/*
 * 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.apache.maven.artifact.versioning;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.WeakHashMap;

import org.apache.maven.artifact.Artifact;

/**
 * Construct a version range from a specification.
 *
 * @author <a href="mailto:brett@apache.org">Brett Porter</a>
 */
public class VersionRange {
    private static final Map<String, VersionRange> CACHE_SPEC =
            Collections.<String, VersionRange>synchronizedMap(new WeakHashMap<String, VersionRange>());

    private static final Map<String, VersionRange> CACHE_VERSION =
            Collections.<String, VersionRange>synchronizedMap(new WeakHashMap<String, VersionRange>());

    private final ArtifactVersion recommendedVersion;

    private final List<Restriction> restrictions;

    private VersionRange(ArtifactVersion recommendedVersion, List<Restriction> restrictions) {
        this.recommendedVersion = recommendedVersion;
        this.restrictions = restrictions;
    }

    public ArtifactVersion getRecommendedVersion() {
        return recommendedVersion;
    }

    public List<Restriction> getRestrictions() {
        return restrictions;
    }

    /**
     * @deprecated VersionRange is immutable, cloning is not useful and even more an issue against the cache
     * @return a clone
     */
    @Deprecated
    public VersionRange cloneOf() {
        List<Restriction> copiedRestrictions = null;

        if (restrictions != null) {
            copiedRestrictions = new ArrayList<>();

            if (!restrictions.isEmpty()) {
                copiedRestrictions.addAll(restrictions);
            }
        }

        return new VersionRange(recommendedVersion, copiedRestrictions);
    }

    /**
     * <p>
     * Create a version range from a string representation
     * </p>
     * Some spec examples are:
     * <ul>
     * <li><code>1.0</code> Version 1.0 as a recommended version</li>
     * <li><code>[1.0]</code> Version 1.0 explicitly only</li>
     * <li><code>[1.0,2.0)</code> Versions 1.0 (included) to 2.0 (not included)</li>
     * <li><code>[1.0,2.0]</code> Versions 1.0 to 2.0 (both included)</li>
     * <li><code>[1.5,)</code> Versions 1.5 and higher</li>
     * <li><code>(,1.0],[1.2,)</code> Versions up to 1.0 (included) and 1.2 or higher</li>
     * </ul>
     *
     * @param spec string representation of a version or version range
     * @return a new {@link VersionRange} object that represents the spec
     * @throws InvalidVersionSpecificationException
     *
     */
    public static VersionRange createFromVersionSpec(String spec) throws InvalidVersionSpecificationException {
        if (spec == null) {
            return null;
        }

        VersionRange cached = CACHE_SPEC.get(spec);
        if (cached != null) {
            return cached;
        }

        List<Restriction> restrictions = new ArrayList<>();
        String process = spec;
        ArtifactVersion version = null;
        ArtifactVersion upperBound = null;
        ArtifactVersion lowerBound = null;

        while (process.startsWith("[") || process.startsWith("(")) {
            int index1 = process.indexOf(')');
            int index2 = process.indexOf(']');

            int index = index2;
            if (index2 < 0 || index1 < index2) {
                if (index1 >= 0) {
                    index = index1;
                }
            }

            if (index < 0) {
                throw new InvalidVersionSpecificationException("Unbounded range: " + spec);
            }

            Restriction restriction = parseRestriction(process.substring(0, index + 1));
            if (lowerBound == null) {
                lowerBound = restriction.getLowerBound();
            }
            if (upperBound != null) {
                if (restriction.getLowerBound() == null
                        || restriction.getLowerBound().compareTo(upperBound) < 0) {
                    throw new InvalidVersionSpecificationException("Ranges overlap: " + spec);
                }
            }
            restrictions.add(restriction);
            upperBound = restriction.getUpperBound();

            process = process.substring(index + 1).trim();

            if (process.length() > 0 && process.startsWith(",")) {
                process = process.substring(1).trim();
            }
        }

        if (process.length() > 0) {
            if (restrictions.size() > 0) {
                throw new InvalidVersionSpecificationException(
                        "Only fully-qualified sets allowed in multiple set scenario: " + spec);
            } else {
                version = new DefaultArtifactVersion(process);
                restrictions.add(Restriction.EVERYTHING);
            }
        }

        cached = new VersionRange(version, restrictions);
        CACHE_SPEC.put(spec, cached);
        return cached;
    }

    private static Restriction parseRestriction(String spec) throws InvalidVersionSpecificationException {
        boolean lowerBoundInclusive = spec.startsWith("[");
        boolean upperBoundInclusive = spec.endsWith("]");

        String process = spec.substring(1, spec.length() - 1).trim();

        Restriction restriction;

        int index = process.indexOf(',');

        if (index < 0) {
            if (!lowerBoundInclusive || !upperBoundInclusive) {
                throw new InvalidVersionSpecificationException("Single version must be surrounded by []: " + spec);
            }

            ArtifactVersion version = new DefaultArtifactVersion(process);

            restriction = new Restriction(version, lowerBoundInclusive, version, upperBoundInclusive);
        } else {
            String lowerBound = process.substring(0, index).trim();
            String upperBound = process.substring(index + 1).trim();

