/**
 * Copyright (c) OpenLens Authors. All rights reserved.
 * Licensed under MIT License. See LICENSE in root directory for more information.
 */

import type { Cluster } from "../../common/cluster/cluster";
import type { Kubectl } from "../kubectl/kubectl";
import type WebSocket from "ws";
import { clearKubeconfigEnvVars } from "../utils/clear-kube-env-vars";
import path from "path";
import os, { userInfo } from "os";
import type * as pty from "node-pty";
import { appEventBus } from "../../common/app-event-bus/event-bus";
import logger from "../logger";
import { stat } from "fs/promises";
import { getOrInsertWith } from "../../common/utils";
import { type TerminalMessage, TerminalChannels } from "../../common/terminal/channels";
import type { Logger } from "../../common/logger";
import type { ComputeShellEnvironment } from "../utils/shell-env/compute-shell-environment.injectable";
import type { SpawnPty } from "./spawn-pty.injectable";
import type { InitializableState } from "../../common/initializable-state/create";

export class ShellOpenError extends Error {
  constructor(message: string, options?: ErrorOptions) {
    super(`${message}`, options);
    this.name = this.constructor.name;
    Error.captureStackTrace(this);
  }
}

export enum WebSocketCloseEvent {
  /**
   * The connection successfully completed the purpose for which it was created.
   */
  NormalClosure = 1000,
  /**
   * The endpoint is going away, either because of a server failure or because
   * the browser is navigating away from the page that opened the connection.
   */
  GoingAway = 1001,
  /**
   * The endpoint is terminating the connection due to a protocol error.
   */
  ProtocolError = 1002,
  /**
   * The connection is being terminated because the endpoint received data of a
   * type it cannot accept. (For example, a text-only endpoint received binary
   * data.)
   */
  UnsupportedData = 1003,
  /**
   * Indicates that no status code was provided even though one was expected.
   */
  NoStatusReceived = 1005,
  /**
   * Indicates that a connection was closed abnormally (that is, with no close
   * frame being sent) when a status code is expected.
   */
  AbnormalClosure = 1006,
  /**
   *  The endpoint is terminating the connection because a message was received
   * that contained inconsistent data (e.g., non-UTF-8 data within a text message).
   */
  InvalidFramePayloadData = 1007,
  /**
   * The endpoint is terminating the connection because it received a message
   * that violates its policy. This is a generic status code, used when codes
   * 1003 and 1009 are not suitable.
   */
  PolicyViolation = 1008,
  /**
   * The endpoint is terminating the connection because a data frame was
   * received that is too large.
   */
  MessageTooBig = 1009,
  /**
   * The client is terminating the connection because it expected the server to
   * negotiate one or more extension, but the server didn't.
   */
  MissingExtension = 1010,
  /**
   * The server is terminating the connection because it encountered an
   * unexpected condition that prevented it from fulfilling the request.
   */
  InternalError = 1011,
  /**
   * The server is terminating the connection because it is restarting.
   */
  ServiceRestart = 1012,
  /**
   * The server is terminating the connection due to a temporary condition,
   * e.g. it is overloaded and is casting off some of its clients.
   */
  TryAgainLater = 1013,
  /**
   * The server was acting as a gateway or proxy and received an invalid
   * response from the upstream server. This is similar to 502 HTTP Status Code.
   */
  BadGateway = 1014,
  /**
   * Indicates that the connection was closed due to a failure to perform a TLS
   * handshake (e.g., the server certificate can't be verified).
   */
  TlsHandshake = 1015,
}

export interface ShellSessionDependencies {
  readonly isWindows: boolean;
  readonly isMac: boolean;
  readonly logger: Logger;
  readonly resolvedShell: string | undefined;
  readonly appName: string;
  readonly buildVersion: InitializableState<string>;
  computeShellEnvironment: ComputeShellEnvironment;
  spawnPty: SpawnPty;
}

export interface ShellSessionArgs {
  kubectl: Kubectl;
  websocket: WebSocket;
  cluster: Cluster;
  tabId: string;
}

export abstract class ShellSession {
  abstract readonly ShellType: string;

  private static readonly shellEnvs = new Map<string, Record<string, string | undefined>>();
  private static readonly processes = new Map<string, pty.IPty>();

