Add scheduleNextRelease gradle task

buildSrc/src/main/java/org/springframework/gradle/github/milestones/GitHubMilestoneApi.java

@@ -18,16 +18,24 @@ package org.springframework.gradle.github.milestones;
 
 import java.io.IOException;
 import java.time.Instant;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.ZoneOffset;
 import java.util.List;
 import java.util.Optional;
+import java.util.TimeZone;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import com.google.common.reflect.TypeToken;
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import okhttp3.Interceptor;
+import okhttp3.MediaType;
 import okhttp3.OkHttpClient;
 import okhttp3.Request;
+import okhttp3.RequestBody;
 import okhttp3.Response;
 
 import org.springframework.gradle.github.RepositoryRef;
@@ -37,7 +45,10 @@ public class GitHubMilestoneApi {
 
 	private OkHttpClient client;
 
-	private Gson gson = new Gson();
+	private final Gson gson = new GsonBuilder()
+			.registerTypeAdapter(LocalDate.class, new LocalDateAdapter().nullSafe())
+			.registerTypeAdapter(LocalDateTime.class, new LocalDateTimeAdapter().nullSafe())
+			.create();
 
 	public GitHubMilestoneApi() {
 		this.client = new OkHttpClient.Builder().build();
@@ -54,26 +65,30 @@ public class GitHubMilestoneApi {
 	}
 
 	public long findMilestoneNumberByTitle(RepositoryRef repositoryRef, String milestoneTitle) {
+		List<Milestone> milestones = this.getMilestones(repositoryRef);
+		for (Milestone milestone : milestones) {
+			if (milestoneTitle.equals(milestone.getTitle())) {
+				return milestone.getNumber();
+			}
+		}
+		if (milestones.size() <= 100) {
+			throw new RuntimeException("Could not find open milestone with title " + milestoneTitle + " for repository " + repositoryRef + " Got " + milestones);
+		}
+		throw new RuntimeException("It is possible there are too many open milestones (only 100 are supported). Could not find open milestone with title " + milestoneTitle + " for repository " + repositoryRef + " Got " + milestones);
+	}
+
+	public List<Milestone> getMilestones(RepositoryRef repositoryRef) {
 		String url = this.baseUrl + "/repos/" + repositoryRef.getOwner() + "/" + repositoryRef.getName() + "/milestones?per_page=100";
 		Request request = new Request.Builder().get().url(url)
 				.build();
 		try {
 			Response response = this.client.newCall(request).execute();
 			if (!response.isSuccessful()) {
-				throw new RuntimeException("Could not find milestone with title " + milestoneTitle + " for repository " + repositoryRef + ". Response " + response);
+				throw new RuntimeException("Could not retrieve milestones for repository " + repositoryRef + ". Response " + response);
 			}
-			List<Milestone> milestones = this.gson.fromJson(response.body().charStream(), new TypeToken<List<Milestone>>(){}.getType());
-			for (Milestone milestone : milestones) {
-				if (milestoneTitle.equals(milestone.getTitle())) {
-					return milestone.getNumber();
-				}
-			}
-			if (milestones.size() <= 100) {
-				throw new RuntimeException("Could not find open milestone with title " + milestoneTitle + " for repository " + repositoryRef + " Got " + milestones);
-			}
-			throw new RuntimeException("It is possible there are too many open milestones open (only 100 are supported). Could not find open milestone with title " + milestoneTitle + " for repository " + repositoryRef + " Got " + milestones);
+			return this.gson.fromJson(response.body().charStream(), new TypeToken<List<Milestone>>(){}.getType());
 		} catch (IOException e) {
-			throw new RuntimeException("Could not find open milestone with title " + milestoneTitle + " for repository " + repositoryRef, e);
+			throw new RuntimeException("Could not retrieve milestones for repository " + repositoryRef, e);
 		}
 	}
 
@@ -115,8 +130,8 @@ public class GitHubMilestoneApi {
 					}.getType());
 			for (Milestone milestone : milestones) {
 				if (milestoneTitle.equals(milestone.getTitle())) {
-					Instant now = Instant.now();
-					return milestone.getDueOn() != null && now.isAfter(milestone.getDueOn().toInstant());
+					LocalDate today = LocalDate.now();
+					return milestone.getDueOn() != null && today.compareTo(milestone.getDueOn().toLocalDate()) >= 0;
 				}
 			}
 			if (milestones.size() <= 100) {
@@ -215,10 +230,28 @@ public class GitHubMilestoneApi {
 		}
 	}
 
