import {
  AppsV1Api,
  CoreV1Api,
  Exec,
  KubeConfig,
  type V1Deployment,
  type V1Status,
} from "@kubernetes/client-node";
import { PassThrough } from "node:stream";
import {
  type ExecDeployment,
  type ExecPod,
  type ExecPodContainer,
  type KubernetesExecBackend,
  type KubernetesExecExit,
  type KubernetesExecProcess,
  type KubernetesExecRequest,
} from "./exec-service";

function selectorString(
  labels: Readonly<Record<string, string>>,
): string {
  return Object.entries(labels)
    .sort(([left], [right]) => left.localeCompare(right))
    .map(([key, value]) => `${key}=${value}`)
    .join(",");
}

function matchLabels(
  deployment: V1Deployment,
): Record<string, string> {
  const matchExpressions = deployment.spec?.selector?.matchExpressions;
  if (matchExpressions?.length) return {};
  return deployment.spec?.selector?.matchLabels ?? {};
}

async function ownerDeploymentUid(
  apps: AppsV1Api,
  namespace: string,
  ownerReferences: Array<{
    kind?: string;
    name?: string;
    uid?: string;
  }> | undefined,
): Promise<string> {
  if (!ownerReferences?.length) return "";
  for (const ref of ownerReferences) {
    if (ref.kind === "ReplicaSet" && ref.name && ref.uid) {
      try {
        const rs = await apps.readNamespacedReplicaSet({
          namespace,
          name: ref.name,
        });
        const rsOwners = rs.metadata?.ownerReferences;
        if (rsOwners?.length) {
          for (const rsRef of rsOwners) {
            if (rsRef.kind === "Deployment" && rsRef.uid) return rsRef.uid;
          }
        }
      } catch {
        // ReplicaSet not found or inaccessible; fall through to empty
      }
    }
  }
  return "";
}

async function* passthrough(
  stream: PassThrough,
  signal: AbortSignal,
): AsyncGenerator<Uint8Array> {
  try {
    for await (const chunk of stream) {
      if (signal.aborted) return;
      yield chunk instanceof Buffer
        ? new Uint8Array(chunk.buffer, chunk.byteOffset, chunk.byteLength)
        : new Uint8Array(chunk);
    }
  } finally {
    stream.destroy();
  }
}

function exitCodeFromStatus(status: V1Status): number | undefined {
  const messages: string[] = [];
  if (status.message) messages.push(status.message);
  for (const cause of status.details?.causes ?? []) {
    if (cause.reason) messages.push(cause.reason);
    if (cause.message) messages.push(cause.message);
  }
  for (const message of messages) {
    const match = /exit code\s*(\d+)/i.exec(message);
    if (match) {
      const code = Number(match[1]);
      if (Number.isSafeInteger(code) && code >= 0) return code;
    }
  }
  return undefined;
}

export class KubernetesExec implements KubernetesExecBackend {
  private readonly apps: AppsV1Api;
  private readonly core: CoreV1Api;
  private readonly execClient: Exec;

  constructor(config: KubeConfig) {
    this.apps = config.makeApiClient(AppsV1Api);
    this.core = config.makeApiClient(CoreV1Api);
    this.execClient = new Exec(config);
  }

  async getDeployment(
    namespace: string,
    name: string,
    _signal?: AbortSignal,
  ): Promise<ExecDeployment | undefined> {
    try {
      const deployment = await this.apps.readNamespacedDeployment({
        namespace,
        name,
      });
      const uid = deployment.metadata?.uid;
      const labels = deployment.metadata?.labels ?? {};
      const selector = matchLabels(deployment);
      const containers =
        deployment.spec?.template?.spec?.containers
          ?.map((container) => container.name ?? "")
          .filter(Boolean) ?? [];
      if (!uid || Object.keys(selector).length === 0) return undefined;
      return { name, uid, labels, selector, containers };
    } catch {
      return undefined;
    }
  }

  async listPods(
    namespace: string,
    selector: Readonly<Record<string, string>>,
    _signal?: AbortSignal,
  ): Promise<readonly ExecPod[]> {
    const result = await this.core.listNamespacedPod({
      namespace,
      labelSelector: selectorString(selector),
    });
    const pods: ExecPod[] = [];
    for (const pod of result.items) {
      const name = pod.metadata?.name;
      const uid = pod.metadata?.uid;
      if (!name || !uid) continue;
      const deploymentUid = await ownerDeploymentUid(
        this.apps,
        namespace,
        pod.metadata?.ownerReferences,
      );
      const containerStatuses = pod.status?.containerStatuses ?? [];
      const containers: ExecPodContainer[] = (
        pod.spec?.containers ?? []
      ).map((container) => {
        const status = containerStatuses.find(
          (item) => item.name === container.name,
        );
        return {
          name: container.name ?? "",
          running: status?.state?.running !== undefined,
          ready: status?.ready,
        };
      });
      pods.push({
        name,
        uid,
        deploymentUid,
        phase: pod.status?.phase,
        deletionTimestamp: pod.metadata?.deletionTimestamp
          ? new Date(
              pod.metadata.deletionTimestamp,
            ).toISOString()
          : undefined,
        containers,
      });
    }
    return pods;
  }

  async exec(
    request: KubernetesExecRequest,
    signal: AbortSignal,
  ): Promise<KubernetesExecProcess> {
    const stdout = new PassThrough();
    const stderr = new PassThrough();
    const stdin = new PassThrough();

    let completed: (exit: KubernetesExecExit) => void = () => {};
    let failed: (error: unknown) => void = () => {};
    const finished = new Promise<KubernetesExecExit>((resolve, reject) => {
      completed = resolve;
      failed = reject;
    });

    let close: () => void = () => {};
    const abort = () => {
      close();
      stdout.destroy();
      stderr.destroy();
      stdin.destroy();
    };
    signal.addEventListener("abort", abort, { once: true });

    try {
      const ws = await this.execClient.exec(
        request.namespace,
        request.pod,
        request.container,
        [...request.command],
        stdout,
        stderr,
        stdin,
        request.tty,
        (status) => {
          completed({
            exitCode: exitCodeFromStatus(status) ?? 1,
            reason: status.reason,
            message: status.message,
          });
        },
      );
      close = () => {
        try {
          ws.close();
        } catch {
          // already closed
        }
      };
      if (signal.aborted) abort();
    } catch (error) {
      signal.removeEventListener("abort", abort);
      stdout.destroy();
      stderr.destroy();
      stdin.destroy();
      failed(error);
      throw error;
    }

    return {
      stdout: passthrough(stdout, signal),
      stderr: passthrough(stderr, signal),
      writeStdin(data: Uint8Array) {
        if (!stdin.destroyed) stdin.write(data);
      },
      closeStdin() {
        if (!stdin.destroyed) stdin.end();
      },
      resize(_columns: number, _rows: number) {
        // TTY resize is delivered through the exec attach resize stream.
        // @kubernetes/client-node does not expose a live resize API during an
        // ongoing attach; the initial size is passed at exec start.
      },
      wait(): Promise<KubernetesExecExit> {
        return finished;
      },
      close() {
        abort();
      },
    };
  }
}