import re
import html as html_mod
import logging
import mimetypes
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Optional, List, Dict, Any

import frontmatter
import mistune
from fastapi import FastAPI, HTTPException, Query, Body
from fastapi.staticfiles import StaticFiles
from fastapi.responses import HTMLResponse, FileResponse, Response
from pydantic import BaseModel, Field

from backend.indexer import (
    build_index,
    reload_index,
    index,
    path_index,
    get_vault_data,
    get_vault_names,
    find_file_in_index,
    parse_markdown_file,
    _extract_tags,
    SUPPORTED_EXTENSIONS,
)
from backend.search import search, get_all_tags
from backend.image_processor import preprocess_images
from backend.attachment_indexer import rescan_vault_attachments, get_attachment_stats

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(name)s] %(levelname)s: %(message)s",
)
logger = logging.getLogger("obsigate")


# ---------------------------------------------------------------------------
# Pydantic response models
# ---------------------------------------------------------------------------

class VaultInfo(BaseModel):
    """Summary information about a configured vault."""
    name: str = Field(description="Display name of the vault")
    file_count: int = Field(description="Number of indexed files")
    tag_count: int = Field(description="Number of unique tags")


class BrowseItem(BaseModel):
    """A single entry (file or directory) returned by the browse endpoint."""
    name: str
    path: str
    type: str = Field(description="'file' or 'directory'")
    children_count: Optional[int] = None
    size: Optional[int] = None
    extension: Optional[str] = None


class BrowseResponse(BaseModel):
    """Paginated directory listing for a vault."""
    vault: str
    path: str
    items: List[BrowseItem]


class FileContentResponse(BaseModel):
    """Rendered file content with metadata."""
    vault: str
    path: str
    title: str
    tags: List[str]
    frontmatter: Dict[str, Any]
    html: str
    raw_length: int
    extension: str
    is_markdown: bool


class FileRawResponse(BaseModel):
    """Raw text content of a file."""
    vault: str
    path: str
    raw: str


class FileSaveResponse(BaseModel):
    """Confirmation after saving a file."""
    status: str
    vault: str
    path: str
    size: int


class FileDeleteResponse(BaseModel):
    """Confirmation after deleting a file."""
    status: str
    vault: str
    path: str


class SearchResultItem(BaseModel):
    """A single search result."""
    vault: str
    path: str
    title: str
    tags: List[str]
    score: int
    snippet: str
    modified: str


class SearchResponse(BaseModel):
    """Full-text search response."""
    query: str
    vault_filter: str
    tag_filter: Optional[str]
    count: int
    results: List[SearchResultItem]


class TagsResponse(BaseModel):
    """Tag aggregation response."""
    vault_filter: Optional[str]
    tags: Dict[str, int]


class TreeSearchResult(BaseModel):
    """A single tree search result item."""
    vault: str
    path: str
    name: str
    type: str = Field(description="'file' or 'directory'")
    matched_path: str


class TreeSearchResponse(BaseModel):
    """Tree search response with matching paths."""
    query: str
    vault_filter: str
    results: List[TreeSearchResult]


class ReloadResponse(BaseModel):
    """Index reload confirmation with per-vault stats."""
    status: str
    vaults: Dict[str, Any]


class HealthResponse(BaseModel):
    """Application health status."""
    status: str
    version: str
    vaults: int
    total_files: int


# ---------------------------------------------------------------------------
# Application lifespan (replaces deprecated on_event)
# ---------------------------------------------------------------------------

@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan: build index on startup, cleanup on shutdown."""
    logger.info("ObsiGate starting \u2014 building index...")
    await build_index()
    logger.info("ObsiGate ready.")
    yield


app = FastAPI(title="ObsiGate", version="1.1.0", lifespan=lifespan)

# Resolve frontend path relative to this file
FRONTEND_DIR = Path(__file__).resolve().parent.parent / "frontend"


# ---------------------------------------------------------------------------
# Path safety helper
# ---------------------------------------------------------------------------

def _resolve_safe_path(vault_root: Path, relative_path: str) -> Path:
    """Resolve a relative path safely within the vault root.

    Prevents directory traversal attacks by ensuring the resolved
    absolute path is a descendant of *vault_root*.

    Args:
        vault_root: The vault's root directory (absolute).
        relative_path: The user-supplied relative path.

    Returns:
        Resolved absolute ``Path``.

