/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.eclipse.aether.resolution;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import org.eclipse.aether.RepositoryException;
import org.eclipse.aether.repository.ArtifactRepository;
import org.eclipse.aether.repository.LocalArtifactResult;
import org.eclipse.aether.transfer.ArtifactFilteredOutException;
import org.eclipse.aether.transfer.ArtifactNotFoundException;
import org.eclipse.aether.transfer.RepositoryOfflineException;

/**
 * Thrown in case of a unresolvable artifacts.
 */
public class ArtifactResolutionException extends RepositoryException {
    private final transient List<ArtifactResult> results;

    /**
     * Creates a new exception with the specified results.
     *
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     */
    public ArtifactResolutionException(List<ArtifactResult> results) {
        super(getSmartMessage(results), getSmartCause(results));
        if (results != null) {
            getSuppressed(results).forEach(this::addSuppressed);
        }
        this.results = results != null ? results : Collections.emptyList();
    }

    /**
     * Creates a new exception with the specified results and detail message.
     *
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     * @param message The detail message, may be {@code null}.
     */
    public ArtifactResolutionException(List<ArtifactResult> results, String message) {
        super(message, getSmartCause(results));
        if (results != null) {
            getSuppressed(results).forEach(this::addSuppressed);
        }
        this.results = results != null ? results : Collections.emptyList();
    }

    /**
     * Creates a new exception with the specified results, detail message and cause.
     *
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     * @param message The detail message, may be {@code null}.
     * @param cause The exception that caused this one, may be {@code null}.
     */
    public ArtifactResolutionException(List<ArtifactResult> results, String message, Throwable cause) {
        super(message, cause);
        if (results != null) {
            getSuppressed(results).forEach(this::addSuppressed);
        }
        this.results = results != null ? results : Collections.emptyList();
    }

    /**
     * Gets the resolution results at the point the exception occurred. Despite being incomplete, callers might want to
     * use these results to fail gracefully and continue their operation with whatever interim data has been gathered.
     *
     * @return The resolution results, never {@code null} (empty if unknown).
     */
    public List<ArtifactResult> getResults() {
        return results;
    }

    /**
     * Gets the first result from {@link #getResults()}. This is a convenience method for cases where callers know only
     * a single result/request is involved.
     *
     * @return The (first) resolution result or {@code null} if none.
     */
    public ArtifactResult getResult() {
        return (results != null && !results.isEmpty()) ? results.get(0) : null;
    }

    private static String getSmartMessage(List<? extends ArtifactResult> results) {
        if (results == null) {
            return null;
        }
        StringBuilder buffer = new StringBuilder(256);

        buffer.append("The following artifacts could not be resolved: ");

        String sep = "";
        for (ArtifactResult result : results) {
            if (!result.isResolved()) {
                buffer.append(sep);
                buffer.append(result.getRequest().getArtifact());
                LocalArtifactResult localResult = result.getLocalArtifactResult();
                if (localResult != null) {
                    buffer.append(" (");
                    if (localResult.getPath() != null) {
                        buffer.append("present");
                        if (!localResult.isAvailable()) {
                            buffer.append(", but unavailable");
                        }
                    } else {
                        buffer.append("absent");
                    }
                    buffer.append(")");
                }
                sep = ", ";
            }
        }

        Throwable cause = getSmartCause(results);
        if (cause != null) {
            buffer.append(": ").append(cause.getMessage());
        }

        String additionalFailures = getAdditionalFailures(results, cause);
        if (!additionalFailures.isEmpty()) {
            buffer.append(" (additional failures: ").append(additionalFailures).append(")");
        }

        return buffer.toString();
    }

    private static String getAdditionalFailures(List<? extends ArtifactResult> results, Throwable primaryCause) {
        List<String> failures = new ArrayList<>();
        for (ArtifactResult result : results) {
            if (!result.isResolved()) {
                for (Map.Entry<ArtifactRepository, List<Exception>> entry :
                        result.getMappedExceptions().entrySet()) {
                    for (Exception exception : entry.getValue()) {
                        if (exception != primaryCause) {
                            String message = exception.getMessage();
                            if (message == null) {
                                message = exception.getClass().getSimpleName();
                            }
                            failures.add(result.getRequest().getArtifact() + " from "
                                    + entry.getKey().getId() + ": " + message);
                        }
                    }
                }
            }
        }
        Collections.sort(failures);
        return String.join("; ", failures);
    }

    /**
     * This method tries to be smart and figure out "cause", but it results in somewhat incomplete result. Maven Core
     * and probably many other code relies on it, so is left in place, but client code should use {@link #getResults()}
     * and {@link ArtifactResult#getMappedExceptions()} methods to build more appropriate error messages.
     */
    private static Throwable getSmartCause(List<? extends ArtifactResult> results) {
        if (results == null) {
            return null;
        }
        for (ArtifactResult result : results) {
            if (!result.isResolved()) {
                Throwable notFound = null, offline = null;
                for (Throwable t : result.getExceptions()) {
                    if (t instanceof ArtifactNotFoundException) {
                        if (notFound == null || notFound instanceof ArtifactFilteredOutException) {
                            notFound = t;
                        }
                        if (offline == null && t.getCause() instanceof RepositoryOfflineException) {
                            offline = t;
                        }
                    } else {
                        return t;
                    }
                }
                if (offline != null) {
                    return offline;
                }
                if (notFound != null) {
                    return notFound;
                }
            }
        }
        return null;
    }

    /**
     * Builds a forest of exceptions to be used as suppressed, and it will contain the whole forest of exceptions per
     * repository.
     */
    private static List<Throwable> getSuppressed(List<? extends ArtifactResult> results) {
        ArrayList<Throwable> result = new ArrayList<>(results.size());
        for (ArtifactResult artifactResult : results) {
            if (!artifactResult.isResolved()) {
                ArtifactResolutionException root = new ArtifactResolutionException(
                        null,
                        "Failed to resolve artifact "
                                + artifactResult.getRequest().getArtifact());
                for (Map.Entry<ArtifactRepository, List<Exception>> entry :
                        artifactResult.getMappedExceptions().entrySet()) {
                    for (Exception e : entry.getValue()) {
                        root.addSuppressed(e);
                    }
                }
                result.add(root);
            }
        }
        return result;
    }
}