import type {
  LoadedWorkspace,
  StoredWorkspace,
  WorkspaceSummary,
} from './workspaceTypes';

const DB_NAME = 'pdf-tools-workspaces';
const DB_VERSION = 1;

const WORKSPACE_STORE = 'workspaces';
const PDF_STORE = 'pdfBinaries';

interface PdfBinaryRecord {
  pdfId: string;
  name: string;
  blob: Blob;
  size: number;
  createdAt: string;
  updatedAt: string;
}

interface SaveWorkspaceInput {
  workspace: StoredWorkspace;
  pdfArrayBuffer: ArrayBuffer;
}

function requestToPromise<T>(request: IDBRequest<T>): Promise<T> {
  return new Promise((resolve, reject) => {
    request.onsuccess = () => resolve(request.result);
    request.onerror = () => reject(request.error);
  });
}

function transactionDone(transaction: IDBTransaction): Promise<void> {
  return new Promise((resolve, reject) => {
    transaction.oncomplete = () => resolve();
    transaction.onerror = () => reject(transaction.error);
    transaction.onabort = () => reject(transaction.error);
  });
}

function openWorkspaceDb(): Promise<IDBDatabase> {
  return new Promise((resolve, reject) => {
    const request = indexedDB.open(DB_NAME, DB_VERSION);

    request.onupgradeneeded = () => {
      const db = request.result;

      if (!db.objectStoreNames.contains(WORKSPACE_STORE)) {
        const workspaceStore = db.createObjectStore(WORKSPACE_STORE, {
          keyPath: 'id',
        });

        workspaceStore.createIndex('updatedAt', 'updatedAt', {
          unique: false,
        });

        workspaceStore.createIndex('pdfId', 'pdfId', {
          unique: false,
        });
      }

      if (!db.objectStoreNames.contains(PDF_STORE)) {
        db.createObjectStore(PDF_STORE, {
          keyPath: 'pdfId',
        });
      }
    };

    request.onsuccess = () => resolve(request.result);
    request.onerror = () => reject(request.error);
  });
}

export async function listWorkspaces(): Promise<WorkspaceSummary[]> {
  const db = await openWorkspaceDb();

  try {
    const tx = db.transaction(WORKSPACE_STORE, 'readonly');
    const store = tx.objectStore(WORKSPACE_STORE);

    const records = await requestToPromise<StoredWorkspace[]>(store.getAll());
    await transactionDone(tx);

    return records
      .map((workspace) => ({
        id: workspace.id,
        name: workspace.name,
        pdfId: workspace.pdfId,
        pdfName: workspace.pdfName,
        createdAt: workspace.createdAt,
        updatedAt: workspace.updatedAt,
        sourcePageCount: workspace.sourcePageCount,
        workspacePageCount: workspace.pages.length,
        historyCount: workspace.history.length,
        redoCount: workspace.redoHistory?.length ?? 0,
      }))
      .sort((a, b) => b.updatedAt.localeCompare(a.updatedAt));
  } finally {
    db.close();
  }
}

export async function saveWorkspaceToIndexedDb({
  workspace,
  pdfArrayBuffer,
}: SaveWorkspaceInput): Promise<void> {
  const db = await openWorkspaceDb();

  try {
    const now = new Date().toISOString();

    const pdfRecord: PdfBinaryRecord = {
      pdfId: workspace.pdfId,
      name: workspace.pdfName,
      blob: new Blob([pdfArrayBuffer], { type: 'application/pdf' }),
      size: pdfArrayBuffer.byteLength,
      createdAt: workspace.createdAt,
      updatedAt: now,
    };

    const tx = db.transaction([WORKSPACE_STORE, PDF_STORE], 'readwrite');

    tx.objectStore(PDF_STORE).put(pdfRecord);
    tx.objectStore(WORKSPACE_STORE).put(workspace);

    await transactionDone(tx);
  } finally {
    db.close();
  }
}

export async function loadWorkspaceFromIndexedDb(
  workspaceId: string
): Promise<LoadedWorkspace | null> {
  const db = await openWorkspaceDb();

  try {
    const tx = db.transaction([WORKSPACE_STORE, PDF_STORE], 'readonly');

    const workspace = await requestToPromise<StoredWorkspace | undefined>(
      tx.objectStore(WORKSPACE_STORE).get(workspaceId)
    );

    if (!workspace) {
      await transactionDone(tx);
      return null;
    }

    const pdfRecord = await requestToPromise<PdfBinaryRecord | undefined>(
      tx.objectStore(PDF_STORE).get(workspace.pdfId)
    );

    await transactionDone(tx);

    if (!pdfRecord) {
      throw new Error(`Missing PDF binary for workspace ${workspaceId}`);
    }

    const pdfArrayBuffer = await pdfRecord.blob.arrayBuffer();

    return {
      workspace,
      pdfArrayBuffer,
    };
  } finally {
    db.close();
  }
}

export async function deleteWorkspaceFromIndexedDb(
  workspaceId: string
): Promise<void> {
  const db = await openWorkspaceDb();

  try {
    const lookupTx = db.transaction(WORKSPACE_STORE, 'readonly');
    const workspace = await requestToPromise<StoredWorkspace | undefined>(
      lookupTx.objectStore(WORKSPACE_STORE).get(workspaceId)
    );
    await transactionDone(lookupTx);

    if (!workspace) return;

    const deleteTx = db.transaction([WORKSPACE_STORE, PDF_STORE], 'readwrite');
    deleteTx.objectStore(WORKSPACE_STORE).delete(workspaceId);
    await transactionDone(deleteTx);

    // Clean up PDF binary if no remaining workspace references it.
    const remainingWorkspaces = await listWorkspaces();

    const pdfStillUsed = remainingWorkspaces.some(
      (summary) => summary.pdfId === workspace.pdfId
    );

    if (!pdfStillUsed) {
      const cleanupDb = await openWorkspaceDb();

      try {
        const cleanupTx = cleanupDb.transaction(PDF_STORE, 'readwrite');
        cleanupTx.objectStore(PDF_STORE).delete(workspace.pdfId);
        await transactionDone(cleanupTx);
      } finally {
        cleanupDb.close();
      }
    }
  } finally {
    db.close();
  }
}