// tslint:disable max-classes-per-file interface-name
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Subject } from 'rxjs/Subject';

import { cloneDeep } from 'lodash';
import { clone } from 'lodash';
import { map } from 'lodash';
import { union } from 'lodash';
import { isFunction } from 'lodash';
import { isEmpty } from 'lodash';
import { isUndefined } from 'lodash';

import { ArrayEmitter } from './array-emitter.js';
import { Chain } from './chain';
import { Database, Model, Query as IQuery, QueryFunction, QueryList, Resource, SocketFactory } from './types';
import { convertToResolvedSubject, Deferred } from './utils';

export class Query<T> extends ArrayEmitter<T> implements IQuery<T> {
  public $refresh: (force?: boolean) => Promise<Query<T>>;
  public $promise: Promise<Query<T>>;
  public $subject: BehaviorSubject<Query<T>>;
  public $resolvedSubject: Subject<Query<T>>;
  public $resolved: boolean;
  public $Model: any;
  public $serverResults?: Query<T>;
  public $skip?: number;
  public $hasNext: boolean;
  public $hasPrev: boolean;

  public extend: (obj: any, noSanitize?: boolean, retServer?: boolean) => Promise<Query<T>>;
  public replace: (qry: any, retServer?: boolean) => Promise<Query<T>>;
  public get: (...args: any[]) => any;
  public next: (num?: number) => Promise<Query<T>>;
  public prev: (num?: number) => Promise<Query<T>>;
  public chain: (Model: Resource<Model> | QueryFunction, qryFn?: QueryFunction) => IQuery<Model>;
  public transform: (tmpResults: any[]) => Promise<any[]> | any[];
  public currentLimit: number;
  public currentSkip: number;
  public loading: boolean;
  public hasNext: boolean;
  public hasPrev: boolean;
}

export class LocalQuery<T> extends Query<T> {}

export class ServerQuery<T> extends Query<T> {
  public $newData?: (qryId: string, response: any, force?: boolean) => void;
}

function normalizeQuery(qry: any) {
  if (!qry) {
    return;
  }

  if (qry._q) {
    return qry._q;
  } else if (qry.find) {
    return qry;
  } else {
    return {find: qry};
  }
}

function extendQuery(qry1: any, qry2: any) {
  // Calc the new query that we want
  const _qry = cloneDeep(qry1);
  ['limit', 'skip', 'sort'].forEach(prop => {
    if (qry2[prop]) {
      _qry[prop] = qry2[prop];
    }
  });

  if (!isEmpty(qry2.find)) {
    // Want to or together - but is the toplevel already an or? (and only an or)
    let existingOr = false;
    if (_qry.find.$or) {
      let valid = true;
      for (const key in _qry.find) {
        if (key !== '$or') {
          valid = false;
          break;
        }
      }
      existingOr = valid;
    }

    if (existingOr) {
      _qry.find = clone(_qry.find);
    } else {
      _qry.find = {$or: [_qry.find]};
    }

    _qry.find.$or.push(qry2.find);
  }

  return _qry;
}

export function createQueryFactory(socket: SocketFactory) {

  function QueryFactory(url: string, rootKey: string, rootKeyPlural: string, db?: Database): QueryList {
    const sock = socket(url, rootKey, rootKeyPlural);

    // Object holding queries (keys are the query ids, values are arrays of arrays)
    const _localQueries: Array<LocalQuery<Model>> = [];

    /**
     * Local Query List
     * @param {[type]} qry      [description]
     * @param {[type]} limit    [description]
     * @param {[type]} Resource [description]
     * @param {[type]} toRes    [description]
     *
     * Strategy - we run the query on the server. However if we can deal with it locally (via
     * nedb) then do so. If the query at any time becomes more complicated we just fall through
     * to the server version
     */
    const LocalQueryList: QueryList = (qry: any,
                                       limit: number,
                                       Resource: Resource<Model>,
                                       toRes: (id: string) => Model): LocalQuery<Model> => {
      // Allow qry to be a promise, and we return the raw (non _q bit)
      qry = Promise.resolve(qry).then(normalizeQuery).then(_qry => {
        if (limit) {
          _qry.limit = limit;
        }
        return _qry;
      });

