feat: Add diff analyzer (closes #176)

scripts/diff_analyzer.py

@@ -0,0 +1,216 @@
+#!/usr/bin/env python3
+"""
+Diff Analyzer — Parse unified diffs and categorize every change.
+
+Pipeline 6.1 for Compounding Intelligence.
+"""
+
+import re
+from dataclasses import dataclass, field, asdict
+from enum import Enum
+from typing import List, Dict, Any, Optional
+
+
+class ChangeCategory(Enum):
+    ADDED = "added"
+    DELETED = "deleted"
+    MODIFIED = "modified"
+    MOVED = "moved"
+    CONTEXT = "context"
+
+
+@dataclass
+class Hunk:
+    """A single diff hunk with header, line ranges, and category."""
+    header: str
+    old_start: int
+    old_count: int
+    new_start: int
+    new_count: int
+    lines: List[str] = field(default_factory=list)
+    category: ChangeCategory = ChangeCategory.CONTEXT
+
+    def to_dict(self) -> Dict[str, Any]:
+        d = asdict(self)
+        d["category"] = self.category.value
+        return d
+
+
+@dataclass
+class FileChange:
+    """A single file's changes."""
+    path: str
+    old_path: Optional[str] = None  # For renames
+    hunks: List[Hunk] = field(default_factory=list)
+    added_lines: int = 0
+    deleted_lines: int = 0
+    is_new: bool = False
+    is_deleted: bool = False
+    is_renamed: bool = False
+    is_binary: bool = False
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {
+            "path": self.path,
+            "old_path": self.old_path,
+            "hunks": [h.to_dict() for h in self.hunks],
+            "added_lines": self.added_lines,
+            "deleted_lines": self.deleted_lines,
+            "is_new": self.is_new,
+            "is_deleted": self.is_deleted,
+            "is_renamed": self.is_renamed,
+            "is_binary": self.is_binary,
+        }
+
+
+@dataclass
+class ChangeSummary:
+    """Aggregate stats + per-file breakdown."""
+    files: List[FileChange] = field(default_factory=list)
+    total_added: int = 0
+    total_deleted: int = 0
+    total_files_changed: int = 0
+    total_hunks: int = 0
+    new_files: int = 0
+    deleted_files: int = 0
+    renamed_files: int = 0
+    binary_files: int = 0
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {
+            "total_files_changed": self.total_files_changed,
+            "total_added": self.total_added,
+            "total_deleted": self.total_deleted,
+            "total_hunks": self.total_hunks,
+            "new_files": self.new_files,
+            "deleted_files": self.deleted_files,
+            "renamed_files": self.renamed_files,
+            "binary_files": self.binary_files,
+            "files": [f.to_dict() for f in self.files],
+        }
+
+
+class DiffAnalyzer:
+    """Parses unified diff format and produces structured ChangeSummary."""
+
+    HUNK_HEADER_RE = re.compile(r"^@@\s+-(\d+)(?:,(\d+))?\s+\+(\d+)(?:,(\d+))?\s+@@(.*)$")
+    DIFF_FILE_RE = re.compile(r"^diff --git a/(.*) b/(.*)")
+    RENAME_RE = re.compile(r"^rename from (.+)$")
+    RENAME_TO_RE = re.compile(r"^rename to (.+)$")
+    NEW_FILE_RE = re.compile(r"^new file mode")
+    DELETED_FILE_RE = re.compile(r"^deleted file mode")
+    BINARY_RE = re.compile(r"^Binary files .* differ")
+
+    def analyze(self, diff_text: str) -> ChangeSummary:
+        """Parse a unified diff and return a ChangeSummary."""
+        summary = ChangeSummary()
+        if not diff_text or not diff_text.strip():
+            return summary
+
+        # Split diff into per-file sections
+        file_diffs = self._split_files(diff_text)
+
+        for file_diff in file_diffs:
+            fc = self._parse_file_diff(file_diff)
+            summary.files.append(fc)
+            summary.total_added += fc.added_lines
+            summary.total_deleted += fc.deleted_lines
+            summary.total_hunks += len(fc.hunks)
+            if fc.is_new:
+                summary.new_files += 1
+            if fc.is_deleted:
+                summary.deleted_files += 1
+            if fc.is_renamed:
+                summary.renamed_files += 1
+            if fc.is_binary:
+                summary.binary_files += 1
+
+        summary.total_files_changed = len(summary.files)
+        return summary
+
+    def _split_files(self, diff_text: str) -> List[str]:
+        """Split a multi-file diff into individual file diffs."""
+        lines = diff_text.split("\n")
+        chunks = []
+        current = []
+        for line in lines:
+            if line.startswith("diff --git ") and current:
+                chunks.append("\n".join(current))
+                current = [line]
+            else:
+                current.append(line)
+        if current:
+            chunks.append("\n".join(current))
+        return chunks
+
+    def _parse_file_diff(self, diff_text: str) -> FileChange:
+        """Parse a single file's diff section."""
+        lines = diff_text.split("\n")
+        fc = FileChange(path="")
+
+        # Extract file paths
+        for line in lines:
+            m = self.DIFF_FILE_RE.match(line)
+            if m:
+                fc.path = m.group(2)
+                break
+
+        # Check for special states
+        for line in lines:
+            if self.NEW_FILE_RE.match(line):
+                fc.is_new = True
+            elif self.DELETED_FILE_RE.match(line):
+                fc.is_deleted = True
+            elif self.RENAME_RE.match(line):
+                fc.old_path = m.group(1) if (m := self.RENAME_RE.match(line)) else None
+                fc.is_renamed = True
+            elif self.BINARY_RE.match(line):
+                fc.is_binary = True
+                return fc  # No hunks for binary
+
+        # Rename TO
+        for line in lines:
+            m = self.RENAME_TO_RE.match(line)
+            if m and fc.is_renamed:
+                fc.path = m.group(1)
+
+        # Parse hunks
+        current_hunk = None
+        for line in lines:
+            m = self.HUNK_HEADER_RE.match(line)
+            if m:
+                if current_hunk:
+                    self._classify_hunk(current_hunk, fc)
+                    fc.hunks.append(current_hunk)
+                current_hunk = Hunk(
+                    header=m.group(5).strip(),
+                    old_start=int(m.group(1)),
+                    old_count=int(m.group(2) or 1),
+                    new_start=int(m.group(3)),
+                    new_count=int(m.group(4) or 1),
+                )
+            elif current_hunk and (line.startswith("+") or line.startswith("-") or line.startswith(" ")):
+                current_hunk.lines.append(line)
+
+        if current_hunk:
+            self._classify_hunk(current_hunk, fc)
+            fc.hunks.append(current_hunk)
+
+        return fc
+
+    def _classify_hunk(self, hunk: Hunk, fc: FileChange):
+        """Classify a hunk and count lines."""
+        added = sum(1 for l in hunk.lines if l.startswith("+"))
+        deleted = sum(1 for l in hunk.lines if l.startswith("-"))
+
+        fc.added_lines += added
+        fc.deleted_lines += deleted
+
+        if added > 0 and deleted == 0:
+            hunk.category = ChangeCategory.ADDED
+        elif deleted > 0 and added == 0:
+            hunk.category = ChangeCategory.DELETED
+        elif added > 0 and deleted > 0:
+            hunk.category = ChangeCategory.MODIFIED
+        else:
+            hunk.category = ChangeCategory.CONTEXT