  /**
   * Kill all remaining shell backing processes. Should be called when about to
   * quit
   */
  public static cleanup(): void {
    for (const shellProcess of this.processes.values()) {
      try {
        process.kill(shellProcess.pid);
      } catch {
        // ignore error
      }
    }

    this.processes.clear();
  }

  protected running = false;
  protected readonly kubectlBinDirP: Promise<string>;
  protected readonly kubeconfigPathP: Promise<string>;
  protected readonly terminalId: string;
  protected readonly kubectl: Kubectl;
  protected readonly websocket: WebSocket;
  protected readonly cluster: Cluster;

  protected abstract get cwd(): string | undefined;

  protected ensureShellProcess(shell: string, args: string[], env: Partial<Record<string, string>>, cwd: string): { shellProcess: pty.IPty; resume: boolean } {
    const resume = ShellSession.processes.has(this.terminalId);
    const shellProcess = getOrInsertWith(ShellSession.processes, this.terminalId, () => (
      this.dependencies.spawnPty(shell, args, {
        rows: 30,
        cols: 80,
        cwd,
        env,
        name: "xterm-256color",
        // TODO: Something else is broken here so we need to force the use of winPty on windows
        useConpty: false,
      })
    ));

    logger.info(`[SHELL-SESSION]: PTY for ${this.terminalId} is ${resume ? "resumed" : "started"} with PID=${shellProcess.pid}`);

    return { shellProcess, resume };
  }

  constructor(protected readonly dependencies: ShellSessionDependencies, args: ShellSessionArgs) {
    this.cluster = args.cluster;
    this.kubectl = args.kubectl;
    this.websocket = args.websocket;
    this.kubeconfigPathP = this.cluster.getProxyKubeconfigPath();
    this.kubectlBinDirP = this.kubectl.binDir();
    this.terminalId = `${this.cluster.id}:${args.tabId}`;
  }

  protected send(message: TerminalMessage): void {
    this.websocket.send(JSON.stringify(message));
  }

  protected async getCwd(env: Record<string, string | undefined>): Promise<string> {
    const cwdOptions = [this.cwd];

    if (this.dependencies.isWindows) {
      cwdOptions.push(
        env.USERPROFILE,
        os.homedir(),
        "C:\\",
      );
    } else {
      cwdOptions.push(
        env.HOME,
        os.homedir(),
      );

      if (this.dependencies.isMac) {
        cwdOptions.push("/Users");
      } else {
        cwdOptions.push("/home");
      }
    }

    for (const potentialCwd of cwdOptions) {
      if (!potentialCwd) {
        continue;
      }

      try {
        const stats = await stat(potentialCwd);

        if (stats.isDirectory()) {
          return potentialCwd;
        }
      } catch {
        // ignore error
      }
    }

    return "."; // Always valid
  }

  protected async openShellProcess(shell: string, args: string[], env: Record<string, string | undefined>) {
    const cwd = await this.getCwd(env);
    const { shellProcess, resume } = this.ensureShellProcess(shell, args, env, cwd);

    if (resume) {
      this.send({ type: TerminalChannels.CONNECTED });
    }

    this.running = true;
    shellProcess.onData(data => this.send({ type: TerminalChannels.STDOUT, data }));
    shellProcess.onExit(({ exitCode }) => {
      logger.info(`[SHELL-SESSION]: shell has exited for ${this.terminalId} closed with exitcode=${exitCode}`);

      // This might already be false because of the kill() within the websocket.on("close") handler
      if (this.running) {
        this.running = false;

        if (exitCode > 0) {
          this.send({ type: TerminalChannels.STDOUT, data: "Terminal will auto-close in 15 seconds ..." });
          setTimeout(() => this.exit(), 15 * 1000);
        } else {
          this.exit();
        }
      }
    });

    this.websocket
      .on("message", (rawData: unknown): void => {
        if (!this.running) {
          return void logger.debug(`[SHELL-SESSION]: received message from ${this.terminalId}, but shellProcess isn't running`);
        }

        if (!(rawData instanceof Buffer)) {
          return void logger.error(`[SHELL-SESSION]: Received message non-buffer message.`, { rawData });
        }

        const data = rawData.toString();

        try {
          const message: TerminalMessage = JSON.parse(data);