            ArtifactVersion lowerVersion = null;
            if (lowerBound.length() > 0) {
                lowerVersion = new DefaultArtifactVersion(lowerBound);
            }
            ArtifactVersion upperVersion = null;
            if (upperBound.length() > 0) {
                upperVersion = new DefaultArtifactVersion(upperBound);
            }

            if (upperVersion != null && lowerVersion != null) {
                int result = upperVersion.compareTo(lowerVersion);
                if (result < 0 || (result == 0 && (!lowerBoundInclusive || !upperBoundInclusive))) {
                    throw new InvalidVersionSpecificationException("Range defies version ordering: " + spec);
                }
            }

            restriction = new Restriction(lowerVersion, lowerBoundInclusive, upperVersion, upperBoundInclusive);
        }

        return restriction;
    }

    public static VersionRange createFromVersion(String version) {
        VersionRange cached = CACHE_VERSION.get(version);
        if (cached == null) {
            List<Restriction> restrictions = Collections.emptyList();
            cached = new VersionRange(new DefaultArtifactVersion(version), restrictions);
            CACHE_VERSION.put(version, cached);
        }
        return cached;
    }

    /**
     * Creates and returns a new <code>VersionRange</code> that is a restriction of this
     * version range and the specified version range.
     * <p>
     * Note: Precedence is given to the recommended version from this version range over the
     * recommended version from the specified version range.
     * </p>
     *
     * @param restriction the <code>VersionRange</code> that will be used to restrict this version
     *                    range.
     * @return the <code>VersionRange</code> that is a restriction of this version range and the
     *         specified version range.
     *         <p>
     *         The restrictions of the returned version range will be an intersection of the restrictions
     *         of this version range and the specified version range if both version ranges have
     *         restrictions. Otherwise, the restrictions on the returned range will be empty.
     *         </p>
     *         <p>
     *         The recommended version of the returned version range will be the recommended version of
     *         this version range, provided that ranges falls within the intersected restrictions. If
     *         the restrictions are empty, this version range's recommended version is used if it is not
     *         <code>null</code>. If it is <code>null</code>, the specified version range's recommended
     *         version is used (provided it is non-<code>null</code>). If no recommended version can be
     *         obtained, the returned version range's recommended version is set to <code>null</code>.
     *         </p>
     * @throws NullPointerException if the specified <code>VersionRange</code> is
     *                              <code>null</code>.
     */
    public VersionRange restrict(VersionRange restriction) {
        List<Restriction> r1 = this.restrictions;
        List<Restriction> r2 = restriction.restrictions;
        List<Restriction> restrictions;

        if (r1.isEmpty() || r2.isEmpty()) {
            restrictions = Collections.emptyList();
        } else {
            restrictions = Collections.unmodifiableList(intersection(r1, r2));
        }

        ArtifactVersion version = null;
        if (restrictions.size() > 0) {
            for (Restriction r : restrictions) {
                if (recommendedVersion != null && r.containsVersion(recommendedVersion)) {
                    // if we find the original, use that
                    version = recommendedVersion;
                    break;
                } else if (version == null
                        && restriction.getRecommendedVersion() != null
                        && r.containsVersion(restriction.getRecommendedVersion())) {
                    // use this if we can, but prefer the original if possible
                    version = restriction.getRecommendedVersion();
                }
            }
        }
        // Either the original or the specified version ranges have no restrictions
        else if (recommendedVersion != null) {
            // Use the original recommended version since it exists
            version = recommendedVersion;
        } else if (restriction.recommendedVersion != null) {
            // Use the recommended version from the specified VersionRange since there is no
            // original recommended version
            version = restriction.recommendedVersion;
        }
        /* TODO should throw this immediately, but need artifact
                else
                {
                    throw new OverConstrainedVersionException( "Restricting incompatible version ranges" );
                }
        */

        return new VersionRange(version, restrictions);
    }

    private List<Restriction> intersection(List<Restriction> r1, List<Restriction> r2) {
        List<Restriction> restrictions = new ArrayList<>(r1.size() + r2.size());
        Iterator<Restriction> i1 = r1.iterator();
        Iterator<Restriction> i2 = r2.iterator();
        Restriction res1 = i1.next();
        Restriction res2 = i2.next();

        boolean done = false;
        while (!done) {
            if (res1.getLowerBound() == null
                    || res2.getUpperBound() == null
                    || res1.getLowerBound().compareTo(res2.getUpperBound()) <= 0) {
                if (res1.getUpperBound() == null
                        || res2.getLowerBound() == null
                        || res1.getUpperBound().compareTo(res2.getLowerBound()) >= 0) {
                    ArtifactVersion lower;
                    ArtifactVersion upper;
                    boolean lowerInclusive;
                    boolean upperInclusive;

