from django.db import models
from django.contrib.auth.models import User
from expenses.models import Project, Category, Vendor
from decimal import Decimal
import uuid

class UnitOfMeasureEnum(models.TextChoices):
    UNIDAD = 'UN', 'Unidad (UN)'
    MES = 'MES', 'Mes de Servicio'
    DIA = 'DIA', 'Día / Jornada'
    HORA = 'HORA', 'Hora Especialista'
    LITRO = 'LITRO', 'Litros'
    GLOBAL = 'GLB', 'Servicio Global'
    LICENCIA = 'LIC', 'Licencia Anual / Mensual'

class RequisitionPriorityEnum(models.TextChoices):
    BAJA = 'BAJA', 'Baja'
    MEDIA = 'MEDIA', 'Media'
    ALTA = 'ALTA', 'Alta'
    CRITICA = 'CRITICA', 'Crítica / Faena Urgente'

class RequisitionStatusEnum(models.TextChoices):
    BORRADOR = 'BORRADOR', 'Borrador'
    SOLICITADA = 'SOLICITADA', 'Solicitada (Pendiente Aprobación)'
    APROBADA_TECNICA = 'APROBADA_TECNICA', 'Aprobada Técnicamente'
    APROBADA_FINANZAS = 'APROBADA_FINANZAS', 'Aprobada por Finanzas'
    RECHAZADA = 'RECHAZADA', 'Rechazada'
    CONVERTIDA_OC = 'CONVERTIDA_OC', 'Orden de Compra Generada'

class PurchaseOrderStatusEnum(models.TextChoices):
    EMITIDA = 'EMITIDA', 'Emitida'
    ENVIADA_PROVEEDOR = 'ENVIADA_PROVEEDOR', 'Enviada al Proveedor'
    RECEPCION_PARCIAL = 'RECEPCION_PARCIAL', 'Recepción Parcial'
    RECEPCION_TOTAL = 'RECEPCION_TOTAL', 'Recepción Conforme Total'
    CONCILIADA_MATCH = 'CONCILIADA_MATCH', '3-Way Match Conciliado'
    CANCELADA = 'CANCELADA', 'Cancelada'

class MatchStatusEnum(models.TextChoices):
    MATCH_PERFECTO = 'MATCH_PERFECTO', 'Match Perfecto (Tolerancia 0% OK)'
    DISCREPANCIA_PRECIO = 'DISCREPANCIA_PRECIO', 'Discrepancia en Precio / Monto Neto'
    DISCREPANCIA_CANTIDAD = 'DISCREPANCIA_CANTIDAD', 'Discrepancia en Cantidades Recibidas'
    PENDIENTE_RECEPCION = 'PENDIENTE_RECEPCION', 'Pendiente de Recepción en Bodega/Faena'
    RECHAZADO = 'RECHAZADO', 'Rechazado por Auditoría'


class ItemCatalog(models.Model):
    """
    Catálogo Oficial de Bienes, Servicios, Vehículos y Licencias EFINTEL (CAT-VEH-01 a CAT-SFT-09).
    """
    code = models.CharField(max_length=50, unique=True, verbose_name="Código Ítem (CAT-XXX-XX)")
    name = models.CharField(max_length=200, verbose_name="Descripción del Bien / Servicio")
    category = models.ForeignKey(Category, on_delete=models.SET_NULL, null=True, blank=True, related_name='catalog_items', verbose_name="Categoría Contable")
    unit = models.CharField(max_length=20, choices=UnitOfMeasureEnum.choices, default=UnitOfMeasureEnum.UNIDAD, verbose_name="Unidad de Medida")
    
    reference_price_clp = models.DecimalField(max_digits=12, decimal_places=2, verbose_name="Precio Referencial Neto (CLP)")
    reference_price_usd = models.DecimalField(max_digits=10, decimal_places=2, default=0, verbose_name="Precio Referencial (USD)")
    sla_days = models.IntegerField(default=3, verbose_name="SLA / Plazo de Entrega (Días)")
    
