// api/session-export.prg — Format CSV/JSON export
//
// ctx:
//   format ("csv"|"json")
//   session (JSON of session row)
//   rows    (JSON array of records)
//
// PRG generates the body string. server.js sets Content-Type/Disposition.

FUNCTION Main()
   LOCAL cFormat, hSession, aRows, hRow, hSensor, aChannels, hCh
   LOCAL cBOM, cCRLF, aLines, aCells, i, hChMap

   cFormat := Lower(ctx_get("format", "csv"))
   hSession := hb_jsonDecode(ctx_get("session", "{}"))
   aRows := hb_jsonDecode(ctx_get("rows", "[]"))

   IF ! HB_ISHASH(hSession) ; hSession := { => } ; ENDIF
   IF ! HB_ISARRAY(aRows) ; aRows := {} ; ENDIF

   IF cFormat == "json"
      AP_JSONRESPONSE({ "session" => hSession, "records" => aRows })
      RETURN NIL
   ENDIF

   // CSV with UTF-8 BOM (Excel Korean support)
   cBOM := Chr(239) + Chr(187) + Chr(191)
   cCRLF := Chr(13) + Chr(10)

   aLines := {}
   AAdd(aLines, "# Session: " + AllTrim(fn_HGet(hSession, "session_name")))
   AAdd(aLines, "# Device: "  + AllTrim(fn_HGet(hSession, "device_name")) + " (" + AllTrim(fn_HGet(hSession, "device_address")) + ")")

   // Header
   AAdd(aLines, "row,timestamp,cmd,batt_mv,batt_pct,temp_c,raa,ch0_peak,ch0_pidx,ch1_peak,ch1_pidx,ch2_peak,ch2_pidx,ch3_peak,ch3_pidx,ch4_peak,ch4_pidx,ch5_peak,ch5_pidx")

   FOR EACH hRow IN aRows
      hSensor := fn_HGet(hRow, "sensor")
      IF ! HB_ISHASH(hSensor) ; hSensor := { => } ; ENDIF

      // Build channel map (ch → {peak, peakIdx})
      hChMap := { => }
      aChannels := fn_HGet(hRow, "channels")
      IF HB_ISARRAY(aChannels)
         FOR EACH hCh IN aChannels
            IF HB_ISHASH(hCh) .AND. hb_HHasKey(hCh, "ch")
               hChMap[ AllTrim(Str(hCh["ch"])) ] := hCh
            ENDIF
         NEXT
      ENDIF

      aCells := { ;
         AllTrim(Str(fn_HGet(hRow, "row_index"))), ;
         AllTrim(fn_HGet(hRow, "timestamp")), ;
         AllTrim(fn_HGet(hRow, "command_type")), ;
         numStr(fn_HGet(hSensor, "batteryMv")), ;
         numStr(fn_HGet(hSensor, "batteryPct")), ;
         numStr(fn_HGet(hSensor, "tempC")), ;
         numStr(fn_HGet(hRow, "raa_status")) ;
      }
      FOR i := 0 TO 5
         IF hb_HHasKey(hChMap, AllTrim(Str(i)))
            AAdd(aCells, numStr(fn_HGet(hChMap[AllTrim(Str(i))], "peak")))
            AAdd(aCells, numStr(fn_HGet(hChMap[AllTrim(Str(i))], "peakIdx")))
         ELSE
            AAdd(aCells, "")
            AAdd(aCells, "")
         ENDIF
      NEXT
      AAdd(aLines, fn_Join(aCells, ","))
   NEXT

   // Use AP_RPUTS to send raw CSV string
   AP_RPUTS(cBOM + fn_Join(aLines, cCRLF))
RETURN NIL

STATIC FUNCTION fn_HGet(h, k)
   IF HB_ISHASH(h) .AND. hb_HHasKey(h, k) ; RETURN h[k] ; ENDIF
RETURN ""

STATIC FUNCTION numStr(x)
   IF x == NIL .OR. Empty(x) ; RETURN "" ; ENDIF
   IF ValType(x) == "N" ; RETURN AllTrim(Str(x)) ; ENDIF
RETURN AllTrim(x)

STATIC FUNCTION fn_Join(arr, sep)
   LOCAL out := "", i
   FOR i := 1 TO Len(arr)
      IF i > 1 ; out += sep ; ENDIF
      out += arr[i]
   NEXT
RETURN out