import fs from "node:fs";
import path from "node:path";
import { dbGlobal } from "drizzle-pkg/lib/db";
import { mediaAssets, mediaRefs } from "drizzle-pkg/lib/schema/content";
import { and, count, desc, eq, inArray, isNotNull, isNull, lte, not, notExists, or, sql } from "drizzle-orm";
import {
  MEDIA_ORPHAN_GRACE_HOURS_AFTER_DEREF,
  MEDIA_ORPHAN_GRACE_HOURS_NEVER_REF,
  POST_MEDIA_PUBLIC_PREFIX,
  RELATIVE_ASSETS_DIR,
} from "#server/constants/media";
import { mergePostMediaUrls, publicAssetUrlToStorageKey } from "#server/utils/post-media-urls";
import { nextIntegerId } from "#server/utils/sqlite-id";

const NEVER_REF_MS = MEDIA_ORPHAN_GRACE_HOURS_NEVER_REF * 3600 * 1000;
const AFTER_DEREF_MS = MEDIA_ORPHAN_GRACE_HOURS_AFTER_DEREF * 3600 * 1000;

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

function isPathUnderAssetsDir(resolvedFile: string): boolean {
  const base = assetsBaseDir() + path.sep;
  return resolvedFile === assetsBaseDir() || resolvedFile.startsWith(base);
}

/** 删除主文件及 variantsJson 中列出的、位于 assets 目录下的相对路径 */
async function unlinkMediaFiles(storageKey: string, variantsJson: string | null): Promise<void> {
  const main = path.resolve(assetsBaseDir(), storageKey);
  if (!isPathUnderAssetsDir(main)) {
    return;
  }
  try {
    await fs.promises.unlink(main);
  } catch (e) {
    if ((e as NodeJS.ErrnoException).code !== "ENOENT") {
      throw e;
    }
  }

  const rels = parseVariantRelativePaths(variantsJson);
  for (const rel of rels) {
    if (rel.includes("..") || path.isAbsolute(rel)) {
      continue;
    }
    const full = path.resolve(assetsBaseDir(), rel);
    if (!isPathUnderAssetsDir(full)) {
      continue;
    }
    try {
      await fs.promises.unlink(full);
    } catch (e) {
      if ((e as NodeJS.ErrnoException).code !== "ENOENT") {
        throw e;
      }
    }
  }
}

function parseVariantRelativePaths(raw: string | null): string[] {
  if (!raw) {
    return [];
  }
  try {
    const j = JSON.parse(raw) as unknown;
    if (!Array.isArray(j)) {
      return [];
    }
    return j.filter((x): x is string => typeof x === "string" && x.length > 0);
  } catch {
    return [];
  }
}

export function isAssetDeletable(row: {
  firstReferencedAt: Date | null;
  dereferencedAt: Date | null;
  createdAt: Date;
}): boolean {
  const now = Date.now();
  if (row.firstReferencedAt == null) {
    return row.createdAt.getTime() <= now - NEVER_REF_MS;
  }
  if (row.dereferencedAt == null) {
    return false;
  }
  return row.dereferencedAt.getTime() <= now - AFTER_DEREF_MS;
}

/** 孤儿资源「宽限结束、允许删除」的绝对时间；无法推算时返回 null */
export function computeOrphanGraceExpiresAt(row: {
  firstReferencedAt: Date | null;
  dereferencedAt: Date | null;
  createdAt: Date;
}): Date | null {
  if (row.firstReferencedAt == null) {
    return new Date(row.createdAt.getTime() + NEVER_REF_MS);
  }
  if (row.dereferencedAt == null) {
    return null;
  }
  return new Date(row.dereferencedAt.getTime() + AFTER_DEREF_MS);
}

function orphanCondition() {
  return notExists(
    dbGlobal.select({ x: sql`1` }).from(mediaRefs).where(eq(mediaRefs.assetId, mediaAssets.id)),
  );
}

