package git

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

// Service defines the interface for git operations
type Service interface {
	CheckConnection(url string) error
	FetchContents(url string) error
	// GetModifications returns the diffs of the top-N most-changed files (by lines
	// added/removed) modified within the last 'days' days. Files with 4 or fewer
	// changed lines are always excluded. Pass topN <= 0 to return all qualifying files.
	GetModifications(days int, topN 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 prepareSSHKey() (string, bool) {
	b, err := os.ReadFile("/root/.ssh/id_rsa")
	if err != nil {
		return "", false
	}

	// Fix literal escaped newlines and CRLF issues that cause libcrypto errors
	content := strings.ReplaceAll(string(b), "\\n", "\n")
	content = strings.ReplaceAll(content, "\r", "")

	// Ensure there is a trailing newline
	if !strings.HasSuffix(content, "\n") {
		content += "\n"
	}

	tmpPath := "/tmp/id_rsa"
	if err := os.WriteFile(tmpPath, []byte(content), 0600); err != nil {
		return "", false
	}

	return tmpPath, true
}

func (s *gitService) CheckConnection(url string) error {
	cmd := exec.Command("git", "ls-remote", url)
	if keyPath, ok := prepareSSHKey(); ok {
		cmd.Env = append(os.Environ(), fmt.Sprintf("GIT_SSH_COMMAND=ssh -i %s -o StrictHostKeyChecking=no", keyPath))
	}
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to check git connection: %w", err)
	}
	fmt.Println("Git connection checked successfully")
	return nil
}

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

	fmt.Println("Cloning repository")

	var cmd *exec.Cmd
	if keyPath, ok := prepareSSHKey(); ok {
		cmd = exec.Command("git", "clone", url, s.repoDir)
		cmd.Env = append(os.Environ(), fmt.Sprintf("GIT_SSH_COMMAND=ssh -i %s -o StrictHostKeyChecking=no", keyPath))
	} else {
		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())
	}
	fmt.Println("Repository cloned successfully")
	return nil
}

func (s *gitService) GetModifications(days int, topN 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", "-c", "core.quotePath=false", "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 {
		fmt.Printf("Processing file: %s\n", file)

		if file == "" {
			continue
		}

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

		// Skip files with "Conteúdos.md" in the path
		if strings.Contains(file, "Conteúdos.md") {
			continue
		}

		originalFile := file

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

		// Note: 'git diff' compares the beginning and end trees, so it has no native concept
		// of ignoring intermediate commits. To skip the changes made in "refactor" commits
		// without using loops, we use `git log -p` combined with `--invert-grep` to
		// natively output the diffs of only the non-refactor commits for this file.
		rangeStr := "HEAD"
		if baseCommit != "4b825dc642cb6eb9a060e54bf8d69288fbee4904" {
			rangeStr = baseCommit + "..HEAD"
		}

		cmdDiff := exec.Command("git", "-c", "core.quotePath=false", "log", "-p", "-i", "--invert-grep", "--grep=refactor", rangeStr, "--", originalFile)
		cmdDiff.Dir = s.repoDir
		diffOut, err := cmdDiff.Output()
		if err != nil {
			return nil, fmt.Errorf("failed to get diff for file %s: %w", originalFile, err)
		}

		if len(diffOut) > 0 {
			mods[file] = string(diffOut)
		}
	}

	// Count the number of changed lines (additions + deletions) per file.
	// Lines starting with '+' or '-' are changed lines; lines starting with '+++'
	// or '---' are the diff file headers and must be excluded.
	type fileScore struct {
		name  string
		score int
	}
	scores := make([]fileScore, 0, len(mods))
	for name, diff := range mods {
		count := 0
		for _, line := range strings.Split(diff, "\n") {
			if (strings.HasPrefix(line, "+") || strings.HasPrefix(line, "-")) &&
				!strings.HasPrefix(line, "++") && !strings.HasPrefix(line, "--") {
				count++
			}
		}
		// Ignore files with 4 or fewer lines changed
		if count <= 4 {
			fmt.Printf("Ignoring file %s: %d lines changed\n", name, count)
			continue
		}
		scores = append(scores, fileScore{name: name, score: count})
	}

	// Sort descending by number of changed lines
	sort.Slice(scores, func(i, j int) bool {
		return scores[i].score > scores[j].score
	})

	// Keep only the top-N entries (if topN <= 0, keep all qualifying files)
	if topN > 0 && len(scores) > topN {
		scores = scores[:topN]
	}

	result := make(map[string]string, len(scores))
	for _, fs := range scores {
		result[fs.name] = mods[fs.name]
	}

	return result, nil
}