    preferred_vendor = models.ForeignKey(Vendor, on_delete=models.SET_NULL, null=True, blank=True, related_name='catalog_items', verbose_name="Proveedor Homologado / Preferido")
    specifications = models.TextField(blank=True, verbose_name="Especificaciones Técnicas")
    is_active = models.BooleanField(default=True, verbose_name="Ítem Activo en Catálogo")

    def __str__(self):
        return f"{self.code} - {self.name} (${self.reference_price_clp:,.0f} CLP)"

    class Meta:
        verbose_name = "Ítem de Catálogo"
        verbose_name_plural = "Catálogo de Ítems y Servicios"
        ordering = ['code']


class PurchaseRequisition(models.Model):
    """
    Requisición Interna de Compra (REQ-2026-XXXX).
    Inicia el flujo de abastecimiento y aprobación técnica/financiera.
    """
    code = models.CharField(max_length=50, unique=True, verbose_name="Código Requisición", default="REQ-2026-0001")
    requester = models.ForeignKey(User, on_delete=models.PROTECT, related_name='purchase_requisitions', verbose_name="Solicitante")
    project = models.ForeignKey(Project, on_delete=models.PROTECT, related_name='purchase_requisitions', verbose_name="Proyecto / Centro de Costo")
    
    purpose = models.TextField(verbose_name="Justificación Técnica y Destino I+D+i")
    priority = models.CharField(max_length=30, choices=RequisitionPriorityEnum.choices, default=RequisitionPriorityEnum.MEDIA, verbose_name="Prioridad")
    status = models.CharField(max_length=30, choices=RequisitionStatusEnum.choices, default=RequisitionStatusEnum.BORRADOR, verbose_name="Estado de Aprobación")
    
    required_date = models.DateField(verbose_name="Fecha Requerida en Sitio")
    
    approved_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True, related_name='approved_requisitions', verbose_name="Aprobado por")
    approved_at = models.DateTimeField(null=True, blank=True, verbose_name="Fecha de Aprobación")
    rejection_reason = models.TextField(blank=True, verbose_name="Motivo de Rechazo")
    
    total_estimated_clp = models.DecimalField(max_digits=15, decimal_places=2, default=0, verbose_name="Total Estimado Neto (CLP)")
    
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return f"{self.code} - {self.project.code} ({self.get_status_display()})"

    def recalculate_total(self):
        total = sum(item.subtotal for item in self.items.all())
        self.total_estimated_clp = total
        self.save(update_fields=['total_estimated_clp'])

    class Meta:
        verbose_name = "Requisición de Compra"
        verbose_name_plural = "Requisiciones de Compra"
        ordering = ['-created_at']


class RequisitionItem(models.Model):
    requisition = models.ForeignKey(PurchaseRequisition, on_delete=models.CASCADE, related_name='items', verbose_name="Requisición")
    catalog_item = models.ForeignKey(ItemCatalog, on_delete=models.SET_NULL, null=True, blank=True, related_name='requisition_items', verbose_name="Ítem del Catálogo")
    description = models.CharField(max_length=255, verbose_name="Descripción / Detalle")
    quantity = models.DecimalField(max_digits=10, decimal_places=2, default=1, verbose_name="Cantidad")
    unit_price = models.DecimalField(max_digits=12, decimal_places=2, verbose_name="Precio Unitario Estimado (CLP)")
    subtotal = models.DecimalField(max_digits=12, decimal_places=2, default=0, verbose_name="Subtotal (CLP)")

    def save(self, *args, **kwargs):
        self.subtotal = self.quantity * self.unit_price
        super().save(*args, **kwargs)

    def __str__(self):
        return f"{self.quantity} x {self.description} (${self.subtotal:,.0f})"


