import { useState } from 'react';
import { View, Text, TouchableOpacity, LayoutAnimation, Platform, UIManager } from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { useTranslation } from 'react-i18next';
import { useColors } from '../../lib/theme';
import type { BackendCooldownEntry } from '../../hooks/useProfileData';

if (Platform.OS === 'android' && UIManager.setLayoutAnimationEnabledExperimental) {
  UIManager.setLayoutAnimationEnabledExperimental(true);
}

const DE_STOP_WORDS = new Set([
  'der', 'die', 'das', 'den', 'dem', 'des', 'ein', 'eine', 'einer', 'einem', 'einen', 'eines',
  'und', 'oder', 'aber', 'auch', 'noch', 'nur', 'nicht', 'kein', 'keine', 'keinen',
  'ich', 'du', 'er', 'sie', 'es', 'wir', 'ihr', 'sie', 'mich', 'dich', 'sich',
  'mir', 'dir', 'uns', 'euch', 'ihm', 'ihr', 'ihnen',
  'mein', 'dein', 'sein', 'ihr', 'unser', 'euer',
  'meinen', 'deinen', 'seinen', 'ihren', 'unseren',
  'meiner', 'deiner', 'seiner', 'ihrer', 'unserer',
  'meinem', 'deinem', 'seinem', 'ihrem', 'unserem',
  'ist', 'sind', 'war', 'waren', 'bin', 'bist', 'hat', 'haben', 'hatte', 'hatten',
  'wird', 'werden', 'wurde', 'wurden', 'kann', 'muss', 'soll', 'will', 'mag',
  'bei', 'von', 'mit', 'aus', 'auf', 'in', 'an', 'im', 'am', 'zu', 'zum', 'zur',
  'als', 'wie', 'wenn', 'weil', 'dass', 'ob', 'damit', 'wann', 'wo', 'was', 'wer',
  'so', 'da', 'hier', 'dort', 'nun', 'mal', 'gerade', 'dann', 'nach', 'vor', 'seit',
  'sehr', 'mehr', 'viel', 'wieder', 'immer', 'schon', 'halt', 'einfach', 'eigentlich',
  'heute', 'jetzt', 'wieder', 'etwa',
]);

const EN_STOP_WORDS = new Set([
  'the', 'a', 'an', 'and', 'or', 'but', 'not', 'no', 'nor',
  'i', 'me', 'my', 'myself', 'we', 'our', 'you', 'your', 'he', 'she', 'it', 'they',
  'him', 'her', 'his', 'its', 'them', 'their', 'this', 'that', 'these', 'those',
  'is', 'are', 'was', 'were', 'be', 'been', 'being', 'have', 'has', 'had',
  'do', 'does', 'did', 'will', 'would', 'could', 'should', 'may', 'might', 'can',
  'of', 'in', 'to', 'for', 'on', 'at', 'by', 'with', 'from', 'as', 'into', 'about',
  'so', 'just', 'also', 'then', 'now', 'here', 'there', 'up', 'out', 'very',
  'really', 'already', 'again', 'too', 'today', 'after', 'before',
]);

const WEEKDAY_KEYS = [
  'profile.cooldown.patterns.weekday_mon',
  'profile.cooldown.patterns.weekday_tue',
  'profile.cooldown.patterns.weekday_wed',
  'profile.cooldown.patterns.weekday_thu',
  'profile.cooldown.patterns.weekday_fri',
  'profile.cooldown.patterns.weekday_sat',
  'profile.cooldown.patterns.weekday_sun',
] as const;

const MAX_BAR_HEIGHT = 48;
const MIN_BAR_HEIGHT = 2;

type TopWord = { word: string; count: number };

function buildHourBuckets(entries: BackendCooldownEntry[]): number[] {
  const buckets = Array(24).fill(0);
  for (const e of entries) {
    const h = new Date(e.startedAt).getHours();
    buckets[h]++;
  }
  return buckets;
}

function buildWeekdayBuckets(entries: BackendCooldownEntry[]): number[] {
  const buckets = Array(7).fill(0);
  for (const e of entries) {
    const jsDay = new Date(e.startedAt).getDay();
    const moFirst = jsDay === 0 ? 6 : jsDay - 1;
    buckets[moFirst]++;
  }
  return buckets;
}

