#!/usr/bin/env python3
"""
verify-collision-detection.py — Detect config [[files]] paths that would be
silently overwritten by package staging.

AGENTS.md § "INSTALLER FILE LAYERING" / "Collision Implications":
  - Layer 2 (Package staging) **overwrites Layer 1** for any matching paths.
  - The init system's config_for_dirs() gives /etc/init.d/ priority
    over /usr/lib/init.d/ for the same filename, so config overrides
    must use /etc/.
  - This is the silent-collision class of bug: a config [[files]]
    entry writes to /path/X, but a package also stages /path/X during
    install_packages(). Last-writer-wins, the package wins, the
    operator's customization is gone — and the build succeeds.

This script parses:
  1. Every recipes/<cat>/<pkg>/recipe.toml with an `[[package]] installs = [...]`
     field — these are the files that the package WILL install at build time.
  2. Every config/redbear-*.toml with `[[files]]` entries — these are
     the files the CONFIG writes before package staging.

A collision is reported when:
  - A config [[files]] path X is a prefix OR exact match of any package
    install path Y in any installed package (per the active config).
  - The path is NOT a known-safe override (/etc/init.d/* and similar
    config-path conventions).

Per AGENTS.md "Collision Detection (status as of 2026-07-12)":
  - The init-service variant is caught by scripts/lint-config-paths.sh.
  - The general package-vs-config variant was not implemented.
This script implements the general variant.

Output: human-readable report per config; non-zero exit on strict mode.
"""

import argparse
import os
import re
import sys
import tomllib
from pathlib import Path

ROOT = Path(__file__).resolve().parent.parent.parent
os.chdir(ROOT)

def parse_recipe_installs(recipe_path: Path):
    """Return list of (recipe_path, install_path) tuples from one recipe.toml."""
    try:
        with open(recipe_path, 'rb') as f:
            data = tomllib.load(f)
    except Exception:
        return []
    installs = []
    pkg = data.get('package', {})
    for path in pkg.get('installs', []):
        installs.append((str(recipe_path), str(path)))
    return installs

def collect_all_recipe_installs():
    """Walk all recipes/ for [[package]] installs fields."""
    installs = []
    for rdir in (ROOT / 'recipes', ROOT / 'local' / 'recipes'):
        if not rdir.is_dir():
            continue
        for path in rdir.rglob('recipe.toml'):
            if 'source' in path.parts or 'target' in path.parts or '/absorbed' in str(path):
                continue
            for r, p in parse_recipe_installs(path):
                installs.append((r, p))
    return installs

def parse_config_files(config_path: Path):
    """Return list of (config_path, target_path, line_num) for [[files]] entries."""
    files = []
    try:
        with open(config_path, 'rb') as f:
            text = f.read().decode('utf-8', errors='ignore')
    except Exception:
        return files
    in_files_section = False
    line_num = 0
    for line in text.split('\n'):
        line_num += 1
        if re.match(r'^\[\[files\]\]', line):
            in_files_section = True
            continue
        elif re.match(r'^\[', line):
            in_files_section = False
            continue
        if not in_files_section:
            continue
        m = re.match(r'\s*path\s*=\s*["\']([^"\']+)["\']', line)
        if m:
            files.append((str(config_path), m.group(1), line_num))
    return files

def collect_all_config_files():
    files = []
    cfgdir = ROOT / 'config'
    if not cfgdir.is_dir():
        return files
    for path in cfgdir.glob('redbear-*.toml'):
        for c, p, ln in parse_config_files(path):
            files.append((c, p, ln))
    return files

def is_safe_override(path, install_path):
    """True if config path is a known-safe override of install path.

    /etc/init.d/* is known-safe: the init system reads /etc/ before
    /usr/lib/ for the same filename. Same for /etc/environment.d/.

    Other safe overrides are tracked by AGENTS.md "Init Service File
    Ownership" rules.
    """
    # /etc/init.d/... overrides /usr/lib/init.d/...
    if path.startswith('/etc/init.d/') and install_path.startswith('/usr/lib/init.d/'):
        return True
    # /etc/environment.d/ overrides /usr/lib/environment.d/
    if path.startswith('/etc/environment.d/') and install_path.startswith('/usr/lib/environment.d/'):
        return True
    return False

def main():
    ap = argparse.ArgumentParser()
    ap.add_argument('config', nargs='*', default=[], help='Specific config files to check')
    ap.add_argument('--strict', action='store_true', help='Exit 1 on any collision')
    ap.add_argument('--report', choices=['summary', 'detail'], default='summary')
    ap.add_argument('--quiet', '-q', action='store_true')
    args = ap.parse_args()

    recipe_installs = collect_all_recipe_installs()
    config_files = collect_all_config_files()

    if args.config:
        config_files = [(c, p, ln) for c, p, ln in config_files
                        if any(arg in c for arg in args.config)]

    if not args.quiet:
        print('=' * 70)
        print('  Red Bear OS — Package-vs-Config Collision Detection')
        print('=' * 70)
        print(f'  Recipe installs surveyed: {len(recipe_installs)}')
        print(f'  Config [[files]] entries: {len(config_files)}')
        print('=' * 70)

    collisions = []
    for cf, cfg_path, line_num in config_files:
        for rec, inst_path in recipe_installs:
            # exact match
            if cfg_path == inst_path:
                if is_safe_override(cfg_path, inst_path):
                    continue
                collisions.append((cf, cfg_path, line_num, rec, inst_path, 'exact-match'))
            # cfg is parent of inst (e.g. /etc/foo vs /etc/foo/bar)
            elif inst_path.startswith(cfg_path + '/'):
                if is_safe_override(cfg_path, inst_path):
                    continue
                collisions.append((cf, cfg_path, line_num, rec, inst_path, 'parent-dir'))

    if not args.quiet:
        print(f'\n  Total collisions: {len(collisions)}')
        print()
    if args.report == 'detail' and collisions:
        for cf, cfg_path, ln, rec, inst_path, kind in collisions[:50]:
            print(f'  COLLISION: {kind}')
            print(f'    config:    {cf}:{ln}')
            print(f'    target:    {cfg_path}')
            print(f'    recipe:    {rec}')
            print(f'    install:   {inst_path}')
            print()

    if not args.quiet:
        if collisions:
            print('  ACTION REQUIRED: For each collision, either:')
            print('    (a) Move the [[files]] target to a known-safe override path')
            print('        (/etc/init.d/*, /etc/environment.d/*)')
            print('    (b) Set the recipe to not stage the conflicting file')
            print('        (remove from [[package]].installs)')
            print('    (c) Add a [path.collision.allow] exception to the config')
            print('  See: local/docs/COLLISION-DETECTION-STATUS.md')
        else:
            print('  NO COLLISIONS — all config [[files]] paths are safe')

    if args.strict and collisions:
        return 1
    return 0

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