package git

import (
	"fmt"
	"time"

	gogit "github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/filemode"
	"github.com/go-git/go-git/v5/plumbing/object"
)

// GitBackend implements low-level Git object operations
type GitBackend struct {
	repo *gogit.Repository
}

// NewGitBackend creates a new GitBackend instance
func NewGitBackend(repo *gogit.Repository) *GitBackend {
	return &GitBackend{repo: repo}
}

// CreateBlob creates a new blob object from the given content
func (gb *GitBackend) CreateBlob(content []byte) (string, error) {
	store := gb.repo.Storer

	// Create a blob object
	blob := store.NewEncodedObject()
	blob.SetType(plumbing.BlobObject)
	blob.SetSize(int64(len(content)))

	writer, err := blob.Writer()
	if err != nil {
		return "", fmt.Errorf("failed to get blob writer: %w", err)
	}

	_, err = writer.Write(content)
	if err != nil {
		writer.Close()
		return "", fmt.Errorf("failed to write blob content: %w", err)
	}

	if err := writer.Close(); err != nil {
		return "", fmt.Errorf("failed to close blob writer: %w", err)
	}

	// Store the blob
	hash, err := store.SetEncodedObject(blob)
	if err != nil {
		return "", fmt.Errorf("failed to store blob: %w", err)
	}

	return hash.String(), nil
}

// TreeEntry represents an entry in a Git tree
type TreeEntry struct {
	Mode filemode.FileMode
	Name string
	Hash plumbing.Hash
}

// CreateTree creates a new tree object from the given entries
func (gb *GitBackend) CreateTree(entries []TreeEntry) (string, error) {
	store := gb.repo.Storer

	// Create a new tree object
	tree := &object.Tree{}
	treeEntries := make([]object.TreeEntry, len(entries))

	for i, entry := range entries {
		treeEntries[i] = object.TreeEntry{
			Name: entry.Name,
			Mode: entry.Mode,
			Hash: entry.Hash,
		}
	}

	tree.Entries = treeEntries

	// Encode and store the tree
	obj := store.NewEncodedObject()
	if err := tree.Encode(obj); err != nil {
		return "", fmt.Errorf("failed to encode tree: %w", err)
	}

	hash, err := store.SetEncodedObject(obj)
	if err != nil {
		return "", fmt.Errorf("failed to store tree: %w", err)
	}

	return hash.String(), nil
}

// CreateCommit creates a new commit object
func (gb *GitBackend) CreateCommit(treeHash, parentHash, message, author string) (string, error) {
	store := gb.repo.Storer

	// Parse hashes
	tree := plumbing.NewHash(treeHash)

	var parents []plumbing.Hash
	if parentHash != "" {
		parents = []plumbing.Hash{plumbing.NewHash(parentHash)}
	}

	// Create commit object
	commit := &object.Commit{
		Author: object.Signature{
			Name:  author,
			Email: "onyx@local",
			When:  time.Now(),
		},
		Committer: object.Signature{
			Name:  author,
			Email: "onyx@local",
			When:  time.Now(),
		},
		Message:  message,
		TreeHash: tree,
	}

	if len(parents) > 0 {
		commit.ParentHashes = parents
	}

	// Encode and store the commit
	obj := store.NewEncodedObject()
	if err := commit.Encode(obj); err != nil {
		return "", fmt.Errorf("failed to encode commit: %w", err)
	}

	hash, err := store.SetEncodedObject(obj)
	if err != nil {
		return "", fmt.Errorf("failed to store commit: %w", err)
	}

	return hash.String(), nil
}

// UpdateRef updates a Git reference to point to a new SHA
func (gb *GitBackend) UpdateRef(refName, sha string) error {
	hash := plumbing.NewHash(sha)
	ref := plumbing.NewHashReference(plumbing.ReferenceName(refName), hash)

	if err := gb.repo.Storer.SetReference(ref); err != nil {
		return fmt.Errorf("failed to update reference %s: %w", refName, err)
	}

	return nil
}

// GetRef retrieves the SHA that a reference points to
func (gb *GitBackend) GetRef(refName string) (string, error) {
	ref, err := gb.repo.Reference(plumbing.ReferenceName(refName), true)
	if err != nil {
		return "", fmt.Errorf("failed to get reference %s: %w", refName, err)
	}

	return ref.Hash().String(), nil
}

// GetObject retrieves a Git object by its SHA
func (gb *GitBackend) GetObject(sha string) (object.Object, error) {
	hash := plumbing.NewHash(sha)
	obj, err := gb.repo.Object(plumbing.AnyObject, hash)
	if err != nil {
		return nil, fmt.Errorf("failed to get object %s: %w", sha, err)
	}

	return obj, nil
}

// GetBlob retrieves a blob object by its SHA
func (gb *GitBackend) GetBlob(sha string) (*object.Blob, error) {
	hash := plumbing.NewHash(sha)
	blob, err := gb.repo.BlobObject(hash)
	if err != nil {
		return nil, fmt.Errorf("failed to get blob %s: %w", sha, err)
	}

	return blob, nil
}

// GetTree retrieves a tree object by its SHA
func (gb *GitBackend) GetTree(sha string) (*object.Tree, error) {
	hash := plumbing.NewHash(sha)
	tree, err := gb.repo.TreeObject(hash)
	if err != nil {
		return nil, fmt.Errorf("failed to get tree %s: %w", sha, err)
	}

	return tree, nil
}

// GetCommit retrieves a commit object by its SHA
func (gb *GitBackend) GetCommit(sha string) (*object.Commit, error) {
	hash := plumbing.NewHash(sha)
	commit, err := gb.repo.CommitObject(hash)
	if err != nil {
		return nil, fmt.Errorf("failed to get commit %s: %w", sha, err)
	}

	return commit, nil
}

// HashFromString converts a string SHA to a plumbing.Hash
func HashFromString(sha string) plumbing.Hash {
	return plumbing.NewHash(sha)
}