use crate::error::AppError;
use chrono::Utc;
use std::fs;
use std::path::Path;

const MAX_BACKUPS: usize = 10;

/// 配置导入导出相关业务逻辑
pub struct ConfigService;

impl ConfigService {
    /// 为当前 config.json 创建备份，返回备份 ID（若文件不存在则返回空字符串）。
    pub fn create_backup(config_path: &Path) -> Result<String, AppError> {
        if !config_path.exists() {
            return Ok(String::new());
        }

        let timestamp = Utc::now().format("%Y%m%d_%H%M%S");
        let backup_id = format!("backup_{timestamp}");

        let backup_dir = config_path
            .parent()
            .ok_or_else(|| AppError::Config("Invalid config path".into()))?
            .join("backups");

        fs::create_dir_all(&backup_dir).map_err(|e| AppError::io(&backup_dir, e))?;

        let backup_path = backup_dir.join(format!("{backup_id}.json"));
        let contents = fs::read(config_path).map_err(|e| AppError::io(config_path, e))?;
        fs::write(&backup_path, contents).map_err(|e| AppError::io(&backup_path, e))?;

        Self::cleanup_old_backups(&backup_dir, MAX_BACKUPS)?;

        Ok(backup_id)
    }

    fn cleanup_old_backups(backup_dir: &Path, retain: usize) -> Result<(), AppError> {
        if retain == 0 {
            return Ok(());
        }

        let entries = match fs::read_dir(backup_dir) {
            Ok(iter) => iter
                .filter_map(|entry| entry.ok())
                .filter(|entry| {
                    entry
                        .path()
                        .extension()
                        .map(|ext| ext == "json")
                        .unwrap_or(false)
                })
                .collect::<Vec<_>>(),
            Err(_) => return Ok(()),
        };

        if entries.len() <= retain {
            return Ok(());
        }

        let remove_count = entries.len().saturating_sub(retain);
        let mut sorted = entries;

        sorted.sort_by(|a, b| {
            let a_time = a.metadata().and_then(|m| m.modified()).ok();
            let b_time = b.metadata().and_then(|m| m.modified()).ok();
            a_time.cmp(&b_time)
        });

        for entry in sorted.into_iter().take(remove_count) {
            if let Err(err) = fs::remove_file(entry.path()) {
                log::warn!(
                    "Failed to remove old backup {}: {}",
                    entry.path().display(),
                    err
                );
            }
        }

        Ok(())
    }
}