package git

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/config"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/go-git/go-git/v5/plumbing/transport/http"
)

// GitOperations handles git operations on repositories
type GitOperations struct {
	cacheDir string
}

// NewGitOperations creates a new GitOperations instance
func NewGitOperations(cacheDir string) *GitOperations {
	return &GitOperations{
		cacheDir: cacheDir,
	}
}

// getRepoPath returns the local path for a repository
func (g *GitOperations) getRepoPath(repoFullName string) string {
	return filepath.Join(g.cacheDir, repoFullName)
}

// CloneOrOpen clones a repository if it doesn't exist, or opens it if it does
func (g *GitOperations) CloneOrOpen(ctx context.Context, repoFullName, cloneURL, accessToken string) (*git.Repository, error) {
	repoPath := g.getRepoPath(repoFullName)

	// Check if repository already exists
	if _, err := os.Stat(filepath.Join(repoPath, ".git")); err == nil {
		// Repository exists, open it
		repo, err := git.PlainOpen(repoPath)
		if err != nil {
			return nil, fmt.Errorf("failed to open repository: %w", err)
		}

		// Fetch latest changes
		err = repo.Fetch(&git.FetchOptions{
			Auth: &http.BasicAuth{
				Username: "oauth2",
				Password: accessToken,
			},
			Force: true,
		})
		if err != nil && err != git.NoErrAlreadyUpToDate {
			return nil, fmt.Errorf("failed to fetch: %w", err)
		}

		return repo, nil
	}

	// Repository doesn't exist, clone it
	if err := os.MkdirAll(filepath.Dir(repoPath), 0755); err != nil {
		return nil, fmt.Errorf("failed to create cache directory: %w", err)
	}

	repo, err := git.PlainClone(repoPath, false, &git.CloneOptions{
		URL: cloneURL,
		Auth: &http.BasicAuth{
			Username: "oauth2",
			Password: accessToken,
		},
		Progress: nil,
	})
	if err != nil {
		return nil, fmt.Errorf("failed to clone repository: %w", err)
	}

	return repo, nil
}

// CreateBranch creates a new branch from the default branch
func (g *GitOperations) CreateBranch(repo *git.Repository, branchName, baseBranch string) error {
	// Get the base branch reference
	baseBranchRef := plumbing.NewRemoteReferenceName("origin", baseBranch)
	baseRef, err := repo.Reference(baseBranchRef, true)
	if err != nil {
		return fmt.Errorf("failed to get base branch reference: %w", err)
	}

	// Create new branch reference
	newBranchRef := plumbing.NewBranchReferenceName(branchName)
	ref := plumbing.NewHashReference(newBranchRef, baseRef.Hash())

	// Store the reference
	if err := repo.Storer.SetReference(ref); err != nil {
		return fmt.Errorf("failed to create branch reference: %w", err)
	}

	// Checkout the new branch
	w, err := repo.Worktree()
	if err != nil {
		return fmt.Errorf("failed to get worktree: %w", err)
	}

	if err := w.Checkout(&git.CheckoutOptions{
		Branch: newBranchRef,
		Force:  true,
	}); err != nil {
		return fmt.Errorf("failed to checkout branch: %w", err)
	}

	return nil
}

// CheckoutBranch checks out an existing branch
func (g *GitOperations) CheckoutBranch(repo *git.Repository, branchName string) error {
	w, err := repo.Worktree()
	if err != nil {
		return fmt.Errorf("failed to get worktree: %w", err)
	}

	branchRef := plumbing.NewBranchReferenceName(branchName)
	if err := w.Checkout(&git.CheckoutOptions{
		Branch: branchRef,
		Force:  true,
	}); err != nil {
		return fmt.Errorf("failed to checkout branch: %w", err)
	}

	return nil
}

// WriteFile writes content to a file in the repository
func (g *GitOperations) WriteFile(repoFullName, filePath, content string) error {
	repoPath := g.getRepoPath(repoFullName)
	fullPath := filepath.Join(repoPath, filePath)

	// Create directory if it doesn't exist
	if err := os.MkdirAll(filepath.Dir(fullPath), 0755); err != nil {
		return fmt.Errorf("failed to create directory: %w", err)
	}

	// Write file
	if err := os.WriteFile(fullPath, []byte(content), 0644); err != nil {
		return fmt.Errorf("failed to write file: %w", err)
	}

	return nil
}

// CommitChanges commits all changes with a message
func (g *GitOperations) CommitChanges(repo *git.Repository, message string, filePaths []string) (string, error) {
	w, err := repo.Worktree()
	if err != nil {
		return "", fmt.Errorf("failed to get worktree: %w", err)
	}

	// Add files
	for _, filePath := range filePaths {
		if _, err := w.Add(filePath); err != nil {
			return "", fmt.Errorf("failed to add file %s: %w", filePath, err)
		}
	}

	// Commit
	commit, err := w.Commit(message, &git.CommitOptions{
		Author: &object.Signature{
			Name:  "MarkEdit",
			Email: "markedit@users.noreply.github.com",
			When:  time.Now(),
		},
	})
	if err != nil {
		return "", fmt.Errorf("failed to commit: %w", err)
	}

	return commit.String(), nil
}

// Push pushes the current branch to remote
func (g *GitOperations) Push(repo *git.Repository, branchName, accessToken string) error {
	// Get the branch reference
	branchRef := plumbing.NewBranchReferenceName(branchName)

	// Push the branch
	err := repo.Push(&git.PushOptions{
		RemoteName: "origin",
		RefSpecs: []config.RefSpec{
			config.RefSpec(branchRef + ":" + branchRef),
		},
		Auth: &http.BasicAuth{
			Username: "oauth2",
			Password: accessToken,
		},
		Force: false,
	})

	if err != nil && err != git.NoErrAlreadyUpToDate {
		return fmt.Errorf("failed to push: %w", err)
	}

	return nil
}

// DeleteLocalBranch deletes a local branch
func (g *GitOperations) DeleteLocalBranch(repo *git.Repository, branchName string) error {
	branchRef := plumbing.NewBranchReferenceName(branchName)

	if err := repo.Storer.RemoveReference(branchRef); err != nil {
		return fmt.Errorf("failed to delete branch: %w", err)
	}

	return nil
}

// GetCurrentBranch returns the name of the current branch
func (g *GitOperations) GetCurrentBranch(repo *git.Repository) (string, error) {
	head, err := repo.Head()
	if err != nil {
		return "", fmt.Errorf("failed to get HEAD: %w", err)
	}

	if !head.Name().IsBranch() {
		return "", fmt.Errorf("HEAD is not a branch")
	}

	return head.Name().Short(), nil
}

// DeleteFile removes a file from the repository worktree
func (g *GitOperations) DeleteFile(repoFullName, filePath string) error {
	repoPath := g.getRepoPath(repoFullName)
	fullPath := filepath.Join(repoPath, filePath)

	if err := os.Remove(fullPath); err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("failed to delete file: %w", err)
	}

	return nil
}