from typing import List, Literal, Optional, TypedDict

from langchain_core.documents import Document
from langchain_core.prompts import ChatPromptTemplate
from langgraph.graph import END, START, StateGraph
from pydantic import BaseModel, Field
from qdrant_client.http.models import (
    FieldCondition,
    Filter,
    MatchValue,
)

from clients import LLM, VECTOR_STORE


class RetrievalState(TypedDict):
    """State for the agentic retrieval graph."""

    original_query: str
    current_query: str
    category: Optional[str]
    topic: Optional[str]
    documents: List[Document]
    relevant_documents: List[Document]
    generation: str
    retry_count: int
    max_retries: int


class GradeDocuments(BaseModel):
    """Grade whether a document is relevant to the query."""

    is_relevant: Literal["yes", "no"] = Field(
        description="Is the document relevant to the query? 'yes' or 'no'"
    )
    reason: str = Field(description="Brief reason for the relevance decision")


def retrieve_documents(state: RetrievalState) -> RetrievalState:
    """Retrieve documents from vector store."""
    query = state["current_query"]
    category = state.get("category")
    topic = state.get("topic")

    # Build Qdrant filter
    conditions = []
    if category:
        conditions.append(
            FieldCondition(key="metadata.category", match=MatchValue(value=category))
        )
    if topic:
        conditions.append(
            FieldCondition(key="metadata.topic", match=MatchValue(value=topic))
        )

    qdrant_filter = Filter(must=conditions) if conditions else None

    documents = VECTOR_STORE.similarity_search(
        query,
        k=5,
        filter=qdrant_filter,
    )

    return {**state, "documents": documents}


def grade_documents(state: RetrievalState) -> RetrievalState:
    """Grade documents for relevance using LLM."""
    query = state["original_query"]
    documents = state["documents"]

    if not documents:
        return {**state, "relevant_documents": []}

    # Create grader with structured output
    grader_llm = LLM.with_structured_output(GradeDocuments)

    grading_prompt = ChatPromptTemplate.from_messages(
        [
            (
                "system",
                """You are a grader assessing relevance of a retrieved document to a user query.
        
If the document contains keywords or semantic meaning related to the query, grade it as relevant.
Be lenient - even partial relevance should be marked as 'yes'.
Only mark 'no' if the document is completely unrelated.""",
            ),
            (
                "human",
                """Query: {query}

Document content: {document}

Is this document relevant to the query?""",
            ),
        ]
    )

    relevant_docs = []
    for doc in documents:
        try:
            result = grader_llm.invoke(
                grading_prompt.format_messages(
                    query=query,
                    document=doc.page_content[:1000],  # Limit content length
                )
            )
            if result.is_relevant == "yes":
                relevant_docs.append(doc)
        except Exception:
            # If grading fails, include the document (fail-safe)
            relevant_docs.append(doc)

    return {**state, "relevant_documents": relevant_docs}


def rewrite_query(state: RetrievalState) -> RetrievalState:
    """Rewrite the query for better retrieval."""
    original_query = state["original_query"]
    retry_count = state["retry_count"]

    rewrite_prompt = ChatPromptTemplate.from_messages(
        [
            (
                "system",
                """You are an expert at reformulating search queries.
Given the original query, generate a better search query that might retrieve more relevant documents.

Focus on:
- Extracting key concepts and entities
- Using synonyms or related terms
- Being more specific or more general as appropriate

Return ONLY the rewritten query, nothing else.""",
            ),
            ("human", "Original query: {query}\n\nRewritten query:"),
        ]
    )

    response = LLM.invoke(rewrite_prompt.format_messages(query=original_query))

    new_query = response.content.strip()

    return {
        **state,
        "current_query": new_query,
        "retry_count": retry_count + 1,
    }


def generate_response(state: RetrievalState) -> RetrievalState:
    """Generate final response from relevant documents."""
    relevant_docs = state["relevant_documents"]

    if not relevant_docs:
        return {**state, "generation": "No relevant memories found."}

    # Format documents
    formatted = []
    for i, doc in enumerate(relevant_docs, 1):
        meta = doc.metadata
        formatted.append(
            f"{i}. [{meta.get('category', 'N/A')}/{meta.get('topic', 'N/A')}]: {doc.page_content}"
        )

    return {**state, "generation": "\n".join(formatted)}


def should_retry(state: RetrievalState) -> Literal["rewrite", "generate"]:
    """Decide whether to retry with a rewritten query."""
    relevant_docs = state["relevant_documents"]
    retry_count = state["retry_count"]
    max_retries = state["max_retries"]

    # If we have relevant docs, generate response
    if relevant_docs:
        return "generate"

    # If no relevant docs and we can still retry, rewrite query
    if retry_count < max_retries:
        return "rewrite"

    # Max retries reached, generate (empty) response
    return "generate"


def build_retrieval_graph():
    workflow = StateGraph(RetrievalState)

    # Add nodes
    workflow.add_node("retrieve", retrieve_documents)
    workflow.add_node("grade", grade_documents)
    workflow.add_node("rewrite", rewrite_query)
    workflow.add_node("generate", generate_response)

    # Add edges
    workflow.add_edge(START, "retrieve")
    workflow.add_edge("retrieve", "grade")
    workflow.add_conditional_edges(
        "grade",
        should_retry,
        {
            "rewrite": "rewrite",
            "generate": "generate",
        },
    )
    workflow.add_edge("rewrite", "retrieve")
    workflow.add_edge("generate", END)

    return workflow.compile()