"use server";
import { revalidatePath } from "next/cache";
import { rawDb, uniqueSlug } from "@/lib/db/client";
import { redirect } from "next/navigation";

export async function createCollection(name: string, description?: string): Promise<{ id: number; slug: string } | null> {
  const trimmed = name.trim();
  if (!trimmed) return null;
  const slug = uniqueSlug(rawDb, "collections", trimmed);
  // New collections land at the end of the manual order. Wrap the read +
  // insert in a tx so concurrent creates don't both pick the same
  // position.
  const tx = rawDb.transaction(() => {
    const max = rawDb.prepare(`SELECT COALESCE(MAX(position), -1) AS m FROM collections`).get() as { m: number };
    const r = rawDb.prepare(`
      INSERT INTO collections (name, slug, description, position) VALUES (?, ?, ?, ?) RETURNING id
    `).get(trimmed, slug, description?.trim() || null, max.m + 1) as { id: number };
    return r.id;
  });
  const id = tx();
  revalidatePath("/collection");
  return { id, slug };
}

export async function createCollectionAction(formData: FormData) {
  const name = String(formData.get("name") ?? "");
  const description = String(formData.get("description") ?? "");
  const created = await createCollection(name, description);
  if (created) redirect(`/collection/${created.slug}`);
}

export async function addImageToCollection(collectionId: number, imageId: number) {
  // Wrap the read-then-insert in a transaction so concurrent calls
  // can't both compute the same MAX(position) and produce duplicate
  // ordering values.
  const tx = rawDb.transaction(() => {
    const max = rawDb.prepare(`SELECT COALESCE(MAX(position), -1) AS m FROM collection_images WHERE collection_id = ?`).get(collectionId) as { m: number };
    rawDb.prepare(`
      INSERT OR IGNORE INTO collection_images (collection_id, image_id, position) VALUES (?, ?, ?)
    `).run(collectionId, imageId, max.m + 1);
    rawDb.prepare(`UPDATE collections SET last_used_at = (unixepoch() * 1000) WHERE id = ?`).run(collectionId);
  });
  tx();
  revalidatePath(`/collection`);
  revalidatePath(`/image/${imageId}`);
}

export async function removeImageFromCollection(collectionId: number, imageId: number) {
  rawDb.prepare(`DELETE FROM collection_images WHERE collection_id = ? AND image_id = ?`).run(collectionId, imageId);
  revalidatePath(`/collection`);
  revalidatePath(`/image/${imageId}`);
}

export async function deleteCollection(collectionId: number) {
  rawDb.prepare(`DELETE FROM collections WHERE id = ?`).run(collectionId);
  revalidatePath("/collection");
  redirect("/collection");
}

/**
 * Reorder a single image within a collection. The drag-and-drop UI passes
 * the image being moved and the image it should now sit before (or null
 * to drop at the end). We pull the current ordered list, splice the
 * moved image into its new index, then rewrite every position so the
 * sequence is dense (0..N-1) regardless of any gaps the previous
 * ordering may have had.
 */
export async function reorderCollectionImage(
  collectionId: number,
  movedImageId: number,
  beforeImageId: number | null,
): Promise<void> {
  const rows = rawDb.prepare(`
    SELECT image_id FROM collection_images
    WHERE collection_id = ?
    ORDER BY position ASC, image_id ASC
  `).all(collectionId) as Array<{ image_id: number }>;
  const ids = rows.map((r) => r.image_id);
  const fromIdx = ids.indexOf(movedImageId);
  if (fromIdx === -1) return;
  ids.splice(fromIdx, 1);
  let toIdx = beforeImageId == null ? ids.length : ids.indexOf(beforeImageId);
  if (toIdx === -1) toIdx = ids.length;
  ids.splice(toIdx, 0, movedImageId);

  const tx = rawDb.transaction(() => {
    const update = rawDb.prepare(`
      UPDATE collection_images SET position = ? WHERE collection_id = ? AND image_id = ?
    `);
    for (let i = 0; i < ids.length; i++) {
      update.run(i, collectionId, ids[i]);
    }
  });
  tx();

  const slugRow = rawDb.prepare(`SELECT slug FROM collections WHERE id = ?`).get(collectionId) as { slug: string } | undefined;
  revalidatePath("/collection");
  if (slugRow) revalidatePath(`/collection/${slugRow.slug}`);
}

/**
 * Reorder a collection in the manual list on /collection. Pulls the
 * current ordered ids, splices the moved one to its new index, then
 * rewrites every position so the sequence is dense (0..N-1).
 */
export async function reorderCollection(
  movedId: number,
  beforeId: number | null,
): Promise<void> {
  const rows = rawDb.prepare(`
    SELECT id FROM collections ORDER BY position ASC, id ASC
  `).all() as Array<{ id: number }>;
  const ids = rows.map((r) => r.id);
  const fromIdx = ids.indexOf(movedId);
  if (fromIdx === -1) return;
  ids.splice(fromIdx, 1);
  let toIdx = beforeId == null ? ids.length : ids.indexOf(beforeId);
  if (toIdx === -1) toIdx = ids.length;
  ids.splice(toIdx, 0, movedId);

  const tx = rawDb.transaction(() => {
    const update = rawDb.prepare(`UPDATE collections SET position = ? WHERE id = ?`);
    for (let i = 0; i < ids.length; i++) update.run(i, ids[i]);
  });
  tx();
  revalidatePath("/collection");
}

/** Rename a collection. Returns the new slug for client-side redirect.
 *  Wraps the slug-uniqueness check + UPDATE in a transaction so two
 *  concurrent renames can't both compute the same slug and crash on
 *  the UNIQUE constraint (or worse, race past it). */
export async function renameCollection(id: number, name: string): Promise<{ slug: string; name: string } | null> {
  const trimmed = name.trim();
  if (!trimmed) return null;
  const tx = rawDb.transaction(() => {
    const current = rawDb.prepare(`SELECT name, slug FROM collections WHERE id = ?`).get(id) as
      | { name: string; slug: string }
      | undefined;
    if (!current) return null;
    if (current.name === trimmed) {
      return { slug: current.slug, name: trimmed };
    }
    const slug = uniqueSlug(rawDb, "collections", trimmed, id);
    rawDb.prepare(`UPDATE collections SET name = ?, slug = ? WHERE id = ?`).run(trimmed, slug, id);
    return { slug, name: trimmed };
  });
  const result = tx() as { slug: string; name: string } | null;
  if (!result) return null;
  revalidatePath("/collection");
  revalidatePath(`/collection/${result.slug}`);
  return result;
}