src/anki/notebuilder: allow filtering only lowest frequency

This feature extends the ``{frequencies}`` marker with the extended
marker syntax and adds two new options: ``min-value`` which allows to
export only the lowest value frequency out of all the options and
``value-only`` which strips the dictionary name and html list format to
keep only raw numbers.

This allow memento to support card format that rely on raw frequency
values to sort their cards.

Author: eyalmazuz

src/anki/notebuilder.cpp

@@ -420,6 +420,53 @@ static bool createScreenshotHelper(
     return true;
 }
 
+/**
+ * Parses the frequency string into a double.
+ * @param frequency The string representation of the current frequency.
+ * @return Float value of the frequency, nullopt if it could not be parsed.
+ */
+[[nodiscard]]
+static std::optional<double> parseFrequencyValue(const QString &frequency)
+{
+    const QRegularExpression FLOAT_ONLY_REGEX(
+        "^[+-]?([0-9]+([.][0-9]*)?|[.][0-9]+)"
+    );
+
+    QRegularExpressionMatch numberMatch = FLOAT_ONLY_REGEX.match(frequency);
+    if (!numberMatch.hasMatch())
+    {
+        if (frequency == "★")
+        {
+            return 20.0;
+        }
+        else if (frequency == "★★")
+        {
+            return 40.0;
+        }
+        else if (frequency == "★★★")
+        {
+            return 60.0;
+        }
+        else if (frequency == "★★★★")
+        {
+            return 80.0;
+        }
+        else if (frequency == "★★★★★")
+        {
+            return 100.0;
+        }
+        return {};
+    }
+
+    bool ok = false;
+    double frequencyValue = numberMatch.captured().toDouble(&ok);
+    if (!ok)
+    {
+        return {};
+    }
+    return frequencyValue;
+}
+
 /* End Helper Functions */
 /* Begin Marker Functions */
 
@@ -486,27 +533,92 @@ static QString getFuriganaPlain(const Term &term)
 /**
  * Builds the HTML string for the frequencies marker.
  * @param frequencies The frequencies to use.
+ * @param args Extended marker syntax args.
  * @return The string for the {frequency} marker.
  */
 [[nodiscard]]
-static QString buildFrequencies(const QList<Frequency> &frequencies)
+static QString buildFrequencies(
+    const QList<Frequency> &frequencies,
+    const QHash<QString, QString> &args)
 {
     if (frequencies.isEmpty())
     {
         return "";
     }
 
+    constexpr const char *VALUE_ONLY_KEY = "value-only";
+    constexpr const char *MIN_VALUE_KEY = "min-value";
+    constexpr const double MIN_VALUE_DEFAULT = 9999999.0;
+
+    bool valueOnly = false;
+    bool minValueOnly = false;
+
+    QString minFreqDictionary;
+    double minFreq = MIN_VALUE_DEFAULT;
+    QString minFreqStr;
+
+    if (args.contains(VALUE_ONLY_KEY))
+    {
+        valueOnly = QVariant(args[VALUE_ONLY_KEY]).toBool();
+    }
+    if (args.contains(MIN_VALUE_KEY))
+    {
+        minValueOnly = QVariant(args[MIN_VALUE_KEY]).toBool();
+    }
+
     QString freqStr;
-    freqStr += "<ul>";
+    if (!valueOnly)
+    {
+        freqStr += "<ul>";
+    }
     for (const Frequency &freq : frequencies)
     {
-        freqStr += "<li>";
-        freqStr += freq.dictionary;
-        freqStr += freq.dictionary.endsWith(':') ? " " : ": ";
+        if (!valueOnly)
+        {
+            freqStr += "<li>";
+            freqStr += freq.dictionary;
+            freqStr += freq.dictionary.endsWith(':') ? " " : ": ";
+        }
         freqStr += freq.freq;
-        freqStr += "</li>";
+        if (valueOnly)
+        {
+            freqStr += "<br>";
+        }
+        else
+        {
+            freqStr += "</li>";
+        }
+
+        std::optional<double> freqValue = parseFrequencyValue(freq.freq);
+        if (minValueOnly && freqValue && *freqValue < minFreq)
+        {
+            minFreq = *freqValue;
+            minFreqStr = freq.freq;
+            minFreqDictionary = freq.dictionary;
+            minFreqDictionary += freq.dictionary.endsWith(':') ? " " : ": ";
+        }
+    }
+    if (!valueOnly)
+    {
+        freqStr += "</ul>";
+    }
+
+    if (minValueOnly)
+    {
+        if (!valueOnly)
+        {
+            freqStr = "<ul>";
+            freqStr += "<li>";
+            freqStr += minFreqDictionary;
+            freqStr += minFreqStr;
+            freqStr += "</li>";
+            freqStr += "</ul>";
+        }
+        else
+        {
+            freqStr = std::move(minFreqStr);
+        }
     }
-    freqStr += "</ul>";
 
     if (freqStr == "<ul></ul>")
     {
@@ -1534,7 +1646,7 @@ static MarkerResult processMarkerCommon(
     }
     else if (marker.marker == Anki::Marker::FREQUENCIES)
     {
-        result.text = buildFrequencies(exp.frequencies);
+        result.text = buildFrequencies(exp.frequencies, marker.args);
         return result;
     }
     else if (marker.marker == Anki::Marker::FREQ_HARMONIC_RANK)

src/gui/widgets/settings/ankisettingshelp.ui

@@ -1725,6 +1725,50 @@ These will expand to larger expressions in the final card.</string>
              </property>
             </widget>
            </item>
+           <item row="6" column="0" alignment="Qt::AlignmentFlag::AlignHCenter">
+            <widget class="QLabel" name="labelExtendedFrequencyMinValue">
+             <property name="font">
+              <font>
+               <bold>true</bold>
+              </font>
+             </property>
+             <property name="text">
+              <string>min-value</string>
+             </property>
+             <property name="textInteractionFlags">
+              <set>Qt::TextInteractionFlag::TextSelectableByKeyboard|Qt::TextInteractionFlag::TextSelectableByMouse</set>
+             </property>
+            </widget>
+           </item>
+           <item row="6" column="1">
+            <widget class="QLabel" name="labelExtendedFrequencyMinValueEx">
+             <property name="text">
+              <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Only export the lowest value frequency. Applies to marker &lt;span style=&quot; font-weight:700;&quot;&gt;{frequencies}&lt;/span&gt;. Default value: false.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+             </property>
+            </widget>
+           </item>
+           <item row="7" column="0" alignment="Qt::AlignmentFlag::AlignHCenter">
+            <widget class="QLabel" name="labelExtendedFrequencyValueOnly">
+             <property name="font">
+              <font>
+               <bold>true</bold>
+              </font>
+             </property>
+             <property name="text">
+              <string>value-only</string>
+             </property>
+             <property name="textInteractionFlags">
+              <set>Qt::TextInteractionFlag::TextSelectableByKeyboard|Qt::TextInteractionFlag::TextSelectableByMouse</set>
+             </property>
+            </widget>
+           </item>
+           <item row="7" column="1">
+            <widget class="QLabel" name="labelExtendedFrequencyValueOnlyEx">
+             <property name="text">
+              <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Export frequency values without the dictionary names. Applies to marker &lt;span style=&quot; font-weight:700;&quot;&gt;{frequencies}&lt;/span&gt;. Default value: false.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+             </property>
+            </widget>
+           </item>
           </layout>
          </widget>
         </widget>