92 lines
3.3 KiB
Rust
92 lines
3.3 KiB
Rust
use serde::{Deserialize, Serialize};
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use std::fs;
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use std::path::PathBuf;
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use std::sync::atomic::{AtomicU64, Ordering};
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use super::task::{DownloadTask, DownloaderSettings};
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/// 引擎持久化状态（序列化到 engine_state.json）
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#[derive(Serialize, Deserialize)]
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pub struct EngineState {
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/// 所有任务（active + queued + paused + complete + error）
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#[serde(default)]
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pub tasks: Vec<DownloadTask>,
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/// 下载设置
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#[serde(default)]
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pub settings: DownloaderSettings,
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/// 自增 ID 计数器（不序列化为 hex，存原始数字）
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#[serde(default)]
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pub next_id: u64,
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}
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impl Default for EngineState {
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fn default() -> Self {
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Self {
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tasks: Vec::new(),
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settings: DownloaderSettings::default(),
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next_id: 1,
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}
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}
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}
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/// 存储管理器：负责加载/保存引擎状态到 JSON 文件
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pub struct Storage {
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state_path: PathBuf,
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/// ID 计数器（内存中维护，与 EngineState.next_id 同步）
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pub id_counter: AtomicU64,
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}
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impl Storage {
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pub fn new(data_dir: PathBuf) -> Self {
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// 确保数据目录存在（首次启动或目录被删除时自动创建）
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if let Err(e) = fs::create_dir_all(&data_dir) {
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crate::logger::log_error("download", &format!("创建数据目录失败: {} ({})", data_dir.display(), e));
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}
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let state_path = data_dir.join("engine_state.json");
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let existing = Self::load_raw(&state_path);
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let next_id = existing.as_ref().map(|s| s.next_id).unwrap_or(1);
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Self {
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state_path,
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id_counter: AtomicU64::new(next_id),
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}
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}
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/// 生成下一个任务 ID（16 位 hex 字符串）
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pub fn next_task_id(&self) -> String {
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let id = self.id_counter.fetch_add(1, Ordering::SeqCst);
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format!("{:016x}", id)
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}
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/// 从磁盘加载状态
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fn load_raw(path: &PathBuf) -> Option<EngineState> {
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let raw = fs::read_to_string(path).ok()?;
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serde_json::from_str::<EngineState>(&raw).ok()
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}
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/// 加载完整状态（若文件不存在返回默认值）
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pub fn load(&self) -> EngineState {
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Self::load_raw(&self.state_path).unwrap_or_default()
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}
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/// 保存状态到磁盘（原子写：先写 .tmp 再 rename 覆盖，
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/// 避免进程崩溃时产生半写/截断的状态文件导致任务列表丢失）
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/// 失败返回 Err，由调用方决定是否将任务置为 Error（防止"看似已保存"的假象）。
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pub fn save(&self, mut state: EngineState) -> Result<(), String> {
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// 同步 ID 计数器
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state.next_id = self.id_counter.load(Ordering::SeqCst);
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let json = serde_json::to_string_pretty(&state)
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.map_err(|e| format!("序列化状态失败: {}", e))?;
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// 兜底：若父目录被外部删除则在写入前重建
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if let Some(parent) = self.state_path.parent() {
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let _ = fs::create_dir_all(parent);
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}
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let tmp_path = PathBuf::from(format!("{}.tmp", self.state_path.display()));
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fs::write(&tmp_path, json).map_err(|e| format!("保存状态失败: {}", e))?;
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fs::rename(&tmp_path, &self.state_path).map_err(|e| {
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let _ = fs::remove_file(&tmp_path);
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format!("替换状态文件失败: {}", e)
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})?;
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Ok(())
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}
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}
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