1 files changed, 66 insertions, 4 deletions
diff --git a/lib/unitsToRanges.js b/lib/unitsToRanges.js
index 8ffd7b0..eebd3ef 100644
--- a/lib/unitsToRanges.js
+++ b/lib/unitsToRanges.js
@@ -1,23 +1,85 @@
 /**
- * Convert a list of unit numbers into an addr:flats list. eg. converts 1,2,3,5 into 1-3;5
+ * Convert a list of unit numbers into an addr:flats list. Examples:
+ * 1,2,3,5 => 1-3;5
+ * 1a,2a,3a,5 => 1a-3a;5
+ * 1,2,3-5 => 1-5
+ * 1,2,3a-5a => 1-2;3a-5a
  *
  * @param {Array} units
  *
  * @returns {string} addr:flats list
  */
 module.exports = (units) => {
+  const regexp = /^(?<pre>\D*)(?<num>\d*)(?<suf>\D*)$/
+
+  // expand out any existing ranges which may be mixed into the input
+  const expandedUnits = units
+    .slice()
+    .reduce((acc, cur) => {
+      const rangeParts = cur.split('-')
+      if (rangeParts.length === 2) {
+        // was a range, pull out prefix and suffix
+        const fromMatch = rangeParts[0].match(regexp)
+        const toMatch = rangeParts[1].match(regexp)
+
+        // matching prefix and suffix
+        if (fromMatch.groups.pre === toMatch.groups.pre && fromMatch.groups.suf === toMatch.groups.suf) {
+          for (let i = fromMatch.groups.num; i <= toMatch.groups.num; i++) {
+            acc.push(`${fromMatch.groups.pre}${i}${fromMatch.groups.suf}`)
+          }
+        } else {
+          // prefix/suffix don't match in the from-to, so just pass as is
+          console.log(`passed a range with different prefix/suffix: ${rangeParts[0]}-${rangeParts[1]}`)
+          acc.push(cur)
+        }
+      } else if (rangeParts.length > 2) {
+        // 1-2-3 not sure if this ever occures, but just pass as is
+        console.log(`Unsupported range ${cur}`)
+        acc.push(cur)
+      } else {
+        // was not a range
+        acc.push(cur)
+      }
+      return acc
+    }, [])
+
+  // combine individual unit values into ranges
+  const existingRanges = []
+
   // adapted from https://stackoverflow.com/a/54973116/6702659
-  const unitRanges = units
+  const formedRanges = expandedUnits
     .slice()
+    .map(unit => {
+      if (unit.split('-').length > 1) {
+        existingRanges.push(unit)
+        return []
+      } else {
+        return [unit]
+      }
+    })
+    .flat()
     .sort((a, b) => a - b)
     .reduce((acc, cur, idx, src) => {
-      if ((idx > 0) && ((cur - src[idx - 1]) === 1)) {
-        acc[acc.length - 1][1] = cur
+      const curParts = cur.match(regexp)
+      const prevParts = idx > 0 ? src[idx - 1].match(regexp) : null
+
+      const curNum = curParts.groups.num
+      const prevNum = prevParts ? prevParts.groups.num : null
+
+      if ((idx > 0) && ((curNum - prevNum) === 1)) {
+        if (prevParts ? (curParts.groups.pre === prevParts.groups.pre && curParts.groups.suf === prevParts.groups.suf) : true) {
+          acc[acc.length - 1][1] = cur
+        } else {
+          acc.push([cur])
+        }
       } else {
         acc.push([cur])
       }
       return acc
     }, [])
     .map(range => range.join('-'))
+
+  const unitRanges = [...formedRanges, ...existingRanges]
+
   return unitRanges.length ? unitRanges.join(';') : null
 }