/// <reference lib="webworker" />

import type {
	CounterfactualAnalysis,
	LeavePlacement,
	PlanOutcome,
	PlanningExplanation,
	PlanningOutcome,
	PlanningReason,
	PlanningSnapshot,
	PlanningStateSnapshot,
} from './leave-planner.service';
import {
	analyzeCounterfactualInternal,
	calculatePlanningAsyncInternal,
	explainIncompleteCheckpoint,
	type PlanningArtifacts,
} from './leave-planner.core';

type WorkerPlanningRequest = {
	calculationDate?: string;
	declaredDays?: unknown;
	horizon?: { start?: unknown; end?: unknown };
	balances?: unknown;
	rules?: unknown;
	identities?: unknown;
	labels?: unknown;
	deadlineMs?: unknown;
	progress?: unknown;
};

type WorkerRequest =
	| {
			type: 'plan';
			request: WorkerPlanningRequest;
	  }
	| { type: 'cancel' }
	| {
			type: 'counterfactual';
			request: PlanningSnapshot;
			plan: PlanOutcome;
			placement: LeavePlacement;
			state?: PlanningStateSnapshot;
	  }
	| {
			type: 'explain-checkpoint';
			request: PlanningSnapshot;
			plan: PlanOutcome;
			state: PlanningStateSnapshot;
			interruption: PlanningReason;
	  };

type WorkerResponse =
	| { type: 'heartbeat' }
	| { type: 'progress'; stage: string }
	| { type: 'checkpoint'; plan: PlanOutcome; state?: PlanningStateSnapshot }
	| { type: 'result'; outcome: PlanningOutcome }
	| { type: 'artifacts'; artifacts: PlanningArtifacts }
	| {
			type: 'explanation';
			explanation?: PlanningExplanation;
			explanationError?: PlanningReason;
			finalState?: PlanningStateSnapshot;
	  }
	| { type: 'counterfactual-result'; analysis: CounterfactualAnalysis }
	| { type: 'error'; code?: string; message: string };

const worker = self as DedicatedWorkerGlobalScope;
let activeCalculation: { cancelled: boolean } | undefined;

worker.onmessage = async (event: MessageEvent<WorkerRequest>) => {
	try {
		if (event.data?.type === 'cancel') {
			if (activeCalculation) activeCalculation.cancelled = true;
			return;
		}
		if (event.data?.type === 'plan') {
			const calculation = { cancelled: false };
			activeCalculation = calculation;
			let artifacts: PlanningArtifacts = {};
			let outcomePosted = false;
			let outcome: PlanningOutcome;
			// The cooperative driver yields during preparation and search, even within one phase.
			const heartbeat = () =>
				worker.postMessage({ type: 'heartbeat' } satisfies WorkerResponse);
			const heartbeatTimer = setInterval(heartbeat, 1000);
			try {
				heartbeat();
				outcome = await calculatePlanningAsyncInternal(
					{
						...event.data.request,
						progress: (stage: string) =>
							worker.postMessage({
								type: 'progress',
								stage,
							} satisfies WorkerResponse),
					},
					(plan, state) =>
						worker.postMessage({
							type: 'checkpoint',
							plan,
							state,
						} satisfies WorkerResponse),
					(value) => (artifacts = value),
					(value) => {
						outcomePosted = true;
						worker.postMessage({
							type: 'result',
							outcome: value,
						} satisfies WorkerResponse);
					},
					(explanation, explanationError, finalState) =>
						worker.postMessage({
							type: 'explanation',
							explanation,
							explanationError,
							finalState,
						} satisfies WorkerResponse),
					() => calculation.cancelled,
				);
			} catch (error) {
				worker.postMessage({
					type: 'error',
					code: 'planner-error',
					message: error instanceof Error ? error.message : String(error),
				} satisfies WorkerResponse);
				return;
			} finally {
				clearInterval(heartbeatTimer);
				if (activeCalculation === calculation) activeCalculation = undefined;
			}
			if (!outcomePosted)
				worker.postMessage({ type: 'result', outcome } satisfies WorkerResponse);
			worker.postMessage({ type: 'artifacts', artifacts } satisfies WorkerResponse);
			return;
		}
		if (event.data?.type === 'explain-checkpoint') {
			const result = explainIncompleteCheckpoint(
				event.data.request,
				event.data.plan,
				event.data.state,
				event.data.interruption,
			);
			worker.postMessage({ type: 'explanation', ...result } satisfies WorkerResponse);
			return;
		}
		if (event.data?.type !== 'counterfactual') return;
		try {
			const analysis = analyzeCounterfactualInternal(
				event.data.request,
				event.data.plan,
				event.data.placement,
				event.data.state,
			);
			worker.postMessage({
				type: 'counterfactual-result',
				analysis,
			} satisfies WorkerResponse);
		} catch (error) {
			worker.postMessage({
				type: 'error',
				code: 'counterfactual-error',
				message: error instanceof Error ? error.message : String(error),
			} satisfies WorkerResponse);
		}
	} catch (error) {
		worker.postMessage({
			type: 'error',
			code: 'worker-error',
			message: error instanceof Error ? error.message : String(error),
		} satisfies WorkerResponse);
	}
};