"""Standalone AI assistant chat service with RAG context.

Provides persistent conversation history for general IT questions
with semantic search over the team's flow library.

Uses Anthropic prompt caching to reduce cost on multi-turn conversations:
- The static system prompt is cached (ephemeral, 5-min TTL)
- The conversation history prefix is cached via a breakpoint on the
  last existing message before the new user input
"""
import logging
from typing import Any
from uuid import UUID

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import settings
from app.models.assistant_chat import AssistantChat
from app.services.rag_service import search as rag_search, build_rag_context, extract_suggested_flows

logger = logging.getLogger(__name__)

ASSISTANT_SYSTEM_PROMPT = """You are a Senior Systems and Network Engineer with 15+ years of experience working in Managed Service Provider (MSP) environments. You specialize in:
- Windows Server, Active Directory, Group Policy, and Hybrid Identity (Entra ID)
- Networking (TCP/IP, DNS, DHCP, VPN, firewall troubleshooting, Cisco/Fortinet)
- Virtualization (VMware, Hyper-V) and cloud platforms (Azure, AWS, M365)
- Endpoint management, RMM tools, and PSA platforms (ConnectWise, Datto, Kaseya)
- PowerShell scripting and automation

When answering:
- Be direct and actionable — MSP engineers need fast, practical answers
- Include specific commands, paths, and config values when relevant
- Mention potential risks or gotchas before suggesting changes
- If a relevant troubleshooting flow exists in the team's library, reference it
- Keep responses concise but thorough — prefer bullet points and code blocks
- Format code with proper markdown code blocks
"""


async def _call_ai(
    system_base: str,
    rag_context: str,
    history: list[dict[str, Any]],
    new_message: str,
    max_tokens: int = 4096,
) -> tuple[str, int, int]:
    """Call the AI with prompt caching when using Anthropic.

    Caching strategy:
    - System prompt base: cached (stable across all turns)
    - RAG context: NOT cached (changes per query)
    - Conversation history prefix: cached via breakpoint on last
      existing message (stable — only new user message is uncached)
    """
    if settings.AI_PROVIDER == "anthropic" and settings.ANTHROPIC_API_KEY:
        return await _call_anthropic_cached(
            system_base, rag_context, history, new_message, max_tokens
        )

    # Fallback: generic provider (Gemini, etc.)
    from app.core.ai_provider import get_ai_provider

    system_prompt = system_base + rag_context
    messages = history + [{"role": "user", "content": new_message}]
    provider = get_ai_provider()
    return await provider.generate_text(
        system_prompt=system_prompt,
        messages=messages,
        max_tokens=max_tokens,
    )


async def _call_anthropic_cached(
    system_base: str,
    rag_context: str,
    history: list[dict[str, Any]],
    new_message: str,
    max_tokens: int,
) -> tuple[str, int, int]:
    """Call Anthropic with prompt caching on system prompt and history.

    Uses structured system blocks so the static base prompt is cached
    independently from the per-query RAG context.
    """
    import anthropic

    client = anthropic.AsyncAnthropic(
        api_key=settings.ANTHROPIC_API_KEY,
        timeout=settings.AI_REQUEST_TIMEOUT_SECONDS,
    )

    # System prompt as structured blocks:
    # Block 1: static base prompt (cached)
    # Block 2: RAG context (changes per query, not cached)
    system_blocks: list[dict[str, Any]] = [
        {
            "type": "text",
            "text": system_base,
            "cache_control": {"type": "ephemeral"},
        },
    ]
    if rag_context:
        system_blocks.append({"type": "text", "text": rag_context})

    # Build messages with cache breakpoint on conversation history
    messages: list[dict[str, Any]] = []
    for msg in history:
        messages.append({"role": msg["role"], "content": msg["content"]})

    # Place cache breakpoint on the last history message so the entire
    # conversation prefix is cached across turns
    if messages:
        last = messages[-1]
        messages[-1] = {
            "role": last["role"],
            "content": [
                {
                    "type": "text",
                    "text": last["content"],
                    "cache_control": {"type": "ephemeral"},
                }
            ],
        }

    # Add the new user message (uncached — it's new each turn)
    messages.append({"role": "user", "content": new_message})

    response = await client.messages.create(
        model=settings.AI_MODEL_ANTHROPIC,
        max_tokens=max_tokens,
        system=system_blocks,
        messages=messages,
    )

    text = response.content[0].text
    usage = response.usage
    input_tokens = usage.input_tokens
    output_tokens = usage.output_tokens

    # Log cache performance
    cache_read = getattr(usage, "cache_read_input_tokens", 0) or 0
    cache_creation = getattr(usage, "cache_creation_input_tokens", 0) or 0
    if cache_read or cache_creation:
        logger.info(
            "Anthropic cache: read=%d creation=%d input=%d output=%d",
            cache_read, cache_creation, input_tokens, output_tokens,
        )

    return text, input_tokens, output_tokens


def _auto_title(message: str) -> str:
    """Generate a short title from the first user message."""
    title = message.strip()[:100]
    if len(message) > 100:
        title = title.rsplit(" ", 1)[0] + "..."
    return title


async def create_chat(
    user_id: UUID,
    account_id: UUID,
    db: AsyncSession,
) -> AssistantChat:
    """Create a new empty chat."""
    chat = AssistantChat(
        user_id=user_id,
        account_id=account_id,
        messages=[],
    )
    db.add(chat)
    await db.flush()
    return chat


async def send_message(
    chat_id: UUID,
    user_id: UUID,
    account_id: UUID,
    message: str,
    db: AsyncSession,
) -> tuple[str, list[dict[str, Any]], AssistantChat]:
    """Send a user message and get AI response.

    Returns (ai_content, suggested_flows, chat).
    """
    result = await db.execute(
        select(AssistantChat).where(
            AssistantChat.id == chat_id,
            AssistantChat.user_id == user_id,
        )
    )
    chat = result.scalar_one_or_none()
    if not chat:
        raise ValueError("Chat not found")

    # Auto-title from first message
    if chat.message_count == 0:
        chat.title = _auto_title(message)

    # RAG search
    rag_results = await rag_search(
        query=message,
        account_id=account_id,
        db=db,
        limit=8,
    )

    rag_context = build_rag_context(rag_results)

    # Build messages for AI
    ai_messages: list[dict[str, Any]] = []
    for msg in chat.messages:
        if msg["role"] in ("user", "assistant"):
            ai_messages.append({"role": msg["role"], "content": msg["content"]})

    # Call AI with prompt caching (Anthropic) or generic provider
    ai_content, input_tokens, output_tokens = await _call_ai(
        system_base=ASSISTANT_SYSTEM_PROMPT,
        rag_context=rag_context,
        history=ai_messages,
        new_message=message,
    )

    # Update chat
    msgs = list(chat.messages)
    msgs.append({"role": "user", "content": message})
    msgs.append({"role": "assistant", "content": ai_content})
    chat.messages = msgs
    chat.message_count += 2
    chat.total_input_tokens += input_tokens
    chat.total_output_tokens += output_tokens

    suggested_flows = extract_suggested_flows(rag_results)

    return ai_content, suggested_flows, chat