function extractTopWords(entries: BackendCooldownEntry[], lang: string): TopWord[] {
  const stopWords = lang.startsWith('de') ? DE_STOP_WORDS : EN_STOP_WORDS;
  const freq: Record<string, number> = {};

  for (const e of entries) {
    if (!e.reason) continue;
    const words = e.reason
      .toLowerCase()
      .replace(/[^a-zA-ZäöüÄÖÜß\s]/g, ' ')
      .split(/\s+/);
    for (const w of words) {
      if (w.length < 3) continue;
      if (stopWords.has(w)) continue;
      freq[w] = (freq[w] ?? 0) + 1;
    }
  }

  return Object.entries(freq)
    .sort((a, b) => b[1] - a[1])
    .slice(0, 5)
    .map(([word, count]) => ({ word, count }));
}

function cancelRate(entries: BackendCooldownEntry[]): number {
  if (entries.length === 0) return 0;
  const cancelled = entries.filter((e) => e.status === 'cancelled').length;
  return Math.round((cancelled / entries.length) * 100);
}

type BarChartProps = {
  buckets: number[];
  labels: string[];
  highlightIndices?: number[];
  colors: ReturnType<typeof import('../../lib/theme').useColors>;
};

function BarChart({ buckets, labels, highlightIndices, colors }: BarChartProps) {
  const maxCount = Math.max(...buckets, 1);
  return (
    <View style={{ flexDirection: 'row', alignItems: 'flex-end', gap: 2 }}>
      {buckets.map((count, i) => {
        const isEmpty = count === 0;
        const barHeight = isEmpty
          ? MIN_BAR_HEIGHT
          : Math.max(MIN_BAR_HEIGHT, (count / maxCount) * MAX_BAR_HEIGHT);
        const isHighlight = highlightIndices?.includes(i);
        return (
          <View key={i} style={{ flex: 1, alignItems: 'center' }}>
            <View
              style={{
                width: '100%',
                height: barHeight,
                borderRadius: 3,
                backgroundColor: isEmpty
                  ? colors.border
                  : isHighlight
                  ? colors.brandOrange
                  : colors.brandOrange + 'aa',
              }}
            />
            {labels[i] !== '' ? (
              <Text
                style={{
                  marginTop: 4,
                  fontSize: 8,
                  color: colors.textMuted,
                  fontFamily: 'Nunito_400Regular',
                  textAlign: 'center',
                }}
                numberOfLines={1}
              >
                {labels[i]}
              </Text>
            ) : (
              <View style={{ height: 12 }} />
            )}
          </View>
        );
      })}
    </View>
  );
}

type SectionHeadingProps = { label: string; colors: ReturnType<typeof import('../../lib/theme').useColors> };

function SectionHeading({ label, colors }: SectionHeadingProps) {
  return (
    <Text
      style={{
        fontSize: 11,
        color: colors.textMuted,
        fontFamily: 'Nunito_700Bold',
        letterSpacing: 0.6,
        marginBottom: 10,
      }}
    >
      {label.toUpperCase()}
    </Text>
  );
}

type Props = {
  rawCooldowns: BackendCooldownEntry[] | null;
};

export function CooldownPatternAnalysis({ rawCooldowns }: Props) {
  const { t, i18n } = useTranslation();
  const colors = useColors();
  const lang = i18n.language ?? 'de';
  const [expanded, setExpanded] = useState(false);

  function toggle() {
    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut);
    setExpanded((v) => !v);
  }

  const entries = rawCooldowns ?? [];
  const hasData = entries.length > 0;

  const hourBuckets = hasData ? buildHourBuckets(entries) : Array(24).fill(0);
  const weekdayBuckets = hasData ? buildWeekdayBuckets(entries) : Array(7).fill(0);
  const topWords = hasData ? extractTopWords(entries, lang) : [];
  const pct = cancelRate(entries);

  const hourLabels: string[] = Array(24)
    .fill('')
    .map((_, h) => {
      if (h === 6) return t('profile.cooldown.patterns.hour_morning');
      if (h === 12) return t('profile.cooldown.patterns.hour_afternoon');
      if (h === 18) return t('profile.cooldown.patterns.hour_evening');
      if (h === 0) return t('profile.cooldown.patterns.hour_night');
      return '';
    });

