/*
 * VM-Operator
 * Copyright (C) 2024 Michael N. Lipp
 * 
 * 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 org.jdrupes.vmoperator.common;

import java.time.Duration;
import java.time.Instant;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import org.jdrupes.vmoperator.common.VmDefinition.Assignment;
import org.jdrupes.vmoperator.common.VmDefinition.Grant;
import org.jdrupes.vmoperator.common.VmDefinition.Permission;
import org.jdrupes.vmoperator.util.DataPath;

/**
 * Represents a VM pool.
 */
public class VmPool {

    private final String name;
    private String retention;
    private boolean loginOnAssignment;
    private boolean defined;
    private List<Grant> permissions = Collections.emptyList();
    private final Set<String> vms
        = Collections.synchronizedSet(new HashSet<>());

    /**
     * Instantiates a new vm pool.
     *
     * @param name the name
     */
    public VmPool(String name) {
        this.name = name;
    }

    /**
     * Fill the properties of a provisionally created pool from
     * the definition.
     *
     * @param definition the definition
     */
    public void defineFrom(VmPool definition) {
        retention = definition.retention();
        permissions = definition.permissions();
        loginOnAssignment = definition.loginOnAssignment();
        defined = true;
    }

    /**
     * Returns the name.
     *
     * @return the name
     */
    public String name() {
        return name;
    }

    /**
     * Checks if is login on assignment.
     *
     * @return the loginOnAssignment
     */
    public boolean loginOnAssignment() {
        return loginOnAssignment;
    }

    /**
     * Checks if is defined.
     *
     * @return the result
     */
    public boolean isDefined() {
        return defined;
    }

    /**
     * Marks the pool as undefined.
     */
    public void setUndefined() {
        defined = false;
    }

    /**
     * Gets the retention.
     *
     * @return the retention
     */
    public String retention() {
        return retention;
    }

    /**
     * Permissions granted for a VM from the pool.
     *
     * @return the permissions
     */
    public List<Grant> permissions() {
        return permissions;
    }

    /**
     * Returns the VM names.
     *
     * @return the vms
     */
    public Set<String> vms() {
        return vms;
    }

    /**
     * Collect all permissions for the given user with the given roles.
     *
     * @param user the user
     * @param roles the roles
     * @return the sets the
     */
    public Set<Permission> permissionsFor(String user,
            Collection<String> roles) {
        return permissions.stream()
            .filter(g -> DataPath.get(g, "user").map(u -> u.equals(user))
                .orElse(false)
                || DataPath.get(g, "role").map(roles::contains).orElse(false))
            .map(g -> DataPath.<Set<Permission>> get(g, "may")
                .orElse(Collections.emptySet()).stream())
            .flatMap(Function.identity()).collect(Collectors.toSet());
    }

    /**
     * Checks if the given VM belongs to the pool and is not in use.
     *
     * @param vmDef the vm def
     * @return true, if is assignable
     */
    @SuppressWarnings("PMD.SimplifyBooleanReturns")
    public boolean isAssignable(VmDefinition vmDef) {
        // Check if the VM is in the pool
        if (!vmDef.pools().contains(name)) {
            return false;
        }

        // Check if the VM is not in use
        if (vmDef.consoleConnected()) {
            return false;
        }

        // If not assigned, it's usable
        if (vmDef.assignment().isEmpty()) {
            return true;
        }

        // Check if it is to be retained
        if (vmDef.assignment().map(Assignment::lastUsed).map(this::retainUntil)
            .map(ru -> Instant.now().isBefore(ru)).orElse(false)) {
            return false;
        }

        // Additional check in case lastUsed has not been updated
        // by PoolMonitor#onVmResourceChanged() yet ("race condition")
        if (vmDef.condition("ConsoleConnected")
            .map(cc -> cc.getLastTransitionTime().toInstant())
            .map(this::retainUntil)
            .map(ru -> Instant.now().isBefore(ru)).orElse(false)) {
            return false;
        }
        return true;
    }

    /**
     * Return the instant until which an assignment should be retained.
     *
     * @param lastUsed the last used
     * @return the instant
     */
    public Instant retainUntil(Instant lastUsed) {
        if (retention.startsWith("P")) {
            return lastUsed.plus(Duration.parse(retention));
        }
        return Instant.parse(retention);
    }

    /**
     * To string.
     *
     * @return the string
     */
    @Override
    @SuppressWarnings({ "PMD.AvoidLiteralsInIfCondition",
        "PMD.AvoidSynchronizedStatement" })
    public String toString() {
        StringBuilder builder = new StringBuilder(50);
        builder.append("VmPool [name=").append(name).append(", permissions=")
            .append(permissions).append(", vms=");
        if (vms.size() <= 3) {
            builder.append(vms);
        } else {
            synchronized (vms) {
                builder.append('[').append(vms.stream().limit(3)
                    .map(s -> s + ",").collect(Collectors.joining()))
                    .append("...]");
            }
        }
        builder.append(']');
        return builder.toString();
    }
}