unit Myc.Data.Types.Arrays;

interface

uses
    System.Generics.Collections,
    System.SysUtils,
    Myc.Data.Types;

type
    // An interface helper for IDataArrayValue.
    TArrayValue = record
    private
        FArrayValue: IDataArrayValue;
        function GetElementCount: Integer; inline;
        function GetItem(Idx: Integer): TDataValue; inline;
    public
        constructor Create(const AArrayValue: IDataArrayValue);

        class operator Implicit(const A: IDataArrayValue): TArrayValue; overload;
        class operator Implicit(const A: TArrayValue): IDataArrayValue; overload;

        property ElementCount: Integer read GetElementCount;
        property Items[Idx: Integer]: TDataValue read GetItem; default;
    end;

    // An interface helper for IDataArrayType.
    TArrayType = record
    private
        FArrayType: IDataArrayType;
        function GetElementType: TDataType; inline;
        function GetName: String; inline;
    public
        constructor Create(const AArrayType: IDataArrayType);

        class operator Implicit(const A: IDataArrayType): TArrayType; overload;
        class operator Implicit(const A: TArrayType): IDataArrayType; overload;

        function CreateValue(const AItems: array of IDataValue): TArrayValue;

        property Name: String read GetName;
        property ElementType: TDataType read GetElementType;
    end;

    TDataValueHelper = record helper for TDataValue
    public
        function AsArray: TArrayValue;
    end;

    TDataTypeHelper = record helper for TDataType
    public
        function AsArray: TArrayType;
    end;

    // Public factory for creating and caching array types.
    TArrayTypes = record
    strict private
        class var
            FRegistry: TDictionary<IDataType, IDataArrayType>;
        class constructor CreateClass;
        class destructor DestroyClass;
    public
        class function GetType(const AElementType: TDataType): TArrayType; static;
    end;

implementation

uses
    System.SyncObjs;

type
    {fwd}
    TImplDataArrayType = class;

    // Implements the array data value.
    TImplDataArrayValue = class(TInterfacedObject, IDataValue, IDataArrayValue)
    private
        FArrayType: IDataArrayType;
        FItems: TArray<IDataValue>;
        function GetDataType: IDataType;
        function GetElementCount: Integer;
        function GetItem(Idx: Integer): IDataValue;
    public
        constructor Create(const AArrayType: IDataArrayType; const AItems: array of IDataValue);
    end;

    // Implements the array data type.
    TImplDataArrayType = class(TInterfacedObject, IDataType, IDataArrayType)
    private
        FElementType: IDataType;
        function GetElementType: IDataType;
        function GetName: String;
    public
        constructor Create(const AElementType: IDataType);
        function CreateValue(const AItems: array of IDataValue): IDataArrayValue;
    end;

{ TArrayValue }

constructor TArrayValue.Create(const AArrayValue: IDataArrayValue);
begin
    FArrayValue := AArrayValue;
end;

function TArrayValue.GetElementCount: Integer;
begin
    if Assigned(FArrayValue) then
        Result := FArrayValue.ElementCount
    else
        Result := 0;
end;

function TArrayValue.GetItem(Idx: Integer): TDataValue;
begin
    if Assigned(FArrayValue) then
        Result := FArrayValue.Items[Idx]
    else
        Result := TDataValue.Create(nil);
end;

class operator TArrayValue.Implicit(const A: TArrayValue): IDataArrayValue;
begin
    Result := A.FArrayValue;
end;

class operator TArrayValue.Implicit(const A: IDataArrayValue): TArrayValue;
begin
    Result.FArrayValue := A;
end;

{ TArrayType }

constructor TArrayType.Create(const AArrayType: IDataArrayType);
begin
    FArrayType := AArrayType;
end;

function TArrayType.CreateValue(const AItems: array of IDataValue): TArrayValue;
begin
    if Assigned(FArrayType) then
        Result := FArrayType.CreateValue(AItems)
    else
        raise EAccessViolation.Create('Cannot create value from a nil array type.');
end;

function TArrayType.GetElementType: TDataType;
begin
    if Assigned(FArrayType) then
        Result := FArrayType.ElementType
    else
        Result := TDataType.Create(nil);
end;

function TArrayType.GetName: String;
begin
    if Assigned(FArrayType) then
        Result := FArrayType.Name
    else
        Result := '';
end;

class operator TArrayType.Implicit(const A: TArrayType): IDataArrayType;
begin
    Result := A.FArrayType;
end;

class operator TArrayType.Implicit(const A: IDataArrayType): TArrayType;
begin
    Result.FArrayType := A;
end;

{ TImplDataArrayValue }

constructor TImplDataArrayValue.Create(const AArrayType: IDataArrayType; const AItems: array of IDataValue);
var
    i: Integer;
begin
    inherited Create;
    FArrayType := AArrayType;
    SetLength(FItems, Length(AItems));
    for i := 0 to High(AItems) do
        FItems[i] := AItems[i];
end;

function TImplDataArrayValue.GetDataType: IDataType;
begin
    Result := FArrayType;
end;

function TImplDataArrayValue.GetElementCount: Integer;
begin
    Result := Length(FItems);
end;

function TImplDataArrayValue.GetItem(Idx: Integer): IDataValue;
begin
    Result := FItems[Idx];
end;

{ TImplDataArrayType }

constructor TImplDataArrayType.Create(const AElementType: IDataType);
begin
    inherited Create;
    FElementType := AElementType;
end;

function TImplDataArrayType.CreateValue(const AItems: array of IDataValue): IDataArrayValue;
var
    item: IDataValue;
    i: Integer;
begin
    // Validate that all items match the element type of this array type.
    i := 0;
    for item in AItems do
    begin
        if (item.DataType <> FElementType) then
            raise EArgumentException.CreateFmt(
                'Invalid data type for item at index %d. Expected ''%s'', but got ''%s''.',
                [i, FElementType.Name, item.DataType.Name]);
        inc(i);
    end;
    Result := TImplDataArrayValue.Create(Self, AItems);
end;

function TImplDataArrayType.GetElementType: IDataType;
begin
    Result := FElementType;
end;

function TImplDataArrayType.GetName: String;
begin
    Result := Format('Array<%s>', [FElementType.Name]);
end;

{ TDataValueHelper }

function TDataValueHelper.AsArray: TArrayValue;
begin
    Result := Self.DataValue as IDataArrayValue;
end;

{ TDataTypeHelper }

function TDataTypeHelper.AsArray: TArrayType;
begin
    Result := Self.DataType as IDataArrayType;
end;

{ TArrayTypes }

class constructor TArrayTypes.CreateClass;
begin
    // IDataType interface keys work out-of-the-box with the default comparer.
    FRegistry := TDictionary<IDataType, IDataArrayType>.Create;
end;

class destructor TArrayTypes.DestroyClass;
begin
    FRegistry.Free;
end;

class function TArrayTypes.GetType(const AElementType: TDataType): TArrayType;
var
    arrayTypeItf: IDataArrayType;
    elementTypeItf: IDataType;
begin
    elementTypeItf := AElementType.DataType; // Get underlying interface from helper
    if not Assigned(elementTypeItf) then
        raise EArgumentException.Create('Cannot create an array type with a nil element type.');

    TMonitor.Enter(FRegistry);
    try
        if not FRegistry.TryGetValue(elementTypeItf, arrayTypeItf) then
        begin
            arrayTypeItf := TImplDataArrayType.Create(elementTypeItf);
            FRegistry.Add(elementTypeItf, arrayTypeItf);
        end;
    finally
        TMonitor.Exit(FRegistry);
    end;
    Result := arrayTypeItf;
end;

end.