-//	public boolean isOpenIssuesForMilestoneName(String owner, String repository, String milestoneName) {
-//
-//	}
-
+	/**
+	 * Create a milestone.
+	 *
+	 * @param repository The repository owner/name
+	 * @param milestone The milestone containing a title and due date
+	 */
+	public void createMilestone(RepositoryRef repository, Milestone milestone) {
+		String url = this.baseUrl + "/repos/" + repository.getOwner() + "/" + repository.getName() + "/milestones";
+		String json = this.gson.toJson(milestone);
+		RequestBody body = RequestBody.create(MediaType.parse("application/json"), json);
+		Request request = new Request.Builder().url(url).post(body).build();
+		try {
+			Response response = this.client.newCall(request).execute();
+			if (!response.isSuccessful()) {
+				throw new RuntimeException(String.format("Could not create milestone %s for repository %s/%s. Got response %s",
+						milestone.getTitle(), repository.getOwner(), repository.getName(), response));
+			}
+		} catch (IOException ex) {
+			throw new RuntimeException(String.format("Could not create release %s for repository %s/%s",
+					milestone.getTitle(), repository.getOwner(), repository.getName()), ex);
+		}
+	}
 
 	private static class AuthorizationInterceptor implements Interceptor {
 

buildSrc/src/main/java/org/springframework/gradle/github/milestones/GitHubMilestonePlugin.java

@@ -21,6 +21,8 @@ import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.TaskProvider;
 
+import org.springframework.gradle.github.RepositoryRef;
+
 public class GitHubMilestonePlugin implements Plugin<Project> {
 	@Override
 	public void apply(Project project) {
@@ -68,5 +70,13 @@ public class GitHubMilestonePlugin implements Plugin<Project> {
 						}
 					}
 				});
+		project.getTasks().register("scheduleNextRelease", ScheduleNextReleaseTask.class, (scheduleNextRelease) -> {
+			scheduleNextRelease.doNotTrackState("API call to GitHub needs to check for new milestones every time");
+			scheduleNextRelease.setGroup("Release");
+			scheduleNextRelease.setDescription("Schedule the next release (even months only) or release train (series of milestones starting in January or July) based on the current version");
+
+			scheduleNextRelease.setVersion((String) project.findProperty("nextVersion"));
+			scheduleNextRelease.setGitHubAccessToken((String) project.findProperty("gitHubAccessToken"));
+		});
 	}
 }

buildSrc/src/main/java/org/springframework/gradle/github/milestones/LocalDateAdapter.java

@@ -0,0 +1,23 @@
+package org.springframework.gradle.github.milestones;
+
+import java.io.IOException;
+import java.time.LocalDate;
+
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+/**
+ * @author Steve Riesenberg
+ */
+class LocalDateAdapter extends TypeAdapter<LocalDate> {
+	@Override
+	public void write(JsonWriter jsonWriter, LocalDate localDate) throws IOException {
+		jsonWriter.value(localDate.toString());
+	}
+
+	@Override
+	public LocalDate read(JsonReader jsonReader) throws IOException {
+		return LocalDate.parse(jsonReader.nextString());
+	}
+}

buildSrc/src/main/java/org/springframework/gradle/github/milestones/LocalDateTimeAdapter.java

@@ -0,0 +1,25 @@
+package org.springframework.gradle.github.milestones;
+
+import java.io.IOException;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+/**
+ * @author Steve Riesenberg
+ */
+class LocalDateTimeAdapter extends TypeAdapter<LocalDateTime> {
+	@Override
+	public void write(JsonWriter jsonWriter, LocalDateTime localDateTime) throws IOException {
+		jsonWriter.value(localDateTime.atOffset(ZoneOffset.UTC).format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
+	}
+
+	@Override
+	public LocalDateTime read(JsonReader jsonReader) throws IOException {
+		return LocalDateTime.parse(jsonReader.nextString(), DateTimeFormatter.ISO_ZONED_DATE_TIME);
+	}
+}

buildSrc/src/main/java/org/springframework/gradle/github/milestones/Milestone.java

