books/backend/Books.Api/Database/Migrations/011_Customers.sql

-- 011_Customers.sql
-- Creates customer read model tables and number series for invoicing support
-- Supports B2B (business with CVR) and B2C (private) customers
-- Each customer gets a sub-ledger account under 1900 Debitorer

-- Customer read models
CREATE TABLE IF NOT EXISTS customer_read_models (
    -- EventFlow standard columns
    aggregate_id VARCHAR(255) PRIMARY KEY,
    create_time TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_time TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    last_aggregate_sequence_number INT NOT NULL DEFAULT 1,

    -- Business columns (snake_case)
    company_id VARCHAR(255) NOT NULL,
    customer_number VARCHAR(20) NOT NULL,
    customer_type VARCHAR(20) NOT NULL,  -- 'Business' or 'Private'
    name VARCHAR(255) NOT NULL,
    cvr VARCHAR(8),  -- Required for Business, optional for Private
    address VARCHAR(500),
    postal_code VARCHAR(10),
    city VARCHAR(100),
    country VARCHAR(2) NOT NULL DEFAULT 'DK',
    email VARCHAR(255),
    phone VARCHAR(50),
    payment_terms_days INT NOT NULL DEFAULT 30,
    default_revenue_account_id VARCHAR(255),
    sub_ledger_account_id VARCHAR(255) NOT NULL,  -- Auto-created 1900-XXXX account
    is_active BOOLEAN NOT NULL DEFAULT TRUE,

    CONSTRAINT fk_customer_company
        FOREIGN KEY (company_id) REFERENCES company_read_models(aggregate_id) ON DELETE CASCADE,
    CONSTRAINT chk_customer_type
        CHECK (customer_type IN ('Business', 'Private')),
    CONSTRAINT chk_payment_terms
        CHECK (payment_terms_days >= 0 AND payment_terms_days <= 365)
);

-- Unique customer number per company
CREATE UNIQUE INDEX IF NOT EXISTS idx_customer_number
    ON customer_read_models(company_id, customer_number);

-- Lookup by company
CREATE INDEX IF NOT EXISTS idx_customer_company
    ON customer_read_models(company_id);

-- Lookup by CVR (for B2B customers)
CREATE INDEX IF NOT EXISTS idx_customer_cvr
    ON customer_read_models(cvr) WHERE cvr IS NOT NULL;

-- Search by name
CREATE INDEX IF NOT EXISTS idx_customer_name
    ON customer_read_models(company_id, name);

-- Filter active customers
CREATE INDEX IF NOT EXISTS idx_customer_active
    ON customer_read_models(company_id, is_active) WHERE is_active = TRUE;

-- Number series for sequential numbering (customers, invoices, credit notes)
-- Uses atomic UPSERT for thread-safe number generation
CREATE TABLE IF NOT EXISTS number_series (
    id SERIAL PRIMARY KEY,
    company_id VARCHAR(255) NOT NULL,
    sequence_key VARCHAR(100) NOT NULL,  -- e.g., 'customer', 'invoice-2024', 'creditnote-2024'
    last_number INT NOT NULL DEFAULT 0,
    prefix VARCHAR(20),  -- e.g., 'INV-2024-', 'CN-2024-', ''
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),

    UNIQUE(company_id, sequence_key),
    CONSTRAINT fk_number_series_company
        FOREIGN KEY (company_id) REFERENCES company_read_models(aggregate_id) ON DELETE CASCADE
);

CREATE INDEX IF NOT EXISTS idx_number_series_company
    ON number_series(company_id);

-- Comments for documentation
COMMENT ON TABLE customer_read_models IS 'Customer master data supporting B2B and B2C customers';
COMMENT ON COLUMN customer_read_models.customer_type IS 'Business (requires CVR) or Private (no CVR required)';
COMMENT ON COLUMN customer_read_models.sub_ledger_account_id IS 'Auto-created sub-ledger account (1900-XXXX) for customer receivables';
COMMENT ON COLUMN customer_read_models.payment_terms_days IS 'Default payment terms in days, used to calculate invoice due dates';

COMMENT ON TABLE number_series IS 'Sequential number generation for customers, invoices, and credit notes (Momsloven §52)';
COMMENT ON COLUMN number_series.sequence_key IS 'Identifies the sequence: customer, invoice-YYYY, creditnote-YYYY';