#!/usr/bin/env python3
"""
Architecture Doc Generator — 4.4

Analyzes codebase structure and generates an architecture overview:
- Maps module dependencies (Python imports within the repo)
- Identifies entry points (main guards, CLI scripts)
- Generates ASCII diagram of module relationships
- Produces one ARCHITECTURE.md per repo

Usage:
  python3 scripts/architecture_doc_generator.py [repo_root]

If no repo_root given, uses current directory.
Outputs ARCHITECTURE.md to the repo root.
"""

import argparse
import re
import sys
from collections import defaultdict
from pathlib import Path


def scan_python_files(root: Path):
    """Find all .py files under root, excluding tests/ and .git/."""
    py_files = []
    for path in root.rglob("*.py"):
        parts = path.parts
        if any(p.startswith('.') for p in parts if p != '.'):
            continue
        if 'test' in parts:
            continue
        if any(x in parts for x in ('venv', 'node_modules', '__pycache__', 'dist', 'build')):
            continue
        py_files.append(path)
    return sorted(py_files)


def module_id(path: Path, root: Path) -> str:
    """Return a readable module identifier."""
    rel = path.relative_to(root)
    if rel.parent == Path('.'):
        return path.stem
    return str(rel.with_suffix('')).replace('/', '.')


def extract_imports(path: Path) -> list[str]:
    """Extract top-level import names from a Python file."""
    try:
        text = path.read_text(errors='ignore')
    except Exception:
        return []
    imports = set()
    # import X or import X.Y.Z
    for m in re.finditer(r'^\s*import\s+([a-zA-Z0-9_.]+)', text, re.MULTILINE):
        imports.add(m.group(1).split('.')[0])
    # from X import Y  (handles absolute and relative: from .X import Y)
    for m in re.finditer(r'^\s*from\s+(\.+)?([a-zA-Z0-9_.]+)\s+import', text, re.MULTILINE):
        imports.add(m.group(2).split('.')[0])
    return sorted(imports)


def build_dependency_graph(py_files: list[Path], root: Path) -> dict[str, set[str]]:
    """Build adjacency: local_module -> set(local_modules it imports)."""
    graph = defaultdict(set)
    # Collect all local module identifiers
    local_ids = set()
    for p in py_files:
        local_ids.add(module_id(p, root))

    for path in py_files:
        src_mod = module_id(path, root)
        for imp in extract_imports(path):
            # Match import to a local module by stem or by full dotted prefix
            target = None
            # Exact match
            if imp in local_ids:
                target = imp
            else:
                # Find module whose stem equals imp, or whose dotted name ends with .imp
                for mid in local_ids:
                    if mid.split('.')[-1] == imp or mid == imp:
                        target = mid
                        break
            if target:
                graph[src_mod].add(target)

    return {k: sorted(v) for k, v in graph.items()}


def find_entry_points(py_files: list[Path]) -> list[Path]:
    """Files with if __name__ == '__main__' guard or executable scripts."""
    entries = []
    for path in py_files:
        try:
            text = path.read_text(errors='ignore')
        except Exception:
            continue
        if 'if __name__' in text and '__main__' in text:
            entries.append(path)
    return sorted(entries, key=lambda p: (not (p.stat().st_mode & 0o111), p.name))


def ascii_diagram(graph: dict[str, list[str]], entries: list[Path], root: Path) -> str:
    """Generate a simple ASCII box-and-arrow diagram."""
    lines = []
    entry_names = {module_id(p, root) for p in entries}
    # All nodes
    nodes = sorted(set(graph.keys()) | set().union(*graph.values()))
    for node in nodes:
        is_entry = node in entry_names
        label = f"*{node}*" if is_entry else f"[{node}]"
        lines.append(label)
        for dep in graph.get(node, []):
            lines.append(f"  └─> {dep}")
    return '\n'.join(lines)


def generate_markdown(root: Path, graph: dict, entries: list[Path], diagram: str) -> str:
    root_name = root.name
    md = []
    md.append(f"# Architecture: {root_name}")
    md.append("")
    md.append("**Generated by:** `scripts/architecture_doc_generator.py`")
    md.append("")
    md.append("## Entry Points")
    if entries:
        for p in entries:
            rel = p.relative_to(root)
            md.append(f"- `{rel}`")
    else:
        md.append("_No entry points detected._")
    md.append("")
    md.append("## Module Dependencies")
    if graph:
        md.append("| Module | Imports |")
        md.append("|--------|---------|")
        for mod in sorted(graph.keys()):
            deps = ', '.join(sorted(graph[mod])) if graph[mod] else '_none_'
            md.append(f"| `{mod}` | `{deps}` |")
    else:
        md.append("_No dependencies detected._")
    md.append("")
    md.append("## ASCII Diagram")
    md.append("```")
    md.append(diagram)
    md.append("```")
    md.append("")
    md.append("_Generated automatically. Keep this file in sync with code changes by re-running the generator._")
    return '\n'.join(md)


def main():
    parser = argparse.ArgumentParser(description="Generate architecture documentation")
    parser.add_argument("repo_root", nargs="?", default=".", help="Repository root (default: current directory)")
    args = parser.parse_args()

    root = Path(args.repo_root).resolve()
    py_files = scan_python_files(root)
    if not py_files:
        print("No Python files found — nothing to do.", file=sys.stderr)
        sys.exit(1)

    graph = build_dependency_graph(py_files, root)
    entries = find_entry_points(py_files)
    diagram = ascii_diagram(graph, entries, root)
    markdown = generate_markdown(root, graph, entries, diagram)

    out_path = root / "ARCHITECTURE.md"
    out_path.write_text(markdown, encoding='utf-8')
    print(f"Written: {out_path}")
    print(f"  Modules scanned: {len(py_files)}")
    print(f"  Entry points: {len(entries)}")
    print(f"  Dependency edges: {sum(len(v) for v in graph.values())}")


if __name__ == "__main__":
    main()