package loader

import (
	"debug/elf"
	_ "embed"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

var (
	//go:embed tests/noop.so
	soNoop []byte
)

func TestLoadProgram_Noop(t *testing.T) {
	loader, err := NewLoaderFromBytes(soNoop)
	require.NoError(t, err)

	err = loader.parse()
	require.NoError(t, err)

	assert.Equal(t, elf.Header64{
		Ident: [16]byte{
			0x7f, 0x45, 0x4c, 0x46,
			0x02, 0x01, 0x01, 0x00,
			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		},
		Type:      uint16(elf.ET_DYN),
		Machine:   uint16(elf.EM_BPF),
		Version:   uint32(elf.EV_CURRENT),
		Entry:     4096,
		Phoff:     64,
		Shoff:     8792,
		Flags:     0,
		Ehsize:    64,
		Phentsize: 56,
		Phnum:     7,
		Shentsize: 64,
		Shnum:     13,
		Shstrndx:  11,
	}, loader.eh)

	assert.Equal(t, elf.Prog64{
		Type:   uint32(elf.PT_LOAD),
		Flags:  06,
		Off:    8192,
		Vaddr:  8192,
		Paddr:  8192,
		Filesz: 208,
		Memsz:  208,
		Align:  4096,
	}, loader.phLoad)

	assert.Equal(t, elf.Section64{
		Name:      82,
		Type:      uint32(elf.SHT_STRTAB),
		Flags:     0,
		Addr:      0,
		Off:       8648,
		Size:      100,
		Addralign: 1,
	}, loader.shShstrtab)

	assert.Equal(t, &elf.Section64{
		Name:      50,
		Type:      uint32(elf.SHT_PROGBITS),
		Flags:     6,
		Addr:      4096,
		Off:       4096,
		Size:      96,
		Addralign: 8,
	}, loader.shText)

	assert.Equal(t, &elf.Section64{
		Name:      74,
		Type:      uint32(elf.SHT_SYMTAB),
		Flags:     0,
		Addr:      0,
		Off:       8504,
		Size:      144,
		Link:      12,
		Info:      3,
		Addralign: 8,
		Entsize:   24,
	}, loader.shSymtab)

	assert.Equal(t, &elf.Section64{
		Name:      92,
		Type:      uint32(elf.SHT_STRTAB),
		Flags:     0,
		Addr:      0,
		Off:       8748,
		Size:      39,
		Link:      0,
		Info:      0,
		Addralign: 1,
		Entsize:   0,
	}, loader.shStrtab)

	assert.Equal(t, &elf.Section64{
		Name:      25,
		Type:      uint32(elf.SHT_STRTAB),
		Flags:     uint64(elf.DF_SYMBOLIC),
		Addr:      624,
		Off:       624,
		Size:      23,
		Link:      0,
		Info:      0,
		Addralign: 1,
		Entsize:   0,
	}, loader.shDynstr)

	assert.Equal(t, &elf.Prog64{
		Type:   uint32(elf.PT_DYNAMIC),
		Flags:  uint32(elf.DF_TEXTREL | elf.DF_SYMBOLIC),
		Off:    8192,
		Vaddr:  8192,
		Paddr:  8192,
		Filesz: 208,
		Memsz:  208,
		Align:  8,
	}, loader.phDynamic)

	assert.Equal(t, &elf.Section64{
		Name:      56,
		Type:      uint32(elf.SHT_DYNAMIC),
		Flags:     3,
		Addr:      8192,
		Off:       8192,
		Size:      208,
		Link:      4,
		Info:      0,
		Addralign: 8,
		Entsize:   16,
	}, loader.shDynamic)

	var dynamic [DT_NUM]uint64
	dynamic[elf.DT_HASH] = 0x248
	dynamic[elf.DT_STRTAB] = 0x270
	dynamic[elf.DT_SYMTAB] = 0x1c8
	dynamic[elf.DT_STRSZ] = 0x17
	dynamic[elf.DT_SYMENT] = 0x18
	dynamic[elf.DT_REL] = 0x288
	dynamic[elf.DT_RELSZ] = 0x30
	dynamic[elf.DT_RELENT] = 0x10
	dynamic[elf.DT_FLAGS] = 0x04

	assert.Equal(t, dynamic, loader.dynamic)

	err = loader.copy()
	require.NoError(t, err)

	assert.Equal(t, []addrRange{
		{
			// .rodata
			min: 0x2b8,
			max: 0x2c3,
		},
	}, loader.rodatas)

	assert.Equal(t, addrRange{
		min: 0x1000,
		max: 0x1060,
	}, loader.text)

	assertZeroBytes(t, loader.program[:loader.rodatas[0].min])
	assert.Equal(t,
		soNoop[loader.rodatas[0].min:loader.rodatas[0].max],
		loader.program[loader.rodatas[0].min:loader.rodatas[0].max])
	assertZeroBytes(t, loader.program[loader.rodatas[0].max:loader.text.min])
	assert.Equal(t,
		soNoop[loader.text.min:loader.text.max],
		loader.program[loader.text.min:loader.text.max])
	assertZeroBytes(t, loader.program[loader.text.max:])
}

func assertZeroBytes(t *testing.T, b []byte) {
	if !isZeroBytes(b) {
		t.Fatal("Should be zero")
	}
}

func isZeroBytes(b []byte) bool {
	for _, v := range b {
		if v != 0x00 {
			return false
		}
	}
	return true
}