import fs from "node:fs";
import path from "node:path";
import { dbGlobal } from "drizzle-pkg/lib/db";
import { mediaAssets, postMediaRefs } from "drizzle-pkg/lib/schema/content";
import { count, eq } from "drizzle-orm";
import { RELATIVE_ASSETS_DIR } from "#server/constants/media";

function assetsBaseDir(): string {
  return path.resolve(process.cwd(), RELATIVE_ASSETS_DIR);
}

function isSafeStorageKey(key: string): boolean {
  if (!key || key !== path.basename(key)) {
    return false;
  }
  return !key.includes("..");
}

function resolvedFilePath(storageKey: string): string | null {
  if (!isSafeStorageKey(storageKey)) {
    return null;
  }
  const base = assetsBaseDir();
  const full = path.resolve(base, storageKey);
  const prefix = base + path.sep;
  if (full !== base && !full.startsWith(prefix)) {
    return null;
  }
  return full;
}

export type StorageAuditMissingRow = {
  id: number;
  userId: number;
  storageKey: string;
  refCount: number;
};

export type StorageAuditResult = {
  scannedAt: string;
  dbRowCount: number;
  diskFileCount: number;
  missingOnDisk: StorageAuditMissingRow[];
  invalidStorageKey: Array<{ id: number; userId: number; storageKey: string; refCount: number }>;
  onDiskNotInDb: string[];
};

export async function auditMediaStorageVsDb(): Promise<StorageAuditResult> {
  const base = assetsBaseDir();
  const rows = await dbGlobal
    .select({
      id: mediaAssets.id,
      userId: mediaAssets.userId,
      storageKey: mediaAssets.storageKey,
    })
    .from(mediaAssets);

  const refAgg = await dbGlobal
    .select({
      assetId: postMediaRefs.assetId,
      c: count(),
    })
    .from(postMediaRefs)
    .groupBy(postMediaRefs.assetId);

  const refMap = new Map<number, number>();
  for (const r of refAgg) {
    refMap.set(r.assetId, r.c);
  }

  const dbKeys = new Set<string>();
  const missingOnDisk: StorageAuditMissingRow[] = [];
  const invalidStorageKey: StorageAuditMissingRow[] = [];

  for (const r of rows) {
    const refCount = refMap.get(r.id) ?? 0;
    if (!isSafeStorageKey(r.storageKey)) {
      invalidStorageKey.push({
        id: r.id,
        userId: r.userId,
        storageKey: r.storageKey,
        refCount,
      });
      continue;
    }
    dbKeys.add(r.storageKey);
    const full = resolvedFilePath(r.storageKey);
    if (!full) {
      invalidStorageKey.push({
        id: r.id,
        userId: r.userId,
        storageKey: r.storageKey,
        refCount,
      });
      continue;
    }
    if (!fs.existsSync(full)) {
      missingOnDisk.push({
        id: r.id,
        userId: r.userId,
        storageKey: r.storageKey,
        refCount,
      });
    }
  }

  let diskFileCount = 0;
  const onDiskNotInDb: string[] = [];
  if (!fs.existsSync(base)) {
    return {
      scannedAt: new Date().toISOString(),
      dbRowCount: rows.length,
      diskFileCount: 0,
      missingOnDisk,
      invalidStorageKey,
      onDiskNotInDb: [],
    };
  }

  const dirents = await fs.promises.readdir(base, { withFileTypes: true });
  for (const e of dirents) {
    if (!e.isFile()) {
      continue;
    }
    if (e.name.startsWith(".")) {
      continue;
    }
    diskFileCount += 1;
    if (!dbKeys.has(e.name)) {
      onDiskNotInDb.push(e.name);
    }
  }
  onDiskNotInDb.sort();

  return {
    scannedAt: new Date().toISOString(),
    dbRowCount: rows.length,
    diskFileCount,
    missingOnDisk,
    invalidStorageKey,
    onDiskNotInDb,
  };
}

/**
 * 删除「磁盘上不存在」且「无任何文章引用」的 media_assets 行（不尝试 unlink）。
 */
export async function removeUnreferencedDbRowsForMissingFiles(): Promise<{
  removed: number;
  removedIds: number[];
}> {
  const audit = await auditMediaStorageVsDb();
  const candidates = audit.missingOnDisk.filter((m) => m.refCount === 0);
  if (candidates.length === 0) {
    return { removed: 0, removedIds: [] };
  }

  const removedIds: number[] = [];

  for (const c of candidates) {
    const full = resolvedFilePath(c.storageKey);
    if (!full) {
      continue;
    }
    if (fs.existsSync(full)) {
      continue;
    }
    const [{ n }] = await dbGlobal
      .select({ n: count() })
      .from(postMediaRefs)
      .where(eq(postMediaRefs.assetId, c.id));
    if (n > 0) {
      continue;
    }
    await dbGlobal.delete(mediaAssets).where(eq(mediaAssets.id, c.id));
    removedIds.push(c.id);
  }

  return { removed: removedIds.length, removedIds };
}