import * as db from '../database';
import * as util from './util';
import * as crypt from './crypt';
import * as session from './session';
import * as store from './storage';
import Logger from './logger';

export const FULL_SYNC_INTERVAL = 60E3;
export const QUEUE_DEBOUNCE_TIME = 1E3;
export const PUSH_DEBOUNCE_TIME = 10E3;
export const START_PULL_DELAY = 2E3;
export const START_PUSH_DELAY = 1E3;

const WHITE_LIST = {
  [db.request.type]: true,
  [db.requestGroup.type]: true,
  [db.workspace.type]: true,
  [db.environment.type]: true,
  [db.cookieJar.type]: true
};

export const logger = new Logger();

// TODO: Move this stuff somewhere else
const NO_VERSION = '__NO_VERSION__';
const resourceGroupCache = {};

/**
 * Trigger a full sync cycle. Useful if you don't want to wait for the next
 * tick.
 */
export async function triggerSync () {
  await initSync();
  await push();
  await pull();
}

let isInitialized = false;
export async function initSync () {
  const settings = await db.settings.getOrCreate();
  if (!settings.optSyncBeta) {
    logger.debug('Not enabled');
    return;
  }

  if (isInitialized) {
    logger.debug('Already enabled');
    return;
  }

  db.onChange(changes => {
    for (const [event, doc, fromSync] of changes) {
      if (!WHITE_LIST[doc.type]) {
        continue;
      }

      if (fromSync) {
        // Change was triggered from sync, so do nothing.
        continue;
      }

      // Make sure it happens async
      process.nextTick(() => _queueChange(event, doc, fromSync));
    }
  });

  setTimeout(pull, START_PULL_DELAY);
  setTimeout(push, START_PUSH_DELAY);
  setInterval(pull, FULL_SYNC_INTERVAL);
  isInitialized = true;
  logger.debug('Initialized');
}

export async function push (resourceGroupId = null) {
  if (!session.isLoggedIn()) {
    logger.warn('Not logged in');
    return;
  }

  let dirtyResources = [];
  if (resourceGroupId) {
    dirtyResources = await store.findActiveDirtyResourcesForResourceGroup(resourceGroupId)
  } else {
    dirtyResources = await store.findActiveDirtyResources()
  }

  if (!dirtyResources.length) {
    logger.debug('No changes to push');
    return;
  }

  let responseBody;
  try {
    responseBody = await util.fetchPost('/sync/push', dirtyResources);
  } catch (e) {
    logger.error('Failed to push changes', e);
    return;
  }

  // Update all resource versions with the ones that were returned
  const {updated} = responseBody;
  for (const {id, version} of updated) {
    const resource = await store.getResourceById(id);
    await store.updateResource(resource, {version, dirty: false});
    logger.debug(`Updated ${id}`);
  }

  // Update all resource versions with the ones that were returned
  const {created} = responseBody;
  for (const {id, version} of created) {
    const resource = await store.getResourceById(id);
    await store.updateResource(resource, {version, dirty: false});
    logger.debug(`Created ${id}`);
  }

  // Update all resource versions with the ones that were returned
  const {removed} = responseBody;
  for (const {id, version} of removed) {
    const resource = await store.getResourceById(id);
    await store.updateResource(resource, {version, dirty: false});
    logger.debug(`Removed ${id}`);
  }

  // Resolve conflicts
  const {conflicts} = responseBody;
  for (const serverResource of conflicts) {
    const localResource = await store.getResourceById(serverResource.id);

    // On conflict, choose last edited one
    const serverIsNewer = serverResource.lastEdited > localResource.lastEdited;
    const winner = serverIsNewer ? serverResource : localResource;

    // Decrypt the docs from the resources. Don't fetch the local doc from the
    // app database, because it might have been deleted.
    logger.debug(`Resolved conflict for ${serverResource.id} (${serverIsNewer ? 'Server' : 'Local'})`, winner);

    // Update local resource
    // NOTE: using localResource as the base to make sure we have _id
    await store.updateResource(localResource, winner, {
      version: serverResource.version, // Act as the server resource no matter what
      dirty: !serverIsNewer // It's dirty if we chose the local doc
    });

