"""Canonical dialogue lineage (message-grade provenance) for memory, story, chapter, eval."""

from __future__ import annotations

from typing import Any, Sequence

from pydantic import BaseModel, Field, field_validator

LINEAGE_SCHEMA_VERSION = 1


class DialogueTurnRef(BaseModel):
    """One interview beat: user message paired with assistant reply (if any)."""

    user_message_id: str
    assistant_message_id: str | None = None


class DialogueLineage(BaseModel):
    """
    Multi-turn provenance. `turns` order is chronological within the contributing slice.
    """

    schema_version: int = Field(default=LINEAGE_SCHEMA_VERSION, ge=1)
    conversation_id: str
    turns: list[DialogueTurnRef] = Field(default_factory=list)
    primary_user_message_id: str | None = None
    segment_ids: list[str] = Field(default_factory=list)

    @field_validator("turns")
    @classmethod
    def _non_empty_user_ids(cls, v: list[DialogueTurnRef]) -> list[DialogueTurnRef]:
        for t in v:
            if not (t.user_message_id or "").strip():
                raise ValueError("turn.user_message_id must be non-empty")
        return v

    def model_dump_json_safe(self) -> dict[str, Any]:
        return self.model_dump(mode="json")

    @classmethod
    def for_single_turn(
        cls,
        *,
        conversation_id: str,
        user_message_id: str,
        assistant_message_id: str | None,
        segment_ids: list[str] | None = None,
    ) -> DialogueLineage:
        return cls(
            conversation_id=conversation_id,
            turns=[
                DialogueTurnRef(
                    user_message_id=user_message_id,
                    assistant_message_id=assistant_message_id,
                )
            ],
            primary_user_message_id=user_message_id,
            segment_ids=list(segment_ids or []),
        )


def parse_dialogue_lineage(raw: Any) -> DialogueLineage | None:
    if raw is None:
        return None
    if isinstance(raw, DialogueLineage):
        return raw
    if not isinstance(raw, dict):
        return None
    try:
        return DialogueLineage.model_validate(raw)
    except Exception:
        return None


def primary_user_message_id_from_lineage(raw: Any) -> str | None:
    ln = parse_dialogue_lineage(raw)
    if ln is None:
        return None
    if ln.primary_user_message_id:
        return ln.primary_user_message_id
    if ln.turns:
        return ln.turns[0].user_message_id
    return None


def merge_dialogue_lineages(
    lineages: Sequence[DialogueLineage | dict | None],
    *,
    conversation_id: str,
    segment_ids_ordered: list[str] | None = None,
) -> DialogueLineage | None:
    """Ordered union of turns; dedupe by user_message_id (first occurrence wins)."""
    turns_out: list[DialogueTurnRef] = []
    seen_user: set[str] = set()
    segments_accum: list[str] = []

    for raw in lineages:
        ln = parse_dialogue_lineage(raw)
        if ln is None:
            continue
        for sid in ln.segment_ids:
            if sid and sid not in segments_accum:
                segments_accum.append(sid)
        for t in ln.turns:
            uid = t.user_message_id.strip()
            if not uid or uid in seen_user:
                continue
            seen_user.add(uid)
            turns_out.append(
                DialogueTurnRef(
                    user_message_id=uid,
                    assistant_message_id=t.assistant_message_id,
                )
            )

    if segment_ids_ordered:
        for sid in segment_ids_ordered:
            if sid and sid not in segments_accum:
                segments_accum.append(sid)

    if not turns_out:
        return None

    return DialogueLineage(
        conversation_id=conversation_id,
        turns=turns_out,
        primary_user_message_id=turns_out[0].user_message_id,
        segment_ids=segments_accum,
    )


def aggregate_lineage_from_segments(
    segments: Sequence[Any],
    *,
    conversation_id_fallback: str | None = None,
) -> dict[str, Any] | None:
    """
    Build merged lineage dict from ORM segments (expects .id, .conversation_id,
    .lineage_json, optional .user_message_id).
    """
    if not segments:
        return None
    conv0 = (
        conversation_id_fallback or getattr(segments[0], "conversation_id", None) or ""
    )
    if not conv0:
        lj0 = getattr(segments[0], "lineage_json", None)
        if isinstance(lj0, dict) and lj0.get("conversation_id"):
            conv0 = str(lj0["conversation_id"])
    if not conv0:
        return None

    lineages: list[DialogueLineage | dict | None] = []
    seg_ids_order: list[str] = []
    for seg in segments:
        sid = str(getattr(seg, "id", "") or "")
        if sid:
            seg_ids_order.append(sid)
        lj = getattr(seg, "lineage_json", None)
        if lj:
            lineages.append(lj)
        else:
            um = getattr(seg, "user_message_id", None)
            if um:
                lineages.append(
                    DialogueLineage.for_single_turn(
                        conversation_id=str(
                            getattr(seg, "conversation_id", None) or conv0
                        ),
                        user_message_id=str(um),
                        assistant_message_id=None,
                        segment_ids=[sid] if sid else None,
                    )
                )

    merged = merge_dialogue_lineages(
        lineages, conversation_id=str(conv0), segment_ids_ordered=seg_ids_order
    )
    if merged is None:
        return None
    return merged.model_dump_json_safe()