feat: implement the header parameter "headers=false" to disable the h…

…eader in the returned CSV/TSV #624

lapis2/src/main/kotlin/org/genspectrum/lapis/controller/ControllerDescriptions.kt

@@ -50,8 +50,10 @@ const val OFFSET_DESCRIPTION =
     """The offset of the first entry to return in the response. 
     This is useful for pagination in combination with \"limit\"."""
 const val FORMAT_DESCRIPTION =
-    """The data format of the response. Alternatively, the data format can be specified by setting the 
-    \"Accept\"-header. When both are specified, this parameter takes precedence."""
+    """The data format of the response.
+    Alternatively, the data format can be specified by setting the \"Accept\"-header.
+    You can include the parameter to return the CSV/TSV without headers: "$TEXT_CSV_WITHOUT_HEADERS_HEADER". 
+    When both are specified, this parameter takes precedence."""
 
 private const val MAYBE_DESCRIPTION = """
 A mutation can be wrapped in a maybe expression "MAYBE(\<mutation\>)"

lapis2/src/main/kotlin/org/genspectrum/lapis/controller/CsvWriter.kt

@@ -14,7 +14,7 @@ interface CsvRecord {
 @Component
 class CsvWriter {
     fun write(
-        headers: Array<String>,
+        headers: Array<String>?,
         data: List<CsvRecord>,
         delimiter: Delimiter,
     ): String {
@@ -24,7 +24,11 @@ class CsvWriter {
             CSVFormat.DEFAULT.builder()
                 .setRecordSeparator("\n")
                 .setDelimiter(delimiter.value)
-                .setHeader(*headers)
+                .also {
+                    when {
+                        headers != null -> it.setHeader(*headers)
+                    }
+                }
                 .build(),
         ).use {
             for (datum in data) {

lapis2/src/main/kotlin/org/genspectrum/lapis/controller/DataFormatParameterFilter.kt

@@ -16,11 +16,21 @@ import java.util.Enumeration
 
 private val log = KotlinLogging.logger {}
 
+const val HEADERS_ACCEPT_HEADER_PARAMETER = "headers"
+
 const val TEXT_CSV_HEADER = "text/csv"
+const val TEXT_CSV_WITHOUT_HEADERS_HEADER = "text/csv;$HEADERS_ACCEPT_HEADER_PARAMETER=false"
 const val TEXT_TSV_HEADER = "text/tab-separated-values"
 
 const val DATA_FORMAT_FILTER_ORDER = 0
 
+object DataFormat {
+    const val JSON = "JSON"
+    const val CSV = "CSV"
+    const val CSV_WITHOUT_HEADERS = "CSV-WITHOUT-HEADERS"
+    const val TSV = "TSV"
+}
+
 @Component
 @Order(DATA_FORMAT_FILTER_ORDER)
 class DataFormatParameterFilter(val objectMapper: ObjectMapper) : OncePerRequestFilter() {
@@ -40,25 +50,9 @@ class AcceptHeaderModifyingRequestWrapper(
 ) : HttpServletRequestWrapper(reReadableRequest) {
     override fun getHeader(name: String): String? {
         if (name.equals("Accept", ignoreCase = true)) {
-            when (reReadableRequest.getStringField(FORMAT_PROPERTY)?.uppercase()) {
-                "CSV" -> {
-                    log.debug { "Overwriting Accept header to $TEXT_CSV_HEADER due to format property" }
-                    return TEXT_CSV_HEADER
-                }
-
-                "TSV" -> {
-                    log.debug { "Overwriting Accept header to $TEXT_TSV_HEADER due to format property" }
-                    return TEXT_TSV_HEADER
-                }
-
-                "JSON" -> {
-                    log.debug {
-                        "Overwriting Accept header to ${MediaType.APPLICATION_JSON_VALUE} due to format property"
-                    }
-                    return MediaType.APPLICATION_JSON_VALUE
-                }
-
-                else -> {}
+            when (val overwrittenValue = findAcceptHeaderOverwriteValue()) {
+                null -> {}
+                else -> return overwriteWith(overwrittenValue)
             }
         }
 
@@ -67,28 +61,32 @@ class AcceptHeaderModifyingRequestWrapper(
 
     override fun getHeaders(name: String): Enumeration<String>? {
         if (name.equals("Accept", ignoreCase = true)) {
-            when (reReadableRequest.getStringField(FORMAT_PROPERTY)?.uppercase()) {
-                "CSV" -> {
-                    log.debug { "Overwriting Accept header to $TEXT_CSV_HEADER due to format property" }
-                    return Collections.enumeration(listOf(TEXT_CSV_HEADER))
-                }
+            when (val overwrittenValue = findAcceptHeaderOverwriteValue()) {
+                null -> {}
+                else -> return Collections.enumeration(listOf(overwriteWith(overwrittenValue)))
+            }
+        }
 
-                "TSV" -> {
-                    log.debug { "Overwriting Accept header to $TEXT_TSV_HEADER due to format property" }
-                    return Collections.enumeration(listOf(TEXT_TSV_HEADER))
-                }
+        return super.getHeaders(name)
+    }
 
-                "JSON" -> {
-                    log.debug {
-                        "Overwriting Accept header to ${MediaType.APPLICATION_JSON_VALUE} due to format property"
-                    }
-                    return Collections.enumeration(listOf(MediaType.APPLICATION_JSON_VALUE))
-                }
+    override fun getHeaderNames(): Enumeration<String> =
+        when (findAcceptHeaderOverwriteValue()) {
+            null -> super.getHeaderNames()
+            else -> Collections.enumeration(super.getHeaderNames().toList() + "Accept")
+        }
 
-                else -> {}
-            }
+    private fun findAcceptHeaderOverwriteValue() =
+        when (reReadableRequest.getStringField(FORMAT_PROPERTY)?.uppercase()) {
+            DataFormat.CSV -> TEXT_CSV_HEADER
+            DataFormat.CSV_WITHOUT_HEADERS -> TEXT_CSV_WITHOUT_HEADERS_HEADER
+            DataFormat.TSV -> TEXT_TSV_HEADER
+            DataFormat.JSON -> MediaType.APPLICATION_JSON_VALUE
+            else -> null
         }
 
-        return super.getHeaders(name)
+    private fun overwriteWith(value: String): String {
+        log.debug { "Overwriting Accept header to $value due to format property" }
+        return value
     }
 }