package git

import (
	"bytes"
	"fmt"
	"os"
	"os/exec"
	"strings"
	"time"
)

// Service defines the interface for git operations
type Service interface {
	CheckConnection(url string) error
	FetchContents(url string) error
	GetModifications(days int) (map[string]string, error)
}

type gitService struct {
	repoDir string
}

// NewGitService creates a new Git service
func NewGitService() Service {
	return &gitService{
		repoDir: "./cloned_repo",
	}
}

func (s *gitService) CheckConnection(url string) error {
	cmd := exec.Command("git", "ls-remote", url)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to check git connection: %w", err)
	}
	return nil
}

func (s *gitService) FetchContents(url string) error {
	// Remove the repo directory if it already exists from a previous run
	_ = os.RemoveAll(s.repoDir)

	cmd := exec.Command("git", "clone", url, s.repoDir)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to fetch contents: %w, stderr: %s", err, stderr.String())
	}
	return nil
}

func (s *gitService) GetModifications(days int) (map[string]string, error) {
	mods := make(map[string]string)

	// Determine the commit to diff against (the latest commit *before* 'days' ago)
	since := time.Now().AddDate(0, 0, -days).Format(time.RFC3339)
	cmdBase := exec.Command("git", "rev-list", "-1", "--before", since, "HEAD")
	cmdBase.Dir = s.repoDir

	out, err := cmdBase.Output()
	baseCommit := strings.TrimSpace(string(out))

	if err != nil || baseCommit == "" {
		// If there is no commit before 'days' ago, diff against the empty tree
		// (this gets all files created in the repository's entire history if it's newer than 'days')
		baseCommit = "4b825dc642cb6eb9a060e54bf8d69288fbee4904"
	}

	// Get the list of modified files between the base commit and HEAD
	cmdFiles := exec.Command("git", "diff", "--name-only", baseCommit, "HEAD")
	cmdFiles.Dir = s.repoDir
	filesOut, err := cmdFiles.Output()
	if err != nil {
		return nil, fmt.Errorf("failed to get modified files: %w", err)
	}

	files := strings.Split(strings.TrimSpace(string(filesOut)), "\n")
	for _, file := range files {
		if file == "" {
			continue
		}

		// Filter only .md files
		if !strings.HasSuffix(file, ".md") {
			continue
		}

		// Remove first folder from file path
		file = strings.Join(strings.Split(file, "/")[1:], "/")

		// Get the specific diff for this file
		cmdDiff := exec.Command("git", "diff", baseCommit, "HEAD", "--", file)
		cmdDiff.Dir = s.repoDir
		diffOut, err := cmdDiff.Output()
		if err != nil {
			return nil, fmt.Errorf("failed to get diff for file %s: %w", file, err)
		}

		mods[file] = string(diffOut)
	}

	return mods, nil
}