import {deepClone, diffObject, expandObject, flattenObject, getType, isEmpty, mergeObject} from "../utils/helpers.mjs";
import {
  DataField,
  SchemaField,
  EmbeddedDataField,
  EmbeddedCollectionField,
  ObjectField,
  TypeDataField, EmbeddedDocumentField
} from "../data/fields.mjs";
import {DataModelValidationFailure} from "../data/validation-failure.mjs";

/**
 * @typedef {Record<string, DataField>}  DataSchema
 */

/**
 * @typedef {Object} DataValidationOptions
 * @property {boolean} [strict=true]     Throw an error if validation fails.
 * @property {boolean} [fallback=false]  Attempt to replace invalid values with valid defaults?
 * @property {boolean} [partial=false]   Allow partial source data, ignoring absent fields?
 * @property {boolean} [dropInvalidEmbedded=false]  If true, invalid embedded documents will emit a warning and be
 *                                                  placed in the invalidDocuments collection rather than causing the
 *                                                  parent to be considered invalid.
 */

/**
 * The abstract base class which defines the data schema contained within a Document.
 * @param {object} [data={}]                    Initial data used to construct the data object. The provided object
 *                                              will be owned by the constructed model instance and may be mutated.
 * @param {DataValidationOptions} [options={}]  Options which affect DataModel construction
 * @param {Document} [options.parent]           A parent DataModel instance to which this DataModel belongs
 * @abstract
 */
export default class DataModel {
  constructor(data={}, {parent=null, strict=true, ...options}={}) {

    // Parent model
    Object.defineProperty(this, "parent", {
      value: (() => {
        if ( parent === null ) return null;
        if ( parent instanceof DataModel ) return parent;
        throw new Error("The provided parent must be a DataModel instance");
      })(),
      writable: false,
      enumerable: false
    });

    // Source data
    Object.defineProperty(this, "_source", {
      value: this._initializeSource(data, {strict, ...options}),
      writable: false,
      enumerable: false
    });
    Object.seal(this._source);

    // Additional subclass configurations
    this._configure(options);

    // Data validation and initialization
    const fallback = options.fallback ?? !strict;
    const dropInvalidEmbedded = options.dropInvalidEmbedded ?? !strict;
    this.validate({strict, fallback, dropInvalidEmbedded, fields: true, joint: true});
    this._initialize({strict, ...options});
  }

  /**
   * Configure the data model instance before validation and initialization workflows are performed.
   * @protected
   */
  _configure(options={}) {}

  /* -------------------------------------------- */

  /**
   * The source data object for this DataModel instance.
   * Once constructed, the source object is sealed such that no keys may be added nor removed.
   * @type {object}
   */
  _source;

  /**
   * The defined and cached Data Schema for all instances of this DataModel.
   * @type {SchemaField}
   * @private
   */
  static _schema;

  /**
   * An immutable reverse-reference to a parent DataModel to which this model belongs.
   * @type {DataModel|null}
   */
  parent;

  /* ---------------------------------------- */
  /*  Data Schema                             */
  /* ---------------------------------------- */

  /**
   * Define the data schema for documents of this type.
   * The schema is populated the first time it is accessed and cached for future reuse.
   * @virtual
   * @returns {DataSchema}
   */
  static defineSchema() {
    throw new Error(`The ${this["name"]} subclass of DataModel must define its Document schema`);
  }

  /* ---------------------------------------- */

  /**
   * The Data Schema for all instances of this DataModel.
   * @type {SchemaField}
   */
  static get schema() {
    if ( this.hasOwnProperty("_schema") ) return this._schema;
    const schema = new SchemaField(Object.freeze(this.defineSchema()));
    Object.defineProperty(this, "_schema", {value: schema, writable: false});
    return schema;
  }

  /* ---------------------------------------- */

  /**
   * Define the data schema for this document instance.
   * @type {SchemaField}
   */
  get schema() {
    return this.constructor.schema;
  }

  /* ---------------------------------------- */

  /**
   * Is the current state of this DataModel invalid?
   * The model is invalid if there is any unresolved failure.
   * @type {boolean}
   */
  get invalid() {
    return Object.values(this.#validationFailures).some(f => f?.unresolved);
  }

