/*****************************************************************************
 * Open MCT, Copyright (c) 2014-2021, United States Government
 * as represented by the Administrator of the National Aeronautics and Space
 * Administration. All rights reserved.
 *
 * Open MCT is licensed 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.
 *
 * Open MCT includes source code licensed under additional open source
 * licenses. See the Open Source Licenses file (LICENSES.md) included with
 * this source code distribution or the Licensing information page available
 * at runtime from the About dialog for additional information.
 *****************************************************************************/

import utils from 'objectUtils';
import MutableDomainObject from './MutableDomainObject';
import RootRegistry from './RootRegistry';
import RootObjectProvider from './RootObjectProvider';
import EventEmitter from 'EventEmitter';
import InterceptorRegistry from './InterceptorRegistry';
import Transaction from './Transaction';
import ConflictError from './ConflictError';
import InMemorySearchProvider from './InMemorySearchProvider';

/**
 * Utilities for loading, saving, and manipulating domain objects.
 * @interface ObjectAPI
 * @memberof module:openmct
 */

function ObjectAPI(typeRegistry, openmct) {
    this.openmct = openmct;
    this.typeRegistry = typeRegistry;
    this.eventEmitter = new EventEmitter();
    this.providers = {};
    this.rootRegistry = new RootRegistry(openmct);
    this.inMemorySearchProvider = new InMemorySearchProvider(openmct);

    this.rootProvider = new RootObjectProvider(this.rootRegistry);
    this.cache = {};
    this.interceptorRegistry = new InterceptorRegistry();

    this.SYNCHRONIZED_OBJECT_TYPES = ['notebook', 'plan'];

    this.errors = {
        Conflict: ConflictError
    };
}

/**
 * Set fallback provider, this is an internal API for legacy reasons.
 * @private
 */
ObjectAPI.prototype.supersecretSetFallbackProvider = function (p) {
    this.fallbackProvider = p;
};

/**
 * Retrieve the provider for a given identifier.
 * @private
 */
ObjectAPI.prototype.getProvider = function (identifier) {

    if (identifier.key === 'ROOT') {
        return this.rootProvider;
    }

    return this.providers[identifier.namespace] || this.fallbackProvider;
};

/**
 * Get an active transaction instance
 * @returns {Transaction} a transaction object
 */
ObjectAPI.prototype.getActiveTransaction = function () {
    return this.transaction;
};

/**
 * Get the root-level object.
 * @returns {Promise.<DomainObject>} a promise for the root object
 */
ObjectAPI.prototype.getRoot = function () {
    return this.rootProvider.get();
};

/**
 * Register a new object provider for a particular namespace.
 *
 * @param {string} namespace the namespace for which to provide objects
 * @param {module:openmct.ObjectProvider} provider the provider which
 *        will handle loading domain objects from this namespace
 * @memberof {module:openmct.ObjectAPI#}
 * @name addProvider
 */
ObjectAPI.prototype.addProvider = function (namespace, provider) {
    this.providers[namespace] = provider;
};

/**
 * Provides the ability to read, write, and delete domain objects.
 *
 * When registering a new object provider, all methods on this interface
 * are optional.
 *
 * @interface ObjectProvider
 * @memberof module:openmct
 */

/**
 * Create the given domain object in the corresponding persistence store
 *
 * @method create
 * @memberof module:openmct.ObjectProvider#
 * @param {module:openmct.DomainObject} domainObject the domain object to
 *        create
 * @returns {Promise} a promise which will resolve when the domain object
 *          has been created, or be rejected if it cannot be saved
 */

/**
 * Update this domain object in its persistence store
 *
 * @method update
 * @memberof module:openmct.ObjectProvider#
 * @param {module:openmct.DomainObject} domainObject the domain object to
 *        update
 * @returns {Promise} a promise which will resolve when the domain object
 *          has been updated, or be rejected if it cannot be saved
 */

/**
 * Delete this domain object.
 *
 * @method delete
 * @memberof module:openmct.ObjectProvider#
 * @param {module:openmct.DomainObject} domainObject the domain object to
 *        delete
 * @returns {Promise} a promise which will resolve when the domain object
 *          has been deleted, or be rejected if it cannot be deleted
 */

