engine refactor

internal/weather/gfs/constants.go

@@ -1,34 +1,28 @@
 package gfs
 
-import "fmt"
+// Cross-variant constants. Per-variant geometry (latitudes, longitudes,
+// pressure levels, hour step, max hour, URL token) lives on the Variant
+// type; see variant.go.
 
-// Dataset shape: (hour, pressure_level, variable, latitude, longitude).
-// Matches the cube layout used by the reference Tawhiri implementation.
 const (
-	NumHours      = 65  // 0, 3, 6, ..., 192 hours forecast
-	NumLevels     = 47  // pressure levels
-	NumVariables  = 3   // geopotential height, U-wind, V-wind
-	NumLatitudes  = 361 // -90.0 to +90.0 inclusive in 0.5° steps
-	NumLongitudes = 720 // 0.0 to 359.5 in 0.5° steps
+	// NumVariables is the number of dataset variables: HGT, UGRD, VGRD.
+	NumVariables = 3
+	// ElementSize is the cell size in bytes (float32).
+	ElementSize = 4
 
-	HourStep   = 3
-	MaxHour    = 192
-	Resolution = 0.5
-	LatStart   = -90.0
-	LonStart   = 0.0
+	// LatStart is the first latitude in the cube (south to north).
+	LatStart = -90.0
+	// LonStart is the first longitude in the cube (0..360 east).
+	LonStart = 0.0
 
+	// Variable indices within the cube's 3rd axis.
 	VarHeight = 0
 	VarWindU  = 1
 	VarWindV  = 2
-
-	ElementSize = 4 // float32
-
-	// DatasetSize is the canonical file size: every grid cell × element size.
-	DatasetSize int64 = int64(NumHours) * int64(NumLevels) * int64(NumVariables) *
-		int64(NumLatitudes) * int64(NumLongitudes) * int64(ElementSize)
 )
 
-// LevelSet identifies which GRIB file (primary/secondary) carries a level.
+// LevelSet identifies which GRIB file (primary or secondary) carries a
+// pressure level.
 type LevelSet int
 
 const (
@@ -36,106 +30,5 @@ const (
 	LevelSetB                 // pgrb2b — secondary file
 )
 
-// Pressures lists the 47 pressure levels (hPa) in dataset index order,
-// descending from surface to top of atmosphere.
-var Pressures = [NumLevels]int{
-	1000, 975, 950, 925, 900, 875, 850, 825, 800, 775,
-	750, 725, 700, 675, 650, 625, 600, 575, 550, 525,
-	500, 475, 450, 425, 400, 375, 350, 325, 300, 275,
-	250, 225, 200, 175, 150, 125, 100, 70, 50, 30,
-	20, 10, 7, 5, 3, 2, 1,
-}
-
-// PressuresPgrb2 lists the levels carried by the primary GRIB file.
-var PressuresPgrb2 = []int{
-	10, 20, 30, 50, 70, 100, 150, 200, 250, 300, 350, 400,
-	450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 925,
-	950, 975, 1000,
-}
-
-// PressuresPgrb2b lists the levels carried by the secondary GRIB file.
-var PressuresPgrb2b = []int{
-	1, 2, 3, 5, 7, 125, 175, 225, 275, 325, 375, 425,
-	475, 525, 575, 625, 675, 725, 775, 825, 875,
-}
-
-var pressureIndex map[int]int
-var pressureLevelSet map[int]LevelSet
-
-func init() {
-	pressureIndex = make(map[int]int, NumLevels)
-	for i, p := range Pressures {
-		pressureIndex[p] = i
-	}
-	pressureLevelSet = make(map[int]LevelSet, NumLevels)
-	for _, p := range PressuresPgrb2 {
-		pressureLevelSet[p] = LevelSetA
-	}
-	for _, p := range PressuresPgrb2b {
-		pressureLevelSet[p] = LevelSetB
-	}
-}
-
-// PressureIndex returns the dataset index for a pressure level in hPa,
-// or -1 when the level is unknown.
-func PressureIndex(hPa int) int {
-	idx, ok := pressureIndex[hPa]
-	if !ok {
-		return -1
-	}
-	return idx
-}
-
-// PressureLevelSet returns the GRIB file set carrying a pressure level.
-func PressureLevelSet(hPa int) (LevelSet, bool) {
-	ls, ok := pressureLevelSet[hPa]
-	return ls, ok
-}
-
-// HourIndex returns the dataset time index for a forecast hour, or -1 when
-// the hour is outside the range or not a multiple of HourStep.
-func HourIndex(hour int) int {
-	if hour < 0 || hour > MaxHour || hour%HourStep != 0 {
-		return -1
-	}
-	return hour / HourStep
-}
-
-// Hours returns the full list of forecast hours, [0, 3, 6, ..., MaxHour].
-func Hours() []int {
-	out := make([]int, 0, NumHours)
-	for h := 0; h <= MaxHour; h += HourStep {
-		out = append(out, h)
-	}
-	return out
-}
-
-// VariableIndex maps a GRIB (category, number) pair to a dataset variable
-// index, returning -1 for parameters this dataset does not store.
-func VariableIndex(parameterCategory, parameterNumber int) int {
-	switch {
-	case parameterCategory == 3 && parameterNumber == 5:
-		return VarHeight
-	case parameterCategory == 2 && parameterNumber == 2:
-		return VarWindU
-	case parameterCategory == 2 && parameterNumber == 3:
-		return VarWindV
-	default:
-		return -1
-	}
-}
-
-// S3 URL configuration for NOAA GFS data on the public S3 mirror.
+// S3BaseURL is the public NOAA S3 mirror.
 const S3BaseURL = "https://noaa-gfs-bdp-pds.s3.amazonaws.com"
-
-// GribURL returns the S3 URL for a primary (pgrb2) GRIB file.
-func GribURL(date string, runHour, forecastStep int) string {
-	return fmt.Sprintf("%s/gfs.%s/%02d/atmos/gfs.t%02dz.pgrb2.0p50.f%03d",
-		S3BaseURL, date, runHour, runHour, forecastStep)
-}
-
-// GribURLB returns the S3 URL for a secondary (pgrb2b) GRIB file.
-func GribURLB(date string, runHour, forecastStep int) string {
-	return fmt.Sprintf("%s/gfs.%s/%02d/atmos/gfs.t%02dz.pgrb2b.0p50.f%03d",
-		S3BaseURL, date, runHour, runHour, forecastStep)
-}