  /**
   * An array of validation failure instances which may have occurred when this instance was last validated.
   * @type {{fields: DataModelValidationFailure|null, joint: DataModelValidationFailure|null}}
   */
  get validationFailures() {
    return this.#validationFailures;
  }

  #validationFailures = Object.seal({fields: null, joint: null });

  /**
   * A set of localization prefix paths which are used by this DataModel.
   * @type {string[]}
   */
  static LOCALIZATION_PREFIXES = [];

  /* ---------------------------------------- */
  /*  Data Cleaning Methods                   */
  /* ---------------------------------------- */

  /**
   * Initialize the source data for a new DataModel instance.
   * One-time migrations and initial cleaning operations are applied to the source data.
   * @param {object|DataModel} data   The candidate source data from which the model will be constructed
   * @param {object} [options]        Options provided to the model constructor
   * @returns {object}                Migrated and cleaned source data which will be stored to the model instance
   * @protected
   */
  _initializeSource(data, options={}) {
    if ( data instanceof DataModel ) data = data.toObject();
    const dt = getType(data);
    if ( dt !== "Object" ) {
      logger.error(`${this.constructor.name} was incorrectly constructed with a ${dt} instead of an object. 
      Attempting to fall back to default values.`)
      data = {};
    }
    data = this.constructor.migrateDataSafe(data);    // Migrate old data to the new format
    data = this.constructor.cleanData(data);          // Clean the data in the new format
    return this.constructor.shimData(data);           // Apply shims which preserve backwards compatibility
  }

  /* ---------------------------------------- */

  /**
   * Clean a data source object to conform to a specific provided schema.
   * @param {object} [source]         The source data object
   * @param {object} [options={}]     Additional options which are passed to field cleaning methods
   * @returns {object}                The cleaned source data
   */
  static cleanData(source={}, options={}) {
    return this.schema.clean(source, options);
  }

  /* ---------------------------------------- */
  /*  Data Initialization                     */
  /* ---------------------------------------- */

  /**
   * A generator that orders the DataFields in the DataSchema into an expected initialization order.
   * @returns {Generator<[string,DataField]>}
   * @protected
   */
  static *_initializationOrder() {
    for ( const entry of this.schema.entries() ) yield entry;
  }

  /* ---------------------------------------- */

  /**
   * Initialize the instance by copying data from the source object to instance attributes.
   * This mirrors the workflow of SchemaField#initialize but with some added functionality.
   * @param {object} [options]        Options provided to the model constructor
   * @protected
   */
  _initialize(options={}) {
    for ( let [name, field] of this.constructor._initializationOrder() ) {
      const sourceValue = this._source[name];

      // Field initialization
      const value = field.initialize(sourceValue, this, options);

      // Special handling for Document IDs.
      if ( (name === "_id") && (!Object.getOwnPropertyDescriptor(this, "_id") || (this._id === null)) ) {
        Object.defineProperty(this, name, {value, writable: false, configurable: true});
      }

      // Readonly fields
      else if ( field.readonly ) {
        if ( this[name] !== undefined ) continue;
        Object.defineProperty(this, name, {value, writable: false});
      }

      // Getter fields
      else if ( value instanceof Function ) {
        Object.defineProperty(this, name, {get: value, set() {}, configurable: true});
      }

      // Writable fields
      else this[name] = value;
    }
  }

  /* ---------------------------------------- */

  /**
   * Reset the state of this data instance back to mirror the contained source data, erasing any changes.
   */
  reset() {
    this._initialize();
  }

  /* ---------------------------------------- */

  /**
   * Clone a model, creating a new data model by combining current data with provided overrides.
   * @param {Object} [data={}]                    Additional data which overrides current document data at the time of creation
   * @param {object} [context={}]                 Context options passed to the data model constructor
   * @returns {Document|Promise<Document>}        The cloned Document instance
   */
  clone(data={}, context={}) {
    data = mergeObject(this.toObject(), data, {insertKeys: false, performDeletions: true, inplace: true});
    return new this.constructor(data, {parent: this.parent, ...context});
  }

  /* ---------------------------------------- */
  /*  Data Validation Methods                 */
  /* ---------------------------------------- */

