import logging
import os
import re
import secrets
import shutil
import time
from pathlib import Path

from fastapi import APIRouter, Depends, File, HTTPException, UploadFile, Query
from fastapi.responses import StreamingResponse

from config import VOLUME_ROOT
from rbac import require_admin

router = APIRouter()
logger = logging.getLogger(__name__)
BASE = Path(VOLUME_ROOT)

MAX_UPLOAD_SIZE = 100 * 1024 * 1024  # 100 MB
BLOCKED_DIRS = {"@appstore", "@docker", "@eaDir", "@S2S", "@sharesnap", "@tmp", "docker", "homes", "backups"}

# Download token storage: {token: (path, expiry_timestamp)}
_download_tokens = {}
TOKEN_EXPIRY = 300  # 5 minutes


_BASE_RESOLVED = str(BASE.resolve())


def _safe_path(path: str) -> Path:
    # Strip leading slashes to prevent absolute path interpretation
    path = path.lstrip("/")
    target = (BASE / path).resolve()
    if not str(target).startswith(_BASE_RESOLVED):
        raise ValueError("forbidden")
    # Block access to sensitive directories
    rel = target.relative_to(BASE.resolve())
    if rel.parts and rel.parts[0] in BLOCKED_DIRS:
        raise ValueError("forbidden")
    return target


def _is_safe_symlink(item: Path) -> bool:
    """Check if a symlink resolves to a path within BASE and not in blocked dirs."""
    if not item.is_symlink():
        return True
    try:
        resolved = item.resolve()
        if not str(resolved).startswith(_BASE_RESOLVED):
            return False
        rel = resolved.relative_to(BASE.resolve())
        if rel.parts and rel.parts[0] in BLOCKED_DIRS:
            return False
        return True
    except (OSError, ValueError):
        return False


def _sanitize_filename(name: str) -> str:
    name = os.path.basename(name)
    name = name.replace("\x00", "").replace("/", "").replace("\\", "")
    name = re.sub(r"\.\.+", ".", name)
    name = name.strip(". ")
    if not name:
        raise ValueError("invalid filename")
    return name


@router.get("/browse")
def browse(path: str = ""):
    try:
        target = _safe_path(path)
    except ValueError:
        raise HTTPException(status_code=403, detail="Access denied")

    # Check if we have permission to read the directory
    try:
        items = list(target.iterdir())
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied")
    except OSError as e:
        logger.error(f"Error reading directory {target}: {e}")
        raise HTTPException(status_code=500, detail="Error reading directory")

    entries = []
    for item in sorted(items):
        try:
            if not _is_safe_symlink(item):
                continue
            st = item.stat()
            entries.append({"name": item.name, "is_dir": item.is_dir(), "size": st.st_size if item.is_file() else 0})
        except (PermissionError, OSError):
            continue
    return {"path": str(target.relative_to(BASE)), "entries": entries}


@router.post("/download-token")
def create_download_token(path: str):
    """Generate a temporary download token for large file downloads."""
    try:
        target = _safe_path(path)
        if not target.exists():
            raise HTTPException(status_code=404, detail="File not found")

        # Clean up expired tokens
        now = time.time()
        expired = [t for t, (_, exp) in _download_tokens.items() if exp < now]
        for t in expired:
            del _download_tokens[t]

        # Generate new token
        token = secrets.token_urlsafe(32)
        _download_tokens[token] = (str(target), now + TOKEN_EXPIRY)

        return {"token": token, "expires_in": TOKEN_EXPIRY}
    except ValueError:
        raise HTTPException(status_code=403, detail="Access denied")


@router.get("/download")
def download(path: str = None, token: str = Query(None)):
    """Download a file. Supports both authenticated access (path param) and token-based access (token param)."""
    try:
        if token:
            # Token-based download (no auth required)
            if token not in _download_tokens:
                raise HTTPException(status_code=403, detail="Invalid or expired token")

            file_path, expiry = _download_tokens[token]
            if time.time() > expiry:
                del _download_tokens[token]
                raise HTTPException(status_code=403, detail="Token expired")

            # Consume token after use
            del _download_tokens[token]
            target = Path(file_path)
        else:
            # Authenticated download
            if not path:
                raise HTTPException(status_code=400, detail="Path or token required")
            target = _safe_path(path)

        if not target.exists():
            raise HTTPException(status_code=404, detail="File not found")

        def file_iterator():
            with open(target, "rb") as f:
                while chunk := f.read(8192 * 1024):  # 8MB chunks
                    yield chunk

        return StreamingResponse(
            file_iterator(),
            media_type="application/octet-stream",
            headers={"Content-Disposition": f'attachment; filename="{target.name}"'}
        )
    except ValueError:
        raise HTTPException(status_code=403, detail="Access denied")


@router.post("/upload", dependencies=[Depends(require_admin())])
async def upload(path: str, file: UploadFile = File(...)):
    try:
        safe_name = _sanitize_filename(file.filename)
        target = _safe_path(path) / safe_name
    except ValueError:
        raise HTTPException(status_code=403, detail="Access denied")
    # Stream with size check
    total = 0
    with open(target, "wb") as f:
        while chunk := await file.read(1024 * 1024):
            total += len(chunk)
            if total > MAX_UPLOAD_SIZE:
                f.close()
                target.unlink(missing_ok=True)
                raise HTTPException(status_code=413, detail="File too large (max 100MB)")
            f.write(chunk)
    return {"ok": True}


@router.delete("/delete", dependencies=[Depends(require_admin())])
def delete(path: str, recursive: bool = False):
    try:
        target = _safe_path(path)
    except ValueError:
        raise HTTPException(status_code=403, detail="Access denied")

    if target == BASE.resolve():
        raise HTTPException(status_code=403, detail="Cannot delete base root")

    try:
        if target.is_dir():
            if not recursive:
                raise HTTPException(status_code=400, detail="Directory deletion requires recursive=true")
            shutil.rmtree(target)
        else:
            target.unlink()
    except HTTPException:
        raise
    except FileNotFoundError:
        raise HTTPException(status_code=404, detail="Path not found")
    except PermissionError:
        raise HTTPException(status_code=403, detail="Permission denied")
    except OSError as exc:
        logger.exception("OS error during file deletion: %s", path)
        raise HTTPException(status_code=400, detail="Failed to delete file")
    return {"ok": True}