import enum
import uuid
from sqlalchemy import (
    JSON,
    Boolean,
    Column,
    DateTime,
    Enum as SQLEnum,
    Float,
    ForeignKey,
    Integer,
    Numeric,
    String,
    Text,
    UniqueConstraint,
)
from sqlalchemy.orm import relationship
from sqlalchemy.sql import func

from core.database import Base


class AccountType(str, enum.Enum):
    ASSET = "asset"
    LIABILITY = "liability"
    EQUITY = "equity"
    REVENUE = "revenue"
    EXPENSE = "expense"

class TransactionStatus(str, enum.Enum):
    PENDING = "pending"
    POSTED = "posted"
    FAILED = "failed"
    CANCELLED = "cancelled"

class EntryType(str, enum.Enum):
    DEBIT = "debit"
    CREDIT = "credit"

class EntityType(str, enum.Enum):
    VENDOR = "vendor"
    CUSTOMER = "customer"
    BOTH = "both"

class BillStatus(str, enum.Enum):
    DRAFT = "draft"
    OPEN = "open"
    PAID = "paid"
    VOID = "void"

class InvoiceStatus(str, enum.Enum):
    DRAFT = "draft"
    OPEN = "open"
    PAID = "paid"
    VOID = "void"
    OVERDUE = "overdue"

class Account(Base):
    __tablename__ = "accounting_accounts"
    __table_args__ = {'extend_existing': True}

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    name = Column(String, nullable=False)
    code = Column(String, nullable=False) # e.g., "1000", "5000"
    type = Column(SQLEnum(AccountType), nullable=False)
    description = Column(Text, nullable=True)
    is_active = Column(Boolean, default=True)
    parent_id = Column(String, ForeignKey("accounting_accounts.id"), nullable=True)
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    standards_mapping = Column(JSON, nullable=True) # e.g. {"gaap": "1001", "ifrs": "ASSET_CASH"}
    last_audit_at = Column(DateTime(timezone=True), nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

    __table_args__ = (
        UniqueConstraint('workspace_id', 'code', name='_workspace_code_uc'),
    )

    # Relationships
    parent = relationship("Account", remote_side=[id], backref="sub_accounts")
    entries = relationship("JournalEntry", back_populates="account")

class Transaction(Base):
    """Event-sourced transaction header

    All transactions MUST have a category for cost attribution accuracy.
    The category field enforces that every cost is properly categorized,
    preventing uncategorized transactions that would bypass budget tracking.
    """
    __tablename__ = "accounting_transactions"
    __table_args__ = {'extend_existing': True}  # Resolve SQLAlchemy metadata conflict with core/models.py

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    external_id = Column(String, nullable=True, index=True) # e.g. Stripe ID, Bank ID
    source = Column(String, nullable=False) # e.g. "stripe", "manual", "bank_feed"
    status = Column(SQLEnum(TransactionStatus), default=TransactionStatus.PENDING)
    transaction_date = Column(DateTime(timezone=True), nullable=False)
    description = Column(Text, nullable=True)
    amount = Column(Numeric(precision=19, scale=4), nullable=True) # Denormalized for convenience
    metadata_json = Column(JSON, nullable=True)
    is_intercompany = Column(Boolean, default=False)
    counterparty_workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=True)

    # Cost Attribution - Category is NOT NULL to enforce cost categorization
    # Standard categories: llm_tokens, compute, storage, network, labor, software,
    # infrastructure, support, sales, other
    category = Column(String(50), nullable=False, index=True, default='other')

    # Project Linking
    project_id = Column(String, ForeignKey("service_projects.id"), nullable=True)
    milestone_id = Column(String, ForeignKey("service_milestones.id"), nullable=True)

    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

    # Relationships
    journal_entries = relationship("JournalEntry", back_populates="transaction", cascade="all, delete-orphan")

class JournalEntry(Base):
    """The double-entry record"""
    __tablename__ = "accounting_journal_entries"
    __table_args__ = {'extend_existing': True}  # Resolve SQLAlchemy metadata conflict with core/models.py

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    transaction_id = Column(String, ForeignKey("accounting_transactions.id"), nullable=False)
    account_id = Column(String, ForeignKey("accounting_accounts.id"), nullable=False)
    type = Column(SQLEnum(EntryType), nullable=False)
    amount = Column(Numeric(precision=19, scale=4), nullable=False)
    currency = Column(String, default="USD")
    description = Column(Text, nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())

    # Relationships
    transaction = relationship("Transaction", back_populates="journal_entries")
    account = relationship("Account", back_populates="entries")

class CategorizationProposal(Base):
    """AI-generated categorization suggestion"""
    __tablename__ = "accounting_categorization_proposals"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    transaction_id = Column(String, ForeignKey("accounting_transactions.id"), nullable=False)
    suggested_account_id = Column(String, ForeignKey("accounting_accounts.id"), nullable=False)
    confidence = Column(Float, nullable=False) # 0.0 to 1.0
    reasoning = Column(Text, nullable=True)
    is_accepted = Column(Boolean, nullable=True) # True: accepted, False: rejected, None: pending
    reviewed_by = Column(String, ForeignKey("users.id"), nullable=True)
    reviewed_at = Column(DateTime(timezone=True), nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())

