Upload compare.py

compare.py

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+"""
+ClauseGuard — Contract Comparison Engine
+═══════════════════════════════════════
+Compare two contracts side-by-side:
+  • Clause-level diff (added/removed/modified clauses)
+  • Risk delta (which contract is more favorable)
+  • Alignment score (similarity between documents)
+"""
+
+import re
+from difflib import SequenceMatcher
+from collections import defaultdict
+
+def _normalize_clause(text):
+    """Normalize clause text for comparison."""
+    text = text.lower()
+    text = re.sub(r'[^a-z0-9\s]', ' ', text)
+    text = re.sub(r'\s+', ' ', text).strip()
+    return text
+
+def _clause_similarity(a, b):
+    """Compute similarity between two clauses."""
+    return SequenceMatcher(None, _normalize_clause(a), _normalize_clause(b)).ratio()
+
+def _extract_clause_type(clause_text):
+    """Heuristic clause type detection for alignment."""
+    text_lower = clause_text.lower()
+    type_keywords = {
+        "governing law": ["govern", "law", "jurisdiction"],
+        "termination": ["terminat", "cancel", "end"],
+        "indemnification": ["indemnif", "hold harmless"],
+        "confidentiality": ["confidential", "non-disclosure"],
+        "liability": ["liability", "liable", "damages"],
+        "payment": ["payment", "fee", "price", "compensat"],
+        "intellectual property": ["intellectual", "ip", "copyright", "patent"],
+        "warranty": ["warrant", "guarantee"],
+        "force majeure": ["force majeure", "act of god"],
+        "arbitration": ["arbitrat", "mediation"],
+        "assignment": ["assign", "transfer"],
+        "non-compete": ["compete", "competition"],
+        "renewal": ["renew", "extend"],
+        "effective date": ["effective date", "commencement"],
+    }
+    for ctype, keywords in type_keywords.items():
+        if any(kw in text_lower for kw in keywords):
+            return ctype
+    return "general"
+
+def compare_contracts(text_a, text_b, clauses_a=None, clauses_b=None):
+    """
+    Compare two contract texts and return structural diff.
+
+    Returns dict with:
+      - alignment_score: float 0-1
+      - added_clauses: clauses in B not in A
+      - removed_clauses: clauses in A not in B
+      - modified_clauses: clauses that are similar but different
+      - risk_delta: which contract is riskier
+      - clause_type_map: clauses grouped by type for both docs
+    """
+    if not text_a or not text_b:
+        return {"error": "Both contracts required"}
+
+    # Split into clauses if not provided
+    if clauses_a is None:
+        clauses_a = _split_clauses(text_a)
+    if clauses_b is None:
+        clauses_b = _split_clauses(text_b)
+
+    # Build clause type maps
+    type_map_a = defaultdict(list)
+    type_map_b = defaultdict(list)
+    for c in clauses_a:
+        type_map_a[_extract_clause_type(c)].append(c)
+    for c in clauses_b:
+        type_map_b[_extract_clause_type(c)].append(c)
+
+    # Find matches
+    matched_a = set()
+    matched_b = set()
+    modified = []
+
+    SIMILARITY_THRESHOLD = 0.75
+    MODIFIED_THRESHOLD = 0.45
+
+    for i, ca in enumerate(clauses_a):
+        best_sim = 0
+        best_j = -1
+        for j, cb in enumerate(clauses_b):
+            if j in matched_b:
+                continue
+            sim = _clause_similarity(ca, cb)
+            if sim > best_sim:
+                best_sim = sim
+                best_j = j
+
+        if best_sim >= SIMILARITY_THRESHOLD:
+            matched_a.add(i)
+            matched_b.add(best_j)
+            if best_sim < 0.95:
+                modified.append({
+                    "type": "modified",
+                    "similarity": round(best_sim, 3),
+                    "clause_a": ca[:200],
+                    "clause_b": clauses_b[best_j][:200],
+                    "clause_type": _extract_clause_type(ca),
+                })
+        elif best_sim >= MODIFIED_THRESHOLD:
+            modified.append({
+                "type": "partial",
+                "similarity": round(best_sim, 3),
+                "clause_a": ca[:200],
+                "clause_b": clauses_b[best_j][:200] if best_j >= 0 else "",
+                "clause_type": _extract_clause_type(ca),
+            })
+
+    removed = [clauses_a[i] for i in range(len(clauses_a)) if i not in matched_a]
+    added = [clauses_b[j] for j in range(len(clauses_b)) if j not in matched_b]
+
+    # Compute alignment score
+    total_pairs = max(len(clauses_a), len(clauses_b))
+    if total_pairs > 0:
+        alignment = len(matched_a) / total_pairs
+    else:
+        alignment = 0.0
+
+    # Risk delta: compare length and presence of risk keywords
+    risk_keywords = ["unlimited", "unilateral", "waive", "arbitration", "indemnif",
+                     "not liable", "no warranty", "sole discretion"]
+    risk_a = sum(1 for kw in risk_keywords if kw in text_a.lower())
+    risk_b = sum(1 for kw in risk_keywords if kw in text_b.lower())
+
+    if risk_a > risk_b + 2:
+        risk_delta = "Contract A is significantly riskier"
+        risk_winner = "B"
+    elif risk_b > risk_a + 2:
+        risk_delta = "Contract B is significantly riskier"
+        risk_winner = "A"
+    else:
+        risk_delta = "Similar risk profiles"
+        risk_winner = "tie"
+
+    return {
+        "alignment_score": round(alignment, 3),
+        "contract_a_clauses": len(clauses_a),
+        "contract_b_clauses": len(clauses_b),
+        "added_clauses": [{"text": c[:200], "type": _extract_clause_type(c)} for c in added[:50]],
+        "removed_clauses": [{"text": c[:200], "type": _extract_clause_type(c)} for c in removed[:50]],
+        "modified_clauses": modified[:50],
+        "risk_delta": risk_delta,
+        "risk_winner": risk_winner,
+        "type_map_a": {k: len(v) for k, v in type_map_a.items()},
+        "type_map_b": {k: len(v) for k, v in type_map_b.items()},
+    }
+
+def _split_clauses(text):
+    """Split text into clauses."""
