mule-image/backend/app/routers/photos.py

"""
Photos API router
"""
from typing import List, Optional, Dict, Any
from datetime import datetime
from pathlib import Path
from fastapi import APIRouter, Depends, HTTPException, Query, Response
from fastapi.responses import FileResponse
from pydantic import BaseModel
from sqlalchemy import select, and_, or_, func
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload
import json
import os
import logging

logger = logging.getLogger(__name__)

from app.database import get_db
from app.models import Photo, Folder, Tag
from app.models.folders import SourceRoot
from app.models.heaps import heap_photos
from app.models.tags import photo_tags
from app.schemas.photos import PhotoResponse, PhotoUpdate, PhotoListResponse, BulkAction
from app.config import settings

router = APIRouter()

@router.get("")
async def list_photos(
    q: Optional[str] = None,
    date_from: Optional[datetime] = None,
    date_to: Optional[datetime] = None,
    folder_id: Optional[str] = None,
    tag_ids: Optional[str] = None,
    media_type: Optional[str] = None,
    rating_min: Optional[int] = Query(None, ge=0, le=5),
    rating_max: Optional[int] = Query(None, ge=0, le=5),
    color_label: Optional[str] = None,
    is_discarded: Optional[bool] = False,
    is_duplicate: Optional[bool] = None,
    heap_id: Optional[str] = None,
    sort: str = "taken_at",
    order: str = "desc",
    page: int = Query(1, ge=1),
    per_page: int = Query(100, ge=1, le=500),
    db: AsyncSession = Depends(get_db)
):
    """List photos with filters and pagination"""
    
    # Build query — eager-load tags so the response can include them
    # without an N+1 round-trip per photo.
    query = select(Photo).options(selectinload(Photo.tags))
    
    # Apply filters
    filters = []
    
    # Text search (would use FTS5 in production)
    if q:
        search_pattern = f"%{q}%"
        filters.append(
            or_(
                Photo.filename.ilike(search_pattern),
                Photo.user_title.ilike(search_pattern),
                Photo.user_notes.ilike(search_pattern),
                Photo.exif_json.ilike(search_pattern)
            )
        )
    
    # Date range
    if date_from:
        filters.append(Photo.taken_at >= date_from)
    if date_to:
        filters.append(Photo.taken_at <= date_to)
    
    # Folder filter. The sidebar can pass either a SourceRoot id or a
    # Folder id; both should include descendants so clicking a parent
    # folder shows everything under it (Lightroom semantics).
    if folder_id:
        sr_check = await db.execute(
            select(SourceRoot).where(SourceRoot.id == folder_id)
        )
        sr_row = sr_check.scalar_one_or_none()

        if sr_row is not None:
            # Source root → all folders under it (any depth).
            child_folders = await db.execute(
                select(Folder.id).where(Folder.source_root_id == folder_id)
            )
            child_ids = [row[0] for row in child_folders.all()]
            if child_ids:
                filters.append(Photo.folder_id.in_(child_ids))
            else:
                filters.append(Photo.id == '__no_match__')
        else:
            # Folder id → that folder + every descendant by path prefix.
            target_check = await db.execute(
                select(Folder).where(Folder.id == folder_id)
            )
            target = target_check.scalar_one_or_none()
            if target is None:
                filters.append(Photo.id == '__no_match__')
            else:
                target_path = os.path.normpath(target.path).rstrip(os.sep)
                desc_result = await db.execute(
                    select(Folder.id).where(
                        (Folder.path == target_path)
                        | (Folder.path.like(target_path + os.sep + '%'))
                    )
                )
                desc_ids = [row[0] for row in desc_result.all()]
                filters.append(Photo.folder_id.in_(desc_ids))
    
    # Media type filter
    if media_type:
        types = media_type.split(',')
        filters.append(Photo.media_type.in_(types))
    
    # Rating filter
    if rating_min is not None:
        filters.append(Photo.rating >= rating_min)
    if rating_max is not None:
        filters.append(Photo.rating <= rating_max)
    
    # Color label filter
    if color_label:
        if color_label == 'none':
            filters.append(Photo.color_label.is_(None))
        else:
            filters.append(Photo.color_label == color_label)
    
    # Discard filter — defaults to hiding discarded photos
    filters.append(Photo.is_discarded == is_discarded)

    # Duplicate filter — only applied when explicitly set, so the default
    # view shows everything regardless of duplicate status.
    if is_duplicate is not None:
        filters.append(Photo.is_duplicate == is_duplicate)

