use chrono::Local;
use serde::{Deserialize, Serialize};
use std::fs::{self, File, OpenOptions};
use std::io::{BufRead, BufReader, Write};
use std::path::PathBuf;

/// 日志级别
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum LogLevel {
    Debug,
    Info,
    Warn,
    Error,
}

/// 单条日志记录
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogEntry {
    pub timestamp: String,
    pub level: LogLevel,
    pub module: String,
    pub message: String,
}

/// 日志文件信息
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogInfo {
    pub log_dir: String,
    pub log_files: Vec<String>,
    pub total_size_bytes: u64,
    pub max_file_size_bytes: u64,
    pub max_files: u32,
}

/// 日志管理器 —— 负责文件轮转、写入、查询
pub struct LogManager {
    log_dir: PathBuf,
    max_file_size: u64,
    max_files: u32,
    base_name: String,
}

impl LogManager {
    pub fn new(log_dir: PathBuf) -> Self {
        fs::create_dir_all(&log_dir).ok();
        Self {
            log_dir,
            max_file_size: 5 * 1024 * 1024,
            max_files: 5,
            base_name: "thing".to_string(),
        }
    }

    /// 写入一条日志
    pub fn log(&self, level: LogLevel, module: &str, message: &str) {
        let timestamp = Local::now().format("%Y-%m-%d %H:%M:%S").to_string();
        let level_str = match level {
            LogLevel::Debug => "DEBUG",
            LogLevel::Info => "INFO",
            LogLevel::Warn => "WARN",
            LogLevel::Error => "ERROR",
        };
        let line = format!(
            "[{}] [{}] [{}] {}\n",
            timestamp, level_str, module, message
        );

        let current_log = self.log_dir.join(format!("{}.log", self.base_name));

        // 检查是否需要轮转
        if let Ok(meta) = fs::metadata(&current_log) {
            if meta.len() >= self.max_file_size {
                self.rotate();
            }
        }

        // 追加写入
        if let Ok(mut file) = OpenOptions::new()
            .create(true)
            .append(true)
            .open(&current_log)
        {
            let _ = file.write_all(line.as_bytes());
            let _ = file.flush();
        }
    }

    /// 日志文件轮转: thing.log → thing.1.log, thing.1.log → thing.2.log, …
    fn rotate(&self) {
        // 删除最旧的文件
        let oldest = self
            .log_dir
            .join(format!("{}.{}.log", self.base_name, self.max_files));
        fs::remove_file(&oldest).ok();

        // 依次重命名
        for i in (1..self.max_files).rev() {
            let src = self
                .log_dir
                .join(format!("{}.{}.log", self.base_name, i));
            let dst = self
                .log_dir
                .join(format!("{}.{}.log", self.base_name, i + 1));
            fs::rename(&src, &dst).ok();
        }

        // thing.log → thing.1.log
        let current = self.log_dir.join(format!("{}.log", self.base_name));
        let first_rotated = self
            .log_dir
            .join(format!("{}.1.log", self.base_name));
        fs::rename(&current, &first_rotated).ok();
    }

    /// 读取日志（支持按模块/级别过滤、条数限制）
    pub fn get_logs(
        &self,
        module: Option<&str>,
        level: Option<LogLevel>,
        limit: Option<usize>,
    ) -> Vec<LogEntry> {
        let mut entries: Vec<LogEntry> = Vec::new();

        // 收集所有日志文件（包括轮转文件）
        let mut log_files: Vec<PathBuf> = Vec::new();
        let current = self.log_dir.join(format!("{}.log", self.base_name));
        if current.exists() {
            log_files.push(current);
        }
        for i in 1..=self.max_files {
            let rotated = self
                .log_dir
                .join(format!("{}.{}.log", self.base_name, i));
            if rotated.exists() {
                log_files.push(rotated);
            }
        }

        for path in &log_files {
            if let Ok(file) = File::open(path) {
                for line in BufReader::new(file).lines().flatten() {
                    if let Some(entry) = Self::parse_line(&line) {
                        if let Some(ref m) = module {
                            if entry.module != *m {
                                continue;
                            }
                        }
                        if let Some(ref l) = level {
                            if entry.level != *l {
                                continue;
                            }
                        }
                        entries.push(entry);
                    }
                }
            }
        }

