// ============================================================
// DOCUMENT SPEC
// ============================================================
// A flat list of blocks a Word renderer can draw, built from either source: the
// typed deck a presentation is stored as, or the markdown an article is.
//
// Going deck → markdown → pandoc lost the structure twice. A comparison became
// two headings and two lists, a callout became bold text, and a table survived
// only because pandoc happens to parse pipe tables. Coming from the deck
// directly, a comparison is a two-column table, a callout is a shaded box, and a
// figure keeps its caption.

var BLOCK = ['heading', 'para', 'bullets', 'table', 'callout', 'image'];

function text(value, max) {
  return String(value === undefined || value === null ? '' : value).slice(0, max || 4000).trim();
}

/** Blocks from a stored deck. Slides become sections of a handout. */
function fromDeck(deck, images) {
  var blocks = [];
  var byJob = images || {};
  (deck.slides || []).forEach(function (slide) {
    if (slide.type === 'title') return;   // the document has its own title page
    if (slide.heading) blocks.push({ type: 'heading', level: slide.type === 'section' ? 1 : 2,
                                     text: text(slide.heading, 300) });

    if (slide.type === 'callout' && slide.text) {
      blocks.push({ type: 'callout', text: text(slide.text) });
    } else if (slide.type === 'table') {
      blocks.push({ type: 'table', header: (slide.header || []).map(function (c) { return text(c, 300); }),
                    rows: (slide.rows || []).map(function (row) {
                      return row.map(function (c) { return text(c, 600); });
                    }) });
    } else if (slide.type === 'compare' && (slide.columns || []).length === 2) {
      // Side by side stays side by side. Flattened to two lists it stopped
      // being a comparison, which was the whole reason for the layout.
      var left = slide.columns[0], right = slide.columns[1];
      var depth = Math.max((left.bullets || []).length, (right.bullets || []).length);
      var rows = [];
      for (var i = 0; i < depth; i++) {
        rows.push([text((left.bullets[i] || {}).text, 600), text((right.bullets[i] || {}).text, 600)]);
      }
      blocks.push({ type: 'table', header: [text(left.label, 120), text(right.label, 120)], rows: rows });
    } else {
      var items = (slide.bullets || []).concat(slide.left || []).concat(slide.right || []);
      if (items.length) {
        blocks.push({ type: 'bullets', items: items.map(function (b) {
          return { text: text(b.text, 1200), level: Math.max(0, Math.min(4, b.level || 0)) };
        }) });
      }
    }

    if (slide.image_job && byJob[slide.image_job]) {
      blocks.push({ type: 'image', path: byJob[slide.image_job], caption: text(slide.caption, 300) });
    }
    if (slide.notes) blocks.push({ type: 'para', text: text(slide.notes, 2000), muted: true });
  });
  return blocks;
}

function parseTable(lines, at) {
  var rows = [];
  var i = at;
  while (i < lines.length && /^\s*\|/.test(lines[i])) { rows.push(lines[i]); i++; }
  if (rows.length < 2) return null;
  function cells(line) {
    return line.trim().replace(/^\||\|$/g, '').split('|').map(function (c) { return c.trim(); });
  }
  var header = cells(rows[0]);
  var start = /^[\s|:-]+$/.test(rows[1]) ? 2 : 1;
  var body = rows.slice(start).map(cells).filter(function (r) { return r.some(Boolean); });
  if (!body.length) return null;
  return { block: { type: 'table', header: header, rows: body }, next: i };
}

/** Blocks from markdown. What an article is stored as. */
function fromMarkdown(markdown) {
  var lines = String(markdown || '').replace(/\r\n/g, '\n').split('\n');
  var blocks = [];
  var bullets = null;
  var para = [];

  function flushPara() {
    if (!para.length) return;
    blocks.push({ type: 'para', text: para.join(' ').trim() });
    para = [];
  }
  function flushBullets() {
    if (!bullets) return;
    blocks.push({ type: 'bullets', items: bullets });
    bullets = null;
  }
  function flush() { flushPara(); flushBullets(); }

  for (var i = 0; i < lines.length; i++) {
    var line = lines[i];
    if (/^%\s*/.test(line)) continue;                      // pandoc title block

    if (/^\s*\|/.test(line)) {
      var table = parseTable(lines, i);
      if (table) { flush(); blocks.push(table.block); i = table.next - 1; continue; }
    }

    var heading = /^(#{1,6})\s+(.*)$/.exec(line);
    if (heading) { flush(); blocks.push({ type: 'heading', level: Math.min(heading[1].length, 4),
                                          text: heading[2].trim() }); continue; }

    var bullet = /^(\s*)(?:[-*+]|\d+\.)\s+(.*)$/.exec(line);
    if (bullet) {
      flushPara();
      if (!bullets) bullets = [];
      bullets.push({ text: bullet[2].trim(), level: Math.min(4, Math.floor(bullet[1].length / 2)) });
      continue;
    }

    var quote = /^\s*>\s?(.*)$/.exec(line);
    if (quote) { flush(); blocks.push({ type: 'callout', text: quote[1].trim() }); continue; }

    if (/^\s*[-*_]{3,}\s*$/.test(line)) { flush(); continue; }

    if (!line.trim()) { flush(); continue; }
    flushBullets();
    para.push(line.trim());
  }
  flush();
  return blocks;
}

/**
 * The whole document. `deck` wins when there is one — it is the typed source,
 * and the markdown beside it is a serialisation of it.
 */
function build(options) {
  var opts = options || {};
  var blocks = opts.deck && (opts.deck.slides || []).length
    ? fromDeck(opts.deck, opts.images)
    : fromMarkdown(opts.markdown);
  var meta = opts.deck || {};
  var first = (opts.markdown || '').match(/^%\s*(.+)$/m);
  return {
    title: text(meta.title || (first && first[1]) || opts.title || 'Resource', 300),
    subtitle: text(meta.subtitle, 300),
    date: text(meta.date, 120),
    blocks: blocks.filter(function (b) { return BLOCK.indexOf(b.type) !== -1; })
  };
}

module.exports = { build, fromDeck, fromMarkdown, BLOCK };