    # Heap membership filter — restrict to photos that belong to the heap.
    if heap_id:
        filters.append(
            Photo.id.in_(
                select(heap_photos.c.photo_id).where(heap_photos.c.heap_id == heap_id)
            )
        )

    # Tag filter — comma-separated tag ids, AND semantics. A photo must
    # have a row in photo_tags for EVERY listed tag. Implemented as a
    # single GROUP BY ... HAVING COUNT(DISTINCT) = N subquery so the cost
    # is independent of the number of tags being filtered.
    if tag_ids:
        tag_id_list = [t.strip() for t in tag_ids.split(',') if t.strip()]
        if tag_id_list:
            matching_photos = (
                select(photo_tags.c.photo_id)
                .where(photo_tags.c.tag_id.in_(tag_id_list))
                .group_by(photo_tags.c.photo_id)
                .having(
                    func.count(func.distinct(photo_tags.c.tag_id)) == len(tag_id_list)
                )
            )
            filters.append(Photo.id.in_(matching_photos))

    # Apply all filters
    if filters:
        query = query.where(and_(*filters))
    
    # Apply sorting. The sort field is whitelisted so a malicious client
    # can't pass an arbitrary column name (e.g. "filepath" leaks paths or
    # any other Photo attribute the model exposes).
    SORT_WHITELIST = {
        "taken_at": Photo.taken_at,
        "added_at": Photo.added_at,
        "filename": Photo.filename,
        "file_size": Photo.file_size,
        "rating": Photo.rating,
    }
    sort_column = SORT_WHITELIST.get(sort, Photo.taken_at)
    if order == "desc":
        query = query.order_by(sort_column.desc())
    else:
        query = query.order_by(sort_column.asc())
    
    # Count total results
    count_query = select(func.count()).select_from(query.subquery())
    total_result = await db.execute(count_query)
    total = total_result.scalar()
    
    # Apply pagination
    offset = (page - 1) * per_page
    query = query.offset(offset).limit(per_page)
    
    # Execute query
    result = await db.execute(query)
    photos = result.scalars().all()
    
    # Convert to response, attaching tags inline so the frontend can group
    # client-side without a second round-trip.
    photo_dicts = []
    for photo in photos:
        d = PhotoResponse.from_orm(photo).dict()
        d["tags"] = [
            {"id": t.id, "name": t.name, "color": t.color}
            for t in (photo.tags or [])
        ]
        photo_dicts.append(d)

    return {
        "photos": photo_dicts,
        "total": total,
        "page": page,
        "per_page": per_page,
        "pages": (total + per_page - 1) // per_page if total else 0,
    }

@router.get("/{photo_id}")
async def get_photo(
    photo_id: str,
    db: AsyncSession = Depends(get_db)
):
    """Get single photo with full EXIF and its tags."""
    result = await db.execute(
        select(Photo).where(Photo.id == photo_id)
    )
    photo = result.scalar_one_or_none()

    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")

    # Fetch tags via the join table so we don't need to declare a
    # relationship on the Photo model side.
    tag_result = await db.execute(
        select(Tag)
        .join(photo_tags, Tag.id == photo_tags.c.tag_id)
        .where(photo_tags.c.photo_id == photo_id)
        .order_by(Tag.name.asc())
    )
    tags = tag_result.scalars().all()

    base = PhotoResponse.from_orm(photo).dict()
    base["tags"] = [
        {"id": t.id, "name": t.name, "color": t.color} for t in tags
    ]
    return base


@router.post("/{photo_id}/tags", status_code=201)
async def add_photo_tags(
    photo_id: str,
    body: dict,
    db: AsyncSession = Depends(get_db),
):
    """Add one or more tags to a photo. Body: { tag_ids: [str, ...] }.
    Idempotent: re-adding existing members is a no-op."""
    photo_result = await db.execute(select(Photo).where(Photo.id == photo_id))
    if photo_result.scalar_one_or_none() is None:
        raise HTTPException(status_code=404, detail="Photo not found")

    tag_ids = body.get("tag_ids") or []
    if not isinstance(tag_ids, list) or not tag_ids:
        return {"status": "success", "added": 0}

