import _ from 'lodash';
import moment from 'moment';

import {
  CompletionItem,
  CompletionItemGroup,
  LanguageProvider,
  TypeaheadInput,
  TypeaheadOutput,
} from 'app/types/explore';

import { parseSelector, processLabels, RATE_RANGES } from './language_utils';
import PromqlSyntax, { FUNCTIONS } from './promql';

const DEFAULT_KEYS = ['job', 'instance'];
const EMPTY_SELECTOR = '{}';
const HISTOGRAM_SELECTOR = '{le!=""}'; // Returns all timeseries for histograms
const HISTORY_ITEM_COUNT = 5;
const HISTORY_COUNT_CUTOFF = 1000 * 60 * 60 * 24; // 24h

const wrapLabel = (label: string) => ({ label });

const setFunctionMove = (suggestion: CompletionItem): CompletionItem => {
  suggestion.move = -1;
  return suggestion;
};

export function addHistoryMetadata(item: CompletionItem, history: any[]): CompletionItem {
  const cutoffTs = Date.now() - HISTORY_COUNT_CUTOFF;
  const historyForItem = history.filter(h => h.ts > cutoffTs && h.query === item.label);
  const count = historyForItem.length;
  const recent = historyForItem[0];
  let hint = `Queried ${count} times in the last 24h.`;
  if (recent) {
    const lastQueried = moment(recent.ts).fromNow();
    hint = `${hint} Last queried ${lastQueried}.`;
  }
  return {
    ...item,
    documentation: hint,
  };
}

export default class PromQlLanguageProvider extends LanguageProvider {
  histogramMetrics?: string[];
  labelKeys?: { [index: string]: string[] }; // metric -> [labelKey,...]
  labelValues?: { [index: string]: { [index: string]: string[] } }; // metric -> labelKey -> [labelValue,...]
  metrics?: string[];
  started: boolean;

  constructor(datasource: any, initialValues?: any) {
    super();

    this.datasource = datasource;
    this.histogramMetrics = [];
    this.labelKeys = {};
    this.labelValues = {};
    this.metrics = [];
    this.started = false;

    Object.assign(this, initialValues);
  }
  // Strip syntax chars
  cleanText = s => s.replace(/[{}[\]="(),!~+\-*/^%]/g, '').trim();

  getSyntax() {
    return PromqlSyntax;
  }

  request = url => {
    return this.datasource.metadataRequest(url);
  };

  start = () => {
    if (!this.started) {
      this.started = true;
      return Promise.all([this.fetchMetricNames(), this.fetchHistogramMetrics()]);
    }
    return Promise.resolve([]);
  };

  // Keep this DOM-free for testing
  provideCompletionItems({ prefix, wrapperClasses, text }: TypeaheadInput, context?: any): TypeaheadOutput {
    // Syntax spans have 3 classes by default. More indicate a recognized token
    const tokenRecognized = wrapperClasses.length > 3;
    // Determine candidates by CSS context
    if (_.includes(wrapperClasses, 'context-range')) {
      // Suggestions for metric[|]
      return this.getRangeCompletionItems();
    } else if (_.includes(wrapperClasses, 'context-labels')) {
      // Suggestions for metric{|} and metric{foo=|}, as well as metric-independent label queries like {|}
      return this.getLabelCompletionItems.apply(this, arguments);
    } else if (_.includes(wrapperClasses, 'context-aggregation')) {
      return this.getAggregationCompletionItems.apply(this, arguments);
    } else if (
      // Show default suggestions in a couple of scenarios
      (prefix && !tokenRecognized) || // Non-empty prefix, but not inside known token
      (prefix === '' && !text.match(/^[\]})\s]+$/)) || // Empty prefix, but not following a closing brace
      text.match(/[+\-*/^%]/) // Anything after binary operator
    ) {
      return this.getEmptyCompletionItems(context || {});
    }

    return {
      suggestions: [],
    };
  }

  getEmptyCompletionItems(context: any): TypeaheadOutput {
    const { history } = context;
    const { metrics } = this;
    const suggestions: CompletionItemGroup[] = [];

    if (history && history.length > 0) {
      const historyItems = _.chain(history)
        .uniqBy('query')
        .take(HISTORY_ITEM_COUNT)
        .map(h => h.query)
        .map(wrapLabel)
        .map(item => addHistoryMetadata(item, history))
        .value();

      suggestions.push({
        prefixMatch: true,
        skipSort: true,
        label: 'History',
        items: historyItems,
      });
    }

    suggestions.push({
      prefixMatch: true,
      label: 'Functions',
      items: FUNCTIONS.map(setFunctionMove),
    });

    if (metrics) {
      suggestions.push({
        label: 'Metrics',
        items: metrics.map(wrapLabel),
      });
    }
    return { suggestions };
  }

  getRangeCompletionItems(): TypeaheadOutput {
    return {
      context: 'context-range',
      suggestions: [
        {
          label: 'Range vector',
          items: [...RATE_RANGES].map(wrapLabel),
        },
      ],
    };
  }

  getAggregationCompletionItems({ value }: TypeaheadInput): TypeaheadOutput {
    let refresher: Promise<any> = null;
    const suggestions: CompletionItemGroup[] = [];