      // Generate the ServerQuery. We do this so we have something to fall back on
      // and also so that we will (or should!) get notified of changes from the server if
      // someone else creates or removes something that should go in these results
      const serverResults = ServerQueryList(qry, limit, Resource);

      const results = new LocalQuery<Model>();
      _localQueries.push(results);
      let currentLimit = 0;
      let currentSkip = 0;
      let lastBatchSize = 0;
      let fallback = false;

      results.loading = true;

      // When the server results are updated we want to check paging options and apply
      // them to our results
      serverResults.$emitter.on('update', syncFromServer);

      function syncFromServer() {
        results.hasNext = serverResults.hasNext;
        results.hasPrev = serverResults.hasPrev;

        // If we are falling back then set up and copy our letious properties across
        if (fallback) {
          results.$hasNext = false;
          results.$hasPrev = false;
          results.length = 0;
          serverResults.forEach(res => {
            results.push(res);
          });

          currentLimit = results.length;
          currentSkip = results.$skip;
          lastBatchSize = lastBatchSize || results.length;
        }
      }

      function get() {
        return Resource.get.apply(Resource, arguments);
      }

      function chain(Model: Resource<Model> | QueryFunction, qryFn?: QueryFunction) {
        return Chain(results, Model, qryFn);
      }

      function query(_qry: any) {

        // Store off the qry making sure its a promise
        qry = Promise.resolve(_qry);

        fallback = !db.qryIsSimple(_qry);

        // If we are fallingback then just resolve with our results. The server should
        // do the rest.
        if (fallback) {
          // We want to return the server's promise here so that people will be notified
          // when the results are actually loaded
          let prom;
          if (!serverResults.$resolved) {
            prom = serverResults.$promise.then(() => {
              return results;
            });
          } else {
            prom = Promise.resolve(results);
          }

          return prom;
        }

        return db.query(_qry).then((ids: string[]) => {

          // We can set the hasNext and hasPrev values to true here if we know there
          // are some. However only the server has the definitive ability to say
          // there arent any
          results.$hasNext = false;
          results.$hasPrev = false;
          if (limit && ids.length > limit) {
            // We have more results to fetch
            results.hasNext = true;
            results.$hasNext = true;

            // Trim the results down to size
            ids.length -= 1;
          }

          const skip = _qry.skip;

          if (skip) {
            results.hasPrev = true;
            results.$hasPrev = true;
          }

          // Calculate paging options
          currentLimit = ids.length;
          currentSkip = skip || 0;
          lastBatchSize = lastBatchSize || ids.length;

          // Go to resource types
          const tmpResults = ids.map(toRes);

          // Do we need to do a transform?
          let rprom;
          if (isFunction(results.transform)) {
            rprom = Promise.resolve(results.transform(tmpResults));
          } else {
            rprom = Promise.resolve(tmpResults);
          }

          return rprom.then(transformed => {
            // Put the resources into the list
            const old = results.slice();
            results.length = 0;
            transformed.forEach((res: Model) => {
              results.push(res);
            });

            results.$emitter.emit('update', results, old);

            return results;
          });
        });

      }

      function refreshQuery(forceServer?: boolean): Promise<LocalQuery<Model>> {
        // Perform our query
        let prom = qry.then(query).then((res: any[]) => {
          // If we don't have any results then maybe wait for the server to return
          if ((res.length === 0 && !serverResults.$resolved)) {
            return serverResults.$promise.then(() => {
              return refreshQuery();
            });
          } else {
            return res;
          }
        });

        if (forceServer) {
          prom = serverResults.$refresh(true);
        }

        return prom.then((res: any) => {
          results.loading = false;
          return res;
        });
      }

      function extendResults(obj: any, noSanitize?: boolean, retServer?: boolean) {

        // Sanitize the object
        if (!noSanitize) {
          if (obj._q) {
            obj = obj._q;
          } else {
            obj = {find: obj};
          }
        }

        return qry.then((resolved: any) => {
          const _qry = extendQuery(resolved, obj);
          return replace(_qry, retServer);
        });
      }

      function replace(_qry: any, retServer?: boolean) {
        // Sync down to the serverquery
        const serverProm = serverResults.replace(_qry);

        // Do the query but replace the existing query
        const localProm = Promise.resolve(_qry).then(normalizeQuery).then(normQry => {

