import { mkdir, rm } from "node:fs/promises";
import path from "node:path";

import { afterAll, beforeAll, describe, expect, it } from "vitest";

import { readBoundedBytes } from "../../src/adapters/http/bounded-body-reader.ts";
import {
  createContractHttpExecutor,
  type HttpExecutionObservation,
} from "../../src/adapters/http/http-execution-v3.ts";
import {
  type InstalledHttpContract,
} from "../../src/contracts/external-contract-runtime.ts";
import type { CacheScopeSnapshot } from "../../src/contracts/server-state-scope.ts";
import { REFERENCE_FEATURE_TEMPLATE_CONTRIBUTION } from "../../src/features/reference-feature/contracts/reference-feature-contract-contribution.ts";
import {
  computeHttpScenarioCatalogDigest,
  httpScenarioReceiptSchema,
  type AttemptStatus,
  type BodyDisposition,
  type HttpScenarioAssertionGroups,
  type RetryReason,
} from "../../scripts/lib/http-scenario-evidence.ts";
import { writeValidatedJsonArtifact } from "../../scripts/lib/validated-json-artifact.ts";
import { createReferenceScenarioHandlers } from "../mocks/handlers/reference-resources.ts";
import { createStrictMockServer } from "../mocks/server.ts";
import {
  HTTP_SCENARIO_EXECUTION_IDS,
  HTTP_SCENARIO_EXPECTATIONS,
  HTTP_SCENARIO_RECEIPT_SCHEMA_VERSION,
  OPERATION_SCENARIO_CATALOG,
  type HttpScenarioExpectation,
  type HttpScenarioOperationId,
} from "../mocks/scenarios/catalog.ts";

/** The reference gateway owns these low-cardinality route identities. */
function routeIdFor(operationId: HttpScenarioOperationId): string {
  return operationId === "GET_REFERENCE_RESOURCE"
    ? "REFERENCE_RESOURCE_DETAIL"
    : "REFERENCE_RESOURCE_LIST";
}

const RECEIPT_PATH = path.resolve(
  "artifacts/tests/http-scenario-executions.json",
);
const mockApi = createStrictMockServer();

beforeAll(mockApi.listen);
afterAll(mockApi.close);

type AttemptTrace = {
  status: AttemptStatus;
  media: string | null;
  pulledBytes: number;
  appliedCeiling: number | null;
  completed: boolean;
  cancelled: boolean;
};

function operationFor(operationId: HttpScenarioOperationId) {
  const operation = REFERENCE_FEATURE_TEMPLATE_CONTRIBUTION.http.find(
    (candidate) => candidate.contract.operationId === operationId,
  );
  if (!operation) throw new Error(`Missing operation fixture: ${operationId}`);
  return operation as InstalledHttpContract<unknown, unknown, unknown>;
}

function inputFor(operationId: HttpScenarioOperationId): unknown {
  if (operationId === "LIST_REFERENCE_RESOURCES") return { limit: 20 };
  if (operationId === "GET_REFERENCE_RESOURCE") {
    return { resourceId: "reference-1" };
  }
  return { name: "Created" };
}

function normalizeMedia(response: Response): string | null {
  const value = response.headers.get("content-type");
  return value?.split(";", 1)[0]?.trim().toLowerCase() || null;
}

function tracingFetcher(attempts: AttemptTrace[]): typeof fetch {
  return async (input, init) => {
    const trace: AttemptTrace = {
      status: "PENDING_ABORT",
      media: null,
      pulledBytes: 0,
      appliedCeiling: null,
      completed: false,
      cancelled: false,
    };
    attempts.push(trace);
    let response: Response;
    try {
      response = await fetch(input, init);
    } catch (error) {
      trace.status = init?.signal?.aborted
        ? "PENDING_ABORT"
        : "NETWORK_REJECTION";
      throw error;
    }
    trace.status = response.status;
    trace.media = normalizeMedia(response);
    if (!response.body) return response;

    const reader = response.body.getReader();
    const proxy = new ReadableStream<Uint8Array>(
      {
        async pull(controller) {
          try {
            const chunk = await reader.read();
            if (chunk.done) {
              trace.completed = true;
              controller.close();
              return;
            }
            trace.pulledBytes += chunk.value.byteLength;
            controller.enqueue(chunk.value);
          } catch (error) {
            controller.error(error);
          }
        },
        cancel(reason) {
          trace.cancelled = true;
          // MSW-transferred oversized bodies leave the original cancel promise
          // permanently pending. Record and request cancellation without making
          // the proxy response less responsive than the real executor contract.
          void reader.cancel(reason).catch(() => {});
        },
      },
      { highWaterMark: 0 },
    );
    return new Response(proxy, {
      status: response.status,
      statusText: response.statusText,
      headers: response.headers,
    });
  };
}

