'use strict';

import * as Q from 'q';
import { Duration, Timezone } from 'chronoshift';
import { $ } from 'plywood';
import { DataSource, DataSourceJS, RefreshRule } from '../../../common/models/index';

export interface DataSourceFiller {
  (dataSource: DataSource): Q.Promise<DataSource>;
}

export interface DataSourceManagerOptions {
  dataSources?: DataSource[];
  dataSourceStubFactory?: (name: string) => DataSource;
  druidRequester?: Requester.PlywoodRequester<any>;
  dataSourceFiller?: DataSourceFiller;
  sourceListScan?: string;
  sourceListRefreshInterval?: number;
  sourceListRefreshOnLoad?: boolean;
  log?: Function;
}

export interface DataSourceManager {
  getDataSources: () => Q.Promise<DataSource[]>;
  getQueryableDataSources: () => Q.Promise<DataSource[]>;
  getQueryableDataSource: (name: string) => Q.Promise<DataSource>;
}

export function dataSourceManagerFactory(options: DataSourceManagerOptions): DataSourceManager {
  var {
    dataSources,
    dataSourceStubFactory,
    druidRequester,
    dataSourceFiller,
    sourceListScan,
    sourceListRefreshInterval,
    sourceListRefreshOnLoad,
    log
  } = options;

  if (!sourceListScan) sourceListScan = 'auto';
  if (sourceListScan !== 'disable' && sourceListScan !== 'auto') {
    throw new Error(`sourceListScan must be disabled or auto is ('${sourceListScan}')`);
  }

  if (!dataSourceStubFactory) {
    dataSourceStubFactory = (name: string) => {
      return DataSource.fromJS({
        name,
        engine: 'druid',
        source: name,
        timeAttribute: 'time',
        refreshRule: RefreshRule.query().toJS()
      });
    };
  }

  if (!log) log = function() {};

  var myDataSources: DataSource[] = dataSources || [];

  function findDataSource(name: string): DataSource {
    for (var myDataSource of myDataSources) {
      if (myDataSource.name === name) return myDataSource;
    }
    return null;
  }

  function getQueryable(): DataSource[] {
    return myDataSources.filter((dataSource) => dataSource.isQueryable());
  }

  // Updates the correct datasource (by name) in myDataSources
  function addOrUpdateDataSource(dataSource: DataSource): void {
    var updated = false;
    myDataSources = myDataSources.map((myDataSource) => {
      if (myDataSource.name === dataSource.name) {
        updated = true;
        return dataSource;
      } else {
        return myDataSource;
      }
    });
    if (!updated) {
      myDataSources.push(dataSource);
    }
  }

  function introspectDataSource(dataSource: DataSource): Q.Promise<any> {
    return dataSourceFiller(dataSource).then((filledDataSource) => {
      addOrUpdateDataSource(filledDataSource);
    }).catch((e) => {
      log(`Failed to introspect data source: '${dataSource.name}' because ${e.message}`);
    });
  }

  function loadDruidDataSources(): Q.Promise<any> {
    if (!druidRequester) return Q(null);

    return druidRequester({
      query: { queryType: 'sourceList' } as any
    }).then((ds: string[]) => {
      if (!Array.isArray(ds)) throw new Error('invalid result from data source list');

      var unknownDataSourceNames: string[] = [];
      var nonQueryableDataSources: DataSource[] = [];
      ds.forEach((d: string) => {
        var existingDataSources = myDataSources.filter((dataSource) => {
          return dataSource.engine === 'druid' && dataSource.source === d;
        });

        if (existingDataSources.length === 0) {
          unknownDataSourceNames.push(d);
        } else {
          nonQueryableDataSources = nonQueryableDataSources.concat(existingDataSources.filter((dataSource) => {
            return !dataSource.isQueryable();
          }));
        }
      });

      nonQueryableDataSources = nonQueryableDataSources.concat(unknownDataSourceNames.map((name) => {
        var newDataSource = dataSourceStubFactory(name);
        log(`Adding Druid data source: '${name}'`);
        addOrUpdateDataSource(newDataSource);
        return newDataSource;
      }));

      // Nothing to do
      if (!nonQueryableDataSources.length) return Q(null);

      return Q.allSettled(nonQueryableDataSources.map((dataSource) => {
        return introspectDataSource(dataSource);
      }));
    }).catch((e: Error) => {
      log(`Could not get druid source list: '${e.message}'`);
    });
  }

  var initialTasks: Array<Q.Promise<any>> = [];

  myDataSources.forEach((dataSource) => {
    initialTasks.push(introspectDataSource(dataSource));
  });
  if (sourceListScan === 'auto' && druidRequester) {
    initialTasks.push(loadDruidDataSources());
  }

  var initialLoad: Q.Promise<any> = Q.allSettled(initialTasks);

  initialLoad.then(() => {
    var queryableDataSources = getQueryable();
    log(`Initial introspection complete. Got ${myDataSources.length} data sources, ${queryableDataSources.length} queryable`);
  });

  if (sourceListScan === 'auto' && druidRequester && sourceListRefreshInterval) {
    log(`Will refresh data sources every ${sourceListRefreshInterval}ms`);
    setInterval(loadDruidDataSources, sourceListRefreshInterval).unref();
  }

