/**
 * Base type for an API response format.
 */
import {BaseSerializer, Event, ObjectSerializer} from '../../support/bus'
import {Awaitable, ErrorWithContext, hasOwnProperty, JSONState, uuid4} from '../../util'

export interface APIResponse<T> {
    eventName?: string,
    eventUuid?: string,
    success: boolean,
    message?: string,
    data?: T,
    error?: {
        name: string,
        message: string,
        stack?: string[],
    }
}

export function isAPIResponse(what: unknown): what is APIResponse<unknown> {
    return typeof what === 'object' && what !== null
        && hasOwnProperty(what, 'success')
        && typeof what.success === 'boolean'
        && (!hasOwnProperty(what, 'message') || typeof what.message === 'string')
        && (!hasOwnProperty(what, 'error') || (
            typeof what.error === 'object' && what.error !== null
                && hasOwnProperty(what.error, 'name') && typeof what.error.name === 'string'
                && hasOwnProperty(what.error, 'message') && typeof what.error.message === 'string'
                && (!hasOwnProperty(what.error, 'stack') || (
                    Array.isArray(what.error.stack) && what.error.stack.every(x => typeof x === 'string')
                )
                )
        )
        )
}

export function apiEvent<T>(response: APIResponse<T>): APIResponse<T> & Event {
    if ( !response.eventName ) {
        response.eventName = '@extollo/lib:APIResponse'
    }

    if ( !response.eventUuid ) {
        response.eventUuid = uuid4()
    }

    return response as APIResponse<T> & Event
}

/**
 * Serializer implementation that can encode/decode APIResponse objects.
 */
@ObjectSerializer()
export class APIResponseSerializer extends BaseSerializer<APIResponse<unknown>, JSONState> {
    protected decodeSerial(serial: JSONState): Awaitable<APIResponse<unknown>> {
        if ( isAPIResponse(serial) ) {
            return serial
        }

        throw new ErrorWithContext('Could not decode API response: object is malformed')
    }

    protected encodeActual(actual: APIResponse<unknown>): Awaitable<JSONState> {
        return actual as unknown as JSONState
    }

    protected getName(): string {
        return '@extollo/lib:APIResponseSerializer'
    }

    matchActual(some: APIResponse<unknown>): boolean {
        return isAPIResponse(some)
    }
}

/**
 * Formats a mesage as a successful API response.
 * @param {string} displayMessage
 * @return APIResponse
 */
export function message(displayMessage: string): APIResponse<void> {
    return {
        success: true,
        message: displayMessage,
    }
}

/**
 * Formats a single record as a successful API response.
 * @param record
 * @return APIResponse
 */
export function one<T>(record: T): APIResponse<T> {
    return {
        success: true,
        data: record,
    }
}

/**
 * Formats an array of records as a successful API response.
 * @param {array} records
 * @return APIResponse
 */
export function many<T>(records: T[]): APIResponse<{records: T[], total: number}> {
    return {
        success: true,
        data: {
            records,
            total: records.length,
        },
    }
}

/**
 * Formats an error message or Error instance as an API response.
 * @return APIResponse
 * @param thrownError
 */
export function error(thrownError: string | Error): APIResponse<undefined> {
    if ( typeof thrownError === 'string' ) {
        return {
            success: false,
            message: thrownError,
        }
    } else {
        return {
            success: false,
            message: thrownError.message,
            error: {
                name: thrownError.name,
                message: thrownError.message,
                stack: thrownError.stack ? thrownError.stack.split(/\s+at\s+/).slice(1) : [],
            },
        }
    }
}