import os
import re
import sqlite3
from openai import OpenAI
from difflib import get_close_matches

# =========================
# SETUP
# =========================

# Validate API key
api_key = os.getenv("OPENAI_API_KEY")
if not api_key:
    raise ValueError("OPENAI_API_KEY environment variable is not set")
client = OpenAI(api_key=api_key)
conn = sqlite3.connect("mimic_iv_demo.db", check_same_thread=False)


# =========================
# CONVERSATION STATE
# =========================

LAST_PROMPT_TYPE = None
LAST_SUGGESTED_DATE = None



# =========================
# HUMAN RESPONSE HELPERS
# =========================

def humanize(text):
    return f"Sure \n\n{text}"

def friendly(text):
    global LAST_SUGGESTED_DATE
    if LAST_SUGGESTED_DATE:
        return f"{text}\n\nLast data available is {LAST_SUGGESTED_DATE}"
    else:
        # If date not set yet, try to get it
        date = get_latest_data_date()
        if date:
            return f"{text}\n\nLast data available is {date}"
        return text

def is_confirmation(text):
    return text.strip().lower() in ["yes", "yep", "yeah", "ok", "okay", "sure"]

def is_why_question(text):
    return text.strip().lower().startswith("why")

# =========================
# SPELL CORRECTION
# =========================

KNOWN_TERMS = [
    "patient", "patients", "condition", "conditions",
    "encounter", "encounters", "visit", "visits",
    "medication", "medications",
    "admitted", "admission",
    "year", "month", "last", "recent", "today"
]

def correct_spelling(q):
    words = q.split()
    fixed = []
    for w in words:
        clean = w.lower().strip(",.?")
        match = get_close_matches(clean, KNOWN_TERMS, n=1, cutoff=0.8)
        fixed.append(match[0] if match else w)
    return " ".join(fixed)



# =========================
# SCHEMA
# =========================
import json
from functools import lru_cache

@lru_cache(maxsize=1)
def load_ai_schema():
    """Load schema from metadata JSON file with error handling."""
    try:
        with open("hospital_metadata.json", "r") as f:
            schema = json.load(f)
            if not isinstance(schema, dict):
                raise ValueError("Invalid metadata format: expected a dictionary")
            return schema
    except FileNotFoundError:
        raise FileNotFoundError("hospital_metadata.json file not found. Please create it with your table metadata.")
    except json.JSONDecodeError as e:
        raise ValueError(f"Invalid JSON in hospital_metadata.json: {str(e)}")
    except Exception as e:
        raise ValueError(f"Error loading metadata: {str(e)}")

# =========================
# TABLE MATCHING (CORE LOGIC)
# =========================

def extract_relevant_tables(question, max_tables=4):
    schema = load_ai_schema()
    q = question.lower()
    tokens = set(q.replace("?", "").replace(",", "").split())

    matched = []

    # Lightweight intent hints - dynamically filter to only include tables that exist
    # Map natural language terms to potential table names (check against schema)
    all_tables = list(schema.keys())
    table_names_lower = [t.lower() for t in all_tables]
    
    DOMAIN_HINTS = {}
    
    # Build hints only for tables that actually exist
    hint_mappings = {
        "consultant": ["encounter", "encounters", "visit", "visits"],
        "doctor": ["encounter", "encounters", "provider", "providers"],
        "visit": ["encounter", "encounters", "visit", "visits"],
        "visited": ["encounter", "encounters", "visit", "visits"],
        "visits": ["encounter", "encounters", "visit", "visits"],
        "appointment": ["encounter", "encounters", "appointment", "appointments"],
        "patient": ["patient", "patients"],
        "medication": ["medication", "medications", "drug", "drugs"],
        "drug": ["medication", "medications", "drug", "drugs"],
        "condition": ["condition", "conditions", "diagnosis", "diagnoses"],
        "diagnosis": ["condition", "conditions", "diagnosis", "diagnoses"]
    }
    
    # Only include hints for tables that exist in the schema
    for intent, possible_tables in hint_mappings.items():
        matching_tables = [t for t in possible_tables if t in table_names_lower]
        if matching_tables:
            DOMAIN_HINTS[intent] = matching_tables