    existing = await db.execute(
        select(photo_tags.c.tag_id).where(
            photo_tags.c.photo_id == photo_id,
            photo_tags.c.tag_id.in_(tag_ids),
        )
    )
    existing_ids = {row[0] for row in existing.all()}
    new_ids = [tid for tid in tag_ids if tid not in existing_ids]

    if new_ids:
        from sqlalchemy import insert
        await db.execute(
            insert(photo_tags),
            [{"photo_id": photo_id, "tag_id": tid} for tid in new_ids],
        )
        await db.commit()

    return {"status": "success", "added": len(new_ids)}


@router.delete("/{photo_id}/tags/{tag_id}", status_code=204)
async def remove_photo_tag(
    photo_id: str,
    tag_id: str,
    db: AsyncSession = Depends(get_db),
):
    """Remove a tag from a photo. Removing a non-member is a no-op."""
    from sqlalchemy import delete as sql_delete
    await db.execute(
        sql_delete(photo_tags).where(
            photo_tags.c.photo_id == photo_id,
            photo_tags.c.tag_id == tag_id,
        )
    )
    await db.commit()
    return None

@router.get("/{photo_id}/thumb/{size}")
async def get_thumbnail(
    photo_id: str,
    size: str,
    response: Response,
    db: AsyncSession = Depends(get_db)
):
    """Serve thumbnail (with Nginx X-Accel-Redirect support)"""
    if size not in ['small', 'medium', 'large']:
        raise HTTPException(status_code=400, detail="Invalid thumbnail size")
    
    result = await db.execute(
        select(Photo).where(Photo.id == photo_id)
    )
    photo = result.scalar_one_or_none()
    
    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")
    
    # Check if thumbnail exists, generate if not
    thumb_dir = f"/data/thumbs/{photo_id}"
    thumb_path = f"{thumb_dir}/{size}.webp"
    
    if not os.path.exists(thumb_path):
        # Generate thumbnail on demand
        from app.tasks.thumbs import generate_thumbnails
        generate_thumbnails.delay(photo_id)
        
        # For now, return a placeholder or the original with reduced quality
        if os.path.exists(photo.filepath):
            from PIL import Image
            try:
                os.makedirs(thumb_dir, exist_ok=True)
                img = Image.open(photo.filepath)
                
                # Auto-rotate based on EXIF
                from PIL import ExifTags
                try:
                    for orientation in ExifTags.TAGS.keys():
                        if ExifTags.TAGS[orientation] == 'Orientation':
                            break
                    exif = img._getexif()
                    if exif is not None:
                        orient = exif.get(orientation)
                        if orient == 3:
                            img = img.rotate(180, expand=True)
                        elif orient == 6:
                            img = img.rotate(270, expand=True)
                        elif orient == 8:
                            img = img.rotate(90, expand=True)
                except:
                    pass
                
                # Generate thumbnail size
                sizes = {'small': 150, 'medium': 400, 'large': 800}
                target_size = sizes.get(size, 400)
                img.thumbnail((target_size, target_size), Image.Resampling.LANCZOS)
                
                # Save as WebP
                img.save(thumb_path, 'WEBP', quality=85, optimize=True)
                
            except Exception as e:
                logger.error(f"Error generating thumbnail: {e}")
                raise HTTPException(status_code=404, detail="Could not generate thumbnail")
    
    # Check if we're behind Nginx
    if os.environ.get('USE_X_ACCEL_REDIRECT'):
        # Use Nginx X-Accel-Redirect for better performance
        response.headers['X-Accel-Redirect'] = f'/internal_thumbs/{photo_id}/{size}.webp'
        response.headers['Content-Type'] = 'image/webp'
        return Response()
    else:
        # Direct file serving for development
        return FileResponse(thumb_path, media_type='image/webp')

@router.get("/{photo_id}/original")
async def get_original(
    photo_id: str,
    db: AsyncSession = Depends(get_db)
):
    """Serve original file (download for RAW, inline for web-safe formats)"""
    result = await db.execute(
        select(Photo).where(Photo.id == photo_id)
    )
    photo = result.scalar_one_or_none()

    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")

    if not os.path.exists(photo.filepath):
        raise HTTPException(status_code=404, detail="File not found")