class PurchaseOrder(models.Model):
    """
    Orden de Compra Oficial (OC-2026-XXXX).
    Cálculo formal Neto + 19% IVA = Total Facturable.
    """
    code = models.CharField(max_length=50, unique=True, verbose_name="Correlativo OC", default="OC-2026-0001")
    requisition = models.ForeignKey(PurchaseRequisition, on_delete=models.SET_NULL, null=True, blank=True, related_name='purchase_orders', verbose_name="Requisición de Origen")
    vendor = models.ForeignKey(Vendor, on_delete=models.PROTECT, related_name='purchase_orders', verbose_name="Proveedor")
    project = models.ForeignKey(Project, on_delete=models.PROTECT, related_name='purchase_orders', verbose_name="Proyecto")
    issuer = models.ForeignKey(User, on_delete=models.PROTECT, related_name='issued_purchase_orders', verbose_name="Emitido por")
    
    issue_date = models.DateField(verbose_name="Fecha de Emisión")
    expected_delivery_date = models.DateField(null=True, blank=True, verbose_name="Fecha Estimada de Entrega")
    payment_terms = models.CharField(max_length=100, default="30 Días Contra Factura", verbose_name="Condiciones de Pago")
    delivery_address = models.CharField(max_length=255, default="Casa Matriz EFINTEL / Terreno Faena", verbose_name="Lugar de Entrega")
    
    # Financial fields
    net_amount_clp = models.DecimalField(max_digits=15, decimal_places=2, default=0, verbose_name="Monto Neto (CLP)")
    tax_rate = models.DecimalField(max_digits=5, decimal_places=2, default=19.00, verbose_name="Tasa IVA (%)")
    tax_amount_clp = models.DecimalField(max_digits=15, decimal_places=2, default=0, verbose_name="Monto IVA (CLP)")
    total_amount_clp = models.DecimalField(max_digits=15, decimal_places=2, default=0, verbose_name="Monto Total (CLP)")
    
    status = models.CharField(max_length=30, choices=PurchaseOrderStatusEnum.choices, default=PurchaseOrderStatusEnum.EMITIDA, verbose_name="Estado de Orden de Compra")
    terms_and_conditions = models.TextField(blank=True, verbose_name="Términos y Condiciones Especiales")
    notes = models.TextField(blank=True, verbose_name="Notas Internas")
    
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def recalculate_totals(self):
        neto = sum(item.subtotal_net for item in self.items.all())
        iva = (neto * Decimal('0.19')).quantize(Decimal('1'))
        total = neto + iva
        self.net_amount_clp = neto
        self.tax_amount_clp = iva
        self.total_amount_clp = total
        self.save(update_fields=['net_amount_clp', 'tax_amount_clp', 'total_amount_clp'])

    def __str__(self):
        return f"{self.code} - {self.vendor.name} (${self.total_amount_clp:,.0f} CLP)"

    class Meta:
        verbose_name = "Orden de Compra"
        verbose_name_plural = "Órdenes de Compra (OC)"
        ordering = ['-issue_date', '-created_at']


class PurchaseOrderItem(models.Model):
    purchase_order = models.ForeignKey(PurchaseOrder, on_delete=models.CASCADE, related_name='items', verbose_name="Orden de Compra")
    catalog_item = models.ForeignKey(ItemCatalog, on_delete=models.SET_NULL, null=True, blank=True, verbose_name="Ítem del Catálogo")
    description = models.CharField(max_length=255, verbose_name="Descripción del Bien / Servicio")
    quantity = models.DecimalField(max_digits=10, decimal_places=2, default=1, verbose_name="Cantidad")
    unit_price_net = models.DecimalField(max_digits=12, decimal_places=2, verbose_name="Precio Unitario Neto (CLP)")
    subtotal_net = models.DecimalField(max_digits=12, decimal_places=2, default=0, verbose_name="Subtotal Neto (CLP)")

    def save(self, *args, **kwargs):
        self.subtotal_net = self.quantity * self.unit_price_net
        super().save(*args, **kwargs)

