"""AST-level logical operator misuse injection for JavaScript using esprima."""

from typing import Optional

import esprima

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


class JSLogicOperatorRule(MutationRule):
    """Swap `&&` with `||` in a boolean expression.

    Uses `esprima` to locate a LogicalExpression using `&&` and replaces the
    operator with `||`.
    """

    name = "js_logic_operator"
    language = "javascript"
    defect_type = "logic_operator_misuse"

    def detect_and_mutate(self, source: str, filename: str = "") -> Optional[Mutation]:
        # Modern JS is usually ESM: try module grammar first, then script.
        try:
            tree = esprima.parseModule(source, loc=True)
        except Exception:
            try:
                tree = esprima.parseScript(source, loc=True)
            except Exception:
                return None

        for node in self._walk(tree):
            if node.type != "LogicalExpression" or node.operator != "&&":
                continue
            line_no = node.loc.start.line
            lines = source.splitlines(keepends=True)
            line = lines[line_no - 1]
            mutated_line = line.replace("&&", "||", 1)
            if mutated_line == line:
                continue
            mutated = "".join(lines[:line_no - 1] + [mutated_line] + lines[line_no:])
            return Mutation(
                defect_type=self.defect_type,
                language=self.language,
                line_start=line_no,
                line_end=line_no,
                mutated_source=mutated,
                reference_fix="Restore `&&` for correct short-circuit logic.",
                description="Replaced boolean `&&` with `||`.",
            )
        return None

    def _walk(self, node):
        yield node
        for key in getattr(node, "__dict__", {}):
            child = getattr(node, key)
            if isinstance(child, list):
                for item in child:
                    if hasattr(item, "type"):
                        yield from self._walk(item)
            elif hasattr(child, "type"):
                yield from self._walk(child)