import { existsSync, mkdirSync, writeFileSync } from "fs";
import { join } from "path";
import { MODS_DIR, CLIENT_MODS_DIR } from "./constants";
import { getModDetails } from "./mods";

const API = "https://api.modrinth.com/v2";
const GAME_VERSION = "1.20.1";
const LOADER = "forge";

export type ModSide = "client" | "server" | "both";

export type SearchResult = {
  slug: string;
  title: string;
  description: string;
  icon_url: string;
  downloads: number;
  project_id: string;
  author: string;
  date_modified: string;
  follows: number;
};

export type ModDownload = {
  projectId: string;
  versionId: string;
  title: string;
  filename: string;
  url: string;
  isDependency: boolean;
  alreadyInstalled: boolean;
  side: ModSide;
};

export type ResolveResult = {
  toInstall: ModDownload[];
  skipped: ModDownload[];
  conflicts: string[];
};

// ── Search ──────────────────────────────────────────────────

export async function searchMods(query: string): Promise<SearchResult[]> {
  const facets = JSON.stringify([
    [`categories:${LOADER}`],
    [`versions:${GAME_VERSION}`],
    ["project_type:mod"],
  ]);
  const url = `${API}/search?query=${encodeURIComponent(query)}&facets=${encodeURIComponent(facets)}&limit=12`;

  const res = await fetch(url, {
    headers: { "User-Agent": "HurkiCorgiMC/1.0 (minecraft.hurkicorgi.com)" },
  });

  if (!res.ok) throw new Error(`Modrinth search failed: ${res.status}`);

  const data = await res.json();
  return data.hits.map((h: Record<string, unknown>) => ({
    slug: h.slug as string,
    title: h.title as string,
    description: h.description as string,
    icon_url: (h.icon_url as string) || "",
    downloads: (h.downloads as number) ?? 0,
    project_id: h.project_id as string,
    author: (h.author as string) || "",
    date_modified: (h.date_modified as string) || "",
    follows: (h.follows as number) ?? 0,
  }));
}

// ── Get project details (title + side info) ─────────────────

type ProjectDetails = {
  title: string;
  client_side: string;
  server_side: string;
};

async function getProjectDetails(
  projectId: string
): Promise<ProjectDetails | null> {
  try {
    const res = await fetch(`${API}/project/${projectId}`, {
      headers: {
        "User-Agent": "HurkiCorgiMC/1.0 (minecraft.hurkicorgi.com)",
      },
    });
    if (!res.ok) return null;
    const data = await res.json();
    return {
      title: data.title || projectId,
      client_side: data.client_side || "optional",
      server_side: data.server_side || "optional",
    };
  } catch {
    return null;
  }
}

export function classifySide(
  client_side: string,
  server_side: string
): ModSide {
  if (server_side === "unsupported") return "client";
  if (client_side === "unsupported") return "server";
  return "both";
}

// ── Get latest version for a project ────────────────────────

type VersionFile = { url: string; filename: string };
type VersionDep = {
  project_id: string | null;
  dependency_type: string;
};
type VersionData = {
  id: string;
  name: string;
  files: VersionFile[];
  dependencies: VersionDep[];
};

export async function getLatestVersion(
  projectId: string
): Promise<VersionData | null> {
  const url = `${API}/project/${projectId}/version?game_versions=["${GAME_VERSION}"]&loaders=["${LOADER}"]`;

  const res = await fetch(url, {
    headers: { "User-Agent": "HurkiCorgiMC/1.0 (minecraft.hurkicorgi.com)" },
  });

  if (!res.ok) return null;

  const versions: VersionData[] = await res.json();
  return versions.length > 0 ? versions[0] : null;
}

// ── Resolve dependencies ────────────────────────────────────

export async function resolveDependencies(
  projectIds: string[],
  titles: Record<string, string>
): Promise<ResolveResult> {
  // Cache installed mods once for the entire resolution
  const installed = getModDetails();
  const toInstall: ModDownload[] = [];
  const skipped: ModDownload[] = [];
  const conflicts: string[] = [];
  const visited = new Set<string>();
  const queue = projectIds.map((id) => ({ id, isDep: false }));

  while (queue.length > 0) {
    const item = queue.shift()!;
    if (visited.has(item.id)) continue;
    visited.add(item.id);

    const [version, details] = await Promise.all([
      getLatestVersion(item.id),
      getProjectDetails(item.id),
    ]);

    if (!version || version.files.length === 0) {
      if (!item.isDep) {
        conflicts.push(
          `"${titles[item.id] || item.id}" has no Forge 1.20.1 version available`
        );
      }
      continue;
    }

    const title = titles[item.id] || details?.title || item.id;
    const side = details
      ? classifySide(details.client_side, details.server_side)
      : "both";
    const file = version.files[0];

    const mod: ModDownload = {
      projectId: item.id,
      versionId: version.id,
      title,
      filename: file.filename,
      url: file.url,
      isDependency: item.isDep,
      alreadyInstalled: false,
      side,
    };

    // Check if already installed (by filename as rough proxy)
    const filenameBase = file.filename.replace(/-[\d.]+.*\.jar$/, "").toLowerCase();
    const isInstalled = installed.some(
      (m) =>
        m.filename === file.filename ||
        m.filename.toLowerCase().startsWith(filenameBase)
    );

    if (isInstalled) {
      mod.alreadyInstalled = true;
      skipped.push(mod);
    } else {
      toInstall.push(mod);
    }

    // Queue required dependencies
    for (const dep of version.dependencies) {
      if (
        dep.dependency_type === "required" &&
        dep.project_id &&
        !visited.has(dep.project_id)
      ) {
        queue.push({ id: dep.project_id, isDep: true });
      }
    }
  }

  return { toInstall, skipped, conflicts };
}

// ── Download a mod ──────────────────────────────────────────

export async function downloadMod(
  url: string,
  filename: string,
  side: ModSide = "both"
): Promise<void> {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`Failed to download ${filename}: ${res.status}`);

  const targetDir = side === "client" ? CLIENT_MODS_DIR : MODS_DIR;
  if (side === "client" && !existsSync(CLIENT_MODS_DIR)) {
    mkdirSync(CLIENT_MODS_DIR, { recursive: true });
  }

  const buffer = Buffer.from(await res.arrayBuffer());
  writeFileSync(join(targetDir, filename), buffer);
}