A Flutter voice copilot case study, where the chat
is voice.

// gf_voice_copilot.dart — GetWidget OSS Flutter package
//
// Drop the voice copilot into any Flutter scaffold. Mic-permission
// UX, the partial transcript chip, the animated waveform, and
// barge-in handling all live in the widget. The host wires the
// two callbacks: partial transcript (during) + suggestions (after
// the function call resolves).

import 'package:flutter/material.dart';

class VoiceCopilotConfig {
  /// First-token latency budget. The widget surfaces a degraded
  /// affordance when the model exceeds it twice in a row.
  final int firstTokenBudgetMs;

  /// Time to wait before falling from WebRTC to chunked HTTP + Whisper.
  final Duration fallbackToHttpAfter;

  /// Honour barge-in (tap-to-cancel mid-response).
  final bool bargeIn;

  const VoiceCopilotConfig({
    this.firstTokenBudgetMs = 600,
    this.fallbackToHttpAfter = const Duration(seconds: 2),
    this.bargeIn = true,
  });
}

class ProductSuggestion {
  final String sku;
  final String title;
  final num priceCents;
  const ProductSuggestion({
    required this.sku,
    required this.title,
    required this.priceCents,
  });
}

typedef OnSuggestions   = void Function(List<ProductSuggestion>);
typedef OnTranscript    = void Function(String partial);
typedef OnHandoff       = void Function(String intent);

class GFVoiceCopilot extends StatefulWidget {
  /// Scopes the function-call surface to this catalog (per-store SKU set).
  final String catalogId;

  /// Latency + fallback behaviour.
  final VoiceCopilotConfig config;

  /// Fires repeatedly as the model surfaces partial transcript.
  final OnTranscript onPartialTranscript;

  /// Fires once per function-call response with the suggestion list.
  final OnSuggestions onSuggestions;

  /// Fires when the agent classifies the intent as out-of-scope
  /// (returns, support, account questions). The host should
  /// navigate to a chat or human surface here.
  final OnHandoff onHandoff;

  const GFVoiceCopilot({
    super.key,
    required this.catalogId,
    required this.onPartialTranscript,
    required this.onSuggestions,
    required this.onHandoff,
    this.config = const VoiceCopilotConfig(),
  });

  @override
  State<GFVoiceCopilot> createState() => _GFVoiceCopilotState();
}