package buildstep

import (
	"os"
	"path/filepath"
	"reflect"
	"testing"
)

func pe(offset int, magic string) []byte {
	b := make([]byte, 0x100)
	copy(b, "MZ")
	b[0x3c] = byte(offset)
	copy(b[offset:], magic)
	return b
}

func TestExecutableKindTellsProgramsFromText(t *testing.T) { // issue 1577
	for _, c := range []struct {
		name string
		head []byte
		want string
	}{
		{"elf", []byte("\x7fELF\x02\x01\x01"), "ELF"},
		{"mach-o 64", []byte{0xcf, 0xfa, 0xed, 0xfe, 7, 0, 0, 1}, "Mach-O"},
		{"mach-o 32 big", []byte{0xfe, 0xed, 0xfa, 0xce, 0, 0, 0, 7}, "Mach-O"},
		{"fat mach-o", []byte{0xca, 0xfe, 0xba, 0xbe, 0, 0, 0, 2}, "Mach-O"},
		{"java class", []byte{0xca, 0xfe, 0xba, 0xbe, 0, 0, 0, 0x34}, ""},
		{"pe", pe(0x80, "PE\x00\x00"), "PE"},
		{"mz text", []byte("MZ is a text file starting with two letters"), ""},
		{"mz without a pe header", pe(0x80, "XX\x00\x00"), ""},
		{"text", []byte("package main"), ""},
		{"empty", nil, ""},
	} {
		if got := ExecutableKind(c.head); got != c.want {
			t.Errorf("%s: kind = %q, want %q", c.name, got, c.want)
		}
	}
}

func TestProgramsInNamesTheAddedAndModifiedRegularFilesThatArePrograms(t *testing.T) { // issue 1577
	dir := t.TempDir()
	write := func(name string, b []byte) {
		if err := os.MkdirAll(filepath.Dir(filepath.Join(dir, name)), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(filepath.Join(dir, name), b, 0o755); err != nil {
			t.Fatal(err)
		}
	}
	write("m/prog", []byte("\x7fELF\x02\x01"))
	write("m/notes", []byte("plain text"))
	write("m/mac", []byte{0xcf, 0xfa, 0xed, 0xfe, 7, 0, 0, 1})
	if err := os.Symlink("prog", filepath.Join(dir, "m/link")); err != nil {
		t.Fatal(err)
	}
	line := func(mode, path string) string { return ":000000 " + mode + " 0000 1111 A\x00" + path + "\x00" }
	for _, c := range []struct {
		name, raw string
		want      []Program
	}{
		{"none", "", []Program{}},
		{"a program and a text", line("100755", "m/prog") + line("100644", "m/notes"), []Program{{"m/prog", "ELF", ""}}},
		{"two programs", line("100644", "m/prog") + line("100755", "m/mac"), []Program{{"m/prog", "ELF", ""}, {"m/mac", "Mach-O", ""}}},
		{"a symlink and a submodule are not read", line("120000", "m/link") + line("160000", "m/sub"), []Program{}},
		{"a path the tree lacks", line("100644", "m/gone"), []Program{}},
	} {
		if got := programsIn(dir, c.raw); !reflect.DeepEqual(got, c.want) {
			t.Errorf("%s: programs = %v, want %v", c.name, got, c.want)
		}
	}
}