"""
Générateur Factur-X BASIC via template Jinja2
"""

from jinja2 import Environment, FileSystemLoader
from dataclasses import dataclass, field
from typing import List, Optional
from datetime import date
from collections import defaultdict

from fastapi.templating import Jinja2Templates

templates = Jinja2Templates(directory="templates")

# ─────────────────────────────────────────────
# Structures de données (identiques au générateur lxml)
# ─────────────────────────────────────────────
@dataclass
class Address:
    line1: str
    city: str
    postcode: str
    country_code: str
    line2: Optional[str] = None


@dataclass
class Party:
    name: str
    vat_id: Optional[str] = None
    siret: Optional[str] = None
    address: Optional[Address] = None


@dataclass
class InvoiceLine:
    line_id: str
    description: str
    quantity: float
    unit_code: str
    unit_price: float
    vat_rate: float
    vat_category: str = "S"

# Raison d'exonération par catégorie TVA
EXEMPTION_REASONS = {
    "E": "TVA non applicable, art. 293 B du CGI",
    "Z": "Taux zéro",
    "AE": "Autoliquidation",
    "K": "Exonération intracommunautaire",
    "G": "Exportation hors UE",
}

@dataclass
class TaxLine:
    rate: float
    category: str
    base_amount: float
    amount: float
    exemption_reason: Optional[str] = None

@dataclass
class Invoice:
    number: str
    issue_date: date
    currency: str
    seller: Party
    buyer: Party
    lines: List[InvoiceLine] = field(default_factory=list)
    due_date: Optional[date] = None
    type_code: str = "380"
    payment_means_code: str = "30"
    iban: Optional[str] = None
    payment_reference: Optional[str] = None
    note: Optional[str] = None

    # Calculés automatiquement (voir compute())
    tax_lines: List[TaxLine] = field(default_factory=list)
    total_ht: float = 0.0
    total_tva: float = 0.0
    total_ttc: float = 0.0

    def compute(self):
        """Calcule les totaux et les lignes de TVA depuis les lignes de facture."""
        tax_groups = defaultdict(float)
        self.total_ht = 0.0

        for ln in self.lines:
            net = round(ln.quantity * ln.unit_price, 2)
            self.total_ht += net
            tax_groups[(ln.vat_rate, ln.vat_category)] += net

        self.total_ht = round(self.total_ht, 2)
        self.tax_lines = []
        self.total_tva = 0.0

        for (rate, category), base in tax_groups.items():
            base = round(base, 2)
            amount = round(base * rate / 100, 2)
            self.total_tva += amount
            self.tax_lines.append(TaxLine(
                rate=rate,
                category=category,
                base_amount=base,
                amount=amount,
                 # Raison d'exonération automatique si catégorie != "S" (standard)
                exemption_reason=EXEMPTION_REASONS.get(category) if category != "S" else None,
            ))

        self.total_tva = round(self.total_tva, 2)
        self.total_ttc = round(self.total_ht + self.total_tva, 2)


# ─────────────────────────────────────────────
# Filtres Jinja2 personnalisés
# ─────────────────────────────────────────────
def filter_amount(value: float) -> str:
    return f"{float(value):.2f}"


def filter_datefmt(value: date) -> str:
    return value.strftime("%Y%m%d")


# ─────────────────────────────────────────────
# Générateur
# ─────────────────────────────────────────────
def generate_facturx_xml(invoice: Invoice, template_dir: str = ".", output_file: str = "factur-x.xml") -> str:
    """
    Génère le XML Factur-X BASIC depuis le template Jinja2.
    Retourne le XML sous forme de chaîne et l'écrit dans output_file.
    """
    # Calcul des totaux
    invoice.compute()

    # Environnement Jinja2
    env = Environment(
        loader=FileSystemLoader(template_dir),
        autoescape=False,          # XML géré manuellement
        trim_blocks=True,          # supprime le \n après les blocs {% %}
        lstrip_blocks=True,        # supprime les espaces avant {% %}
    )
    env.filters["amount"] = filter_amount
    env.filters["datefmt"] = filter_datefmt

    template = env.get_template("templates/xml/factur-x-basic.xml.j2")
    xml_str = template.render(
        invoice=invoice,
        seller=invoice.seller,
        buyer=invoice.buyer,
    )

    with open(output_file, "w", encoding="utf-8") as f:
        f.write(xml_str)

    return xml_str


# ─────────────────────────────────────────────
# Exemple d'utilisation
# ─────────────────────────────────────────────
if __name__ == "__main__":

    invoice = Invoice(
        number="FA-2024-00123",
        issue_date=date(2024, 3, 15),
        due_date=date(2024, 4, 14),
        currency="EUR",
        type_code="380",
        note="Facture relative au contrat n°CTR-2024-01",

        seller=Party(
            name="Ma Société SAS",
            # vat_id absent : pas de numéro TVA en franchise (art. 293 B CGI)
            siret="12345678900012",
            address=Address(
                line1="10 rue de la Paix",
                city="Paris",
                postcode="75001",
                country_code="FR",
            ),
        ),

        buyer=Party(
            name="Client SARL",
            vat_id="FR98765432100",
            siret="98765432100011",
            address=Address(
                line1="5 avenue des Fleurs",
                city="Lyon",
                postcode="69001",
                country_code="FR",
            ),
        ),

        payment_means_code="30",
        iban="FR7612345678901234567890189",
        payment_reference="CTR-2024-01",
    )

    # Ajout des lignes — franchise de TVA (art. 293 B du CGI)
    # Utiliser vat_category="E" et vat_rate=0.0
    articles = [
        {"desc": "Développement logiciel - Sprint 1", "qty": 10, "unit": "HUR", "prix": 150.0, "tva": 0.0, "cat": "E"},
        {"desc": "Licence logicielle annuelle",        "qty":  1, "unit": "C62", "prix": 500.0, "tva": 0.0, "cat": "E"},
        {"desc": "Formation utilisateurs",             "qty":  2, "unit": "HUR", "prix": 200.0, "tva": 0.0, "cat": "E"},
    ]

    for i, art in enumerate(articles, start=1):
        invoice.lines.append(InvoiceLine(
            line_id=str(i),
            description=art["desc"],
            quantity=art["qty"],
            unit_code=art["unit"],
            unit_price=art["prix"],
            vat_rate=art["tva"],
            vat_category=art["cat"],   # "E" = exonéré (franchise TVA)
        ))

    xml = generate_facturx_xml(invoice, template_dir=".", output_file="factur-x.xml")

    print(f"✅ Fichier généré : factur-x.xml")
    print(f"   Total HT  : {invoice.total_ht:.2f} €")
    print(f"   TVA 20%   : {invoice.total_tva:.2f} €")
    print(f"   Total TTC : {invoice.total_ttc:.2f} €")