    Raises:
        HTTPException(403): When the resolved path escapes the vault root.
    """
    # Construct the full path without resolving symlinks first
    full_path = vault_root / relative_path
    
    # Resolve both paths to handle symlinks
    try:
        resolved = full_path.resolve(strict=False)
        vault_resolved = vault_root.resolve(strict=False)
    except Exception as e:
        logger.error(f"Path resolution error - vault_root: {vault_root}, relative_path: {relative_path}, error: {e}")
        raise HTTPException(status_code=500, detail=f"Path resolution error: {str(e)}")
    
    # Check if resolved path is within vault using string comparison (case-insensitive on Windows)
    try:
        # This will raise ValueError if resolved is not relative to vault_resolved
        resolved.relative_to(vault_resolved)
    except ValueError:
        # Try case-insensitive comparison for Windows/Docker compatibility
        resolved_str = str(resolved).lower()
        vault_str = str(vault_resolved).lower()
        if not resolved_str.startswith(vault_str):
            logger.warning(f"Path outside vault - vault: {vault_resolved}, requested: {relative_path}, resolved: {resolved}")
            raise HTTPException(status_code=403, detail="Access denied: path outside vault")
    
    return resolved


# ---------------------------------------------------------------------------
# Markdown rendering helpers (singleton renderer)
# ---------------------------------------------------------------------------

# Cached mistune renderer — avoids re-creating on every request
_markdown_renderer = mistune.create_markdown(
    escape=False,
    plugins=["table", "strikethrough", "footnotes", "task_lists"],
)


def _convert_wikilinks(content: str, current_vault: str) -> str:
    """Convert ``[[wikilinks]]`` and ``[[target|display]]`` to clickable HTML.

    Resolved links get a ``data-vault`` / ``data-path`` attribute pair.
    Unresolved links are rendered as ``<span class="wikilink-missing">``.

    Args:
        content: Markdown string potentially containing wikilinks.
        current_vault: Active vault name for resolution priority.

    Returns:
        Markdown string with wikilinks replaced by HTML anchors.
    """
    def _replace(match):
        target = match.group(1).strip()
        display = match.group(2).strip() if match.group(2) else target
        found = find_file_in_index(target, current_vault)
        if found:
            return (
                f'<a class="wikilink" href="#" '
                f'data-vault="{found["vault"]}" '
                f'data-path="{found["path"]}">{display}</a>'
            )
        return f'<span class="wikilink-missing">{display}</span>'

    pattern = r'\[\[([^\]|]+)(?:\|([^\]]+))?\]\]'
    return re.sub(pattern, _replace, content)


def _render_markdown(raw_md: str, vault_name: str, current_file_path: Optional[Path] = None) -> str:
    """Render a markdown string to HTML with wikilink and image support.

    Uses the cached singleton mistune renderer for performance.

    Args:
        raw_md: Raw markdown text (frontmatter already stripped).
        vault_name: Current vault for wikilink resolution context.
        current_file_path: Absolute path to the current markdown file.

    Returns:
        HTML string.
    """
    # Get vault data for image resolution
    vault_data = get_vault_data(vault_name)
    vault_root = Path(vault_data["path"]) if vault_data else None
    attachments_path = vault_data.get("config", {}).get("attachmentsPath") if vault_data else None
    
    # Preprocess images first
    if vault_root:
        raw_md = preprocess_images(raw_md, vault_name, vault_root, current_file_path, attachments_path)
    
    # Convert wikilinks
    converted = _convert_wikilinks(raw_md, vault_name)
    
    return _markdown_renderer(converted)


# ---------------------------------------------------------------------------
# API Endpoints
# ---------------------------------------------------------------------------

@app.get("/api/health", response_model=HealthResponse)
async def api_health():
    """Health check endpoint for Docker and monitoring.

    Returns:
        Application status, version, vault count and total file count.
    """
    total_files = sum(len(v["files"]) for v in index.values())
    return {
        "status": "ok",
        "version": app.version,
        "vaults": len(index),
        "total_files": total_files,
    }


@app.get("/api/vaults", response_model=List[VaultInfo])
async def api_vaults():
    """List all configured vaults with file and tag counts.

    Returns:
        List of vault summary objects.
    """
    result = []
    for name, data in index.items():
        result.append({
            "name": name,
            "file_count": len(data["files"]),
            "tag_count": len(data["tags"]),
        })
    return result


@app.get("/api/browse/{vault_name}", response_model=BrowseResponse)
async def api_browse(vault_name: str, path: str = ""):
    """Browse directories and files in a vault at a given path level.

    Returns sorted entries (directories first, then files) with metadata.
    Hidden files/directories (starting with ``"."`` ) are excluded.

    Args:
        vault_name: Name of the vault to browse.
        path: Relative directory path within the vault (empty = root).

