manager.ts

import {
  compareWithOriginal,
  getPrimaryKeyInfo,
  getRelationValues,
  getTableName,
  getValues,
  isSaved,
  mapValueProperties,
  setSaved,
} from "./utils/models.ts";
import type { Adapter } from "./adapters/adapter.ts";
import { range } from "./utils/number.ts";
import { RelationType } from "./model.ts";
import { ModelQuery } from "./modelquery.ts";
import { Q } from "./q.ts";

/**
 * Same as Partial<T> but goes deeper and makes Partial<T> all its properties and sub-properties.
 */
export type DeepPartial<T> = {
  [P in keyof T]?: T[P] extends Array<infer U> ? Array<DeepPartial<U>>
    : T[P] extends ReadonlyArray<infer U> ? ReadonlyArray<DeepPartial<U>>
    : DeepPartial<T[P]>;
};

/**
 * Query options to find a single record.
 */
export interface FindOneOptions<T> {
  where?: DeepPartial<T>;
  includes?: string[];
}

/**
 * Query options to find multiple records.
 */
export type FindOptions<T> = FindOneOptions<T> & {
  limit?: number;
  offset?: number;
};

/**
 * Manager allows you to perform queries to your model.
 */
export class Manager {
  /**
   * Create a model manager.
   * 
   * @param adapter the database adapter to perform queries
   */
  constructor(private adapter: Adapter) {}

  /**
   * Query a model.
   * 
   * @param modelClass the model you want to query
   */
  public query<T extends Object>(modelClass: { new (): T }): ModelQuery<T> {
    return new ModelQuery(modelClass, this.adapter);
  }

  /**
   * Save model a instance to the database.
   *
   * @param model the model you want to save
   */
  public async save<T extends Object>(model: T): Promise<T>;

  /**
   * Save model instances to the database.
   *
   * @param models the models you want to save
   */
  public async save<T extends Object>(models: T[]): Promise<T[]>;

  /**
   * Save model instance to the database.
   *
   * @param model the model you want to save
   */
  public async save<T extends Object>(model: T | T[]): Promise<T | T[]> {
    // If an Array of models is passed, perform INSERT in bulk.
    // Otherwise, check if the model is already saved to the
    // database or not. If it is, perform update instead of
    if (Array.isArray(model)) {
      // We wrap everything in transaction, this will undo every
      // changes in the database if one of the queries fail.
      await this.adapter.transaction(async () => {
        // We need to group the models by it's constructor first
        // in order to perform bulk insert.
        for (const [key, value] of this.groupModels(model)) {
          const insert: T[] = [];

          // If one of the models is already saved, perform UPDATE.
          for (const data of value) {
            !data.isSaved
              ? insert.push(data.model)
              : await this.update(data.model);
          }

          await this.bulkInsert(key, insert);
        }
      });
    } else {
      // If the record is saved, we assume that the user want to update the record.
      // Otherwise, create a new record to the database.
      isSaved(model)
        ? await this.update(model)
        : await this.bulkInsert(model.constructor, [model]);
    }

    return model;
  }

  /**
   * Remove given model instance from the database.
   * 
   * @param model the model you want to remove.
   */
  public async remove<T extends Object>(model: T): Promise<T>;

  /**
   * Remove given model instaces from the database.
   * 
   * @param model the model you want to remove.
   */
  public async remove<T extends Object>(model: T[]): Promise<T[]>;

  /**
   * Remove given model from the database.
   * 
   * @param model the model you want to remove.
   */
  public async remove<T extends Object>(model: T | T[]): Promise<T | T[]> {
    if (Array.isArray(model)) {
      // Just like save, wrap everything in transaction. This will undo
      // every changes in the database if one of the queries fail.
      await this.adapter.transaction(async () => {
        for (const [key, value] of this.groupModels(model).entries()) {
          const tableName = getTableName(key);
          const primaryKeyInfo = getPrimaryKeyInfo(key);

          // Holds the primary keys of the models to delete.
          const ids: number[] = [];

          // Holds the model instances to clear it's original values.
          const models: T[] = [];

          // Only delete saved models.
          for (const item of value) {
            if (item.isSaved) {
              ids.push((item.model as any)[primaryKeyInfo.propertyKey]);
              models.push(item.model);
            }
          }

          // Perform bulk delete.
          await this.adapter
            .table(tableName)
            .where(primaryKeyInfo.name, Q.in(ids))
            .delete()
            .execute();

