package impact

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

func gitRepo(t *testing.T) string {
	t.Helper()
	if _, err := exec.LookPath("git"); err != nil {
		t.Skip("git not available")
	}
	dir := t.TempDir()
	run := func(args ...string) {
		t.Helper()
		cmd := exec.Command("git", append([]string{"-C", dir}, args...)...)
		cmd.Env = append(os.Environ(), "GIT_CONFIG_GLOBAL=/dev/null", "GIT_CONFIG_SYSTEM=/dev/null")
		if out, err := cmd.CombinedOutput(); err != nil {
			t.Fatalf("git %v: %v: %s", args, err, out)
		}
	}
	write := func(name, body string) {
		t.Helper()
		p := filepath.Join(dir, name)
		if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(p, []byte(body), 0o600); err != nil {
			t.Fatal(err)
		}
	}

	run("init", "--initial-branch=develop")
	run("config", "user.email", "test@example.net")
	run("config", "user.name", "test")
	write("keep.pp", "keep\n")
	write("gone.pp", "gone\n")
	write("old/name.pp", "some reasonably long body so rename detection fires\n")
	run("add", ".")
	run("commit", "-m", "base")

	run("checkout", "-b", "feature")
	write("added.pp", "added\n")
	write("keep.pp", "changed\n")
	if err := os.Remove(filepath.Join(dir, "gone.pp")); err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(filepath.Join(dir, "new"), 0o755); err != nil {
		t.Fatal(err)
	}
	run("mv", "old/name.pp", "new/name.pp")
	run("add", "-A")
	run("commit", "-m", "feature")
	run("checkout", "develop")
	return dir
}

func TestChangedFilesCoversAddDeleteAndRename(t *testing.T) {
	dir := gitRepo(t)
	got, err := ChangedFiles(dir, "develop", "feature")
	if err != nil {
		t.Fatalf("ChangedFiles: %v", err)
	}
	want := []string{"added.pp", "gone.pp", "keep.pp", "new/name.pp", "old/name.pp"}
	if !reflect.DeepEqual(got, want) {
		t.Errorf("ChangedFiles = %v, want %v", got, want)
	}
}

func TestCurrentBranch(t *testing.T) {
	dir := gitRepo(t)
	got, err := CurrentBranch(dir)
	if err != nil {
		t.Fatalf("CurrentBranch: %v", err)
	}
	if got != "develop" {
		t.Errorf("CurrentBranch = %q, want develop", got)
	}
}

func TestChangedFilesReportsGitErrors(t *testing.T) {
	dir := gitRepo(t)
	if _, err := ChangedFiles(dir, "develop", "no-such-branch"); err == nil {
		t.Fatal("expected an error for a missing ref")
	}
}