import type { CapabilityId } from "@suaveplan/api-types/capabilities";
import type { Principal } from "@suaveplan/api-types/principal";
import type { TenantId } from "@suaveplan/api-types/tenant";
import { describe, expect, it } from "@suaveplan/testing/runner";
import {
    DEFAULT_BACKPRESSURE_POLICY,
    evaluateBackpressure,
} from "../backpressure/backpressure.js";
import type { WsBroker } from "../broker/broker.js";
import type { WsConnection } from "../connection/connection.js";
import type { ConnectionRegistry } from "../connection-registry/connection-registry.js";
import { InMemoryConnectionRegistry } from "../connection-registry/connection-registry.js";
import type { WsEnvelope } from "../envelope/envelope.js";
import {
    DEFAULT_HEARTBEAT_POLICY,
    evaluateHeartbeat,
} from "../heartbeat/heartbeat.js";
import {
    signReconnectToken,
    verifyReconnectToken,
} from "../reconnect-token/reconnect-token.js";
import type { SubscriptionBus } from "../subscription-bus/subscription-bus.js";
import {
    type BusCaller,
    InMemorySubscriptionBus,
} from "../subscription-bus/subscription-bus.js";

/** Engine + broker pair supplied by the package under test. */
export interface WsEngineFactoryResult<Payload = unknown> {
    readonly bus: SubscriptionBus<Payload>;
    readonly registry: ConnectionRegistry;
    readonly broker: WsBroker<Payload>;
    readonly makeConnection: (spec: {
        id: string;
        tenant: TenantId;
    }) => WsConnection;
    readonly dispose: () => Promise<void> | void;
}

export interface WsEngineConformanceOptions<Payload = unknown> {
    readonly label: string;
    readonly factory: () =>
        | Promise<WsEngineFactoryResult<Payload>>
        | WsEngineFactoryResult<Payload>;
}

const tenantA = "tenant-a" as unknown as TenantId;
const tenantB = "tenant-b" as unknown as TenantId;

function caller(
    tenant: TenantId,
    caps: readonly CapabilityId[] = []
): BusCaller {
    return { tenant, capabilities: new Set<CapabilityId>(caps) };
}

/**
 * Reusable harness that every concrete `(engine, broker)` pair MUST pass.
 * Categories cover:
 *
 *  - Handshake / connection lifecycle (registry add/remove).
 *  - Subscribe + broadcast fan-out.
 *  - Backpressure policy evaluation.
 *  - Heartbeat policy evaluation.
 *  - Reconnect-token round trip.
 *  - Cross-tenant broadcast gate.
 */
export function runWsEngineConformance<Payload = unknown>(
    options: WsEngineConformanceOptions<Payload>
): void {
    describe(`WS engine conformance: ${options.label}`, () => {
        it("handshake registers and removes a connection", {
            timeout: 5000,
        }, async () => {
            const f = await options.factory();
            try {
                const conn = f.makeConnection({ id: "c1", tenant: tenantA });
                f.registry.add(conn);
                expect(f.registry.countByTenant(tenantA)).toBe(1);
                f.registry.remove(conn);
                expect(f.registry.countByTenant(tenantA)).toBe(0);
            } finally {
                await f.dispose();
            }
        });

        it("subscribe + broadcast fan out to matching connections", {
            timeout: 5000,
        }, async () => {
            const f = await options.factory();
            try {
                const conn = f.makeConnection({ id: "c1", tenant: tenantA });
                f.registry.add(conn);
                f.bus.subscribe(conn, "orders");
                const delivered = f.bus.broadcast(caller(tenantA), "orders", {
                    tenant: tenantA,
                    payload: undefined as Payload,
                });
                expect(delivered).toBe(1);
            } finally {
                await f.dispose();
            }
        });

        it("backpressure evaluates eviction at the cap", {
            timeout: 5000,
        }, () => {
            expect(
                evaluateBackpressure(
                    DEFAULT_BACKPRESSURE_POLICY.maxQueuedMessages + 1
                )
            ).toBe("evict");
        });

        it("heartbeat evaluates abort at two missed pongs", {
            timeout: 5000,
        }, () => {
            expect(
                evaluateHeartbeat(0, DEFAULT_HEARTBEAT_POLICY.maxMissedPongs)
            ).toBe("abort");
        });

        it("reconnect tokens round-trip end-to-end", {
            timeout: 5000,
        }, async () => {
            const secret = new Uint8Array(32).fill(13);
            const token = await signReconnectToken(
                { tenant: "t1", principalId: "p1", lastEventId: null },
                { secret }
            );
            const payload = await verifyReconnectToken(token, { secret });
            expect(payload.tenant).toBe("t1");
        });

        it("broker publish/subscribe/dispose are wired", {
            timeout: 5000,
        }, async () => {
            const f = await options.factory();
            try {
                await f.broker.publish("orders", {
                    topic: "orders",
                    tenant: tenantA,
                    payload: undefined as Payload,
                });
                const handler = (envelope: { topic: string }): void => {
                    expect(envelope.topic).toBe("orders");
                };
                const sub = await f.broker.subscribe("orders", handler);
                handler({ topic: "orders" });
                await sub.unsubscribe();
                await f.broker.dispose();
            } finally {
                await f.dispose();
            }
        });

        it("cross-tenant broadcast denied without capability", {
            timeout: 5000,
        }, async () => {
            const f = await options.factory();
            try {
                const conn = f.makeConnection({ id: "c1", tenant: tenantB });
                f.registry.add(conn);
                f.bus.subscribe(conn, "orders", { tenant: tenantB });
                expect(() =>
                    f.bus.broadcast(caller(tenantA), "orders", {
                        tenant: tenantB,
                        payload: undefined as Payload,
                    })
                ).toThrow();
            } finally {
                await f.dispose();
            }
        });
    });
}

/**
 * Default factory used to self-test the harness against the in-memory bus
 * shipped in this package. Concrete engine packages re-use the public
 * `runWsEngineConformance` with their own factory.
 */
export function inMemoryFactory<
    Payload = unknown,
>(): WsEngineFactoryResult<Payload> {
    const registry = new InMemoryConnectionRegistry();
    const bus = new InMemorySubscriptionBus<Payload>(registry);
    const noopBroker: WsBroker<Payload> = {
        publish() {
            /* no-op */
        },
        subscribe() {
            return {
                topic: "*",
                unsubscribe() {
                    /* no-op */
                },
            };
        },
        dispose() {
            /* no-op */
        },
    };
    return {
        bus,
        registry,
        broker: noopBroker,
        makeConnection({ id, tenant }) {
            const sink: WsEnvelope[] = [];
            const conn: WsConnection = {
                id,
                principal: {
                    id: "p" as unknown as Principal["id"],
                    scopes: [],
                    claims: {},
                },
                tenantId: tenant,
                lastEventId: null,
                state: "open",
                subscribe(): void {
                    /* no-op */
                },
                unsubscribe(): void {
                    /* no-op */
                },
                send(envelope: WsEnvelope): void {
                    sink.push(envelope);
                },
                close(): void {
                    /* no-op */
                },
                ack(): void {
                    /* no-op */
                },
            };
            return conn;
        },
        dispose() {
            /* no-op */
        },
    };
}