function outcomeDetail(outcome: Readonly<Record<string, unknown>>): string | null {
  if (outcome.kind === "CONTRACT_VIOLATION") {
    return String((outcome.violation as Readonly<{ kind: string }>).kind);
  }
  if (outcome.kind === "TRANSPORT_FAILURE") {
    return String((outcome.failure as Readonly<{ kind: string }>).kind);
  }
  if (outcome.kind === "PROBLEM") {
    return String((outcome.metadata as Readonly<{ status: number }>).status);
  }
  return null;
}

function retryReason(status: AttemptStatus): RetryReason {
  if (status === "NETWORK_REJECTION") return "NETWORK_FAILURE";
  if (status === 429) return "HTTP_429";
  if (status === 503) return "HTTP_503";
  throw new Error(`Sleep followed a non-retryable attempt: ${String(status)}`);
}

function bodyDisposition(
  trace: AttemptTrace,
  outcome: Readonly<Record<string, unknown>>,
): BodyDisposition {
  if (trace.status === "NETWORK_REJECTION" || trace.status === "PENDING_ABORT") {
    return "NO_RESPONSE";
  }
  if (
    outcome.kind === "CONTRACT_VIOLATION" &&
    outcomeDetail(outcome) === "RESPONSE_TOO_LARGE" &&
    trace.cancelled
  ) {
    return "REJECTED_LIMIT";
  }
  if (trace.completed) return "FULLY_READ_WITHIN_BOUND";
  if (trace.cancelled) return "CANCELLED_WITHOUT_READ";
  throw new Error(`Response body was neither consumed nor cancelled: ${trace.status}`);
}

async function waitForHandler(
  ready: Promise<void>,
  executionId: string,
): Promise<void> {
  let watchdog: ReturnType<typeof setTimeout> | undefined;
  try {
    await Promise.race([
      ready,
      new Promise<never>((_resolve, reject) => {
        watchdog = setTimeout(
          () => reject(new Error(`Handler readiness timed out: ${executionId}`)),
          2_000,
        );
      }),
    ]);
  } finally {
    if (watchdog !== undefined) clearTimeout(watchdog);
  }
}

async function executeScenario(
  entry: HttpScenarioExpectation,
): Promise<HttpScenarioAssertionGroups> {
  const physicalAttempts: AttemptTrace[] = [];
  const sleeps: RetryReason[] = [];
  const observations: HttpExecutionObservation[] = [];
  const caller = new AbortController();
  const scopeLifetime = new AbortController();
  let scopeCurrent = true;
  let handlerReady!: () => void;
  const ready = new Promise<void>((resolve) => {
    handlerReady = resolve;
  });
  const scope: CacheScopeSnapshot = Object.freeze({
    generation: 1,
    fingerprint: "scenario-scope-1",
    identities: Object.freeze({}) as CacheScopeSnapshot["identities"],
    signal: scopeLifetime.signal,
    isCurrent: () => scopeCurrent,
  });
  const baseOperation = operationFor(entry.operationId);
  const operation =
    entry.testDeadlineOverrideMs === null
      ? baseOperation
      : Object.freeze({
          ...baseOperation,
          frontend: Object.freeze({
            ...baseOperation.frontend,
            totalDeadlineMs: entry.testDeadlineOverrideMs,
          }),
        });
  const fetcher = tracingFetcher(physicalAttempts);
  const executor = createContractHttpExecutor({
    baseUrl: "https://api.test",
    maxRetryAttempts: 2,
    attachCredentials: () => ({
      kind: "READY",
      headers: {},
      credentials: "omit",
    }),
    fetcher,
    random: () => 0,
    readBoundedResponseBytes: async (response, maximumBytes) => {
      const trace = physicalAttempts.at(-1);
      if (!trace) throw new Error("Body reader ran before a physical attempt");
      if (trace.appliedCeiling !== null) {
        throw new Error("Body reader ran more than once for one attempt");
      }
      trace.appliedCeiling = maximumBytes;
      return readBoundedBytes(response, maximumBytes);
    },
    sleep: async () => {
      const prior = physicalAttempts.at(-1);
      if (!prior) throw new Error("Retry sleep occurred before an attempt");
      sleeps.push(retryReason(prior.status));
    },
    observe: (observation) => observations.push(observation),
  });

  mockApi.server.use(
    ...createReferenceScenarioHandlers({
      scenarios: { [entry.operationId]: entry.scenarioId },
      onAttempt(attempt) {
        if (
          attempt.operationId === entry.operationId &&
          attempt.scenarioId === entry.scenarioId
        ) {
          handlerReady();
        }
      },
    }),
  );

  try {
    const execution = executor.execute(operation, inputFor(entry.operationId), {
      routeId: routeIdFor(entry.operationId),
      scope,
      signal: caller.signal,
      ...(entry.operationId === "CREATE_REFERENCE_RESOURCE"
        ? {
            intent: Object.freeze({
              intentId: `intent-${entry.scenarioId}`,
              operationId: entry.operationId,
              canonicalInputIdentity: "scenario-input",
              idempotencyKey: `scenario-${entry.scenarioId}`,
              createdAtMonotonicMs: 1,
            }),
          }
        : {}),
    });

