#!/usr/bin/env python3
"""Fuzz dm/tools/romfs.py's Image, the reader of a DMROMFS1 RomFS image (romfs_image.py packs it; the tools read an extraction's RomFS.img through it).
Seeds: small trees packed by romfs_image.pack from a scratch folder (nested folders, empty files and folders, names that sort byte-wise).
Clean rejection: Image() raises ValueError (its header, entry, name, tree and sort checks). An image it accepts must hold to what those checks promise, which the harness asserts:
every entry is reachable once from the root, find() returns each entry by its path (the binary search needs sorted names) and every file range lies inside the image.
Any other exception, or a broken promise, is a finding. Usage: see fuzzlib.py"""
import os
from pathlib import Path
import sys
import tempfile

import fuzzlib
import romfs
import romfs_image

HARNESS = 'romfs'


def seeds():
    out = {}
    trees = {'flat': {'a': b'one', 'b': b'', 'c': b'three' * 9},
             'nested': {'Data': {'archive': b'\x03\x02\x23\x07' * 8, 'empty': {}, 'z': {'deep': {'file.bin': b'x'}}}, 'A': b'upper', 'a': b'lower', 'top': b'top'},
             'empty': {}}
    with tempfile.TemporaryDirectory() as t:
        for name, tree in trees.items():
            src = Path(t, name); src.mkdir()
            def make(d, node):
                for k, v in node.items():
                    if isinstance(v, dict): (d / k).mkdir(); make(d / k, v)
                    else: (d / k).write_bytes(v)
            make(src, tree)
            romfs_image.pack(src, Path(t, name + '.img')); out[name] = Path(t, name + '.img').read_bytes()
    return out


_file = fuzzlib.InputFile('RomFS.img')


def check(data):
    p = _file.write(data)
    try: img = romfs.Image(p)
    except ValueError: return   # the declared rejection
    size, seen, todo = os.path.getsize(p), {0}, [(0, '')]
    while todo:
        k, path = todo.pop()
        a, b, _, _, t, _ = img.entry(k)
        if path and img.find(path) != k: raise fuzzlib.broken('romfs.py:Image', f'find({path!r}) does not return entry {k}')
        if t:
            if a + b > size: raise fuzzlib.broken('romfs.py:Image', f'entry {k}: file range {a:#x}+{b:#x} past the image end {size:#x}')
            continue
        for name, j in img.children(k):
            if j in seen: raise fuzzlib.broken('romfs.py:Image', f'entry {j} is reached twice')
            seen.add(j); todo.append((j, f'{path}/{name}' if path else name))
    if len(seen) != img.count: raise fuzzlib.broken('romfs.py:Image', f'{img.count - len(seen)} entries are not reachable from the root')


if __name__ == '__main__':
    sys.exit(fuzzlib.main(HARNESS, check, seeds))