Fix Fayda FAN false positive on adjacent date-of-birth dates

feature/external-credential/src/main/java/com/simprints/feature/externalcredential/screens/scanocr/usecase/FaydaCardOcrReaderUseCase.kt

@@ -5,19 +5,20 @@
 import javax.inject.Inject
 
 internal class FaydaCardOcrReaderUseCase @Inject constructor() {
-    operator fun invoke(ocrReader: OcrReader): OcrScanResult.FaydaCard? {
-        val credential = ocrReader.find {
-            matchesCondition { line ->
-                // Removing non-digits from the line readout. Checking if remaining digits match FAN_PATTERN
-                line.filter(Char::isDigit).matches(FAN_PATTERN)
-            }
-        } ?: return null
-        val credentialText = credential.text.filter(Char::isDigit)
-        return OcrScanResult.FaydaCard(credential.copy(text = credentialText))
+    operator fun invoke(ocrReader: OcrReader): OcrScanResult.FaydaCard? = ocrReader.ocrText.allLines.firstNotNullOfOrNull { line ->
+        FAN_OCR_PATTERN.find(line.text)?.let { match ->
+            OcrScanResult.FaydaCard(line.copy(text = match.value.filter(Char::isDigit)))
+        }
     }
 
     companion object {
-        // Fayda Alias Number (FAN): exactly 16 digits after stripping all non-digit characters
+        // Fayda Alias Number (FAN): exactly 16 digits
         val FAN_PATTERN = Regex("^\\d{16}$")
+
+        // FAN within an OCR line: 16 digits, optionally split by OCR into up to 4 groups separated by single whitespace
+        // characters, and not part of a longer digit run. Punctuation between digits and more than 4 groups are not
+        // allowed, so that adjacent dates such as "07/02/1998 | 2005/10/17" are not read as a FAN, even if OCR reads the
+        // separators as spaces ("07 02 1998 2005 10 17").
+        val FAN_OCR_PATTERN = Regex("(?<!\\d\\s?)(?=(?:\\d+\\s){0,3}\\d+(?!\\s?\\d))\\d(?:\\s?\\d){15}(?!\\s?\\d)")
     }
 }

feature/external-credential/src/test/java/com/simprints/feature/externalcredential/screens/scanocr/usecase/FaydaCardOcrReaderUseCaseTest.kt

@@ -16,16 +16,32 @@ internal class FaydaCardOcrReaderUseCaseTest {
         "0000000000000000",
         "9999999999999999",
     )
-    private val validFansWithNoise = listOf(
+    private val validFansWithWhitespace = listOf(
         "1234 5678 1234 5678",
-        "1234-5678-1234-5678",
-        "1234.5678.1234.5678",
+        "12345678 12345678",
+        "258094592481 5610",
+        "1 23456781234567 8",
+    )
+    private val linesContainingFan = mapOf(
+        "FAN 8642370540168134" to "8642370540168134",
+        "8642370540168134 FAN" to "8642370540168134",
+        "ቁጥር: 2580945924815610" to "2580945924815610",
     )
     private val invalidFans = listOf(
-        "123456781234567",   // 15 digits
+        "123456781234567", // 15 digits
         "12345678123456789", // 17 digits
+        "1234567812345678 9", // 17 digits, last one separated by whitespace
         "ABCDEFGHIJKLMNOP", // 16 letters, 0 digits
         "1234567812345A78", // letter in the middle
+        "1234-5678-1234-5678", // punctuation between digits
+        "1234.5678.1234.5678", // punctuation between digits
+        "1234  5678  1234  5678", // more than one whitespace between digits
+        "07/02/1998 | 2005/10/17", // date of birth line (Gregorian | Ethiopian)
+        "25/12/2000 | 2008/08/31", // date of birth line (Gregorian | Ethiopian)
+        "07/02/1998 2005/10/17", // date of birth line with separator lost by OCR
+        "07 02 1998 2005 10 17", // date of birth line with all separators read as spaces by OCR
+        "07 02 1998 | 2005 10 17", // date of birth line with slashes read as spaces by OCR
+        "1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8", // more than 4 groups
         "",
     )
 
@@ -44,13 +60,21 @@ internal class FaydaCardOcrReaderUseCaseTest {
     }
 
     @Test
-    fun `returns matching line and strips non-digit characters from FAN`() {
-        validFansWithNoise.forEachIndexed { id, fan ->
+    fun `returns matching line and strips whitespace from FAN`() {
+        validFansWithWhitespace.forEachIndexed { id, fan ->
             val reader = buildReader(line(id = id, text = fan, top = 100))
             assertThat(useCase(reader)?.credential?.text).isEqualTo(fan.filter(Char::isDigit))
         }
     }
 
+    @Test
+    fun `extracts FAN from line containing other text`() {
+        linesContainingFan.entries.forEachIndexed { id, (text, fan) ->
+            val reader = buildReader(line(id = id, text = text, top = 100))
+            assertThat(useCase(reader)?.credential?.text).isEqualTo(fan)
+        }
+    }
+
     @Test
     fun `returns null for invalid FAN formats`() {
         invalidFans.forEachIndexed { id, fan ->
@@ -59,6 +83,18 @@ internal class FaydaCardOcrReaderUseCaseTest {
         }
     }
 
+    @Test
+    fun `skips date of birth line and returns FAN line`() {
+        val reader = buildReader(
+            line(id = 0, text = "07/02/1998 | 2005/10/17", top = 100),
+            line(id = 1, text = "30/07/2026 | 08/04/2034", top = 150),
+            line(id = 2, text = "8642370540168134", top = 200),
+        )
+        val result = useCase(reader)
+        assertThat(result?.credential?.id).isEqualTo(2)
+        assertThat(result?.credential?.text).isEqualTo("8642370540168134")
+    }
+
     private fun buildReader(vararg lines: OcrLine) = OcrReader(
         OcrText(allLines = lines.toList()),
     )