          // We allow a query to resolve to something falsy - in which case we just
          // drop it
          if (!normQry) {
            return;
          }

          return qry.then((oldqry: any) => {
            if (JSON.stringify(oldqry) !== JSON.stringify(normQry)) {
              // query is different - continue

              return query(normQry);
            }
          });
        });

        return retServer ? serverProm : localProm;
      }

      function next(num?: number) {
        let promise;
        let extendSize;
        if (results.hasNext) {
          lastBatchSize = extendSize = num || lastBatchSize;
          const extendObj = {
            limit: currentLimit + extendSize,
          };
          promise = extendResults(extendObj, true, !results.$hasNext);
        } else {
          const deferred = new Deferred();
          deferred.resolve();
          promise = deferred.promise;
        }

        return promise;
      }

      function prev(num?: number) {
        let promise;
        let extendSize;
        if (results.hasPrev) {
          lastBatchSize = extendSize = num || lastBatchSize;
          const extendObj = {
            limit: currentLimit + extendSize,
            skip: Math.max(currentSkip - extendSize, 0),
          };
          promise = extendResults(extendObj, true, !results.$hasPrev);
        } else {
          const deferred = new Deferred();
          deferred.resolve();
          promise = deferred.promise;
        }

        return promise;
      }

      results.$refresh = refreshQuery;
      results.extend = extendResults;
      results.replace = replace;
      results.get = get;
      results.next = next;
      results.prev = prev;
      results.$promise = refreshQuery();
      results.$resolvedSubject = convertToResolvedSubject(results.$subject, results.$promise);
      results.chain = chain;
      results.$Model = Resource;
      results.$serverResults = serverResults;

      // Put currentSkip and currentLimit onto the results
      Object.defineProperty(results, 'currentLimit', {
        enumerable: true,
        get: () => {
          return currentLimit;
        },
      });
      Object.defineProperty(results, 'currentSkip', {
        enumerable: true,
        get: () => {
          return currentSkip;
        },
      });

      return results;
    };

    let refreshTimer: number;
    LocalQueryList.refresh = () => {

      // If we have a timer outstanding then just return - a refresh will happen soon.
      if (!refreshTimer) {
        refreshTimer = setTimeout(doRefresh, 100);
      }

      return refreshTimer;

      function doRefresh() {
        _localQueries.forEach(res => {
          res.$refresh();
        });
        refreshTimer = null;
      }
    };

    /**
     * Server query list. The server makes sure we keep in sync
     * @param {[type]} qry      [description]
     * @param {[type]} limit    [description]
     * @param {[type]} Resource [description]
     */
    function ServerQueryList(qry: any, limit: number, Resource: any): ServerQuery<Model> {
      // Allow qry to be a promise
      qry = Promise.resolve(qry).then(normalizeQuery).then(_qry => {
        if (limit) {
          _qry.limit = limit;
        }
        return _qry;
      });

      let emitPromise: Promise<any> = null;
      const results = new ServerQuery<Model>();
      let currentLimit = 0;
      let currentSkip = 0;
      let lastBatchSize = 0;
      let _pagingOpts: any = {};

      results.loading = true;

      function query(data: any) {
        // We only want to do one emit at a time (otherwise we could get into a bad state)
        if (isFunction(data)) {
          data = data();
        }

        // Store off the query - make sure its a promise
        qry = Promise.resolve(data);

        return qry.then((_data: any) => {
          // If we have an existing emitPromise then wait for it to resolve before we run
          let promise;
          if (emitPromise) {
            promise = emitPromise.then(() => {
              return sock.query(_data);
            });
          } else {
            emitPromise = promise = sock.query(_data);
          }

          return promise;
        });
      }

      function newData(_qryId: string, response: any, force?: boolean) {
        if (!response) {
          return;
        }

        const deferred = new Deferred();
        const ids: string[] = response.ids;
        const pagingOpts = response.pagingOpts;

        // So far we've only got the ids of the qry result - go and fetch the actual objects.
        // This mechanism saves bandwidth by only getting the object data once then listening
        // for changes to it
        //
        // If we are forcing we want to get both the old and new ids to check for any changes
        // deletions etc..
        let getIds = ids;
        if (force) {
          const oldIds = map(results, '_id');
          getIds = union(ids, oldIds);
        }

        Resource.get(getIds, force).$promise.then((ress: any[]) => {
          const ressmap: any = {};
          ress.forEach(res => {
            ressmap[res._id] = res;
          });

          // We don't allow repeated ids so just iterate over the results
          const tmpResults: any[] = [];
          ids.forEach(id => {
            tmpResults.push(ressmap[id]);
          });