        // 按时间戳降序（最新在前）
        entries.sort_by(|a, b| b.timestamp.cmp(&a.timestamp));

        if let Some(n) = limit {
            entries.truncate(n);
        }

        entries
    }

    /// 解析一行日志: `[YYYY-MM-DD HH:MM:SS] [LEVEL] [MODULE] message`
    fn parse_line(line: &str) -> Option<LogEntry> {
        let line = line.trim();
        if line.len() < 22 || !line.starts_with('[') {
            return None;
        }

        let ts_end = line[1..].find(']')? + 1;
        let timestamp = line[1..ts_end].to_string();

        let rest = line[ts_end + 1..].trim();
        if !rest.starts_with('[') {
            return None;
        }

        let lv_end = rest[1..].find(']')? + 1;
        let level_str = &rest[1..lv_end];
        let level = match level_str {
            "DEBUG" => LogLevel::Debug,
            "INFO" => LogLevel::Info,
            "WARN" => LogLevel::Warn,
            "ERROR" => LogLevel::Error,
            _ => return None,
        };

        let rest = rest[lv_end + 1..].trim();
        if !rest.starts_with('[') {
            return None;
        }

        let mod_end = rest[1..].find(']')? + 1;
        let module = rest[1..mod_end].to_string();

        let message = rest[mod_end + 1..].trim().to_string();

        Some(LogEntry {
            timestamp,
            level,
            module,
            message,
        })
    }

    /// 清空所有日志文件
    pub fn clear_logs(&self) -> Result<(), String> {
        let current = self.log_dir.join(format!("{}.log", self.base_name));
        fs::remove_file(&current).map_err(|e| e.to_string())?;
        for i in 1..=self.max_files {
            let rotated = self
                .log_dir
                .join(format!("{}.{}.log", self.base_name, i));
            fs::remove_file(&rotated).ok();
        }
        Ok(())
    }

    /// 获取日志系统信息
    pub fn get_info(&self) -> LogInfo {
        let mut log_files: Vec<String> = Vec::new();
        let mut total_size: u64 = 0;

        let current = self.log_dir.join(format!("{}.log", self.base_name));
        if current.exists() {
            if let Ok(meta) = fs::metadata(&current) {
                total_size += meta.len();
            }
            log_files.push(format!("{}.log", self.base_name));
        }
        for i in 1..=self.max_files {
            let rotated = self
                .log_dir
                .join(format!("{}.{}.log", self.base_name, i));
            if rotated.exists() {
                if let Ok(meta) = fs::metadata(&rotated) {
                    total_size += meta.len();
                }
                log_files.push(format!("{}.{}.log", self.base_name, i));
            }
        }

        LogInfo {
            log_dir: self.log_dir.to_string_lossy().to_string(),
            log_files,
            total_size_bytes: total_size,
            max_file_size_bytes: self.max_file_size,
            max_files: self.max_files,
        }
    }
}

// ===== Tauri 命令 =====

#[tauri::command]
pub fn log_message(
    state: tauri::State<'_, LogManager>,
    level: String,
    module: String,
    message: String,
) -> Result<(), String> {
    let level = match level.as_str() {
        "debug" => LogLevel::Debug,
        "info" => LogLevel::Info,
        "warn" => LogLevel::Warn,
        "error" => LogLevel::Error,
        _ => return Err(format!("无效的日志级别: {}", level)),
    };
    state.log(level, &module, &message);
    Ok(())
}

#[tauri::command]
pub fn get_logs(
    state: tauri::State<'_, LogManager>,
    module: Option<String>,
    level: Option<String>,
    limit: Option<usize>,
) -> Vec<LogEntry> {
    let level = level.and_then(|l| match l.as_str() {
        "debug" => Some(LogLevel::Debug),
        "info" => Some(LogLevel::Info),
        "warn" => Some(LogLevel::Warn),
        "error" => Some(LogLevel::Error),
        _ => None,
    });
    state.get_logs(module.as_deref(), level, limit)
}

#[tauri::command]
pub fn clear_logs(state: tauri::State<'_, LogManager>) -> Result<(), String> {
    state.clear_logs()
}

#[tauri::command]
pub fn get_log_info(state: tauri::State<'_, LogManager>) -> LogInfo {
    state.get_info()
}