import { Panel } from './Panel';
import { getCSSColor } from '@/utils';
import type { CountryScore } from '@/services/country-instability';
import { t } from '../services/i18n';
import { h, replaceChildren, rawHtml, setTrustedHtml, trustedHtml, type TrustedHtml } from '@/utils/dom-utils';
import type { CachedRiskScores } from '@/services/cached-risk-scores';
import { toCountryScore } from '@/services/cached-risk-scores';
import { renderFollowButton } from '@/utils/follow-button';
import {
  getFollowed,
  isFollowFeatureEnabled,
  subscribe as subscribeFollowed,
} from '@/services/followed-countries';
import {
  partitionByFollowed,
  shouldRenderSectionLabels,
} from './_cii-panel-partition';

export const CII_METHODOLOGY_HREF = '/docs/methodology/cii-risk-scores';

export class CIIPanel extends Panel {
  private scores: CountryScore[] = [];
  private onShareStory?: (code: string, name: string) => void;
  private onCountryClick?: (code: string) => void;
  // Per-row FollowButton teardowns. Keyed by ISO code so we can tear
  // down each one before the row is re-rendered (refresh / renderFromCached
  // both call replaceChildren on this.content). Without this the
  // FollowButton's watchlist + entitlement subscriptions leak each
  // refresh tick — CIIPanel re-renders very frequently.
  private followButtonTeardowns = new Map<string, () => void>();
  // U6 — teardown for the watchlist subscription installed in the
  // constructor. Re-renders the current rows whenever the followed list
  // changes (anonymous: localStorage write or cross-tab `storage` event;
  // signed-in: Convex `listFollowed` snapshot). Fired on `destroy()`.
  private followedUnsubscribe: (() => void) | null = null;

  constructor() {
    super({
      id: 'cii',
      title: t('panels.cii'),
      // Two keys (#3725 review): infoTooltip ships translated in all 21 locales;
      // methodologyLink is shipped en-only as a stop-gap so the disclosure link is
      // present in every locale immediately. Translators can localize the link
      // asynchronously without holding back the transparency feature.
      infoTooltip: `${t('components.cii.infoTooltip')} ${t('components.cii.methodologyLink')}`,
      defaultRowSpan: 2,
    });
    this.showLoading(t('common.loading'));

    // U6 — re-render rows on every watchlist mutation so the pinned-to-top
    // group stays in sync. We re-render the cached scores in place rather
    // than re-fetch — the data hasn't changed, only the partition order.
    // The handler is a no-op until `this.scores` is populated by the first
    // `refresh()` / `renderFromCached()` call.
    this.followedUnsubscribe = subscribeFollowed(() => {
      this.rerenderRows();
    });
  }

  public setShareStoryHandler(handler: (code: string, name: string) => void): void {
    this.onShareStory = handler;
  }

  public setCountryClickHandler(handler: (code: string) => void): void {
    this.onCountryClick = handler;
  }

  private getLevelColor(level: CountryScore['level']): string {
    switch (level) {
      case 'critical': return getCSSColor('--semantic-critical');
      case 'high': return getCSSColor('--semantic-high');
      case 'elevated': return getCSSColor('--semantic-elevated');
      case 'normal': return getCSSColor('--semantic-normal');
      case 'low': return getCSSColor('--semantic-low');
    }
  }

  private getLevelEmoji(level: CountryScore['level']): string {
    switch (level) {
      case 'critical': return '🔴';
      case 'high': return '🟠';
      case 'elevated': return '🟡';
      case 'normal': return '🟢';
      case 'low': return '⚪';
    }
  }

  private static readonly SHARE_SVG: TrustedHtml = trustedHtml(
    '<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M4 12v7a2 2 0 002 2h12a2 2 0 002-2v-7"/><polyline points="16 6 12 2 8 6"/><line x1="12" y1="2" x2="12" y2="15"/></svg>',
    'Static share icon SVG defined in source',
  );

  private buildTrendArrow(trend: CountryScore['trend'], change: number): HTMLElement {
    if (trend === 'rising') return h('span', { className: 'trend-up' }, `↑${change > 0 ? change : ''}`);
    if (trend === 'falling') return h('span', { className: 'trend-down' }, `↓${Math.abs(change)}`);
    return h('span', { className: 'trend-stable' }, '→');
  }

  private buildCountry(country: CountryScore): HTMLElement {
    const color = this.getLevelColor(country.level);
    const emoji = this.getLevelEmoji(country.level);

    const shareBtn = h('button', {
      className: 'cii-share-btn',
      dataset: { code: country.code, name: country.name },
      title: t('common.shareStory'),
    });
    shareBtn.appendChild(rawHtml(CIIPanel.SHARE_SVG));

