from datetime import datetime
from typing import Literal

from pydantic import BaseModel, Field, ConfigDict


# Stub locale di _YamlModel (in the reference implementation vive in mschema/models.py).
# Qui serve solo come base con populate_by_name; mschema/ sara' portato nel Task A9.
class _YamlModel(BaseModel):
    model_config = ConfigDict(populate_by_name=True)


class SessionManifest(_YamlModel):
    id: str
    created_at: datetime
    status: Literal["open", "closed", "finalized"] = "open"
    question: str
    database: str
    db_schema: str = Field(alias="schema")
    # D12/D15: autore della sessione (auth) e versione del workflow usato.
    author: str | None = None
    summary: str | None = None
    updated_at: datetime | None = None
    updated_by: str | None = None
    schema_version: int | None = None


class Candidate(BaseModel):
    kind: Literal["table", "column"]
    name: str
    signals: dict = {}
    evidence: list[str] = []
    decision: Literal["promoted", "excluded", "pending"] = "pending"
    decision_seq: int | None = None
    # D14a: valori citati nella domanda ancorati a questa colonna/tabella.
    grounded_values: list[dict] = []


class Join(BaseModel):
    from_: str = Field(alias="from")
    to: str
    source: str = ""
    decision: Literal["promoted", "excluded", "pending"] = "promoted"
    decision_seq: int | None = None

    model_config = {"populate_by_name": True}


class ExcludedItem(BaseModel):
    kind: Literal["table", "column"]
    name: str
    decision_seq: int | None = None


class SchemaLinking(BaseModel):
    question: str
    candidates: list[Candidate] = []
    joins: list[Join] = []
    excluded: list[ExcludedItem] = []
    open_questions: list[str] = []
    # D14b: formule di concetto approvate, parte dello schema-linking.
    concept_formulas: list[dict] = []

    model_config = {"extra": "forbid"}