import { proxyUrlFor } from '../media/registry.ts';
import { anchorOf, type Comment, type Media, type Post, type Quoted, type Segment } from '../types.ts';
import { html, raw, type Raw } from './html.ts';
import { badge, layout, originalUrlBlock } from './layout.ts';
import { renderMarkdown } from './markdown.ts';
import { linkify } from './text.ts';

/**
 * Put the ratio on the media itself, never on the figure around it. On the
 * figure, at the full width of the column, a portrait video forces a box
 * taller than the window and the rest of the post gets pushed off screen.
 */
function aspect(item: Media): string {
  return item.width && item.height ? `aspect-ratio: ${item.width} / ${item.height};` : '';
}

function renderItem(item: Media, index: number): Raw {
  const src = proxyUrlFor(item);

  if (item.kind === 'video') {
    const poster = item.poster ? proxyUrlFor(item.poster) : undefined;
    return html`<figure class="item item--video" data-index="${index}">
      <video
        controls
        playsinline
        preload="metadata"
        style="${aspect(item)}"
        ${poster ? html`poster="${poster}"` : ''}
      ><source src="${src}"></video>
      ${item.hls
        ? html`<figcaption class="item__note">Streaming format — plays natively in Safari.</figcaption>`
        : ''}
    </figure>`;
  }

  return html`<figure class="item item--image" data-index="${index}">
    <img
      src="${src}"
      alt="${item.alt ?? ''}"
      style="${aspect(item)}"
      loading="${index === 0 ? 'eager' : 'lazy'}"
      decoding="async"
    >
  </figure>`;
}

function renderMedia(media: Media[]): Raw {
  if (media.length === 0) return html``;

  const many = media.length > 1;
  return html`<section class="media" data-count="${media.length}">
    ${many
      ? html`<div class="media__bar">
          <span class="media__count"><span class="media__at">1</span> / ${media.length}</span>
          <div class="media__views" role="group" aria-label="Layout">
            <button type="button" class="media__view" data-view="swipe" aria-pressed="true">Swipe</button>
            <button type="button" class="media__view" data-view="grid" aria-pressed="false">Grid</button>
          </div>
        </div>`
      : ''}
    <div class="media__rail">${media.map((item, index) => renderItem(item, index))}</div>
  </section>`;
}

function renderText(segment: Segment, post: Post): Raw {
  if (!segment.text && !segment.title) return html``;
  return html`<div class="text">
    ${segment.title ? html`<h1 class="text__title">${segment.title}</h1>` : ''}
    ${segment.text ? linkify(segment.text, post.platform) : ''}
  </div>`;
}

function renderWhen(postedAt: string | undefined): Raw {
  if (!postedAt) return html``;
  const date = new Date(postedAt);
  if (Number.isNaN(date.getTime())) return html``;
  return html`<time datetime="${date.toISOString()}">${date.toLocaleString('en-CA', {
    dateStyle: 'medium',
    timeStyle: 'short',
  })}</time>`;
}

/**
 * The post being quoted, drawn as a post of its own inside the one quoting
 * it: its author, its words, its pictures, and a way to open it.
 *
 * The author line is the point. Lifting only the media out — which is what
 * this used to do — put someone else's picture under the quoter's name with
 * nothing to say so.
 */
function renderQuoted(quoted: Quoted, post: Post): Raw {
  const avatar = quoted.author.avatar ? proxyUrlFor(quoted.author.avatar) : undefined;

  return html`<blockquote class="quote">
    <header class="quote__who">
      ${avatar ? html`<img class="quote__avatar" src="${avatar}" alt="" loading="lazy">` : ''}
      ${quoted.author.displayName
        ? html`<span class="quote__name">${quoted.author.displayName}</span>`
        : ''}
      <span class="quote__handle">${quoted.author.handle}</span>
      ${renderWhen(quoted.postedAt)}
    </header>
    ${quoted.text ? html`<div class="quote__text">${linkify(quoted.text, post.platform)}</div>` : ''}
    ${renderMedia(quoted.media)}
    ${quoted.url
      ? html`<a class="quote__open" href="${quoted.url}" rel="noopener noreferrer nofollow" target="_blank">
          Open the quoted post on ${post.platformLabel}
        </a>`
      : ''}
  </blockquote>`;
}

/**
 * One post in the chain. When there is only one, the wrapper is invisible;
 * when there are several, each is separated and the one that was actually
 * linked is marked, since it may not be the first.
 */
function renderSegment(segment: Segment, post: Post, threaded: boolean): Raw {
  const above = post.textPosition === 'above';
  return html`<section class="segment" ${threaded && segment.isAnchor ? raw('data-anchor="true"') : ''} ${
    segment.quoted ? raw('data-quoted="true"') : ''
  }>
    ${threaded && segment.isAnchor
      ? html`<p class="segment__mark">the post you followed</p>`
      : ''}
    ${above ? renderText(segment, post) : ''}
    ${renderMedia(segment.media)}
    ${above ? '' : renderText(segment, post)}
    ${segment.quoted ? renderQuoted(segment.quoted, post) : ''}
  </section>`;
}

/** Short enough to sit on a comment's byline without wrapping. Absolute
 *  rather than "3 hours ago", because the page is cached for an hour and a
 *  relative time would quietly become wrong while it sat there. */
function shortWhen(postedAt: string | undefined): Raw {
  if (!postedAt) return html``;
  const date = new Date(postedAt);
  if (Number.isNaN(date.getTime())) return html``;
  return html`<time datetime="${date.toISOString()}">${date.toLocaleString('en-CA', {
    month: 'short',
    day: 'numeric',
    hour: 'numeric',
    minute: '2-digit',
  })}</time>`;
}

