from __future__ import annotations
from dataclasses import dataclass, field
from typing import Optional


@dataclass
class Field:
    name: str
    level: int
    pic: str
    usage: str = "DISPLAY"
    offset: int = 0
    length: int = 0
    decimal: int = 0
    signed: bool = False
    sign_separate: bool = False
    occurs: Optional[int] = None
    occurs_max: Optional[int] = None
    redefines: Optional[str] = None
    redefines_variant: Optional[str] = None
    conditions: list[dict] = field(default_factory=list)
    children: list["Field"] = field(default_factory=list)


@dataclass
class FieldTree:
    fields: list[Field] = field(default_factory=list)
    copybook_name: str = ""
    sha256: str = ""

    def flatten(self) -> dict[str, Field]:
        result = {}
        def _walk(ff):
            for f in ff:
                result[f.name] = f
                _walk(f.children)
        _walk(self.fields)
        return result

    def get_by_name(self, name: str) -> Optional[Field]:
        return self.flatten().get(name)

    @classmethod
    def from_list(cls, fields: list[Field], name: str = "") -> "FieldTree":
        return cls(fields=fields, copybook_name=name)


_f = Field(name="BR-AMT", level=5, pic="S9(7)V99", usage="COMP-3", offset=0, length=5, decimal=2, signed=True)
assert _f.name == "BR-AMT"
assert _f.decimal == 2
assert _f.signed

_ft = FieldTree(fields=[_f], copybook_name="BILLCPY")
assert "BR-AMT" in _ft.flatten()
assert _ft.get_by_name("BR-AMT") is _f