gradle-master/subprojects/build-init/src/main/java/org/gradle/api/tasks/wrapper/GradleVersionResolver.java
/*
 * Copyright 2022 the original author or authors.
 *
 * 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 org.gradle.api.tasks.wrapper;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import org.gradle.api.GradleException;
import org.gradle.api.resources.TextResource;
import org.gradle.api.tasks.wrapper.internal.DefaultWrapperVersionsResources;
import org.gradle.util.GradleVersion;

import java.lang.reflect.Type;
import java.util.Map;

import static org.gradle.api.tasks.wrapper.internal.DefaultWrapperVersionsResources.LATEST;
import static org.gradle.api.tasks.wrapper.internal.DefaultWrapperVersionsResources.NIGHTLY;
import static org.gradle.api.tasks.wrapper.internal.DefaultWrapperVersionsResources.RELEASE_CANDIDATE;
import static org.gradle.api.tasks.wrapper.internal.DefaultWrapperVersionsResources.RELEASE_NIGHTLY;

class GradleVersionResolver {

    private TextResource latest;
    private TextResource releaseCandidate;
    private TextResource nightly;
    private TextResource releaseNightly;

    private GradleVersion gradleVersion;
    private String gradleVersionString = GradleVersion.current().getVersion();

    void setTextResources(TextResource latest, TextResource releaseCandidate, TextResource nightly, TextResource releaseNightly) {
        this.latest = latest;
        this.releaseCandidate = releaseCandidate;
        this.nightly = nightly;
        this.releaseNightly = releaseNightly;
    }

    String resolve(String version) {
        if (version == null) {
            return GradleVersion.current().getVersion();
        }
        switch (version) {
            case LATEST:
                return getVersion(latest.asString(), version);
            case NIGHTLY:
                return getVersion(nightly.asString(), version);
            case RELEASE_NIGHTLY:
                return getVersion(releaseNightly.asString(), version);
            case RELEASE_CANDIDATE:
                return getVersion(releaseCandidate.asString(), version);
            default:
                return version;
        }
    }

    static String getVersion(String json, String placeHolder) {
        Type type = new TypeToken<Map<String, String>>() {}.getType();
        Map<String, String> map = new Gson().fromJson(json, type);
        String version = map.get("version");
        if (version == null) {
            throw new GradleException("There is currently no version information available for '" + placeHolder + "'.");
        }
        return version;
    }

    static boolean isPlaceHolder(String version) {
        return DefaultWrapperVersionsResources.PLACE_HOLDERS.contains(version);
    }

    GradleVersion getGradleVersion() {
        if (gradleVersion == null) {
            gradleVersion = GradleVersion.version(resolve(gradleVersionString));
        }
        return gradleVersion;
    }

    void setGradleVersionString(String gradleVersionString) {
        if (!isPlaceHolder(gradleVersionString)) {
            this.gradleVersion = GradleVersion.version(gradleVersionString);
        }
        if (this.gradleVersionString != gradleVersionString) {
            this.gradleVersionString = gradleVersionString;
            this.gradleVersion = null;
        }
    }
}