          // Set the `isSaved` value to be false on each models
          // and remove their original values.
          for (const item of models) {
            delete (item as any)[primaryKeyInfo.propertyKey];
            setSaved(item, false);
          }
        }
      });
    } else {
      const tableName = getTableName(model.constructor);
      const primaryKeyInfo = getPrimaryKeyInfo(model.constructor);

      // Only remove model if it's already saved
      if (isSaved(model)) {
        const id = (model as any)[primaryKeyInfo.propertyKey];
        await this.adapter
          .table(tableName)
          .where(primaryKeyInfo.name, id)
          .delete()
          .execute();

        // Remove the primary key
        delete (model as any)[primaryKeyInfo.propertyKey];

        // Set the `isSaved` value to be false and remove the original values
        setSaved(model, false);
      }
    }

    return model;
  }

  /**
   * Perform update to a model.
   * 
   * @param model the model you want to update.
   */
  private async update<T extends Object>(model: T): Promise<T> {
    const tableName = getTableName(model.constructor);
    const primaryKeyInfo = getPrimaryKeyInfo(model.constructor);
    const { isDirty, diff } = compareWithOriginal(model);

    if (isDirty) {
      await this.adapter
        .table(tableName)
        .where(
          primaryKeyInfo.name,
          (model as any)[primaryKeyInfo.propertyKey],
        )
        .update(diff)
        .execute();

      // Save the model's original values
      setSaved(model, true);
    }

    return model;
  }

  /**
   * Group models by its constructor.
   */
  private groupModels<T extends Object>(models: T[]) {
    return models.reduce((prev, next, index) => {
      const previousModels = prev.get(next.constructor);
      const data = { model: next, index, isSaved: isSaved(next) };
      prev.set(
        next.constructor,
        previousModels ? previousModels.concat(data) : [data],
      );
      return prev;
    }, new Map<Function, { model: T; index: number; isSaved: boolean }[]>());
  }

  /**
   * Insert multiple records to the database efficiently
   */
  private async bulkInsert<T extends Object>(
    modelClass: Function,
    models: T[],
  ): Promise<T[]> {
    const tableName = getTableName(modelClass);
    const primaryKeyInfo = getPrimaryKeyInfo(modelClass);

    // Get all model values
    const values = models.map((model) => {
      const values = getValues(model);

      // If there's a belongs to relationship, add it to the INSERT statement
      for (const relation of getRelationValues(model)) {
        if (relation.description.type === RelationType.BelongsTo) {
          values[relation.description.targetColumn] = relation.value as number;
        }
      }

      return values;
    });

    // Execute query
    const query = this.adapter.table(tableName).insert(values);

    // The postgres adapter doesn't have any equivalient `lastInsertedId` property.
    // So, we need to manually return the primary key.
    if (this.adapter.dialect === "postgres") {
      query.returning(primaryKeyInfo.name);
    }

    // Execute the query
    const result = await query.execute();

    // Get last inserted id
    const lastInsertedId = this.adapter.dialect === "postgres"
      ? result[result.length - 1][primaryKeyInfo.name] as number
      : this.adapter.lastInsertedId;

    // Set the model primary keys
    const ids = range(
      lastInsertedId + 1 - models.length,
      lastInsertedId,
    );

    // Assign values to the models
    for (const [index, model] of models.entries()) {
      // Get the models values that has been sent to the database
      // and map column names from `name` to `propertyKey`.
      const value = mapValueProperties(
        model.constructor,
        values[index],
        "propertyKey",
      );

      // Set the primary key
      value[primaryKeyInfo.propertyKey] = ids[index];

      // Populate empty properties with default value
      Object.assign(model, value);

      // If there's a has many relationship, update the foreign key
      for (const relation of getRelationValues(model)) {
        if (relation.description.type === RelationType.HasMany) {
          const ids = relation.value as number[];
          const tableName = getTableName(relation.description.getModel());
          const relationPkInfo = getPrimaryKeyInfo(
            relation.description.getModel(),
          );

          await this.adapter
            .table(tableName)
            .update({
              [relation.description.targetColumn]:
                (model as any)[primaryKeyInfo.propertyKey],
            })
            .where(relationPkInfo.name, Q.in(ids))
            .execute();

          for (let i = 0; i < ids.length; i++) {
            (model as any)[relation.description.propertyKey][i][
              relation.description.targetColumn
            ] = (model as any)[primaryKeyInfo.propertyKey];
          }
        }
      }

      // Update the `isSaved` status and save the original values
      setSaved(model, true);
    }

    return models;
  }
}