Java tutorial
/* * Copyright (C) 2015 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 com.android.tools.idea.templates; import com.google.common.base.Objects; import com.google.common.collect.ImmutableMap; import com.google.common.collect.Iterables; import com.google.common.collect.Maps; import com.google.common.collect.Sets; import com.intellij.openapi.util.text.StringUtil; import org.jetbrains.annotations.NotNull; import org.jetbrains.annotations.Nullable; import java.util.HashMap; import java.util.Map; import java.util.Set; /** * Class which handles setting up the relationships between a bunch of {@link Parameter}s and then * resolves them. */ public final class ParameterValueResolver { @NotNull private static final Deduplicator DO_NOTHING_DEDUPLICATOR = new Deduplicator() { @Nullable @Override public String deduplicate(@NotNull Parameter parameter, @Nullable String value) { return value; } }; @NotNull private final Set<Parameter> myComputedParameters = Sets.newHashSet(); @NotNull private final Set<Parameter> myStaticParameters = Sets.newHashSet(); @NotNull private final Deduplicator myDeduplicator; @NotNull private final StringEvaluator myStringEvaluator = new StringEvaluator(); @NotNull private final Map<Parameter, Object> myUserValues; @NotNull private final Map<String, Object> myAdditionalValues; /** * @see #resolve(Iterable, Map, Map, Deduplicator) */ @NotNull public static Map<Parameter, Object> resolve(@NotNull Iterable<Parameter> parameters, @NotNull Map<Parameter, Object> userValues, @NotNull Map<String, Object> additionalValues) throws CircularParameterDependencyException { return resolve(parameters, userValues, additionalValues, DO_NOTHING_DEDUPLICATOR); } /** * Resolve input parameters, returning a mapping of parameters to their resolved values. * * @param parameters parameters to resolve * @param userValues parameter values supplied by the user. * @param additionalValues parameters that were not declared by the template but are instead a part of our "runtime" * @param deduplicator a function that ensures uniqueness of the parameter value */ @NotNull public static Map<Parameter, Object> resolve(@NotNull Iterable<Parameter> parameters, @NotNull Map<Parameter, Object> userValues, @NotNull Map<String, Object> additionalValues, @NotNull Deduplicator deduplicator) throws CircularParameterDependencyException { ParameterValueResolver resolver = new ParameterValueResolver(parameters, userValues, additionalValues, deduplicator); return resolver.resolve(); } private ParameterValueResolver(@NotNull Iterable<Parameter> parameters, @NotNull Map<Parameter, Object> userValues, @NotNull Map<String, Object> additionalValues, @NotNull Deduplicator deduplicator) { myUserValues = userValues; myAdditionalValues = additionalValues; for (Parameter parameter : parameters) { if (parameter != null && !StringUtil.isEmptyOrSpaces(parameter.id)) { if (!StringUtil.isEmptyOrSpaces(parameter.suggest) && !userValues.containsKey(parameter)) { myComputedParameters.add(parameter); } else { myStaticParameters.add(parameter); } } } myDeduplicator = deduplicator; } @Nullable private static Object decodeInitialValue(@NotNull Parameter input, @Nullable String initial) { if (initial != null && input.type == Parameter.Type.BOOLEAN) { return Boolean.valueOf(initial); } else { return initial; } } /** * Returns a map of parameters to their resolved values. */ @NotNull public Map<Parameter, Object> resolve() throws CircularParameterDependencyException { Map<String, Object> staticValues = getStaticParameterValues(myUserValues, myAdditionalValues); Map<String, Object> computedValues = computeParameterValues(staticValues); HashMap<Parameter, Object> allValues = Maps .newHashMapWithExpectedSize(computedValues.size() + staticValues.size()); for (Parameter parameter : Iterables.concat(myStaticParameters, myComputedParameters)) { allValues.put(parameter, computedValues.get(parameter.id)); } return allValues; } @Nullable private Object computeParameterValue(@NotNull Parameter computedParameter, @NotNull Map<String, Object> currentValues) { String suggest = computedParameter.suggest; assert !StringUtil.isEmptyOrSpaces(suggest); String value = myStringEvaluator.evaluate(suggest, currentValues); value = myDeduplicator.deduplicate(computedParameter, value); return decodeInitialValue(computedParameter, value); } @NotNull private Map<String, Object> getStaticParameterValues(@NotNull Map<Parameter, Object> userValues, @NotNull Map<String, Object> additionalValues) { final Map<String, Object> knownValues = Maps .newHashMapWithExpectedSize(myStaticParameters.size() + additionalValues.size()); knownValues.putAll(additionalValues); for (Parameter parameter : myStaticParameters) { Object value; if (userValues.containsKey(parameter)) { value = userValues.get(parameter); } else if (additionalValues.containsKey(parameter.id)) { value = additionalValues.get(parameter.id); } else { String initial = parameter.initial; value = decodeInitialValue(parameter, initial); } knownValues.put(parameter.id, value); } return knownValues; } /** * Computes values of the parameters with non-static default values. * * These parameters may depend on other computable parameters. We do not have that information * (expressions are evaluated with FreeMarker), so we keep reevaluating the parameter values until * they stabilize. */ @NotNull private Map<String, Object> computeParameterValues(@NotNull Map<String, Object> staticValues) throws CircularParameterDependencyException { Map<String, Object> computedValues = Maps .newHashMapWithExpectedSize(myComputedParameters.size() + staticValues.size()); computedValues.putAll(staticValues); for (Parameter parameter : myComputedParameters) { computedValues.put(parameter.id, ""); } // Limit the number of iterations before we recognize there's circular dependency. // The maximum depth of the parameter dependency tree would be a number of parameters, // hence this is our "worst case" number of iterations (note we'll need +1 iteration // to check the value is stable) we would need to compute the values. // Update: it turns out we do have circular dependencies which in most cases turn into // a stable situation, but worst case is 2 times the number of iterations since a value // can also be modified because of a "unique" qualifier. final int maxIterations = 2 * myComputedParameters.size(); Map<String, Object> updatedValues = ImmutableMap.of(); for (int i = 0; i <= maxIterations; i++) { updatedValues = computeUpdatedValues(computedValues); if (updatedValues.isEmpty()) { return computedValues; } else { computedValues.putAll(updatedValues); } } throw new CircularParameterDependencyException(updatedValues.keySet()); } @NotNull private Map<String, Object> computeUpdatedValues(@NotNull Map<String, Object> values) { Map<String, Object> updatedValues = Maps.newHashMapWithExpectedSize(myComputedParameters.size()); for (Parameter computedParameter : myComputedParameters) { Object value = computeParameterValue(computedParameter, values); String id = computedParameter.id; if (!Objects.equal(values.get(id), value)) { updatedValues.put(id, value); } } return updatedValues; } public interface Deduplicator { @Nullable String deduplicate(@NotNull Parameter parameter, @Nullable String value); } }