    // Update app database (NOTE: Not silently)
    if (!winner.removed) {
      const doc = await _decryptDoc(winner.resourceGroupId, winner.encContent);
      await db.update(doc, serverIsNewer);
    }
  }
}

export async function pull (resourceGroupId = null) {
  if (!session.isLoggedIn()) {
    logger.warn('Not logged in');
    return;
  }

  const allResources = await _getOrCreateAllActiveResources(resourceGroupId);

  let blacklistedConfigs;
  if (resourceGroupId) {
    // When doing a partial sync, blacklist === (everything except syncing)
    const allConfigs = await store.allConfigs();
    blacklistedConfigs = allConfigs.filter(c => c.resourceGroupId !== resourceGroupId)
  } else {
    // When doing a full sync, blacklist === inactive
    blacklistedConfigs = await store.findInactiveConfigs(resourceGroupId);
  }

  const blacklistedResourceGroupIds = blacklistedConfigs.map(c => c.resourceGroupId);

  const resources = allResources.map(r => ({
    id: r.id,
    resourceGroupId: r.resourceGroupId,
    version: r.version,
    removed: r.removed
  }));

  const body = {resources, blacklist: blacklistedResourceGroupIds};

  logger.debug(`Diffing ${resources.length} tags`);

  let responseBody;
  try {
    responseBody = await util.fetchPost('/sync/pull', body);
  } catch (e) {
    logger.error('Failed to sync changes', e, body);
    return;
  }

  const {
    updatedResources,
    createdResources,
    idsToPush,
    idsToRemove,
  } = responseBody;

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //
  // Insert all the created docs to the DB //
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //

  await createdResources.map(async serverResource => {
    try {
      const {resourceGroupId, encContent} = serverResource;
      const doc = await _decryptDoc(resourceGroupId, encContent);

      // Update local Resource
      await store.insertResource(serverResource, {dirty: false});

      // Insert into app database (NOTE: not silently)
      await db.insert(doc, true);
    } catch (e) {
      logger.warn('Failed to decode created resource', e, serverResource);
    }
  });

  if (createdResources.length) {
    logger.debug(`Created ${createdResources.length} resources`, createdResources);
  }

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //
  // Save all the updated docs to the DB //
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //

  await updatedResources.map(async serverResource => {
    try {
      const {resourceGroupId, encContent} = serverResource;
      const doc = await _decryptDoc(resourceGroupId, encContent);

      // Update app database (NOTE: Not silently)
      await db.update(doc, true);

      // Update local resource
      const resource = await store.getResourceById(serverResource.id);
      await store.updateResource(resource, serverResource, {dirty: false});
    } catch (e) {
      logger.warn('Failed to decode updated resource', e, serverResource);
    }
  });

  if (updatedResources.length) {
    logger.debug(`Updated ${updatedResources.length} resources`, updatedResources);
  }

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //
  // Remove all the docs that need removing //
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //

  for (const id of idsToRemove) {
    const resource = await store.getResourceById(id);
    if (!resource) {
      throw new Error(`Could not find Resource to remove for ${id}`)
    }

    const doc = await _decryptDoc(resource.resourceGroupId, resource.encContent);
    if (!doc) {
      throw new Error(`Could not find doc to remove ${id}`)
    }

    // Mark resource as deleted
    await store.updateResource(resource, {dirty: false, removed: true});

    // Remove from DB (NOTE: Not silently)
    await db.remove(doc, true);
  }

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //
  // Push all the docs that need pushing //
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //

  for (const id of idsToPush) {
    const resource = await store.getResourceById(id);
    if (!resource) {
      throw new Error(`Could not find Resource to push for id ${id}`)
    }

    const doc = await _decryptDoc(resource.resourceGroupId, resource.encContent);
    if (!doc) {
      throw new Error(`Could not find doc to push ${id}`)
    }

