export type ErrorMessage = string

export type ErrorMessages = ErrorMessage[]

export type FieldErrorMessages = {
	[field: string]: ErrorMessages
}

export type SimpleFieldErrorMessages = {
	[field: string]: ErrorMessage | ErrorMessages
}

export interface ErrorOptions {
	label?: string | null
}

export class ValidationError extends Error {
	messages?: ErrorMessages
	errors?: FieldErrorMessages
	opts: ErrorOptions

	constructor(
		arg: ErrorMessage | ErrorMessages | SimpleFieldErrorMessages,
		opts?: Partial<ErrorOptions>
	) {
		let message: ErrorMessage | undefined
		let messages: ErrorMessages | undefined
		let errors: FieldErrorMessages | undefined

		if (typeof arg === "string") {
			messages = [arg]
			message = arg
		} else if (Array.isArray(arg)) {
			if (!arg.length) {
				throw new Error("ValidationError array argument can't empty.")
			}
			for (const i in arg) {
				const e = arg[i]
				if (!(typeof e === "string")) {
					throw new Error(
						`ValidationError array element ${i} must be a string.`
					)
				}
			}
			messages = arg
			message = JSON.stringify(messages)
		} else if (typeof arg === "object") {
			if (!Object.keys(arg).length) {
				throw new Error("ValidationError object argument can't be empty.")
			}
			errors = {}
			for (const field of Object.keys(arg)) {
				const fieldArg = arg[field]
				if (typeof fieldArg === "string") {
					errors[field] = [fieldArg]
				} else if (Array.isArray(fieldArg)) {
					if (!fieldArg.length) {
						throw new Error(
							`ValidationError field ${field} can't be empty array.`
						)
					}
					for (const i in fieldArg) {
						const e = fieldArg[i]
						if (!(typeof e === "string")) {
							throw new Error(
								`ValidationError field ${field} array element ${i} must be a string.`
							)
						}
					}
					errors[field] = fieldArg
				} else {
					throw new Error(
						`ValidationError field ${field} must be a string or array.`
					)
				}
			}
			message = JSON.stringify(errors)
		} else {
			throw new Error(
				"ValidationError argument must be a string, array or object."
			)
		}
		super(message)
		this.messages = messages
		this.errors = errors
		this.opts = { ...opts }
	}
}