package downloader

import (
	"testing"
)

const sampleIdx = `1:0:d=2024010100:HGT:1000 mb:0 hour fcst:
2:289012:d=2024010100:HGT:975 mb:0 hour fcst:
3:541876:d=2024010100:TMP:1000 mb:0 hour fcst:
4:789012:d=2024010100:UGRD:1000 mb:0 hour fcst:
5:1045678:d=2024010100:VGRD:1000 mb:0 hour fcst:
6:1298765:d=2024010100:UGRD:975 mb:0 hour fcst:
7:1567890:d=2024010100:UGRD:2 m above ground:0 hour fcst:
8:1812345:d=2024010100:VGRD:975 mb:0 hour fcst:
9:2098765:d=2024010100:HGT:500 mb:3 hour fcst:
`

func TestParseIdx(t *testing.T) {
	entries := ParseIdx([]byte(sampleIdx))
	if len(entries) != 9 {
		t.Fatalf("expected 9 entries, got %d", len(entries))
	}

	// Check first entry
	e := entries[0]
	if e.Index != 1 || e.Offset != 0 || e.Variable != "HGT" || e.LevelMB != 1000 || e.Hour != 0 {
		t.Errorf("entry 0: got %+v", e)
	}
	if e.EndOffset != 289012 {
		t.Errorf("entry 0 EndOffset: got %d, want 289012", e.EndOffset)
	}

	// Check "2 m above ground" is not a pressure level
	e = entries[6] // UGRD at "2 m above ground"
	if e.LevelMB != 0 {
		t.Errorf("non-pressure level should have LevelMB=0, got %d", e.LevelMB)
	}

	// Last entry should have EndOffset = -1
	last := entries[len(entries)-1]
	if last.EndOffset != -1 {
		t.Errorf("last entry EndOffset: got %d, want -1", last.EndOffset)
	}
}

func TestFilterIdx(t *testing.T) {
	entries := ParseIdx([]byte(sampleIdx))
	filtered := FilterIdx(entries, neededVariables)

	// Should include HGT/UGRD/VGRD at pressure levels, exclude TMP and "above ground"
	// And exclude last entry (no EndOffset)
	for _, e := range filtered {
		if !neededVariables[e.Variable] {
			t.Errorf("unexpected variable %s", e.Variable)
		}
		if e.LevelMB <= 0 {
			t.Errorf("non-pressure level included: %+v", e)
		}
		if e.Length() <= 0 {
			t.Errorf("entry with unknown length included: %+v", e)
		}
	}

	// Count expected: HGT@1000, HGT@975, UGRD@1000, VGRD@1000, UGRD@975, VGRD@975 = 6
	// But HGT@500 at 3hr fcst is the last entry (no EndOffset), so excluded
	if len(filtered) != 6 {
		t.Errorf("expected 6 filtered entries, got %d", len(filtered))
		for _, e := range filtered {
			t.Logf("  %s %d mb (offset %d, len %d)", e.Variable, e.LevelMB, e.Offset, e.Length())
		}
	}
}

func TestParseLevelMB(t *testing.T) {
	tests := []struct {
		input string
		want  int
	}{
		{"1000 mb", 1000},
		{"975 mb", 975},
		{"1 mb", 1},
		{"2 m above ground", 0},
		{"surface", 0},
		{"tropopause", 0},
	}
	for _, tt := range tests {
		got := parseLevelMB(tt.input)
		if got != tt.want {
			t.Errorf("parseLevelMB(%q) = %d, want %d", tt.input, got, tt.want)
		}
	}
}

func TestParseHour(t *testing.T) {
	tests := []struct {
		input string
		want  int
	}{
		{"0 hour fcst", 0},
		{"3 hour fcst", 3},
		{"192 hour fcst", 192},
		{"anl", 0},
	}
	for _, tt := range tests {
		got := parseHour(tt.input)
		if got != tt.want {
			t.Errorf("parseHour(%q) = %d, want %d", tt.input, got, tt.want)
		}
	}
}