  /**
   * Validate the data contained in the document to check for type and content
   * This function throws an error if data within the document is not valid
   *
   * @param {object} options                    Optional parameters which customize how validation occurs.
   * @param {object} [options.changes]          A specific set of proposed changes to validate, rather than the full
   *                                            source data of the model.
   * @param {boolean} [options.clean=false]     If changes are provided, attempt to clean the changes before validating
   *                                            them?
   * @param {boolean} [options.fallback=false]  Allow replacement of invalid values with valid defaults?
   * @param {boolean} [options.dropInvalidEmbedded=false]  If true, invalid embedded documents will emit a warning and
   *                                                       be placed in the invalidDocuments collection rather than
   *                                                       causing the parent to be considered invalid.
   * @param {boolean} [options.strict=true]     Throw if an invalid value is encountered, otherwise log a warning?
   * @param {boolean} [options.fields=true]     Perform validation on individual fields?
   * @param {boolean} [options.joint]           Perform joint validation on the full data model?
   *                                            Joint validation will be performed by default if no changes are passed.
   *                                            Joint validation will be disabled by default if changes are passed.
   *                                            Joint validation can be performed on a complete set of changes (for
   *                                            example testing a complete data model) by explicitly passing true.
   * @return {boolean}                          An indicator for whether the document contains valid data
   */
  validate({changes, clean=false, fallback=false, dropInvalidEmbedded=false, strict=true, fields=true, joint}={}) {
    const source = changes ?? this._source;
    this.#validationFailures.fields = this.#validationFailures.joint = null; // Remove any prior failures

    // Determine whether we are performing partial or joint validation
    const partial = !!changes;
    joint = joint ?? !changes;
    if ( partial && joint ) {
      throw new Error("It is not supported to perform joint data model validation with only a subset of changes");
    }

    // Optionally clean the data before validating
    if ( partial && clean ) this.constructor.cleanData(source, {partial});

    // Validate individual fields in the data or in a specific change-set, throwing errors if validation fails
    if ( fields ) {
      const failure = this.schema.validate(source, {partial, fallback, dropInvalidEmbedded});
      if ( failure ) {
        const id = this._source._id ? `[${this._source._id}] ` : "";
        failure.message = `${this.constructor.name} ${id}validation errors:`;
        this.#validationFailures.fields = failure;
        if ( strict && failure.unresolved ) throw failure.asError();
        else logger.warn(failure.asError());
      }
    }

    // Perform joint document-level validations which consider all fields together
    if ( joint ) {
      try {
        this.schema._validateModel(source);     // Validate inner models
        this.constructor.validateJoint(source); // Validate this model
      } catch (err) {
        const id = this._source._id ? `[${this._source._id}] ` : "";
        const message = [this.constructor.name, id, `Joint Validation Error:\n${err.message}`].filterJoin(" ");
        const failure = new DataModelValidationFailure({message, unresolved: true});
        this.#validationFailures.joint = failure;
        if ( strict ) throw failure.asError();
        else logger.warn(failure.asError());
      }
    }
    return !this.invalid;
  }

  /* ---------------------------------------- */

  /**
   * Evaluate joint validation rules which apply validation conditions across multiple fields of the model.
   * Field-specific validation rules should be defined as part of the DataSchema for the model.
   * This method allows for testing aggregate rules which impose requirements on the overall model.
   * @param {object} data     Candidate data for the model
   * @throws                  An error if a validation failure is detected
   */
  static validateJoint(data) {
    /**
     * @deprecated since v11
     * @ignore
     */
    if ( this.prototype._validateModel instanceof Function ) {
      const msg = `${this.name} defines ${this.name}.prototype._validateModel instance method which should now be`
                + ` declared as ${this.name}.validateJoint static method.`
      foundry.utils.logCompatibilityWarning(msg, {from: 11, until: 13});
      return this.prototype._validateModel.call(this, data);
    }
  }

  /* ---------------------------------------- */
  /*  Data Management                         */
  /* ---------------------------------------- */

