Add CSS font matching algorithm when rendering html

.gitignore

@@ -1,3 +1,4 @@
+.vscode
 .idea
 .DS_Store
 node_modules/

src/libs/fontFace.js

@@ -0,0 +1,292 @@
+function toLookup(arr) {
+  return arr.reduce((lookup, name, index) => {
+    lookup[name] = index;
+
+    return lookup;
+  }, {});
+}
+
+var fontStyleOrder = {
+  italic: ["italic", "oblique", "normal"],
+  oblique: ["oblique", "italic", "normal"],
+  normal: ["normal", "oblique", "italic"]
+};
+
+var fontStretchOrder = [
+  "ultra-condensed",
+  "extra-condensed",
+  "condensed",
+  "semi-condensed",
+  "normal",
+  "semi-expanded",
+  "expanded",
+  "extra-expanded",
+  "ultra-expanded"
+];
+
+// For a given font-stretch value, we need to know where to start our search
+// from in the fontStretchOrder list.
+var fontStretchLookup = toLookup(fontStretchOrder);
+
+var fontWeights = [100, 200, 300, 400, 500, 600, 700, 800, 900];
+var fontWeightsLookup = toLookup(fontWeights);
+
+function normalizeFontStretch(stretch) {
+  stretch = stretch || "normal";
+
+  return typeof fontStretchLookup[stretch] === "number" ? stretch : "normal";
+}
+
+function normalizeFontStyle(style) {
+  style = style || "normal";
+
+  return fontStyleOrder[style] ? style : "normal";
+}
+
+function normalizeFontWeight(weight) {
+  if (!weight) {
+    return 400;
+  }
+
+  if (typeof weight === "number") {
+    // Ignore values which aren't valid font-weights.
+    return weight >= 100 && weight <= 900 && weight % 100 === 0 ? weight : 400;
+  }
+
+  if (/^\d00$/.test(weight)) {
+    return parseInt(weight);
+  }
+
+  switch (weight) {
+    case "bold":
+      return 700;
+
+    case "normal":
+    default:
+      return 400;
+  }
+}
+
+export function normalizeFontFace(fontFace) {
+  var family = fontFace.family.replace(/"|'/g, "").toLowerCase();
+
+  var style = normalizeFontStyle(fontFace.style);
+  var weight = normalizeFontWeight(fontFace.weight);
+  var stretch = normalizeFontStretch(fontFace.stretch);
+
+  return {
+    family: family,
+    style: style,
+    weight: weight,
+    stretch: stretch,
+    src: fontFace.src || [],
+
+    // The ref property maps this font-face to the font
+    // added by the .addFont() method.
+    ref: fontFace.ref || {
+      name: family,
+      style: [stretch, style, weight].join(" ")
+    }
+  };
+}
+
+/**
+ * Turns a list of font-faces into a map, for easier lookup when resolving
+ * fonts.
+ * */
+export function buildFontFaceMap(fontFaces) {
+  var map = {};
+
+  for (var i = 0; i < fontFaces.length; ++i) {
+    var normalized = normalizeFontFace(fontFaces[i]);
+
+    var name = normalized.family;
+    var stretch = normalized.stretch;
+    var style = normalized.style;
+    var weight = normalized.weight;
+
+    map[name] = map[name] || {};
+
+    map[name][stretch] = map[name][stretch] || {};
+    map[name][stretch][style] = map[name][stretch][style] || {};
+    map[name][stretch][style][weight] = normalized;
+  }
+
+  return map;
+}
+
+/**
+ * Searches a map of stretches, weights, etc. in the given direction and
+ * then, if no match has been found, in the opposite directions.
+ *
+ * @param {Object.<string, any>} matchingSet A map of the various font variations.
+ * @param {any[]} order The order of the different variations
+ * @param {number} pivot The starting point of the search in the order list.
+ * @param {-1 | 1} dir The initial direction of the search (desc = -1, asc = 1)
+ */
+
+function searchFromPivot(matchingSet, order, pivot, dir) {
+  var i;
+
+  for (i = pivot; i >= 0 && i < order.length; i += dir) {
+    if (matchingSet[order[i]]) {
+      return matchingSet[order[i]];
+    }
+  }
+
+  for (i = pivot; i >= 0 && i < order.length; i -= dir) {
+    if (matchingSet[order[i]]) {
+      return matchingSet[order[i]];
+    }
+  }
+}
+
+function resolveFontStretch(stretch, matchingSet) {
+  if (matchingSet[stretch]) {
+    return matchingSet[stretch];
+  }