  const weekdayLabels: string[] = WEEKDAY_KEYS.map((k) => t(k));

  const peakHour = hasData ? hourBuckets.indexOf(Math.max(...hourBuckets)) : -1;
  const peakDay = hasData ? weekdayBuckets.indexOf(Math.max(...weekdayBuckets)) : -1;

  return (
    <View style={{ marginTop: 8 }}>
      <TouchableOpacity onPress={toggle} activeOpacity={0.7}>
        <View
          style={{
            flexDirection: 'row',
            alignItems: 'center',
            justifyContent: 'space-between',
            paddingVertical: 10,
            paddingHorizontal: 2,
          }}
        >
          <Text
            style={{
              fontSize: 12,
              color: colors.textMuted,
              fontFamily: 'Nunito_600SemiBold',
            }}
          >
            {t('profile.cooldown.patterns.toggle_label')}
          </Text>
          <Ionicons
            name={expanded ? 'chevron-down' : 'chevron-forward'}
            size={14}
            color={colors.textMuted}
          />
        </View>
      </TouchableOpacity>

      {expanded ? (
        <View
          style={{
            backgroundColor: colors.card,
            borderWidth: 1,
            borderColor: colors.border,
            borderRadius: 14,
            padding: 16,
            gap: 20,
          }}
        >
          {!hasData ? (
            <Text
              style={{
                fontSize: 13,
                color: colors.textMuted,
                fontFamily: 'Nunito_400Regular',
                textAlign: 'center',
                paddingVertical: 8,
              }}
            >
              {t('profile.cooldown.patterns.not_enough')}
            </Text>
          ) : (
            <>
              <View>
                <SectionHeading
                  label={t('profile.cooldown.patterns.hour_heading')}
                  colors={colors}
                />
                <BarChart
                  buckets={hourBuckets}
                  labels={hourLabels}
                  highlightIndices={peakHour >= 0 ? [peakHour] : []}
                  colors={colors}
                />
              </View>

              <View
                style={{
                  height: 1,
                  backgroundColor: colors.border,
                }}
              />

              <View>
                <SectionHeading
                  label={t('profile.cooldown.patterns.day_heading')}
                  colors={colors}
                />
                <BarChart
                  buckets={weekdayBuckets}
                  labels={weekdayLabels}
                  highlightIndices={peakDay >= 0 ? [peakDay] : []}
                  colors={colors}
                />
              </View>

              <View
                style={{
                  height: 1,
                  backgroundColor: colors.border,
                }}
              />

              <View>
                <SectionHeading
                  label={t('profile.cooldown.patterns.reason_heading')}
                  colors={colors}
                />
                {topWords.length >= 3 ? (
                  <View style={{ flexDirection: 'row', flexWrap: 'wrap', gap: 8, marginBottom: 12 }}>
                    {topWords.map(({ word, count }) => (
                      <View
                        key={word}
                        style={{
                          flexDirection: 'row',
                          alignItems: 'center',
                          backgroundColor: colors.border,
                          borderRadius: 999,
                          paddingVertical: 5,
                          paddingHorizontal: 12,
                          gap: 6,
                        }}
                      >
                        <Text
                          style={{
                            fontSize: 12,
                            color: colors.text,
                            fontFamily: 'Nunito_600SemiBold',
                          }}
                        >
                          {word}
                        </Text>
                        <Text
                          style={{
                            fontSize: 11,
                            color: colors.textMuted,
                            fontFamily: 'Nunito_400Regular',
                          }}
                        >
                          ({count})
                        </Text>
                      </View>
                    ))}
                  </View>
                ) : (
                  <Text
                    style={{
                      fontSize: 12,
                      color: colors.textMuted,
                      fontFamily: 'Nunito_400Regular',
                      marginBottom: 12,
                    }}
                  >
                    {t('profile.cooldown.patterns.not_enough')}
                  </Text>
                )}
                <Text
                  style={{
                    fontSize: 12,
                    color: colors.textMuted,
                    fontFamily: 'Nunito_400Regular',
                  }}
                >
                  {t('profile.cooldown.patterns.cancel_rate', { pct })}
                </Text>
              </View>
            </>
          )}
        </View>
      ) : null}
    </View>
  );
}