daton/lib/src/http/kernel/module/ApplyRouteHandlers.ts

import Module from '../Module.ts'
import {Injectable} from '../../../../../di/src/decorator/Injection.ts'
import Kernel from '../Kernel.ts'
import {Logging} from '../../../service/logging/Logging.ts'
import {Request} from '../../Request.ts'
import ResponseFactory from '../../response/ResponseFactory.ts'
import {http, error} from '../../response/helpers.ts'
import {HTTPStatus} from '../../../const/http.ts'

@Injectable()
export default class ApplyRouteHandlers extends Module {
    public static register(kernel: Kernel) {
        kernel.register(this).core()
    }

    constructor(
        protected readonly logger: Logging,
    ) {
        super()
    }

    public async apply(request: Request): Promise<Request> {
        if ( !request.route ) { // Route not found
            const factory = http(HTTPStatus.NOT_FOUND)
            return await factory.write(request)
        }

        if ( !Array.isArray(request.route.handlers) ) { // Route found but invalid HTTP method
            const factory = http(HTTPStatus.METHOD_NOT_ALLOWED)
            return await factory.write(request)
        }

        if ( request.route.handlers.length < 1 ) { // Route and method found, but no handlers
            const factory = http(HTTPStatus.NOT_IMPLEMENTED)
            return await factory.write(request)
        }

        let current_request: Request = request
        for ( const handler of request.route.handlers ) {
            try {
                const result = await handler(current_request)
                if ( result instanceof Request ) {
                    // If we got a request instance back, use that for further handlers
                    current_request = result
                } else if ( result instanceof ResponseFactory ) {
                    // If we got a response factory back, write the response and move along
                    return await result.write(current_request)
                }
            } catch (e) {
                this.logger.error('Error encountered while applying request handlers!')
                this.logger.error(e)

                // TODO determine response type (html | json, &c.)
                const factory = error(e)
                return await factory.write(request)
            }
        }

        return current_request
    }
}