import { isError } from "es-toolkit";

import type { CheckResult, RawTargetConfig } from "../../types";
import type { CheckerContext, CheckerDefinition, CheckerValidationInput, ResolveContext } from "../types";
import type { RawTcpExpectConfig, ResolvedTcpExpectConfig, ResolvedTcpTarget, TcpTargetConfig } from "./types";

import { resolveContentExpectations } from "../../expect/content";
import { errorFailure } from "../../expect/failure";
import { checkValueExpectation, resolveValueExpectation } from "../../expect/value";
import { parseSize } from "../../utils";
import { checkBanner, checkConnected } from "./expect";
import { tcpCheckerSchemas } from "./schema";
import { validateTcpConfig } from "./validate";

const DEFAULT_BANNER_READ_TIMEOUT = 2000;
const DEFAULT_MAX_BANNER_BYTES = 4096;

type ConnectAndBannerResult =
  | { banner?: string; bannerExceeded?: boolean; connectTimeMs: number; ok: true; socket: { close(): void } }
  | { error: string; ok: false };

export class TcpChecker implements CheckerDefinition<ResolvedTcpTarget> {
  readonly configKey = "tcp";

  readonly schemas = tcpCheckerSchemas;

  readonly type = "tcp";

  buildDetail(observation: Record<string, unknown>): null | string {
    const connected = observation["connected"];
    if (connected !== true) {
      const error = observation["error"];
      return typeof error === "string" ? `connection failed: ${error}` : "not connected";
    }
    const connectTimeMs = observation["connectTimeMs"];
    const banner = observation["banner"];
    const parts: string[] = [`connected in ${typeof connectTimeMs === "number" ? connectTimeMs : "?"}ms`];
    if (typeof banner === "string" && banner.length > 0) {
      parts.push(`banner: ${truncateBanner(banner)}`);
    }
    return parts.join(", ");
  }

  async execute(t: ResolvedTcpTarget, ctx: CheckerContext): Promise<CheckResult> {
    const timestamp = new Date().toISOString();
    const start = performance.now();
    const expect = t.expect;

    try {
      const connectResult = await connectAndMaybeReadBanner(
        t.tcp.host,
        t.tcp.port,
        t.tcp.readBanner,
        t.tcp.bannerReadTimeout,
        t.tcp.maxBannerBytes,
        ctx.signal,
      );

      if (!connectResult.ok) {
        const durationMs = Math.round(performance.now() - start);
        const observation: Record<string, unknown> = {
          banner: null,
          connected: false,
          connectTimeMs: null,
          error: connectResult.error,
        };
        if (expect?.connected === false) {
          return {
            detail: null,
            durationMs,
            failure: null,
            matched: true,
            observation,
            targetId: t.id,
            timestamp,
          };
        }
        return {
          detail: null,
          durationMs,
          failure: errorFailure("connect", "connect", connectResult.error),
          matched: false,
          observation,
          targetId: t.id,
          timestamp,
        };
      }

      const socket = connectResult.socket;
      const connectTimeMs = connectResult.connectTimeMs;

      if (ctx.signal.aborted) {
        closeSocket(socket);
        const durationMs = Math.round(performance.now() - start);
        return {
          detail: null,
          durationMs,
          failure: errorFailure("connect", "connect", `连接超时 (${t.timeoutMs}ms)`),
          matched: false,
          observation: null,
          targetId: t.id,
          timestamp,
        };
      }

      const expectedConnected = expect?.connected ?? true;
      const connectedResult = checkConnected(true, expectedConnected);
      if (!connectedResult.matched) {
        closeSocket(socket);
        const durationMs = Math.round(performance.now() - start);
        return {
          detail: null,
          durationMs,
          failure: connectedResult.failure,
          matched: false,
          observation: { banner: null, connected: true, connectTimeMs, error: null },
          targetId: t.id,
          timestamp,
        };
      }