    # Pick a media type the browser can render inline for web-safe formats
    # so the loupe view and <video> tags work without forcing a download.
    ext = Path(photo.filepath).suffix.lower()
    inline_types = {
        '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg',
        '.png': 'image/png', '.webp': 'image/webp', '.gif': 'image/gif',
        '.mp4': 'video/mp4', '.mov': 'video/quicktime',
        '.webm': 'video/webm', '.mkv': 'video/x-matroska',
    }
    media_type = inline_types.get(ext, 'application/octet-stream')

    return FileResponse(
        photo.filepath,
        filename=photo.filename if media_type == 'application/octet-stream' else None,
        media_type=media_type,
    )


# Extensions that the browser can decode natively. Anything else (RAW, HEIC,
# TIFF) needs the /proxy endpoint to convert to WebP for display.
_WEB_SAFE_DISPLAY_EXTS = {'.jpg', '.jpeg', '.png', '.webp', '.gif'}


def _generate_proxy_webp(src_path: str, dst_path: str) -> None:
    """Decode src_path with the appropriate backend and write a full-res WebP
    to dst_path. Used by GET /photos/{id}/proxy for RAW/HEIC/TIFF display.

    Conservative: catches per-format failures and falls back to extracting an
    embedded preview where possible (RAW), so a single broken file never
    crashes the request.
    """
    from PIL import Image
    ext = Path(src_path).suffix.lower()

    img = None

    # RAW formats — decode via rawpy at full size
    raw_exts = {'.cr2', '.cr3', '.nef', '.nrw', '.arw', '.srf',
                '.raf', '.rw2', '.orf', '.srw', '.pef', '.rwl', '.dng'}
    if ext in raw_exts:
        try:
            import rawpy
            with rawpy.imread(src_path) as raw:
                rgb = raw.postprocess(use_camera_wb=True, no_auto_bright=False)
            img = Image.fromarray(rgb, 'RGB')
        except Exception as e:
            logger.warning(f"rawpy decode failed for {src_path}: {e}; trying embedded preview")
            try:
                import rawpy
                with rawpy.imread(src_path) as raw:
                    thumb = raw.extract_thumb()
                    if thumb.format == rawpy.ThumbFormat.JPEG:
                        from io import BytesIO
                        img = Image.open(BytesIO(thumb.data))
            except Exception as e2:
                logger.error(f"RAW preview extraction also failed for {src_path}: {e2}")
                raise HTTPException(status_code=415, detail="Unable to decode RAW file")

    # HEIC/HEIF — pillow-heif registers a PIL plugin
    elif ext in {'.heic', '.heif'}:
        try:
            from pillow_heif import register_heif_opener
            register_heif_opener()
            img = Image.open(src_path)
        except Exception as e:
            logger.error(f"HEIC decode failed for {src_path}: {e}")
            raise HTTPException(status_code=415, detail="Unable to decode HEIC file")

    # TIFF and any other PIL-supported format
    else:
        try:
            img = Image.open(src_path)
        except Exception as e:
            logger.error(f"PIL open failed for {src_path}: {e}")
            raise HTTPException(status_code=415, detail="Unable to decode image")

    # Auto-rotate via EXIF
    try:
        from PIL import ImageOps
        img = ImageOps.exif_transpose(img)
    except Exception:
        pass

    if img.mode not in ('RGB', 'RGBA'):
        img = img.convert('RGB')

    os.makedirs(os.path.dirname(dst_path), exist_ok=True)
    img.save(dst_path, 'WEBP', quality=90, method=4)


@router.get("/{photo_id}/proxy")
async def get_proxy(
    photo_id: str,
    response: Response,
    db: AsyncSession = Depends(get_db),
):
    """Serve a full-resolution WebP proxy for non-web-safe formats (RAW, HEIC,
    TIFF) so the loupe view can display them inline. Web-safe formats are
    redirected to /original to avoid pointless transcoding.

    Cached at /data/proxies/{photo_id}.webp; subsequent requests serve the
    cached file (with optional X-Accel-Redirect for production).
    """
    result = await db.execute(select(Photo).where(Photo.id == photo_id))
    photo = result.scalar_one_or_none()

    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")

    if not os.path.exists(photo.filepath):
        raise HTTPException(status_code=404, detail="File not found")

    ext = Path(photo.filepath).suffix.lower()

