import {query, QueryResult} from "./MysqlConnectionManager";
import {Connection} from "mysql";

export default class Query {
    public static select(table: string, ...fields: string[]): Query {
        return new Query(QueryType.SELECT, table, fields.length > 0 ? fields : ['*']);
    }

    public static update(table: string, data: {
        [key: string]: any
    }): Query {
        const fields = [];
        for (let key in data) {
            if (data.hasOwnProperty(key)) {
                fields.push(new UpdateFieldValue(key, data[key], false));
            }
        }
        return new Query(QueryType.UPDATE, table, fields);
    }

    public static delete(table: string): Query {
        return new Query(QueryType.DELETE, table);
    }

    private readonly type: QueryType;
    private readonly table: string;
    private readonly fields: (string | SelectFieldValue | UpdateFieldValue)[];
    private _leftJoin?: string;
    private _leftJoinOn: WhereFieldValue[] = [];
    private _where: WhereFieldValue[] = [];
    private _limit?: number;
    private _offset?: number;
    private _sortBy?: string;
    private _sortDirection?: 'ASC' | 'DESC';
    private _foundRows: boolean = false;

    private constructor(type: QueryType, table: string, fields?: (string | SelectFieldValue | UpdateFieldValue)[]) {
        this.type = type;
        this.table = table;
        this.fields = fields || [];
    }

    public leftJoin(table: string): this {
        this._leftJoin = table;
        return this;
    }

    public on(field1: string, field2: string, test: WhereTest = WhereTest.EQ, operator: WhereOperator = WhereOperator.AND): this {
        this._leftJoinOn.push(new WhereFieldValue(field1, field2, true, test, operator));
        return this;
    }

    public where(field: string, value: string | Date | Query | any, test: WhereTest = WhereTest.EQ, operator: WhereOperator = WhereOperator.AND): this {
        this._where.push(new WhereFieldValue(field, value, false, test, operator));
        return this;
    }

    public limit(limit: number, offset: number = 0): this {
        this._limit = limit;
        this._offset = offset;
        return this;
    }

    public first(): this {
        return this.limit(1);
    }

    public sortBy(field: string, direction: 'ASC' | 'DESC' = 'ASC'): this {
        this._sortBy = field;
        this._sortDirection = direction;
        return this;
    }

    public withTotalRowCount(): this {
        this._foundRows = true;
        return this;
    }

    public toString(final: boolean = false): string {
        let query = '';

        let fields = this.fields?.join(',');

        let join = '';
        if (this._leftJoin) {
            join = `LEFT JOIN ${this._leftJoin} ON ${this._leftJoinOn[0]}`;
            for (let i = 1; i < this._leftJoinOn.length; i++) {
                join += this._leftJoinOn[i].toString(false);
            }
        }

        let where = '';
        if (this._where.length > 0) {
            where = `WHERE ${this._where[0]}`;
            for (let i = 1; i < this._where.length; i++) {
                where += this._where[i].toString(false);
            }
        }

        let limit = '';
        if (typeof this._limit === 'number') {
            limit = `LIMIT ${this._limit}`;
            if (typeof this._offset === 'number' && this._offset !== 0) {
                limit += ` OFFSET ${this._offset}`;
            }
        }

        let orderBy = '';
        if (typeof this._sortBy === 'string') {
            orderBy = `ORDER BY ${this._sortBy} ${this._sortDirection}`;
        }

        switch (this.type) {
            case QueryType.SELECT:
                query = `SELECT ${this._foundRows ? 'SQL_CALC_FOUND_ROWS' : ''} ${fields} FROM ${this.table} ${join} ${where} ${orderBy} ${limit}`;
                break;
            case QueryType.UPDATE:
                query = `UPDATE ${this.table} SET ${fields} ${where} ${orderBy} ${limit}`;
                break;
            case QueryType.DELETE:
                query = `DELETE FROM ${this.table} ${where} ${orderBy} ${limit}`;
                break;

        }

        return final ? query : `(${query})`;
    }

    public build(): string {
        return this.toString(true);
    }

    public get variables(): any[] {
        const variables: any[] = [];
        this.fields?.filter(v => v instanceof FieldValue)
            .flatMap(v => (<FieldValue>v).variables)
            .forEach(v => variables.push(v));
        this._where.flatMap(v => v.variables)
            .forEach(v => variables.push(v));
        return variables;
    }

    public isCacheable(): boolean {
        return this.type === QueryType.SELECT && this.fields.length === 1 && this.fields[0] === '*';
    }

    public async execute(connection?: Connection): Promise<QueryResult> {
        const queryResult = await query(this.build(), this.variables, connection);
        if (this._foundRows) {
            const foundRows = await query('SELECT FOUND_ROWS() as r', undefined, connection);
            queryResult.foundRows = foundRows.results[0].r;
        }
        return queryResult;
    }
}

export enum QueryType {
    SELECT,
    UPDATE,
    DELETE,
}

export enum WhereOperator {
    AND = 'AND',
    OR = 'OR',
}

export enum WhereTest {
    EQ = '=',
    NE = '!=',
    GT = '>',
    GE = '>=',
    LT = '<',
    LE = '<=',
    IN = ' IN ',
}

class FieldValue {
    protected readonly field: string;
    protected value: any;
    protected raw: boolean;

    constructor(field: string, value: any, raw: boolean) {
        this.field = field;
        this.value = value;
        this.raw = raw;
    }

    public toString(first: boolean = true): string {
        return `${!first ? ',' : ''}${this.field}${this.test}${this.raw || this.value instanceof Query ? this.value : (Array.isArray(this.value) ? '(?)' : '?')}`;
    }

    protected get test(): string {
        return '=';
    }

    public get variables(): any[] {
        return this.value instanceof Query ? this.value.variables : [this.value];
    }
}

class SelectFieldValue extends FieldValue {
    public toString(first: boolean = true): string {
        return `(${this.value instanceof Query ? this.value : '?'}) AS ${this.field}`;
    }
}

class UpdateFieldValue extends FieldValue {
}

class WhereFieldValue extends FieldValue {
    private readonly _test: WhereTest;
    private readonly operator: WhereOperator;

    constructor(field: string, value: any, raw: boolean, test: WhereTest, operator: WhereOperator) {
        super(field, value, raw);
        this._test = test;
        this.operator = operator;
    }

    public toString(first: boolean = true): string {
        return (!first ? ` ${this.operator} ` : '') + super.toString(true);
    }

    protected get test(): string {
        return this._test;
    }
}