/**
 * Copyright (C) 2022, 2024, 2025 Adrien Hopkins
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package sevenUnits.utils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A version number in the <a href="https://semver.org">Semantic Versioning</a>
 * scheme
 * <p>
 * Each version number has three main parts:
 * <ol>
 * <li>The major version, which increments when backwards incompatible changes
 * are made
 * <li>The minor version, which increments when backwards compatible feature
 * changes are made
 * <li>The patch version, which increments when backwards compatible bug fixes
 * are made
 * </ol>
 *
 * @since v0.4.0
 * @since 2022-02-19
 */
public final class SemanticVersionNumber
		implements Comparable<SemanticVersionNumber> {
	/**
	 * A builder that can be used to create complex version numbers.
	 * <p>
	 * Note: None of this builder's methods tolerate null arguments, arrays
	 * containing nulls, negative numbers, or non-alphanumeric identifiers. Nulls
	 * throw NullPointerExceptions, everything else throws
	 * IllegalArgumentException.
	 *
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public static final class Builder {
		private final int major;
		private final int minor;
		private final int patch;
		private final List<String> preReleaseIdentifiers;
		private final List<String> buildMetadata;

		/**
		 * Creates a builder which can be used to create a
		 * {@code SemanticVersionNumber}
		 *
		 * @param major major version number of final version
		 * @param minor minor version number of final version
		 * @param patch patch version number of final version
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		private Builder(int major, int minor, int patch) {
			this.major = major;
			this.minor = minor;
			this.patch = patch;
			this.preReleaseIdentifiers = new ArrayList<>();
			this.buildMetadata = new ArrayList<>();
		}

		/**
		 * @return version number created by this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public SemanticVersionNumber build() {
			return new SemanticVersionNumber(this.major, this.minor, this.patch,
					this.preReleaseIdentifiers, this.buildMetadata);
		}

		/**
		 * Adds one or more build metadata identifiers
		 *
		 * @param identifiers build metadata
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder buildMetadata(List<String> identifiers) {
			Objects.requireNonNull(identifiers, "identifiers may not be null");
			for (final String identifier : identifiers) {
				Objects.requireNonNull(identifier, "identifier may not be null");
				if (!VALID_IDENTIFIER.matcher(identifier).matches())
					throw new IllegalArgumentException(
							String.format("Invalid identifier \"%s\"", identifier));
				this.buildMetadata.add(identifier);
			}
			return this;
		}

		/**
		 * Adds one or more build metadata identifiers
		 *
		 * @param identifiers build metadata
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder buildMetadata(String... identifiers) {
			Objects.requireNonNull(identifiers, "identifiers may not be null");
			for (final String identifier : identifiers) {
				Objects.requireNonNull(identifier, "identifier may not be null");
				if (!VALID_IDENTIFIER.matcher(identifier).matches())
					throw new IllegalArgumentException(
							String.format("Invalid identifier \"%s\"", identifier));
				this.buildMetadata.add(identifier);
			}
			return this;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (!(obj instanceof Builder))
				return false;
			final Builder other = (Builder) obj;
			return Objects.equals(this.buildMetadata, other.buildMetadata)
					&& this.major == other.major && this.minor == other.minor
					&& this.patch == other.patch && Objects.equals(
							this.preReleaseIdentifiers, other.preReleaseIdentifiers);
		}

		@Override
		public int hashCode() {
			return Objects.hash(this.buildMetadata, this.major, this.minor,
					this.patch, this.preReleaseIdentifiers);
		}

		/**
		 * Adds one or more numeric identifiers to the version number
		 *
		 * @param identifiers pre-release identifier(s) to add
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder preRelease(int... identifiers) {
			Objects.requireNonNull(identifiers, "identifiers may not be null");
			for (final int identifier : identifiers) {
				if (identifier < 0)
					throw new IllegalArgumentException(
							"Numeric identifiers may not be negative");
				this.preReleaseIdentifiers.add(Integer.toString(identifier));
			}
			return this;
		}

