From b0a1ee0de238758144770c2225d50595439cd021 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8E=8B=E5=BE=B7=E5=AE=87?= <kvtodev@outlook.com>
Date: Sat, 5 Sep 2026 10:42:13 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96=20DirectProject=20=E5=8E=86?=
 =?UTF-8?q?=E5=8F=B2=E5=B9=82=E7=AD=89=E6=A3=80=E6=9F=A5?=
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按文件尾部反向分块查找带 id 的历史 item

避免每次追加都完整读取并扫描历史文件
---
 .../src/agent/direct_project_history.rs       | 93 ++++++++++++++++++-
 1 file changed, 88 insertions(+), 5 deletions(-)

diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/direct_project_history.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/direct_project_history.rs
index c438990e0..edad7c9c8 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/direct_project_history.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/direct_project_history.rs
@@ -5,7 +5,7 @@ use crate::project::{
 use crate::{LocalConversationMessageRecord, LocalConversationResult};
 use serde_json::Value;
 use std::fs::File;
-use std::io::{BufRead, BufReader};
+use std::io::{BufRead, BufReader, Read, Seek, SeekFrom};
 use std::path::{Path, PathBuf};
 
 const DIRECT_PROJECT_HISTORY_RECORD_TYPE: &str = "response_item";
@@ -22,6 +22,92 @@ fn record(item: &Value) -> Result<String, String> {
     .map_err(|error| format!("序列化 DirectProject 历史失败：{error}"))
 }
 
+const DIRECT_PROJECT_HISTORY_REVERSE_SCAN_CHUNK_BYTES: usize = 16 * 1024;
+
+fn find_direct_project_history_item_by_id_at(
+    path: &Path,
+    item_id: &str,
+) -> Result<Option<Value>, String> {
+    let mut file = File::open(path)
+        .map_err(|error| format!("打开 DirectProject 历史失败：{}: {error}", path.display()))?;
+    let mut position = file
+        .metadata()
+        .map_err(|error| {
+            format!(
+                "读取 DirectProject 历史元数据失败：{}: {error}",
+                path.display()
+            )
+        })?
+        .len();
+    let mut pending = Vec::new();
+    let mut chunk = vec![0u8; DIRECT_PROJECT_HISTORY_REVERSE_SCAN_CHUNK_BYTES];
+
+    loop {
+        if position == 0 {
+            break;
+        }
+        let read_len = usize::try_from(position)
+            .unwrap_or(usize::MAX)
+            .min(chunk.len());
+        position -= read_len as u64;
+        file.seek(SeekFrom::Start(position))
+            .map_err(|error| format!("定位 DirectProject 历史失败：{}: {error}", path.display()))?;
+        file.read_exact(&mut chunk[..read_len])
+            .map_err(|error| format!("读取 DirectProject 历史失败：{}: {error}", path.display()))?;
+
+        let mut combined = Vec::with_capacity(read_len + pending.len());
+        combined.extend_from_slice(&chunk[..read_len]);
+        combined.extend_from_slice(&pending);
+        let mut line_end = combined.len();
+        while let Some(newline) = combined[..line_end].iter().rposition(|byte| *byte == b'\n') {
+            let line = &combined[newline + 1..line_end];
+            if !line.is_empty() {
+                if let Some(item) = direct_project_history_item_from_line(path, line)? {
+                    if item.get("id").and_then(Value::as_str) == Some(item_id) {
+                        return Ok(Some(item));
+                    }
+                }
+            }
+            line_end = newline;
+        }
+        pending = combined[..line_end].to_vec();
+    }
+
+    if !pending.is_empty() {
+        if let Some(item) = direct_project_history_item_from_line(path, &pending)? {
+            if item.get("id").and_then(Value::as_str) == Some(item_id) {
+                return Ok(Some(item));
+            }
+        }
+    }
+    Ok(None)
+}
+
+fn direct_project_history_item_from_line(
+    path: &Path,
+    line: &[u8],
+) -> Result<Option<Value>, String> {
+    if line.iter().all(|byte| byte.is_ascii_whitespace()) {
+        return Ok(None);
+    }
+    let parsed: Value = serde_json::from_slice(line)
+        .map_err(|error| format!("解析 DirectProject 历史失败：{}: {error}", path.display()))?;
+    if parsed.get("type").and_then(Value::as_str) != Some(DIRECT_PROJECT_HISTORY_RECORD_TYPE) {
+        return Err(format!(
+            "DirectProject 历史记录类型无效：{}",
+            path.display()
+        ));
+    }
+    let item = parsed
+        .get("payload")
+        .cloned()
+        .ok_or_else(|| format!("DirectProject 历史记录缺少 payload：{}", path.display()))?;
+    if is_direct_project_internal_context_item(&item) {
+        return Ok(None);
+    }
+    Ok(Some(item))
+}
+
 pub(crate) fn append_direct_project_history_item_at(
     root: &Path,
     item: &Value,
@@ -33,10 +119,7 @@ pub(crate) fn append_direct_project_history_item_at(
     let lock = project_append_lock_for(&path)?;
     let _append_guard = lock.lock("DirectProject 历史追加写")?;
     if let Some(item_id) = item.get("id").and_then(Value::as_str) {
-        if let Some(existing) = read_direct_project_history_items_at(root)?
-            .into_iter()
-            .find(|existing| existing.get("id").and_then(Value::as_str) == Some(item_id))
-        {
+        if let Some(existing) = find_direct_project_history_item_by_id_at(&path, item_id)? {
             if &existing == item {
                 return Ok(());
             }