Redlines

Extract and normalize tracked changes ("redlines") from DOC, DOCX, and PDF documents into a single unified shape.

Each format is handled by a dedicated backend:

• DOC — legacy Word binary format, parsed by doc_redlines (precompiled Rust NIF).
• DOCX — Office Open XML, parsed in pure Elixir by reading word/document.xml from the zip and extracting <w:ins> / <w:del> via SweetXml.
• PDF — parsed by pdf_redlines (precompiled Rust/MuPDF NIF), which detects strikethroughs and underlines drawn over text.

All results are normalized into Redlines.Change structs regardless of source format. Neither Rust NIF requires a local Rust toolchain — precompiled binaries are fetched from GitHub Releases.

Installation

Add :redlines to your dependencies:

def deps do
  [
    {:redlines, "~> 0.9.3"}
  ]
end

doc_redlines and pdf_redlines are pulled in transitively; both ship precompiled NIFs, so no Rust toolchain is required.

Usage

Extracting Changes

# DOC — legacy Word binary format (delegates to doc_redlines)
{:ok, %Redlines.Result{changes: changes, source: :doc}} =
  Redlines.extract("contract_v2.doc")

# DOCX — extracts <w:ins> and <w:del> from word/document.xml
{:ok, %Redlines.Result{changes: changes, source: :docx}} =
  Redlines.extract("contract_v2.docx")

# PDF — detects strikethrough/underline markup (delegates to pdf_redlines)
{:ok, %Redlines.Result{changes: changes, source: :pdf}} =
  Redlines.extract("contract_v2.pdf")

# Override type inference
{:ok, result} = Redlines.extract("document.bin", type: :docx)

# Forward tuning options to pdf_redlines
{:ok, result} = Redlines.extract("scan.pdf", pdf_opts: [red_r_min: 150])

Type is inferred from the file extension (.doc, .docx, .pdf); pass :type to override.

Accepting DOCX Track Changes

Four variants, covering path-vs-binary input and with/without warnings about other revision markup (moves, *PrChange property-change history):

# Path input
{:ok, cleaned_docx} = Redlines.clean_docx("contract_v2.docx")
{:ok, cleaned_docx, warnings} = Redlines.clean_docx_with_warnings("contract_v2.docx")

# Binary input
{:ok, cleaned_docx} = Redlines.clean_docx_binary(docx_bytes)
{:ok, cleaned_docx, warnings} = Redlines.clean_docx_binary_with_warnings(docx_bytes)

The cleaner removes <w:del>…</w:del>, unwraps <w:ins>…</w:ins>, and drops other WordprocessingML revision markup where possible. DOC and PDF do not have analogous cleaners — accepting tracked changes is a DOCX-only operation.

The Change Struct

Every tracked change is normalized into a Redlines.Change:

%Redlines.Change{
  type: :deletion | :insertion | :paired,
  deletion: "removed text" | nil,
  insertion: "added text" | nil,
  location: "page 3, paragraph 2" | nil,
  meta: %{"source" => "docx" | "doc" | "pdf", ...}
}

• :deletion — text was removed (deletion populated)
• :insertion — text was added (insertion populated)
• :paired — a deletion and insertion representing a replacement (both populated)

meta varies by source:

DOC and PDF may emit :paired changes; DOCX only emits :insertion and :deletion.

Formatting for LLM Prompts

format_for_llm/2 produces a structured text summary suitable for including in LLM prompts:

Redlines.format_for_llm(changes)
# DELETIONS (removed content):
#   - "the old clause"
#
#
# INSERTIONS (new content):
#   + "the new clause"
#
#
# DELETED → INSERTED:
#   "old term" → "new term"

Options:

• :pair_separator — separator between deleted/inserted pairs (default "→")
• :max_len — truncation length for long text (default 150)

Accepts a Redlines.Result, a list of Redlines.Change structs, a raw DOCX track-changes map (%{insertions: [...], deletions: [...]}), or a list of pdf_redlines entries.

Performance

• DOC — Rust NIF on a dirty scheduler; typical documents complete in tens of milliseconds.
• DOCX — pure Elixir XML parsing; effectively instant.
• PDF — Rust/MuPDF NIF on a dirty scheduler; under 700 ms even on 35 MB scanned PDFs.

License

MIT — see LICENSE.