function deletableTimeCondition(now: number) {
  const neverRefCutoff = new Date(now - NEVER_REF_MS);
  const afterDerefCutoff = new Date(now - AFTER_DEREF_MS);
  return or(
    and(isNull(mediaAssets.firstReferencedAt), lte(mediaAssets.createdAt, neverRefCutoff)),
    and(
      isNotNull(mediaAssets.firstReferencedAt),
      isNotNull(mediaAssets.dereferencedAt),
      lte(mediaAssets.dereferencedAt, afterDerefCutoff),
    ),
  );
}

export async function insertMediaAssetRow(params: {
  userId: number;
  storageKey: string;
  mime: string;
  sizeBytes: number;
  sha256?: string | null;
  variantsJson?: string | null;
}): Promise<number> {
  const id = await nextIntegerId(mediaAssets, mediaAssets.id);
  await dbGlobal.insert(mediaAssets).values({
    id,
    userId: params.userId,
    storageKey: params.storageKey,
    mime: params.mime,
    sizeBytes: params.sizeBytes,
    sha256: params.sha256 ?? null,
    variantsJson: params.variantsJson ?? null,
  });
  return id;
}

export async function reconcileAssetTimestampsAfterRefChange(assetIds: number[]): Promise<void> {
  const unique = [...new Set(assetIds)];
  for (const id of unique) {
    const [{ c }] = await dbGlobal
      .select({ c: count() })
      .from(mediaRefs)
      .where(eq(mediaRefs.assetId, id));

    if (c > 0) {
      const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
      if (!row) {
        continue;
      }
      await dbGlobal
        .update(mediaAssets)
        .set({
          firstReferencedAt: row.firstReferencedAt ?? new Date(),
          dereferencedAt: null,
        })
        .where(eq(mediaAssets.id, id));
      continue;
    }

    const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
    if (!row) {
      continue;
    }
    if (row.firstReferencedAt == null) {
      continue;
    }
    if (row.dereferencedAt != null) {
      continue;
    }
    await dbGlobal
      .update(mediaAssets)
      .set({ dereferencedAt: new Date() })
      .where(eq(mediaAssets.id, id));
  }
}

export async function syncPostMediaRefs(
  userId: number,
  postId: number,
  bodyMarkdown: string,
  coverUrl: string | null,
): Promise<void> {
  const beforeRows = await dbGlobal
    .select({ assetId: mediaRefs.assetId })
    .from(mediaRefs)
    .where(eq(mediaRefs.postId, postId));
  const beforeIds = beforeRows.map((r) => r.assetId);

  await dbGlobal.delete(mediaRefs).where(eq(mediaRefs.postId, postId));

  const urls = mergePostMediaUrls(bodyMarkdown, coverUrl);
  const keys = [...new Set(urls.map((u) => publicAssetUrlToStorageKey(u)).filter((k): k is string => k != null))];

  let afterIds: number[] = [];
  if (keys.length > 0) {
    const assetRows = await dbGlobal
      .select({ id: mediaAssets.id })
      .from(mediaAssets)
      .where(and(eq(mediaAssets.userId, userId), inArray(mediaAssets.storageKey, keys)));
    afterIds = assetRows.map((r) => r.id);
    if (afterIds.length > 0) {
      await dbGlobal
        .insert(mediaRefs)
        .values(afterIds.map((assetId) => ({ postId, assetId })))
        .onConflictDoNothing();
    }
  }

  await reconcileAssetTimestampsAfterRefChange([...new Set([...beforeIds, ...afterIds])]);
}

export async function listOrphanCandidatesForUser(
  userId: number,
  filter: "all" | "deletable" | "cooling",
  page: number,
  pageSize: number,
): Promise<{
  items: Array<{
    id: number;
    storageKey: string;
    publicUrl: string;
    sizeBytes: number;
    createdAt: Date;
    firstReferencedAt: Date | null;
    dereferencedAt: Date | null;
    graceExpiresAt: Date | null;
    state: "deletable" | "cooling";
  }>;
  total: number;
}> {
  const now = Date.now();
  const base = and(eq(mediaAssets.userId, userId), orphanCondition());