          // Do we need to do a transform?
          let rprom;
          if (isFunction(results.transform)) {
            rprom = Promise.resolve(results.transform(tmpResults));
          } else {
            rprom = Promise.resolve(tmpResults);
          }

          return rprom.then(transformed => {

            results.length = 0;
            transformed.forEach((res: Model) => {
              results.push(res);
            });

            // Since we now have data in our array store off limit data
            currentLimit = tmpResults.length;
            results.$skip = currentSkip = (qry && qry.skip) ? qry.skip : 0;
            lastBatchSize = lastBatchSize || tmpResults.length;
            _pagingOpts = pagingOpts;
            results.hasNext = (pagingOpts.next != null);
            results.hasPrev = (pagingOpts.prev != null);

            // Data has come back
            results.loading = false;

            results.$emitter.emit('update', results);

            deferred.resolve(results);
          });
        });

        return deferred.promise;
      }

      function refreshQuery(force?: boolean): Promise<ServerQuery<Model>> {
        const req = query(qry);
        const promise = req.then((res: any) => {

          // If we get no response (the app could be offline) then just resolve with
          // the existing results
          if (isUndefined(res)) {
            results.loading = false;
            return results;
          }

          const _qryId = res.qryId;
          const response = res.data;

          return newData(_qryId, response, force);
        });
        return promise;
      }

      function replace(_qry: any) {
        // Do the query but replace the existing query
        return Promise.resolve(_qry).then(normalizeQuery).then(normQry => {

          // We allow a query to resolve to something falsy - in which case we just
          // drop it
          if (!normQry) {
            return;
          }

          return qry.then((oldqry: any) => {
            if (JSON.stringify(oldqry) !== JSON.stringify(normQry)) {
              // query is different - continue
              const req = query(normQry);

              const promise = req.then((res: any) => {
                // If we get no response (the app could be offline) then just resolve with
                // the existing results
                if (isUndefined(res)) {
                  results.loading = false;
                  return results;
                }

                // We do have a response. Continue
                const _qryId = res.qryId;
                const data = res.data;

                return newData(_qryId, data);
              });

              return promise;
            }
          });
        });

      }

      function extendResults(obj: any, noSanitize?: boolean) {

        // Sanitize the object
        if (!noSanitize) {
          if (obj._q) {
            obj = obj._q;
          } else {
            obj = {find: obj};
          }
        }

        return qry.then((resolved: any) => {
          const _qry = extendQuery(resolved, obj);
          return replace(_qry);
        });
      }

      function next(num: number) {
        let promise;
        let extendSize;
        if (_pagingOpts.next) {
          lastBatchSize = extendSize = num || lastBatchSize;
          const extendObj = {
            limit: currentLimit + extendSize,
          };
          promise = extendResults(extendObj, true);
        } else {
          const deferred = new Deferred();
          deferred.resolve();
          promise = deferred.promise;
        }

        return promise;
      }

      function prev(num: number) {
        let promise;
        let extendSize;
        if (_pagingOpts.prev) {
          lastBatchSize = extendSize = num || lastBatchSize;
          const extendObj = {
            limit: currentLimit + extendSize,
            skip: Math.max(currentSkip - extendSize, 0),
          };
          promise = extendResults(extendObj, true);
        } else {
          const deferred = new Deferred();
          deferred.resolve();
          promise = deferred.promise;
        }

        return promise;
      }

      function get() {
        return Resource.get.apply(Resource, arguments);
      }

      function chain(Model: any, qryFn: QueryFunction) {
        return Chain(results, Model, qryFn);
      }

      results.$newData = newData;
      results.$refresh = refreshQuery;
      results.extend = extendResults;
      results.replace = replace;
      results.get = get;
      results.next = next;
      results.prev = prev;
      results.$promise = refreshQuery().then(res => {
        results.$resolved = true;
        return res;
      });
      results.$resolvedSubject = convertToResolvedSubject(results.$subject, results.$promise);
      results.$resolved = false;
      results.chain = chain;
      results.$Model = Resource;
      results.$skip = 0;

      // Put currentSkip and currentLimit onto the results
      Object.defineProperty(results, 'currentLimit', {
        enumerable: true,
        get: () => {
          return currentLimit;
        },
      });
      Object.defineProperty(results, 'currentSkip', {
        enumerable: true,
        get: () => {
          return currentSkip;
        },
      });

      return results;
    }

    return db ? LocalQueryList : ServerQueryList;
  }

  return QueryFactory;
}