		/**
		 * Adds one or more pre-release identifier(s) to the version number
		 *
		 * @param identifiers pre-release identifier(s) to add
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder preRelease(List<String> identifiers) {
			Objects.requireNonNull(identifiers, "identifiers may not be null");
			for (final String identifier : identifiers) {
				Objects.requireNonNull(identifier, "identifier may not be null");
				if (!VALID_IDENTIFIER.matcher(identifier).matches())
					throw new IllegalArgumentException(
							String.format("Invalid identifier \"%s\"", identifier));
				this.preReleaseIdentifiers.add(identifier);
			}
			return this;
		}

		/**
		 * Adds one or more pre-release identifier(s) to the version number
		 *
		 * @param identifiers pre-release identifier(s) to add
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder preRelease(String... identifiers) {
			Objects.requireNonNull(identifiers, "identifiers may not be null");
			for (final String identifier : identifiers) {
				Objects.requireNonNull(identifier, "identifier may not be null");
				if (!VALID_IDENTIFIER.matcher(identifier).matches())
					throw new IllegalArgumentException(
							String.format("Invalid identifier \"%s\"", identifier));
				this.preReleaseIdentifiers.add(identifier);
			}
			return this;
		}

		/**
		 * Adds a string identifier and an integer identifer to pre-release data
		 *
		 * @param identifier1 first identifier
		 * @param identifier2 second identifier
		 * @return this builder
		 * @since v0.4.0
		 * @since 2022-02-19
		 */
		public Builder preRelease(String identifier1, int identifier2) {
			Objects.requireNonNull(identifier1, "identifier1 may not be null");
			if (!VALID_IDENTIFIER.matcher(identifier1).matches())
				throw new IllegalArgumentException(
						String.format("Invalid identifier \"%s\"", identifier1));
			if (identifier2 < 0)
				throw new IllegalArgumentException(
						"Integer identifier cannot be negative");
			this.preReleaseIdentifiers.add(identifier1);
			this.preReleaseIdentifiers.add(Integer.toString(identifier2));
			return this;
		}

		@Override
		public String toString() {
			return "Semantic Version Builder: " + this.build().toString();
		}
	}

	/**
	 * An alternative comparison method for version numbers. This uses the
	 * version's natural order, but the build metadata will be compared (using
	 * the same rules as pre-release identifiers) if everything else is equal.
	 * <p>
	 * This ordering is consistent with equals, unlike
	 * {@code SemanticVersionNumber}'s natural ordering.
	 */
	public static final Comparator<SemanticVersionNumber> BUILD_METADATA_COMPARATOR = new Comparator<>() {
		@Override
		public int compare(SemanticVersionNumber o1, SemanticVersionNumber o2) {
			Objects.requireNonNull(o1, "o1 may not be null");
			Objects.requireNonNull(o2, "o2 may not be null");
			final int naturalComparison = o1.compareTo(o2);
			if (naturalComparison == 0)
				return SemanticVersionNumber.compareIdentifiers(o1.buildMetadata,
						o2.buildMetadata);
			else
				return naturalComparison;
		};
	};

	/** The alphanumeric pattern all identifiers must follow */
	private static final Pattern VALID_IDENTIFIER = Pattern
			.compile("[0-9A-Za-z-]+");

	/** The numeric pattern which causes special behaviour */
	private static final Pattern NUMERIC_IDENTIFER = Pattern.compile("[0-9]+");

	/** The pattern for a version number */
	private static final Pattern VERSION_NUMBER = Pattern
			.compile("(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)" // main
					// version
					+ "(?:-([0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?" // pre-release
					+ "(?:\\+([0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?"); // build data

	/**
	 * Creates a builder that can be used to create a version number
	 *
	 * @param major major version number of final version
	 * @param minor minor version number of final version
	 * @param patch patch version number of final version
	 * @return version number builder
	 * @throws IllegalArgumentException if any argument is negative
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public static final SemanticVersionNumber.Builder builder(int major,
			int minor, int patch) {
		if (major < 0)
			throw new IllegalArgumentException(
					"Major version must be non-negative.");
		if (minor < 0)
			throw new IllegalArgumentException(
					"Minor version must be non-negative.");
		if (patch < 0)
			throw new IllegalArgumentException(
					"Patch version must be non-negative.");
		return new SemanticVersionNumber.Builder(major, minor, patch);
	}

