"""
api.py — FastAPI REST endpoint for DocMind AI (Multi-File + Memory)
Runs on port 7861 alongside the Streamlit app (port 7860).

v4 changes:
  - GET  /documents              → list all loaded documents
  - DELETE /documents/{filename} → remove a specific file
  - Upload now supports up to 5 files (additive)
  - Reset clears all files
"""

from fastapi import FastAPI, UploadFile, File, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
from typing import List
import os
import io

app = FastAPI(title="DocMind AI API", version="3.0")

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Shared RAG engine instance
_rag_engine = None

def get_rag():
    global _rag_engine
    if _rag_engine is None:
        from rag_engine import RAGEngine
        _rag_engine = RAGEngine()
    return _rag_engine


# ── Models ───────────────────────────────────────────────────────────────────

class QueryRequest(BaseModel):
    question: str

class DocumentInfo(BaseModel):
    name:        str
    file_type:   str
    chunk_count: int

class QueryResponse(BaseModel):
    answer:       str
    sources:      List[str]
    success:      bool
    error:        str = ""
    memory_count: int = 0

class UploadResponse(BaseModel):
    success:     bool
    filename:    str
    chunks:      int
    file_type:   str
    message:     str
    file_count:  int    # how many files are now loaded
    total_chunks: int   # total chunks across all files

class DocumentsResponse(BaseModel):
    file_count:   int
    max_files:    int
    total_chunks: int
    documents:    List[DocumentInfo]

class MemoryResponse(BaseModel):
    exchanges: int
    messages:  List[dict]


# ── Routes ───────────────────────────────────────────────────────────────────

@app.get("/health")
def health():
    return {"status": "ok", "service": "DocMind AI API", "version": "3.0"}


@app.get("/documents", response_model=DocumentsResponse)
def list_documents():
    """List all currently loaded documents."""
    rag  = get_rag()
    docs = rag.get_documents()
    return DocumentsResponse(
        file_count=len(docs),
        max_files=5,
        total_chunks=rag.get_total_chunks(),
        documents=[
            DocumentInfo(
                name=d["name"],
                file_type=d["type"],
                chunk_count=d["chunk_count"],
            )
            for d in docs
        ],
    )


@app.delete("/documents/{filename}")
def remove_document(filename: str):
    """Remove a specific document by filename."""
    rag     = get_rag()
    removed = rag.remove_file(filename)
    if not removed:
        raise HTTPException(status_code=404, detail=f"Document '{filename}' not found.")
    return {
        "success":      True,
        "message":      f"Removed '{filename}'.",
        "file_count":   rag.get_file_count(),
        "total_chunks": rag.get_total_chunks(),
    }


@app.post("/upload", response_model=UploadResponse)
async def upload_document(file: UploadFile = File(...)):
    """
    Upload and ingest a document (additive — up to 5 files).
    Supported: PDF, TXT, DOCX, CSV, XLSX, JPG, PNG, WEBP
    """
    filename = file.filename
    suffix   = os.path.splitext(filename)[-1].lower()

    SUPPORTED = {".pdf", ".txt", ".docx", ".doc", ".csv", ".xlsx", ".xls",
                 ".jpg", ".jpeg", ".png", ".webp"}
    if suffix not in SUPPORTED:
        raise HTTPException(
            status_code=400,
            detail=f"Unsupported file type: {suffix}. Supported: {', '.join(sorted(SUPPORTED))}"
        )

    try:
        rag     = get_rag()
        content = await file.read()
        buf     = io.BytesIO(content)
        buf.name     = filename
        buf.filename = filename
        chunks  = rag.ingest_file(buf)

        type_labels = {
            ".pdf": "PDF Document",
            ".txt": "Text File",
            ".docx": "Word Document", ".doc": "Word Document",
            ".csv": "CSV Spreadsheet",
            ".xlsx": "Excel Spreadsheet", ".xls": "Excel Spreadsheet",
            ".jpg": "Image", ".jpeg": "Image", ".png": "Image", ".webp": "Image",
        }

        return UploadResponse(
            success=True,
            filename=filename,
            chunks=chunks,
            file_type=type_labels.get(suffix, suffix),
            message=f"Successfully indexed {chunks} chunks from {filename}",
            file_count=rag.get_file_count(),
            total_chunks=rag.get_total_chunks(),
        )
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))


@app.post("/query", response_model=QueryResponse)
async def query_document(req: QueryRequest):
    """Ask a question across all loaded documents. Uses conversation memory."""
    if not req.question.strip():
        raise HTTPException(status_code=400, detail="Question cannot be empty.")
    try:
        rag             = get_rag()
        answer, sources = rag.query(req.question)
        return QueryResponse(
            answer=answer,
            sources=sources,
            success=True,
            memory_count=rag.get_memory_count()
        )
    except Exception as e:
        return QueryResponse(answer="", sources=[], success=False, error=str(e))


@app.get("/memory", response_model=MemoryResponse)
def get_memory():
    """Return current conversation history."""
    rag = get_rag()
    return MemoryResponse(
        exchanges=rag.get_memory_count(),
        messages=rag.get_memory_messages()
    )


@app.post("/memory/clear")
def clear_memory():
    """Clear conversation history without removing documents."""
    rag = get_rag()
    rag.clear_memory()
    return {"success": True, "message": "Conversation memory cleared."}


@app.post("/reset")
def reset():
    """Reset everything — all documents and memory."""
    rag = get_rag()
    rag.reset()
    return {"success": True, "message": "All documents and memory cleared."}