@@ -18,15 +18,19 @@ package org.springframework.gradle.github.milestones;
 
 import com.google.gson.annotations.SerializedName;
 
+import java.time.LocalDateTime;
 import java.util.Date;
 
+/**
+ * @author Steve Riesenberg
+ */
 public class Milestone {
 	private String title;
 
-	private long number;
+	private Long number;
 
 	@SerializedName("due_on")
-	private Date dueOn;
+	private LocalDateTime dueOn;
 
 	public String getTitle() {
 		return title;
@@ -36,19 +40,19 @@ public class Milestone {
 		this.title = title;
 	}
 
-	public long getNumber() {
+	public Long getNumber() {
 		return number;
 	}
 
-	public void setNumber(long number) {
+	public void setNumber(Long number) {
 		this.number = number;
 	}
 
-	public Date getDueOn() {
+	public LocalDateTime getDueOn() {
 		return dueOn;
 	}
 
-	public void setDueOn(Date dueOn) {
+	public void setDueOn(LocalDateTime dueOn) {
 		this.dueOn = dueOn;
 	}
 
@@ -57,7 +61,7 @@ public class Milestone {
 		return "Milestone{" +
 				"title='" + title + '\'' +
 				", number='" + number + '\'' +
-				", dueOn='" + dueOn +
+				", dueOn='" + dueOn + '\'' +
 				'}';
 	}
 }

buildSrc/src/main/java/org/springframework/gradle/github/milestones/ScheduleNextReleaseTask.java

@@ -0,0 +1,142 @@
+/*
+ * Copyright 2002-2022 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
+ *
+ *      https://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.springframework.gradle.github.milestones;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+
+import org.gradle.api.DefaultTask;
+import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.TaskAction;
+
+import org.springframework.gradle.github.RepositoryRef;
+
+/**
+ * @author Steve Riesenberg
+ */
+public class ScheduleNextReleaseTask extends DefaultTask {
+	@Input
+	private RepositoryRef repository = new RepositoryRef();
+
+	@Input
+	private String gitHubAccessToken;
+
+	@Input
+	private String version;
+
+	@Input
+	private Integer weekOfMonth;
+
+	@Input
+	private Integer dayOfWeek;
+
+	@TaskAction
+	public void scheduleNextRelease() {
+		GitHubMilestoneApi gitHubMilestoneApi = new GitHubMilestoneApi(this.gitHubAccessToken);
+		String nextReleaseMilestone = gitHubMilestoneApi.getNextReleaseMilestone(this.repository, this.version);
+
+		// If the next release contains a dash (e.g. 5.6.0-RC1), it is already scheduled
+		if (nextReleaseMilestone.contains("-")) {
+			return;
+		}
+
+		// Check to see if a scheduled GA version already exists
+		boolean hasExistingMilestone = gitHubMilestoneApi.getMilestones(this.repository).stream()
+				.anyMatch(milestone -> nextReleaseMilestone.equals(milestone.getTitle()));
+		if (hasExistingMilestone) {
+			return;
+		}
+
+		// Next milestone is either a patch version or minor version
+		// Note: Major versions will be handled like minor and get a release
+		// train which can be manually updated to match the desired schedule.
+		if (nextReleaseMilestone.endsWith(".0")) {
+			// Create M1, M2, M3, RC1 and GA milestones for release train
+			getReleaseTrain(nextReleaseMilestone).getTrainDates().forEach((milestoneTitle, dueOn) -> {
+				Milestone milestone = new Milestone();
+				milestone.setTitle(milestoneTitle);
+				// Note: GitHub seems to store full date/time as UTC then displays
+				// as a date (no time) in your timezone, which means the date will
+				// not always be the same date as we intend.
+				// Using 12pm/noon UTC allows GitHub to schedule and display the
+				// correct date.
+				milestone.setDueOn(dueOn.atTime(LocalTime.NOON));
+				gitHubMilestoneApi.createMilestone(this.repository, milestone);
+			});
+		} else {
+			// Create GA milestone for patch release on the next even month
+			LocalDate startDate = LocalDate.now();
+			LocalDate dueOn = getReleaseTrain(nextReleaseMilestone).getNextReleaseDate(startDate);
+			Milestone milestone = new Milestone();
+			milestone.setTitle(nextReleaseMilestone);
+			milestone.setDueOn(dueOn.atTime(LocalTime.NOON));
+			gitHubMilestoneApi.createMilestone(this.repository, milestone);
+		}
+	}
+
+	private SpringReleaseTrain getReleaseTrain(String nextReleaseMilestone) {
+		SpringReleaseTrainSpec releaseTrainSpec =
+				SpringReleaseTrainSpec.builder()
+						.nextTrain()
+						.version(nextReleaseMilestone)
+						.weekOfMonth(this.weekOfMonth)
+						.dayOfWeek(this.dayOfWeek)
+						.build();
+
+		return new SpringReleaseTrain(releaseTrainSpec);
+	}
+
+	public RepositoryRef getRepository() {
+		return this.repository;
+	}
+
+	public void setRepository(RepositoryRef repository) {
+		this.repository = repository;
+	}
+
+	public String getGitHubAccessToken() {
+		return this.gitHubAccessToken;
+	}
+
+	public void setGitHubAccessToken(String gitHubAccessToken) {
+		this.gitHubAccessToken = gitHubAccessToken;
+	}
+
+	public String getVersion() {
+		return this.version;
+	}
+
+	public void setVersion(String version) {
+		this.version = version;
+	}
+
+	public Integer getWeekOfMonth() {
+		return weekOfMonth;
+	}
+
+	public void setWeekOfMonth(Integer weekOfMonth) {
+		this.weekOfMonth = weekOfMonth;
+	}
+
+	public Integer getDayOfWeek() {
+		return dayOfWeek;
+	}
+
+	public void setDayOfWeek(Integer dayOfWeek) {
+		this.dayOfWeek = dayOfWeek;
+	}
+}

