generateHtml function Null safety

String generateHtml(
  1. {required String sessionPublicKey,
  2. required String callbackScheme,
  3. required String callbackPath,
  4. Uri? authUri}
)

Implementation

String generateHtml(
    {required String sessionPublicKey,
    required String callbackScheme,
    required String callbackPath,
    Uri? authUri}) {
  final withHash = authUri != null
      ? authUri.toString()
      : Uri.parse(IDENTITY_PROVIDER_DEFAULT + '/' + IDENTITY_PROVIDER_ENDPOINT).toString();

  return """
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Grant Access to Flutter</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <style>
    html, body { margin: 0; padding: 0; }
    main {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      font-family: -apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol;
    }
    #icon {
      font-size: 96pt;
    }
    #text {
      padding: 2em;
      max-width: 260px;
      text-align: center;
    }
    .text {
      padding: 2em;
      max-width: 260px;
      text-align: center;
    }
    #button a {
      display: inline-block;
      padding: 6px 12px;
      color: white;
      border: 1px solid rgba(27,31,35,.2);
      border-radius: 3px;
      background-image: linear-gradient(-180deg, #34d058 0%, #22863a 90%);
      text-decoration: none;
      font-size: 14px;
      font-weight: 600;
    }
    #button a:active {
      background-color: #279f43;
      background-image: none;
    }
  </style>

</head>
<body>
  <main>
    <div id="icon">&#x1F3C7;</div>
    <div id="text">You are being redirected to</div>
    <div class="text">$withHash...</div>
    <div id="button" onclick="getValue()"><a>Click To Continue</a></div>
  </main>
  <script>
    var idpWindow;

    const toHex = arr => Array.from(arr, i => i.toString(16).padStart(2, "0")).join("");
    const fromHexString = hexString => new Uint8Array(hexString.match(/.{1,2}/g).map(byte => parseInt(byte, 16)));

    function getValue() {
      idpWindow = window.open('$withHash', 'idpWindow');
      if (idpWindow != undefined) {
        var listener = window.addEventListener('message', function (event) {
          var message = event.data;
          switch (message.kind) {
            case 'authorize-ready': {
              // IDP is ready. Send a message to request authorization.
              var request = {
                kind: 'authorize-client',
                sessionPublicKey: fromHexString('$sessionPublicKey'),
                maxTimeToLive: undefined,
              };

              idpWindow.postMessage(request, '$withHash');
              break;
            }
            case 'authorize-client-success':
              idpWindow.close();
              console.log(message);
              const { userPublicKey, delegations } = message;

              const newDelegations = delegations.map((d) => {
                const { pubkey, expiration } = d.delegation;
                return {
                  delegation: {
                    pubkey: toHex(pubkey),
                    expiration: expiration.toString(),
                  },
                  signature: toHex(d.signature),
                };
              });

              const newUserPublicKey = toHex(userPublicKey);

              const data = {
                delegations: newDelegations,
                publicKey: newUserPublicKey,
              };
              const json = JSON.stringify(data);

              window.removeEventListener('message', listener);
              window.location.href = '$callbackScheme://$callbackPath?success=true&&json=' + json;
              break;
            case 'authorize-client-failure':
              idpWindow.close();
              window.removeEventListener('message', listener);
              window.location.href =
                '$callbackScheme://$callbackPath?success=false&&json=' + message.text;
              break;
            default:
              break;
          }
        });
      }
    }
  </script>
</body>

</html>
""";
}