import asyncio
from datetime import datetime, timezone
from typing import Optional
from fastapi import APIRouter, HTTPException, Depends, Query
from pydantic import BaseModel
from firebase_admin import auth as firebase_auth
from app.internal.auth import require_admin_token
from app.internal import firestore as fstore
from app.internal import audit

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

VALID_ROLES = {"admin", "operator", "viewer"}


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

class UserCreate(BaseModel):
    email: str
    role: str = "viewer"
    display_name: Optional[str] = None
    owned_node_ids: list[str] = []


class UserUpdate(BaseModel):
    role: Optional[str] = None
    owned_node_ids: Optional[list[str]] = None
    display_name: Optional[str] = None


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

def _ms_to_iso(ms: Optional[int]) -> Optional[str]:
    if ms is None:
        return None
    return datetime.fromtimestamp(ms / 1000, tz=timezone.utc).isoformat()


def _extract_role_nodes(fb_user: firebase_auth.UserRecord) -> tuple[str, list[str]]:
    claims = fb_user.custom_claims or {}
    if claims.get("role") == "admin" or claims.get("admin"):
        role = "admin"
    else:
        role = claims.get("role", "viewer")
        if role not in VALID_ROLES:
            role = "viewer"
    owned_node_ids = claims.get("owned_node_ids") or []
    return role, owned_node_ids


def _format_user(fb_user: firebase_auth.UserRecord, link: Optional[dict] = None) -> dict:
    role, owned_node_ids = _extract_role_nodes(fb_user)
    return {
        "uid": fb_user.uid,
        "email": fb_user.email,
        "display_name": fb_user.display_name,
        "role": role,
        "owned_node_ids": owned_node_ids,
        "disabled": fb_user.disabled,
        "creation_time": _ms_to_iso(fb_user.user_metadata.creation_timestamp),
        "last_sign_in": _ms_to_iso(fb_user.user_metadata.last_sign_in_timestamp),
        "discord_linked": bool(link and link.get("discord_user_id")),
        "discord_username": link.get("discord_username") if link else None,
        "discord_user_id": link.get("discord_user_id") if link else None,
    }


def _list_fb_users() -> list[firebase_auth.UserRecord]:
    users: list[firebase_auth.UserRecord] = []
    page = firebase_auth.list_users()
    while page:
        users.extend(page.users)
        page = page.get_next_page()
    return users


# ---------------------------------------------------------------------------
# Endpoints
# ---------------------------------------------------------------------------

@router.get("")
async def list_users(decoded: dict = Depends(require_admin_token)):
    """List all Firebase Auth users with role, node ownership, and Discord link status."""
    fb_users = await asyncio.to_thread(_list_fb_users)

    links: list[Optional[dict]] = await asyncio.gather(*[
        fstore.doc_get("firebase_discord_links", u.uid) for u in fb_users
    ])

    return [_format_user(u, lnk) for u, lnk in zip(fb_users, links)]


@router.post("")
async def create_user(body: UserCreate, decoded: dict = Depends(require_admin_token)):
    """Create a new Firebase Auth user and set their role. Returns a one-time invite link."""
    if body.role not in VALID_ROLES:
        raise HTTPException(400, f"Invalid role. Must be one of: {', '.join(sorted(VALID_ROLES))}")
    if body.role == "operator" and not body.owned_node_ids:
        raise HTTPException(400, "Operator role requires at least one owned node.")

    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(
            firebase_auth.create_user,
            email=body.email,
            display_name=body.display_name or "",
            email_verified=False,
        )
    except firebase_auth.EmailAlreadyExistsError:
        raise HTTPException(409, "A user with this email already exists.")
    except Exception as e:
        raise HTTPException(400, f"Failed to create user: {e}")

    # Set custom claims
    claims: dict = {"role": body.role, "owned_node_ids": body.owned_node_ids}
    if body.role == "admin":
        claims["admin"] = True
    await asyncio.to_thread(firebase_auth.set_custom_user_claims, fb_user.uid, claims)

    # Write Firestore profile
    now = datetime.now(timezone.utc).isoformat()
    await fstore.doc_set("user_profiles", fb_user.uid, {
        "uid": fb_user.uid,
        "email": body.email,
        "display_name": body.display_name or "",
        "role": body.role,
        "owned_node_ids": body.owned_node_ids,
        "created_by_uid": decoded["uid"],
        "created_at": now,
    }, merge=False)

    # Generate a one-time invite/password-reset link
    invite_link: Optional[str] = None
    try:
        invite_link = await asyncio.to_thread(firebase_auth.generate_password_reset_link, body.email)
    except Exception:
        pass

    await audit.write_audit(
        actor_uid=decoded["uid"],
        actor_email=decoded.get("email", ""),
        action="user.create",
        target_uid=fb_user.uid,
        target_email=body.email,
        details={"role": body.role, "owned_node_ids": body.owned_node_ids},
    )

    return {**_format_user(fb_user), "invite_link": invite_link}


@router.get("/{uid}")
async def get_user(uid: str, decoded: dict = Depends(require_admin_token)):
    """Get a single user with full detail, including recent sessions."""
    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    except firebase_auth.UserNotFoundError:
        raise HTTPException(404, "User not found.")

