet();
        Map<String, List<String>> typePropertyPathsMap = new ArrayMap<>(schemas.size());
        for (String schema : schemas) {
            typePropertyPathsMap.put(
                    schema,
                    Objects.requireNonNull(typePropertyPathsBundle.getStringArrayList(schema)));
        }
        return typePropertyPathsMap;
    }

    /**
     * Returns the map of namespace and target document ids to search over.
     *
     * <p>The keys of the returned map are namespaces, and the values are the target document ids in
     * that namespace to search over.
     *
     * <p>If {@link Builder#addFilterDocumentIds} was never called, returns an empty map. In this
     * case AppSearch will search over all namespace and document ids.
     *
     * <p>Calling this function repeatedly is inefficient. Prefer to retain the Map returned by this
     * function, rather than calling it multiple times.
     */
    @NonNull
    public Map<String, List<String>> getFilterDocumentIds() {
        Bundle documentIdsBundle = Objects.requireNonNull(mBundle.getBundle(DOCUMENT_IDS_FIELD));
        Set<String> namespaces = documentIdsBundle.keySet();
        Map<String, List<String>> documentIdsMap = new ArrayMap<>(namespaces.size());
        for (String namespace : namespaces) {
            documentIdsMap.put(
                    namespace,
                    Objects.requireNonNull(documentIdsBundle.getStringArrayList(namespace)));
        }
        return documentIdsMap;
    }

    /** Builder for {@link SearchSuggestionSpec objects}. */
    public static final class Builder {
        private ArrayList<String> mNamespaces = new ArrayList<>();
        private ArrayList<String> mSchemas = new ArrayList<>();
        private Bundle mTypePropertyFilters = new Bundle();
        private Bundle mDocumentIds = new Bundle();
        private final int mTotalResultCount;

        @SuggestionRankingStrategy
        private int mRankingStrategy = SUGGESTION_RANKING_STRATEGY_DOCUMENT_COUNT;

        private boolean mBuilt = false;

        /**
         * Creates an {@link SearchSuggestionSpec.Builder} object.
         *
         * @param maximumResultCount Sets the maximum number of suggestion in the returned object.
         */
        public Builder(@IntRange(from = 1) int maximumResultCount) {
            Preconditions.checkArgument(
                    maximumResultCount >= 1, "maximumResultCount must be positive.");
            mTotalResultCount = maximumResultCount;
        }

        /**
         * Adds a namespace filter to {@link SearchSuggestionSpec} Entry. Only search for
         * suggestions that has documents under the specified namespaces.
         *
         * <p>If unset, the query will search over all namespaces.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterNamespaces(@NonNull String... namespaces) {
            Objects.requireNonNull(namespaces);
            resetIfBuilt();
            return addFilterNamespaces(Arrays.asList(namespaces));
        }

        /**
         * Adds a namespace filter to {@link SearchSuggestionSpec} Entry. Only search for
         * suggestions that has documents under the specified namespaces.
         *
         * <p>If unset, the query will search over all namespaces.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterNamespaces(@NonNull Collection<String> namespaces) {
            Objects.requireNonNull(namespaces);
            resetIfBuilt();
            mNamespaces.addAll(namespaces);
            return this;
        }

        /**
         * Sets ranking strategy for suggestion results.
         *
         * <p>The default value {@link #SUGGESTION_RANKING_STRATEGY_DOCUMENT_COUNT} will be used if
         * this method is never called.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder setRankingStrategy(@SuggestionRankingStrategy int rankingStrategy) {
            Preconditions.checkArgumentInRange(
                    rankingStrategy,
                    SUGGESTION_RANKING_STRATEGY_DOCUMENT_COUNT,
                    SUGGESTION_RANKING_STRATEGY_NONE,
                    "Suggestion ranking strategy");
            resetIfBuilt();
            mRankingStrategy = rankingStrategy;
            return this;
        }

        /**
         * Adds a schema filter to {@link SearchSuggestionSpec} Entry. Only search for suggestions
         * that has documents under the specified schema.
         *
         * <p>If unset, the query will search over all schema.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterSchemas(@NonNull String... schemaTypes) {
            Objects.requireNonNull(schemaTypes);
            resetIfBuilt();
            return addFilterSchemas(Arrays.asList(schemaTypes));
        }

        /**
         * Adds a schema filter to {@link SearchSuggestionSpec} Entry. Only search for suggestions
         * that has documents under the specified schema.
         *
         * <p>If unset, the query will search over all schema.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterSchemas(@NonNull Collection<String> schemaTypes) {
            Objects.requireNonNull(schemaTypes);
            resetIfBuilt();
            mSchemas.addAll(schemaTypes);
            return this;
        }

