"""
Logique partagée d'import / mise à jour de ContractPost depuis un fichier
Excel de type « Inventaire E24.143 » (format SPRB-GOB/Fonteinen).

Structure des colonnes (0-indexé) :
  0  – Nr. Post           → order_number
  1  – Code Fontaine      → code
  2  – Beschrijving NL    → description_nl
  3  – AO/TVS             → is_amount_to_be_justified (TVS = True)
  4  – Unité NL           → fallback unit
  5  – Description FR     → description_fr
  6  – NC                 (ignoré)
  7  – U (unité FR)       → unit (prioritaire)
  8  – Quantité présumée  (ignorée : pas mappée au modèle)
  9  – Prix unitaire      → unit_price
  10 – Total par poste    (ignoré : calculable)

Utilisé depuis :
  - contracts/management/commands/import_contract_posts.py
  - contracts/admin.py (vue d'import)
"""

from decimal import Decimal, InvalidOperation

import openpyxl

from .models import Contract, ContractPost


# ---------------------------------------------------------------------------
# Utilitaires internes
# ---------------------------------------------------------------------------

def _to_decimal(value):
    if value is None:
        return None
    try:
        return Decimal(str(value))
    except (InvalidOperation, ValueError):
        return None


def _clean(value):
    if value is None:
        return ''
    return str(value).strip()


# ---------------------------------------------------------------------------
# Fonction principale
# ---------------------------------------------------------------------------

def import_contract_posts(contract: Contract, excel_source, *, dry_run: bool = False,
                          update_existing: bool = False, log=None) -> dict:
    """
    Importe (ou met à jour) les postes d'un contrat depuis un fichier Excel.

    Paramètres
    ----------
    contract        : instance Contract cible
    excel_source    : chemin fichier (str/Path) ou objet fichier ouvert (bytes-like)
    dry_run         : si True, ne persiste rien en base
    update_existing : si True, met à jour les postes existants (même order_number) ;
                      si False, les ignore
    log             : callable(str) pour afficher des messages ; défaut = print

    Retour
    ------
    dict avec les clés :
      total_rows, created, updated, skipped_already_exists, skipped_no_price, errors
    """
    if log is None:
        log = print

    stats = {
        'total_rows': 0,
        'created': 0,
        'updated': 0,
        'skipped_already_exists': 0,
        'skipped_no_price': 0,
        'errors': 0,
    }

    # ------------------------------------------------------------------
    # Ouverture du classeur (chemin ou objet fichier)
    # ------------------------------------------------------------------
    try:
        wb = openpyxl.load_workbook(
            excel_source, read_only=True, data_only=True, keep_vba=False
        )
    except Exception as exc:
        log(f"ERREUR ouverture Excel : {exc}")
        stats['errors'] += 1
        return stats

    ws = wb.active
    log(f"Feuille lue : {ws.title}")

    # ------------------------------------------------------------------
    # Map order_number → ContractPost existants pour le contrat
    # ------------------------------------------------------------------
    existing_map = {
        p.order_number: p
        for p in ContractPost.objects.filter(contract=contract)
    }

    posts_to_create = []
    posts_to_update = []
    fields_to_update = [
        'code', 'description_fr', 'description_nl',
        'unit', 'unit_price', 'is_amount_to_be_justified',
    ]

    for row_num, row in enumerate(ws.iter_rows(values_only=True), start=1):
        # Ne garder que les lignes avec un entier en colonne A (Nr. Post)
        raw_num = row[0] if len(row) > 0 else None
        if not isinstance(raw_num, (int, float)) or raw_num != int(raw_num):
            continue

        stats['total_rows'] += 1
        order_number = int(raw_num)

        code             = _clean(row[1] if len(row) > 1 else None)
        description_nl   = _clean(row[2] if len(row) > 2 else None)
        ao               = _clean(row[3] if len(row) > 3 else None)
        unit_nl          = _clean(row[4] if len(row) > 4 else None)
        description_fr   = _clean(row[5] if len(row) > 5 else None)
        unit_fr          = _clean(row[7] if len(row) > 7 else None)
        unit_price       = _to_decimal(row[9] if len(row) > 9 else None)

        unit = unit_fr if unit_fr else unit_nl
        is_amount_to_be_justified = ao.upper() == 'TVS'

        if unit_price is None:
            log(f"  Ligne {row_num}: poste {order_number} – prix unitaire manquant, ignoré")
            stats['skipped_no_price'] += 1
            continue

        if order_number in existing_map:
            if not update_existing:
                log(f"  Ligne {row_num}: poste {order_number} ({code}) – déjà présent, ignoré")
                stats['skipped_already_exists'] += 1
                continue

            # Mise à jour
            post = existing_map[order_number]
            post.code = code
            post.description_fr = description_fr
            post.description_nl = description_nl
            post.unit = unit
            post.unit_price = unit_price
            post.is_amount_to_be_justified = is_amount_to_be_justified
            posts_to_update.append(post)
            log(
                f"  [UPDATE] poste {order_number:3d} | {code:<12} | "
                f"{unit_price:>10} | {description_fr[:60]}"
            )
            stats['updated'] += 1
        else:
            posts_to_create.append(ContractPost(
                contract=contract,
                code=code,
                description_fr=description_fr,
                description_nl=description_nl,
                order_number=order_number,
                unit=unit,
                unit_price=unit_price,
                is_amount_to_be_justified=is_amount_to_be_justified,
            ))
            log(
                f"  [CREATE] poste {order_number:3d} | {code:<12} | "
                f"{unit_price:>10} | {description_fr[:60]}"
            )
            stats['created'] += 1

    # ------------------------------------------------------------------
    # Persistance
    # ------------------------------------------------------------------
    if not dry_run:
        from django.db import transaction
        try:
            with transaction.atomic():
                if posts_to_create:
                    ContractPost.objects.bulk_create(posts_to_create)
                if posts_to_update:
                    ContractPost.objects.bulk_update(posts_to_update, fields_to_update)
        except Exception as exc:
            import traceback
            log(f"\nERREUR lors de l'écriture en base : {exc}")
            traceback.print_exc()
            stats['errors'] += stats['created'] + stats['updated']
            stats['created'] = 0
            stats['updated'] = 0

    return stats