"""Fin-hub reporting allocation of a booked AI-plan fact onto work."""

from __future__ import annotations

from datetime import date
from decimal import Decimal
from typing import Literal

from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator

from fin_hub.money import money

REPORTING_METHODS = (
    "measured_token_share",
    "measured_estimated_token_share",
    "session_count_share",
    "even_split",
)


class ReportingAllocationShare(BaseModel):
    model_config = ConfigDict(extra="forbid")

    target_key: str = Field(min_length=1, max_length=256)
    share: Decimal = Field(ge=0, le=1)
    driver_value: int = Field(ge=0)

    @field_validator("share", mode="before")
    @classmethod
    def validate_share(cls, value):
        return money(value, non_negative=True)


class ReportingAllocation(BaseModel):
    """Local reporting allocation. Not resource-control AllocationEvidence."""

    model_config = ConfigDict(extra="forbid")

    schema_version: Literal["0.1"] = "0.1"
    record_type: Literal["reporting_allocation"] = "reporting_allocation"
    record_id: str = Field(min_length=1, max_length=256)
    revision_of: str | None = None
    financial_fact_id: str = Field(min_length=1)
    method: Literal[
        "measured_token_share",
        "measured_estimated_token_share",
        "session_count_share",
        "even_split",
    ]
    estimator_version: str = Field(min_length=1, max_length=64)
    session_token_record_id: str | None = None
    period_start: date
    period_end: date
    currency: str
    booked_amount: Decimal
    shares: list[ReportingAllocationShare]
    residual_share: Decimal = Field(ge=0, le=1)
    residual_reason: Literal["none", "unmeasured", "unattributed", "no_targets"]
    source_evidence: list[str] = Field(min_length=1)

    @field_validator("booked_amount", "residual_share", mode="before")
    @classmethod
    def validate_money_fields(cls, value):
        return money(value, non_negative=True)

    @model_validator(mode="after")
    def validate_shares(self) -> "ReportingAllocation":
        keys = [share.target_key for share in self.shares]
        if len(set(keys)) != len(keys):
            raise ValueError("reporting allocation target keys must be unique")
        total = sum((share.share for share in self.shares), Decimal("0.00"))
        if total + self.residual_share != Decimal("1.00"):
            raise ValueError("allocation shares plus residual_share must equal 1")
        if self.residual_share == Decimal("0.00") and self.residual_reason != "none":
            raise ValueError("zero residual must use residual_reason=none")
        if self.residual_share > Decimal("0.00") and self.residual_reason == "none":
            raise ValueError("nonzero residual requires a residual_reason")
        return self