// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.config.application.api.xml;

import com.yahoo.config.application.api.DeploymentSpec;
import com.yahoo.config.application.api.DeploymentSpec.DeclaredZone;
import com.yahoo.config.application.api.DeploymentSpec.Delay;
import com.yahoo.config.application.api.DeploymentSpec.ParallelZones;
import com.yahoo.config.application.api.DeploymentSpec.Step;
import com.yahoo.config.application.api.Notifications;
import com.yahoo.config.application.api.Notifications.Role;
import com.yahoo.config.application.api.Notifications.When;
import com.yahoo.config.application.api.TimeWindow;
import com.yahoo.config.provision.AthenzDomain;
import com.yahoo.config.provision.AthenzService;
import com.yahoo.config.provision.Environment;
import com.yahoo.config.provision.RegionName;
import com.yahoo.io.IOUtils;
import com.yahoo.text.XML;
import org.w3c.dom.Element;

import java.io.IOException;
import java.io.Reader;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;

/**
 * @author bratseth
 */
public class DeploymentSpecXmlReader {

    private static final String majorVersionTag = "major-version";
    private static final String testTag = "test";
    private static final String stagingTag = "staging";
    private static final String blockChangeTag = "block-change";
    private static final String prodTag = "prod";
    
    private final boolean validate;
    
    /** Creates a validating reader */
    public DeploymentSpecXmlReader() {
        this(true);
    }

    /** 
     * Creates a reader 
     * 
     * @param validate true to validate the input, false to accept any input which can be unabiguously parsed
     */
    public DeploymentSpecXmlReader(boolean validate) {
        this.validate = validate;
    }

    public DeploymentSpec read(Reader reader) {
        try {
            return read(IOUtils.readAll(reader));
        }
        catch (IOException e) {
            throw new IllegalArgumentException("Could not read deployment spec", e);
        }
    }

    /** Reads a deployment spec from XML */
    public DeploymentSpec read(String xmlForm) {
        List<Step> steps = new ArrayList<>();
        Optional<String> globalServiceId = Optional.empty();
        Element root = XML.getDocument(xmlForm).getDocumentElement();
        if (validate)
            validateTagOrder(root);
        for (Element environmentTag : XML.getChildren(root)) {
            if ( ! isEnvironmentName(environmentTag.getTagName())) continue;

            Environment environment = Environment.from(environmentTag.getTagName());

            if (environment == Environment.prod) {
                for (Element stepTag : XML.getChildren(environmentTag)) {
                    Optional<AthenzService> athenzService = stringAttribute("athenz-service", environmentTag).map(AthenzService::from);
                    if (stepTag.getTagName().equals("delay")) {
                        steps.add(new Delay(Duration.ofSeconds(longAttribute("hours", stepTag) * 60 * 60 +
                                                               longAttribute("minutes", stepTag) * 60 +
                                                               longAttribute("seconds", stepTag))));
                    } else if (stepTag.getTagName().equals("parallel")) {
                        List<DeclaredZone> zones = new ArrayList<>();
                        for (Element regionTag : XML.getChildren(stepTag)) {
                            zones.add(readDeclaredZone(environment, athenzService, regionTag));
                        }
                        steps.add(new ParallelZones(zones));
                    } else { // a region: deploy step
                        steps.add(readDeclaredZone(environment, athenzService, stepTag));
                    }
                }
            } else {
                steps.add(new DeclaredZone(environment));
            }

            if (environment == Environment.prod)
                globalServiceId = readGlobalServiceId(environmentTag);
            else if (readGlobalServiceId(environmentTag).isPresent())
                throw new IllegalArgumentException("Attribute 'global-service-id' is only valid on 'prod' tag.");

        }
        Optional<AthenzDomain> athenzDomain = stringAttribute("athenz-domain", root).map(AthenzDomain::from);
        Optional<AthenzService> athenzService = stringAttribute("athenz-service", root).map(AthenzService::from);
        return new DeploymentSpec(globalServiceId,
                                  readUpgradePolicy(root),
                                  optionalIntegerAttribute(majorVersionTag, root),
                                  readChangeBlockers(root),
                                  steps,
                                  xmlForm,
                                  athenzDomain,
                                  athenzService,
                                  readNotifications(root));
    }

    private Notifications readNotifications(Element root) {
        Element notificationsElement = XML.getChild(root, "notifications");
        if (notificationsElement == null)
            return Notifications.none();

        When defaultWhen = stringAttribute("when", notificationsElement).map(When::fromValue).orElse(When.failingCommit);
        Map<When, List<String>> emailAddresses = new HashMap<>();
        Map<When, List<Role>> emailRoles = new HashMap<>();
        for (When when : When.values()) {
            emailAddresses.put(when, new ArrayList<>());
            emailRoles.put(when, new ArrayList<>());
        }

        for (Element emailElement : XML.getChildren(notificationsElement, "email")) {
            Optional<String> addressAttribute = stringAttribute("address", emailElement);
            Optional<Role> roleAttribute = stringAttribute("role", emailElement).map(Role::fromValue);
            When when = stringAttribute("when", emailElement).map(When::fromValue).orElse(defaultWhen);
            if (addressAttribute.isPresent() == roleAttribute.isPresent())
                throw new IllegalArgumentException("Exactly one of 'role' and 'address' must be present in 'email' elements.");

            addressAttribute.ifPresent(address -> emailAddresses.get(when).add(address));
            roleAttribute.ifPresent(role -> emailRoles.get(when).add(role));
        }
        return Notifications.of(emailAddresses, emailRoles);
    }

