"""AST-level resource leak injection for Java using javalang."""

from typing import Optional

import javalang

from app.dataset.rules.base import Mutation, MutationRule


class JavaResourceLeakRule(MutationRule):
    """Replace try-with-resources with a plain try block, leaking the resource.

    Uses `javalang` to locate a try-with-resources statement and removes the
    resource specification, leaving the stream unclosed.
    """

    name = "java_resource_leak"
    language = "java"
    defect_type = "resource_not_closed"

    def detect_and_mutate(self, source: str, filename: str = "") -> Optional[Mutation]:
        try:
            tree = javalang.parse.parse(source)
        except Exception:
            return None

        for path, node in tree:
            if not isinstance(node, javalang.tree.TryStatement):
                continue
            if not node.resources:
                continue
            pos = node.position
            if not pos:
                continue
            lines = source.splitlines(keepends=True)
            start = pos.line
            # Find the resource clause line e.g. try (BufferedReader br = ...)
            resource_line = lines[start - 1]
            new_header = resource_line.split("(", 1)[0].rstrip() + " {\n"
            mutated = "".join(lines[: start - 1] + [new_header] + lines[start:])
            return Mutation(
                defect_type=self.defect_type,
                language=self.language,
                line_start=start,
                line_end=start,
                mutated_source=mutated,
                reference_fix="Use try-with-resources or explicitly close the stream in finally.",
                description="Removed try-with-resources, leaking the acquired resource.",
            )
        return None