/**
 * Get a domain object.
 *
 * @method get
 * @memberof module:openmct.ObjectProvider#
 * @param {string} key the key for the domain object to load
 * @param {AbortController.signal} abortSignal (optional) signal to abort fetch requests
 * @returns {Promise} a promise which will resolve when the domain object
 *          has been saved, or be rejected if it cannot be saved
 */

ObjectAPI.prototype.get = function (identifier, abortSignal) {
    let keystring = this.makeKeyString(identifier);

    if (this.cache[keystring] !== undefined) {
        return this.cache[keystring];
    }

    identifier = utils.parseKeyString(identifier);
    let dirtyObject;
    if (this.isTransactionActive()) {
        dirtyObject = this.transaction.getDirtyObject(identifier);
    }

    if (dirtyObject) {
        return Promise.resolve(dirtyObject);
    }

    const provider = this.getProvider(identifier);

    if (!provider) {
        throw new Error('No Provider Matched');
    }

    if (!provider.get) {
        throw new Error('Provider does not support get!');
    }

    let objectPromise = provider.get(identifier, abortSignal).then(result => {
        delete this.cache[keystring];

        result = this.applyGetInterceptors(identifier, result);
        if (result.isMutable) {
            result.$refresh(result);
        } else {
            let mutableDomainObject = this._toMutable(result);
            mutableDomainObject.$refresh(result);
        }

        return result;
    }).catch((result) => {
        console.warn(`Failed to retrieve ${keystring}:`, result);

        delete this.cache[keystring];

        result = this.applyGetInterceptors(identifier);

        return result;
    });

    this.cache[keystring] = objectPromise;

    return objectPromise;
};

/**
 * Search for domain objects.
 *
 * Object providersSearches and combines results of each object provider search.
 * Objects without search provided will have been indexed
 * and will be searched using the fallback in-memory search.
 * Search results are asynchronous and resolve in parallel.
 *
 * @method search
 * @memberof module:openmct.ObjectAPI#
 * @param {string} query the term to search for
 * @param {AbortController.signal} abortSignal (optional) signal to cancel downstream fetch requests
 * @returns {Array.<Promise.<module:openmct.DomainObject>>}
 *          an array of promises returned from each object provider's search function
 *          each resolving to domain objects matching provided search query and options.
 */
ObjectAPI.prototype.search = function (query, abortSignal) {
    const searchPromises = Object.values(this.providers)
        .filter(provider => provider.search !== undefined)
        .map(provider => provider.search(query, abortSignal));
    // abortSignal doesn't seem to be used in generic search?
    searchPromises.push(this.inMemorySearchProvider.query(query, null)
        .then(results => results.hits
            .map(hit => {
                return hit;
            })));

    return searchPromises;
};

/**
 * Will fetch object for the given identifier, returning a version of the object that will automatically keep
 * itself updated as it is mutated. Before using this function, you should ask yourself whether you really need it.
 * The platform will provide mutable objects to views automatically if the underlying object can be mutated. The
 * platform will manage the lifecycle of any mutable objects that it provides. If you use `getMutable` you are
 * committing to managing that lifecycle yourself. `.destroy` should be called when the object is no longer needed.
 *
 * @memberof {module:openmct.ObjectAPI#}
 * @returns {Promise.<MutableDomainObject>} a promise that will resolve with a MutableDomainObject if
 * the object can be mutated.
 */
ObjectAPI.prototype.getMutable = function (identifier) {
    if (!this.supportsMutation(identifier)) {
        throw new Error(`Object "${this.makeKeyString(identifier)}" does not support mutation.`);
    }

    return this.get(identifier).then((object) => {
        return this._toMutable(object);
    });
};

/**
 * This function is for cleaning up a mutable domain object when you're done with it.
 * You only need to use this if you retrieved the object using `getMutable()`. If the object was provided by the
 * platform (eg. passed into a `view()` function) then the platform is responsible for its lifecycle.
 * @param {MutableDomainObject} domainObject
 */
ObjectAPI.prototype.destroyMutable = function (domainObject) {
    if (domainObject.isMutable) {
        return domainObject.$destroy();
    } else {
        throw new Error("Attempted to destroy non-mutable domain object");
    }
};

