music: add support for date-encoding years

Add support for date-encoding years such as "YYYYMMDD".

This is a semi-common timestamp edge-case, it seems, primarily due to
taggers wanting to encode date information in older tag formats.

app/src/main/java/org/oxycblt/auxio/music/Date.kt

@@ -182,14 +182,25 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
          */
         private val ISO8601_REGEX =
             Regex(
-                """^(\d{4,})([-.](\d{2})([-.](\d{2})([T ](\d{2})([:.](\d{2})([:.](\d{2})(Z)?)?)?)?)?)?$""")
+                """^(\d{4})([-.](\d{2})([-.](\d{2})([T ](\d{2})([:.](\d{2})([:.](\d{2})(Z)?)?)?)?)?)?$""")
 
         /**
          * Create a [Date] from a year component.
          * @param year The year component.
          * @return A new [Date] of the given component, or null if the component is invalid.
          */
-        fun from(year: Int) = fromTokens(listOf(year))
+        fun from(year: Int) =
+            if (year in 10000000..100000000) {
+                // Year is actually more likely to be a separated date timestamp. Interpret
+                // it as such.
+                val stringYear = year.toString()
+                from(
+                    stringYear.substring(0..3).toInt(),
+                    stringYear.substring(4..5).toInt(),
+                    stringYear.substring(6..7).toInt())
+            } else {
+                fromTokens(listOf(year))
+            }
 
         /**
          * Create a [Date] from a date component.
@@ -222,8 +233,9 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
          */
         fun from(timestamp: String): Date? {
             val tokens =
-            // Match the input with the timestamp regex
-            (ISO8601_REGEX.matchEntire(timestamp) ?: return null)
+            // Match the input with the timestamp regex. If there is no match, see if we can
+            // fall back to some kind of year value.
+            (ISO8601_REGEX.matchEntire(timestamp) ?: return timestamp.toIntOrNull()?.let(::from))
                     .groupValues
                     // Filter to the specific tokens we want and convert them to integer tokens.
                     .mapIndexedNotNull { index, s -> if (index % 2 != 0) s.toIntOrNull() else null }
@@ -238,7 +250,7 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
          */
         private fun fromTokens(tokens: List<Int>): Date? {
             val validated = mutableListOf<Int>()
-            validateTokens(tokens, validated)
+            transformTokens(tokens, validated)
             if (validated.isEmpty()) {
                 // No token was valid, return null.
                 return null
@@ -252,7 +264,7 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
          * @param src The input tokens to validate.
          * @param dst The destination list to add valid tokens to.
          */
-        private fun validateTokens(src: List<Int>, dst: MutableList<Int>) {
+        private fun transformTokens(src: List<Int>, dst: MutableList<Int>) {
             dst.add(src.getOrNull(0)?.nonZeroOrNull() ?: return)
             dst.add(src.getOrNull(1)?.inRangeOrNull(1..12) ?: return)
             dst.add(src.getOrNull(2)?.inRangeOrNull(1..31) ?: return)
@@ -260,5 +272,7 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
             dst.add(src.getOrNull(4)?.inRangeOrNull(0..59) ?: return)
             dst.add(src.getOrNull(5)?.inRangeOrNull(0..59) ?: return)
         }
+
+        private fun transformYearToken(src: List<Int>, dst: MutableList<Int>) {}
     }
 }

app/src/main/java/org/oxycblt/auxio/music/extractor/MediaStoreExtractor.kt

@@ -305,7 +305,7 @@ abstract class MediaStoreExtractor(
         // MediaStore only exposes the year value of a file. This is actually worse than it
         // seems, as it means that it will not read ID3v2 TDRC tags or Vorbis DATE comments.
         // This is one of the major weaknesses of using MediaStore, hence the redundancy layers.
-        raw.date = cursor.getIntOrNull(yearIndex)?.let(Date::from)
+        raw.date = cursor.getStringOrNull(yearIndex)?.let(Date::from)
         // A non-existent album name should theoretically be the name of the folder it contained
         // in, but in practice it is more often "0" (as in /storage/emulated/0), even when it the
         // file is not actually in the root internal storage directory. We can't do anything to

app/src/main/java/org/oxycblt/auxio/music/extractor/MetadataExtractor.kt

@@ -293,7 +293,7 @@ class Task(context: Context, private val raw: Song.Raw) {
         // date tag that android supports, so it must be 15 years old or more!)
         (comments["originaldate"]?.run { Date.from(first()) }
                 ?: comments["date"]?.run { Date.from(first()) }
-                    ?: comments["year"]?.run { first().toIntOrNull()?.let(Date::from) })
+                    ?: comments["year"]?.run { Date.from(first()) })
             ?.let { raw.date = it }
 
         // Album

app/src/test/java/org/oxycblt/auxio/music/DateTest.kt

@@ -124,6 +124,12 @@ class DateTest {
         assertEquals(Date.from(0), null)
     }
 
+    @Test
+    fun date_fromYearDate() {
+        assertEquals("2016", Date.from(2016).toString())
+        assertEquals("2016", Date.from("2016").toString())
+    }
+
     @Test
     fun dateRange_fromDates() {
         val range =