"""
Database migration logic for importing CSV data.
Used by both CLI script and automatic startup migration.
"""

import re
from pathlib import Path
from typing import Dict, Optional

import numpy as np
import pandas as pd
import requests

from .config import settings
from .database import Base, engine, get_db_session
from .models import School, SchoolResult
from .schemas import (
    COLUMN_MAPPINGS,
    LA_CODE_TO_NAME,
    NULL_VALUES,
    SCHOOL_TYPE_MAP,
)


def parse_numeric(value) -> Optional[float]:
    """Parse a numeric value, handling special cases."""
    if pd.isna(value):
        return None
    if isinstance(value, (int, float)):
        return float(value) if not np.isnan(value) else None
    str_val = str(value).strip().upper()
    if str_val in NULL_VALUES or str_val == "":
        return None
    # Remove percentage signs if present
    str_val = str_val.replace("%", "")
    try:
        return float(str_val)
    except ValueError:
        return None


def extract_year_from_folder(folder_name: str) -> Optional[int]:
    """Extract year from folder name like '2023-2024'."""
    match = re.search(r"(\d{4})-(\d{4})", folder_name)
    if match:
        return int(match.group(2))
    match = re.search(r"(\d{4})", folder_name)
    if match:
        return int(match.group(1))
    return None


def geocode_postcodes_bulk(postcodes: list) -> Dict[str, tuple]:
    """
    Geocode postcodes in bulk using postcodes.io API.
    Returns dict of postcode -> (latitude, longitude).
    """
    results = {}
    valid_postcodes = [
        p.strip().upper()
        for p in postcodes
        if p and isinstance(p, str) and len(p.strip()) >= 5
    ]
    valid_postcodes = list(set(valid_postcodes))

    if not valid_postcodes:
        return results

    batch_size = 100
    total_batches = (len(valid_postcodes) + batch_size - 1) // batch_size

    for i, batch_start in enumerate(range(0, len(valid_postcodes), batch_size)):
        batch = valid_postcodes[batch_start : batch_start + batch_size]
        print(
            f"    Geocoding batch {i + 1}/{total_batches} ({len(batch)} postcodes)..."
        )

        try:
            response = requests.post(
                "https://api.postcodes.io/postcodes",
                json={"postcodes": batch},
                timeout=30,
            )
            if response.status_code == 200:
                data = response.json()
                for item in data.get("result", []):
                    if item and item.get("result"):
                        pc = item["query"].upper()
                        lat = item["result"].get("latitude")
                        lon = item["result"].get("longitude")
                        if lat and lon:
                            results[pc] = (lat, lon)
        except Exception as e:
            print(f"    Warning: Geocoding batch failed: {e}")

    return results


def load_csv_data(data_dir: Path) -> pd.DataFrame:
    """Load all CSV data from data directory."""
    all_data = []

    for folder in sorted(data_dir.iterdir()):
        if not folder.is_dir():
            continue

        year = extract_year_from_folder(folder.name)
        if not year:
            continue

        # Specifically look for the KS2 results file
        ks2_file = folder / "england_ks2final.csv"
        if not ks2_file.exists():
            continue

        csv_file = ks2_file
        print(f"  Loading {csv_file.name} (year {year})...")

        try:
            df = pd.read_csv(csv_file, encoding="latin-1", low_memory=False)
        except Exception as e:
            print(f"    Error loading {csv_file}: {e}")
            continue

        # Rename columns
        df.rename(columns=COLUMN_MAPPINGS, inplace=True)
        df["year"] = year

        # Handle local authority name
        la_name_cols = ["LANAME", "LA (name)", "LA_NAME", "LA NAME"]
        la_name_col = next((c for c in la_name_cols if c in df.columns), None)

        if la_name_col and la_name_col != "local_authority":
            df["local_authority"] = df[la_name_col]
        elif "LEA" in df.columns:
            df["local_authority_code"] = pd.to_numeric(df["LEA"], errors="coerce")
            df["local_authority"] = (
                df["local_authority_code"]
                .map(LA_CODE_TO_NAME)
                .fillna(df["LEA"].astype(str))
            )

        # Store LEA code
        if "LEA" in df.columns:
            df["local_authority_code"] = pd.to_numeric(df["LEA"], errors="coerce")

        # Map school type
        if "school_type_code" in df.columns:
            df["school_type"] = (
                df["school_type_code"]
                .map(SCHOOL_TYPE_MAP)
                .fillna(df["school_type_code"])
            )

