import MysqlConnectionManager, {query} from "./MysqlConnectionManager";
import Validator from "./Validator";
import {Connection} from "mysql";
import ModelComponent from "./ModelComponent";
import {Type} from "../Utils";
import ModelFactory from "./ModelFactory";
import ModelRelation from "./ModelRelation";
import ModelQuery, {ModelQueryResult} from "./ModelQuery";
import {Request} from "express";

export default abstract class Model {
    public static select<T extends Model>(this: Type<T>, ...fields: string[]): ModelQuery<T> {
        return ModelFactory.get(this).select(...fields);
    }

    public static update<T extends Model>(this: Type<T>, data: { [key: string]: any }): ModelQuery<T> {
        return ModelFactory.get(this).update(data);
    }

    public static delete<T extends Model>(this: Type<T>): ModelQuery<T> {
        return ModelFactory.get(this).delete();
    }

    public static async getById<T extends Model>(this: Type<T>, ...id: any): Promise<T | null> {
        return ModelFactory.get(this).getById(id);
    }

    public static async paginate<T extends Model>(this: Type<T>, request: Request, perPage: number = 20, query?: ModelQuery<T>): Promise<ModelQueryResult<T>> {
        return ModelFactory.get(this).paginate(request, perPage, query);
    }

    protected readonly _factory: ModelFactory<any>;
    private readonly _components: ModelComponent<any>[] = [];
    private readonly _validators: { [key: string]: Validator<any> } = {};

    [key: string]: any;

    public constructor(factory: ModelFactory<any>) {
        if (!factory || !(factory instanceof ModelFactory)) throw new Error('Cannot instantiate model directly.');
        this._factory = factory;
        this.init();
    }

    protected abstract init(): void;

    protected setValidation<T>(propertyName: keyof this): Validator<T> {
        const validator = new Validator<T>();
        this._validators[propertyName as string] = validator;
        return validator;
    }

    public addComponent(modelComponent: ModelComponent<this>): void {
        modelComponent.init();
        this._components.push(modelComponent);
    }

    public as<T extends ModelComponent<any>>(type: Type<T>): T {
        for (const component of this._components) {
            if (component instanceof type) {
                return <any>this;
            }
        }
        throw new Error(`Component ${type.name} was not initialized for this ${this.constructor.name}.`);
    }

    public updateWithData(data: any) {
        for (const property of this._properties) {
            if (data[property] !== undefined) {
                this[property] = data[property];
            }
        }
    }

    protected async beforeSave(exists: boolean, connection: Connection): Promise<void> {
    }

    protected async afterSave(): Promise<void> {
    }

    public async save(connection?: Connection, postHook?: (callback: () => Promise<void>) => void): Promise<void> {
        await this.validate(false, connection);

        const exists = await this.exists();
        let needs_full_update = false;

        if (connection) {
            needs_full_update = await this.saveTransaction(connection, exists, needs_full_update);
        } else {
            needs_full_update = await MysqlConnectionManager.wrapTransaction(async connection => this.saveTransaction(connection, exists, needs_full_update));
        }

        const callback = async () => {
            if (needs_full_update) {
                this.updateWithData((await this._factory.select().where('id', this.id!).limit(1).execute()).results[0]);
            }

            await this.afterSave();
        };

        if (connection) {
            postHook!(callback);
        } else {
            await callback();
        }
    }

    private async saveTransaction(connection: Connection, exists: boolean, needs_full_update: boolean): Promise<boolean> {
        // Before save
        await this.beforeSave(exists, connection);
        if (exists && this.hasOwnProperty('updated_at')) {
            this.updated_at = new Date();
        }

        const properties = [];
        const values = [];

        if (exists) {
            const data: any = {};
            for (const property of this._properties) {
                const value = this[property];
                if (value !== undefined) {
                    data[property] = value;
                } else {
                    needs_full_update = true;
                }
            }
            let query = this._factory.update(data);
            for (const indexField of this._factory.getPrimaryKeyFields()) {
                query = query.where(indexField, this[indexField]);
            }
            await query.execute(connection);
        } else {
            const props_holders = [];
            for (const property of this._properties) {
                const value = this[property];
                if (value !== undefined) {
                    properties.push(property);
                    props_holders.push('?');
                    values.push(value);
                } else {
                    needs_full_update = true;
                }
            }
            const result = await query(`INSERT INTO ${this.table} (${properties.join(', ')}) VALUES(${props_holders.join(', ')})`, values, connection);

            if (this.hasOwnProperty('id')) this.id = result.other.insertId;
        }

        return needs_full_update;
    }

    public async exists(): Promise<boolean> {
        let query = this._factory.select('1');
        for (const indexField of this._factory.getPrimaryKeyFields()) {
            query = query.where(indexField, this[indexField]);
        }
        return (await query.limit(1).execute()).results.length > 0;
    }

    public async delete(): Promise<void> {
        if (!(await this.exists())) throw new Error('This model instance doesn\'t exist in DB.');

        let query = this._factory.delete();
        for (const indexField of this._factory.getPrimaryKeyFields()) {
            query = query.where(indexField, this[indexField]);
        }
        await query.execute();
    }

    public async validate(onlyFormat: boolean = false, connection?: Connection): Promise<void[]> {
        return await Promise.all(this._properties.map(
            prop => this._validators[prop]?.execute(prop, this[prop], onlyFormat, connection)
        ));
    }

    public get table(): string {
        return this._factory.table;
    }

    private get _properties(): string[] {
        return Object.getOwnPropertyNames(this).filter(p => {
            return !p.startsWith('_') && !(this[p] instanceof ModelRelation);
        });
    }
}

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