import { css } from '@emotion/css';
import { shuffle } from 'lodash';
import { PureComponent } from 'react';

import { type GrafanaTheme2, type QueryEditorHelpProps } from '@grafana/data';
import { reportInteraction } from '@grafana/runtime';
import { TextLink, type Themeable2, withTheme2 } from '@grafana/ui';

import type LokiLanguageProvider from '../LanguageProvider';
import { escapeLabelValueInExactSelector } from '../languageUtils';
import { type LokiQuery } from '../types';

const DEFAULT_EXAMPLES = ['{job="default/prometheus"}'];
const PREFERRED_LABELS = ['job', 'app', 'k8s_app'];
const EXAMPLES_LIMIT = 5;

const LOGQL_EXAMPLES = [
  {
    title: 'Log pipeline',
    expression: '{job="mysql"} |= "metrics" | logfmt | duration > 10s',
    label:
      'This query targets the MySQL job, keeps logs that contain the substring "metrics", and then parses and filters the logs further.',
  },
  {
    title: 'Count over time',
    expression: 'count_over_time({job="mysql"}[5m])',
    label: 'This query counts all the log lines within the last five minutes for the MySQL job.',
  },
  {
    title: 'Rate',
    expression: 'rate(({job="mysql"} |= "error" != "timeout")[10s])',
    label:
      'This query gets the per-second rate of all non-timeout errors within the last ten seconds for the MySQL job.',
  },
  {
    title: 'Aggregate, count, and group',
    expression: 'sum(count_over_time({job="mysql"}[5m])) by (level)',
    label: 'Get the count of logs during the last five minutes, grouping by level.',
  },
];

class UnthemedLokiCheatSheet extends PureComponent<
  QueryEditorHelpProps<LokiQuery> & Themeable2,
  { userExamples: string[] }
> {
  declare userLabelTimer: ReturnType<typeof setTimeout>;
  state = {
    userExamples: [],
  };

  componentDidMount() {
    this.scheduleUserLabelChecking();
    reportInteraction('grafana_loki_cheatsheet_opened', {});
  }

  componentWillUnmount() {
    clearTimeout(this.userLabelTimer);
  }

  scheduleUserLabelChecking() {
    this.userLabelTimer = setTimeout(this.checkUserLabels, 1000);
  }

  checkUserLabels = async () => {
    // Set example from user labels
    const provider: LokiLanguageProvider = this.props.datasource?.languageProvider;
    if (provider.started) {
      const labels = provider.getLabelKeys() || [];
      const preferredLabel = PREFERRED_LABELS.find((l) => labels.includes(l));
      if (preferredLabel) {
        const values = await provider.fetchLabelValues(preferredLabel);
        const userExamples = shuffle(values)
          .slice(0, EXAMPLES_LIMIT)
          .map((value) => `{${preferredLabel}="${escapeLabelValueInExactSelector(value)}"}`);
        this.setState({ userExamples });
      }
    } else {
      this.scheduleUserLabelChecking();
    }
  };

  renderExpression(expr: string) {
    const { onClickExample, theme } = this.props;
    const styles = getStyles(theme);
    const onClick = (query: LokiQuery) => {
      onClickExample(query);
      reportInteraction('grafana_loki_cheatsheet_example_clicked', {});
    };

    return (
      <button
        type="button"
        className={styles.cheatSheetExample}
        key={expr}
        onClick={() => onClick({ refId: 'A', expr })}
      >
        <code>{expr}</code>
      </button>
    );
  }

  render() {
    const { userExamples } = this.state;
    const { theme } = this.props;
    const hasUserExamples = userExamples.length > 0;
    const styles = getStyles(theme);

    return (
      <div>
        <h2>Loki Cheat Sheet</h2>
        <div className={styles.cheatSheetItem}>
          <div className={styles.cheatSheetItemTitle}>See your logs</div>
          Start by selecting a log stream from the Label browser, or alternatively you can write a stream selector into
          the query field.
          {hasUserExamples ? (
            <div>
              Here are some example streams from your logs:
              {userExamples.map((example) => this.renderExpression(example))}
            </div>
          ) : (
            <div>
              Here is an example of a log stream:
              {this.renderExpression(DEFAULT_EXAMPLES[0])}
            </div>
          )}
        </div>
        <div className={styles.cheatSheetItem}>
          <div className={styles.cheatSheetItemTitle}>Combine stream selectors</div>
          {this.renderExpression('{app="cassandra",namespace="prod"}')}
          Returns all log lines from streams that have both labels.
        </div>

        <div className={styles.cheatSheetItem}>
          <div className={styles.cheatSheetItemTitle}>Filtering for search terms.</div>
          {this.renderExpression('{app="cassandra"} |~ "(duration|latency)s*(=|is|of)s*[d.]+"')}
          {this.renderExpression('{app="cassandra"} |= "exact match"')}
          {this.renderExpression('{app="cassandra"} != "do not match"')}
          <TextLink href="https://grafana.com/docs/loki/latest/logql/#log-pipeline" external>
            LogQL
          </TextLink>{' '}
          supports exact and regular expression filters.
        </div>
        {LOGQL_EXAMPLES.map((item) => (
          <div className={styles.cheatSheetItem} key={item.expression}>
            <div className={styles.cheatSheetItemTitle}>{item.title}</div>
            {this.renderExpression(item.expression)}
            {item.label}
          </div>
        ))}
      </div>
    );
  }
}

export default withTheme2(UnthemedLokiCheatSheet);

const getStyles = (theme: GrafanaTheme2) => ({
  cheatSheetItem: css({
    margin: theme.spacing(3, 0),
  }),
  cheatSheetItemTitle: css({
    fontSize: theme.typography.h3.fontSize,
  }),
  cheatSheetExample: css({
    margin: theme.spacing(0.5, 0),
    // element is interactive, clear button styles
    textAlign: 'left',
    border: 'none',
    background: 'transparent',
    display: 'block',
  }),
});