	/**
	 * Compares two lists of strings based on SemVer's precedence rules
	 *
	 * @param a first list
	 * @param b second list
	 * @return result of comparison as in a comparator
	 * @see Comparator
	 * @since v0.4.0
	 * @since 2022-02-20
	 */
	private static final int compareIdentifiers(List<String> a, List<String> b) {
		// test pre-release size
		final int aSize = a.size();
		final int bSize = b.size();

		// no identifiers is greater than any identifiers
		if (aSize != 0 && bSize == 0)
			return -1;
		else if (aSize == 0 && bSize != 0)
			return 1;

		// test identifiers one by one
		for (int i = 0; i < Math.min(aSize, bSize); i++) {
			final String aElement = a.get(i);
			final String bElement = b.get(i);

			if (NUMERIC_IDENTIFER.matcher(aElement).matches()) {
				if (NUMERIC_IDENTIFER.matcher(bElement).matches()) {
					// both are numbers, compare them
					final int aNumber = Integer.parseInt(aElement);
					final int bNumber = Integer.parseInt(bElement);

					if (aNumber < bNumber)
						return -1;
					else if (aNumber > bNumber)
						return 1;
				} else
					// aElement is a number and bElement is not a number
					// by the rules, a goes before b
					return -1;
			} else {
				if (NUMERIC_IDENTIFER.matcher(bElement).matches())
					// aElement is not a number but bElement is
					// by the rules, a goes after b
					return 1;
				else {
					// both are not numbers, compare them
					final int comparison = aElement.compareTo(bElement);
					if (comparison != 0)
						return comparison;
				}
			}
		}

		// we just tested the stuff that's in common, maybe someone has more
		if (aSize < bSize)
			return -1;
		else if (aSize > bSize)
			return 1;
		else
			return 0;
	}

	/**
	 * Gets a version number from a string in the official format
	 *
	 * @param versionString string to parse
	 * @return {@code SemanticVersionNumber} instance
	 * @since v0.4.0
	 * @since 2022-02-19
	 * @see #toString
	 */
	public static final SemanticVersionNumber fromString(String versionString) {
		// parse & validate version string
		Objects.requireNonNull(versionString, "versionString may not be null");
		final Matcher m = VERSION_NUMBER.matcher(versionString);
		if (!m.matches())
			throw new IllegalArgumentException(
					String.format("Provided string \"%s\" is not a version number",
							versionString));

		// main parts
		final int major = Integer.parseInt(m.group(1));
		final int minor = Integer.parseInt(m.group(2));
		final int patch = Integer.parseInt(m.group(3));

		// pre release
		final List<String> preRelease;
		if (m.group(4) == null) {
			preRelease = List.of();
		} else {
			preRelease = Arrays.asList(m.group(4).split("\\."));
		}

		// build metadata
		final List<String> buildMetadata;
		if (m.group(5) == null) {
			buildMetadata = List.of();
		} else {
			buildMetadata = Arrays.asList(m.group(5).split("\\."));
		}

		// return number
		return new SemanticVersionNumber(major, minor, patch, preRelease,
				buildMetadata);
	}

	/**
	 * Tests whether a string is a valid Semantic Version string
	 * 
	 * @param versionString string to test
	 * @return true iff string is valid
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public static final boolean isValidVersionString(String versionString) {
		return VERSION_NUMBER.matcher(versionString).matches();
	}

