import { Knex } from 'knex';
import { SchemaInspector } from '../types/schema-inspector';
import { Table } from '../types/table';
import { Column } from '../types/column';
import { ForeignKey } from '../types/foreign-key';
import { stripQuotes } from '../utils/strip-quotes';

type RawTable = {
  TABLE_NAME: string;
  TABLE_SCHEMA: string;
  TABLE_COMMENT: string | null;
  ENGINE: string;
  TABLE_COLLATION: string;
};

type RawColumn = {
  TABLE_NAME: string;
  COLUMN_NAME: string;
  COLUMN_DEFAULT: any | null;
  COLUMN_TYPE: string;
  CHARACTER_MAXIMUM_LENGTH: number | null;
  NUMERIC_PRECISION: number | null;
  NUMERIC_SCALE: number | null;
  IS_NULLABLE: 'YES' | 'NO';
  COLLATION_NAME: string | null;
  COLUMN_COMMENT: string | null;
  REFERENCED_TABLE_NAME: string | null;
  REFERENCED_COLUMN_NAME: string | null;
  UPDATE_RULE: string | null;
  DELETE_RULE: string | null;
  COLUMN_KEY: 'PRI' | 'UNI' | null;
  EXTRA: 'auto_increment' | 'STORED GENERATED' | 'VIRTUAL GENERATED' | null;
  CONSTRAINT_NAME: 'PRIMARY' | null;
  GENERATION_EXPRESSION: string;
};

export function rawColumnToColumn(rawColumn: RawColumn): Column {
  let dataType = rawColumn.COLUMN_TYPE.replace(/\(.*?\)/, '');
  if (rawColumn.COLUMN_TYPE.startsWith('tinyint(1)')) {
    dataType = 'boolean';
  }

  return {
    name: rawColumn.COLUMN_NAME,
    table: rawColumn.TABLE_NAME,
    data_type: dataType,
    default_value: parseDefaultValue(rawColumn.COLUMN_DEFAULT),
    generation_expression: rawColumn.GENERATION_EXPRESSION || null,
    max_length: rawColumn.CHARACTER_MAXIMUM_LENGTH,
    numeric_precision: rawColumn.NUMERIC_PRECISION,
    numeric_scale: rawColumn.NUMERIC_SCALE,
    is_generated: !!rawColumn.EXTRA?.endsWith('GENERATED'),
    is_nullable: rawColumn.IS_NULLABLE === 'YES',
    is_unique: rawColumn.COLUMN_KEY === 'UNI',
    is_primary_key:
      rawColumn.CONSTRAINT_NAME === 'PRIMARY' || rawColumn.COLUMN_KEY === 'PRI',
    has_auto_increment: rawColumn.EXTRA === 'auto_increment',
    foreign_key_column: rawColumn.REFERENCED_COLUMN_NAME,
    foreign_key_table: rawColumn.REFERENCED_TABLE_NAME,
    comment: rawColumn.COLUMN_COMMENT,
  };
}

export function parseDefaultValue(value: string | null) {
  if (value === null || value.trim().toLowerCase() === 'null') return null;

  return stripQuotes(value);
}

export default class MySQL implements SchemaInspector {
  knex: Knex;

  constructor(knex: Knex) {
    this.knex = knex;
  }

  // Tables
  // ===============================================================================================

  /**
   * List all existing tables in the current schema/database
   */
  async tables() {
    const records = await this.knex
      .select<{ TABLE_NAME: string }[]>('TABLE_NAME')
      .from('INFORMATION_SCHEMA.TABLES')
      .where({
        TABLE_TYPE: 'BASE TABLE',
        TABLE_SCHEMA: this.knex.client.database(),
      });
    return records.map(({ TABLE_NAME }) => TABLE_NAME);
  }

  /**
   * Get the table info for a given table. If table parameter is undefined, it will return all tables
   * in the current schema/database
   */
  tableInfo(): Promise<Table[]>;
  tableInfo(table: string): Promise<Table>;
  async tableInfo<T>(table?: string) {
    const query = this.knex
      .select(
        'TABLE_NAME',
        'ENGINE',
        'TABLE_SCHEMA',
        'TABLE_COLLATION',
        'TABLE_COMMENT'
      )
      .from('information_schema.tables')
      .where({
        table_schema: this.knex.client.database(),
        table_type: 'BASE TABLE',
      });

    if (table) {
      const rawTable: RawTable = await query
        .andWhere({ table_name: table })
        .first();

      return {
        name: rawTable.TABLE_NAME,
        schema: rawTable.TABLE_SCHEMA,
        comment: rawTable.TABLE_COMMENT,
        collation: rawTable.TABLE_COLLATION,
        engine: rawTable.ENGINE,
      } as T extends string ? Table : Table[];
    }

    const records: RawTable[] = await query;

    return records.map((rawTable): Table => {
      return {
        name: rawTable.TABLE_NAME,
        schema: rawTable.TABLE_SCHEMA,
        comment: rawTable.TABLE_COMMENT,
        collation: rawTable.TABLE_COLLATION,
        engine: rawTable.ENGINE,
      };
    }) as T extends string ? Table : Table[];
  }

  /**
   * Check if a table exists in the current schema/database
   */
  async hasTable(table: string): Promise<boolean> {
    const result = await this.knex
      .count<{ count: 0 | 1 }>({ count: '*' })
      .from('information_schema.tables')
      .where({
        table_schema: this.knex.client.database(),
        table_name: table,
      })
      .first();
    return (result && result.count === 1) || false;
  }

