import AdmZip from "adm-zip";
import { execSync } from "child_process";
import {
  existsSync,
  readdirSync,
  readFileSync,
  statSync,
  unlinkSync,
  writeFileSync,
} from "fs";
import { join } from "path";
import { status } from "minecraft-server-util";
import {
  MODS_DIR,
  CLIENT_MODS_DIR,
  MOD_METADATA_FILE,
  MC_SERVER_IP,
  MC_SERVER_PORT,
} from "./constants";
import { sendCommand } from "./rcon";
import { memo, invalidate } from "./cache";
import type { ModSide } from "./modrinth";

const MODS_CACHE_KEY = "mods:details";
const MODS_CACHE_TTL = 10_000;

export function invalidateModsCache(): void {
  invalidate("mods:");
}

const MODPACK_ZIP = "/var/www/minecraft/modpack.zip";
const MODPACK_MODS = "/var/www/minecraft/mods";

export type ModMeta = {
  modId: string;
  displayName: string;
  version: string;
  filename: string;
  size: string;
  side: ModSide;
};

// ── Mod metadata persistence ───────────────────────────────

type ModMetadataEntry = { projectId: string; side: ModSide };
type ModMetadataMap = Record<string, ModMetadataEntry>;

function loadModMetadata(): ModMetadataMap {
  try {
    return JSON.parse(readFileSync(MOD_METADATA_FILE, "utf8"));
  } catch {
    return {};
  }
}

function saveModMetadata(metadata: ModMetadataMap): void {
  writeFileSync(MOD_METADATA_FILE, JSON.stringify(metadata, null, 2));
}

export function addModMetadata(
  filename: string,
  entry: ModMetadataEntry
): void {
  const metadata = loadModMetadata();
  metadata[filename] = entry;
  saveModMetadata(metadata);
  invalidateModsCache();
}

export function removeModMetadata(filename: string): void {
  const metadata = loadModMetadata();
  delete metadata[filename];
  saveModMetadata(metadata);
}

// ── Read mod metadata from JAR files ────────────────────────

function extractToml(content: string, key: string): string | null {
  const regex = new RegExp(`^\\s*${key}\\s*=\\s*"([^"]*)"`, "m");
  const match = content.match(regex);
  return match ? match[1] : null;
}

type JarParseCacheEntry = {
  mtimeMs: number;
  size: number;
  meta: Omit<ModMeta, "side">;
};

const jarParseCache = new Map<string, JarParseCacheEntry>();

function parseJarMeta(
  dir: string,
  filename: string
): Omit<ModMeta, "side"> {
  let modId = "unknown";
  let displayName = filename
    .replace(/-(\d)/, " $1")
    .replace(".jar", "")
    .replace(/-/g, " ");
  let version = "";

  try {
    const zip = new AdmZip(join(dir, filename));
    const toml = zip.getEntry("META-INF/mods.toml");
    if (toml) {
      const content = toml.getData().toString("utf8");
      modId = extractToml(content, "modId") || modId;
      displayName = extractToml(content, "displayName") || displayName;
      version = extractToml(content, "version") || "";
    }
  } catch {
    // Use filename-based defaults
  }

  return {
    modId,
    displayName,
    version,
    filename,
    size: "",
  };
}

function extractModMeta(
  dir: string,
  filename: string
): Omit<ModMeta, "side"> {
  const filePath = join(dir, filename);
  const stat = statSync(filePath);
  const cacheKey = filePath;
  const cached = jarParseCache.get(cacheKey);

  if (cached && cached.mtimeMs === stat.mtimeMs && cached.size === stat.size) {
    return { ...cached.meta, size: (stat.size / 1024 / 1024).toFixed(1) + " MB" };
  }

  const meta = parseJarMeta(dir, filename);
  jarParseCache.set(cacheKey, {
    mtimeMs: stat.mtimeMs,
    size: stat.size,
    meta,
  });

  return { ...meta, size: (stat.size / 1024 / 1024).toFixed(1) + " MB" };
}

export function getModDetails(): ModMeta[] {
  return memo(MODS_CACHE_KEY, MODS_CACHE_TTL, computeModDetails);
}

function computeModDetails(): ModMeta[] {
  const metadata = loadModMetadata();

  // Server mods
  const serverFiles = readdirSync(MODS_DIR).filter((f) => f.endsWith(".jar"));
  const serverMods: ModMeta[] = serverFiles.map((f) => {
    const meta = extractModMeta(MODS_DIR, f);
    const stored = metadata[f];
    const side: ModSide = stored?.side === "server" ? "server" : stored?.side || "both";
    return { ...meta, side };
  });