  /**
   * Update the DataModel locally by applying an object of changes to its source data.
   * The provided changes are cleaned, validated, and stored to the source data object for this model.
   * The source data is then re-initialized to apply those changes to the prepared data.
   * The method returns an object of differential changes which modified the original data.
   *
   * @param {object} changes          New values which should be applied to the data model
   * @param {object} [options={}]     Options which determine how the new data is merged
   * @returns {object}                An object containing the changed keys and values
   */
  updateSource(changes={}, options={}) {
    const schema = this.schema;
    const source = this._source;
    const _diff = {};
    const _backup = {};
    const _collections = this.collections;
    const _singletons = this.singletons;

    // Expand the object, if dot-notation keys are provided
    if ( Object.keys(changes).some(k => /\./.test(k)) ) changes = expandObject(changes);

    // Clean and validate the provided changes, throwing an error if any change is invalid
    this.validate({changes, clean: true, fallback: options.fallback, strict: true, fields: true, joint: false});

    // Update the source data for all fields and validate the final combined model
    let error;
    try {
      DataModel.#updateData(schema, source, changes, {_backup, _collections, _singletons, _diff, ...options});
      this.validate({fields: this.invalid, joint: true, strict: true});
    } catch(err) {
      error = err;
    }

    // Restore the backup data
    if ( error || options.dryRun ) {
      mergeObject(this._source, _backup, { recursive: false });
      if ( error ) throw error;
    }

    // Initialize the updated data
    if ( !options.dryRun ) this._initialize();
    return _diff;
  }

  /* ---------------------------------------- */

  /**
   * Update the source data for a specific DataSchema.
   * This method assumes that both source and changes are valid objects.
   * @param {SchemaField} schema      The data schema to update
   * @param {object} source           Source data to be updated
   * @param {object} changes          Changes to apply to the source data
   * @param {object} [options={}]     Options which modify the update workflow
   * @returns {object}                The updated source data
   * @throws                          An error if the update operation was unsuccessful
   * @private
   */
  static #updateData(schema, source, changes, options) {
    const {_backup, _diff} = options;
    for ( let [name, value] of Object.entries(changes) ) {
      const field = schema.get(name);
      if ( !field ) continue;

      // Skip updates where the data is unchanged
      const prior = source[name];
      if ( (value?.equals instanceof Function) && value.equals(prior) ) continue;  // Arrays, Sets, etc...
      if ( (prior === value) ) continue; // Direct comparison
      _backup[name] = deepClone(prior);
      _diff[name] = value;

      // Field-specific updating logic
      this.#updateField(name, field, source, value, options);
    }
    return source;
  }

  /* ---------------------------------------- */

  /**
   * Update the source data for a specific DataField.
   * @param {string} name             The field name being updated
   * @param {DataField} field         The field definition being updated
   * @param {object} source           The source object being updated
   * @param {*} value                 The new value for the field
   * @param {object} options          Options which modify the update workflow
   * @throws                          An error if the new candidate value is invalid
   * @private
   */
  static #updateField(name, field, source, value, options) {
    const {dryRun, fallback, recursive, restoreDelta, _collections, _singletons, _diff, _backup} = options;
    let current = source?.[name];   // The current value may be null or undefined

    // Special Case: Update Embedded Collection
    if ( field instanceof EmbeddedCollectionField ) {
      _backup[name] = current;
      if ( !dryRun ) _collections[name].update(value, {fallback, recursive, restoreDelta});
      return;
    }

    // Special Case: Update Embedded Document
    if ( (field instanceof EmbeddedDocumentField) && _singletons[name] ) {
      _diff[name] = _singletons[name].updateSource(value ?? {}, {dryRun, fallback, recursive, restoreDelta});
      if ( isEmpty(_diff[name]) ) delete _diff[name];
      return;
    }

    // Special Case: Inner Data Schema
    let innerSchema;
    if ( (field instanceof SchemaField) || (field instanceof EmbeddedDataField) ) innerSchema = field;
    else if ( field instanceof TypeDataField ) {
      const cls = field.getModelForType(source.type);
      if ( cls ) {
        innerSchema = cls.schema;
        if ( dryRun ) {
          _backup[name] = current;
          current = deepClone(current);
        }
      }
    }
    if ( innerSchema && current && value ) {
      _diff[name] = {};
      const recursiveOptions = {fallback, recursive, _backup: current, _collections, _diff: _diff[name]};
      this.#updateData(innerSchema, current, value, recursiveOptions);
      if ( isEmpty(_diff[name]) ) delete _diff[name];
    }