  let whereClause =
    filter === "all"
      ? base
      : filter === "deletable"
        ? and(base, deletableTimeCondition(now))
        : and(base, not(deletableTimeCondition(now)));

  const [{ total: totalRaw }] = await dbGlobal.select({ total: count() }).from(mediaAssets).where(whereClause);

  const offset = Math.max(0, (page - 1) * pageSize);
  const rows = await dbGlobal
    .select({
      id: mediaAssets.id,
      storageKey: mediaAssets.storageKey,
      sizeBytes: mediaAssets.sizeBytes,
      createdAt: mediaAssets.createdAt,
      firstReferencedAt: mediaAssets.firstReferencedAt,
      dereferencedAt: mediaAssets.dereferencedAt,
    })
    .from(mediaAssets)
    .where(whereClause)
    .orderBy(desc(mediaAssets.createdAt), desc(mediaAssets.id))
    .limit(pageSize)
    .offset(offset);

  const items = rows.map((row) => {
    const state: "deletable" | "cooling" = isAssetDeletable(row) ? "deletable" : "cooling";
    return {
      id: row.id,
      storageKey: row.storageKey,
      publicUrl: `${POST_MEDIA_PUBLIC_PREFIX}${row.storageKey}`,
      sizeBytes: row.sizeBytes,
      createdAt: row.createdAt,
      firstReferencedAt: row.firstReferencedAt,
      dereferencedAt: row.dereferencedAt,
      graceExpiresAt: computeOrphanGraceExpiresAt(row),
      state,
    };
  });

  return { items, total: totalRaw };
}

async function assertAssetDeletableOrThrow(row: typeof mediaAssets.$inferSelect): Promise<void> {
  const [{ c }] = await dbGlobal
    .select({ c: count() })
    .from(mediaRefs)
    .where(eq(mediaRefs.assetId, row.id));
  if (c > 0) {
    throw createError({ statusCode: 400, statusMessage: "资源仍被文章引用，无法删除" });
  }
  if (!isAssetDeletable(row)) {
    throw createError({ statusCode: 400, statusMessage: "资源尚在宽限期，暂不可删除" });
  }
}

export async function deleteMediaAssetsForUser(userId: number, ids: number[]): Promise<number> {
  if (ids.length === 0) {
    return 0;
  }

  for (const id of ids) {
    const [row] = await dbGlobal.select().from(mediaAssets).where(eq(mediaAssets.id, id)).limit(1);
    if (!row || row.userId !== userId) {
      throw createError({ statusCode: 400, statusMessage: "资源不存在或不属于当前用户" });
    }
    await assertAssetDeletableOrThrow(row);
    await unlinkMediaFiles(row.storageKey, row.variantsJson);
    await dbGlobal.delete(mediaAssets).where(eq(mediaAssets.id, id));
  }

  return ids.length;
}

export async function purgeAllDeletableOrphansGlobally(limit: number): Promise<number> {
  const now = Date.now();
  const whereClause = and(orphanCondition(), deletableTimeCondition(now));

  const candidates = await dbGlobal
    .select()
    .from(mediaAssets)
    .where(whereClause)
    .orderBy(mediaAssets.id)
    .limit(limit);

  let deleted = 0;
  for (const row of candidates) {
    const [{ c }] = await dbGlobal
      .select({ c: count() })
      .from(mediaRefs)
      .where(eq(mediaRefs.assetId, row.id));
    if (c > 0) {
      continue;
    }
    if (!isAssetDeletable(row)) {
      continue;
    }
    await unlinkMediaFiles(row.storageKey, row.variantsJson);
    await dbGlobal.delete(mediaAssets).where(eq(mediaAssets.id, row.id));
    deleted += 1;
  }

  return deleted;
}