// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package worker

import (
	"io/ioutil"
	"path"
	"testing"
	"time"

	"github.com/go-git/go-billy/v5/memfs"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/go-git/go-git/v5/storage/memory"
	"golang.org/x/tools/txtar"
	"golang.org/x/vuln/internal/derrors"
)

// readTxtarRepo converts a txtar file to a single-commit
// repo.
func readTxtarRepo(filename string) (_ *git.Repository, err error) {
	defer derrors.Wrap(&err, "readTxtarRepo(%q)", filename)

	mfs := memfs.New()
	ar, err := txtar.ParseFile(filename)
	if err != nil {
		return nil, err
	}
	for _, f := range ar.Files {
		file, err := mfs.Create(f.Name)
		if err != nil {
			return nil, err
		}
		if _, err := file.Write(f.Data); err != nil {
			return nil, err
		}
		if err := file.Close(); err != nil {
			return nil, err
		}
	}

	repo, err := git.Init(memory.NewStorage(), mfs)
	if err != nil {
		return nil, err
	}
	wt, err := repo.Worktree()
	if err != nil {
		return nil, err
	}
	for _, f := range ar.Files {
		if _, err := wt.Add(f.Name); err != nil {
			return nil, err
		}
	}
	_, err = wt.Commit("", &git.CommitOptions{All: true, Author: &object.Signature{
		Name:  "Joe Random",
		Email: "joe@example.com",
		When:  time.Now(),
	}})
	if err != nil {
		return nil, err
	}
	return repo, nil
}

// headCommit returns the commit at the repo HEAD.
func headCommit(t *testing.T, repo *git.Repository) *object.Commit {
	h, err := headHash(repo)
	if err != nil {
		t.Fatal(err)
	}
	commit, err := repo.CommitObject(h)
	if err != nil {
		t.Fatal(err)
	}
	return commit
}

// headHash returns the hash of the repo's HEAD.
func headHash(repo *git.Repository) (plumbing.Hash, error) {
	ref, err := repo.Reference(plumbing.HEAD, true)
	if err != nil {
		return plumbing.ZeroHash, err
	}
	return ref.Hash(), nil
}

// findBlob returns the blob at filename in repo.
// It fail the test if it doesn't exist.
func findBlob(t *testing.T, repo *git.Repository, filename string) *object.Blob {
	c := headCommit(t, repo)
	tree, err := repo.TreeObject(c.TreeHash)
	if err != nil {
		t.Fatal(err)
	}
	e := findEntry(t, repo, tree, filename)
	blob, err := repo.BlobObject(e.Hash)
	if err != nil {
		t.Fatal(err)
	}
	return blob
}

// readBlob reads the contents of a blob.
func readBlob(t *testing.T, blob *object.Blob) []byte {
	r, err := blob.Reader()
	if err != nil {
		t.Fatal(err)
	}
	data, err := ioutil.ReadAll(r)
	if err != nil {
		t.Fatal(err)
	}
	return data
}

// findEntry returns the TreeEntry at filename. It fails the test if
// it doesn't exist.
func findEntry(t *testing.T, repo *git.Repository, tree *object.Tree, filename string) object.TreeEntry {
	dir, base := path.Split(filename)
	if dir != "" {
		te := findEntry(t, repo, tree, dir[:len(dir)-1])
		var err error
		tree, err = repo.TreeObject(te.Hash)
		if err != nil {
			t.Fatal(err)
		}
	}
	for _, e := range tree.Entries {
		if e.Name == base {
			return e
		}
	}
	t.Fatalf("could not find %q in repo", filename)
	return object.TreeEntry{}
}