    # Web-safe formats don't need a proxy — serve the original directly so the
    # browser uses its native decoder. Saves disk and CPU.
    if ext in _WEB_SAFE_DISPLAY_EXTS:
        return FileResponse(
            photo.filepath,
            media_type={
                '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg',
                '.png': 'image/png', '.webp': 'image/webp', '.gif': 'image/gif',
            }[ext],
        )

    proxy_dir = "/data/proxies"
    proxy_path = f"{proxy_dir}/{photo_id}.webp"

    if not os.path.exists(proxy_path):
        try:
            _generate_proxy_webp(photo.filepath, proxy_path)
        except HTTPException:
            raise
        except Exception as e:
            logger.error(f"Proxy generation failed for {photo_id}: {e}")
            raise HTTPException(status_code=500, detail="Proxy generation failed")

    if os.environ.get('USE_X_ACCEL_REDIRECT'):
        response.headers['X-Accel-Redirect'] = f'/internal_proxies/{photo_id}.webp'
        response.headers['Content-Type'] = 'image/webp'
        return Response()

    return FileResponse(proxy_path, media_type='image/webp')

@router.patch("/{photo_id}", response_model=PhotoResponse)
async def update_photo(
    photo_id: str,
    update: PhotoUpdate,
    db: AsyncSession = Depends(get_db)
):
    """Update photo metadata. If `filename` is included, also rename the
    file on disk in its current directory (no cross-folder moves through
    this endpoint).
    """
    result = await db.execute(
        select(Photo).where(Photo.id == photo_id)
    )
    photo = result.scalar_one_or_none()

    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")

    update_data = update.dict(exclude_unset=True)

    # Filename rename: validate, rename on disk, then update both filename
    # and filepath atomically. Done before any other field changes so a
    # filesystem failure leaves the rest of the row untouched.
    if 'filename' in update_data:
        new_name = (update_data.pop('filename') or '').strip()
        if not new_name:
            raise HTTPException(status_code=400, detail="Filename cannot be empty")
        # Reject path separators and parent traversal — same-directory only.
        if '/' in new_name or '\\' in new_name or new_name in ('.', '..'):
            raise HTTPException(status_code=400, detail="Invalid filename")

        if new_name != photo.filename:
            current_dir = os.path.dirname(photo.filepath)
            new_path = os.path.join(current_dir, new_name)

            if not os.path.exists(photo.filepath):
                raise HTTPException(status_code=404, detail="Source file missing on disk")
            if os.path.exists(new_path):
                raise HTTPException(status_code=409, detail="A file with that name already exists")

            try:
                os.rename(photo.filepath, new_path)
            except OSError as e:
                logger.error(f"Failed to rename {photo.filepath} -> {new_path}: {e}")
                raise HTTPException(status_code=500, detail=f"Rename failed: {e}")

            photo.filename = new_name
            photo.filepath = new_path

    # Apply remaining updates
    for field, value in update_data.items():
        setattr(photo, field, value)

    await db.commit()
    await db.refresh(photo)
    
    return PhotoResponse.from_orm(photo)

@router.delete("/{photo_id}")
async def discard_photo(
    photo_id: str,
    db: AsyncSession = Depends(get_db)
):
    """Soft-discard a photo: sets is_discarded=true. The file stays on disk so
    restore is just a flag flip. Permanent deletion happens via DELETE
    /discard/{id} or DELETE /discard/empty.
    """
    result = await db.execute(
        select(Photo).where(Photo.id == photo_id)
    )
    photo = result.scalar_one_or_none()

    if not photo:
        raise HTTPException(status_code=404, detail="Photo not found")

    photo.is_discarded = True
    photo.discarded_at = datetime.utcnow()
    await db.commit()

    return {"status": "success", "message": "Photo discarded"}

class MoveRequest(BaseModel):
    photo_ids: list[str]
    target_id: str  # folder id OR source root id


class CopyRequest(BaseModel):
    photo_ids: list[str]
    target_id: str  # folder id OR source root id


@router.post("/copy")
async def copy_photos(
    body: CopyRequest,
    db: AsyncSession = Depends(get_db),
):
    """Copy photos into a target folder. Same target resolution as /move
    (folder id or source root id), but uses shutil.copy2 and creates new
    Photo rows for each copied file. Original photos are unaffected.