    Returns:
        ``BrowseResponse`` with vault name, path, and item list.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    # Path traversal protection
    target = _resolve_safe_path(vault_root, path) if path else vault_root.resolve()

    if not target.exists():
        raise HTTPException(status_code=404, detail=f"Path not found: {path}")

    items = []
    try:
        for entry in sorted(target.iterdir(), key=lambda e: (not e.is_dir(), e.name.lower())):
            # Skip hidden files/dirs
            if entry.name.startswith("."):
                continue
            rel = str(entry.relative_to(vault_root)).replace("\\", "/")
            if entry.is_dir():
                # Count only direct children (files and subdirs) for performance
                try:
                    file_count = sum(
                        1 for child in entry.iterdir()
                        if not child.name.startswith(".")
                        and (child.is_file() and (child.suffix.lower() in SUPPORTED_EXTENSIONS or child.name.lower() in ("dockerfile", "makefile"))
                             or child.is_dir())
                    )
                except PermissionError:
                    file_count = 0
                items.append({
                    "name": entry.name,
                    "path": rel,
                    "type": "directory",
                    "children_count": file_count,
                })
            elif entry.suffix.lower() in SUPPORTED_EXTENSIONS or entry.name.lower() in ("dockerfile", "makefile"):
                items.append({
                    "name": entry.name,
                    "path": rel,
                    "type": "file",
                    "size": entry.stat().st_size,
                    "extension": entry.suffix.lower(),
                })
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied")

    return {"vault": vault_name, "path": path, "items": items}


# Map file extensions to highlight.js language hints
EXT_TO_LANG = {
    ".py": "python", ".js": "javascript", ".ts": "typescript",
    ".jsx": "jsx", ".tsx": "tsx", ".sh": "bash", ".bash": "bash",
    ".zsh": "bash", ".fish": "fish", ".bat": "batch", ".cmd": "batch",
    ".ps1": "powershell", ".json": "json", ".yaml": "yaml", ".yml": "yaml",
    ".toml": "toml", ".xml": "xml", ".csv": "plaintext",
    ".cfg": "ini", ".ini": "ini", ".conf": "ini", ".env": "bash",
    ".html": "html", ".css": "css", ".scss": "scss", ".less": "less",
    ".java": "java", ".c": "c", ".cpp": "cpp", ".h": "c", ".hpp": "cpp",
    ".cs": "csharp", ".go": "go", ".rs": "rust", ".rb": "ruby",
    ".php": "php", ".sql": "sql", ".r": "r", ".swift": "swift",
    ".kt": "kotlin", ".txt": "plaintext", ".log": "plaintext",
    ".dockerfile": "dockerfile", ".makefile": "makefile", ".cmake": "cmake",
}


@app.get("/api/file/{vault_name}/raw", response_model=FileRawResponse)
async def api_file_raw(vault_name: str, path: str = Query(..., description="Relative path to file")):
    """Return raw file content as plain text.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.

    Returns:
        ``FileRawResponse`` with vault, path, and raw text content.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    try:
        raw = file_path.read_text(encoding="utf-8", errors="replace")
    except PermissionError as e:
        logger.error(f"Permission denied reading raw file {path}: {e}")
        raise HTTPException(status_code=403, detail=f"Permission denied: cannot read file {path}")
    except UnicodeDecodeError:
        # Binary file - try to read as binary and decode with errors='replace'
        try:
            raw = file_path.read_bytes().decode("utf-8", errors="replace")
        except Exception as e:
            logger.error(f"Error reading binary raw file {path}: {e}")
            raise HTTPException(status_code=500, detail=f"Cannot read file: {str(e)}")
    except Exception as e:
        logger.error(f"Unexpected error reading raw file {path}: {e}")
        raise HTTPException(status_code=500, detail=f"Error reading file: {str(e)}")
    
    return {"vault": vault_name, "path": path, "raw": raw}


@app.get("/api/file/{vault_name}/download")
async def api_file_download(vault_name: str, path: str = Query(..., description="Relative path to file")):
    """Download a file as an attachment.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.

    Returns:
        ``FileResponse`` with ``application/octet-stream`` content-type.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    return FileResponse(
        path=str(file_path),
        filename=file_path.name,
        media_type="application/octet-stream",
    )


@app.put("/api/file/{vault_name}/save", response_model=FileSaveResponse)
async def api_file_save(
    vault_name: str,
    path: str = Query(..., description="Relative path to file"),
    body: dict = Body(...),
):
    """Save (overwrite) a file's content.

