erDiagram
    HANA_SERVERS ||--o{ SITES : "default for HANA source system"
    SITES ||--o{ CENTRAL_SALES_RECORDS : stores
    SITES ||--o{ EXPORT_LOGS : writes
    SITES ||--o{ APP_EVENT_LOGS : logs
    SITES ||--o{ SAP_SOURCE_DEFINITIONS : configures
    SITES ||--o{ SAP_JOIN_DEFINITIONS : configures
    SITES ||--o{ SAP_FIELD_MAPPINGS : configures

    SOURCE_SYSTEM_DEFINITIONS {
        int Id PK
        string Code
        string DisplayName
        string ConnectionKind
        bool IsActive
        string CentralServiceUrl
        string CentralUsername
        string CentralPassword
    }

    HANA_SERVERS {
        int Id PK
        string SourceSystem
        string Name
        string Host
        int Port
        string DatabaseName
        bool UseSsl
        bool ValidateCertificate
        string AdditionalParams
    }

    SITES {
        int Id PK
        int HanaServerId FK
        string Schema
        string TSC
        string Land
        string SourceSystem
        string UsernameOverride
        string PasswordOverride
        string LocalExportFolderOverride
        string ManualImportFilePath
        datetime ManualImportLastUploadedAtUtc
        string SapServiceUrl
        string SapEntitySet
        string SapEntitySetsCache
        datetime SapEntitySetsRefreshedAtUtc
        bool IsActive
    }

    SHARE_POINT_CONFIGS {
        int Id PK
        string SiteUrl
        string ExportFolder
        string CentralExportFolder
        string TenantId
        string ClientId
        string ClientSecret
    }

    EXPORT_SETTINGS {
        int Id PK
        string DateFilter
        int TimerHour
        int TimerMinute
        bool TimerEnabled
        bool DebugLoggingEnabled
        string LocalSiteExportFolder
        string LocalConsolidatedExportFolder
    }

    FIELD_TRANSFORMATION_RULES {
        int Id PK
        string SourceSystem
        string SourceField
        string TargetField
        string TransformationType
        string RuleScope
        string Argument
        int SortOrder
        bool IsActive
    }

    SAP_SOURCE_DEFINITIONS {
        int Id PK
        int SiteId FK
        string Alias
        string EntitySet
        bool IsPrimary
        bool IsActive
        int SortOrder
    }

    SAP_JOIN_DEFINITIONS {
        int Id PK
        int SiteId FK
        string LeftAlias
        string RightAlias
        string LeftKeys
        string RightKeys
        string JoinType
        bool IsActive
        int SortOrder
    }

    SAP_FIELD_MAPPINGS {
        int Id PK
        int SiteId FK
        string TargetField
        string SourceExpression
        bool IsRequired
        bool IsActive
        int SortOrder
    }

    CENTRAL_SALES_RECORDS {
        int Id PK
        datetime StoredAtUtc
        int SiteId FK
        string SourceSystem
        datetime ExtractionDate
        string Tsc
        string InvoiceNumber
        int PositionOnInvoice
        string Material
        string Name
        string ProductGroup
        decimal Quantity
        string SupplierNumber
        string SupplierName
        string SupplierCountry
        string CustomerNumber
        string CustomerName
        string CustomerCountry
        string CustomerIndustry
        decimal StandardCost
        string StandardCostCurrency
        string PurchaseOrderNumber
        decimal SalesPriceValue
        string SalesCurrency
        string Incoterms2020
        string SalesResponsibleEmployee
        datetime InvoiceDate
        datetime OrderDate
        string Land
        string DocumentType
    }

    EXPORT_LOGS {
        int Id PK
        datetime Timestamp
        int SiteId FK
        string Land
        string TSC
        string Status
        int RowCount
        string ErrorMessage
        string FileName
        string FilePath
        double DurationSeconds
    }

    APP_EVENT_LOGS {
        int Id PK
        datetime Timestamp
        string Level
        string Category
        int SiteId FK
        string Land
        string Message
        string Details
    }

    CURRENCY_EXCHANGE_RATES {
        int Id PK
        string FromCurrency
        string ToCurrency
        decimal Rate
        datetime ValidFrom
        datetime ValidTo
        string Notes
        bool IsActive
    }