unit Myc.Data.Types.Arrays;

interface

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

type
    // Implements the array data type.
    TDataArrayType = class(TInterfacedObject, IDataType, IDataArrayType)
    private
        FElementType: IDataType;
        FEmptyValue: IDataArrayValue; // Cached empty array value for this type
        function GetElementType: IDataType;
        function GetName: String;
        function GetKind: TDataKind;
    public
        constructor Create(const AElementType: IDataType);
        function CreateValue(const AItems: array of IDataValue): IDataArrayValue;
    end;

implementation

uses
    System.SyncObjs,
    System.Rtti;

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

    // Optimized implementation for an array with 0 elements.
    TDataArrayValue0 = class(TInterfacedObject, IDataValue, IDataArrayValue)
    strict private
        class var
            FEmptyTValue: TValue; // Singleton TValue for an empty array
        class constructor CreateClass;
    private
        FArrayType: IDataArrayType;
        function GetDataType: IDataType;
        function GetAsString: string;
        function AsTValue: TValue;
        function GetElementCount: Integer;
        function GetItem(Idx: Integer): IDataValue;
    public
        constructor Create(const AArrayType: IDataArrayType);
    end;

    // Optimized implementation for an array with 1 element.
    TDataArrayValue1 = class(TInterfacedObject, IDataValue, IDataArrayValue)
    private
        FArrayType: IDataArrayType;
        FItem0: IDataValue;
        function GetDataType: IDataType;
        function GetAsString: string;
        function AsTValue: TValue;
        function GetElementCount: Integer;
        function GetItem(Idx: Integer): IDataValue;
    public
        constructor Create(const AArrayType: IDataArrayType; const AItems: array of IDataValue);
    end;

{ TDataArrayValue (generic implementation for N > 1 elements) }

constructor TDataArrayValue.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 TDataArrayValue.GetDataType: IDataType;
begin
    Result := FArrayType;
end;

function TDataArrayValue.GetAsString: string;
var
    sb: TStringBuilder;
    i: Integer;
begin
    sb := TStringBuilder.Create;
    try
        sb.Append('[');
        for i := 0 to High(FItems) do
        begin
            sb.Append(FItems[i].AsString);
            if (i < High(FItems)) then
                sb.Append(', ');
        end;
        sb.Append(']');
        Result := sb.ToString;
    finally
        sb.Free;
    end;
end;

function TDataArrayValue.AsTValue: TValue;
var
    tvalueArray: TArray<TValue>;
    i: Integer;
begin
    SetLength(tvalueArray, Length(FItems));
    for i := 0 to High(FItems) do
        tvalueArray[i] := FItems[i].AsTValue;
    Result := TValue.From<TArray<TValue>>(tvalueArray);
end;

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

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

{ TDataArrayValue0 }

class constructor TDataArrayValue0.CreateClass;
begin
    // Create a singleton TValue representing an empty dynamic array.
    FEmptyTValue := TValue.From<TArray<TValue>>([]);
end;

constructor TDataArrayValue0.Create(const AArrayType: IDataArrayType);
begin
    inherited Create;
    FArrayType := AArrayType;
end;

function TDataArrayValue0.GetAsString: string;
begin
    Result := '[]';
end;

function TDataArrayValue0.AsTValue: TValue;
begin
    Result := FEmptyTValue;
end;

function TDataArrayValue0.GetDataType: IDataType;
begin
    Result := FArrayType;
end;

function TDataArrayValue0.GetElementCount: Integer;
begin
    Result := 0;
end;

function TDataArrayValue0.GetItem(Idx: Integer): IDataValue;
begin
    raise EArgumentException.Create('Index out of bounds');
end;

{ TDataArrayValue1 }

constructor TDataArrayValue1.Create(const AArrayType: IDataArrayType; const AItems: array of IDataValue);
begin
    inherited Create;
    FArrayType := AArrayType;
    FItem0 := AItems[0];
end;

function TDataArrayValue1.GetAsString: string;
begin
    Result := '[' + FItem0.AsString + ']';
end;

function TDataArrayValue1.AsTValue: TValue;
var
    tvalueArray: TArray<TValue>;
begin
    SetLength(tvalueArray, 1);
    tvalueArray[0] := FItem0.AsTValue;
    Result := TValue.From<TArray<TValue>>(tvalueArray);
end;

function TDataArrayValue1.GetDataType: IDataType;
begin
    Result := FArrayType;
end;

function TDataArrayValue1.GetElementCount: Integer;
begin
    Result := 1;
end;

function TDataArrayValue1.GetItem(Idx: Integer): IDataValue;
begin
    case Idx of
        0: Result := FItem0;
    else
        raise EArgumentException.Create('Index out of bounds');
    end;
end;

{ TDataArrayType }

constructor TDataArrayType.Create(const AElementType: IDataType);
begin
    inherited Create;
    FElementType := AElementType;
    FEmptyValue := TDataArrayValue0.Create(Self);
end;

function TDataArrayType.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;

    // Use optimized implementations for arrays with 0 or 1 elements.
    case Length(AItems) of
        0: Result := FEmptyValue;
        1: Result := TDataArrayValue1.Create(Self, AItems);
    else
        // Use the generic implementation for arrays with more than 1 element.
        Result := TDataArrayValue.Create(Self, AItems);
    end;
end;

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

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

function TDataArrayType.GetKind: TDataKind;
begin
    Result := dkArray;
end;

end.