    _queueChange(db.CHANGE_UPDATE, doc)
  }

  return updatedResources.length + createdResources.length;
}

export async function getOrCreateConfig (resourceGroupId) {
  const config = await store.getConfig(resourceGroupId);

  if (!config) {
    return await store.insertConfig({resourceGroupId});
  } else {
    return config;
  }
}

export async function createOrUpdateConfig (resourceGroupId, syncMode) {
  const config = await store.getConfig(resourceGroupId);
  const patch = {resourceGroupId, syncMode};

  if (config) {
    return await store.updateConfig(config, patch);
  } else {
    return await store.insertConfig(patch);
  }
}

export async function resetLocalData () {
  for (const r of await store.allResources()) {
    await store.removeResource(r);
  }

  for (const c of await store.allConfigs()) {
    await store.removeConfig(c);
  }
}

export async function resetRemoteData () {
  await util.fetchPost('/auth/reset');
}

// ~~~~~~~ //
// HELPERS //
// ~~~~~~~ //

let _queuedChanges = {};
let _queuedChangesTimeout = null;
let _pushChangesTimeout = null;

async function _queueChange (event, doc) {
  if (!session.isLoggedIn()) {
    logger.warn('Not logged in');
    return;
  }

  // How this works?
  // First, debounce updates to Resources because they are heavy (encryption)
  // Second, debounce pushes to the server, because they are slow (network)
  // ... Using _queuedChanges as a map so that future changes to the same doc
  //     don't trigger more than 1 update.

  // NOTE: Don't use doc.modified because that doesn't work for removal
  _queuedChanges[doc._id + event] = [event, doc, Date.now()];

  clearTimeout(_queuedChangesTimeout);
  _queuedChangesTimeout = setTimeout(async () => {

    const queuedChangesCopy = Object.assign({}, _queuedChanges);
    _queuedChanges = {};

    for (const k of Object.keys(queuedChangesCopy)) {
      const [event, doc, ts] = queuedChangesCopy[k];

      // Update the resource content and set dirty
      const resource = await getOrCreateResourceForDoc(doc);
      await store.updateResource(resource, {
        lastEdited: ts,
        lastEditedBy: session.getAccountId(),
        encContent: await _encryptDoc(resource.resourceGroupId, doc),
        removed: event === db.CHANGE_REMOVE,
        dirty: true
      });

      logger.debug(`Queue ${event} ${doc._id}`);

      // Debounce pushing of dirty resources
      clearTimeout(_pushChangesTimeout);
      _pushChangesTimeout = setTimeout(() => push(), PUSH_DEBOUNCE_TIME);
    }
  }, QUEUE_DEBOUNCE_TIME);
}

/**
 * Fetch a ResourceGroup. If it has been fetched before, lookup from memory
 *
 * @param resourceGroupId
 * @returns {*}
 */
async function _fetchResourceGroup (resourceGroupId) {
  let resourceGroup = resourceGroupCache[resourceGroupId];

  if (!resourceGroup) {
    // TODO: Handle a 404 here
    try {
      resourceGroup = resourceGroupCache[resourceGroupId] = await util.fetchGet(
        `/api/resource_groups/${resourceGroupId}`
      );
    } catch (e) {
      logger.error(`Failed to get ResourceGroup ${resourceGroupId}: ${e}`);
      throw e;
    }
  }

  return resourceGroup;
}

/**
 * Get a ResourceGroup's symmetric encryption key
 *
 * @param resourceGroupId
 * @private
 */
async function _getResourceGroupSymmetricKey (resourceGroupId) {
  const resourceGroup = await _fetchResourceGroup(resourceGroupId);
  const accountPrivateKey = await session.getPrivateKey();

  const symmetricKeyStr = crypt.decryptRSAWithJWK(
    accountPrivateKey,
    resourceGroup.encSymmetricKey
  );

  return JSON.parse(symmetricKeyStr);
}

async function _encryptDoc (resourceGroupId, doc) {
  try {
    const symmetricKey = await _getResourceGroupSymmetricKey(resourceGroupId);
    const docStr = JSON.stringify(doc);
    const message = crypt.encryptAES(symmetricKey, docStr);
    return JSON.stringify(message);
  } catch (e) {
    logger.error(`Failed to encrypt for ${resourceGroupId}: ${e}`);
    throw e;
  }
}

