import {EscapedValue, escape} from './types.ts'
import {IncorrectInterpolationError} from './Builder.ts'
import ConnectionExecutable from './type/ConnectionExecutable.ts'

/**
 * Query builder base class for a raw SQL statement.
 * @extends ConnectionExecutable
 */
export class Statement<T> extends ConnectionExecutable<T> {
    constructor(
        /**
         * The statement to be executed.
         * @type string
         */
        public statement: string,
        /**
         * The variables to be interpolated into the statement.
         * @type Array<EscapedValue>
         */
        public interpolations: EscapedValue[]
    ) {
        super()
    }

    sql(): string {
        const statement = this.statement
        const interpolations = [...this.interpolations].reverse()
        const expected_interpolations = (statement.match(/\?/g) || []).length
        if ( expected_interpolations !== interpolations.length ) {
            throw new IncorrectInterpolationError(expected_interpolations, interpolations.length)
        }

        const query_chars = []
        for ( const char of statement.split('') ) {
            if ( char === '?' ) {
                const val = interpolations.pop()
                if ( typeof val !== 'undefined' )
                    query_chars.push(escape(val))
                else
                    throw new TypeError('Got an undefined interpolation value. Unable to continue.')
            } else {
                query_chars.push(char)
            }
        }

        return query_chars.join('')
    }
}