    def __str__(self):
        return f"{self.quantity} x {self.description} (${self.subtotal_net:,.0f} Neto)"


class GoodsReceipt(models.Model):
    """
    Recepción Conforme en Bodega o Terreno.
    """
    code = models.CharField(max_length=50, unique=True, verbose_name="N° Acta Recepción", default="REC-2026-0001")
    purchase_order = models.ForeignKey(PurchaseOrder, on_delete=models.PROTECT, related_name='receipts', verbose_name="Orden de Compra")
    dispatch_guide_number = models.CharField(max_length=50, verbose_name="N° Guía de Despacho / Acta Terreno")
    receipt_date = models.DateField(verbose_name="Fecha de Recepción")
    received_by = models.ForeignKey(User, on_delete=models.PROTECT, related_name='received_deliveries', verbose_name="Receptor Conforme")
    
    technical_conformity = models.BooleanField(default=True, verbose_name="Conformidad Técnica Aprobada")
    notes = models.TextField(blank=True, verbose_name="Observaciones de Entrega / Inspección")
    created_at = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f"{self.code} - Guía {self.dispatch_guide_number} (OC: {self.purchase_order.code})"

    class Meta:
        verbose_name = "Recepción de Bienes / Servicios"
        verbose_name_plural = "Recepciones de Bienes y Servicios"
        ordering = ['-receipt_date']


class ThreeWayMatch(models.Model):
    """
    Módulo de Conciliación 3-Way Match con tolerancia 0%.
    Compara:
    1. Orden de Compra (OC autorizada)
    2. Recepción Física (Guía de Despacho / Acta de Conformidad)
    3. Factura Electrónica SII (DTE 33)
    """
    purchase_order = models.OneToOneField(PurchaseOrder, on_delete=models.PROTECT, related_name='three_way_match', verbose_name="Orden de Compra")
    goods_receipt = models.ForeignKey(GoodsReceipt, on_delete=models.SET_NULL, null=True, blank=True, related_name='matches', verbose_name="Recepción Conforme")
    
    # Datos Factura Electrónica SII DTE 33
    dte_invoice_number = models.CharField(max_length=50, verbose_name="N° Factura Electrónica (DTE 33)")
    dte_invoice_rut = models.CharField(max_length=20, verbose_name="RUT Emisor Factura")
    dte_invoice_date = models.DateField(verbose_name="Fecha Emisión Factura")
    
    dte_net_amount = models.DecimalField(max_digits=15, decimal_places=2, verbose_name="Monto Neto Factura (CLP)")
    dte_tax_amount = models.DecimalField(max_digits=15, decimal_places=2, verbose_name="Monto IVA Factura (CLP)")
    dte_total_amount = models.DecimalField(max_digits=15, decimal_places=2, verbose_name="Monto Total Factura (CLP)")
    
    # Discrepancias calculadas (Tolerancia 0%)
    price_difference_clp = models.DecimalField(max_digits=12, decimal_places=2, default=0, verbose_name="Diferencia de Monto Neto (CLP)")
    quantity_difference = models.DecimalField(max_digits=10, decimal_places=2, default=0, verbose_name="Diferencia en Cantidades")
    
    match_status = models.CharField(max_length=30, choices=MatchStatusEnum.choices, default=MatchStatusEnum.PENDIENTE_RECEPCION, verbose_name="Resultado del 3-Way Match")
    
    matched_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True, verbose_name="Auditor / Conciliador")
    matched_at = models.DateTimeField(null=True, blank=True, verbose_name="Fecha de Conciliación")
    resolution_notes = models.TextField(blank=True, verbose_name="Notas de Resolución / Observación Contable")
    
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return f"Match OC {self.purchase_order.code} vs Fac {self.dte_invoice_number} ({self.get_match_status_display()})"

    class Meta:
        verbose_name = "Conciliación 3-Way Match"
        verbose_name_plural = "Conciliaciones 3-Way Match (Tolerancia 0%)"
        ordering = ['-created_at']