                    // overlaps
                    if (res1.getLowerBound() == null) {
                        lower = res2.getLowerBound();
                        lowerInclusive = res2.isLowerBoundInclusive();
                    } else if (res2.getLowerBound() == null) {
                        lower = res1.getLowerBound();
                        lowerInclusive = res1.isLowerBoundInclusive();
                    } else {
                        int comparison = res1.getLowerBound().compareTo(res2.getLowerBound());
                        if (comparison < 0) {
                            lower = res2.getLowerBound();
                            lowerInclusive = res2.isLowerBoundInclusive();
                        } else if (comparison == 0) {
                            lower = res1.getLowerBound();
                            lowerInclusive = res1.isLowerBoundInclusive() && res2.isLowerBoundInclusive();
                        } else {
                            lower = res1.getLowerBound();
                            lowerInclusive = res1.isLowerBoundInclusive();
                        }
                    }

                    if (res1.getUpperBound() == null) {
                        upper = res2.getUpperBound();
                        upperInclusive = res2.isUpperBoundInclusive();
                    } else if (res2.getUpperBound() == null) {
                        upper = res1.getUpperBound();
                        upperInclusive = res1.isUpperBoundInclusive();
                    } else {
                        int comparison = res1.getUpperBound().compareTo(res2.getUpperBound());
                        if (comparison < 0) {
                            upper = res1.getUpperBound();
                            upperInclusive = res1.isUpperBoundInclusive();
                        } else if (comparison == 0) {
                            upper = res1.getUpperBound();
                            upperInclusive = res1.isUpperBoundInclusive() && res2.isUpperBoundInclusive();
                        } else {
                            upper = res2.getUpperBound();
                            upperInclusive = res2.isUpperBoundInclusive();
                        }
                    }

                    // don't add if they are equal and one is not inclusive
                    if (lower == null || upper == null || lower.compareTo(upper) != 0) {
                        restrictions.add(new Restriction(lower, lowerInclusive, upper, upperInclusive));
                    } else if (lowerInclusive && upperInclusive) {
                        restrictions.add(new Restriction(lower, lowerInclusive, upper, upperInclusive));
                    }

                    //noinspection ObjectEquality
                    if (upper == res2.getUpperBound()) {
                        // advance res2
                        if (i2.hasNext()) {
                            res2 = i2.next();
                        } else {
                            done = true;
                        }
                    } else {
                        // advance res1
                        if (i1.hasNext()) {
                            res1 = i1.next();
                        } else {
                            done = true;
                        }
                    }
                } else {
                    // move on to next in r1
                    if (i1.hasNext()) {
                        res1 = i1.next();
                    } else {
                        done = true;
                    }
                }
            } else {
                // move on to next in r2
                if (i2.hasNext()) {
                    res2 = i2.next();
                } else {
                    done = true;
                }
            }
        }

        return restrictions;
    }

    public ArtifactVersion getSelectedVersion(Artifact artifact) throws OverConstrainedVersionException {
        ArtifactVersion version;
        if (recommendedVersion != null) {
            version = recommendedVersion;
        } else {
            if (restrictions.size() == 0) {
                throw new OverConstrainedVersionException("The artifact has no valid ranges", artifact);
            }

            version = null;
        }
        return version;
    }

    public boolean isSelectedVersionKnown(Artifact artifact) throws OverConstrainedVersionException {
        boolean value = false;
        if (recommendedVersion != null) {
            value = true;
        } else {
            if (restrictions.size() == 0) {
                throw new OverConstrainedVersionException("The artifact has no valid ranges", artifact);
            }
        }
        return value;
    }

    public String toString() {
        if (recommendedVersion != null) {
            return recommendedVersion.toString();
        } else {
            StringBuilder buf = new StringBuilder();
            for (Iterator<Restriction> i = restrictions.iterator(); i.hasNext(); ) {
                Restriction r = i.next();

                buf.append(r.toString());

                if (i.hasNext()) {
                    buf.append(',');
                }
            }
            return buf.toString();
        }
    }

    public ArtifactVersion matchVersion(List<ArtifactVersion> versions) {
        // TODO could be more efficient by sorting the list and then moving along the restrictions in order?

        ArtifactVersion matched = null;
        for (ArtifactVersion version : versions) {
            if (containsVersion(version)) {
                // valid - check if it is greater than the currently matched version
                if (matched == null || version.compareTo(matched) > 0) {
                    matched = version;
                }
            }
        }
        return matched;
    }

    public boolean containsVersion(ArtifactVersion version) {
        for (Restriction restriction : restrictions) {
            if (restriction.containsVersion(version)) {
                return true;
            }
        }
        return false;
    }

    public boolean hasRestrictions() {
        return !restrictions.isEmpty() && recommendedVersion == null;
    }

    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof VersionRange)) {
            return false;
        }
        VersionRange other = (VersionRange) obj;

        return Objects.equals(recommendedVersion, other.recommendedVersion)
                && Objects.equals(restrictions, other.restrictions);
    }

    public int hashCode() {
        int hash = 7;
        hash = 31 * hash + (recommendedVersion == null ? 0 : recommendedVersion.hashCode());
        hash = 31 * hash + (restrictions == null ? 0 : restrictions.hashCode());
        return hash;
    }
}
