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"])


@router.get("", response_model=PaginatedResponse)
async def list_techniques(
    category: Annotated[str | None, Query()] = None,
    creator_slug: Annotated[str | None, Query()] = None,
    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."""
    stmt = select(TechniquePage)

    if category:
        stmt = stmt.where(TechniquePage.topic_category == category)

    if creator_slug:
        # Join to Creator to filter by slug
        stmt = stmt.join(Creator, TechniquePage.creator_id == Creator.id).where(
            Creator.slug == creator_slug
        )

    # Count total before pagination
    from sqlalchemy import func

    count_stmt = select(func.count()).select_from(stmt.subquery())
    count_result = await db.execute(count_stmt)
    total = count_result.scalar() or 0

    stmt = stmt.order_by(TechniquePage.created_at.desc()).offset(offset).limit(limit)
    result = await db.execute(stmt)
    pages = result.scalars().all()

    return PaginatedResponse(
        items=[TechniquePageRead.model_validate(p) for p in pages],
        total=total,
        offset=offset,
        limit=limit,
    )


@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),
                )
            )

    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)