ObjectAPI.prototype.delete = function () {
    throw new Error('Delete not implemented');
};

ObjectAPI.prototype.isPersistable = function (idOrKeyString) {
    let identifier = utils.parseKeyString(idOrKeyString);
    let provider = this.getProvider(identifier);

    return provider !== undefined
        && provider.create !== undefined
        && provider.update !== undefined;
};

ObjectAPI.prototype.isMissing = function (domainObject) {
    let identifier = utils.makeKeyString(domainObject.identifier);
    let missingName = 'Missing: ' + identifier;

    return domainObject.name === missingName;
};

/**
 * Save this domain object in its current state. EXPERIMENTAL
 *
 * @private
 * @memberof module:openmct.ObjectAPI#
 * @param {module:openmct.DomainObject} domainObject the domain object to
 *        save
 * @returns {Promise} a promise which will resolve when the domain object
 *          has been saved, or be rejected if it cannot be saved
 */
ObjectAPI.prototype.save = function (domainObject) {
    let provider = this.getProvider(domainObject.identifier);
    let savedResolve;
    let savedReject;
    let result;

    if (!this.isPersistable(domainObject.identifier)) {
        result = Promise.reject('Object provider does not support saving');
    } else if (hasAlreadyBeenPersisted(domainObject)) {
        result = Promise.resolve(true);
    } else {
        const persistedTime = Date.now();
        if (domainObject.persisted === undefined) {
            result = new Promise((resolve, reject) => {
                savedResolve = resolve;
                savedReject = reject;
            });
            domainObject.persisted = persistedTime;
            const newObjectPromise = provider.create(domainObject);
            if (newObjectPromise) {
                newObjectPromise.then(response => {
                    this.mutate(domainObject, 'persisted', persistedTime);
                    savedResolve(response);
                }).catch((error) => {
                    savedReject(error);
                });
            } else {
                result = Promise.reject(`[ObjectAPI][save] Object provider returned ${newObjectPromise} when creating new object.`);
            }
        } else {
            domainObject.persisted = persistedTime;
            this.mutate(domainObject, 'persisted', persistedTime);
            result = provider.update(domainObject);
        }
    }

    return result;
};

/**
 * After entering into edit mode, creates a new instance of Transaction to keep track of changes in Objects
 */
ObjectAPI.prototype.startTransaction = function () {
    if (this.isTransactionActive()) {
        throw new Error("Unable to start new Transaction: Previous Transaction is active");
    }

    this.transaction = new Transaction(this);
};

/**
 * Clear instance of Transaction
 */
ObjectAPI.prototype.endTransaction = function () {
    this.transaction = null;
};

/**
 * Add a root-level object.
 * @param {module:openmct.ObjectAPI~Identifier|array|function} identifier an identifier or
 *        an array of identifiers for root level objects, or a function that returns a
 *        promise for an identifier or an array of root level objects.
 * @param {module:openmct.PriorityAPI~priority|Number} priority a number representing
 *        this item(s) position in the root object's composition (example: order in object tree).
 *        For arrays, they are treated as blocks.
 * @method addRoot
 * @memberof module:openmct.ObjectAPI#
 */
ObjectAPI.prototype.addRoot = function (identifier, priority) {
    this.rootRegistry.addRoot(identifier, priority);
};

/**
 * Register an object interceptor that transforms a domain object requested via module:openmct.ObjectAPI.get
 * The domain object will be transformed after it is retrieved from the persistence store
 * The domain object will be transformed only if the interceptor is applicable to that domain object as defined by the InterceptorDef
 *
 * @param {module:openmct.InterceptorDef} interceptorDef the interceptor definition to add
 * @method addGetInterceptor
 * @memberof module:openmct.InterceptorRegistry#
 */
ObjectAPI.prototype.addGetInterceptor = function (interceptorDef) {
    this.interceptorRegistry.addInterceptor(interceptorDef);
};

/**
 * Retrieve the interceptors for a given domain object.
 * @private
 */
ObjectAPI.prototype.listGetInterceptors = function (identifier, object) {
    return this.interceptorRegistry.getInterceptors(identifier, object);
};