    if (entry.scenarioId === "timeout" || entry.scenarioId === "aborted") {
      await waitForHandler(ready, entry.executionId);
      if (entry.scenarioId === "aborted") {
        if (entry.operationId === "LIST_REFERENCE_RESOURCES") {
          caller.abort();
        } else {
          scopeCurrent = false;
          scopeLifetime.abort();
        }
      }
    }
    const outcome = (await execution) as unknown as Readonly<Record<string, unknown>>;
    expect(observations, `${entry.executionId} observer count`).toHaveLength(1);
    const observation = observations[0]!;
    const observedSignal = scopeLifetime.signal.aborted ? "ABORTED" : "ACTIVE";
    const cancellationOwner =
      observation.terminalReason === "TIMEOUT"
        ? "DEADLINE"
        : caller.signal.aborted
          ? "CALLER"
          : scopeLifetime.signal.aborted
            ? "SCOPE_FENCE"
            : "NONE";
    const observed: HttpScenarioAssertionGroups = Object.freeze({
      status: Object.freeze({
        attempts: Object.freeze(physicalAttempts.map((attempt) => attempt.status)),
        final: physicalAttempts.at(-1)!.status,
      }),
      outcome: Object.freeze({
        kind: String(outcome.kind),
        detail: outcomeDetail(outcome),
      }),
      effect: Object.freeze({
        outcome: String(outcome.effect),
        observer: observation.terminalReason,
      }),
      retry: Object.freeze({ count: sleeps.length, reasons: Object.freeze(sleeps) }),
      fetch: Object.freeze({
        count: physicalAttempts.length,
        observerAttempts: observation.attemptCount,
        agrees: physicalAttempts.length === observation.attemptCount,
      }),
      media: Object.freeze({
        attempts: Object.freeze(physicalAttempts.map((attempt) => attempt.media)),
        final: physicalAttempts.at(-1)?.media ?? null,
      }),
      body: Object.freeze({
        attempts: Object.freeze(
          physicalAttempts.map((attempt) =>
            Object.freeze({
              disposition: bodyDisposition(attempt, outcome),
              pulledBytes: attempt.pulledBytes,
              ceiling: attempt.appliedCeiling ?? 0,
            }),
          ),
        ),
      }),
      scope: Object.freeze({
        start: "CURRENT",
        end: scopeCurrent ? "CURRENT" : "STALE",
        signal: observedSignal,
        cancellationOwner,
      }),
    });
    return observed;
  } finally {
    caller.abort();
    scopeLifetime.abort();
    mockApi.reset();
  }
}

describe("HTTP scenario catalog execution evidence", () => {
  it("declares exactly the 54 behaviorally distinct operation scenarios", () => {
    const executionIds = Object.entries(OPERATION_SCENARIO_CATALOG).flatMap(
      ([operationId, scenarioIds]) =>
        scenarioIds.map((scenarioId) => `${operationId}::${scenarioId}`),
    );

    expect(OPERATION_SCENARIO_CATALOG.LIST_REFERENCE_RESOURCES).toHaveLength(19);
    expect(OPERATION_SCENARIO_CATALOG.GET_REFERENCE_RESOURCE).toHaveLength(18);
    expect(OPERATION_SCENARIO_CATALOG.CREATE_REFERENCE_RESOURCE).toHaveLength(17);
    expect(executionIds).toHaveLength(54);
    expect(new Set(executionIds)).toHaveLength(54);
    expect(executionIds).toEqual(HTTP_SCENARIO_EXECUTION_IDS);
  });

  it("executes every declared scenario and publishes one complete receipt", async () => {
    await rm(RECEIPT_PATH, { force: true });
    const rows: Array<Readonly<{
      executionId: string;
      expected: HttpScenarioAssertionGroups;
      observed: HttpScenarioAssertionGroups;
      testDeadlineOverrideMs: number | null;
    }>> = [];

    for (const entry of HTTP_SCENARIO_EXPECTATIONS) {
      const observed = await executeScenario(entry);
      expect(observed, entry.executionId).toEqual(entry.expected);
      rows.push(
        Object.freeze({
          executionId: entry.executionId,
          expected: entry.expected,
          observed,
          testDeadlineOverrideMs: entry.testDeadlineOverrideMs,
        }),
      );
    }

    const sortedRows = [...rows].sort((left, right) =>
      left.executionId.localeCompare(right.executionId),
    );
    await mkdir(path.dirname(RECEIPT_PATH), { recursive: true });
    await writeValidatedJsonArtifact({
      path: RECEIPT_PATH,
      schema: httpScenarioReceiptSchema,
      value: {
        schemaVersion: HTTP_SCENARIO_RECEIPT_SCHEMA_VERSION,
        catalogDigest: computeHttpScenarioCatalogDigest(
          HTTP_SCENARIO_RECEIPT_SCHEMA_VERSION,
          HTTP_SCENARIO_EXPECTATIONS,
        ),
        catalogTotal: 54,
        executedIds: sortedRows.map((row) => row.executionId),
        rows: sortedRows,
      },
    });
  }, 30_000);
});