import type {
    RumEvent,
    RumEventDomainContext,
    RumInitConfiguration,
    RumResourceEventDomainContext,
} from '@datadog/browser-rum';
import type { ApplicationBeforeSendHandler, ServiceBeforeSendHandler } from './before-send';
import { enrichEvent } from './enrich-event';
import { handleResource } from './handle-resource';
import type { State } from './types';

function applyBuiltIn(event: RumEvent, context: RumEventDomainContext): void {
    if (event.type === 'resource') {
        handleResource(event, context as RumResourceEventDomainContext);
    }
    enrichEvent(event, context);
}

function callApplicationHandler(
    handler: ApplicationBeforeSendHandler,
    event: RumEvent,
    context: RumEventDomainContext
): boolean {
    try {
        return handler(event, context) !== false;
    } catch {
        return true;
    }
}

function callServiceHandler(
    handler: ServiceBeforeSendHandler,
    event: RumEvent,
    context: RumEventDomainContext
): void {
    try {
        handler(event, context);
    } catch {
        // Fail-open: a service handler may not drop or block events.
    }
}

function applyApplication(state: State, event: RumEvent, context: RumEventDomainContext): boolean {
    if (state.applicationBeforeSend) {
        return callApplicationHandler(state.applicationBeforeSend, event, context);
    }
    return true;
}

function applyServiceSpecific(state: State, event: RumEvent, context: RumEventDomainContext): void {
    const serviceKey = event.service;
    if (!serviceKey) {
        return;
    }
    const entry = state.services.get(serviceKey);
    if (!entry) {
        return;
    }
    if (entry.beforeSend) {
        callServiceHandler(entry.beforeSend, event, context);
    }
    if (entry.context) {
        event.context = { ...event.context, ...entry.context };
    }
}

export function buildBeforeSend(state: State): NonNullable<RumInitConfiguration['beforeSend']> {
    return function (event: RumEvent, context: RumEventDomainContext) {
        try {
            applyBuiltIn(event, context);
            if (!applyApplication(state, event, context)) {
                return false;
            }
            applyServiceSpecific(state, event, context);
            return true;
        } catch {
            // Fail-open: prefer noisy data over no data.
            return true;
        }
    };
}