"""Admin panel API — System Prompt, TOV configuration, and User management.

Only users with role='admin' can access these endpoints.
All previous prompt versions are preserved for FCA audit trail.
"""
from __future__ import annotations

import uuid
from datetime import datetime, timezone

import bcrypt
from fastapi import APIRouter, Depends, HTTPException, status
from pydantic import BaseModel
from sqlalchemy import select, update, func
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.auth import get_current_user
from app.database import get_db
from app.models.system_prompt import SystemPrompt
from app.models.user import User

router = APIRouter()


def require_admin(current_user: User = Depends(get_current_user)) -> User:
    if current_user.role != "admin":
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Admin access required")
    return current_user


class SystemPromptCreate(BaseModel):
    label: str
    system_text: str
    tov_text: str | None = None
    tov_banned_phrases: str = "say hello to,give you peace of mind,it's a win-win,win-win,game-changer"
    short_title_max: int = 32
    long_body_max: int = 128
    cta_max: int = 50


class SystemPromptOut(BaseModel):
    id: uuid.UUID
    version: int
    label: str
    system_text: str
    tov_text: str | None = None
    tov_banned_phrases: str
    short_title_max: int
    long_body_max: int
    cta_max: int
    is_active: bool
    created_at: datetime

    class Config:
        from_attributes = True


@router.get("/system-prompts", response_model=list[SystemPromptOut])
async def list_system_prompts(
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    result = await db.execute(select(SystemPrompt).order_by(SystemPrompt.version.desc()))
    return result.scalars().all()


@router.get("/system-prompts/active", response_model=SystemPromptOut)
async def get_active_prompt(
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    result = await db.execute(select(SystemPrompt).where(SystemPrompt.is_active == True))  # noqa: E712
    prompt = result.scalar_one_or_none()
    if not prompt:
        raise HTTPException(status_code=404, detail="No active system prompt")
    return prompt


@router.post("/system-prompts", response_model=SystemPromptOut, status_code=201)
async def create_system_prompt(
    payload: SystemPromptCreate,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    # Determine next version number
    result = await db.execute(select(SystemPrompt).order_by(SystemPrompt.version.desc()).limit(1))
    latest = result.scalar_one_or_none()
    next_version = (latest.version + 1) if latest else 1

    prompt = SystemPrompt(
        version=next_version,
        created_by_id=admin.id,
        created_at=datetime.now(timezone.utc),
        **payload.model_dump(),
    )
    db.add(prompt)
    await db.commit()
    await db.refresh(prompt)
    return prompt


@router.post("/system-prompts/{prompt_id}/activate", response_model=SystemPromptOut)
async def activate_system_prompt(
    prompt_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    # Deactivate all
    await db.execute(update(SystemPrompt).values(is_active=False))

    result = await db.execute(select(SystemPrompt).where(SystemPrompt.id == prompt_id))
    prompt = result.scalar_one_or_none()
    if not prompt:
        raise HTTPException(status_code=404, detail="System prompt not found")

    prompt.is_active = True
    await db.commit()
    await db.refresh(prompt)
    return prompt


@router.put("/system-prompts/{prompt_id}", response_model=SystemPromptOut)
async def update_system_prompt(
    prompt_id: uuid.UUID,
    payload: SystemPromptCreate,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    """Update creates a new version (immutable audit trail) and deactivates old."""
    result = await db.execute(select(SystemPrompt).where(SystemPrompt.id == prompt_id))
    old = result.scalar_one_or_none()
    if not old:
        raise HTTPException(status_code=404, detail="System prompt not found")

    was_active = old.is_active
    old.is_active = False

    new_version = old.version + 1
    new_prompt = SystemPrompt(
        version=new_version,
        created_by_id=admin.id,
        created_at=datetime.now(timezone.utc),
        is_active=was_active,
        **payload.model_dump(),
    )
    db.add(new_prompt)
    await db.commit()
    await db.refresh(new_prompt)
    return new_prompt


# ── User management ───────────────────────────────────────────────────────────

class UserOut(BaseModel):
    id: uuid.UUID
    email: str
    role: str
    created_at: datetime

    class Config:
        from_attributes = True


class UserCreate(BaseModel):
    email: str
    password: str
    role: str = "user"


class UserUpdate(BaseModel):
    email: str | None = None
    role: str | None = None
    password: str | None = None


@router.get("/users", response_model=list[UserOut])
async def list_users(
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    result = await db.execute(select(User).order_by(User.created_at))
    return result.scalars().all()


@router.post("/users", response_model=UserOut, status_code=201)
async def create_user(
    payload: UserCreate,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    existing = await db.execute(select(User).where(func.lower(User.email) == payload.email.lower()))
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=409, detail="Email already registered")

    if payload.role not in ("user", "admin"):
        raise HTTPException(status_code=422, detail="Role must be 'user' or 'admin'")

    hashed = bcrypt.hashpw(payload.password.encode(), bcrypt.gensalt()).decode()
    user = User(email=payload.email.lower(), hashed_password=hashed, role=payload.role)
    db.add(user)
    await db.commit()
    await db.refresh(user)
    return user


@router.patch("/users/{user_id}", response_model=UserOut)
async def update_user(
    user_id: uuid.UUID,
    payload: UserUpdate,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")

    if payload.role is not None:
        if payload.role not in ("user", "admin"):
            raise HTTPException(status_code=422, detail="Role must be 'user' or 'admin'")
        # Prevent removing last admin
        if user.role == "admin" and payload.role != "admin":
            count = await db.execute(select(func.count()).select_from(User).where(User.role == "admin"))
            if count.scalar() <= 1:
                raise HTTPException(status_code=409, detail="Cannot demote the only admin")
        user.role = payload.role

    if payload.email is not None:
        user.email = payload.email.lower()

    if payload.password is not None:
        user.hashed_password = bcrypt.hashpw(payload.password.encode(), bcrypt.gensalt()).decode()

    await db.commit()
    await db.refresh(user)
    return user


@router.delete("/users/{user_id}", status_code=204)
async def delete_user(
    user_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    admin: User = Depends(require_admin),
):
    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")

    if user.id == admin.id:
        raise HTTPException(status_code=409, detail="Cannot delete your own account")

    if user.role == "admin":
        count = await db.execute(select(func.count()).select_from(User).where(User.role == "admin"))
        if count.scalar() <= 1:
            raise HTTPException(status_code=409, detail="Cannot delete the only admin")

    await db.delete(user)
    await db.commit()