buildSrc/src/main/java/org/springframework/gradle/github/milestones/SpringReleaseTrain.java

@@ -0,0 +1,134 @@
+/*
+ * Copyright 2002-2022 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
+ *
+ *      https://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.springframework.gradle.github.milestones;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.Month;
+import java.time.Year;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Spring release train generator based on rules contained in a specification.
+ * <p>
+ * The rules are:
+ * <ol>
+ *     <li>Train 1 (January-May) or 2 (July-November)</li>
+ *     <li>Version number (e.g. 0.1.2, 1.0.0, etc.)</li>
+ *     <li>Week of month (1st, 2nd, 3rd, 4th)</li>
+ *     <li>Day of week (Monday-Friday)</li>
+ *     <li>Year (e.g. 2020, 2021, etc.)</li>
+ * </ol>
+ *
+ * The release train generated will contain M1, M2, M3, RC1 and GA versions
+ * mapped to their respective dates in the train.
+ *
+ * @author Steve Riesenberg
+ */
+public final class SpringReleaseTrain {
+	private final SpringReleaseTrainSpec releaseTrainSpec;
+
+	public SpringReleaseTrain(SpringReleaseTrainSpec releaseTrainSpec) {
+		this.releaseTrainSpec = releaseTrainSpec;
+	}
+
+	/**
+	 * Calculate release train dates based on the release train specification.
+	 *
+	 * @return A mapping of release milestones to scheduled release dates
+	 */
+	public Map<String, LocalDate> getTrainDates() {
+		Map<String, LocalDate> releaseDates = new LinkedHashMap<>();
+		switch (this.releaseTrainSpec.getTrain()) {
+			case ONE:
+				addTrainDate(releaseDates, "M1", Month.JANUARY);
+				addTrainDate(releaseDates, "M2", Month.FEBRUARY);
+				addTrainDate(releaseDates, "M3", Month.MARCH);
+				addTrainDate(releaseDates, "RC1", Month.APRIL);
+				addTrainDate(releaseDates, null, Month.MAY);
+				break;
+			case TWO:
+				addTrainDate(releaseDates, "M1", Month.JULY);
+				addTrainDate(releaseDates, "M2", Month.AUGUST);
+				addTrainDate(releaseDates, "M3", Month.SEPTEMBER);
+				addTrainDate(releaseDates, "RC1", Month.OCTOBER);
+				addTrainDate(releaseDates, null, Month.NOVEMBER);
+				break;
+		}
+
+		return releaseDates;
+	}
+
+	/**
+	 * Determine if a given date matches the due date of given version.
+	 *
+	 * @param version The version number (e.g. 5.6.0-M1, 5.6.0, etc.)
+	 * @param expectedDate The expected date
+	 * @return true if the given date matches the due date of the given version, false otherwise
+	 */
+	public boolean isTrainDate(String version, LocalDate expectedDate) {
+		return expectedDate.isEqual(getTrainDates().get(version));
+	}
+
+	/**
+	 * Calculate the next release date following the given date.
+	 * <p>
+	 * The next release date is always on an even month so that a patch release
+	 * is the month after the GA version of a release train. This method does
+	 * not consider the year of the release train, only the given start date.
+	 *
+	 * @param startDate The start date
+	 * @return The next release date following the given date
+	 */
+	public LocalDate getNextReleaseDate(LocalDate startDate) {
+		LocalDate trainDate;
+		LocalDate currentDate = startDate;
+		do {
+			trainDate = calculateReleaseDate(
+					Year.of(currentDate.getYear()),
+					currentDate.getMonth(),
+					this.releaseTrainSpec.getDayOfWeek().getDayOfWeek(),
+					this.releaseTrainSpec.getWeekOfMonth().getDayOffset()
+			);
+			currentDate = currentDate.plusMonths(1);
+		} while (!trainDate.isAfter(startDate) || trainDate.getMonthValue() % 2 != 0);
+
+		return trainDate;
+	}
+
+	private void addTrainDate(Map<String, LocalDate> releaseDates, String milestone, Month month) {
+		LocalDate releaseDate = calculateReleaseDate(
+				this.releaseTrainSpec.getYear(),
+				month,
+				this.releaseTrainSpec.getDayOfWeek().getDayOfWeek(),
+				this.releaseTrainSpec.getWeekOfMonth().getDayOffset()
+		);
+		String suffix = (milestone == null) ? "" : "-" + milestone;
+		releaseDates.put(this.releaseTrainSpec.getVersion() + suffix, releaseDate);
+	}
+
+	private static LocalDate calculateReleaseDate(Year year, Month month, DayOfWeek dayOfWeek, int dayOffset) {
+		LocalDate firstDayOfMonth = year.atMonth(month).atDay(1);
+		int dayOfWeekOffset = dayOfWeek.getValue() - firstDayOfMonth.getDayOfWeek().getValue();
+		if (dayOfWeekOffset < 0) {
+			dayOfWeekOffset += 7;
+		}
+
+		return firstDayOfMonth.plusDays(dayOfWeekOffset).plusDays(dayOffset);
+	}
+}