	/**
	 * Creates a simple pre-release version number of the form
	 * MAJOR.MINOR.PATH-TYPE.NUMBER (e.g. 1.2.3-alpha.4).
	 *
	 * @param major            major version number
	 * @param minor            minor version number
	 * @param patch            patch version number
	 * @param preReleaseType   first pre-release element
	 * @param preReleaseNumber second pre-release element
	 * @return {@code SemanticVersionNumber} instance
	 * @throws IllegalArgumentException if any argument is negative or if the
	 *                                  preReleaseType is null, empty or not
	 *                                  alphanumeric (0-9, A-Z, a-z, - only)
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public static final SemanticVersionNumber preRelease(int major, int minor,
			int patch, String preReleaseType, int preReleaseNumber) {
		if (major < 0)
			throw new IllegalArgumentException(
					"Major version must be non-negative.");
		if (minor < 0)
			throw new IllegalArgumentException(
					"Minor version must be non-negative.");
		if (patch < 0)
			throw new IllegalArgumentException(
					"Patch version must be non-negative.");
		Objects.requireNonNull(preReleaseType, "preReleaseType may not be null");
		if (!VALID_IDENTIFIER.matcher(preReleaseType).matches())
			throw new IllegalArgumentException(
					String.format("Invalid identifier \"%s\".", preReleaseType));
		if (preReleaseNumber < 0)
			throw new IllegalArgumentException(
					"Pre-release number must be non-negative.");
		return new SemanticVersionNumber(major, minor, patch,
				List.of(preReleaseType, Integer.toString(preReleaseNumber)),
				List.of());
	}

	/**
	 * Creates a {@code SemanticVersionNumber} instance without pre-release
	 * identifiers or build metadata.
	 * <p>
	 * Note: this method allows you to create versions with major version number
	 * 0, even though these versions would not be considered stable.
	 *
	 * @param major major version number
	 * @param minor minor version number
	 * @param patch patch version number
	 * @return {@code SemanticVersionNumber} instance
	 * @throws IllegalArgumentException if any argument is negative
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public static final SemanticVersionNumber stableVersion(int major, int minor,
			int patch) {
		if (major < 0)
			throw new IllegalArgumentException(
					"Major version must be non-negative.");
		if (minor < 0)
			throw new IllegalArgumentException(
					"Minor version must be non-negative.");
		if (patch < 0)
			throw new IllegalArgumentException(
					"Patch version must be non-negative.");
		return new SemanticVersionNumber(major, minor, patch, List.of(),
				List.of());
	}

	// parts of the version number
	private final int major;
	private final int minor;
	private final int patch;
	private final List<String> preReleaseIdentifiers;
	private final List<String> buildMetadata;

	/**
	 * Creates a version number
	 *
	 * @param major                 major version number
	 * @param minor                 minor version number
	 * @param patch                 patch version number
	 * @param preReleaseIdentifiers pre-release version data
	 * @param buildMetadata         build metadata
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	private SemanticVersionNumber(int major, int minor, int patch,
			List<String> preReleaseIdentifiers, List<String> buildMetadata) {
		this.major = major;
		this.minor = minor;
		this.patch = patch;
		this.preReleaseIdentifiers = preReleaseIdentifiers;
		this.buildMetadata = buildMetadata;
	}

	/**
	 * @return build metadata (empty if there is none)
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public List<String> buildMetadata() {
		return Collections.unmodifiableList(this.buildMetadata);
	}

	/**
	 * Compares two version numbers according to the official Semantic Versioning
	 * order.
	 * <p>
	 * Note: this ordering is not consistent with equals. Specifically, two
	 * versions that are identical except for their build metadata will be
	 * considered different by equals but the same by this method. This is
	 * required to follow the official Semantic Versioning specification.
	 * <p>
	 */
	@Override
	public int compareTo(SemanticVersionNumber o) {
		// test the three big numbers in order first
		if (this.major < o.major)
			return -1;
		else if (this.major > o.major)
			return 1;

		if (this.minor < o.minor)
			return -1;
		else if (this.minor > o.minor)
			return 1;

		if (this.patch < o.patch)
			return -1;
		else if (this.patch > o.patch)
			return 1;

		// now we just compare pre-release identifiers
		// (remember: build metadata is ignored)
		return SemanticVersionNumber.compareIdentifiers(
				this.preReleaseIdentifiers, o.preReleaseIdentifiers);
	}