+
+  var pivot = fontStretchLookup[stretch];
+
+  // If the font-stretch value is normal or more condensed, we want to
+  // start with a descending search, otherwise we should do ascending.
+  var dir = pivot <= fontStretchLookup["normal"] ? -1 : 1;
+  var match = searchFromPivot(matchingSet, fontStretchOrder, pivot, dir);
+
+  if (!match) {
+    // Since a font-family cannot exist without having at least one stretch value
+    // we should never reach this point.
+    throw new Error(
+      "Could not find a matching font-stretch value for " + stretch
+    );
+  }
+
+  return match;
+}
+
+function resolveFontStyle(fontStyle, matchingSet) {
+  if (matchingSet[fontStyle]) {
+    return matchingSet[fontStyle];
+  }
+
+  var ordering = fontStyleOrder[fontStyle];
+
+  for (var i = 0; i < ordering.length; ++i) {
+    if (matchingSet[ordering[i]]) {
+      return matchingSet[ordering[i]];
+    }
+  }
+
+  // Since a font-family cannot exist without having at least one style value
+  // we should never reach this point.
+  throw new Error("Could not find a matching font-style for " + fontStyle);
+}
+
+function resolveFontWeight(weight, matchingSet) {
+  if (matchingSet[weight]) {
+    return matchingSet[weight];
+  }
+
+  if (weight === 400 && matchingSet[500]) {
+    return matchingSet[500];
+  }
+
+  if (weight === 500 && matchingSet[400]) {
+    return matchingSet[400];
+  }
+
+  var pivot = fontWeightsLookup[weight];
+
+  // If the font-stretch value is normal or more condensed, we want to
+  // start with a descending search, otherwise we should do ascending.
+  var dir = weight < 400 ? -1 : 1;
+  var match = searchFromPivot(matchingSet, fontWeights, pivot, dir);
+
+  if (!match) {
+    // Since a font-family cannot exist without having at least one stretch value
+    // we should never reach this point.
+    throw new Error(
+      "Could not find a matching font-weight for value " + weight
+    );
+  }
+
+  return match;
+}
+
+var defaultGenericFontFamilies = {
+  "sans-serif": "helvetica",
+  fixed: "courier",
+  monospace: "courier",
+  terminal: "courier",
+  cursive: "times",
+  fantasy: "times",
+  serif: "times"
+};
+
+function ruleToString(rule) {
+  return [rule.stretch, rule.style, rule.weight, rule.family].join(" ");
+}
+
+export function resolveFontFace(fontFaceMap, rules, opts) {
+  opts = opts || {};
+
+  var defaultFontFamily = opts.defaultFontFamily || "times";
+  var genericFontFamilies = Object.assign(
+    {},
+    defaultGenericFontFamilies,
+    opts.genericFontFamilies || {}
+  );
+
+  var rule = null;
+  var matches = null;
+
+  for (var i = 0; i < rules.length; ++i) {
+    rule = normalizeFontFace(rules[i]);
+
+    if (genericFontFamilies[rule.family]) {
+      rule.family = genericFontFamilies[rule.family];
+    }
+
+    if (fontFaceMap.hasOwnProperty(rule.family)) {
+      matches = fontFaceMap[rule.family];
+
+      break;
+    }
+  }
+
+  // Always fallback to a known font family.
+  matches = matches || fontFaceMap[defaultFontFamily];
+
+  if (!matches) {
+    // At this point we should definitiely have a font family, but if we
+    // don't there is something wrong with our configuration
+    throw new Error(
+      "Could not find a font-family for the rule '" +
+        ruleToString(rule) +
+        "' and default family '" +
+        defaultFontFamily +
+        "'."
+    );
+  }
+
+  matches = resolveFontStretch(rule.stretch, matches);
+  matches = resolveFontStyle(rule.style, matches);
+  matches = resolveFontWeight(rule.weight, matches);
+
+  if (!matches) {
+    // We should've fount
+    throw new Error(
+      "Failed to resolve a font for the rule '" + ruleToString(rule) + "'."
+    );
+  }
+
+  return matches;
+}
+
+/**
+ * Builds a style id for use with the addFont() method.
+ * @param {FontFace} font
+ */
+export function toStyleName(font) {
+  return [font.weight, font.style, font.stretch].join(" ");
+}