          switch (message.type) {
            case TerminalChannels.STDIN:
              shellProcess.write(message.data);
              break;
            case TerminalChannels.RESIZE:
              shellProcess.resize(message.data.width, message.data.height);
              break;
            case TerminalChannels.PING:
              logger.silly(`[SHELL-SESSION]: ${this.terminalId} ping!`);
              break;
            default:
              logger.warn(`[SHELL-SESSION]: unknown or unhandleable message type for ${this.terminalId}`, message);
              break;
          }
        } catch (error) {
          logger.error(`[SHELL-SESSION]: failed to handle message for ${this.terminalId}`, error);
        }
      })
      .once("close", code => {
        logger.info(`[SHELL-SESSION]: websocket for ${this.terminalId} closed with code=${WebSocketCloseEvent[code]}(${code})`, { cluster: this.cluster.getMeta() });

        const stopShellSession = this.running
          && (
            (
              code !== WebSocketCloseEvent.AbnormalClosure
              && code !== WebSocketCloseEvent.GoingAway
            )
            || this.cluster.disconnected
          );

        if (stopShellSession) {
          this.running = false;

          try {
            logger.info(`[SHELL-SESSION]: Killing shell process (pid=${shellProcess.pid}) for ${this.terminalId}`);
            shellProcess.kill();
            ShellSession.processes.delete(this.terminalId);
          } catch (error) {
            logger.warn(`[SHELL-SESSION]: failed to kill shell process (pid=${shellProcess.pid}) for ${this.terminalId}`, error);
          }
        }
      });

    appEventBus.emit({ name: this.ShellType, action: "open" });
  }

  protected getPathEntries(): string[] {
    return [];
  }

  protected async getCachedShellEnv() {
    const { id: clusterId } = this.cluster;

    let env = ShellSession.shellEnvs.get(clusterId);

    if (!env) {
      env = await this.getShellEnv();
      ShellSession.shellEnvs.set(clusterId, env);
    } else {
      // refresh env in the background
      this.getShellEnv().then((shellEnv: any) => {
        ShellSession.shellEnvs.set(clusterId, shellEnv);
      });
    }

    return env;
  }

  protected async getShellEnv() {
    const shell = this.dependencies.resolvedShell || userInfo().shell;
    const result = await this.dependencies.computeShellEnvironment(shell);
    const rawEnv = (() => {
      if (result.callWasSuccessful) {
        return result.response ?? process.env;
      }

      return process.env;
    })();

    const env = clearKubeconfigEnvVars(JSON.parse(JSON.stringify(rawEnv)));
    const pathStr = [await this.kubectlBinDirP, ...this.getPathEntries(), env.PATH].join(path.delimiter);

    delete env.DEBUG; // don't pass DEBUG into shells

    if (this.dependencies.isWindows) {
      env.PTYSHELL = shell || "powershell.exe";
      env.PATH = pathStr;
      env.LENS_SESSION = "true";
      env.WSLENV = [
        env.WSLENV,
        "KUBECONFIG/up:LENS_SESSION/u",
      ]
        .filter(Boolean)
        .join(":");
    } else if (shell !== undefined) {
      env.PTYSHELL = shell;
      env.PATH = pathStr;
    } else {
      env.PTYSHELL = ""; // blank runs the system default shell
    }

    if (path.basename(env.PTYSHELL) === "zsh") {
      env.OLD_ZDOTDIR = env.ZDOTDIR || env.HOME;
      env.ZDOTDIR = await this.kubectlBinDirP;
      env.DISABLE_AUTO_UPDATE = "true";
    }

    env.PTYPID = process.pid.toString();
    env.KUBECONFIG = await this.kubeconfigPathP;
    env.TERM_PROGRAM = this.dependencies.appName;
    env.TERM_PROGRAM_VERSION = this.dependencies.buildVersion.get();

    if (this.cluster.preferences.httpsProxy) {
      env.HTTPS_PROXY = this.cluster.preferences.httpsProxy;
    }

    env.NO_PROXY = [
      "localhost",
      "127.0.0.1",
      env.NO_PROXY,
    ]
      .filter(Boolean)
      .join();

    return env;
  }

  protected exit(code = WebSocketCloseEvent.NormalClosure) {
    if (this.websocket.readyState == this.websocket.OPEN) {
      this.websocket.close(code);
    }
  }
}