    // First child: per-row FollowButton (size sm). Insertion happens
    // before the existing .cii-header so the star renders at the start
    // of the row. The host wrapper owns the button's innerHTML across
    // re-renders; teardown is tracked in `followButtonTeardowns` and
    // fired before every wholesale rebuild + on panel destroy.
    const followHost = h('span', {
      className: 'cii-follow-btn-host',
      dataset: { code: country.code },
    });
    const handle = renderFollowButton({
      countryCode: country.code,
      countryName: country.name,
      size: 'sm',
    });
    setTrustedHtml(followHost, trustedHtml(handle.html, "legacy direct innerHTML migration"));
    // Attach immediately. The host doesn't need to be DOM-connected for
    // `attach()` to install its delegated click + subscription listeners,
    // and `attach()` re-renders into the host so any state drift is
    // resolved on mount.
    const teardown = handle.attach(followHost);
    this.followButtonTeardowns.set(country.code, teardown);
    // Stop click bubbling so the per-row `onCountryClick` doesn't fire
    // when the user clicks the star (matches the `cii-share-btn`
    // stopPropagation pattern in `bindShareButtons`).
    followHost.addEventListener('click', (e) => e.stopPropagation());

    return h('div', { className: 'cii-country', dataset: { code: country.code } },
      followHost,
      h('div', { className: 'cii-header' },
        h('span', { className: 'cii-emoji' }, emoji),
        h('span', { className: 'cii-name' }, country.name),
        h('span', { className: 'cii-score' }, String(country.score)),
        this.buildTrendArrow(country.trend, country.change24h),
        shareBtn,
      ),
      h('div', { className: 'cii-bar-container' },
        h('div', { className: 'cii-bar', style: `width: ${country.score}%; background: ${color};` }),
      ),
      h('div', { className: 'cii-components' },
        h('span', { title: t('common.unrest') }, `U:${country.components.unrest}`),
        h('span', { title: t('common.conflict') }, `C:${country.components.conflict}`),
        h('span', { title: t('common.security') }, `S:${country.components.security}`),
        h('span', { title: t('common.information') }, `I:${country.components.information}`),
      ),
    );
  }

  private tearDownFollowButtons(): void {
    for (const teardown of this.followButtonTeardowns.values()) {
      try {
        teardown();
      } catch {
        /* swallow — teardown should never throw, but be defensive */
      }
    }
    this.followButtonTeardowns.clear();
  }

  /**
   * U6 — Build the list element from already-loaded scores. Inserts a
   * single "Following" / "All" section pair when BOTH groups are
   * non-empty; otherwise renders the unpartitioned list (no divider, no
   * label) so the zero-followed and all-followed cases match today's UX.
   *
   * Partition logic lives in `_cii-panel-partition.ts` so it's
   * unit-testable without the Panel/DOM/i18n transitive deps.
   *
   * Caller must call `tearDownFollowButtons()` BEFORE invoking this
   * (every row mounts a fresh FollowButton; the previous batch's
   * subscriptions must be released first).
   */
  private buildList(scores: CountryScore[]): HTMLElement {
    // Gate the partition input on the feature flag — `getFollowed()` reads
    // localStorage even when the flag is off (anonymous mode reads aren't
    // short-circuited, only mutations are). When the flag is OFF, treat
    // the followed list as `[]` so partitionByFollowed becomes a no-op:
    // rows render in the original score order, no FOLLOWING / ALL labels.
    // Without this gate, flag-off users would see partitioning + section
    // labels even though the FollowButton / chip surface is hidden.
    const followedCodes = isFollowFeatureEnabled() ? getFollowed() : [];
    const partition = partitionByFollowed(scores, followedCodes);

    if (!shouldRenderSectionLabels(partition)) {
      // Zero-followed OR all-followed → render the original order with
      // no divider. Behaviour identical to pre-U6.
      return h(
        'div',
        { className: 'cii-list' },
        ...scores.map((s) => this.buildCountry(s)),
      );
    }