      if (connectResult.bannerExceeded) {
        closeSocket(socket);
        const durationMs = Math.round(performance.now() - start);
        return {
          detail: null,
          durationMs,
          failure: errorFailure("banner", "banner", `banner 数据超过 ${t.tcp.maxBannerBytes} 字节限制`),
          matched: false,
          observation: { banner: null, connected: true, connectTimeMs, error: null },
          targetId: t.id,
          timestamp,
        };
      }

      const banner = connectResult.banner ?? "";
      closeSocket(socket);

      const observation: Record<string, unknown> = {
        banner: banner ? truncateBannerForObservation(banner) : null,
        connected: true,
        connectTimeMs,
        error: null,
      };

      if (expect?.banner) {
        const bannerCheck = checkBanner(banner, expect.banner);
        if (!bannerCheck.matched) {
          const durationMs = Math.round(performance.now() - start);
          return {
            detail: null,
            durationMs,
            failure: bannerCheck.failure,
            matched: false,
            observation,
            targetId: t.id,
            timestamp,
          };
        }
      }

      const durationMs = Math.round(performance.now() - start);
      const durationResult = checkValueExpectation(durationMs, expect?.durationMs, {
        message: "durationMs mismatch",
        path: "durationMs",
        phase: "duration",
      });
      if (!durationResult.matched) {
        return {
          detail: null,
          durationMs,
          failure: durationResult.failure,
          matched: false,
          observation,
          targetId: t.id,
          timestamp,
        };
      }

      return {
        detail: null,
        durationMs,
        failure: null,
        matched: true,
        observation,
        targetId: t.id,
        timestamp,
      };
    } catch (error) {
      const durationMs = Math.round(performance.now() - start);
      return {
        detail: null,
        durationMs,
        failure: errorFailure(
          "connect",
          "connect",
          ctx.signal.aborted ? `连接超时 (${t.timeoutMs}ms)` : isError(error) ? error.message : String(error),
        ),
        matched: false,
        observation: null,
        targetId: t.id,
        timestamp,
      };
    }
  }

  resolve(target: RawTargetConfig, context: ResolveContext): ResolvedTcpTarget {
    const t = target as RawTargetConfig & { tcp: TcpTargetConfig; type: "tcp" };

    const maxBannerBytes = parseSize(t.tcp.maxBannerBytes ?? DEFAULT_MAX_BANNER_BYTES);
    const bannerReadTimeout = t.tcp.bannerReadTimeout ?? DEFAULT_BANNER_READ_TIMEOUT;

    const rawExpect = target.expect as RawTcpExpectConfig | undefined;
    const resolvedExpect: ResolvedTcpExpectConfig = rawExpect
      ? {
          banner: resolveContentExpectations(rawExpect.banner),
          connected: rawExpect.connected ?? true,
          durationMs: resolveValueExpectation(rawExpect.durationMs),
        }
      : { connected: true };

    return {
      description: null,
      expect: resolvedExpect,
      group: target.group ?? "default",
      id: t.id,
      intervalMs: context.defaultIntervalMs,
      name: t.name ?? null,
      rawExpect,
      tcp: {
        bannerReadTimeout,
        host: t.tcp.host,
        maxBannerBytes,
        port: t.tcp.port,
        readBanner: t.tcp.readBanner ?? false,
      },
      timeoutMs: context.defaultTimeoutMs,
      type: "tcp",
    } satisfies ResolvedTcpTarget;
  }

  serialize(t: ResolvedTcpTarget): { config: string; target: string } {
    return {
      config: JSON.stringify({
        bannerReadTimeout: t.tcp.bannerReadTimeout,
        host: t.tcp.host,
        maxBannerBytes: t.tcp.maxBannerBytes,
        port: t.tcp.port,
        readBanner: t.tcp.readBanner,
      }),
      target: `${t.tcp.host}:${t.tcp.port}`,
    };
  }

  validate(input: CheckerValidationInput) {
    return validateTcpConfig(input);
  }
}

function assembleChunks(chunks: Uint8Array[], totalBytes: number): Uint8Array {
  const result = new Uint8Array(totalBytes);
  let offset = 0;
  for (const chunk of chunks) {
    result.set(chunk, offset);
    offset += chunk.byteLength;
  }
  return result;
}