    # Early exit threshold - if we find a perfect match, we can stop early
    VERY_HIGH_SCORE = 10

    for table, meta in schema.items():
        score = 0
        table_l = table.lower()

        # 1️⃣ Strong signal: table name (exact match is very high confidence)
        if table_l in q:
            score += 6
            # Early exit optimization: if exact table match found, prioritize it
            if score >= VERY_HIGH_SCORE:
                matched.append((table, score))
                continue

        # 2️⃣ Column relevance
        for col, desc in meta["columns"].items():
            col_l = col.lower()
            if col_l in q:
                score += 3
            elif any(tok in col_l for tok in tokens):
                score += 1

        # 3️⃣ Description relevance (less weight to avoid false positives)
        if meta.get("description"):
            desc_tokens = set(meta["description"].lower().split())
            # Only count meaningful word matches, not common words
            common_words = {"the", "is", "at", "which", "on", "for", "a", "an"}
            meaningful_matches = tokens & desc_tokens - common_words
            if meaningful_matches:
                score += len(meaningful_matches) * 0.5  # Reduced weight

        # 4️⃣ Semantic intent mapping (important - highest priority)
        for intent, tables in DOMAIN_HINTS.items():
            if intent in q and table_l in tables:
                score += 5

        # 5️⃣ Only add if meets minimum threshold (prevents low-quality matches)
        # Use lower threshold for small schemas (more lenient)
        # Increased threshold from 3 to 4 for better precision, but lower to 2 for small schemas
        threshold = 2 if len(schema) <= 5 else 4
        if score >= threshold:
            matched.append((table, score))

    # Sort by relevance
    matched.sort(key=lambda x: x[1], reverse=True)

    # If no matches but schema is very small, return all tables (with lower confidence)
    if not matched and len(schema) <= 3:
        return list(schema.keys())[:max_tables]

    return [t[0] for t in matched[:max_tables]]


# =========================
# HUMAN SCHEMA DESCRIPTION
# =========================

def describe_schema(max_tables=10):
    schema = load_ai_schema()
    total_tables = len(schema)

    response = f"Here's the data I currently have access to ({total_tables} tables):\n\n"

    # Show only top N tables to avoid overwhelming output
    shown_tables = list(schema.items())[:max_tables]
    
    for table, meta in shown_tables:
        response += f"• **{table.capitalize()}** — {meta['description']}\n"
        # Show only first 5 columns per table
        for col, desc in list(meta["columns"].items())[:5]:
            response += f"  - {col}: {desc}\n"
        if len(meta["columns"]) > 5:
            response += f"  ... and {len(meta['columns']) - 5} more columns\n"
        response += "\n"

    if total_tables > max_tables:
        response += f"\n... and {total_tables - max_tables} more tables.\n"
        response += "Ask about a specific table to see its details.\n\n"

    response += (
        "You can ask things like:\n"
        "• How many patients are there?\n"
        "• Patient count by gender\n"
        "• Admissions by year\n\n"
        "Just tell me what you want to explore "
    )

    return response

# =========================
# TIME HANDLING
# =========================

def get_latest_data_date():
    """Get the latest data date by checking tables with date columns."""
    schema = load_ai_schema()
    
    # Common date column names to check
    date_columns = ["date", "start_date", "end_date", "admission_date", "admittime", "dischtime", "created_at", "updated_at"]
    
    # Try to find a table with a date column
    for table_name in schema.keys():
        columns = schema[table_name].get("columns", {})
        
        # Check if table has any date-like column
        for col_name in columns.keys():
            col_lower = col_name.lower()
            if any(date_col in col_lower for date_col in date_columns):
                try:
                    result = conn.execute(
                        f"SELECT MAX({col_name}) FROM {table_name}"
                    ).fetchone()
                    if result and result[0]:
                        return result[0]
                except (sqlite3.Error, sqlite3.OperationalError):
                    continue  # Try next table/column
    
    return None


def normalize_time_question(q):
    latest = get_latest_data_date()
    if not latest:
        return q

    if "today" in q:
        return q.replace("today", f"on {latest[:10]}")

    if "yesterday" in q:
        return q.replace("yesterday", f"on {latest[:10]}")

    return q

# =========================
# UNSUPPORTED QUESTIONS
# =========================

def is_question_supported(question):
    q = question.lower()
    tokens = set(q.replace("?", "").replace(",", "").split())

