unit PM.Router;

{
  URL dispatcher. Mirrors the switch(true) pattern of api.php.
  Each handler unit registers its routes here. The Router itself owns no state.
}

interface

uses
  System.SysUtils, System.Classes, System.Generics.Collections,
  System.RegularExpressions,
  IdCustomHTTPServer;

type
  TRouteParams = TArray<string>;

  TRouteHandler = reference to procedure(
    ARequest: TIdHTTPRequestInfo;
    AResponse: TIdHTTPResponseInfo;
    const AParams: TRouteParams);

  TRoute = record
    Method: string;
    Pattern: string;           // regex; ^ and $ added automatically
    Regex: TRegEx;
    Handler: TRouteHandler;
  end;

  TPMRouter = class
  private
    FRoutes: TList<TRoute>;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Register(const AMethod, APattern: string;
      const AHandler: TRouteHandler);
    function DispatchRequest(ARequest: TIdHTTPRequestInfo;
      AResponse: TIdHTTPResponseInfo): Boolean;
  end;

var
  Router: TPMRouter;

implementation

constructor TPMRouter.Create;
begin
  inherited;
  FRoutes := TList<TRoute>.Create;
end;

destructor TPMRouter.Destroy;
begin
  FRoutes.Free;
  inherited;
end;

procedure TPMRouter.Register(const AMethod, APattern: string;
  const AHandler: TRouteHandler);
var
  R: TRoute;
begin
  R.Method := UpperCase(AMethod);
  R.Pattern := APattern;
  R.Regex := TRegEx.Create('^' + APattern + '$');
  R.Handler := AHandler;
  FRoutes.Add(R);
end;

function TPMRouter.DispatchRequest(ARequest: TIdHTTPRequestInfo;
  AResponse: TIdHTTPResponseInfo): Boolean;
var
  LRoute: TRoute;
  LMatch: TMatch;
  LParams: TRouteParams;
  I: Integer;
  LMethod, LPath: string;
begin
  Result := False;
  LMethod := UpperCase(ARequest.Command);
  LPath := ARequest.Document;
  for LRoute in FRoutes do
  begin
    if LRoute.Method <> LMethod then Continue;
    LMatch := LRoute.Regex.Match(LPath);
    if LMatch.Success then
    begin
      SetLength(LParams, LMatch.Groups.Count - 1);
      for I := 1 to LMatch.Groups.Count - 1 do
        LParams[I - 1] := LMatch.Groups[I].Value;
      LRoute.Handler(ARequest, AResponse, LParams);
      Exit(True);
    end;
  end;
end;

initialization
  Router := TPMRouter.Create;

finalization
  Router.Free;

end.