  // Periodically check if max time needs to be updated
  setInterval(() => {
    myDataSources.forEach((dataSource) => {
      if (dataSource.shouldQueryMaxTime()) {
        DataSource.updateMaxTime(dataSource).then((updatedDataSource) => {
          log(`Getting the latest MaxTime for '${updatedDataSource.name}'`);
          addOrUpdateDataSource(updatedDataSource);
        });
      }
    });
  }, 1000).unref();

  return {
    getDataSources: () => {
      return initialLoad.then(() => {
        if (myDataSources.length && !sourceListRefreshOnLoad) return myDataSources;

        // There are no data sources... lets try to load some:
        return loadDruidDataSources().then(() => {
          return myDataSources; // we tried
        });
      });
    },

    getQueryableDataSources: () => {
      return initialLoad.then(() => {
        var queryableDataSources = getQueryable();
        if (queryableDataSources.length && !sourceListRefreshOnLoad) return queryableDataSources;

        // There are no data sources... lets try to load some:
        return loadDruidDataSources().then(() => {
          return getQueryable(); // we tried
        });
      });
    },

    getQueryableDataSource: (name: string) => {
      return initialLoad.then(() => {
        var myDataSource = findDataSource(name);
        if (myDataSource) {
          if (myDataSource.isQueryable()) return myDataSource;

          return introspectDataSource(myDataSource).then(() => {
            var queryableDataSource = findDataSource(name);
            return (queryableDataSource && queryableDataSource.isQueryable()) ? queryableDataSource : null;
          });
        }

        // There are no data sources... lets try to load some:
        return loadDruidDataSources().then(() => {
          var queryableDataSource = findDataSource(name);
          return (queryableDataSource && queryableDataSource.isQueryable()) ? queryableDataSource : null;
        });
      });
    }
  };
}


export function dataSourceToYAML(dataSource: DataSource, withComments: boolean): string[] {
  var lines: string[] = [
    `  - name: ${dataSource.name}`,
    `    title: ${dataSource.title}`,
    `    engine: ${dataSource.engine}`,
    `    source: ${dataSource.source}`,
    ``
  ];


  if (dataSource.timeAttribute) {
    if (withComments) {
      lines.push("    # The primary time attribute of the data refers to the attribute that must always be filtered on");
      lines.push("    # This is particularly useful for Druid data sources as they must always have a time filter.");
    }
    lines.push(`    timeAttribute: ${dataSource.timeAttribute.name}`, '');
  }


  var refreshRule = dataSource.refreshRule;
  if (withComments) {
    lines.push("    # The refresh rule describes how often the data source looks for new data. Default: 'query'/PT1M (every minute)");
    lines.push("    # In this case it has to be fixed since this data source is static");
  }
  lines.push(`    refreshRule:`);
  lines.push(`      rule: ${refreshRule.rule}`);
  if (refreshRule.time) {
    lines.push(`      time: ${refreshRule.time.toISOString()}`);
  }
  if (refreshRule.refresh) {
    lines.push(`      refresh: ${refreshRule.refresh.toString()}`);
  }
  lines.push('');


  var defaultTimezone = dataSource.defaultTimezone;
  if (withComments) {
    lines.push("    # The default timezone for this dataset to operate in defaults to UTC");
  }
  if (defaultTimezone.equals(DataSource.DEFAULT_TIMEZONE)) {
    if (withComments) {
      lines.push(`    #defaultTimezone: ${DataSource.DEFAULT_TIMEZONE.toString()}`, '');
    }
  } else {
    lines.push(`    defaultTimezone: ${defaultTimezone.toString()}}`, '');
  }


  var defaultDuration = dataSource.defaultDuration;
  if (withComments) {
    lines.push("    # The default duration for the time filter (if not set P3D is used)");
  }
  if (defaultDuration.equals(DataSource.DEFAULT_DURATION)) {
    if (withComments) {
      lines.push(`    #defaultDuration: ${DataSource.DEFAULT_DURATION.toString()}`, '');
    }
  } else {
    lines.push(`    defaultDuration: ${defaultDuration.toString()}`, '');
  }

  var introspection = dataSource.introspection;
  if (withComments) {
    lines.push(
      "    # How the dataset should be introspected",
      "    # possible options are:",
      "    # * none - Do not do any introspection, take what is written in the config as the rule of law.",
      "    # * no-autofill - Introspect the datasource but do not automatically generate dimensions or measures",
      "    # * autofill-dimensions-only - Introspect the datasource, automatically generate dimensions only",
      "    # * autofill-measures-only - Introspect the datasource, automatically generate measures only",
      "    # * autofill-all - (default) Introspect the datasource, automatically generate dimensions and measures"
    );
  }
  lines.push(`    introspection: ${introspection}`, '');

  lines.push('');
  return lines;
}