    const { followed, unfollowed } = partition;
    const followingLabel = h(
      'div',
      { className: 'cii-section-label' },
      t('components.cii.sectionFollowing'),
    );
    const allLabel = h(
      'div',
      { className: 'cii-section-label' },
      t('components.cii.sectionAll'),
    );

    return h(
      'div',
      { className: 'cii-list' },
      followingLabel,
      ...followed.map((s) => this.buildCountry(s)),
      allLabel,
      ...unfollowed.map((s) => this.buildCountry(s)),
    );
  }

  private buildMethodologyFooter(): HTMLElement {
    return h('div', { className: 'cii-methodology-footer' },
      h('a', {
        href: CII_METHODOLOGY_HREF,
        target: '_blank',
        rel: 'noopener noreferrer',
      }, t('components.cii.methodologyLink')),
    );
  }

  private formatCachedSourceDetail(cached: Pick<CachedRiskScores, 'degraded' | 'stale'>): string {
    const flags: string[] = [];
    if (cached.degraded) flags.push(t('components.cii.sourceStates.degraded'));
    if (cached.stale) flags.push(t('components.cii.sourceStates.stale'));
    return flags.join(' · ');
  }

  private updateSourceBadge(cached: Pick<CachedRiskScores, 'degraded' | 'stale'> | null): void {
    if (!cached) {
      this.clearDataBadge();
      return;
    }
    const detail = this.formatCachedSourceDetail(cached);
    this.setDataBadge('cached', detail || undefined);
  }

  /**
   * U6 — Cheap re-render path used by the watchlist subscription. Rebuilds
   * the row list from the cached `this.scores` (no re-fetch) so the
   * partition order updates in one tick. No-op if no scores have been
   * loaded yet (the next refresh / renderFromCached will pick up the
   * watchlist on its own).
   */
  private rerenderRows(): void {
    if (this.scores.length === 0) return;
    const withData = this.scores.filter((s) => s.score > 0);
    if (withData.length === 0) return;
    this.tearDownFollowButtons();
    replaceChildren(this.content, this.buildList(withData), this.buildMethodologyFooter());
    this.bindShareButtons();
  }

  private bindShareButtons(): void {
    if (!this.onShareStory && !this.onCountryClick) return;

    this.content.querySelectorAll('.cii-country').forEach(el => {
      el.addEventListener('click', (e) => {
        const target = e.currentTarget as HTMLElement;
        const code = target.dataset.code;
        if (code && this.onCountryClick) {
          this.onCountryClick(code);
        }
      });
    });

    this.content.querySelectorAll('.cii-share-btn').forEach(btn => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        const el = e.currentTarget as HTMLElement;
        const code = el.dataset.code || '';
        const name = el.dataset.name || '';
        if (code && name && this.onShareStory) this.onShareStory(code, name);
      });
    });
  }

  public renderUnavailable(): void {
    this.scores = [];
    this.setCount(0);
    this.setErrorState(false);
    this.setDataBadge('unavailable');
    this.tearDownFollowButtons();
    replaceChildren(
      this.content,
      h('div', { className: 'empty-state' }, t('common.failedCII')),
      this.buildMethodologyFooter(),
    );
  }

  public renderFromCached(cached: CachedRiskScores): void {
    const scores = cached.cii.map(toCountryScore).filter(s => s.score > 0);
    if (scores.length === 0) return;
    this.scores = scores;
    this.updateSourceBadge(cached);
    this.setCount(scores.length);
    this.setErrorState(false);
    // Tear down previous FollowButtons before mounting the new batch.
    this.tearDownFollowButtons();
    replaceChildren(this.content, this.buildList(scores), this.buildMethodologyFooter());
    this.bindShareButtons();
    console.log(`[CIIPanel] Rendered ${scores.length} countries from cached/bootstrap data`);
  }

  public getScores(): CountryScore[] {
    return this.scores;
  }

  public override destroy(): void {
    this.tearDownFollowButtons();
    if (this.followedUnsubscribe) {
      try {
        this.followedUnsubscribe();
      } catch {
        /* swallow — unsubscribe should never throw, but be defensive */
      }
      this.followedUnsubscribe = null;
    }
    super.destroy();
  }
}