// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package asm

import (
	"bytes"
	"debug/elf"
	"encoding/binary"
	"testing"

	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
)

// TestELFRISCVObjectDataRelocation checks that a symbol-valued DATA field
// ("DATA s+0(SB)/8, $other(SB)") reaches the RISC-V ELF object as a
// .rela.data entry: an R_RISCV_64 (R_RISCV_32 for a width-4 field) at the
// field's offset within .data, against the named symbol, external targets
// included.
func TestELFRISCVObjectDataRelocation(t *testing.T) {
	f, errs := parser.Parse("t_riscv64.s", `#include "textflag.h"
TEXT ·Keep(SB), NOSPLIT, $0-0
	RET
GLOBL holder(SB), NOPTR, $32
DATA holder+0(SB)/8, $·Keep+5(SB)
DATA holder+8(SB)/8, $holder(SB)
DATA holder+16(SB)/8, $extvar(SB)
DATA holder+24(SB)/4, $Keep(SB)
`)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	obj, err := img.ELFRISCVObject()
	if err != nil {
		t.Fatalf("ELFRISCVObject: %v", err)
	}
	checkELFSectionAccounting(t, obj)
	ef, err := elf.NewFile(bytes.NewReader(obj))
	if err != nil {
		t.Fatalf("parse emitted object: %v", err)
	}
	defer ef.Close()
	relaData := ef.Section(".rela.data")
	if relaData == nil {
		t.Fatal("missing .rela.data section")
	}
	if relaData.Type != elf.SHT_RELA {
		t.Errorf(".rela.data type = %v, want SHT_RELA", relaData.Type)
	}
	if relaData.Link == 0 || ef.Sections[relaData.Link].Name != ".symtab" {
		t.Errorf(".rela.data sh_link = %d, want the .symtab index", relaData.Link)
	}
	if ef.Sections[relaData.Info].Name != ".data" {
		t.Errorf(".rela.data sh_info = %d, want the .data index", relaData.Info)
	}
	relas, err := relaData.Data()
	if err != nil {
		t.Fatal(err)
	}
	var got []struct {
		off    uint64
		sym    uint32
		typ    uint32
		addend int64
	}
	for i := 0; i+24 <= len(relas); i += 24 {
		got = append(got, struct {
			off    uint64
			sym    uint32
			typ    uint32
			addend int64
		}{
			off: binary.LittleEndian.Uint64(relas[i:]),
			// r_info packs the type in the low dword and the symbol index
			// in the high dword.
			typ:    binary.LittleEndian.Uint32(relas[i+8:]),
			sym:    binary.LittleEndian.Uint32(relas[i+12:]),
			addend: int64(binary.LittleEndian.Uint64(relas[i+16:])),
		})
	}
	// debug/elf hides the table's null entry, so raw index s names syms[s-1].
	syms, err := ef.Symbols()
	if err != nil {
		t.Fatal(err)
	}
	name := func(idx uint32) string {
		if idx >= 1 && int(idx) <= len(syms) {
			return syms[idx-1].Name
		}
		return ""
	}
	// The offsets are data-section-relative: the field's DATA offset plus
	// the symbol's position in .data (the layout aligns each symbol to 16).
	base := uint64(0)
	for _, d := range img.DataSyms {
		if d.Name == "holder" {
			base = uint64(d.Offset)
		}
	}
	want := []struct {
		off    uint64
		typ    uint32
		addend int64
		target string
	}{
		{off: base + 0, typ: uint32(elf.R_RISCV_64), addend: 5, target: "Keep"},
		{off: base + 8, typ: uint32(elf.R_RISCV_64), addend: 0, target: "holder"},
		{off: base + 16, typ: uint32(elf.R_RISCV_64), addend: 0, target: "extvar"},
		{off: base + 24, typ: uint32(elf.R_RISCV_32), addend: 0, target: "Keep"},
	}
	if len(got) != len(want) {
		t.Fatalf(".rela.data entries = %d, want %d", len(got), len(want))
	}
	for i, w := range want {
		g := got[i]
		if g.off != w.off || g.typ != w.typ || g.addend != w.addend {
			t.Errorf("entry %d = {off %d typ %d addend %d}, want {off %d typ %d addend %d}",
				i, g.off, g.typ, g.addend, w.off, w.typ, w.addend)
		}
		if n := name(g.sym); n != w.target {
			t.Errorf("entry %d names %q, want %q", i, n, w.target)
		}
	}
}