        /**
         * Adds property paths for the specified type to the property filter of {@link
         * SearchSuggestionSpec} Entry. Only search for suggestions that has content under the
         * specified property. If property paths are added for a type, then only the properties
         * referred to will be retrieved for results of that type.
         *
         * <p>If a property path that is specified isn't present in a result, it will be ignored for
         * that result. Property paths cannot be null.
         *
         * <p>If no property paths are added for a particular type, then all properties of results
         * of that type will be retrieved.
         *
         * <p>Example properties: 'body', 'sender.name', 'sender.emailaddress', etc.
         *
         * @param schema the {@link AppSearchSchema} that contains the target properties
         * @param propertyPaths The String version of {@link PropertyPath}. A dot-delimited sequence
         *     of property names indicating which property in the document these snippets correspond
         *     to.
         * @hide
         */
        // TODO(b/228240987) migrate this API when we support property restrict for multiple terms
        @NonNull
        public Builder addFilterProperties(
                @NonNull String schema, @NonNull Collection<String> propertyPaths) {
            Objects.requireNonNull(schema);
            Objects.requireNonNull(propertyPaths);
            resetIfBuilt();
            ArrayList<String> propertyPathsArrayList = new ArrayList<>(propertyPaths.size());
            for (String propertyPath : propertyPaths) {
                Objects.requireNonNull(propertyPath);
                propertyPathsArrayList.add(propertyPath);
            }
            mTypePropertyFilters.putStringArrayList(schema, propertyPathsArrayList);
            return this;
        }

        /**
         * Adds property paths for the specified type to the property filter of {@link
         * SearchSuggestionSpec} Entry. Only search for suggestions that has content under the
         * specified property. If property paths are added for a type, then only the properties
         * referred to will be retrieved for results of that type.
         *
         * <p>If a property path that is specified isn't present in a result, it will be ignored for
         * that result. Property paths cannot be null.
         *
         * <p>If no property paths are added for a particular type, then all properties of results
         * of that type will be retrieved.
         *
         * @param schema the {@link AppSearchSchema} that contains the target properties
         * @param propertyPaths The {@link PropertyPath} to search suggestion over
         * @hide
         */
        // TODO(b/228240987) migrate this API when we support property restrict for multiple terms
        @NonNull
        public Builder addFilterPropertyPaths(
                @NonNull String schema, @NonNull Collection<PropertyPath> propertyPaths) {
            Objects.requireNonNull(schema);
            Objects.requireNonNull(propertyPaths);
            ArrayList<String> propertyPathsArrayList = new ArrayList<>(propertyPaths.size());
            for (PropertyPath propertyPath : propertyPaths) {
                propertyPathsArrayList.add(propertyPath.toString());
            }
            return addFilterProperties(schema, propertyPathsArrayList);
        }

        /**
         * Adds a document ID filter to {@link SearchSuggestionSpec} Entry. Only search for
         * suggestions in the given specified documents.
         *
         * <p>If unset, the query will search over all documents.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterDocumentIds(
                @NonNull String namespace, @NonNull String... documentIds) {
            Objects.requireNonNull(namespace);
            Objects.requireNonNull(documentIds);
            resetIfBuilt();
            return addFilterDocumentIds(namespace, Arrays.asList(documentIds));
        }

        /**
         * Adds a document ID filter to {@link SearchSuggestionSpec} Entry. Only search for
         * suggestions in the given specified documents.
         *
         * <p>If unset, the query will search over all documents.
         */
        @CanIgnoreReturnValue
        @NonNull
        public Builder addFilterDocumentIds(
                @NonNull String namespace, @NonNull Collection<String> documentIds) {
            Objects.requireNonNull(namespace);
            Objects.requireNonNull(documentIds);
            resetIfBuilt();
            ArrayList<String> documentIdList = new ArrayList<>(documentIds.size());
            for (String documentId : documentIds) {
                documentIdList.add(Objects.requireNonNull(documentId));
            }
            mDocumentIds.putStringArrayList(namespace, documentIdList);
            return this;
        }

        /** Constructs a new {@link SearchSpec} from the contents of this builder. */
        @NonNull
        public SearchSuggestionSpec build() {
            Bundle bundle = new Bundle();
            if (!mSchemas.isEmpty()) {
                Set<String> schemaFilter = new ArraySet<>(mSchemas);
                for (String schema : mTypePropertyFilters.keySet()) {
                    if (!schemaFilter.contains(schema)) {
                        throw new IllegalStateException(
                                "The schema: "
                                        + schema
                                        + " exists in the property filter but "
                                        + "doesn't exist in the schema filter.");
                    }
                }
            }
            if (!mNamespaces.isEmpty()) {
                Set<String> namespaceFilter = new ArraySet<>(mNamespaces);
                for (String namespace : mDocumentIds.keySet()) {
                    if (!namespaceFilter.contains(namespace)) {
                        throw new IllegalStateException(
                                "The namespace: "
                                        + namespace
                                        + " exists in the document id "
                                        + "filter but doesn't exist in the namespace filter.");
                    }
                }
            }
            bundle.putStringArrayList(NAMESPACE_FIELD, mNamespaces);
            bundle.putStringArrayList(SCHEMA_FIELD, mSchemas);
            bundle.putBundle(PROPERTY_FIELD, mTypePropertyFilters);
            bundle.putBundle(DOCUMENT_IDS_FIELD, mDocumentIds);
            bundle.putInt(MAXIMUM_RESULT_COUNT_FIELD, mTotalResultCount);
            bundle.putInt(RANKING_STRATEGY_FIELD, mRankingStrategy);
            mBuilt = true;
            return new SearchSuggestionSpec(bundle);
        }

        private void resetIfBuilt() {
            if (mBuilt) {
                mNamespaces = new ArrayList<>(mNamespaces);
                mSchemas = new ArrayList<>(mSchemas);
                mTypePropertyFilters = BundleUtil.deepCopy(mTypePropertyFilters);
                mDocumentIds = BundleUtil.deepCopy(mDocumentIds);
                mBuilt = false;
            }
        }
    }
}