  // Client mods
  let clientMods: ModMeta[] = [];
  if (existsSync(CLIENT_MODS_DIR)) {
    const clientFiles = readdirSync(CLIENT_MODS_DIR).filter((f) =>
      f.endsWith(".jar")
    );
    clientMods = clientFiles.map((f) => ({
      ...extractModMeta(CLIENT_MODS_DIR, f),
      side: "client" as ModSide,
    }));
  }

  return [...serverMods, ...clientMods];
}

// ── Remove a single mod ─────────────────────────────────────

export function removeMod(filename: string): void {
  const serverPath = join(MODS_DIR, filename);
  const clientPath = join(CLIENT_MODS_DIR, filename);

  if (existsSync(serverPath)) {
    unlinkSync(serverPath);
    jarParseCache.delete(serverPath);
  } else if (existsSync(clientPath)) {
    unlinkSync(clientPath);
    jarParseCache.delete(clientPath);
  } else {
    throw new Error(`Mod "${filename}" not found`);
  }

  removeModMetadata(filename);
  invalidateModsCache();
}

export function isClientOnlyMod(filename: string): boolean {
  return (
    !existsSync(join(MODS_DIR, filename)) &&
    existsSync(join(CLIENT_MODS_DIR, filename))
  );
}

// ── Server health check ─────────────────────────────────────

export type HealthProgress = {
  phase: "waiting" | "process-alive" | "port-open" | "rcon-ready" | "failed" | "process-died";
  elapsed: number;
  message: string;
};

export async function waitForServerAdaptive(
  onProgress?: (p: HealthProgress) => void | Promise<void>,
  options?: { initialDelayMs?: number; maxWaitMs?: number }
): Promise<boolean> {
  const { initialDelayMs = 8000, maxWaitMs = 600000 } = options ?? {};
  const start = Date.now();
  const elapsed = () => Date.now() - start;
  const elapsedSec = () => Math.round(elapsed() / 1000);

  const report = async (phase: HealthProgress["phase"], message: string) => {
    await onProgress?.({ phase, elapsed: elapsed(), message });
  };

  await report("waiting", "Waiting for server process...");
  await sleep(initialDelayMs);

  let rconFailsWhileActive = 0;

  while (elapsed() < maxWaitMs) {
    // Tier 1: is the process alive?
    let serviceState: string;
    try {
      serviceState = execSync("systemctl is-active minecraft.service", {
        encoding: "utf8",
      }).trim();
    } catch {
      await report("process-died", "Server process is not running");
      return false;
    }

    if (serviceState !== "active" && serviceState !== "activating") {
      await report("process-died", `Server process state: ${serviceState}`);
      return false;
    }

    await report("process-alive", `Server process alive (${elapsedSec()}s)`);

    // Tier 2: try RCON directly — this is the definitive "server is ready" signal
    // RCON only starts after the server is fully loaded ("Done!")
    try {
      await sendCommand("list");
      await report("rcon-ready", "Server is fully online");
      return true;
    } catch {
      rconFailsWhileActive++;
    }

    // Tier 3: if RCON keeps failing, try MC protocol ping as fallback
    // (handles case where RCON is misconfigured but server is actually ready)
    if (rconFailsWhileActive >= 6) {
      try {
        await status(MC_SERVER_IP, MC_SERVER_PORT, { timeout: 3000 });
        await report("port-open", "Server is online (port verified, RCON unavailable)");
        return true;
      } catch {}
    }

    await sleep(3000);
  }

  await report("failed", `Server did not respond within ${Math.round(maxWaitMs / 1000)}s`);
  return false;
}

export async function waitForServer(timeoutMs = 600000): Promise<boolean> {
  return waitForServerAdaptive(undefined, { maxWaitMs: timeoutMs });
}

function sleep(ms: number): Promise<void> {
  return new Promise((r) => setTimeout(r, ms));
}

// ── Modpack rebuild ─────────────────────────────────────────

export function rebuildModpack(): void {
  // Zip server mods
  execSync(
    `cd ${MODS_DIR} && rm -f /tmp/modpack-rebuild.zip && zip -j /tmp/modpack-rebuild.zip *.jar`,
    { encoding: "utf8" }
  );

  // Add client mods to the same zip
  if (existsSync(CLIENT_MODS_DIR)) {
    try {
      execSync(
        `cd ${CLIENT_MODS_DIR} && zip -j /tmp/modpack-rebuild.zip *.jar 2>/dev/null || true`,
        { encoding: "utf8" }
      );
    } catch {}
  }

  // Copy to web root
  execSync(`sudo cp /tmp/modpack-rebuild.zip ${MODPACK_ZIP}`);
  execSync(`sudo rm -f ${MODPACK_MODS}/*.jar`);
  execSync(`sudo cp ${MODS_DIR}/*.jar ${MODPACK_MODS}/`);

  if (existsSync(CLIENT_MODS_DIR)) {
    try {
      execSync(
        `sudo cp ${CLIENT_MODS_DIR}/*.jar ${MODPACK_MODS}/ 2>/dev/null || true`
      );
    } catch {}
  }

  // Generate modlist from both directories
  execSync(
    `(ls ${MODS_DIR}/*.jar -1 2>/dev/null; ls ${CLIENT_MODS_DIR}/*.jar -1 2>/dev/null) | xargs -I{} basename {} | sort | sudo tee /var/www/minecraft/modlist.txt > /dev/null`
  );
}