        # Create combined address
        addr_parts = ["address1", "address2", "town", "postcode"]
        for col in addr_parts:
            if col not in df.columns:
                df[col] = None

        df["address"] = df.apply(
            lambda r: ", ".join(
                str(v)
                for v in [
                    r.get("address1"),
                    r.get("address2"),
                    r.get("town"),
                    r.get("postcode"),
                ]
                if pd.notna(v) and str(v).strip()
            ),
            axis=1,
        )

        all_data.append(df)
        print(f"    Loaded {len(df)} records")

    if all_data:
        result = pd.concat(all_data, ignore_index=True)
        print(f"\nTotal records loaded: {len(result)}")
        print(f"Unique schools: {result['urn'].nunique()}")
        print(f"Years: {sorted(result['year'].unique())}")
        return result

    return pd.DataFrame()


def migrate_data(df: pd.DataFrame, geocode: bool = False):
    """Migrate DataFrame data to database."""

    # Clean URN column - convert to integer, drop invalid values
    df = df.copy()
    df["urn"] = pd.to_numeric(df["urn"], errors="coerce")
    df = df.dropna(subset=["urn"])
    df["urn"] = df["urn"].astype(int)

    # Group by URN to get unique schools (use latest year's data)
    school_data = (
        df.sort_values("year", ascending=False).groupby("urn").first().reset_index()
    )
    print(f"\nMigrating {len(school_data)} unique schools...")

    # Geocode if requested
    geocoded = {}
    if geocode and "postcode" in df.columns:
        print("\nGeocoding postcodes...")
        postcodes = df["postcode"].dropna().unique().tolist()
        geocoded = geocode_postcodes_bulk(postcodes)
        print(f"  Successfully geocoded {len(geocoded)} postcodes")

    with get_db_session() as db:
        # Create schools
        urn_to_school_id = {}
        schools_created = 0

        for _, row in school_data.iterrows():
            # Safely parse URN - handle None, NaN, whitespace, and invalid values
            urn_val = row.get("urn")
            urn = None
            if pd.notna(urn_val):
                try:
                    urn_str = str(urn_val).strip()
                    if urn_str:
                        urn = int(float(urn_str))  # Handle "12345.0" format
                except (ValueError, TypeError):
                    pass
            if not urn:
                continue

            # Skip if we've already added this URN (handles duplicates in source data)
            if urn in urn_to_school_id:
                continue

            # Get geocoding data
            postcode = row.get("postcode")
            lat, lon = None, None
            if postcode and pd.notna(postcode):
                coords = geocoded.get(str(postcode).strip().upper())
                if coords:
                    lat, lon = coords

            # Safely parse local_authority_code
            la_code = None
            la_code_val = row.get("local_authority_code")
            if pd.notna(la_code_val):
                try:
                    la_code_str = str(la_code_val).strip()
                    if la_code_str:
                        la_code = int(float(la_code_str))
                except (ValueError, TypeError):
                    pass

            school = School(
                urn=urn,
                school_name=row.get("school_name")
                if pd.notna(row.get("school_name"))
                else "Unknown",
                local_authority=row.get("local_authority")
                if pd.notna(row.get("local_authority"))
                else None,
                local_authority_code=la_code,
                school_type=row.get("school_type")
                if pd.notna(row.get("school_type"))
                else None,
                school_type_code=row.get("school_type_code")
                if pd.notna(row.get("school_type_code"))
                else None,
                religious_denomination=row.get("religious_denomination")
                if pd.notna(row.get("religious_denomination"))
                else None,
                age_range=row.get("age_range")
                if pd.notna(row.get("age_range"))
                else None,
                address1=row.get("address1") if pd.notna(row.get("address1")) else None,
                address2=row.get("address2") if pd.notna(row.get("address2")) else None,
                town=row.get("town") if pd.notna(row.get("town")) else None,
                postcode=row.get("postcode") if pd.notna(row.get("postcode")) else None,
                latitude=lat,
                longitude=lon,
            )
            db.add(school)
            db.flush()  # Get the ID
            urn_to_school_id[urn] = school.id
            schools_created += 1

            if schools_created % 1000 == 0:
                print(f"  Created {schools_created} schools...")

        print(f"  Created {schools_created} schools")

        # Create results
        print(f"\nMigrating {len(df)} yearly results...")
        results_created = 0

        for _, row in df.iterrows():
            # Safely parse URN
            urn_val = row.get("urn")
            urn = None
            if pd.notna(urn_val):
                try:
                    urn_str = str(urn_val).strip()
                    if urn_str:
                        urn = int(float(urn_str))
                except (ValueError, TypeError):
                    pass
            if not urn or urn not in urn_to_school_id:
                continue

            school_id = urn_to_school_id[urn]

