"""Failure classifier for agent step errors.

Maps (step_kind, error_text) → FailureClass.
Used by retry_policy to decide whether and how to retry.
"""
from __future__ import annotations

from enum import Enum


class FailureClass(str, Enum):
    SECURITY_DENIED = "security_denied"   # blocked by security policy
    TEMPLATE_ERROR  = "template_error"    # {{ }} resolution failed
    FILE_ERROR      = "file_error"        # file not found / path error
    EXECUTION_ERROR = "execution_error"   # subprocess failure / transient
    UNKNOWN_ERROR   = "unknown_error"     # catch-all


def classify(step_kind: str, error: str) -> FailureClass:
    """Classify a step failure from its kind and error message."""
    if not error:
        return FailureClass.UNKNOWN_ERROR

    err = error.lower()

    # Security policy rejections — cannot be retried
    if "blocked by security policy" in err or "is not in allowlist" in err:
        return FailureClass.SECURITY_DENIED

    # Template resolution failures — logic errors, cannot be retried
    if "template resolution failed" in err or "could not be resolved" in err:
        return FailureClass.TEMPLATE_ERROR

    # File system errors — may be transient (e.g. write race), limited retry
    if step_kind in ("write_file", "read_file"):
        if any(kw in err for kw in ("not found", "path traversal", "missing 'path'", "no such file")):
            return FailureClass.FILE_ERROR

    # Explicit execution_error tag (used by flaky test tool)
    if err.startswith("execution_error"):
        return FailureClass.EXECUTION_ERROR

    # Shell non-zero exit or binary not found
    if step_kind == "shell" and any(kw in err for kw in ("non-zero exit code", "not found on path", "timed out")):
        return FailureClass.EXECUTION_ERROR

    return FailureClass.UNKNOWN_ERROR