"""
core/importer.py
----------------
CSV draw importer for LottoSight.

Supported formats (auto-detected):
  1. LottoSight export  — Game, Date, "N1,N2,...", Bonus, Multiplier, Source
  2. Wide format        — Date, N1, N2, ..., Nn [, Bonus]
  3. Packed format      — Date, "N1,N2,...", [Bonus]

Header rows are auto-detected and skipped.
Dates accepted: YYYY-MM-DD, MM/DD/YYYY, M/D/YYYY, MM-DD-YYYY.
Duplicate draws (same game + date already in DB) are skipped, not errored.
"""

import csv
from datetime import datetime

from db.models import get_game_by_id, insert_draw


# ── Date parsing ──────────────────────────────────────────────────────────────

_DATE_FORMATS = ("%Y-%m-%d", "%m/%d/%Y", "%m-%d-%Y", "%d/%m/%Y", "%-m/%-d/%Y")


def _parse_date(text: str) -> str | None:
    """Return ISO date string (YYYY-MM-DD) or None."""
    text = text.strip()
    for fmt in _DATE_FORMATS:
        try:
            return datetime.strptime(text, fmt).strftime("%Y-%m-%d")
        except ValueError:
            pass
    return None


def _is_header(row: list[str]) -> bool:
    """Heuristic: first cell is not a recognisable date → row is a header."""
    return bool(row) and _parse_date(row[0]) is None


# ── Row parsing ───────────────────────────────────────────────────────────────

def _parse_row_lottosight(cells: list[str]) -> dict | None:
    """Parse LottoSight export row: Game, Date, Numbers, Bonus, ..."""
    if len(cells) < 3:
        return None
    date_str = _parse_date(cells[1])
    if date_str is None:
        return None
    try:
        numbers = [int(n.strip()) for n in cells[2].split(",") if n.strip()]
        bonus   = int(cells[3]) if len(cells) > 3 and cells[3].strip().isdigit() else None
    except (ValueError, IndexError):
        return None
    return {"date": date_str, "numbers": numbers, "bonus": bonus}


def _parse_row_generic(cells: list[str], game: dict) -> dict | None:
    """Parse wide or packed format: Date, [nums...]"""
    date_str = _parse_date(cells[0])
    if date_str is None:
        return None

    rest = cells[1:]
    if not rest:
        return None

    # Packed: second cell contains comma-separated numbers
    if "," in rest[0]:
        try:
            numbers = [int(n.strip()) for n in rest[0].split(",") if n.strip()]
            bonus   = int(rest[1]) if len(rest) > 1 and rest[1].strip().isdigit() else None
            return {"date": date_str, "numbers": numbers, "bonus": bonus}
        except ValueError:
            pass

    # Wide: each number in its own column
    nums: list[int] = []
    for col in rest:
        col = col.strip()
        if col.isdigit():
            nums.append(int(col))
        else:
            break  # stop at first non-numeric cell (e.g. multiplier string)

    if len(nums) < game["main_count"]:
        return None

    numbers = nums[: game["main_count"]]
    bonus   = (nums[game["main_count"]]
               if game["bonus_count"] > 0 and len(nums) > game["main_count"]
               else None)
    return {"date": date_str, "numbers": numbers, "bonus": bonus}


# ── Public API ────────────────────────────────────────────────────────────────

def import_draws_csv(game_id: int, filepath: str) -> dict:
    """
    Import draw records from *filepath* into the database for *game_id*.

    Returns:
        {"added": int, "skipped": int, "errors": list[str]}
    """
    game = get_game_by_id(game_id)
    if game is None:
        return {"added": 0, "skipped": 0, "errors": [f"Unknown game_id {game_id}"]}

    added = skipped = 0
    errors: list[str] = []

    # Read file
    try:
        with open(filepath, newline="", encoding="utf-8-sig") as f:
            sample = f.read(4096)
            f.seek(0)
            try:
                dialect = csv.Sniffer().sniff(sample, delimiters=",\t;")
            except csv.Error:
                dialect = csv.excel
            rows = list(csv.reader(f, dialect))
    except FileNotFoundError:
        return {"added": 0, "skipped": 0, "errors": [f"File not found: {filepath}"]}
    except Exception as e:
        return {"added": 0, "skipped": 0, "errors": [f"Could not read file: {e}"]}

    if not rows:
        return {"added": 0, "skipped": 0, "errors": ["File is empty"]}

    # Detect LottoSight export format by header
    lottosight_fmt = (
        len(rows[0]) >= 3
        and rows[0][0].strip().lower() == "game"
        and rows[0][1].strip().lower() == "date"
    )

    # Determine start row (skip header if present)
    start = 1 if (lottosight_fmt or _is_header(rows[0])) else 0

    for line_num, row in enumerate(rows[start:], start=start + 1):
        cells = [c.strip() for c in row]
        if not any(cells):
            continue  # blank line

        if lottosight_fmt:
            parsed = _parse_row_lottosight(cells)
        else:
            parsed = _parse_row_generic(cells, game)

        if parsed is None:
            errors.append(f"Line {line_num}: could not parse — {row}")
            continue

        numbers = parsed["numbers"]

        # Validate count
        if len(numbers) != game["main_count"]:
            errors.append(
                f"Line {line_num}: expected {game['main_count']} numbers, "
                f"got {len(numbers)}"
            )
            continue

        # Validate range
        bad = [n for n in numbers if not (1 <= n <= game["main_max"])]
        if bad:
            errors.append(
                f"Line {line_num}: numbers out of range 1–{game['main_max']}: {bad}"
            )
            continue

        result = insert_draw(
            game_id, parsed["date"], numbers,
            bonus=parsed["bonus"], source="csv_import",
        )
        if result == "inserted":
            added += 1
        else:
            skipped += 1

    return {"added": added, "skipped": skipped, "errors": errors}