/**
 * Inovke interceptors if applicable for a given domain object.
 * @private
 */
ObjectAPI.prototype.applyGetInterceptors = function (identifier, domainObject) {
    const interceptors = this.listGetInterceptors(identifier, domainObject);
    interceptors.forEach(interceptor => {
        domainObject = interceptor.invoke(identifier, domainObject);
    });

    return domainObject;
};

/**
 * Return relative url path from a given object path
 * eg: #/browse/mine/cb56f6bf-c900-43b7-b923-2e3b64b412db/6e89e858-77ce-46e4-a1ad-749240286497/....
 * @param {Array} objectPath
 * @returns {string} relative url for object
 */
ObjectAPI.prototype.getRelativePath = function (objectPath) {
    return objectPath
        .map(p => this.makeKeyString(p.identifier))
        .reverse()
        .join('/')
    ;
};

/**
 * Modify a domain object.
 * @param {module:openmct.DomainObject} object the object to mutate
 * @param {string} path the property to modify
 * @param {*} value the new value for this property
 * @method mutate
 * @memberof module:openmct.ObjectAPI#
 */
ObjectAPI.prototype.mutate = function (domainObject, path, value) {
    if (!this.supportsMutation(domainObject.identifier)) {
        throw `Error: Attempted to mutate immutable object ${domainObject.name}`;
    }

    if (domainObject.isMutable) {
        domainObject.$set(path, value);
    } else {
        //Creating a temporary mutable domain object allows other mutable instances of the
        //object to be kept in sync.
        let mutableDomainObject = this._toMutable(domainObject);

        //Mutate original object
        MutableDomainObject.mutateObject(domainObject, path, value);

        //Mutate temporary mutable object, in the process informing any other mutable instances
        mutableDomainObject.$set(path, value);

        //Destroy temporary mutable object
        this.destroyMutable(mutableDomainObject);
    }

    if (this.isTransactionActive()) {
        this.transaction.add(domainObject);
    } else {
        this.save(domainObject);
    }
};

/**
 * Updates a domain object based on its latest persisted state. Note that this will mutate the provided object.
 * @param {module:openmct.DomainObject} domainObject an object to refresh from its persistence store
 * @returns {Promise} the provided object, updated to reflect the latest persisted state of the object.
 */
ObjectAPI.prototype.refresh = async function (domainObject) {
    const refreshedObject = await this.get(domainObject.identifier);

    if (domainObject.isMutable) {
        domainObject.$refresh(refreshedObject);
    } else {
        utils.refresh(domainObject, refreshedObject);
    }

    return domainObject;
};

/**
 * @private
 */
ObjectAPI.prototype._toMutable = function (object) {
    let mutableObject;

    if (object.isMutable) {
        mutableObject = object;
    } else {
        mutableObject = MutableDomainObject.createMutable(object, this.eventEmitter);

        // Check if provider supports realtime updates
        let identifier = utils.parseKeyString(mutableObject.identifier);
        let provider = this.getProvider(identifier);

        if (provider !== undefined
            && provider.observe !== undefined
            && this.SYNCHRONIZED_OBJECT_TYPES.includes(object.type)) {
            let unobserve = provider.observe(identifier, (updatedModel) => {
                if (updatedModel.persisted > mutableObject.modified) {
                    //Don't replace with a stale model. This can happen on slow connections when multiple mutations happen
                    //in rapid succession and intermediate persistence states are returned by the observe function.
                    updatedModel = this.applyGetInterceptors(identifier, updatedModel);
                    mutableObject.$refresh(updatedModel);
                }
            });
            mutableObject.$on('$_destroy', () => {
                unobserve();
            });
        }
    }

    return mutableObject;
};

/**
 * Updates a domain object based on its latest persisted state. Note that this will mutate the provided object.
 * @param {module:openmct.DomainObject} domainObject an object to refresh from its persistence store
 * @returns {Promise} the provided object, updated to reflect the latest persisted state of the object.
 */
ObjectAPI.prototype.refresh = async function (domainObject) {
    const refreshedObject = await this.get(domainObject.identifier);

    if (domainObject.isMutable) {
        domainObject.$refresh(refreshedObject);
    } else {
        utils.refresh(domainObject, refreshedObject);
    }

    return domainObject;
};

