"""T11 改进候选契约：对照证据、独立审核与发布。

Owner：本文件（docs/v2/03-detailed-design.md §9.4 ImprovementCandidate 与状态机、
docs/v2/14-experience-loop.md §8、06-validation.md §5）。

三条不可让渡的规则：
1. **没有对照证据不能发布**：候选必须带一次冻结版本的旧/新对照，且不是退化
   （AC-34 / 06 §5"未评测、自批、退化均不能发布"）。
2. **自批不算审核**：提交人与审核人必须是不同的人；同模型自评也不能当独立评测
   （AC-41）。
3. **发布是引用不可变版本**：发布只把候选指向一个既有的、不可变的发布结果，
   不允许"标成已发布却没有对应版本"（03 §9.4 末）。
"""

from __future__ import annotations

from typing import Literal

from pydantic import Field, model_validator

from contracts.prescreen import (
    DESC_MAX,
    ID_MAX,
    AwareDatetime,
    Contract,
    DataDomain,
    ErrorCode,
    Ref,
)

CANDIDATE_STATUSES = ("draft", "evaluating", "ready", "in_review", "approved",
                      "rejected", "released", "withdrawn")
TARGETS = ("knowledge", "orchestration", "question_profile")


class ContrastMetrics(Contract):
    """高预测组指标口径（AC-37）：分子、可观察分母、覆盖率与未观察数分开报。

    零分母时必须留空而不是填 0%——"没有样本"与"全都没通过"是两件事。
    """

    label: str = Field(min_length=1, max_length=DESC_MAX)
    numerator: int = Field(ge=0)
    observable_denominator: int = Field(ge=0)
    unobserved: int = Field(ge=0)
    coverage: float | None = Field(default=None, ge=0, le=1)
    rate: float | None = Field(default=None, ge=0, le=1)

    @model_validator(mode="after")
    def _check_metrics(self) -> ContrastMetrics:
        if self.numerator > self.observable_denominator:
            raise ValueError("分子不得大于可观察分母")
        if self.observable_denominator == 0:
            if self.rate is not None or self.coverage is not None:
                raise ValueError("零分母时不得给出比率或覆盖率；样本不足不是 0%")
        elif self.rate is None:
            raise ValueError("有可观察样本时必须给出比率，避免用空白代替结果")
        return self


class ContrastReport(Contract):
    """一次旧/新对照的结果。versions 冻结后才可比较（06 §5）。"""

    id: str = Field(min_length=1, max_length=ID_MAX)
    baseline_ref: Ref
    candidate_ref: Ref
    dataset_ref: str = Field(min_length=1, max_length=DESC_MAX)
    split_ref: str = Field(min_length=1, max_length=DESC_MAX)
    baseline_metrics: list[ContrastMetrics] = Field(default_factory=list, max_length=20)
    candidate_metrics: list[ContrastMetrics] = Field(default_factory=list, max_length=20)
    sample_size: int = Field(ge=0)
    contaminated: list[str] = Field(default_factory=list, max_length=200)
    independent: bool = False
    verdict: Literal["improved", "unchanged", "regressed", "inconclusive"]
    reviewer_id: str | None = Field(default=None, max_length=ID_MAX)
    created_at: AwareDatetime

    @model_validator(mode="after")
    def _check_report(self) -> ContrastReport:
        if self.verdict != "inconclusive" and not self.independent:
            raise ValueError("非独立评测不得给出改进/退化结论，只能记 inconclusive")
        if self.sample_size == 0 and self.verdict == "improved":
            raise ValueError("没有样本不得声称改进")
        return self


class ImprovementCandidate(Contract):
    """改进候选。发布引用既有不可变版本；撤回只影响新运行。"""

    id: str = Field(min_length=1, max_length=ID_MAX)
    project_id: str = Field(min_length=1, max_length=ID_MAX)
    data_domain: DataDomain
    revision: int = Field(ge=1)
    target: Literal["knowledge", "orchestration", "question_profile"]
    target_ref: Ref
    source_run_ids: list[str] = Field(default_factory=list, max_length=200)
    outcome_ids: list[str] = Field(default_factory=list, max_length=200)
    change_summary: str = Field(min_length=1, max_length=DESC_MAX)
    proposed_revision_ref: Ref
    status: Literal["draft", "evaluating", "ready", "in_review", "approved",
                    "rejected", "released", "withdrawn"]
    evaluation_ref: Ref | None = None
    contrast: ContrastReport | None = None
    reviewer_id: str | None = Field(default=None, max_length=ID_MAX)
    released_ref: Ref | None = None
    proposed_by: str = Field(min_length=1, max_length=ID_MAX)
    rejection_reason: str | None = Field(default=None, max_length=DESC_MAX)
    created_at: AwareDatetime

    @model_validator(mode="after")
    def _check_candidate(self) -> ImprovementCandidate:
        if self.status in ("approved", "released") and self.reviewer_id is None:
            raise ValueError("通过审核的候选必须记录审核人")
        if self.status == "released" and self.released_ref is None:
            raise ValueError("已发布必须引用一个既有的不可变发布版本，不得只改状态")
        if self.status == "rejected" and not self.rejection_reason:
            raise ValueError("拒绝必须留下原因")
        if self.status in ("ready", "in_review", "approved", "released") \
                and self.contrast is None:
            raise ValueError("没有对照证据的候选不得进入待审核或已发布状态")
        return self

    def must_not_self_approve(self, actor: str) -> None:
        if actor == self.proposed_by:
            raise PermissionError("改进候选不能由提出者自己审核（自批不算独立审核）")

    def release_blockers(self) -> list[str]:
        """发布前必须为空的阻塞项列表；可读的失败原因，便于界面展示。"""
        blockers = []
        if self.contrast is None:
            blockers.append("缺少旧/新对照证据")
        else:
            if self.contrast.contaminated:
                blockers.append(f"对照样本存在泄漏：{self.contrast.contaminated}")
            if not self.contrast.independent:
                blockers.append("对照不是独立评测（同模型自评不算证据）")
            if self.contrast.verdict == "regressed":
                blockers.append("对照显示退化，不得发布")
            if self.contrast.verdict == "inconclusive":
                blockers.append("对照结论不明确，不得发布")
        if self.status != "approved":
            blockers.append(f"当前状态为 {self.status}，未通过审核")
        return blockers


CONTAMINATION_CODE = ErrorCode.EVALUATION_CONTAMINATED
NOT_VALIDATED_CODE = ErrorCode.IMPROVEMENT_NOT_VALIDATED