    link, raw_sessions = await asyncio.gather(
        fstore.doc_get("firebase_discord_links", uid),
        fstore.collection_where("user_sessions", [("uid", "==", uid)]),
    )

    raw_sessions.sort(key=lambda s: s.get("timestamp", ""), reverse=True)

    return {
        **_format_user(fb_user, link),
        "sessions": raw_sessions[:20],
    }


@router.patch("/{uid}")
async def update_user(uid: str, body: UserUpdate, decoded: dict = Depends(require_admin_token)):
    """Update a user's role, owned nodes, or display name."""
    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    except firebase_auth.UserNotFoundError:
        raise HTTPException(404, "User not found.")

    current_role, current_nodes = _extract_role_nodes(fb_user)
    new_role = body.role if body.role is not None else current_role
    new_nodes = body.owned_node_ids if body.owned_node_ids is not None else current_nodes

    if new_role not in VALID_ROLES:
        raise HTTPException(400, f"Invalid role. Must be one of: {', '.join(sorted(VALID_ROLES))}")
    if new_role == "operator" and not new_nodes:
        raise HTTPException(400, "Operator role requires at least one owned node.")

    # Merge with existing claims (preserve any other claims already set)
    existing_claims: dict = dict(fb_user.custom_claims or {})
    new_claims = {**existing_claims, "role": new_role, "owned_node_ids": new_nodes}
    if new_role == "admin":
        new_claims["admin"] = True
    else:
        new_claims.pop("admin", None)

    await asyncio.to_thread(firebase_auth.set_custom_user_claims, uid, new_claims)

    if body.display_name is not None:
        await asyncio.to_thread(firebase_auth.update_user, uid, display_name=body.display_name)

    profile_data: dict = {"uid": uid, "role": new_role, "owned_node_ids": new_nodes}
    if body.display_name is not None:
        profile_data["display_name"] = body.display_name
    await fstore.doc_set("user_profiles", uid, profile_data, merge=True)

    await audit.write_audit(
        actor_uid=decoded["uid"],
        actor_email=decoded.get("email", ""),
        action="user.update",
        target_uid=uid,
        target_email=fb_user.email,
        details={
            "old_role": current_role,
            "new_role": new_role,
            "old_nodes": current_nodes,
            "new_nodes": new_nodes,
        },
    )

    updated: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    link = await fstore.doc_get("firebase_discord_links", uid)
    return _format_user(updated, link)


@router.post("/{uid}/disable")
async def disable_user(uid: str, decoded: dict = Depends(require_admin_token)):
    """Disable a user — they can no longer sign in but their data is preserved."""
    if uid == decoded.get("uid"):
        raise HTTPException(400, "Cannot disable your own account.")
    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    except firebase_auth.UserNotFoundError:
        raise HTTPException(404, "User not found.")

    await asyncio.to_thread(firebase_auth.update_user, uid, disabled=True)

    await audit.write_audit(
        actor_uid=decoded["uid"],
        actor_email=decoded.get("email", ""),
        action="user.disable",
        target_uid=uid,
        target_email=fb_user.email,
    )

    return {"ok": True}


@router.post("/{uid}/enable")
async def enable_user(uid: str, decoded: dict = Depends(require_admin_token)):
    """Re-enable a previously disabled user."""
    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    except firebase_auth.UserNotFoundError:
        raise HTTPException(404, "User not found.")

    await asyncio.to_thread(firebase_auth.update_user, uid, disabled=False)

    await audit.write_audit(
        actor_uid=decoded["uid"],
        actor_email=decoded.get("email", ""),
        action="user.enable",
        target_uid=uid,
        target_email=fb_user.email,
    )

    return {"ok": True}


@router.delete("/{uid}")
async def delete_user(uid: str, decoded: dict = Depends(require_admin_token)):
    """Permanently delete a user from Firebase Auth and clean up Firestore data."""
    if uid == decoded.get("uid"):
        raise HTTPException(400, "Cannot delete your own account.")

    try:
        fb_user: firebase_auth.UserRecord = await asyncio.to_thread(firebase_auth.get_user, uid)
    except firebase_auth.UserNotFoundError:
        raise HTTPException(404, "User not found.")

    email = fb_user.email

    # Clean up Discord link if present
    link = await fstore.doc_get("firebase_discord_links", uid)
    if link and link.get("discord_user_id"):
        await asyncio.gather(
            fstore.doc_delete("discord_links", link["discord_user_id"]),
            fstore.doc_delete("firebase_discord_links", uid),
        )

    # Delete Firestore profile (sessions are kept for audit history)
    await fstore.doc_delete("user_profiles", uid)

    # Delete from Firebase Auth
    await asyncio.to_thread(firebase_auth.delete_user, uid)

    await audit.write_audit(
        actor_uid=decoded["uid"],
        actor_email=decoded.get("email", ""),
        action="user.delete",
        target_uid=uid,
        target_email=email,
    )

    return {"ok": True}