    Each new row gets is_duplicate=true so the user can spot the
    duplicates later. The new file's name is suffixed with " (copy)" if
    a name collision would otherwise happen, and " (copy 2)", etc., for
    further conflicts.
    """
    import shutil

    # Resolve target_id → (target_dir, target_folder)
    sr_check = await db.execute(
        select(SourceRoot).where(SourceRoot.id == body.target_id)
    )
    source_root = sr_check.scalar_one_or_none()

    if source_root is not None:
        target_dir = source_root.path
        from app.tasks.scan import get_or_create_folder
        target_folder = await get_or_create_folder(db, target_dir, source_root.id)
    else:
        folder_check = await db.execute(
            select(Folder).where(Folder.id == body.target_id)
        )
        target_folder = folder_check.scalar_one_or_none()
        if target_folder is None:
            raise HTTPException(status_code=404, detail="Target folder not found")
        target_dir = target_folder.path

    if not os.path.isdir(target_dir):
        raise HTTPException(
            status_code=400,
            detail=f"Target directory does not exist: {target_dir}",
        )

    if not body.photo_ids:
        return {"status": "success", "copied": 0, "errors": []}

    photos_result = await db.execute(
        select(Photo).where(Photo.id.in_(body.photo_ids))
    )
    photos_to_copy = photos_result.scalars().all()

    copied = 0
    errors: list[dict] = []

    def _unique_target_name(directory: str, filename: str) -> Optional[str]:
        """Find a non-colliding filename in `directory` based on `filename`,
        suffixing " (copy)", " (copy 2)", ... if needed. Gives up after 100
        attempts."""
        if not os.path.exists(os.path.join(directory, filename)):
            return filename
        stem, ext = os.path.splitext(filename)
        for i in range(1, 100):
            candidate = f"{stem} (copy{'' if i == 1 else f' {i}'}){ext}"
            if not os.path.exists(os.path.join(directory, candidate)):
                return candidate
        return None

    for photo in photos_to_copy:
        if not os.path.exists(photo.filepath):
            errors.append({"id": photo.id, "error": "source file missing"})
            continue

        new_name = _unique_target_name(target_dir, photo.filename)
        if new_name is None:
            errors.append({"id": photo.id, "error": "too many name collisions"})
            continue

        new_path = os.path.join(target_dir, new_name)

        try:
            shutil.copy2(photo.filepath, new_path)
        except OSError as e:
            errors.append({"id": photo.id, "error": str(e)})
            continue

        # Create a new Photo row pointing at the copy. Most metadata is
        # copied verbatim; the file_hash stays so the duplicate flag does
        # the right thing across the library.
        new_photo = Photo(
            filepath=new_path,
            filename=new_name,
            folder_id=target_folder.id,
            file_hash=photo.file_hash,
            media_type=photo.media_type,
            original_format=photo.original_format,
            width=photo.width,
            height=photo.height,
            file_size=photo.file_size,
            taken_at=photo.taken_at,
            taken_at_source=photo.taken_at_source,
            user_title=photo.user_title,
            user_notes=photo.user_notes,
            rating=photo.rating,
            color_label=photo.color_label,
            exif_json=photo.exif_json,
            is_duplicate=True,
            processing_status='pending',
        )
        db.add(new_photo)
        copied += 1

    await db.commit()

    return {
        "status": "success",
        "copied": copied,
        "errors": errors,
    }


@router.post("/move")
async def move_photos(
    body: MoveRequest,
    db: AsyncSession = Depends(get_db),
):
    """Move photos into a target folder. The target can be either a Folder
    id or a SourceRoot id (since the LeftSidebar only exposes source roots
    today). The handler resolves the target to an on-disk directory, calls
    shutil.move for each photo, and updates photo.filepath + folder_id.

    Per-file failures (target name collision, missing source) are collected
    and returned in the response so a single bad photo doesn't abort the
    batch.
    """
    import shutil

    # Resolve target_id → (target_dir, target_folder)
    sr_check = await db.execute(
        select(SourceRoot).where(SourceRoot.id == body.target_id)
    )
    source_root = sr_check.scalar_one_or_none()

    if source_root is not None:
        target_dir = source_root.path
        # We need a Folder row to point photo.folder_id at. Reuse the
        # scanner's get_or_create helper so we don't duplicate the dedupe
        # / normalization logic.
        from app.tasks.scan import get_or_create_folder
        target_folder = await get_or_create_folder(db, target_dir, source_root.id)
    else:
        folder_check = await db.execute(
            select(Folder).where(Folder.id == body.target_id)
        )
        target_folder = folder_check.scalar_one_or_none()
        if target_folder is None:
            raise HTTPException(status_code=404, detail="Target folder not found")
        target_dir = target_folder.path

    if not os.path.isdir(target_dir):
        raise HTTPException(
            status_code=400,
            detail=f"Target directory does not exist: {target_dir}",
        )

    if not body.photo_ids:
        return {"status": "success", "moved": 0, "errors": []}

