1 files changed, 265 insertions, 0 deletions
diff --git a/internal/git/diff.go b/internal/git/diff.go
new file mode 100644
index 000000000..d87956f01
--- /dev/null
+++ b/internal/git/diff.go
@@ -0,0 +1,265 @@
+package git
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/kujtimiihoxha/termai/internal/config"
+)
+
+type DiffStats struct {
+	Additions int
+	Removals  int
+}
+
+func GenerateGitDiff(filePath string, contentBefore string, contentAfter string) (string, error) {
+	tempDir, err := os.MkdirTemp("", "git-diff-temp")
+	if err != nil {
+		return "", fmt.Errorf("failed to create temp dir: %w", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	repo, err := git.PlainInit(tempDir, false)
+	if err != nil {
+		return "", fmt.Errorf("failed to initialize git repo: %w", err)
+	}
+
+	wt, err := repo.Worktree()
+	if err != nil {
+		return "", fmt.Errorf("failed to get worktree: %w", err)
+	}
+
+	fullPath := filepath.Join(tempDir, filePath)
+	if err = os.MkdirAll(filepath.Dir(fullPath), 0o755); err != nil {
+		return "", fmt.Errorf("failed to create directories: %w", err)
+	}
+	if err = os.WriteFile(fullPath, []byte(contentBefore), 0o644); err != nil {
+		return "", fmt.Errorf("failed to write 'before' content: %w", err)
+	}
+
+	_, err = wt.Add(filePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to add file to git: %w", err)
+	}
+
+	beforeCommit, err := wt.Commit("Before", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to commit 'before' version: %w", err)
+	}
+
+	if err = os.WriteFile(fullPath, []byte(contentAfter), 0o644); err != nil {
+		return "", fmt.Errorf("failed to write 'after' content: %w", err)
+	}
+
+	_, err = wt.Add(filePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to add updated file to git: %w", err)
+	}
+
+	afterCommit, err := wt.Commit("After", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to commit 'after' version: %w", err)
+	}
+
+	beforeCommitObj, err := repo.CommitObject(beforeCommit)
+	if err != nil {
+		return "", fmt.Errorf("failed to get 'before' commit: %w", err)
+	}
+
+	afterCommitObj, err := repo.CommitObject(afterCommit)
+	if err != nil {
+		return "", fmt.Errorf("failed to get 'after' commit: %w", err)
+	}
+
+	patch, err := beforeCommitObj.Patch(afterCommitObj)
+	if err != nil {
+		return "", fmt.Errorf("failed to generate patch: %w", err)
+	}
+
+	return patch.String(), nil
+}
+
+func GenerateGitDiffWithStats(filePath string, contentBefore string, contentAfter string) (string, DiffStats, error) {
+	tempDir, err := os.MkdirTemp("", "git-diff-temp")
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to create temp dir: %w", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	repo, err := git.PlainInit(tempDir, false)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to initialize git repo: %w", err)
+	}
+
+	wt, err := repo.Worktree()
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to get worktree: %w", err)
+	}
+
+	fullPath := filepath.Join(tempDir, filePath)
+	if err = os.MkdirAll(filepath.Dir(fullPath), 0o755); err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to create directories: %w", err)
+	}
+	if err = os.WriteFile(fullPath, []byte(contentBefore), 0o644); err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to write 'before' content: %w", err)
+	}
+
+	_, err = wt.Add(filePath)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to add file to git: %w", err)
+	}
+
+	beforeCommit, err := wt.Commit("Before", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to commit 'before' version: %w", err)
+	}
+
+	if err = os.WriteFile(fullPath, []byte(contentAfter), 0o644); err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to write 'after' content: %w", err)
+	}
+
+	_, err = wt.Add(filePath)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to add updated file to git: %w", err)
+	}
+
+	afterCommit, err := wt.Commit("After", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to commit 'after' version: %w", err)
+	}
+
+	beforeCommitObj, err := repo.CommitObject(beforeCommit)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to get 'before' commit: %w", err)
+	}
+
+	afterCommitObj, err := repo.CommitObject(afterCommit)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to get 'after' commit: %w", err)
+	}
+
+	patch, err := beforeCommitObj.Patch(afterCommitObj)
+	if err != nil {
+		return "", DiffStats{}, fmt.Errorf("failed to generate patch: %w", err)
+	}
+
+	stats := DiffStats{}
+	for _, fileStat := range patch.Stats() {
+		stats.Additions += fileStat.Addition
+		stats.Removals += fileStat.Deletion
+	}
+
+	return patch.String(), stats, nil
+}
+
+func FormatDiff(diffText string, width int) (string, error) {
+	if isSplitDiffsAvailable() {
+		return formatWithSplitDiffs(diffText, width)
+	}
+
+	return formatSimple(diffText), nil
+}
+
+func isSplitDiffsAvailable() bool {
+	_, err := exec.LookPath("node")
+	return err == nil
+}
+
+func formatWithSplitDiffs(diffText string, width int) (string, error) {
+	var cmd *exec.Cmd
+
+	appCfg := config.Get()
+	appWd := config.WorkingDirectory()
+	script := filepath.Join(
+		appWd,
+		appCfg.Data.Directory,
+		"diff",
+		"index.mjs",
+	)
+
+	cmd = exec.Command("node", script, "--color")
+
+	cmd.Env = append(os.Environ(), fmt.Sprintf("COLUMNS=%d", width))
+
+	cmd.Stdin = strings.NewReader(diffText)
+
+	var out bytes.Buffer
+	cmd.Stdout = &out
+
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	if err != nil {
+		return "", fmt.Errorf("git-split-diffs error: %v, stderr: %s", err, stderr.String())
+	}
+
+	return out.String(), nil
+}
+
+func formatSimple(diffText string) string {
+	lines := strings.Split(diffText, "\n")
+	var result strings.Builder
+
+	for _, line := range lines {
+		if len(line) == 0 {
+			result.WriteString("\n")
+			continue
+		}
+
+		switch line[0] {
+		case '+':
+			result.WriteString("\033[32m" + line + "\033[0m\n")
+		case '-':
+			result.WriteString("\033[31m" + line + "\033[0m\n")
+		case '@':
+			result.WriteString("\033[36m" + line + "\033[0m\n")
+		case 'd':
+			if strings.HasPrefix(line, "diff --git") {
+				result.WriteString("\033[1m" + line + "\033[0m\n")
+			} else {
+				result.WriteString(line + "\n")
+			}
+		default:
+			result.WriteString(line + "\n")
+		}
+	}
+
+	if !strings.HasSuffix(diffText, "\n") {
+		output := result.String()
+		return output[:len(output)-1]
+	}
+
+	return result.String()
+}