from fastapi import FastAPI, HTTPException, Header, Request
from fastapi.responses import JSONResponse, HTMLResponse
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel
import sqlite3
import sqlparse
import os
import uuid
import json  # Added for json.load()
from typing import Dict, Any
from app.database import create_session_db, close_session_db
from app.schemas import RunQueryRequest, ValidateQueryRequest

app = FastAPI()
app.mount("/static", StaticFiles(directory=os.path.join(os.path.dirname(__file__), "static")), name="static")

@app.exception_handler(Exception)
async def custom_exception_handler(request: Request, exc: Exception):
    return JSONResponse(status_code=500, content={"detail": str(exc)})

sessions: Dict[str, dict] = {}

BASE_DIR = os.path.dirname(__file__)

def load_questions(domain: str):
    file_path = os.path.join(BASE_DIR, "questions", f"{domain}.json")
    if not os.path.exists(file_path):
        raise FileNotFoundError(f"Question file not found: {file_path}")
    with open(file_path, "r") as f:
        return json.load(f)  # Replaced eval with json.load()

def load_schema_sql(domain: str):
    file_path = os.path.join(BASE_DIR, "schemas", f"{domain}.sql")
    if not os.path.exists(file_path):
        raise FileNotFoundError(f"Schema file not found: {file_path}")
    with open(file_path, "r") as f:
        return f.read()

def is_safe_query(sql: str) -> bool:
    parsed = sqlparse.parse(sql.lower())[0]
    return str(parsed).lower().strip().startswith("select") and all(kw not in str(parsed).lower() for kw in ["drop", "attach", "detach", "pragma", "insert", "update", "delete"])

def extract_tables(sql: str) -> list:
    tables = set()
    tokens = sql.replace("\n", " ").lower().split()
    in_subquery = in_openquery = in_values = False

    for i, token in enumerate(tokens):
        if token == "(" and not in_subquery and not in_values:
            in_values = i > 0 and tokens[i - 1] == "values"
            in_subquery = not in_values
        if token == ")" and (in_subquery or in_values):
            if in_values and i + 1 < len(tokens) and tokens[i + 1] == "as": in_values = False
            elif in_subquery: in_subquery = False
        if token == "openquery" and i + 1 < len(tokens) and tokens[i + 1] == "(": in_openquery = True
        if token == ")" and in_openquery: in_openquery = False
        if in_openquery: continue

        if token in ["from", "join", "update", "delete", "insert", "into", "using", "apply", "pivot", "table"]:
            next_token = tokens[i + 1].replace(",);", "") if i + 1 < len(tokens) else ""
            if next_token and next_token not in ["select", "where", "on", "order", "group", "having", "as", "("]:
                if i + 2 < len(tokens) and tokens[i + 2] == "as": next_token = next_token
                elif next_token not in ["left", "right", "inner", "outer", "cross", "full"]: tables.add(next_token)
            i += 1
        elif token == "merge" and i + 1 < len(tokens) and tokens[i + 1] == "into":
            next_token = tokens[i + 2].replace(",);", "") if i + 2 < len(tokens) else ""
            if next_token and next_token not in ["using", "select", "where"]: tables.add(next_token)
            i += 2
            while i + 1 < len(tokens) and tokens[i + 1] != "using": i += 1
            if i + 2 < len(tokens) and (next_token := tokens[i + 2].replace(",);", "")) and next_token not in ["select", "where"]: tables.add(next_token)
        elif token == "select" and i + 1 < len(tokens) and tokens[i + 1] == "into":
            next_token = tokens[i + 2].replace(",);", "") if i + 2 < len(tokens) else ""
            if next_token and next_token not in ["from", "select"]: tables.add(next_token)
            i += 2
            while i + 1 < len(tokens) and tokens[i + 1] != "from": i += 1
            if i + 2 < len(tokens) and (next_token := tokens[i + 2].replace(",);", "")) and next_token not in ["where", "join"]: tables.add(next_token)
        elif token == "with":
            while i + 1 < len(tokens) and tokens[i + 1] != "as": i += 1
            if i + 2 < len(tokens) and tokens[i + 2] == "(":
                bracket_count = 1
                subquery_start = i + 2
                i += 2
                while i < len(tokens) and bracket_count > 0:
                    if tokens[i] == "(": bracket_count += 1
                    elif tokens[i] == ")": bracket_count -= 1
                    i += 1
                if bracket_count == 0 and i > subquery_start:
                    subquery = " ".join(tokens[subquery_start:i - 1])
                    tables.update(t for t in extract_tables(subquery) if t not in tables)
        elif token == "values" and i + 1 < len(tokens) and tokens[i + 1] == "(":
            while i + 1 < len(tokens) and tokens[i + 1] != "as": i += 1
            if i + 2 < len(tokens) and (alias := tokens[i + 2].replace(",);", "")): tables.add(alias)
        elif token in ["exists", "in"]:
            subquery_start = i + 1
            while i + 1 < len(tokens) and tokens[i + 1] != ")": i += 1
            if i > subquery_start:
                subquery = " ".join(tokens[subquery_start:i + 1])
                tables.update(t for t in extract_tables(subquery) if t not in tables)
    return list(tables)

