chrysopedia/backend/routers/techniques.py

"""Technique page endpoints — list and detail with eager-loaded relations."""

from __future__ import annotations

import logging
from typing import Annotated

from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from database import get_session
from models import Creator, KeyMoment, RelatedTechniqueLink, SourceVideo, TechniquePage, TechniquePageVersion
from schemas import (
    CreatorInfo,
    KeyMomentSummary,
    PaginatedResponse,
    RelatedLinkItem,
    TechniquePageDetail,
    TechniquePageRead,
    TechniquePageVersionDetail,
    TechniquePageVersionListResponse,
    TechniquePageVersionSummary,
)

logger = logging.getLogger("chrysopedia.techniques")

router = APIRouter(prefix="/techniques", tags=["techniques"])


async def _find_dynamic_related(
    db: AsyncSession,
    page: TechniquePage,
    exclude_slugs: set[str],
    limit: int,
) -> list[RelatedLinkItem]:
    """Score and return dynamically related technique pages.

    Scoring:
      - Same creator + same topic_category: +3
      - Same creator, different category: +2
      - Same topic_category, different creator: +2
      - Each overlapping topic_tag: +1
    """
    exclude_ids = {page.id}

    # Base: all other technique pages, eagerly load creator for name
    stmt = (
        select(TechniquePage)
        .options(selectinload(TechniquePage.creator))
        .where(TechniquePage.id != page.id)
    )
    if exclude_slugs:
        stmt = stmt.where(TechniquePage.slug.notin_(exclude_slugs))

    result = await db.execute(stmt)
    candidates = result.scalars().all()

    if not candidates:
        return []

    current_tags = set(page.topic_tags) if page.topic_tags else set()

    scored: list[tuple[int, str, TechniquePage]] = []
    for cand in candidates:
        score = 0
        reasons: list[str] = []

        same_creator = cand.creator_id == page.creator_id
        same_category = cand.topic_category == page.topic_category

        if same_creator and same_category:
            score += 3
            reasons.append("Same creator, same topic")
        elif same_creator:
            score += 2
            reasons.append("Same creator")
        elif same_category:
            score += 2
            reasons.append(f"Also about {page.topic_category}")

        # Tag overlap scoring
        if current_tags:
            cand_tags = set(cand.topic_tags) if cand.topic_tags else set()
            shared = current_tags & cand_tags
            if shared:
                score += len(shared)
                reasons.append(f"Shared tags: {', '.join(sorted(shared))}")

        if score > 0:
            scored.append((score, "; ".join(reasons), cand))

    # Sort descending by score, then by title for determinism
    scored.sort(key=lambda x: (-x[0], x[2].title))

    results: list[RelatedLinkItem] = []
    for score, reason, cand in scored[:limit]:
        creator_name = cand.creator.name if cand.creator else ""
        results.append(
            RelatedLinkItem(
                target_title=cand.title,
                target_slug=cand.slug,
                relationship="dynamic",
                creator_name=creator_name,
                topic_category=cand.topic_category,
                reason=reason,
            )
        )
    return results


@router.get("", response_model=PaginatedResponse)
async def list_techniques(
    category: Annotated[str | None, Query()] = None,
    creator_slug: Annotated[str | None, Query()] = None,
    sort: Annotated[str, Query()] = "recent",
    offset: Annotated[int, Query(ge=0)] = 0,
    limit: Annotated[int, Query(ge=1, le=100)] = 50,
    db: AsyncSession = Depends(get_session),
) -> PaginatedResponse:
    """List technique pages with optional category/creator filtering."""
    # Correlated subquery for key moment count (same pattern as creators.py)
    key_moment_count_sq = (
        select(func.count())
        .where(KeyMoment.technique_page_id == TechniquePage.id)
        .correlate(TechniquePage)
        .scalar_subquery()
    )

    # Build base query with filters
    base_stmt = select(TechniquePage.id)
    if category:
        base_stmt = base_stmt.where(TechniquePage.topic_category == category)
    if creator_slug:
        base_stmt = base_stmt.join(Creator, TechniquePage.creator_id == Creator.id).where(
            Creator.slug == creator_slug
        )

    # Count total before pagination
    count_stmt = select(func.count()).select_from(base_stmt.subquery())
    count_result = await db.execute(count_stmt)
    total = count_result.scalar() or 0

    # Main query with subquery column
    stmt = select(
        TechniquePage,
        key_moment_count_sq.label("key_moment_count"),
    )
    if category:
        stmt = stmt.where(TechniquePage.topic_category == category)
    if creator_slug:
        stmt = stmt.join(Creator, TechniquePage.creator_id == Creator.id).where(
            Creator.slug == creator_slug
        )

    stmt = stmt.options(selectinload(TechniquePage.creator))
    if sort == "random":
        stmt = stmt.order_by(func.random())
    else:
        stmt = stmt.order_by(TechniquePage.created_at.desc())
    stmt = stmt.offset(offset).limit(limit)
    result = await db.execute(stmt)
    rows = result.all()

    items = []
    for row in rows:
        p = row[0]
        km_count = row[1] or 0
        item = TechniquePageRead.model_validate(p)
        if p.creator:
            item.creator_name = p.creator.name
            item.creator_slug = p.creator.slug
        item.key_moment_count = km_count
        items.append(item)

    return PaginatedResponse(
        items=items,
        total=total,
        offset=offset,
        limit=limit,
    )


