// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package io

import (
	"encoding/binary"
	"os"
	"path/filepath"
	"testing"

	"sourcedock.dev/petrbalvin/tensor/internal/core"
)

// The binary-table reader resolves header keywords through a map whose
// documented rule is first-occurrence-wins, the behaviour the previous
// linear scan answered. A hostile header may repeat a structural card
// with a different value: this pin fixes that the reader follows the
// first value of each repeated card.
func TestLoadFITSTableRepeatedKeywordsFirstWins(t *testing.T) {
	body := make([]byte, 16)
	for r := range 2 {
		binary.BigEndian.PutUint64(body[r*8:], uint64(1000+r))
	}
	cards := []string{
		fitsStringCardRaw("XTENSION", "BINTABLE"),
		fitsIntCard("BITPIX", 8),
		fitsIntCard("NAXIS", 2),
		fitsIntCard("NAXIS1", 8),
		fitsIntCard("NAXIS2", 2),
		fitsIntCard("NAXIS2", 99),
		fitsIntCard("PCOUNT", 0),
		fitsIntCard("GCOUNT", 1),
		fitsIntCard("TFIELDS", 1),
		fitsIntCard("TFIELDS", 5),
		fitsStringCardRaw("TTYPE1", "COL1"),
		fitsStringCardRaw("TFORM1", "K"),
		fitsStringCardRaw("TFORM1", "D"),
		fitsEndCard(),
	}
	out := fitsAppendCards(nil, []string{
		fitsBoolCard("SIMPLE", true),
		fitsIntCard("BITPIX", 8),
		fitsIntCard("NAXIS", 0),
		fitsBoolCard("EXTEND", true),
		fitsEndCard(),
	})
	out = fitsAppendCards(out, cards)
	out = append(out, body...)
	out = fitsAppendZeroPad(out)
	path := filepath.Join(t.TempDir(), "repeated.fits")
	if err := os.WriteFile(path, out, 0o644); err != nil {
		t.Fatal(err)
	}
	table, err := LoadFITSTable(path)
	if err != nil {
		t.Fatalf("LoadFITSTable: %v", err)
	}
	if table.Rows != 2 {
		t.Fatalf("rows = %d, want 2 from the first NAXIS2", table.Rows)
	}
	if len(table.Columns) != 1 {
		t.Fatalf("columns = %d, want 1 from the first TFIELDS", len(table.Columns))
	}
	col := table.Columns[0]
	if col == nil {
		t.Fatal("the first column came back nil; the repeated TFORM1 must still decode the first form")
	}
	if len(table.Text) > 0 && table.Text[0] != nil {
		t.Fatalf("column text = %v, want nil for a K column decoded from the first TFORM1", table.Text[0])
	}
	if col.Dtype() != core.Int {
		t.Fatalf("column dtype = %s, want Int from the first TFORM1 (K)", col.Dtype())
	}
	for i, want := range []int64{1000, 1001} {
		if got := col.RawInts()[i]; got != want {
			t.Fatalf("value %d = %d, want %d", i, got, want)
		}
	}
}