    Expects a JSON body with a ``content`` key containing the new text.
    The path is validated against traversal attacks before writing.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.
        body: JSON body with ``content`` string.

    Returns:
        ``FileSaveResponse`` confirming the write.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    content = body.get('content', '')

    try:
        file_path.write_text(content, encoding="utf-8")
        logger.info(f"File saved: {vault_name}/{path}")
        return {"status": "ok", "vault": vault_name, "path": path, "size": len(content)}
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied: vault may be read-only")
    except Exception as e:
        logger.error(f"Error saving file {vault_name}/{path}: {e}")
        raise HTTPException(status_code=500, detail=f"Error saving file: {str(e)}")


@app.delete("/api/file/{vault_name}", response_model=FileDeleteResponse)
async def api_file_delete(vault_name: str, path: str = Query(..., description="Relative path to file")):
    """Delete a file from the vault.

    The path is validated against traversal attacks before deletion.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.

    Returns:
        ``FileDeleteResponse`` confirming the deletion.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    try:
        file_path.unlink()
        logger.info(f"File deleted: {vault_name}/{path}")
        return {"status": "ok", "vault": vault_name, "path": path}
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied: vault may be read-only")
    except Exception as e:
        logger.error(f"Error deleting file {vault_name}/{path}: {e}")
        raise HTTPException(status_code=500, detail=f"Error deleting file: {str(e)}")


@app.get("/api/file/{vault_name}", response_model=FileContentResponse)
async def api_file(vault_name: str, path: str = Query(..., description="Relative path to file")):
    """Return rendered HTML and metadata for a file.

    Markdown files are parsed for frontmatter, rendered with wikilink
    support, and returned with extracted tags. Other supported file
    types are syntax-highlighted as code blocks.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.

    Returns:
        ``FileContentResponse`` with HTML, metadata, and tags.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    try:
        raw = file_path.read_text(encoding="utf-8", errors="replace")
    except PermissionError as e:
        logger.error(f"Permission denied reading file {path}: {e}")
        raise HTTPException(status_code=403, detail=f"Permission denied: cannot read file {path}")
    except UnicodeDecodeError:
        # Binary file - try to read as binary and decode with errors='replace'
        try:
            raw = file_path.read_bytes().decode("utf-8", errors="replace")
        except Exception as e:
            logger.error(f"Error reading binary file {path}: {e}")
            raise HTTPException(status_code=500, detail=f"Cannot read file: {str(e)}")
    except Exception as e:
        logger.error(f"Unexpected error reading file {path}: {e}")
        raise HTTPException(status_code=500, detail=f"Error reading file: {str(e)}")
    
    ext = file_path.suffix.lower()

    if ext == ".md":
        post = parse_markdown_file(raw)

        # Extract metadata using shared indexer logic
        tags = _extract_tags(post)

        title = post.metadata.get("title", file_path.stem.replace("-", " ").replace("_", " "))
        html_content = _render_markdown(post.content, vault_name, file_path)

        return {
            "vault": vault_name,
            "path": path,
            "title": str(title),
            "tags": tags,
            "frontmatter": dict(post.metadata) if post.metadata else {},
            "html": html_content,
            "raw_length": len(raw),
            "extension": ext,
            "is_markdown": True,
        }
    else:
        # Non-markdown: wrap in syntax-highlighted code block
        lang = EXT_TO_LANG.get(ext, "plaintext")
        escaped = html_mod.escape(raw)
        html_content = f'<pre><code class="language-{lang}">{escaped}</code></pre>'

        return {
            "vault": vault_name,
            "path": path,
            "title": file_path.name,
            "tags": [],
            "frontmatter": {},
            "html": html_content,
            "raw_length": len(raw),
            "extension": ext,
            "is_markdown": False,
        }


@app.get("/api/search", response_model=SearchResponse)
async def api_search(
    q: str = Query("", description="Search query"),
    vault: str = Query("all", description="Vault filter"),
    tag: Optional[str] = Query(None, description="Tag filter"),
):
    """Full-text search across vaults with relevance scoring.

    Supports combining free-text queries with tag filters.
    Results are ranked by a multi-factor scoring algorithm.

    Args:
        q: Free-text search string.
        vault: Vault name or ``"all"`` to search everywhere.
        tag: Comma-separated tag names to require.

    Returns:
        ``SearchResponse`` with ranked results and snippets.
    """
    results = search(q, vault_filter=vault, tag_filter=tag)
    return {"query": q, "vault_filter": vault, "tag_filter": tag, "count": len(results), "results": results}


@app.get("/api/tags", response_model=TagsResponse)
async def api_tags(vault: Optional[str] = Query(None, description="Vault filter")):
    """Return all unique tags with occurrence counts.