async function _decryptDoc (resourceGroupId, messageJSON) {
  try {
    const symmetricKey = await _getResourceGroupSymmetricKey(resourceGroupId);
    const message = JSON.parse(messageJSON);
    const decrypted = crypt.decryptAES(symmetricKey, message);
    return JSON.parse(decrypted);
  } catch (e) {
    logger.error(`Failed to decrypt from ${resourceGroupId}: ${e}`);
    throw e;
  }
}

async function _getWorkspaceForDoc (doc) {
  const ancestors = await db.withAncestors(doc);
  return ancestors.find(d => d.type === db.workspace.type);
}

async function _createResourceGroup (name = '') {
  // Generate symmetric key for ResourceGroup
  const rgSymmetricJWK = await crypt.generateAES256Key();
  const rgSymmetricJWKStr = JSON.stringify(rgSymmetricJWK);

  // Encrypt the symmetric key with Account public key
  const publicJWK = session.getPublicKey();
  const encRGSymmetricJWK = crypt.encryptRSAWithJWK(publicJWK, rgSymmetricJWKStr);

  // Create the new ResourceGroup
  let resourceGroup;
  try {
    resourceGroup = await util.fetchPost('/api/resource_groups', {
      name,
      encSymmetricKey: encRGSymmetricJWK,
    });
  } catch (e) {
    logger.error(`Failed to create ResourceGroup: ${e}`);
    throw e
  }

  // Create a config for it
  await createOrUpdateConfig(resourceGroup.id, store.SYNC_MODE_OFF);

  logger.debug(`created ResourceGroup ${resourceGroup.id}`);
  return resourceGroup;
}

async function _createResource (doc, resourceGroupId) {
  return store.insertResource({
    id: doc._id,
    resourceGroupId: resourceGroupId,
    version: NO_VERSION,
    createdBy: session.getAccountId(),
    lastEdited: doc.modified,
    lastEditedBy: session.getAccountId(),
    removed: false,
    type: doc.type,
    encContent: await _encryptDoc(resourceGroupId, doc),
    dirty: true
  });
}

async function _createResourceForDoc (doc) {
  // No resource yet, so create one
  const workspace = await _getWorkspaceForDoc(doc);

  if (!workspace) {
    throw new Error(`Could not find workspace for doc ${doc._id}`);
  }

  let workspaceResource = await store.getResourceById(workspace._id);

  if (!workspaceResource) {
    // TODO: Don't auto create a ResourceGroup
    const workspaceResourceGroup = await _createResourceGroup(workspace.name);
    workspaceResource = await _createResource(workspace, workspaceResourceGroup.id);
  }

  if (workspace === doc) {
    // If the current doc IS a Workspace, just return it
    return workspaceResource;
  } else {
    return await _createResource(doc, workspaceResource.resourceGroupId);
  }
}

export async function getOrCreateResourceForDoc (doc) {
  let resource = await store.getResourceById(doc._id);

  if (!resource) {
    resource = await _createResourceForDoc(doc);
  }

  return resource;
}

async function _getOrCreateAllActiveResources (resourceGroupId = null) {
  const activeResourceMap = {};

  let activeResources;
  if (resourceGroupId) {
    activeResources = await store.activeResourcesForResourceGroup(resourceGroupId);
  } else {
    activeResources = await store.activeResources();
  }

  for (const r of activeResources) {
    activeResourceMap[r.id] = r;
  }

  // TODO: This is REALLY slow (relatively speaking)
  for (const type of Object.keys(WHITE_LIST)) {
    for (const doc of await db.all(type)) {
      const resource = await store.getResourceById(doc._id);
      if (!resource) {
        activeResourceMap[doc._id] = await _createResourceForDoc(doc);
      }
    }
  }

  return Object.keys(activeResourceMap).map(k => activeResourceMap[k]);
}