#!/usr/bin/env python3
"""Affiche quelques statistiques basiques sur les fichiers CSV météo."""

from __future__ import annotations

import argparse
import csv
from dataclasses import dataclass
from datetime import datetime
from pathlib import Path

ROOT = Path(__file__).resolve().parents[1]
DEFAULT_TARGETS = [
    ("Données brutes complètes", ROOT / "data/weather_raw_full.csv"),
    ("Données agrégées par minute", ROOT / "data/weather_minutely.csv"),
]


@dataclass
class DatasetStats:
    label: str
    path: Path
    size_bytes: int
    columns: list[str]
    row_count: int
    header_detected: bool
    first_timestamp: datetime | None
    last_timestamp: datetime | None


def human_size(num_bytes: int) -> str:
    """Retourne une taille lisible (o/Ko/Mo/Go) à partir d'un nombre d'octets."""
    units = ["o", "Ko", "Mo", "Go", "To"]
    size = float(num_bytes)
    for unit in units:
        if size < 1024 or unit == units[-1]:
            return f"{size:.1f} {unit}"
        size /= 1024
    return f"{num_bytes} o"


def format_int(value: int) -> str:
    """Formate un entier avec des espaces pour les milliers."""
    return f"{value:,}".replace(",", " ")


def parse_timestamp(value: str) -> datetime | None:
    if not value:
        return None
    try:
        return datetime.fromisoformat(value.strip())
    except ValueError:
        return None


def collect_stats(label: str, path: Path, delimiter: str, assume_header: bool) -> DatasetStats:
    if not path.exists():
        raise FileNotFoundError(path)

    columns: list[str] = []
    row_count = 0
    first_ts: datetime | None = None
    last_ts: datetime | None = None
    size_bytes = path.stat().st_size

    with path.open("r", encoding="utf-8", newline="") as handle:
        reader = csv.reader(handle, delimiter=delimiter)
        first_line = next(reader, None)

        if first_line is None:
            header_detected = False
        else:
            columns = [col.strip() for col in first_line]
            header_detected = bool(columns) and assume_header

            # Détermine la première ligne de données en fonction du mode d'en-tête.
            data_row = next(reader, None) if header_detected else first_line
            if data_row is not None:
                row_count = 1
                ts = parse_timestamp(data_row[0]) if data_row else None
                if ts:
                    first_ts = last_ts = ts

            for row in reader:
                row_count += 1
                ts = parse_timestamp(row[0]) if row else None
                if ts:
                    if first_ts is None or ts < first_ts:
                        first_ts = ts
                    if last_ts is None or ts > last_ts:
                        last_ts = ts

    return DatasetStats(
        label=label,
        path=path,
        size_bytes=size_bytes,
        columns=columns,
        row_count=row_count,
        header_detected=header_detected,
        first_timestamp=first_ts,
        last_timestamp=last_ts,
    )


def format_path(path: Path) -> str:
    try:
        return str(path.relative_to(ROOT))
    except ValueError:
        return str(path)


def display_stats(stats: DatasetStats) -> None:
    header = ", ".join(stats.columns) if stats.columns else "-"
    header_note = " (en-tête détecté)" if stats.header_detected else ""
    first_ts = stats.first_timestamp.isoformat(sep=" ") if stats.first_timestamp else "-"
    last_ts = stats.last_timestamp.isoformat(sep=" ") if stats.last_timestamp else "-"

    print(f"\n=== {stats.label}")
    print(f"- Fichier : {format_path(stats.path)}")
    print(f"- Taille : {human_size(stats.size_bytes)} ({format_int(stats.size_bytes)} octets)")
    print(f"- Colonnes : {len(stats.columns)}{header_note}")
    print(f"  {header}")
    print(f"- Lignes (hors en-tête) : {format_int(stats.row_count)}")
    print(f"- Premier enregistrement : {first_ts}")
    print(f"- Dernier enregistrement  : {last_ts}")


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Affiche quelques statistiques basiques sur les CSV météo (taille, colonnes, lignes).",
    )
    parser.add_argument(
        "files",
        nargs="*",
        type=Path,
        help="Fichiers CSV à inspecter (par défaut : les CSV bruts et agrégés du dossier data/).",
    )
    parser.add_argument(
        "--delimiter",
        default=",",
        help="Délimiteur des colonnes (par défaut : ',').",
    )
    parser.add_argument(
        "--no-header",
        action="store_true",
        help="Ne pas soustraire la première ligne lors du comptage des lignes.",
    )
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    targets = [(path.name, path) for path in args.files] if args.files else DEFAULT_TARGETS
    assume_header = not args.no_header

    for label, path in targets:
        try:
            stats = collect_stats(label, path, delimiter=args.delimiter, assume_header=assume_header)
        except FileNotFoundError:
            print(f"\n✘ Fichier introuvable : {format_path(path)}")
            continue
        display_stats(stats)


if __name__ == "__main__":
    main()