+    text = re.sub(r'\n{3,}', '\n\n', text.strip())
+    parts = re.split(
+        r'(?<=[.!?])\s+(?=[A-Z0-9(])|(?:\n\n)(?=\d+[.)]\s|\([a-z]\)\s|[A-Z][A-Z\s]{2,})',
+        text
+    )
+    return [p.strip() for p in parts if len(p.strip()) > 30]
+
+def render_comparison_html(result):
+    """Render comparison results as HTML for Gradio."""
+    if "error" in result:
+        return f'<p style="color:#dc2626;">{result["error"]}</p>'
+
+    html = f'''
+    <div style="font-family:system-ui,sans-serif;">
+      <div style="display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-bottom:16px;">
+        <div style="padding:12px;border-radius:8px;background:#eff6ff;border:1px solid #bfdbfe;text-align:center;">
+          <div style="font-size:24px;font-weight:700;color:#1d4ed8;">{result["contract_a_clauses"]}</div>
+          <div style="font-size:12px;color:#3b82f6;">Clauses in Contract A</div>
+        </div>
+        <div style="padding:12px;border-radius:8px;background:#fefce8;border:1px solid #fde68a;text-align:center;">
+          <div style="font-size:24px;font-weight:700;color:#a16207;">{result["contract_b_clauses"]}</div>
+          <div style="font-size:12px;color:#ca8a04;">Clauses in Contract B</div>
+        </div>
+      </div>
+
+      <div style="padding:12px;border-radius:8px;background:#f9fafb;border:1px solid #e5e7eb;margin-bottom:16px;text-align:center;">
+        <div style="font-size:28px;font-weight:700;color:#374151;">{result["alignment_score"]*100:.1f}%</div>
+        <div style="font-size:12px;color:#6b7280;">Alignment Score</div>
+      </div>
+
+      <div style="padding:12px;border-radius:8px;background:{
+          "#fef2f2" if result["risk_winner"] != "tie" else "#f0fdf4"
+      };border:1px solid {
+          "#fecaca" if result["risk_winner"] != "tie" else "#bbf7d0"
+      };margin-bottom:16px;text-align:center;">
+        <span style="font-size:14px;font-weight:600;color:{
+            "#dc2626" if result["risk_winner"] != "tie" else "#16a34a"
+        };">⚖️ {result["risk_delta"]}</span>
+      </div>
+    '''
+
+    # Modified clauses
+    if result["modified_clauses"]:
+        html += '<div style="margin-bottom:16px;"><h3 style="font-size:14px;color:#374151;margin-bottom:8px;">📝 Modified Clauses</h3>'
+        for m in result["modified_clauses"][:20]:
+            html += f'''
+            <div style="border:1px solid #e5e7eb;border-radius:6px;padding:10px;margin-bottom:8px;">
+              <div style="font-size:11px;color:#6b7280;margin-bottom:4px;">{m["clause_type"].upper()} · Similarity: {m["similarity"]*100:.0f}%</div>
+              <div style="display:grid;grid-template-columns:1fr 1fr;gap:8px;">
+                <div style="background:#fef2f2;padding:6px;border-radius:4px;font-size:12px;color:#991b1b;">{m["clause_a"][:150]}...</div>
+                <div style="background:#f0fdf4;padding:6px;border-radius:4px;font-size:12px;color:#166534;">{m["clause_b"][:150]}...</div>
+              </div>
+            </div>
+            '''
+        html += '</div>'
+
+    # Added clauses
+    if result["added_clauses"]:
+        html += '<div style="margin-bottom:16px;"><h3 style="font-size:14px;color:#374151;margin-bottom:8px;">➕ Added in Contract B</h3>'
+        for a in result["added_clauses"][:15]:
+            html += f'<div style="background:#f0fdf4;padding:8px;border-radius:4px;font-size:12px;color:#166534;margin-bottom:4px;border-left:3px solid #22c55e;"><b>{a["type"].upper()}</b> · {a["text"][:150]}...</div>'
+        html += '</div>'
+
+    # Removed clauses
+    if result["removed_clauses"]:
+        html += '<div style="margin-bottom:16px;"><h3 style="font-size:14px;color:#374151;margin-bottom:8px;">➖ Removed from Contract A</h3>'
+        for r in result["removed_clauses"][:15]:
+            html += f'<div style="background:#fef2f2;padding:8px;border-radius:4px;font-size:12px;color:#991b1b;margin-bottom:4px;border-left:3px solid #ef4444;"><b>{r["type"].upper()}</b> · {r["text"][:150]}...</div>'
+        html += '</div>'
+
+    html += '</div>'
+    return html