    # 1️⃣ Allow analytical intent even without table names
    analytic_keywords = {
        "count", "total", "average", "avg", "sum",
        "how many", "number of", "trend",
        "increase", "decrease", "compare", "more than", "less than"
    }

    if any(k in q for k in analytic_keywords):
        return True

    # 2️⃣ Check schema relevance (table-by-table)
    schema = load_ai_schema()

    for table, meta in schema.items():
        score = 0
        table_l = table.lower()

        # Table name match
        if table_l in q:
            score += 3

        # Column name match
        for col, desc in meta["columns"].items():
            col_l = col.lower()
            if col_l in q:
                score += 2
            elif any(tok in col_l for tok in tokens):
                score += 1

        # Description match
        if meta.get("description"):
            desc_tokens = set(meta["description"].lower().split())
            score += len(tokens & desc_tokens)

        # ✅ If any table is relevant enough → supported
        if score >= 2:
            return True

    return False



# =========================
# SQL GENERATION
# =========================

def build_prompt(question):
    matched = extract_relevant_tables(question)
    full_schema = load_ai_schema()

    if matched:
        schema = {t: full_schema[t] for t in matched}
    else:
        # 🚫 Don't send all 100+ tables! Return a helpful error with available tables
        available_tables = list(full_schema.keys())[:10]  # Show first 10 tables
        tables_list = "\n".join(f"- {t}" for t in available_tables)
        if len(full_schema) > 10:
            tables_list += f"\n... and {len(full_schema) - 10} more tables"
        raise ValueError(
            f"I couldn't find any relevant tables for your question.\n\n"
            f"Available tables:\n{tables_list}\n\n"
            f"Please try mentioning a specific table name or use 'what data' to see all available tables."
        )

    prompt = """
You are a hospital SQL assistant.

Rules:
- Use only SELECT
- SQLite syntax
- Use ONLY the exact table names listed below (do not create or infer table names)
- Use only listed tables/columns
- Return ONLY SQL or NOT_ANSWERABLE

IMPORTANT: Use EXACTLY the table names provided in the list below. Do not pluralize, modify, or guess table names.
"""

    for table, meta in schema.items():
        prompt += f"\nTable: {table}\n"
        for col, desc in meta["columns"].items():
            prompt += f"- {col}: {desc}\n"

    prompt += f"\nQuestion: {question}\n"
    prompt += "\nRemember: Use EXACT table names from the list above. Do not pluralize or modify table names."
    return prompt


def call_llm(prompt):
    """Call OpenAI API with error handling."""
    try:
        res = client.chat.completions.create(
            model="gpt-4.1-mini",
            messages=[
                {"role": "system", "content": "Return only SQL or NOT_ANSWERABLE"},
                {"role": "user", "content": prompt}
            ],
            temperature=0
        )
        if not res.choices or not res.choices[0].message.content:
            raise ValueError("Empty response from OpenAI API")
        return res.choices[0].message.content.strip()
    except Exception as e:
        raise ValueError(f"OpenAI API error: {str(e)}")

# =========================
# SQL SAFETY
# =========================

def sanitize_sql(sql):
    # Remove code fence markers but preserve legitimate SQL
    sql = sql.replace("```sql", "").replace("```", "").strip()
    # Remove leading/trailing markdown code markers
    if sql.startswith("sql"):
        sql = sql[3:].strip()
    sql = sql.split(";")[0]
    return sql.replace("\n", " ").strip()

def correct_table_names(sql):
    """Fix common table name mistakes in generated SQL."""
    schema = load_ai_schema()
    valid_tables = set(schema.keys())
    
    sql_lower = sql.lower()
    sql_corrected = sql
    
    # Common table name mappings (case-insensitive replacement)
    table_corrections = {
        "visits": "encounters",
        "visit": "encounters",
        "providers": "encounters",  # if this table doesn't exist
    }
    