    // Special Case: Object Field
    else if ( (field instanceof ObjectField) && current && value && (recursive !== false) ) {
      _diff[name] = diffObject(current, value);
      mergeObject(current, value, {insertKeys: true, insertValues: true, performDeletions: true});
      if ( isEmpty(_diff[name]) ) delete _diff[name];
    }

    // Standard Case: Update Directly
    else source[name] = value;
  }

  /* ---------------------------------------- */
  /*  Serialization and Storage               */
  /* ---------------------------------------- */

  /**
   * Copy and transform the DataModel into a plain object.
   * Draw the values of the extracted object from the data source (by default) otherwise from its transformed values.
   * @param {boolean} [source=true]     Draw values from the underlying data source rather than transformed values
   * @returns {object}                  The extracted primitive object
   */
  toObject(source=true) {
    if ( source ) return deepClone(this._source);

    // We have use the schema of the class instead of the schema of the instance to prevent an infinite recursion:
    // the EmbeddedDataField replaces the schema of its model instance with itself
    // and EmbeddedDataField#toObject calls DataModel#toObject.
    return this.constructor.schema.toObject(this);
  }

  /* ---------------------------------------- */

  /**
   * Extract the source data for the DataModel into a simple object format that can be serialized.
   * @returns {object}          The document source data expressed as a plain object
   */
  toJSON() {
    return this.toObject(true);
  }

  /* -------------------------------------------- */

  /**
   * Create a new instance of this DataModel from a source record.
   * The source is presumed to be trustworthy and is not strictly validated.
   * @param {object} source                    Initial document data which comes from a trusted source.
   * @param {DocumentConstructionContext & DataValidationOptions} [context]  Model construction context
   * @param {boolean} [context.strict=false]   Models created from trusted source data are validated non-strictly
   * @returns {DataModel}
   */
  static fromSource(source, {strict=false, ...context}={}) {
    return new this(source, {strict, ...context});
  }

  /* ---------------------------------------- */

  /**
   * Create a DataModel instance using a provided serialized JSON string.
   * @param {string} json       Serialized document data in string format
   * @returns {DataModel}       A constructed data model instance
   */
  static fromJSON(json) {
    return this.fromSource(JSON.parse(json))
  }

  /* -------------------------------------------- */
  /*  Deprecations and Compatibility              */
  /* -------------------------------------------- */

  /**
   * Migrate candidate source data for this DataModel which may require initial cleaning or transformations.
   * @param {object} source           The candidate source data from which the model will be constructed
   * @returns {object}                Migrated source data, if necessary
   */
  static migrateData(source) {
    if ( !source ) return source;
    this.schema.migrateSource(source, source);
    return source;
  }

  /* ---------------------------------------- */

  /**
   * Wrap data migration in a try/catch which attempts it safely
   * @param {object} source           The candidate source data from which the model will be constructed
   * @returns {object}                Migrated source data, if necessary
   */
  static migrateDataSafe(source) {
    try {
      this.migrateData(source);
    } catch(err) {
      err.message = `Failed data migration for ${this.name}: ${err.message}`;
      logger.warn(err);
    }
    return source;
  }

  /* ---------------------------------------- */

  /**
   * Take data which conforms to the current data schema and add backwards-compatible accessors to it in order to
   * support older code which uses this data.
   * @param {object} data         Data which matches the current schema
   * @param {object} [options={}] Additional shimming options
   * @param {boolean} [options.embedded=true] Apply shims to embedded models?
   * @returns {object}            Data with added backwards-compatible properties
   */
  static shimData(data, {embedded=true}={}) {
    if ( Object.isSealed(data) ) return data;
    const schema = this.schema;
    if ( embedded ) {
      for ( const [name, value] of Object.entries(data) ) {
        const field = schema.get(name);
        if ( (field instanceof EmbeddedDataField) && !Object.isSealed(value) ) {
          data[name] = field.model.shimData(value || {});
        }
        else if ( field instanceof EmbeddedCollectionField ) {
          for ( const d of (value || []) ) {
            if ( !Object.isSealed(d) ) field.model.shimData(d)
          }
        }
      }
    }
    return data;
  }
}

export {DataModel};