buildSrc/src/main/java/org/springframework/gradle/github/milestones/SpringReleaseTrainSpec.java

@@ -0,0 +1,205 @@
+/*
+ * Copyright 2002-2022 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
+ *
+ *      https://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.springframework.gradle.github.milestones;
+
+import java.time.LocalDate;
+import java.time.Month;
+import java.time.Year;
+
+import org.springframework.util.Assert;
+
+/**
+ * A specification for a release train.
+ *
+ * @author Steve Riesenberg
+ * @see SpringReleaseTrain
+ */
+public final class SpringReleaseTrainSpec {
+	private final Train train;
+	private final String version;
+	private final WeekOfMonth weekOfMonth;
+	private final DayOfWeek dayOfWeek;
+	private final Year year;
+
+	public SpringReleaseTrainSpec(Train train, String version, WeekOfMonth weekOfMonth, DayOfWeek dayOfWeek, Year year) {
+		this.train = train;
+		this.version = version;
+		this.weekOfMonth = weekOfMonth;
+		this.dayOfWeek = dayOfWeek;
+		this.year = year;
+	}
+
+	public Train getTrain() {
+		return train;
+	}
+
+	public String getVersion() {
+		return version;
+	}
+
+	public WeekOfMonth getWeekOfMonth() {
+		return weekOfMonth;
+	}
+
+	public DayOfWeek getDayOfWeek() {
+		return dayOfWeek;
+	}
+
+	public Year getYear() {
+		return year;
+	}
+
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	public enum WeekOfMonth {
+		FIRST(0), SECOND(7), THIRD(14), FOURTH(21);
+
+		private final int dayOffset;
+
+		WeekOfMonth(int dayOffset) {
+			this.dayOffset = dayOffset;
+		}
+
+		public int getDayOffset() {
+			return dayOffset;
+		}
+	}
+
+	public enum DayOfWeek {
+		MONDAY(java.time.DayOfWeek.MONDAY),
+		TUESDAY(java.time.DayOfWeek.TUESDAY),
+		WEDNESDAY(java.time.DayOfWeek.WEDNESDAY),
+		THURSDAY(java.time.DayOfWeek.THURSDAY),
+		FRIDAY(java.time.DayOfWeek.FRIDAY);
+
+		private final java.time.DayOfWeek dayOfWeek;
+
+		DayOfWeek(java.time.DayOfWeek dayOfWeek) {
+			this.dayOfWeek = dayOfWeek;
+		}
+
+		public java.time.DayOfWeek getDayOfWeek() {
+			return dayOfWeek;
+		}
+	}
+
+	public enum Train {
+		ONE, TWO
+	}
+
+	public static class Builder {
+		private Train train;
+		private String version;
+		private WeekOfMonth weekOfMonth;
+		private DayOfWeek dayOfWeek;
+		private Year year;
+
+		private Builder() {
+		}
+
+		public Builder train(int train) {
+			switch (train) {
+				case 1: this.train = Train.ONE; break;
+				case 2: this.train = Train.TWO; break;
+				default: throw new IllegalArgumentException("Invalid train: " + train);