function closeSocket(socket: { close(): void }) {
  try {
    socket.close();
  } catch {
    /* best-effort close */
  }
}

async function connectAndMaybeReadBanner(
  hostname: string,
  port: number,
  readBanner: boolean,
  bannerTimeoutMs: number,
  maxBannerBytes: number,
  signal: AbortSignal,
): Promise<ConnectAndBannerResult> {
  const chunks: Uint8Array[] = [];
  let totalBytes = 0;
  let bannerSettled = false;
  let bannerExceeded = false;
  let bannerResolve: ((value: void) => void) | undefined;
  const bannerPromise = new Promise<void>((resolve) => {
    bannerResolve = resolve;
  });

  const socketHandlers: Record<string, (...args: unknown[]) => void> = {
    close() {
      if (readBanner && !bannerSettled) {
        bannerSettled = true;
        bannerResolve!();
      }
    },
    data(_socket: unknown, data: unknown) {
      if (!readBanner || bannerSettled) return;
      const bytes = data as Uint8Array;
      totalBytes += bytes.byteLength;
      if (totalBytes > maxBannerBytes) {
        bannerSettled = true;
        bannerExceeded = true;
        bannerResolve!();
        return;
      }
      chunks.push(bytes);
    },
    drain() {
      // Bun socket handler 必填项，TCP checker 不关注 drain 事件
    },
    end() {
      if (readBanner && !bannerSettled) {
        bannerSettled = true;
        bannerResolve!();
      }
    },
    error() {
      if (readBanner && !bannerSettled) {
        bannerSettled = true;
        bannerResolve!();
      }
    },
    open() {
      // Bun socket handler 必填项，连接成功由 Bun.connect() resolve 表示
    },
  };

  try {
    const connectStart = performance.now();
    const socket = await Bun.connect({
      hostname,
      port,
      socket: socketHandlers,
    });
    const connectTimeMs = Math.round(performance.now() - connectStart);

    if (signal.aborted) {
      closeSocket(socket);
      return { error: "连接已取消", ok: false };
    }

    if (!readBanner) {
      return { bannerExceeded: false, connectTimeMs, ok: true, socket };
    }

    const timer = setTimeout(() => {
      if (bannerSettled) return;
      bannerSettled = true;
      bannerResolve!();
    }, bannerTimeoutMs);

    const onAbort = () => {
      if (bannerSettled) return;
      bannerSettled = true;
      clearTimeout(timer);
      bannerResolve!();
    };

    if (signal.aborted) {
      clearTimeout(timer);
      closeSocket(socket);
      return { error: "连接已取消", ok: false };
    }
    signal.addEventListener("abort", onAbort, { once: true });

    await bannerPromise;
    clearTimeout(timer);
    signal.removeEventListener("abort", onAbort);

    if (bannerExceeded) {
      return { bannerExceeded: true, connectTimeMs, ok: true, socket };
    }

    const banner = new TextDecoder().decode(assembleChunks(chunks, totalBytes));
    return { banner, bannerExceeded: false, connectTimeMs, ok: true, socket };
  } catch (error) {
    if (signal.aborted) {
      return { error: "连接超时", ok: false };
    }
    const message = isError(error) ? error.message : String(error);
    return { error: simplifyConnectError(message), ok: false };
  }
}

function simplifyConnectError(message: string): string {
  const lower = message.toLowerCase();
  if (lower.includes("econnrefused") || lower.includes("connection refused")) return "connection refused";
  if (lower.includes("enoent") || lower.includes("not found")) return "host not found";
  if (lower.includes("etimedout") || lower.includes("timed out")) return "connection timed out";
  if (lower.includes("econnreset") || lower.includes("reset")) return "connection reset";
  if (lower.includes("enetwork") || lower.includes("network")) return "network error";
  return message;
}

function truncateBanner(banner: string, maxLen = 80): string {
  if (banner.length <= maxLen) return banner;
  return `${banner.slice(0, maxLen)}…`;
}

function truncateBannerForObservation(banner: string, maxLen = 256): string {
  if (banner.length <= maxLen) return banner;
  return banner.slice(0, maxLen);
}