package git

import (
	"context"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
)

// TestMergeFromPath verifies cross-repository (fork) merging through a
// temporary ref fetched from another local repository.
func TestMergeFromPath(t *testing.T) {
	ctx := context.Background()
	tmp := t.TempDir()

	basePath := filepath.Join(tmp, "base.git")
	if err := InitBare(ctx, basePath, "main"); err != nil {
		t.Fatalf("InitBare: %v", err)
	}

	work := filepath.Join(tmp, "work")
	if err := os.MkdirAll(work, 0o755); err != nil {
		t.Fatalf("mkdir: %v", err)
	}
	run := func(dir string, args ...string) {
		t.Helper()
		cmd := exec.CommandContext(ctx, "git", args...)
		cmd.Dir = dir
		if out, err := cmd.CombinedOutput(); err != nil {
			t.Fatalf("git %v: %v (%s)", args, err, string(out))
		}
	}

	run(work, "init", "-b", "main")
	run(work, "config", "user.name", "Alice")
	run(work, "config", "user.email", "alice@example.com")
	if err := os.WriteFile(filepath.Join(work, "file.txt"), []byte("base\n"), 0o644); err != nil {
		t.Fatalf("write: %v", err)
	}
	run(work, "add", ".")
	run(work, "commit", "-m", "base commit")
	run(work, "push", basePath, "main")

	forkPath := filepath.Join(tmp, "fork.git")
	if err := CloneBare(ctx, basePath, forkPath); err != nil {
		t.Fatalf("CloneBare: %v", err)
	}

	// Add a feature branch on the fork.
	run(work, "checkout", "-b", "feature")
	if err := os.WriteFile(filepath.Join(work, "feature.txt"), []byte("feature\n"), 0o644); err != nil {
		t.Fatalf("write: %v", err)
	}
	run(work, "add", ".")
	run(work, "commit", "-m", "add feature")
	run(work, "push", forkPath, "feature")

	hash, err := MergeFromPath(ctx, basePath, forkPath, "main", "feature", "refs/polar/tmp-merge-test", "Merge PR #1", "Alice", "alice@example.com")
	if err != nil {
		t.Fatalf("MergeFromPath: %v", err)
	}
	if hash == "" {
		t.Fatalf("expected merge commit hash")
	}

	out, err := runGit(ctx, basePath, 10_000_000_000, "ls-tree", "-r", "--name-only", "main")
	if err != nil {
		t.Fatalf("ls-tree: %v", err)
	}
	if !strings.Contains(string(out), "feature.txt") {
		t.Fatalf("expected feature.txt on merged main, got: %s", string(out))
	}

	// The temporary ref must be gone after the merge.
	if out, err := runGit(ctx, basePath, 10_000_000_000, "show-ref", "--verify", "--quiet", "refs/polar/tmp-merge-test"); err == nil {
		t.Fatalf("expected temp ref to be deleted, got %s", string(out))
	}
}