import type { Callbacks } from '@langchain/core/callbacks/manager';
import { getLangchainCallbacks } from 'langsmith/langchain';
import { v4 as uuid } from 'uuid';

import type { Evaluator, EvaluationContext, Feedback, LlmCallLimiter } from './harness-types';
import type { SimpleWorkflow } from '../../src/types/workflow';
import type { BuilderFeatureFlags, ChatPayload } from '../../src/workflow-builder-agent';
import { DEFAULTS } from '../support/constants';

/**
 * Get LangChain callbacks that bridge the current traceable context.
 * Returns undefined if not in a traceable context.
 */
export async function getTracingCallbacks(): Promise<Callbacks | undefined> {
	try {
		return await getLangchainCallbacks();
	} catch {
		return undefined;
	}
}

export async function consumeGenerator<T>(gen: AsyncGenerator<T>) {
	for await (const _ of gen) {
		/* consume all */
	}
}

export async function runWithOptionalLimiter<T>(
	fn: () => Promise<T>,
	limiter?: LlmCallLimiter,
): Promise<T> {
	return limiter ? await limiter(fn) : await fn();
}

export async function withTimeout<T>(args: {
	promise: Promise<T>;
	timeoutMs?: number;
	label: string;
}): Promise<T> {
	// NOTE:
	// - This is a best-effort timeout. It does NOT cancel/abort the underlying work.
	// - If the underlying work supports cancellation (e.g. AbortSignal), plumb that through instead.
	// - When combined with `p-limit`, prefer applying the timeout *inside* the limited function so the
	//   limiter slot is released when the timeout triggers.
	const { promise, timeoutMs, label } = args;
	if (typeof timeoutMs !== 'number') return await promise;
	if (!Number.isFinite(timeoutMs) || timeoutMs <= 0) {
		throw new Error(`Invalid timeoutMs (${String(timeoutMs)}) for ${label}`);
	}

	let timer: NodeJS.Timeout | undefined;
	try {
		const timeout = new Promise<never>((_resolve, reject) => {
			timer = setTimeout(
				() => reject(new Error(`Timed out after ${timeoutMs}ms in ${label}`)),
				timeoutMs,
			);
		});
		return await Promise.race([promise, timeout]);
	} finally {
		if (timer) clearTimeout(timer);
	}
}

export interface GetChatPayloadOptions {
	evalType: string;
	message: string;
	workflowId: string;
	featureFlags?: BuilderFeatureFlags;
}

export function getChatPayload(options: GetChatPayloadOptions): ChatPayload {
	const { evalType, message, workflowId, featureFlags } = options;

	return {
		id: `${evalType}-${uuid()}`,
		featureFlags: featureFlags ?? DEFAULTS.FEATURE_FLAGS,
		message,
		workflowContext: {
			currentWorkflow: { id: workflowId, nodes: [], connections: {} },
		},
	};
}

/**
 * Coordination log entry for subgraph timing extraction.
 * Matches the CoordinationLogEntry type from src/types/coordination.ts
 */
interface CoordinationLogEntry {
	phase: 'discovery' | 'builder' | 'assistant' | 'state_management' | 'responder' | 'planner';
	status: 'completed' | 'in_progress' | 'error';
	timestamp: number;
}

/**
 * Subgraph metrics extracted from coordination log.
 */
export interface ExtractedSubgraphMetrics {
	discoveryDurationMs?: number;
	builderDurationMs?: number;
	responderDurationMs?: number;
	nodeCount?: number;
}

/**
 * Calculate duration for a specific phase from coordination log entries.
 * Looks for the first 'in_progress' and terminal ('completed' or 'error') status for the phase.
 */
function calculatePhaseDuration(
	coordinationLog: CoordinationLogEntry[],
	phase: 'discovery' | 'builder' | 'responder',
): number | undefined {
	const phaseEntries = coordinationLog.filter((entry) => entry.phase === phase);
	if (phaseEntries.length === 0) return undefined;

	const inProgress = phaseEntries.find((e) => e.status === 'in_progress');
	// Accept either 'completed' or 'error' as the terminal status
	const terminal = phaseEntries.find((e) => e.status === 'completed' || e.status === 'error');

	if (inProgress && terminal) {
		return terminal.timestamp - inProgress.timestamp;
	}

	// If no in_progress entry, try to calculate from first to last entry
	if (phaseEntries.length >= 2) {
		const sorted = [...phaseEntries].sort((a, b) => a.timestamp - b.timestamp);
		return sorted[sorted.length - 1].timestamp - sorted[0].timestamp;
	}

	return undefined;
}

/**
 * Extract subgraph metrics from coordination log and workflow.
 */
export function extractSubgraphMetrics(
	coordinationLog: CoordinationLogEntry[] | undefined,
	nodeCount: number | undefined,
): ExtractedSubgraphMetrics {
	const metrics: ExtractedSubgraphMetrics = {};

	// Include node count
	if (nodeCount !== undefined) {
		metrics.nodeCount = nodeCount;
	}

	// Extract timing from coordination log
	if (coordinationLog && coordinationLog.length > 0) {
		const discoveryDuration = calculatePhaseDuration(coordinationLog, 'discovery');
		const builderDuration = calculatePhaseDuration(coordinationLog, 'builder');
		const responderDuration = calculatePhaseDuration(coordinationLog, 'responder');

		if (discoveryDuration !== undefined) {
			metrics.discoveryDurationMs = discoveryDuration;
		}
		if (builderDuration !== undefined) {
			metrics.builderDurationMs = builderDuration;
		}
		if (responderDuration !== undefined) {
			metrics.responderDurationMs = responderDuration;
		}
	}

	return metrics;
}

/**
 * Run all evaluators on a workflow + context pair, with per-evaluator timeouts.
 * Returns flattened feedback; errors are captured as feedback items.
 */
export async function runEvaluatorsOnExample(
	evaluators: Array<Evaluator<EvaluationContext>>,
	workflow: SimpleWorkflow,
	context: EvaluationContext,
	timeoutMs?: number,
): Promise<Feedback[]> {
	return (
		await Promise.all(
			evaluators.map(async (evaluator): Promise<Feedback[]> => {
				try {
					return await withTimeout({
						promise: evaluator.evaluate(workflow, context),
						timeoutMs,
						label: `evaluator:${evaluator.name}`,
					});
				} catch (error) {
					const msg = error instanceof Error ? error.message : String(error);
					return [
						{
							evaluator: evaluator.name,
							metric: 'error',
							score: 0,
							kind: 'score' as const,
							comment: msg,
						},
					];
				}
			}),
		)
	).flat();
}