    # Check each correction
    for wrong_name, correct_name in table_corrections.items():
        # Only correct if the wrong table doesn't exist AND correct one does
        if wrong_name.lower() not in valid_tables and correct_name.lower() in valid_tables:
            # Use word boundaries to avoid partial replacements
            pattern = r'\b' + re.escape(wrong_name) + r'\b'
            sql_corrected = re.sub(pattern, correct_name, sql_corrected, flags=re.IGNORECASE)
    
    return sql_corrected

def validate_sql(sql):
    if not sql.lower().startswith("select"):
        raise ValueError("Only SELECT allowed")
    return sql

def run_query(sql):
    """Execute SQL query with proper error handling."""
    cur = conn.cursor()
    try:
        rows = cur.execute(sql).fetchall()
        if cur.description:
            cols = [c[0] for c in cur.description]
        else:
            cols = []
        return cols, rows
    except sqlite3.Error as e:
        raise ValueError(f"Database query error: {str(e)}")

# =========================
# AGGREGATE SAFETY
# =========================

def is_aggregate_only_query(sql):
    s = sql.lower()
    return ("count(" in s or "sum(" in s or "avg(" in s) and "group by" not in s

def has_underlying_data(sql):
    """Check if underlying data exists for the SQL query."""
    base = sql.lower()
    if "from" not in base:
        return False

    base = base.split("from", 1)[1]
    # Split at GROUP BY, ORDER BY, LIMIT, etc. to get just the FROM clause
    for clause in ["group by", "order by", "limit", "having"]:
        base = base.split(clause)[0]
    
    test_sql = "SELECT 1 FROM " + base.strip() + " LIMIT 1"

    cur = conn.cursor()
    try:
        return cur.execute(test_sql).fetchone() is not None
    except sqlite3.Error:
        return False

# =========================
# PATIENT SUMMARY
# =========================

def validate_identifier(name):
    """Validate that identifier is safe (only alphanumeric and underscores)."""
    if not name or not isinstance(name, str):
        return False
    # Check for SQL injection attempts
    forbidden = [";", "--", "/*", "*/", "'", '"', "`", "(", ")", " ", "\n", "\t"]
    if any(char in name for char in forbidden):
        return False
    # Must start with letter or underscore, rest alphanumeric/underscore
    return bool(re.match(r'^[a-zA-Z_][a-zA-Z0-9_]*$', name))

def build_table_summary(table_name):
    """Build summary for a table using metadata."""
    # Validate table name against metadata first
    schema = load_ai_schema()
    if table_name not in schema:
        return f"Table {table_name} not found in metadata."
    
    # Additional safety check
    if not validate_identifier(table_name):
        return f"Invalid table name: {table_name}"

    cur = conn.cursor()
    
    # Total rows (still need to query actual data for count)
    # Note: SQLite doesn't support parameterized table names
    # Since we validated table_name against metadata, it's safe
    try:
        total = cur.execute(
            f"SELECT COUNT(*) FROM {table_name}"
        ).fetchone()[0]
    except sqlite3.Error as e:
        return f"Error querying table {table_name}: {str(e)}"

    columns = schema[table_name]["columns"]  # {col_name: description, ...}

    summary = f"Here's a summary of **{table_name}**:\n\n"
    summary += f"• Total records: {total}\n"

    # Try to summarize categorical columns using metadata
    for col_name, col_desc in columns.items():
        # Validate column name
        if not validate_identifier(col_name):
            continue
            
        # Try to determine if it's a categorical column based on name/description
        # Skip likely numeric/date columns
        col_lower = col_name.lower()
        if any(skip in col_lower for skip in ["id", "_id", "date", "time", "count", "amount", "price"]):
            continue
            
        # Try to get breakdown for text-like columns
        try:
            # Note: SQLite doesn't support parameterized identifiers, so we validate
            rows = cur.execute(
                f"""
                SELECT {col_name}, COUNT(*)
                FROM {table_name}
                GROUP BY {col_name}
                ORDER BY COUNT(*) DESC
                LIMIT 5
                """
            ).fetchall()

            if rows:
                summary += f"\n• {col_name.capitalize()} breakdown:\n"
                for val, count in rows:
                    summary += f"  - {val}: {count}\n"
        except (sqlite3.Error, sqlite3.OperationalError) as e:
            # Ignore columns that can't be grouped (likely not categorical)
            pass

    summary += "\nYou can ask more detailed questions about this data."

