"""Candidate construction for constrained classification prompts."""

from __future__ import annotations

from pydantic import BaseModel, ConfigDict, Field

from gcmd_classifier.llm.prompts import PromptCandidate
from gcmd_classifier.models import CanonicalConceptRecord
from gcmd_classifier.vocabulary.index import VocabularyIndex


class TopicCandidate(BaseModel):
    """Application candidate for one UUID-bearing GCMD Topic."""

    model_config = ConfigDict(extra="forbid", frozen=True)

    candidate_id: str = Field(min_length=1)
    topic_uuid: str = Field(min_length=1)
    prompt_candidate: PromptCandidate

    @property
    def record_uuid(self) -> str:
        """Authoritative UUID for the candidate's Topic record."""
        return self.topic_uuid


class TermCandidate(BaseModel):
    """Application candidate for one direct Term beneath a selected Topic."""

    model_config = ConfigDict(extra="forbid", frozen=True)

    candidate_id: str = Field(min_length=1)
    topic_uuid: str = Field(min_length=1)
    term_uuid: str = Field(min_length=1)
    prompt_candidate: PromptCandidate

    @property
    def record_uuid(self) -> str:
        """Authoritative UUID for the candidate's Term record."""
        return self.term_uuid


class VariableCandidate(BaseModel):
    """Application candidate for one direct Variable child beneath a selected parent."""

    model_config = ConfigDict(extra="forbid", frozen=True)

    candidate_id: str = Field(min_length=1)
    parent_uuid: str = Field(min_length=1)
    variable_uuid: str = Field(min_length=1)
    prompt_candidate: PromptCandidate

    @property
    def record_uuid(self) -> str:
        """Authoritative UUID for the candidate's Variable record."""
        return self.variable_uuid


def build_topic_candidates(index: VocabularyIndex) -> tuple[TopicCandidate, ...]:
    """Build deterministic prompt candidates from UUID-bearing Topic records only."""
    candidates: list[TopicCandidate] = []
    for position, topic in enumerate(index.topics(), start=1):
        _validate_topic_record(topic)
        candidate_id = f"topic_{position:04d}"
        candidates.append(
            TopicCandidate(
                candidate_id=candidate_id,
                topic_uuid=topic.UUID,
                prompt_candidate=PromptCandidate(
                    candidate_id=candidate_id,
                    name=topic.name,
                    level=topic.level,
                    definition=topic.definition,
                    canonical_path=topic.canonical_path,
                ),
            )
        )
    return tuple(candidates)


def build_term_candidates(
    index: VocabularyIndex,
    *,
    topic_uuid: str,
) -> tuple[TermCandidate, ...]:
    """Build deterministic prompt candidates from direct Term children of one Topic."""
    topic = index.get(topic_uuid)
    _validate_topic_record(topic)
    candidates: list[TermCandidate] = []
    for position, term in enumerate(index.terms_for_topic(topic_uuid), start=1):
        _validate_term_record(term, topic_uuid=topic_uuid, index=index)
        candidate_id = f"term_{position:04d}"
        candidates.append(
            TermCandidate(
                candidate_id=candidate_id,
                topic_uuid=topic_uuid,
                term_uuid=term.UUID,
                prompt_candidate=PromptCandidate(
                    candidate_id=candidate_id,
                    name=term.name,
                    level=term.level,
                    definition=term.definition,
                    canonical_path=term.canonical_path,
                    parent_context=topic.canonical_path,
                ),
            )
        )
    return tuple(candidates)


def build_variable_candidates(
    index: VocabularyIndex,
    *,
    parent_uuid: str,
) -> tuple[VariableCandidate, ...]:
    """Build deterministic prompt candidates from direct Variable children of one parent."""
    parent = index.get(parent_uuid)
    _validate_variable_parent_record(parent)
    candidates: list[VariableCandidate] = []
    for position, variable in enumerate(index.variables_for_parent(parent_uuid), start=1):
        _validate_variable_child_record(variable, parent_uuid=parent_uuid, index=index)
        candidate_id = f"variable_{position:04d}"
        candidates.append(
            VariableCandidate(
                candidate_id=candidate_id,
                parent_uuid=parent_uuid,
                variable_uuid=variable.UUID,
                prompt_candidate=PromptCandidate(
                    candidate_id=candidate_id,
                    name=variable.name,
                    level=variable.level,
                    definition=variable.definition,
                    canonical_path=variable.canonical_path,
                    parent_context=parent.canonical_path,
                ),
            )
        )
    return tuple(candidates)


def validate_variable_candidate_relationship(
    candidate: VariableCandidate,
    *,
    selected_parent_uuid: str,
    index: VocabularyIndex,
) -> None:
    """Validate that a Variable candidate is a direct child of the selected parent."""
    if candidate.parent_uuid != selected_parent_uuid:
        raise ValueError(
            f"Variable candidate {candidate.candidate_id!r} was built for parent "
            f"{candidate.parent_uuid!r}, not selected parent {selected_parent_uuid!r}."
        )
    variable = index.get(candidate.variable_uuid)
    _validate_variable_child_record(variable, parent_uuid=selected_parent_uuid, index=index)


def validate_term_candidate_relationship(
    candidate: TermCandidate,
    *,
    selected_topic_uuid: str,
    index: VocabularyIndex,
) -> None:
    """Validate that a Term candidate is a direct child of the selected Topic."""
    if candidate.topic_uuid != selected_topic_uuid:
        raise ValueError(
            f"Term candidate {candidate.candidate_id!r} was built for Topic "
            f"{candidate.topic_uuid!r}, not selected Topic {selected_topic_uuid!r}."
        )
    term = index.get(candidate.term_uuid)
    _validate_term_record(term, topic_uuid=selected_topic_uuid, index=index)


def _validate_topic_record(record: CanonicalConceptRecord) -> None:
    if record.level != "Topic":
        raise ValueError(f"Expected Topic record, got {record.level!r} for {record.UUID!r}.")
    if not record.UUID:
        raise ValueError(f"Topic record {record.name!r} does not have a UUID.")


def _validate_term_record(
    record: CanonicalConceptRecord,
    *,
    topic_uuid: str,
    index: VocabularyIndex,
) -> None:
    if record.level != "Term":
        raise ValueError(f"Expected Term record, got {record.level!r} for {record.UUID!r}.")
    if not record.UUID:
        raise ValueError(f"Term record {record.name!r} does not have a UUID.")
    if index.parent_of(record.UUID) != topic_uuid:
        raise ValueError(f"Term {record.UUID!r} is not a direct child of Topic {topic_uuid!r}.")


def _validate_variable_parent_record(record: CanonicalConceptRecord) -> None:
    if record.level not in {"Term", "Variable_Level_1", "Variable_Level_2"}:
        raise ValueError(
            f"Expected Term or Variable parent, got {record.level!r} for {record.UUID!r}."
        )
    if not record.UUID:
        raise ValueError(f"Variable parent record {record.name!r} does not have a UUID.")


def _validate_variable_child_record(
    record: CanonicalConceptRecord,
    *,
    parent_uuid: str,
    index: VocabularyIndex,
) -> None:
    if record.level not in {"Variable_Level_1", "Variable_Level_2", "Variable_Level_3"}:
        raise ValueError(f"Expected Variable record, got {record.level!r} for {record.UUID!r}.")
    if not record.UUID:
        raise ValueError(f"Variable record {record.name!r} does not have a UUID.")
    if index.parent_of(record.UUID) != parent_uuid:
        raise ValueError(
            f"Variable {record.UUID!r} is not a direct child of parent {parent_uuid!r}."
        )