+			}
+			return this;
+		}
+
+		public Builder train(Train train) {
+			this.train = train;
+			return this;
+		}
+
+		public Builder nextTrain() {
+			// Search for next train starting with this month
+			return nextTrain(LocalDate.now().withDayOfMonth(1));
+		}
+
+		public Builder nextTrain(LocalDate startDate) {
+			Train nextTrain = null;
+
+			// Search for next train from a given start date
+			LocalDate currentDate = startDate;
+			while (nextTrain == null) {
+				if (currentDate.getMonth() == Month.JANUARY) {
+					nextTrain = Train.ONE;
+				} else if (currentDate.getMonth() == Month.JULY) {
+					nextTrain = Train.TWO;
+				}
+
+				currentDate = currentDate.plusMonths(1);
+			}
+
+			return train(nextTrain).year(currentDate.getYear());
+		}
+
+		public Builder version(String version) {
+			this.version = version;
+			return this;
+		}
+
+		public Builder weekOfMonth(int weekOfMonth) {
+			switch (weekOfMonth) {
+				case 1: this.weekOfMonth = WeekOfMonth.FIRST; break;
+				case 2: this.weekOfMonth = WeekOfMonth.SECOND; break;
+				case 3: this.weekOfMonth = WeekOfMonth.THIRD; break;
+				case 4: this.weekOfMonth = WeekOfMonth.FOURTH; break;
+				default: throw new IllegalArgumentException("Invalid weekOfMonth: " + weekOfMonth);
+			}
+			return this;
+		}
+
+		public Builder weekOfMonth(WeekOfMonth weekOfMonth) {
+			this.weekOfMonth = weekOfMonth;
+			return this;
+		}
+
+		public Builder dayOfWeek(int dayOfWeek) {
+			switch (dayOfWeek) {
+				case 1: this.dayOfWeek = DayOfWeek.MONDAY; break;
+				case 2: this.dayOfWeek = DayOfWeek.TUESDAY; break;
+				case 3: this.dayOfWeek = DayOfWeek.WEDNESDAY; break;
+				case 4: this.dayOfWeek = DayOfWeek.THURSDAY; break;
+				case 5: this.dayOfWeek = DayOfWeek.FRIDAY; break;
+				default: throw new IllegalArgumentException("Invalid dayOfWeek: " + dayOfWeek);
+			}
+			return this;
+		}
+
+		public Builder dayOfWeek(DayOfWeek dayOfWeek) {
+			this.dayOfWeek = dayOfWeek;
+			return this;
+		}
+
+		public Builder year(int year) {
+			this.year = Year.of(year);
+			return this;
+		}
+
+		public SpringReleaseTrainSpec build() {
+			Assert.notNull(train, "train cannot be null");
+			Assert.notNull(version, "version cannot be null");
+			Assert.notNull(weekOfMonth, "weekOfMonth cannot be null");
+			Assert.notNull(dayOfWeek, "dayOfWeek cannot be null");
+			Assert.notNull(year, "year cannot be null");
+			return new SpringReleaseTrainSpec(train, version, weekOfMonth, dayOfWeek, year);
+		}
+	}
+}