    return summary



# =========================
# MAIN ENGINE
# =========================

def process_question(question):
    global LAST_PROMPT_TYPE, LAST_SUGGESTED_DATE

    q = question.strip().lower()

    # ----------------------------------
    # Normalize first
    # ----------------------------------
    question = correct_spelling(question)
    question = normalize_time_question(question)
    
    LAST_PROMPT_TYPE = None
    LAST_SUGGESTED_DATE = None


    # ----------------------------------
    # Handle "data updated till"
    # ----------------------------------
    if any(x in q for x in ["updated", "upto", "up to", "latest data"]):
        return {
            "status": "ok",
            "message": f"Data is available up to {get_latest_data_date()}",
            "data": []
        }

    # ----------------------------------
    # Extract relevant tables
    # ----------------------------------
    matched_tables = extract_relevant_tables(question)

    # ----------------------------------
    # SUMMARY ONLY IF USER ASKS FOR IT
    # ----------------------------------
    if (
    len(matched_tables) == 1
    and any(k in q for k in ["summary", "overview", "describe"])
    and not any(k in q for k in ["count", "total", "how many", "average"])
):

        return {
        "status": "ok",
        "message": build_table_summary(matched_tables[0]),
        "data": []
    }
    
    # Only block if too many tables matched AND it's not an analytical question
    # Analytical questions (how many, count, etc.) often need multiple tables
    is_analytical = any(k in q for k in [
        "how many", "count", "total", "number of", 
        "average", "avg", "sum", "more than", "less than",
        "compare", "trend"
    ])
    
    if len(matched_tables) > 4 and not is_analytical:
        return {
        "status": "ok",
        "message": (
            "Your question matches too many datasets:\n"
            + "\n".join(f"- {t}" for t in matched_tables[:5])
            + "\n\nPlease be more specific about what you want to know."
        ),
        "data": []
    }


    # ----------------------------------
    # Metadata discovery
    # ----------------------------------
    if any(x in q for x in ["what data", "what tables", "which data"]):
        return {
            "status": "ok",
            "message": humanize(describe_schema()),
            "data": []
        }

    # ----------------------------------
    # Unsupported question check
    # ----------------------------------
    if not is_question_supported(question):
        return {
            "status": "ok",
            "message": (
                "That information isn’t available in the system.\n\n"
                "You can ask about:\n"
                "• Patients\n"
                "• Visits\n"
                "• Conditions\n"
                "• Medications"
            ),
            "data": []
        }

    # ----------------------------------
    # Generate SQL
    # ----------------------------------
    try:
        sql = call_llm(build_prompt(question))
    except ValueError as e:
        # Handle case where no relevant tables found
        return {
            "status": "ok",
            "message": str(e),
            "data": []
        }

    if sql == "NOT_ANSWERABLE":
        return {
            "status": "ok",
            "message": "I don't have enough data to answer that.",
            "data": []
        }

    # Sanitize, correct table names, then validate
    sql = sanitize_sql(sql)
    sql = correct_table_names(sql)
    sql = validate_sql(sql)
    cols, rows = run_query(sql)

    # ----------------------------------
    # No data handling
    # ----------------------------------
    if is_aggregate_only_query(sql) and not has_underlying_data(sql):
        LAST_PROMPT_TYPE = "NO_DATA"
        LAST_SUGGESTED_DATE = get_latest_data_date()

        return {
            "status": "ok",
            "message": friendly("No data is available for that time period."),
            "note": f"Available data is only up to {LAST_SUGGESTED_DATE}.",
            "data": []
        }

    if not rows:
        LAST_PROMPT_TYPE = "NO_DATA"
        LAST_SUGGESTED_DATE = get_latest_data_date()

        return {
            "status": "ok",
            "message": friendly("No records found."),
            "note": f"Available data is only up to {LAST_SUGGESTED_DATE}.",
            "data": []
        }

    # ----------------------------------
    # Success
    # ----------------------------------
    return {
        "status": "ok",
        "sql": sql,
        "columns": cols,
        "data": rows
    }