    # Relationships
    transaction = relationship("Transaction", backref="proposals")
    suggested_account = relationship("Account")

class Entity(Base):
    """Vendors and Customers"""
    __tablename__ = "accounting_entities"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    name = Column(String, nullable=False)
    email = Column(String, nullable=True)
    phone = Column(String, nullable=True)
    address = Column(Text, nullable=True)
    type = Column(SQLEnum(EntityType), nullable=False)
    tax_id = Column(String, nullable=True) # e.g. TIN, VAT
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

    # Relationships
    bills = relationship("Bill", back_populates="vendor")
    invoices = relationship("Invoice", back_populates="customer")

class Bill(Base):
    """Accounts Payable (Obligation to pay a vendor)"""
    __tablename__ = "accounting_bills"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    vendor_id = Column(String, ForeignKey("accounting_entities.id"), nullable=False)
    bill_number = Column(String, nullable=True)
    issue_date = Column(DateTime(timezone=True), nullable=False)
    due_date = Column(DateTime(timezone=True), nullable=False)
    amount = Column(Numeric(precision=19, scale=4), nullable=False)
    currency = Column(String, default="USD")
    status = Column(SQLEnum(BillStatus), default=BillStatus.DRAFT)
    description = Column(Text, nullable=True)
    transaction_id = Column(String, ForeignKey("accounting_transactions.id"), nullable=True) # Linked ledger tx
    
    # Project Linking
    project_id = Column(String, ForeignKey("service_projects.id"), nullable=True)
    milestone_id = Column(String, ForeignKey("service_milestones.id"), nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

    # Relationships
    vendor = relationship("Entity", back_populates="bills")
    ledger_transaction = relationship("Transaction")
    documents = relationship("Document", back_populates="bill", cascade="all, delete-orphan")

class Invoice(Base):
    """Accounts Receivable (Obligation to be paid by a customer)"""
    __tablename__ = "accounting_invoices"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    customer_id = Column(String, ForeignKey("accounting_entities.id"), nullable=False)
    invoice_number = Column(String, nullable=True)
    issue_date = Column(DateTime(timezone=True), nullable=False)
    due_date = Column(DateTime(timezone=True), nullable=False)
    amount = Column(Numeric(precision=19, scale=4), nullable=False)
    currency = Column(String, default="USD")
    status = Column(SQLEnum(InvoiceStatus), default=InvoiceStatus.DRAFT)
    description = Column(Text, nullable=True)
    transaction_id = Column(String, ForeignKey("accounting_transactions.id"), nullable=True) # Linked ledger tx
    metadata_json = Column(JSON, nullable=True) # Additional invoice metadata (line items, billing details, etc.)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())

    # Relationships
    customer = relationship("Entity", back_populates="invoices")
    ledger_transaction = relationship("Transaction")
    documents = relationship("Document", back_populates="invoice", cascade="all, delete-orphan")

class Document(Base):
    """Financial documents (receipts, bills, invoices)"""
    __tablename__ = "accounting_documents"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    file_path = Column(String, nullable=False)
    file_name = Column(String, nullable=False)
    file_type = Column(String, nullable=True) # e.g. "pdf", "image"
    bill_id = Column(String, ForeignKey("accounting_bills.id"), nullable=True)
    invoice_id = Column(String, ForeignKey("accounting_invoices.id"), nullable=True)
    extracted_data = Column(JSON, nullable=True) # Cache of AI extraction results
    created_at = Column(DateTime(timezone=True), server_default=func.now())

    # Relationships
    bill = relationship("Bill", back_populates="documents")
    invoice = relationship("Invoice", back_populates="documents")

class TaxNexus(Base):
    """Identified tax presence in a jurisdiction"""
    __tablename__ = "accounting_tax_nexus"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    region = Column(String, nullable=False) # e.g. "California", "NY", "UK"
    tax_type = Column(String, default="Sales Tax")
    is_active = Column(Boolean, default=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())

class FinancialClose(Base):
    """Tracks status of periodic financial closes"""
    __tablename__ = "accounting_closes"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    period = Column(String, nullable=False) # e.g. "2025-10"
    is_closed = Column(Boolean, default=False)
    closed_at = Column(DateTime(timezone=True), nullable=True)
    closed_by = Column(String, ForeignKey("users.id"), nullable=True)
    metadata_json = Column(JSON, nullable=True) # Checklists, blockers
    created_at = Column(DateTime(timezone=True), server_default=func.now())

class CategorizationRule(Base):
    """Learned or manual rules for auto-categorization"""
    __tablename__ = "accounting_rules"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    merchant_pattern = Column(String, nullable=False) # e.g. "Amazon", "Starbucks"
    target_account_id = Column(String, ForeignKey("accounting_accounts.id"), nullable=False)
    confidence_weight = Column(Float, default=1.0) # Increases as user accepts more
    is_active = Column(Boolean, default=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())

    __table_args__ = (
        UniqueConstraint('workspace_id', 'merchant_pattern', name='_workspace_merchant_uc'),
    )

class Budget(Base):
    """Budget constraints for projects or departments"""
    __tablename__ = "accounting_budgets"

    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
    workspace_id = Column(String, ForeignKey("workspaces.id"), nullable=False)
    project_id = Column(String, nullable=True) # Linked to task systems
    category_id = Column(String, ForeignKey("accounting_accounts.id"), nullable=True)
    amount = Column(Numeric(precision=19, scale=4), nullable=False)
    period = Column(String, default="month") # "month", "quarter", "year"
    start_date = Column(DateTime(timezone=True), nullable=False)
    end_date = Column(DateTime(timezone=True), nullable=False)
    created_at = Column(DateTime(timezone=True), server_default=func.now())