[inter-v2-04] Chunking cho RAG embedding — trace + demo test

[Supermonters]

Closes #411

cc @anhnth24 — em xin gửi PR inter-v2-04 để anh review ạ.

Summary

• Thêm unit test trong crates/core/src/chunk.rs (mod tests): demo chunk RAG + test phá adversarial trên Markdown inline.
• Trace read-only: chunk_markdown → prepare_chunks (server) → canonical_input (embedding payload {heading}\n{body}).
• Không đổi thuật toán production — không thêm file bench/INTER_V2_* hay fixture .md riêng.

Thay đổi file

crates/core/src/chunk.rs

1. inter_v2_04_chunk_rag_trace_demo

   • Markdown inline H1 → H2 → H3 + section dài (max_chars = 320 để thấy split; production = 2000).
   • Assert count, heading path, thứ tự index, UTF-8-safe.

2. inter_v2_04_empty_heading_body_only / inter_v2_04_crlf_embedding_body_is_lf

   • Edge: không heading; CRLF → body LF, span map về \r\n trên nguồn.

3. inter_v2_04_adversarial_* (test phá)

   • #KhôngSpace không phải heading; empty/whitespace → 0 chunk; hard cut chữ Việt UTF-8-safe; duplicate body anchor order; max_chars dưới sàn 200.

Học tập — chunk-level vs run-level

• Run-level (conv/docx.rs): đơn vị <w:r> Word — gộp trước khi ra Markdown.
• Chunk-level (chunk.rs): chia Markdown theo # heading cho RAG/embed; field heading = "Cha > Con".
• Embedding: server gọi ApprovedEmbeddingRuntime::canonical_input(heading_joined, body) → "{heading}\n{body}".
• Gap DKP: chưa tách raw / normalized / embedding text (chỉ body LF + span gốc).

Demo chunk (max_chars=320) → chunk nào được embed?

index	heading_path	embed?
0	Phần I	yes — Phần I\nGiới thiệu.
1	Phần I > Mục 1	yes
2	Phần I > Mục 1 > Tiểu mục 1.1	yes
3–5	Phần I > Mục 2 (split)	yes — cùng heading, body chia đoạn

→ Mọi chunk body non-empty sau prepare_chunks đều embed; desktop build_corpus chỉ bỏ chunk page-marker-only.

Test nào pass? Assertion nào validate?

Loại (AC issue)	Assert	Ý nghĩa
Count	chunks.len() >= 5	H1 + H2 + H3 + split Mục 2
Heading	Phần I, Phần I > Mục 1 > Tiểu mục 1.1	hierarchy đúng
Order	chunks[i].index == i	thứ tự document
Edge CRLF	body LF, span chứa \r\n	embed LF, citation giữ nguồn
Adversarial	empty → 0 chunk; #KhôngSpace → body not heading	không panic

Test phá — kết quả

Scenario	Kết quả
"" / whitespace only	pass — 0 chunk
#KhôngSpace	pass — by design, không nhận heading
ệ×250 hard cut, max_chars=100	pass — sàn 200, UTF-8-safe, ≥2 chunk
duplicate x under # A / # B	pass — anchor thứ hai sau chunk đầu
Sabotage local: heading = String::new() trong push_chunk	đỏ demo + adversarial → restore → xanh

Vì sao test trong chunk.rs (không integration server)?

• Issue scope: hiểu thuật toán chunk + server path read-only.
• Unit test khóa hành vi chunk_markdown / locate_chunk_span trực tiếp; server prepare_chunks đã có test riêng (chưa chạy local macOS — fileconv-server compile fail sandbox mount trên Darwin).

Test plan

• cargo fmt --all -- --check
• cargo metadata --locked --format-version 1 --no-deps
• python3 scripts/check-dependency-policy.py
• cargo test -p fileconv-core inter_v2_04 -- --nocapture
• cargo test -p fileconv-core chunk::
• cargo test -p fileconv-server prepare_chunks (blocked local: server crate compile trên macOS — CI Linux)
• Sabotage local (không commit): phá push_chunk heading → test đỏ; restore → xanh

Made with Cursor

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

Bugbot Autofix prepared fixes for both issues found in the latest run.

• ✅ Fixed: Floor test does not lock 200
  • Both floor tests now assert the first hard-cut piece is exactly 200 characters, so removing or lowering max(200) fails CI.
• ✅ Fixed: UTF-8 assert always succeeds
  • Replaced the always-true str-end boundary check with source-span char-boundary asserts and a mid-glyph cut check on Vietnamese ệ.

Or push these changes by commenting:

@cursor push 5a8e6ab23c

Preview (5a8e6ab23c)

diff --git a/crates/core/src/chunk.rs b/crates/core/src/chunk.rs
--- a/crates/core/src/chunk.rs
+++ b/crates/core/src/chunk.rs
@@ -392,8 +392,13 @@
                 .count()
                 >= 2
         );
+        let mut cursor = 0usize;
         for c in &chunks {
-            assert!(c.text.is_char_boundary(c.text.len()));
+            let (start, end) = locate_chunk_text(&md, cursor, &c.text).expect("span");
+            assert!(md.is_char_boundary(start));
+            assert!(md.is_char_boundary(end));
+            assert_eq!(&md[start..end], c.text.as_str());
+            cursor = end;
         }
     }
 
@@ -433,9 +438,21 @@
         // max_chars=100 bị sàn lên 200 — vẫn phải cắt và UTF-8-safe.
         let chunks = chunk_markdown(&md, 100);
         assert!(chunks.len() >= 2);
+        assert_eq!(
+            chunks[0].chars, 200,
+            "first hard-cut piece must be the 200 floor"
+        );
+        assert!(chunks.iter().all(|c| c.chars <= 200));
+        let mut cursor = 0usize;
         for c in &chunks {
-            assert!(c.chars <= 200);
             assert!(!c.text.is_empty());
+            let (start, end) = locate_chunk_text(&md, cursor, &c.text).expect("span");
+            assert!(md.is_char_boundary(start));
+            assert!(md.is_char_boundary(end));
+            assert_eq!(&md[start..end], c.text.as_str());
+            // ệ is 3 bytes — a mid-glyph offset must not be treated as a cut point.
+            assert!(!md.is_char_boundary(start + 1));
+            cursor = end;
         }
     }
 
@@ -466,6 +483,10 @@
         let md = "# A\n\n".to_string() + &"y".repeat(250);
         let chunks = chunk_markdown(&md, 50);
         assert!(chunks.len() >= 2);
+        assert_eq!(
+            chunks[0].chars, 200,
+            "first hard-cut piece must be the 200 floor"
+        );
         assert!(chunks.iter().all(|c| c.chars <= 200));
     }
 }

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