/**
 * @param module:openmct.ObjectAPI~Identifier identifier An object identifier
 * @returns {boolean} true if the object can be mutated, otherwise returns false
 */
ObjectAPI.prototype.supportsMutation = function (identifier) {
    return this.isPersistable(identifier);
};

/**
 * Observe changes to a domain object.
 * @param {module:openmct.DomainObject} object the object to observe
 * @param {string} path the property to observe
 * @param {Function} callback a callback to invoke when new values for
 *        this property are observed
 * @method observe
 * @memberof module:openmct.ObjectAPI#
 */
ObjectAPI.prototype.observe = function (domainObject, path, callback) {
    if (domainObject.isMutable) {
        return domainObject.$observe(path, callback);
    } else {
        let mutable = this._toMutable(domainObject);
        mutable.$observe(path, callback);

        return () => mutable.$destroy();
    }
};

/**
 * @param {module:openmct.ObjectAPI~Identifier} identifier
 * @returns {string} A string representation of the given identifier, including namespace and key
 */
ObjectAPI.prototype.makeKeyString = function (identifier) {
    return utils.makeKeyString(identifier);
};

/**
 * @param {string} keyString A string representation of the given identifier, that is, a namespace and key separated by a colon.
 * @returns {module:openmct.ObjectAPI~Identifier} An identifier object
 */
ObjectAPI.prototype.parseKeyString = function (keyString) {
    return utils.parseKeyString(keyString);
};

/**
 * Given any number of identifiers, will return true if they are all equal, otherwise false.
 * @param {module:openmct.ObjectAPI~Identifier[]} identifiers
 */
ObjectAPI.prototype.areIdsEqual = function (...identifiers) {
    return identifiers.map(utils.parseKeyString)
        .every(identifier => {
            return identifier === identifiers[0]
                || (identifier.namespace === identifiers[0].namespace
                    && identifier.key === identifiers[0].key);
        });
};

ObjectAPI.prototype.getOriginalPath = function (identifier, path = []) {
    return this.get(identifier).then((domainObject) => {
        path.push(domainObject);
        let location = domainObject.location;

        if (location) {
            return this.getOriginalPath(utils.parseKeyString(location), path);
        } else {
            return path;
        }
    });
};

ObjectAPI.prototype.isObjectPathToALink = function (domainObject, objectPath) {
    return objectPath !== undefined
        && objectPath.length > 1
        && domainObject.location !== this.makeKeyString(objectPath[1].identifier);
};

ObjectAPI.prototype.isTransactionActive = function () {
    return Boolean(this.transaction && this.openmct.editor.isEditing());
};

/**
 * Uniquely identifies a domain object.
 *
 * @typedef Identifier
 * @memberof module:openmct.ObjectAPI~
 * @property {string} namespace the namespace to/from which this domain
 *           object should be loaded/stored.
 * @property {string} key a unique identifier for the domain object
 *           within that namespace
 */

/**
 * A domain object is an entity of relevance to a user's workflow, that
 * should appear as a distinct and meaningful object within the user
 * interface. Examples of domain objects are folders, telemetry sensors,
 * and so forth.
 *
 * A few common properties are defined for domain objects. Beyond these,
 * individual types of domain objects may add more as they see fit.
 *
 * @property {module:openmct.ObjectAPI~Identifier} identifier a key/namespace pair which
 *           uniquely identifies this domain object
 * @property {string} type the type of domain object
 * @property {string} name the human-readable name for this domain object
 * @property {string} [creator] the user name of the creator of this domain
 *           object
 * @property {number} [modified] the time, in milliseconds since the UNIX
 *           epoch, at which this domain object was last modified
 * @property {module:openmct.ObjectAPI~Identifier[]} [composition] if
 *           present, this will be used by the default composition provider
 *           to load domain objects
 * @typedef DomainObject
 * @memberof module:openmct
 */

function hasAlreadyBeenPersisted(domainObject) {
    const result = domainObject.persisted !== undefined
        && domainObject.persisted >= domainObject.modified;

    return result;
}

export default ObjectAPI;