@app.post("/api/session")
async def create_session():
    session_id = str(uuid.uuid4())
    sessions[session_id] = {"conn": create_session_db(), "domain": None}
    return {"session_id": session_id}

@app.get("/api/databases")
async def get_databases():
    questions_dir = os.path.join(BASE_DIR, "questions")
    return {"databases": [f.replace(".json", "") for f in os.listdir(questions_dir) if f.endswith(".json")] if os.path.exists(questions_dir) else []}

@app.post("/api/load-schema/{domain}")
async def load_schema(domain: str, session_id: str = Header(...)):
    if session_id not in sessions: raise HTTPException(status_code=401, detail="Invalid session")
    sessions[session_id] = {"conn": create_session_db(), "domain": domain}
    try:
        sessions[session_id]["conn"].executescript(load_schema_sql(domain))
        sessions[session_id]["conn"].commit()
    except sqlite3.Error as e:
        close_session_db(sessions[session_id]["conn"])  # Cleanup on error
        del sessions[session_id]
        raise HTTPException(status_code=500, detail=f"Database error: {str(e)}")
    return {"message": f"Database {domain} loaded"}

@app.get("/api/schema/{domain}")
async def get_schema(domain: str, session_id: str = Header(...)):
    if session_id not in sessions or sessions[session_id]["domain"] != domain: raise HTTPException(status_code=401, detail="Invalid session or domain not loaded")
    conn = sessions[session_id]["conn"]
    cursor = conn.cursor()
    cursor.execute("SELECT name FROM sqlite_master WHERE type='table';")
    return {"schema": {table: [{"name": row["name"], "type": row["type"]} for row in conn.execute(f"PRAGMA table_info({table});")] for table in [row["name"] for row in cursor.fetchall()]}}

@app.get("/api/sample-data/{domain}")
async def get_sample_data(domain: str, session_id: str = Header(...)):
    if session_id not in sessions or sessions[session_id]["domain"] != domain: raise HTTPException(status_code=401, detail="Invalid session or domain not loaded")
    conn = sessions[session_id]["conn"]
    cursor = conn.cursor()
    cursor.execute("SELECT name FROM sqlite_master WHERE type='table';")
    return {"sample_data": {table: {"columns": [desc[0] for desc in conn.execute(f"SELECT * FROM {table} LIMIT 5").description], "rows": [dict(row) for row in conn.execute(f"SELECT * FROM {table} LIMIT 5")]} for table in [row["name"] for row in cursor.fetchall()]}}

@app.post("/api/run-query")
async def run_query(request: RunQueryRequest, session_id: str = Header(...)):
    if session_id not in sessions or not sessions[session_id]["domain"]: raise HTTPException(status_code=401, detail="Invalid session or no database loaded")
    if not is_safe_query(request.query): raise HTTPException(status_code=400, detail="Only SELECT queries are allowed")
    conn = sessions[session_id]["conn"]
    cursor = conn.cursor()
    cursor.execute(request.query)
    if cursor.description:
        columns = [desc[0] for desc in cursor.description]
        return {"columns": columns, "rows": [dict(zip(columns, row)) for row in cursor.fetchall()]}
    return {"message": "Query executed successfully (no results)"}

@app.get("/api/questions/{domain}")
async def get_questions(domain: str, difficulty: str = None):
    questions = load_questions(domain)
    if difficulty: questions = [q for q in questions if q["difficulty"].lower() == difficulty.lower()]
    return [{"id": q["id"], "title": q["title"], "difficulty": q["difficulty"], "description": q["description"], "hint": q["hint"], "expected_sql": q["expected_sql"]} for q in questions]

@app.post("/api/validate")
async def validate_query(request: ValidateQueryRequest, session_id: str = Header(...)):
    if session_id not in sessions or not sessions[session_id]["domain"]: raise HTTPException(status_code=401, detail="Invalid session or no database loaded")
    conn = sessions[session_id]["conn"]
    cursor = conn.cursor()
    cursor.execute(request.user_query)
    user_result = [tuple(str(x).lower() for x in row) for row in cursor.fetchall()] if cursor.description else []
    cursor.execute(request.expected_query)
    expected_result = [tuple(str(x).lower() for x in row) for row in cursor.fetchall()] if cursor.description else []
    return {"valid": user_result == expected_result, "error": "Results do not match." if user_result != expected_result else ""}

@app.on_event("shutdown")
async def cleanup():
    for session_id in list(sessions): close_session_db(sessions[session_id]["conn"]); del sessions[session_id]

@app.get("/", response_class=HTMLResponse)
async def serve_frontend():
    file_path = os.path.join(BASE_DIR, "static", "index.html")
    if not os.path.exists(file_path): raise HTTPException(status_code=500, detail=f"Frontend file not found: {file_path}")
    with open(file_path, "r") as f: return f.read()