    # Fetch the photo rows
    photos_result = await db.execute(
        select(Photo).where(Photo.id.in_(body.photo_ids))
    )
    photos_to_move = photos_result.scalars().all()

    moved = 0
    errors: list[dict] = []

    for photo in photos_to_move:
        # Skip if already in the target folder.
        if photo.folder_id == target_folder.id:
            continue

        new_path = os.path.join(target_dir, photo.filename)

        if not os.path.exists(photo.filepath):
            errors.append({"id": photo.id, "error": "source file missing"})
            continue
        if os.path.exists(new_path):
            errors.append({"id": photo.id, "error": f"name already exists in target: {photo.filename}"})
            continue

        try:
            shutil.move(photo.filepath, new_path)
        except OSError as e:
            errors.append({"id": photo.id, "error": str(e)})
            continue

        photo.filepath = new_path
        photo.folder_id = target_folder.id
        moved += 1

    await db.commit()

    return {
        "status": "success",
        "moved": moved,
        "errors": errors,
    }


@router.post("/bulk")
async def bulk_action(
    action: BulkAction,
    db: AsyncSession = Depends(get_db)
):
    """Perform bulk actions on multiple photos"""
    # Get photos
    result = await db.execute(
        select(Photo).where(Photo.id.in_(action.ids))
    )
    photos = result.scalars().all()
    
    if not photos:
        raise HTTPException(status_code=404, detail="No photos found")
    
    # Perform action based on type
    if action.action == 'discard':
        for photo in photos:
            photo.is_discarded = True
            photo.discarded_at = datetime.utcnow()
    elif action.action == 'restore':
        for photo in photos:
            photo.is_discarded = False
            photo.discarded_at = None
    elif action.action == 'set_rating':
        for photo in photos:
            photo.rating = action.value
    elif action.action == 'set_color':
        for photo in photos:
            photo.color_label = action.value
    elif action.action == 'add_tags':
        # value is a list of tag ids. We bulk-insert (photo_id, tag_id)
        # rows for every (photo, tag) combination that doesn't already
        # exist, so the operation is idempotent.
        tag_ids = action.value or []
        if not isinstance(tag_ids, list) or not tag_ids:
            return {"status": "success", "added": 0, "message": "No tags supplied"}
        photo_ids = [p.id for p in photos]
        existing = await db.execute(
            select(photo_tags.c.photo_id, photo_tags.c.tag_id).where(
                photo_tags.c.photo_id.in_(photo_ids),
                photo_tags.c.tag_id.in_(tag_ids),
            )
        )
        existing_pairs = {(row[0], row[1]) for row in existing.all()}
        new_rows = [
            {"photo_id": pid, "tag_id": tid}
            for pid in photo_ids
            for tid in tag_ids
            if (pid, tid) not in existing_pairs
        ]
        if new_rows:
            from sqlalchemy import insert
            await db.execute(insert(photo_tags), new_rows)
        await db.commit()
        return {
            "status": "success",
            "added": len(new_rows),
            "message": f"Added {len(new_rows)} tag link{'s' if len(new_rows) != 1 else ''}",
        }
    elif action.action == 'remove_tags':
        tag_ids = action.value or []
        if not isinstance(tag_ids, list) or not tag_ids:
            return {"status": "success", "removed": 0, "message": "No tags supplied"}
        photo_ids = [p.id for p in photos]
        from sqlalchemy import delete as sql_delete
        result = await db.execute(
            sql_delete(photo_tags).where(
                photo_tags.c.photo_id.in_(photo_ids),
                photo_tags.c.tag_id.in_(tag_ids),
            )
        )
        await db.commit()
        return {
            "status": "success",
            "removed": result.rowcount or 0,
            "message": f"Removed tag link{'s' if (result.rowcount or 0) != 1 else ''}",
        }
    else:
        raise HTTPException(status_code=400, detail="Invalid action")
    
    await db.commit()
    
    return {
        "status": "success",
        "message": f"{action.action} applied to {len(photos)} photos"
    }