#!/usr/bin/env python3
"""
Claude Code PostToolUse hook — blocks new `print(` calls in backend/**/*.py.

Wired in `.claude/settings.json` hooks.PostToolUse with matcher
"Edit|Write|MultiEdit".

Behavior:
- Reads hook input as JSON from stdin (per Anthropic spec).
- If tool is Edit/Write/MultiEdit and file_path matches backend/**/*.py:
    - Scans new content for new `print(` calls.
    - Exits with code 2 to block (stderr is forwarded to Claude as feedback).
- Otherwise exits 0 (no-op).

Notes:
- Allows `print(` inside lines containing `# noqa` (escape hatch).
- Skips files under `backend/tests/**` (test code may use print for debugging).
- Skips `backend/scripts/**` (one-off scripts).
"""

from __future__ import annotations

import json
import re
import sys
from pathlib import Path

ALLOW_PATH_PREFIXES = (
    "backend/tests/",
    "backend/scripts/",
)
WATCH_PATH_PREFIX = "backend/"
# Lookbehind `(?<![\w.])` rejects both word-char prefixes (e.g. `endprint(`)
# and method calls (e.g. `self.print(`, `logger.print(`), which are not the
# builtin `print`.
PRINT_RE = re.compile(r"(?<![\w.])print\s*\(")


def normalize_path(raw: str) -> str:
    """Convert absolute/relative path to repo-relative POSIX-like form."""
    parts = Path(raw).parts
    # Match the repo-root segment "backend" exactly (not a substring like
    # "services-backend"), and anchor on the FIRST such segment so a nested
    # "backend" dir does not drop the leading path components.
    try:
        idx = parts.index("backend")
    except ValueError:
        return Path(raw).as_posix()
    return Path(*parts[idx:]).as_posix()


def main() -> int:
    try:
        payload = json.load(sys.stdin)
    except Exception:
        # No input or malformed — skip silently.
        return 0

    tool_name = payload.get("tool_name") or payload.get("tool") or ""
    if tool_name not in {"Edit", "Write", "MultiEdit"}:
        return 0

    tool_input = payload.get("tool_input") or {}
    file_path = tool_input.get("file_path") or tool_input.get("path") or ""
    if not file_path:
        return 0

    norm = normalize_path(file_path)
    if not norm.startswith(WATCH_PATH_PREFIX):
        return 0
    if any(norm.startswith(p) for p in ALLOW_PATH_PREFIXES):
        return 0
    if not norm.endswith(".py"):
        return 0

    # Pull the new content. Edit gives `new_string`, Write gives `content`,
    # MultiEdit gives an `edits` array of `{old_string, new_string}` entries.
    edits = tool_input.get("edits")
    if isinstance(edits, list):
        new_text = "\n".join(
            str(e.get("new_string") or "")
            for e in edits
            if isinstance(e, dict)
        )
    else:
        new_text = tool_input.get("new_string") or tool_input.get("content") or ""
    if not new_text:
        return 0

    offenders: list[tuple[int, str]] = []
    for lineno, line in enumerate(new_text.splitlines(), start=1):
        if "# noqa" in line:
            continue
        # Skip whole-line comments (e.g. `# print(debug)`); regex on raw
        # lines cannot see the surrounding syntax otherwise.
        if line.lstrip().startswith("#"):
            continue
        if PRINT_RE.search(line):
            offenders.append((lineno, line.strip()))

    if not offenders:
        return 0

    sample = offenders[0]
    msg_lines = [
        f"Blocked: `print(` introduced in {norm}.",
        f"Line {sample[0]}: {sample[1][:120]}",
        "GenDesign convention: use `logger.info/warning/error` instead of print().",
        "If this is intentional one-off debug, add `# noqa` on the line and retry.",
    ]
    print("\n".join(msg_lines), file=sys.stderr)
    return 2


if __name__ == "__main__":
    sys.exit(main())