  // Columns
  // ===============================================================================================

  /**
   * Get all the available columns in the current schema/database. Can be filtered to a specific table
   */
  async columns(table?: string) {
    const query = this.knex
      .select<{ TABLE_NAME: string; COLUMN_NAME: string }[]>(
        'TABLE_NAME',
        'COLUMN_NAME'
      )
      .from('INFORMATION_SCHEMA.COLUMNS')
      .where({ TABLE_SCHEMA: this.knex.client.database() });

    if (table) {
      query.andWhere({ TABLE_NAME: table });
    }

    const records = await query;

    return records.map(({ TABLE_NAME, COLUMN_NAME }) => ({
      table: TABLE_NAME,
      column: COLUMN_NAME,
    }));
  }

  /**
   * Get the column info for all columns, columns in a given table, or a specific column.
   */
  columnInfo(): Promise<Column[]>;
  columnInfo(table: string): Promise<Column[]>;
  columnInfo(table: string, column: string): Promise<Column>;
  async columnInfo<T>(table?: string, column?: string) {
    const query = this.knex
      .select(
        'c.TABLE_NAME',
        'c.COLUMN_NAME',
        'c.COLUMN_DEFAULT',
        'c.COLUMN_TYPE',
        'c.CHARACTER_MAXIMUM_LENGTH',
        'c.IS_NULLABLE',
        'c.COLUMN_KEY',
        'c.EXTRA',
        'c.COLLATION_NAME',
        'c.COLUMN_COMMENT',
        'c.NUMERIC_PRECISION',
        'c.NUMERIC_SCALE',
        'c.GENERATION_EXPRESSION',
        'fk.REFERENCED_TABLE_NAME',
        'fk.REFERENCED_COLUMN_NAME',
        'fk.CONSTRAINT_NAME',
        'rc.UPDATE_RULE',
        'rc.DELETE_RULE',
        'rc.MATCH_OPTION'
      )
      .from('INFORMATION_SCHEMA.COLUMNS as c')
      .leftJoin('INFORMATION_SCHEMA.KEY_COLUMN_USAGE as fk', function () {
        this.on('c.TABLE_NAME', '=', 'fk.TABLE_NAME')
          .andOn('fk.COLUMN_NAME', '=', 'c.COLUMN_NAME')
          .andOn('fk.CONSTRAINT_SCHEMA', '=', 'c.TABLE_SCHEMA');
      })
      .leftJoin(
        'INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS as rc',
        function () {
          this.on('rc.TABLE_NAME', '=', 'fk.TABLE_NAME')
            .andOn('rc.CONSTRAINT_NAME', '=', 'fk.CONSTRAINT_NAME')
            .andOn('rc.CONSTRAINT_SCHEMA', '=', 'fk.CONSTRAINT_SCHEMA');
        }
      )
      .where({
        'c.TABLE_SCHEMA': this.knex.client.database(),
      });

    if (table) {
      query.andWhere({ 'c.TABLE_NAME': table });
    }

    if (column) {
      const rawColumn: RawColumn = await query
        .andWhere({ 'c.column_name': column })
        .first();

      return rawColumnToColumn(rawColumn);
    }

    const records: RawColumn[] = await query;

    return records
      .map(rawColumnToColumn)
      .sort((column) => +!column.foreign_key_column)
      .filter((column, index, records) => {
        const first = records.findIndex((_column) => {
          return column.name === _column.name && column.table === _column.table;
        });
        return first === index;
      });
  }

  /**
   * Check if a table exists in the current schema/database
   */
  async hasColumn(table: string, column: string): Promise<boolean> {
    const result = await this.knex
      .count<{ count: 0 | 1 }>('*', { as: 'count' })
      .from('information_schema.columns')
      .where({
        table_schema: this.knex.client.database(),
        table_name: table,
        column_name: column,
      })
      .first();
    return !!(result && result.count);
  }

  /**
   * Get the primary key column for the given table
   */
  async primary(table: string) {
    const results = await this.knex.raw(
      `SHOW KEYS FROM ?? WHERE Key_name = 'PRIMARY'`,
      table
    );

    if (results && results.length && results[0].length) {
      return results[0][0]['Column_name'] as string;
    }

    return null;
  }

  // Foreign Keys
  // ===============================================================================================

  async foreignKeys(table?: string) {
    const query = this.knex
      .select(
        `rc.TABLE_NAME AS table`,
        `kcu.COLUMN_NAME AS column`,
        `rc.REFERENCED_TABLE_NAME AS foreign_key_table`,
        `kcu.REFERENCED_COLUMN_NAME AS foreign_key_column`,
        `rc.CONSTRAINT_NAME AS constraint_name`,
        `rc.UPDATE_RULE AS on_update`,
        `rc.DELETE_RULE AS on_delete`
      )
      .from(`information_schema.referential_constraints AS rc`)
      .leftJoin(`information_schema.key_column_usage AS kcu `, function () {
        this.on(`rc.CONSTRAINT_NAME`, `=`, `kcu.CONSTRAINT_NAME`).andOn(
          `kcu.CONSTRAINT_SCHEMA`,
          `=`,
          `rc.CONSTRAINT_SCHEMA`
        );
      })
      .where({
        'rc.CONSTRAINT_SCHEMA': this.knex.client.database(),
      });
    if (table) {
      query.andWhere({ 'rc.TABLE_NAME': table });
    }
    const result: ForeignKey[] = await query;
    return result;
  }
}