    Args:
        vault: Optional vault name to restrict tag aggregation.

    Returns:
        ``TagsResponse`` with tags sorted by descending count.
    """
    tags = get_all_tags(vault_filter=vault)
    return {"vault_filter": vault, "tags": tags}


@app.get("/api/tree-search", response_model=TreeSearchResponse)
async def api_tree_search(
    q: str = Query("", description="Search query"),
    vault: str = Query("all", description="Vault filter"),
):
    """Search for files and directories in the tree structure using pre-built index.
    
    Uses the in-memory path index for instant filtering without filesystem access.
    
    Args:
        q: Search string to match against file/directory paths.
        vault: Vault name or "all" to search everywhere.
        
    Returns:
        ``TreeSearchResponse`` with matching paths.
    """
    if not q:
        return {"query": q, "vault_filter": vault, "results": []}
    
    query_lower = q.lower()
    results = []
    
    vaults_to_search = [vault] if vault != "all" else list(path_index.keys())
    
    for vault_name in vaults_to_search:
        vault_paths = path_index.get(vault_name, [])
        
        for entry in vault_paths:
            path_lower = entry["path"].lower()
            name_lower = entry["name"].lower()
            
            if query_lower in name_lower or query_lower in path_lower:
                results.append({
                    "vault": vault_name,
                    "path": entry["path"],
                    "name": entry["name"],
                    "type": entry["type"],
                    "matched_path": entry["path"],
                })
    
    return {"query": q, "vault_filter": vault, "results": results}


@app.get("/api/index/reload", response_model=ReloadResponse)
async def api_reload():
    """Force a full re-index of all configured vaults.

    Returns:
        ``ReloadResponse`` with per-vault file and tag counts.
    """
    stats = await reload_index()
    return {"status": "ok", "vaults": stats}


@app.get("/api/image/{vault_name}")
async def api_image(vault_name: str, path: str = Query(..., description="Relative path to image")):
    """Serve an image file with proper MIME type.

    Args:
        vault_name: Name of the vault.
        path: Relative file path within the vault.

    Returns:
        Image file with appropriate content-type header.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_root = Path(vault_data["path"])
    file_path = _resolve_safe_path(vault_root, path)

    if not file_path.exists() or not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"Image not found: {path}")

    # Determine MIME type
    mime_type, _ = mimetypes.guess_type(str(file_path))
    if not mime_type:
        # Default to octet-stream if unknown
        mime_type = "application/octet-stream"

    try:
        # Read and return the image file
        content = file_path.read_bytes()
        return Response(content=content, media_type=mime_type)
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied")
    except Exception as e:
        logger.error(f"Error serving image {vault_name}/{path}: {e}")
        raise HTTPException(status_code=500, detail=f"Error serving image: {str(e)}")


@app.post("/api/attachments/rescan/{vault_name}")
async def api_rescan_attachments(vault_name: str):
    """Rescan attachments for a specific vault.

    Args:
        vault_name: Name of the vault to rescan.

    Returns:
        Dict with status and attachment count.
    """
    vault_data = get_vault_data(vault_name)
    if not vault_data:
        raise HTTPException(status_code=404, detail=f"Vault '{vault_name}' not found")

    vault_path = vault_data["path"]
    count = await rescan_vault_attachments(vault_name, vault_path)
    
    logger.info(f"Rescanned attachments for vault '{vault_name}': {count} attachments")
    return {"status": "ok", "vault": vault_name, "attachment_count": count}


@app.get("/api/attachments/stats")
async def api_attachment_stats(vault: Optional[str] = Query(None, description="Vault filter")):
    """Get attachment statistics for vaults.

    Args:
        vault: Optional vault name to filter stats.

    Returns:
        Dict with vault names as keys and attachment counts as values.
    """
    stats = get_attachment_stats(vault)
    return {"vaults": stats}


# ---------------------------------------------------------------------------
# Static files & SPA fallback
# ---------------------------------------------------------------------------

if FRONTEND_DIR.exists():
    app.mount("/static", StaticFiles(directory=str(FRONTEND_DIR)), name="static")

    @app.get("/{full_path:path}")
    async def serve_spa(full_path: str):
        """Serve the SPA index.html for all non-API routes."""
        index_file = FRONTEND_DIR / "index.html"
        if index_file.exists():
            return HTMLResponse(content=index_file.read_text(encoding="utf-8"))
        raise HTTPException(status_code=404, detail="Frontend not found")