	/**
	 * Determines the compatibility of code written for this version to
	 * {@code other}. More specifically:
	 * <p>
	 * If this function returns <b>true</b>, then there should be no problems
	 * upgrading code written for this version to version {@code other} as long
	 * as:
	 * <ul>
	 * <li>Semantic Versioning is being used properly
	 * <li>Your code doesn't depend on unintended features (if it does, it isn't
	 * necessarily compatible with any other version)
	 * </ul>
	 * If this function returns <b>false</b>, you may have to change your code to
	 * upgrade it to {@code other}
	 * 
	 * <p>
	 * Two version numbers that are identical (ignoring build metadata) are
	 * always compatible. Different version numbers are compatible as long as:
	 * <ul>
	 * <li>The major version number is not 0 (if it is, the API is considered
	 * unstable and any upgrade can be backwards incompatible)
	 * <li>The major version number is the same (changing the major version
	 * number implies backwards incompatible changes)
	 * <li>This version comes before the other one in the official precedence
	 * order (downgrading can remove features you depend on)
	 * </ul>
	 *
	 * @param other version to compare with
	 * @return true if you can definitely upgrade to {@code other} without
	 *         changing code
	 * @since v0.4.0
	 * @since 2022-02-20
	 */
	public boolean compatibleWith(SemanticVersionNumber other) {
		Objects.requireNonNull(other, "other may not be null");

		return this.compareTo(other) == 0 || this.major != 0
				&& this.major == other.major && this.compareTo(other) < 0;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (!(obj instanceof SemanticVersionNumber))
			return false;
		final SemanticVersionNumber other = (SemanticVersionNumber) obj;
		if (this.buildMetadata == null) {
			if (other.buildMetadata != null)
				return false;
		} else if (!this.buildMetadata.equals(other.buildMetadata))
			return false;
		if (this.major != other.major)
			return false;
		if (this.minor != other.minor)
			return false;
		if (this.patch != other.patch)
			return false;
		if (this.preReleaseIdentifiers == null) {
			if (other.preReleaseIdentifiers != null)
				return false;
		} else if (!this.preReleaseIdentifiers
				.equals(other.preReleaseIdentifiers))
			return false;
		return true;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result
				+ (this.buildMetadata == null ? 0 : this.buildMetadata.hashCode());
		result = prime * result + this.major;
		result = prime * result + this.minor;
		result = prime * result + this.patch;
		result = prime * result + (this.preReleaseIdentifiers == null ? 0
				: this.preReleaseIdentifiers.hashCode());
		return result;
	}

	/**
	 * @return true iff this version is stable (major version > 0 and not a
	 *         pre-release)
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public boolean isStable() {
		return this.major > 0 && this.preReleaseIdentifiers.isEmpty();
	}

	/**
	 * @return the MAJOR version number, incremented when you make backwards
	 *         incompatible API changes
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public int majorVersion() {
		return this.major;
	}

	/**
	 * @return the MINOR version number, incremented when you add backwards
	 *         compatible functionality
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public int minorVersion() {
		return this.minor;
	}

	/**
	 * @return the PATCH version number, incremented when you make backwards
	 *         compatible bug fixes
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public int patchVersion() {
		return this.patch;
	}

	/**
	 * @return identifiers describing this pre-release (empty if not a
	 *         pre-release)
	 * @since v0.4.0
	 * @since 2022-02-19
	 */
	public List<String> preReleaseIdentifiers() {
		return Collections.unmodifiableList(this.preReleaseIdentifiers);
	}

	/**
	 * Converts a version number to a string using the official SemVer format.
	 * The core of a version is MAJOR.MINOR.PATCH, without zero-padding. If
	 * pre-release identifiers are present, they are separated by periods and
	 * added after a '-'. If build metadata is present, it is separated by
	 * periods and added after a '+'. Pre-release identifiers go before version
	 * metadata.
	 * <p>
	 * For example, the version with major number 3, minor number 2, patch number
	 * 1, pre-release identifiers "alpha" and "1" and build metadata "2022-02-19"
	 * has a string representation "3.2.1-alpha.1+2022-02-19".
	 * 
	 * @since v0.4.0
	 * @see <a href="https://semver.org">The official SemVer specification</a>
	 */
	@Override
	public String toString() {
		String versionString = String.format("%d.%d.%d", this.major, this.minor,
				this.patch);
		if (!this.preReleaseIdentifiers.isEmpty()) {
			versionString += "-" + String.join(".", this.preReleaseIdentifiers);
		}
		if (!this.buildMetadata.isEmpty()) {
			versionString += "+" + String.join(".", this.buildMetadata);
		}
		return versionString;
	}
}