package file

import (
	"fmt"
	"os"
	"strings"
)

// Write writes content to path. If startLine and endLine are both zero the
// file is written in full; otherwise the given line range is replaced.
func Write(path, content string, startLine, endLine int) (string, error) {
	if startLine == 0 && endLine == 0 {
		if err := os.WriteFile(path, []byte(content), 0644); err != nil {
			return "", fmt.Errorf("file_write: %w", err)
		}
		return fmt.Sprintf("wrote %d bytes to %s", len(content), path), nil
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return "", fmt.Errorf("file_write: %w", err)
	}
	lines := strings.Split(string(data), "\n")
	start, end := startLine, endLine
	if start < 1 {
		start = 1
	}
	if end > len(lines) {
		end = len(lines)
	}
	if start > end {
		return "", fmt.Errorf("file_write: start_line %d > end_line %d", start, end)
	}
	newLines := strings.Split(content, "\n")
	result := append(lines[:start-1], append(newLines, lines[end:]...)...)
	if err := os.WriteFile(path, []byte(strings.Join(result, "\n")), 0644); err != nil {
		return "", fmt.Errorf("file_write: %w", err)
	}
	return fmt.Sprintf("replaced lines %d-%d in %s", start, end, path), nil
}