from enum import Enum
from typing import Optional

from pydantic import BaseModel, Field, model_validator


class ChangeOp(str, Enum):
    CREATE = "create"
    UPDATE = "update"
    DELETE = "delete"


class ChangeItem(BaseModel):
    op: ChangeOp
    path: str = Field(min_length=1)
    base_hash: Optional[str] = None
    proposed_content: Optional[str] = None
    reason: str = Field(min_length=1, max_length=500)

    @model_validator(mode="after")
    def validate_op_fields(self) -> "ChangeItem":
        if self.op in (ChangeOp.UPDATE, ChangeOp.DELETE) and not self.base_hash:
            raise ValueError("base_hash is required for update/delete")
        if self.op in (ChangeOp.CREATE, ChangeOp.UPDATE) and self.proposed_content is None:
            raise ValueError("proposed_content is required for create/update")
        if self.op == ChangeOp.DELETE and self.proposed_content is not None:
            raise ValueError("proposed_content is forbidden for delete")
        return self


class ChangeSetPayload(BaseModel):
    schema_version: str
    task_id: str
    changeset: list[ChangeItem]