#!/usr/bin/env python3
"""File each module's known vulnerabilities as one security item atop todo.md's next release.

Usage: file_vulnerabilities.py <govulncheck -format json report> <todo.md>
Exits 1 while any vulnerability is known, filed now or before, and 0 on a clean report.
"""

import ast
import json
import re
import sys
from dataclasses import dataclass, field

ROW = re.compile(r"^\| (\d+) \| ([^|]+?) \| [^|]*\| \*\*", re.M)
WEIGHT = re.compile(r"^\| ([\d.]+) \| ([\d.]+) \|$", re.M)
NEXT_ID = re.compile(r"`Next ID = (\d+)`")
SCORES = {"R": 1, "S": 1, "C": 1, "A": 8, "G": 8}
GOAL = "1.1"


@dataclass
class Module:
	path: str
	found_in: str
	fixed: list[str] = field(default_factory=list)
	osvs: dict[str, dict] = field(default_factory=dict)

	@property
	def name(self) -> str:
		return "Go" if self.path == "stdlib" else f"`{self.path}`"

	def version(self, version: str) -> str:
		return version.removeprefix("v") if self.path == "stdlib" else version

	@property
	def carried(self) -> str:
		return f"{self.name} {self.version(self.found_in)}"


def messages(report: str):
	decoder, at = json.JSONDecoder(), 0
	while at < len(report):
		if report[at].isspace():
			at += 1
			continue
		message, at = decoder.raw_decode(report, at)
		yield message


def vulnerable_modules(report: str) -> list[Module]:
	"""Each module govulncheck found a vulnerability in, Go (stdlib) first, then by path."""
	osvs, modules = {}, {}
	for message in messages(report):
		if "osv" in message:
			osv = message["osv"]
			osvs[osv["id"]] = {"id": osv["id"], "aliases": osv.get("aliases", []), "summary": osv.get("summary", "")}
		elif "finding" in message:
			finding = message["finding"]
			frame = finding["trace"][0]
			module = modules.setdefault(frame["module"], Module(frame["module"], frame["version"]))
			module.osvs[finding["osv"]] = osvs[finding["osv"]]
			module.fixed.append(finding.get("fixed_version", ""))
	return sorted(modules.values(), key=lambda m: (m.path != "stdlib", m.path))


def version_key(version: str):
	return [int(part) for part in re.findall(r"\d+", version)]


def evaluate(node, values):
	match node:
		case ast.Constant(value=value):
			return value
		case ast.Name(id=name):
			return values[name]
		case ast.UnaryOp(op=ast.USub(), operand=operand):
			return -evaluate(operand, values)
		case ast.BinOp(left=left, op=ast.Add(), right=right):
			return evaluate(left, values) + evaluate(right, values)
		case ast.BinOp(left=left, op=ast.Sub(), right=right):
			return evaluate(left, values) - evaluate(right, values)
		case ast.BinOp(left=left, op=ast.Mult(), right=right):
			return evaluate(left, values) * evaluate(right, values)
		case ast.BinOp(left=left, op=ast.Div(), right=right):
			return evaluate(left, values) / evaluate(right, values)
	raise ValueError(f"todo.md's formula holds {ast.dump(node)}, which this script cannot evaluate")


def score(todo: str) -> str:
	formula = re.search(r"`Score = (.+?)`", todo).group(1)
	values = dict(SCORES, W=float(dict(WEIGHT.findall(todo))[GOAL]))
	return f"{evaluate(ast.parse(formula, mode='eval').body, values):.1f}"


def tagline(module: Module) -> str:
	if "" in module.fixed:
		return f"Ship no release while fejkdata carries {module.carried}, some of whose known vulnerabilities no version fixes yet."
	fixed = module.version(max(module.fixed, key=version_key))
	if module.path == "stdlib":
		return f"Raise Go to {fixed}, so the release binaries carry none of {module.carried}'s known vulnerabilities."
	return f"Raise {module.name} to {fixed}, so fejkdata requires no version of it with a known vulnerability."


def detail(module: Module) -> str:
	lines = []
	for osv in sorted(module.osvs.values(), key=lambda o: o["id"]):
		aliases = f" ({', '.join(osv['aliases'])})" if osv["aliases"] else ""
		summary = f": {osv['summary']}" if osv["summary"] else ""
		lines.append(f"- {osv['id']}{aliases}{summary}")
	return f"govulncheck found these in {module.carried}:\n\n" + "\n".join(lines) + "\n"


def file_items(modules: list[Module], todo: str) -> tuple[str, list[int]]:
	"""Return todo.md with an item for each module whose vulnerabilities it does not yet name, and the items' IDs."""
	filed = []
	for module in modules:
		if all(osv in todo for osv in module.osvs):
			continue
		first = ROW.search(todo)
		if first is None:
			raise ValueError("todo.md has no item to take the next release from")
		next_id = int(NEXT_ID.search(todo).group(1))
		line = tagline(module)
		scores = " | ".join(str(SCORES[k]) for k in "RSCAG")
		row = f"| {next_id} | {first.group(2)} | security | **{line}** | {scores} | {GOAL} | {score(todo)} |\n"
		todo = todo[: first.start()] + row + todo[first.start() :]
		todo = todo.replace(f"`Next ID = {next_id}`", f"`Next ID = {next_id + 1}`", 1)
		todo = todo.replace("## Details\n\n", f"## Details\n\n### {next_id}. {line}\n\n{detail(module)}\n", 1)
		filed.append(next_id)
	return todo, filed


def main(argv: list[str]) -> int:
	report_path, todo_path = argv
	with open(report_path, encoding="utf-8") as f:
		modules = vulnerable_modules(f.read())
	if not modules:
		print("No known vulnerabilities.")
		return 0
	count = sum(len(m.osvs) for m in modules)
	known = f"{count} known {'vulnerability' if count == 1 else 'vulnerabilities'}"
	with open(todo_path, encoding="utf-8") as f:
		todo, filed = file_items(modules, f.read())
	if not filed:
		print(f"{known}, already planned in todo.md.")
		return 1
	with open(todo_path, "w", encoding="utf-8") as f:
		f.write(todo)
	items = ", ".join(map(str, filed))
	print(f"{known}; todo.md {'item ' + items + ' plans' if len(filed) == 1 else 'items ' + items + ' plan'} the fix.")
	return 1


if __name__ == "__main__":
	sys.exit(main(sys.argv[1:]))