@router.get("/random")
async def random_technique(
    db: AsyncSession = Depends(get_session),
) -> dict:
    """Return the slug of a single random technique page."""
    stmt = select(TechniquePage.slug).order_by(func.random()).limit(1)
    result = await db.execute(stmt)
    slug = result.scalar_one_or_none()
    if slug is None:
        raise HTTPException(status_code=404, detail="No techniques available")
    return {"slug": slug}


@router.get("/{slug}", response_model=TechniquePageDetail)
async def get_technique(
    slug: str,
    db: AsyncSession = Depends(get_session),
) -> TechniquePageDetail:
    """Get full technique page detail with key moments, creator, and related links."""
    stmt = (
        select(TechniquePage)
        .where(TechniquePage.slug == slug)
        .options(
            selectinload(TechniquePage.key_moments).selectinload(KeyMoment.source_video),
            selectinload(TechniquePage.creator),
            selectinload(TechniquePage.outgoing_links).selectinload(
                RelatedTechniqueLink.target_page
            ),
            selectinload(TechniquePage.incoming_links).selectinload(
                RelatedTechniqueLink.source_page
            ),
        )
    )
    result = await db.execute(stmt)
    page = result.scalar_one_or_none()

    if page is None:
        raise HTTPException(status_code=404, detail=f"Technique '{slug}' not found")

    # Build key moments (ordered by start_time)
    key_moments = sorted(page.key_moments, key=lambda km: km.start_time)
    key_moment_items = []
    for km in key_moments:
        item = KeyMomentSummary.model_validate(km)
        item.video_filename = km.source_video.filename if km.source_video else ""
        key_moment_items.append(item)

    # Build creator info
    creator_info = None
    if page.creator:
        creator_info = CreatorInfo(
            name=page.creator.name,
            slug=page.creator.slug,
            genres=page.creator.genres,
        )

    # Build related links (outgoing + incoming)
    related_links: list[RelatedLinkItem] = []
    for link in page.outgoing_links:
        if link.target_page:
            related_links.append(
                RelatedLinkItem(
                    target_title=link.target_page.title,
                    target_slug=link.target_page.slug,
                    relationship=link.relationship.value if hasattr(link.relationship, 'value') else str(link.relationship),
                )
            )
    for link in page.incoming_links:
        if link.source_page:
            related_links.append(
                RelatedLinkItem(
                    target_title=link.source_page.title,
                    target_slug=link.source_page.slug,
                    relationship=link.relationship.value if hasattr(link.relationship, 'value') else str(link.relationship),
                )
            )

    # Supplement with dynamic related techniques (up to 4 total)
    curated_slugs = {link.target_slug for link in related_links}
    max_related = 4
    if len(related_links) < max_related:
        remaining = max_related - len(related_links)
        try:
            dynamic_links = await _find_dynamic_related(
                db, page, curated_slugs, remaining
            )
            related_links.extend(dynamic_links)
        except Exception:
            logger.warning(
                "Dynamic related query failed for %s, continuing with curated only",
                slug,
                exc_info=True,
            )

    base = TechniquePageRead.model_validate(page)

    # Count versions for this page
    version_count_stmt = select(func.count()).where(
        TechniquePageVersion.technique_page_id == page.id
    )
    version_count_result = await db.execute(version_count_stmt)
    version_count = version_count_result.scalar() or 0

    return TechniquePageDetail(
        **base.model_dump(),
        key_moments=key_moment_items,
        creator_info=creator_info,
        related_links=related_links,
        version_count=version_count,
    )


@router.get("/{slug}/versions", response_model=TechniquePageVersionListResponse)
async def list_technique_versions(
    slug: str,
    db: AsyncSession = Depends(get_session),
) -> TechniquePageVersionListResponse:
    """List all version snapshots for a technique page, newest first."""
    # Resolve the technique page
    page_stmt = select(TechniquePage).where(TechniquePage.slug == slug)
    page_result = await db.execute(page_stmt)
    page = page_result.scalar_one_or_none()
    if page is None:
        raise HTTPException(status_code=404, detail=f"Technique '{slug}' not found")

    # Fetch versions ordered by version_number DESC
    versions_stmt = (
        select(TechniquePageVersion)
        .where(TechniquePageVersion.technique_page_id == page.id)
        .order_by(TechniquePageVersion.version_number.desc())
    )
    versions_result = await db.execute(versions_stmt)
    versions = versions_result.scalars().all()

    items = [TechniquePageVersionSummary.model_validate(v) for v in versions]
    return TechniquePageVersionListResponse(items=items, total=len(items))


@router.get("/{slug}/versions/{version_number}", response_model=TechniquePageVersionDetail)
async def get_technique_version(
    slug: str,
    version_number: int,
    db: AsyncSession = Depends(get_session),
) -> TechniquePageVersionDetail:
    """Get a specific version snapshot by version number."""
    # Resolve the technique page
    page_stmt = select(TechniquePage).where(TechniquePage.slug == slug)
    page_result = await db.execute(page_stmt)
    page = page_result.scalar_one_or_none()
    if page is None:
        raise HTTPException(status_code=404, detail=f"Technique '{slug}' not found")

    # Fetch the specific version
    version_stmt = (
        select(TechniquePageVersion)
        .where(
            TechniquePageVersion.technique_page_id == page.id,
            TechniquePageVersion.version_number == version_number,
        )
    )
    version_result = await db.execute(version_stmt)
    version = version_result.scalar_one_or_none()
    if version is None:
        raise HTTPException(
            status_code=404,
            detail=f"Version {version_number} not found for technique '{slug}'",
        )

    return TechniquePageVersionDetail.model_validate(version)