/**
 * A picture inside a comment.
 *
 * Through the proxy like everything else — a comment full of `preview.redd.it`
 * addresses would otherwise have the viewer's browser fetch every one of them
 * straight from Reddit, which is the thing this whole app exists to avoid.
 *
 * No dimensions to reserve space with: the size is in the payload but not in
 * the Markdown, so these are capped by the stylesheet and load at whatever
 * shape they are.
 */
function renderCommentImage(url: string, alt: string): string {
  return html`<img class="c__img" src="${proxyUrlFor({ url })}" alt="${alt}" loading="lazy" decoding="async">`
    .value;
}

/** Everything hanging off a comment, however deep. Shown only while it is
 *  collapsed, so what a fold is hiding is never a mystery. */
function descendantsOf(comment: Comment): number {
  return comment.replies.reduce((total, reply) => total + 1 + descendantsOf(reply), 0);
}

/**
 * One comment and everything under it.
 *
 * A `<details>` per comment, so collapsing works with the stylesheet turned
 * off and the keyboard alone, and takes the whole subtree with it because
 * the replies are nested inside rather than listed alongside.
 */
function renderComment(comment: Comment, depth: number): Raw {
  const marks = [
    comment.isAuthor ? 'OP' : undefined,
    comment.distinguished === 'moderator' ? 'MOD' : undefined,
    comment.distinguished === 'admin' ? 'ADMIN' : undefined,
  ].filter((mark) => mark !== undefined);

  return html`<details class="c" open data-depth="${depth}">
    <summary class="c__head">
      <span class="c__author">${comment.author}</span>
      ${marks.map((mark) => html`<span class="c__mark c__mark--${mark.toLowerCase()}">${mark}</span>`)}
      ${typeof comment.score === 'number'
        ? html`<span class="c__score">${comment.score} ${Math.abs(comment.score) === 1 ? 'point' : 'points'}</span>`
        : ''}
      ${shortWhen(comment.postedAt)}
      ${descendantsOf(comment) > 0
        ? html`<span class="c__hidden">+${descendantsOf(comment)} ${
            descendantsOf(comment) === 1 ? 'reply' : 'replies'
          }</span>`
        : ''}
    </summary>
    ${comment.text
      ? html`<div class="c__body">${renderMarkdown(comment.text, renderCommentImage)}</div>`
      : ''}
    ${comment.replies.length || comment.moreReplies
      ? html`<div class="c__replies">
          ${comment.replies.map((reply) => renderComment(reply, depth + 1))}
          ${comment.moreReplies
            ? html`<p class="c__more">${comment.moreReplies} more ${
                comment.moreReplies === 1 ? 'reply' : 'replies'
              }, on Reddit</p>`
            : ''}
        </div>`
      : ''}
  </details>`;
}

/**
 * The conversation under the post, where the platform has one.
 *
 * Everything the first page carried, in the order it was ranked. What is
 * missing is what was behind a "load more" — following those means going to
 * the platform, so they are counted rather than pretended away.
 */
function renderComments(post: Post): Raw {
  const comments = post.comments;
  if (!comments?.length) return html``;

  const threads = comments.length;
  const shown = comments.reduce((total, comment) => total + 1 + descendantsOf(comment), 0);
  const total = post.commentCount;

  return html`<section class="thread" data-platform="${post.platform}">
    <header class="thread__head">
      <h2 class="thread__title">Comments</h2>
      <span class="thread__count">${
        total !== undefined && total > shown ? html`${shown} of ${total}` : html`${shown}`
      }, in ${threads} ${threads === 1 ? 'thread' : 'threads'}</span>
      <button type="button" class="thread__toggle" data-collapsed="false" hidden>Collapse all</button>
    </header>
    <div class="thread__list">${comments.map((comment) => renderComment(comment, 0))}</div>
    ${post.moreComments
      ? html`<p class="thread__more">${post.moreComments} more, behind “load more” on Reddit.</p>`
      : ''}
  </section>`;
}

export function renderPost(post: Post): string {
  const avatar = post.author.avatar ? proxyUrlFor(post.author.avatar) : undefined;
  const threaded = post.segments.length > 1;
  const anchor = anchorOf(post);

  const body = html`<article class="post" data-platform="${post.platform}" ${
    threaded ? raw(`data-segments="${post.segments.length}"`) : ''
  }>
    <header class="post__head">
      ${badge(post.platform, post.platformLabel)}
      <div class="who">
        ${avatar ? html`<img class="who__avatar" src="${avatar}" alt="" loading="lazy">` : ''}
        <div class="who__names">
          ${post.author.displayName ? html`<span class="who__name">${post.author.displayName}</span>` : ''}
          <span class="who__handle">${post.author.handle}</span>
        </div>
      </div>
    </header>

    ${post.segments.map((segment) => renderSegment(segment, post, threaded))}

    <footer class="post__foot">
      ${renderWhen(anchor?.postedAt)}
      ${originalUrlBlock(post.originalUrl, post.platformLabel)}
    </footer>
  </article>
  ${renderComments(post)}`;

  const who = post.author.displayName ?? post.author.handle;
  return layout(`${who} on ${post.platformLabel}`, body);
}