import type { ExtensionContext } from "@earendil-works/pi-coding-agent";
import type { QuotaSnapshot } from "./types.ts";
import { BUILTIN_MODEL_PROVIDERS, isBuiltinQuotaProvider, QUOTA_PROVIDERS, quotaProviderTitle } from "./types.ts";

export const QUOTA_ADAPTERS_KEY = Symbol.for("@zhcsyncer/pi-meter/quota-adapters");

export interface QuotaModelRef {
	provider?: string;
	id?: string;
}

export interface QuotaAdapter {
	id: string;
	title: string;
	matchProvider(model: QuotaModelRef): boolean;
	fetch(ctx: Pick<ExtensionContext, "modelRegistry">, fetchedAt?: number): Promise<QuotaSnapshot>;
}

export interface QuotaAdapterHost {
	register(adapter: QuotaAdapter): void;
	list(): QuotaAdapter[];
	mailbox?: unknown[];
}

const adapters = new Map<string, QuotaAdapter>();
const registerWarnings: string[] = [];

function warnRegister(message: string): void {
	console.warn(message);
	registerWarnings.push(message);
}

export function takeQuotaAdapterWarnings(): string[] {
	return registerWarnings.splice(0);
}

function isAdapter(value: unknown): value is QuotaAdapter {
	if (!value || typeof value !== "object") return false;
	const adapter = value as QuotaAdapter;
	return typeof adapter.id === "string"
		&& adapter.id.length > 0
		&& typeof adapter.title === "string"
		&& typeof adapter.matchProvider === "function"
		&& typeof adapter.fetch === "function";
}

function readHost(): QuotaAdapterHost | undefined {
	return (globalThis as unknown as Record<symbol, QuotaAdapterHost | undefined>)[QUOTA_ADAPTERS_KEY];
}

function writeHost(host: QuotaAdapterHost): void {
	(globalThis as unknown as Record<symbol, QuotaAdapterHost>)[QUOTA_ADAPTERS_KEY] = host;
}

function claimedBuiltinModels(adapter: QuotaAdapter): string[] {
	const claimed: string[] = [];
	for (const provider of BUILTIN_MODEL_PROVIDERS) {
		try {
			if (adapter.matchProvider({ provider })) claimed.push(provider);
		} catch {
			// Probe only; a throwing matcher is ignored for built-ins too.
		}
	}
	return claimed;
}

export function registerQuotaAdapter(adapter: QuotaAdapter): void {
	if (!isAdapter(adapter)) return;
	if (isBuiltinQuotaProvider(adapter.id)) {
		warnRegister(`pi-meter: refused quota adapter "${adapter.id}" because it collides with a built-in source`);
		return;
	}
	const claimed = claimedBuiltinModels(adapter);
	if (claimed.length > 0) {
		warnRegister(`pi-meter: quota adapter "${adapter.id}" matchProvider() claims built-in model provider(s) ${claimed.join(", ")}; those matches are ignored`);
	}
	adapters.set(adapter.id, adapter);
}

export function listQuotaAdapters(): QuotaAdapter[] {
	return [...adapters.values()];
}

export function getQuotaAdapter(id: string): QuotaAdapter | undefined {
	return adapters.get(id);
}

export function quotaSourceTitle(id: string): string {
	return getQuotaAdapter(id)?.title ?? quotaProviderTitle(id);
}

export function listedQuotaSourceIds(): string[] {
	const ids: string[] = [...QUOTA_PROVIDERS];
	const seen = new Set<string>(QUOTA_PROVIDERS);
	for (const adapter of adapters.values()) {
		if (seen.has(adapter.id)) continue;
		seen.add(adapter.id);
		ids.push(adapter.id);
	}
	return ids;
}

export function installQuotaAdapterHost(): void {
	const current = readHost();
	const pending = Array.isArray(current?.mailbox) ? [...current.mailbox] : [];
	writeHost({
		register: registerQuotaAdapter,
		list: listQuotaAdapters,
		mailbox: [],
	});
	for (const item of pending) {
		if (isAdapter(item)) registerQuotaAdapter(item);
	}
}

export function resetQuotaAdapters(): void {
	adapters.clear();
	registerWarnings.length = 0;
	installQuotaAdapterHost();
}

installQuotaAdapterHost();