    // Stitch all query lines together to support multi-line queries
    let queryOffset;
    const queryText = value.document.getBlocks().reduce((text, block) => {
      const blockText = block.getText();
      if (value.anchorBlock.key === block.key) {
        // Newline characters are not accounted for but this is irrelevant
        // for the purpose of extracting the selector string
        queryOffset = value.anchorOffset + text.length;
      }
      text += blockText;
      return text;
    }, '');

    const leftSide = queryText.slice(0, queryOffset);
    const openParensAggregationIndex = leftSide.lastIndexOf('(');
    const openParensSelectorIndex = leftSide.slice(0, openParensAggregationIndex).lastIndexOf('(');
    const closeParensSelectorIndex = leftSide.slice(openParensSelectorIndex).indexOf(')') + openParensSelectorIndex;

    let selectorString = leftSide.slice(openParensSelectorIndex + 1, closeParensSelectorIndex);

    // Range vector syntax not accounted for by subsequent parse so discard it if present
    selectorString = selectorString.replace(/\[[^\]]+\]$/, '');

    const selector = parseSelector(selectorString, selectorString.length - 2).selector;

    const labelKeys = this.labelKeys[selector];
    if (labelKeys) {
      suggestions.push({ label: 'Labels', items: labelKeys.map(wrapLabel) });
    } else {
      refresher = this.fetchSeriesLabels(selector);
    }

    return {
      refresher,
      suggestions,
      context: 'context-aggregation',
    };
  }

  getLabelCompletionItems({ text, wrapperClasses, labelKey, value }: TypeaheadInput): TypeaheadOutput {
    let context: string;
    let refresher: Promise<any> = null;
    const suggestions: CompletionItemGroup[] = [];
    const line = value.anchorBlock.getText();
    const cursorOffset: number = value.anchorOffset;

    // Get normalized selector
    let selector;
    let parsedSelector;
    try {
      parsedSelector = parseSelector(line, cursorOffset);
      selector = parsedSelector.selector;
    } catch {
      selector = EMPTY_SELECTOR;
    }
    const containsMetric = selector.indexOf('__name__=') > -1;
    const existingKeys = parsedSelector ? parsedSelector.labelKeys : [];

    if ((text && text.match(/^!?=~?/)) || _.includes(wrapperClasses, 'attr-value')) {
      // Label values
      if (labelKey && this.labelValues[selector] && this.labelValues[selector][labelKey]) {
        const labelValues = this.labelValues[selector][labelKey];
        context = 'context-label-values';
        suggestions.push({
          label: `Label values for "${labelKey}"`,
          items: labelValues.map(wrapLabel),
        });
      }
    } else {
      // Label keys
      const labelKeys = this.labelKeys[selector] || (containsMetric ? null : DEFAULT_KEYS);
      if (labelKeys) {
        const possibleKeys = _.difference(labelKeys, existingKeys);
        if (possibleKeys.length > 0) {
          context = 'context-labels';
          suggestions.push({ label: `Labels`, items: possibleKeys.map(wrapLabel) });
        }
      }
    }

    // Query labels for selector
    if (selector && !this.labelValues[selector]) {
      if (selector === EMPTY_SELECTOR) {
        // Query label values for default labels
        refresher = Promise.all(DEFAULT_KEYS.map(key => this.fetchLabelValues(key)));
      } else {
        refresher = this.fetchSeriesLabels(selector, !containsMetric);
      }
    }

    return { context, refresher, suggestions };
  }

  async fetchMetricNames() {
    const url = '/api/v1/label/__name__/values';
    try {
      const res = await this.request(url);
      const body = await (res.data || res.json());
      this.metrics = body.data;
    } catch (error) {
      console.error(error);
    }
  }

  async fetchHistogramMetrics() {
    await this.fetchSeriesLabels(HISTOGRAM_SELECTOR, true);
    const histogramSeries = this.labelValues[HISTOGRAM_SELECTOR];
    if (histogramSeries && histogramSeries['__name__']) {
      this.histogramMetrics = histogramSeries['__name__'].slice().sort();
    }
  }

  async fetchLabelValues(key: string) {
    const url = `/api/v1/label/${key}/values`;
    try {
      const res = await this.request(url);
      const body = await (res.data || res.json());
      const exisingValues = this.labelValues[EMPTY_SELECTOR];
      const values = {
        ...exisingValues,
        [key]: body.data,
      };
      this.labelValues = {
        ...this.labelValues,
        [EMPTY_SELECTOR]: values,
      };
    } catch (e) {
      console.error(e);
    }
  }

  async fetchSeriesLabels(name: string, withName?: boolean) {
    const url = `/api/v1/series?match[]=${name}`;
    try {
      const res = await this.request(url);
      const body = await (res.data || res.json());
      const { keys, values } = processLabels(body.data, withName);
      this.labelKeys = {
        ...this.labelKeys,
        [name]: keys,
      };
      this.labelValues = {
        ...this.labelValues,
        [name]: values,
      };
    } catch (e) {
      console.error(e);
    }
  }
}