#!/usr/bin/env python3
"""Generate a release diff manifest between two Nexus source snapshots."""

from __future__ import annotations

import argparse
import hashlib
from pathlib import Path


DEFAULT_EXCLUDE_NAMES = {
    ".git",
    "node_modules",
    ".venv-py314",
    ".venv-py312-codex",
    "venv",
    "__pycache__",
    ".ruff_cache",
    ".playwright-mcp",
    ".cursor",
    ".pytest_cache",
    "tmp",
}
DEFAULT_EXCLUDE_SUFFIXES = {".pyc", ".pyo"}
DEFAULT_EXCLUDE_EXACT = {"2025.2", "=2025.2"}
DEFAULT_EXCLUDE_PATTERNS = (".bak-",)


def sha256_file(path: Path) -> str:
    h = hashlib.sha256()
    with path.open("rb") as fh:
        for chunk in iter(lambda: fh.read(1024 * 1024), b""):
            h.update(chunk)
    return h.hexdigest()


def snapshot_files(base: Path) -> dict[str, str]:
    result: dict[str, str] = {}
    for path in base.rglob("*"):
        if not path.is_file():
            continue
        rel = path.relative_to(base).as_posix()
        parts = set(Path(rel).parts)
        if parts & DEFAULT_EXCLUDE_NAMES:
            continue
        if path.suffix in DEFAULT_EXCLUDE_SUFFIXES:
            continue
        if rel in DEFAULT_EXCLUDE_EXACT:
            continue
        if any(rel.endswith(pattern) for pattern in DEFAULT_EXCLUDE_PATTERNS):
            continue
        result[rel] = sha256_file(path)
    return result


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--old", required=True, type=Path)
    parser.add_argument("--new", required=True, type=Path)
    parser.add_argument("--output", required=True, type=Path)
    args = parser.parse_args()

    old = args.old.resolve()
    new = args.new.resolve()
    old_files = snapshot_files(old)
    new_files = snapshot_files(new)

    added = sorted(set(new_files) - set(old_files))
    deleted = sorted(set(old_files) - set(new_files))
    modified = sorted(k for k in set(old_files) & set(new_files) if old_files[k] != new_files[k])

    lines: list[str] = [
        "# Nexus release diff manifest (2026-07-08)",
        "",
        "Baseline:",
        "",
        f"- Old snapshot: `{old}`",
        f"- New snapshot: `{new}`",
        "",
        "Excluded names/patterns: `.git`, `node_modules`, `.venv-*`, `venv`, `__pycache__`, `.ruff_cache`, `.playwright-mcp`, `.cursor`, `.pytest_cache`, `tmp`, `*.pyc`, `*.pyo`, `*.bak-`, `2025.2`, `=2025.2`.",
        "",
        "## Summary",
        "",
        f"- Added files: {len(added)}",
        f"- Modified files: {len(modified)}",
        f"- Deleted files: {len(deleted)}",
        "",
    ]

    for title, items in (
        ("Added files", added),
        ("Modified files", modified),
        ("Deleted files", deleted),
    ):
        lines.extend([f"## {title}", ""])
        if items:
            lines.extend(f"- `{item}`" for item in items)
        else:
            lines.append("- None")
        lines.append("")

    args.output.parent.mkdir(parents=True, exist_ok=True)
    args.output.write_text("\n".join(lines), encoding="utf-8")
    print(args.output)
    print(f"added={len(added)} modified={len(modified)} deleted={len(deleted)}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())