            # Safely parse year
            year_val = row.get("year")
            year = None
            if pd.notna(year_val):
                try:
                    year = int(float(str(year_val).strip()))
                except (ValueError, TypeError):
                    pass
            if not year:
                continue

            result = SchoolResult(
                school_id=school_id,
                year=year,
                total_pupils=parse_numeric(row.get("total_pupils")),
                eligible_pupils=parse_numeric(row.get("eligible_pupils")),
                # Expected Standard
                rwm_expected_pct=parse_numeric(row.get("rwm_expected_pct")),
                reading_expected_pct=parse_numeric(row.get("reading_expected_pct")),
                writing_expected_pct=parse_numeric(row.get("writing_expected_pct")),
                maths_expected_pct=parse_numeric(row.get("maths_expected_pct")),
                gps_expected_pct=parse_numeric(row.get("gps_expected_pct")),
                science_expected_pct=parse_numeric(row.get("science_expected_pct")),
                # Higher Standard
                rwm_high_pct=parse_numeric(row.get("rwm_high_pct")),
                reading_high_pct=parse_numeric(row.get("reading_high_pct")),
                writing_high_pct=parse_numeric(row.get("writing_high_pct")),
                maths_high_pct=parse_numeric(row.get("maths_high_pct")),
                gps_high_pct=parse_numeric(row.get("gps_high_pct")),
                # Progress
                reading_progress=parse_numeric(row.get("reading_progress")),
                writing_progress=parse_numeric(row.get("writing_progress")),
                maths_progress=parse_numeric(row.get("maths_progress")),
                # Averages
                reading_avg_score=parse_numeric(row.get("reading_avg_score")),
                maths_avg_score=parse_numeric(row.get("maths_avg_score")),
                gps_avg_score=parse_numeric(row.get("gps_avg_score")),
                # Context
                disadvantaged_pct=parse_numeric(row.get("disadvantaged_pct")),
                eal_pct=parse_numeric(row.get("eal_pct")),
                sen_support_pct=parse_numeric(row.get("sen_support_pct")),
                sen_ehcp_pct=parse_numeric(row.get("sen_ehcp_pct")),
                stability_pct=parse_numeric(row.get("stability_pct")),
                # Absence
                reading_absence_pct=parse_numeric(row.get("reading_absence_pct")),
                gps_absence_pct=parse_numeric(row.get("gps_absence_pct")),
                maths_absence_pct=parse_numeric(row.get("maths_absence_pct")),
                writing_absence_pct=parse_numeric(row.get("writing_absence_pct")),
                science_absence_pct=parse_numeric(row.get("science_absence_pct")),
                # Gender
                rwm_expected_boys_pct=parse_numeric(row.get("rwm_expected_boys_pct")),
                rwm_expected_girls_pct=parse_numeric(row.get("rwm_expected_girls_pct")),
                rwm_high_boys_pct=parse_numeric(row.get("rwm_high_boys_pct")),
                rwm_high_girls_pct=parse_numeric(row.get("rwm_high_girls_pct")),
                # Disadvantaged
                rwm_expected_disadvantaged_pct=parse_numeric(
                    row.get("rwm_expected_disadvantaged_pct")
                ),
                rwm_expected_non_disadvantaged_pct=parse_numeric(
                    row.get("rwm_expected_non_disadvantaged_pct")
                ),
                disadvantaged_gap=parse_numeric(row.get("disadvantaged_gap")),
                # 3-Year
                rwm_expected_3yr_pct=parse_numeric(row.get("rwm_expected_3yr_pct")),
                reading_avg_3yr=parse_numeric(row.get("reading_avg_3yr")),
                maths_avg_3yr=parse_numeric(row.get("maths_avg_3yr")),
            )
            db.add(result)
            results_created += 1

            if results_created % 10000 == 0:
                print(f"  Created {results_created} results...")
                db.flush()

        print(f"  Created {results_created} results")

        # Commit all changes
        db.commit()
        print("\nMigration complete!")


def run_full_migration(geocode: bool = False) -> bool:
    """
    Run a complete migration: drop all tables and reimport from CSV.

    Returns True if successful, False if no data found.
    Raises exception on error.
    """
    print("Dropping existing tables...")
    Base.metadata.drop_all(bind=engine)

    print("Creating tables...")
    Base.metadata.create_all(bind=engine)

    print("\nLoading CSV data...")
    df = load_csv_data(settings.data_dir)

    if df.empty:
        print("Warning: No CSV data found to migrate!")
        return False

    migrate_data(df, geocode=geocode)
    return True