    /** Imposes some constraints on tag order which are not expressible in the schema */
    private void validateTagOrder(Element root) {
        List<String> tags = XML.getChildren(root).stream().map(Element::getTagName).collect(Collectors.toList());
        for (int i = 0; i < tags.size(); i++) {
            if (tags.get(i).equals(blockChangeTag)) {
                String constraint = "<block-change> must be placed after <test> and <staging> and before <prod>";
                if (containsAfter(i, testTag, tags)) throw new IllegalArgumentException(constraint);
                if (containsAfter(i, stagingTag, tags)) throw new IllegalArgumentException(constraint);
                if (containsBefore(i, prodTag, tags)) throw new IllegalArgumentException(constraint);
            }
        }
    }
    
    private boolean containsAfter(int i, String item, List<String> items) {
        return items.subList(i+1, items.size()).contains(item);
    }

    private boolean containsBefore(int i, String item, List<String> items) {
        return items.subList(0, i).contains(item);
    }

    /** Returns the given attribute as an integer, or 0 if it is not present */
    private long longAttribute(String attributeName, Element tag) {
        String value = tag.getAttribute(attributeName);
        if (value == null || value.isEmpty()) return 0;
        try {
            return Long.parseLong(value);
        }
        catch (NumberFormatException e) {
            throw new IllegalArgumentException("Expected an integer for attribute '" + attributeName +
                                               "' but got '" + value + "'");
        }
    }

    /** Returns the given attribute as an integer, or 0 if it is not present */
    private Optional<Integer> optionalIntegerAttribute(String attributeName, Element tag) {
        String value = tag.getAttribute(attributeName);
        if (value == null || value.isEmpty()) return Optional.empty();
        try {
            return Optional.of(Integer.parseInt(value));
        }
        catch (NumberFormatException e) {
            throw new IllegalArgumentException("Expected an integer for attribute '" + attributeName +
                                               "' but got '" + value + "'");
        }
    }

    /** Returns the given attribute as a string, or Optional.empty if it is not present or empty */
    private Optional<String> stringAttribute(String attributeName, Element tag) {
        String value = tag.getAttribute(attributeName);
        return Optional.ofNullable(value).filter(s -> ! s.equals(""));
    }

    private boolean isEnvironmentName(String tagName) {
        return tagName.equals(testTag) || tagName.equals(stagingTag) || tagName.equals(prodTag);
    }

    private DeclaredZone readDeclaredZone(Environment environment, Optional<AthenzService> athenzService, Element regionTag) {
        return new DeclaredZone(environment, Optional.of(RegionName.from(XML.getValue(regionTag).trim())),
                                readActive(regionTag), athenzService);
    }

    private Optional<String> readGlobalServiceId(Element environmentTag) {
        String globalServiceId = environmentTag.getAttribute("global-service-id");
        if (globalServiceId == null || globalServiceId.isEmpty()) {
            return Optional.empty();
        }
        else {
            return Optional.of(globalServiceId);
        }
    }

    private List<DeploymentSpec.ChangeBlocker> readChangeBlockers(Element root) {
        List<DeploymentSpec.ChangeBlocker> changeBlockers = new ArrayList<>();
        for (Element tag : XML.getChildren(root)) {
            // TODO: Remove block-upgrade on Vespa 7
            if ( ! blockChangeTag.equals(tag.getTagName()) && !"block-upgrade".equals(tag.getTagName())) continue;

            boolean blockVersions = tag.getTagName().equals("block-upgrade") || //  TODO: Remove condition on Vespa 7
                                    trueOrMissing(tag.getAttribute("version"));
            boolean blockRevisions = trueOrMissing(tag.getAttribute("revision"))
                                     && !tag.getTagName().equals("block-upgrade"); //  TODO: Remove condition on Vespa 7

            String daySpec = tag.getAttribute("days");
            String hourSpec = tag.getAttribute("hours");
            String zoneSpec = tag.getAttribute("time-zone");
            if (zoneSpec.isEmpty()) { // Default to UTC time zone
                zoneSpec = "UTC";
            }
            changeBlockers.add(new DeploymentSpec.ChangeBlocker(blockRevisions, blockVersions,
                                                                TimeWindow.from(daySpec, hourSpec, zoneSpec)));
        }
        return Collections.unmodifiableList(changeBlockers);
    }

    /** Returns true if the given value is "true", or if it is missing */
    private boolean trueOrMissing(String value) {
        return value == null || value.isEmpty() || value.equals("true");
    }

    private DeploymentSpec.UpgradePolicy readUpgradePolicy(Element root) {
        Element upgradeElement = XML.getChild(root, "upgrade");
        if (upgradeElement == null) return DeploymentSpec.UpgradePolicy.defaultPolicy;

        String policy = upgradeElement.getAttribute("policy");
        switch (policy) {
            case "canary" : return DeploymentSpec.UpgradePolicy.canary;
            case "default" : return DeploymentSpec.UpgradePolicy.defaultPolicy;
            case "conservative" : return DeploymentSpec.UpgradePolicy.conservative;
            default : throw new IllegalArgumentException("Illegal upgrade policy '" + policy + "': " +
                                                         "Must be one of " + Arrays.toString(DeploymentSpec.UpgradePolicy.values()));
        }
    }

    private boolean readActive(Element regionTag) {
        String activeValue = regionTag.getAttribute("active");
        if ("true".equals(activeValue)) return true;
        if ("false".equals(activeValue)) return false;
        throw new IllegalArgumentException("Region tags must have an 'active' attribute set to 'true' or 'false' " +
                                           "to control whether the region should receive production traffic");
    }

}