import { createHash } from "node:crypto";
import { mkdir, writeFile, readFile, unlink, access } from "node:fs/promises";
import { join, extname, resolve } from "node:path";
import { prisma } from "@/lib/prisma";
import { env } from "@/lib/env";

export const FILE_KINDS = ["step", "pdf", "dxf", "svg", "png", "jpg", "other"] as const;
export type FileKind = (typeof FILE_KINDS)[number];

const EXT_TO_KIND: Record<string, FileKind> = {
  ".step": "step",
  ".stp": "step",
  ".pdf": "pdf",
  ".dxf": "dxf",
  ".svg": "svg",
  ".png": "png",
  ".jpg": "jpg",
  ".jpeg": "jpg",
};

const MAX_SIZE = 100 * 1024 * 1024; // 100 MB per file

export function classifyKind(filename: string, mimeType?: string | null): FileKind {
  const ext = extname(filename).toLowerCase();
  if (EXT_TO_KIND[ext]) return EXT_TO_KIND[ext];
  if (mimeType?.startsWith("image/")) {
    if (mimeType.includes("png")) return "png";
    if (mimeType.includes("jpeg") || mimeType.includes("jpg")) return "jpg";
    if (mimeType.includes("svg")) return "svg";
  }
  if (mimeType === "application/pdf") return "pdf";
  return "other";
}

function uploadRoot(): string {
  return resolve(env.UPLOAD_DIR);
}

export function storagePathFor(sha256: string, kind: FileKind, originalName: string): {
  relative: string;
  absolute: string;
} {
  const ext = extname(originalName).toLowerCase() || `.${kind}`;
  const shard = sha256.slice(0, 2);
  const relative = join(kind, shard, `${sha256}${ext}`);
  return {
    relative,
    absolute: join(uploadRoot(), relative),
  };
}

export async function fileExistsOnDisk(absolutePath: string): Promise<boolean> {
  try {
    await access(absolutePath);
    return true;
  } catch {
    return false;
  }
}

export interface SavedFile {
  id: string;
  kind: FileKind;
  sha256: string;
  path: string;
  sizeBytes: number;
  originalName: string;
  mimeType: string | null;
  deduped: boolean;
}

export async function saveUploadedFile(
  file: File,
  uploadedBy: string | null,
): Promise<SavedFile> {
  if (file.size === 0) throw new Error("Empty file");
  if (file.size > MAX_SIZE) throw new Error(`File too large (max ${MAX_SIZE / 1024 / 1024}MB)`);

  const arrayBuffer = await file.arrayBuffer();
  const buffer = Buffer.from(arrayBuffer);
  const sha256 = createHash("sha256").update(buffer).digest("hex");
  const kind = classifyKind(file.name, file.type || null);

  const existing = await prisma.fileAsset.findUnique({ where: { sha256 } });
  if (existing) {
    return {
      id: existing.id,
      kind: existing.kind as FileKind,
      sha256: existing.sha256,
      path: existing.path,
      sizeBytes: existing.sizeBytes,
      originalName: existing.originalName,
      mimeType: existing.mimeType,
      deduped: true,
    };
  }

  const { relative, absolute } = storagePathFor(sha256, kind, file.name);
  await mkdir(join(absolute, ".."), { recursive: true });
  await writeFile(absolute, buffer);

  const asset = await prisma.fileAsset.create({
    data: {
      kind,
      originalName: file.name,
      path: relative,
      sizeBytes: file.size,
      mimeType: file.type || null,
      sha256,
      uploadedBy,
    },
  });

  return {
    id: asset.id,
    kind: asset.kind as FileKind,
    sha256: asset.sha256,
    path: asset.path,
    sizeBytes: asset.sizeBytes,
    originalName: asset.originalName,
    mimeType: asset.mimeType,
    deduped: false,
  };
}

export async function readFileBytes(relative: string): Promise<Buffer> {
  const absolute = resolve(uploadRoot(), relative);
  const root = uploadRoot();
  if (!absolute.startsWith(root + "/") && !absolute.startsWith(root + "\\") && absolute !== root) {
    throw new Error("Invalid file path");
  }
  return readFile(absolute);
}

export async function deleteFileFromDisk(relative: string): Promise<void> {
  const absolute = resolve(uploadRoot(), relative);
  const root = uploadRoot();
  if (!absolute.startsWith(root + "/") && !absolute.startsWith(root + "\\") && absolute !== root) {
    throw new Error("Invalid file path");
  }
  await unlink(absolute).catch(() => undefined);
}

export function mimeForKind(kind: FileKind, originalMime: string | null): string {
  if (originalMime) return originalMime;
  switch (kind) {
    case "pdf":
      return "application/pdf";
    case "png":
      return "image/png";
    case "jpg":
      return "image/jpeg";
    case "svg":
      return "image/svg+xml";
    case "step":
      return "application/step";
    case "dxf":
      return "application/dxf";
    default:
      return "application/octet-stream";
  }
}