export const HEALTH_CHANNEL_STEPS = Object.freeze({
  IDLE: 'idle',
  AWAIT_ACTION_CHOICE: 'await_action_choice',
  AWAIT_METRIC_TYPE: 'await_metric_type',
  AWAIT_CONTEXT: 'await_context',
  AWAIT_VALUE: 'await_value',
  CONFIRM: 'confirm',
  COMMITTED: 'committed',
  EXITED: 'exited',
});

export const HEALTH_ACTIONS = Object.freeze({
  RECORD: 'record',
  ASSESS: 'assess',
  DOCUMENT: 'document',
  ARCHIVE: 'archive',
});

export const HEALTH_METRIC_SETS = Object.freeze([
  'blood_pressure',
  'heart_rate',
  'weight',
  'spo2',
  'temperature',
  'sleep',
  'symptom',
  'medication',
]);

const ACTION_BY_CHOICE = Object.freeze({
  1: HEALTH_ACTIONS.RECORD,
  2: HEALTH_ACTIONS.ASSESS,
  3: HEALTH_ACTIONS.DOCUMENT,
  4: HEALTH_ACTIONS.ARCHIVE,
});

const METRIC_BY_CHOICE = Object.freeze({
  1: 'blood_pressure',
  2: 'heart_rate',
  3: 'weight',
  4: 'spo2',
  5: 'temperature',
  6: 'sleep',
  7: 'symptom',
  8: 'medication',
});

export function createIdleHealthChannelState({ channel = 'h5' } = {}) {
  return {
    sessionKind: 'health',
    channel,
    step: HEALTH_CHANNEL_STEPS.IDLE,
    action: null,
    metricSet: null,
    context: null,
    pendingDraftId: null,
    lastPrompt: null,
  };
}

export function healthChannelUnexpectedPrompt(state) {
  if (state.step === HEALTH_CHANNEL_STEPS.AWAIT_VALUE) {
    if (state.metricSet === 'blood_pressure') {
      return [
        '当前正在录入「血压」。',
        '- 直接发送数值，如 137/82',
        '- 或拍照上传血压计读数',
        '- 回复「取消」放弃本次录入',
        '- 回复「0」退出健康通道',
      ].join('\n');
    }
    const labels = {
      heart_rate: '心率',
      weight: '体重',
      spo2: '血氧',
      temperature: '体温',
      sleep: '睡眠',
      symptom: '症状',
    };
    const label = labels[state.metricSet] ?? '指标';
    return `当前正在录入「${label}」。请按提示发送数值，或回复「取消」/「0」退出。`;
  }
  return '当前操作无法识别。请回复数字选择，或回复「0」退出健康通道。';
}

export function reduceHealthChannel(state, event) {
  const current = state ?? createIdleHealthChannelState();
  const type = String(event?.type ?? '').trim();

  if (type === 'exit' || event?.choice === 0 || event?.text === '0' || event?.text === '退出') {
    return {
      state: { ...createIdleHealthChannelState({ channel: current.channel }), step: HEALTH_CHANNEL_STEPS.EXITED },
      actions: [{ type: 'exit_channel' }],
    };
  }
  if (type === 'timeout') {
    return {
      state: { ...createIdleHealthChannelState({ channel: current.channel }), step: HEALTH_CHANNEL_STEPS.EXITED },
      actions: [{ type: 'timeout_exit' }],
    };
  }
  if (type === 'cancel' || event?.text === '取消') {
    return {
      state: createIdleHealthChannelState({ channel: current.channel }),
      actions: [{ type: 'discard_draft' }],
    };
  }

  if (current.step === HEALTH_CHANNEL_STEPS.IDLE) {
    if (type === 'select_action' && event.action === HEALTH_ACTIONS.RECORD) {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.AWAIT_METRIC_TYPE, action: HEALTH_ACTIONS.RECORD },
        actions: [{ type: 'prompt_metric_type' }],
      };
    }
    if (type === 'select_action' && event.action === HEALTH_ACTIONS.ASSESS) {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.IDLE, action: HEALTH_ACTIONS.ASSESS },
        actions: [{ type: 'run_assessment' }],
      };
    }
    if (type === 'select_action' && (event.action === HEALTH_ACTIONS.DOCUMENT || event.action === HEALTH_ACTIONS.ARCHIVE)) {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.IDLE, action: event.action },
        actions: [{ type: event.action === HEALTH_ACTIONS.DOCUMENT ? 'await_document' : 'show_archive' }],
      };
    }
    if (type === 'ambiguous') {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.AWAIT_ACTION_CHOICE },
        actions: [{ type: 'prompt_action_choice' }],
      };
    }
    if (type === 'unexpected') {
      return {
        state: current,
        actions: [{ type: 'prompt_unexpected', prompt: healthChannelUnexpectedPrompt(current) }],
      };
    }
  }

  if (current.step === HEALTH_CHANNEL_STEPS.AWAIT_ACTION_CHOICE && type === 'choose') {
    const action = ACTION_BY_CHOICE[Number(event.choice)];
    if (!action) {
      return {
        state: current,
        actions: [{ type: 'prompt_action_choice' }],
      };
    }
    return reduceHealthChannel(
      { ...current, step: HEALTH_CHANNEL_STEPS.IDLE },
      { type: 'select_action', action },
    );
  }

  if (current.step === HEALTH_CHANNEL_STEPS.AWAIT_METRIC_TYPE && (type === 'pick_metric' || type === 'choose')) {
    const metricSet = event.metricSet || METRIC_BY_CHOICE[Number(event.choice)];
    if (!HEALTH_METRIC_SETS.includes(metricSet)) {
      return {
        state: current,
        actions: [{ type: 'prompt_metric_type' }],
      };
    }
    const next = {
      ...current,
      metricSet,
      step: metricSet === 'blood_pressure' ? HEALTH_CHANNEL_STEPS.AWAIT_CONTEXT : HEALTH_CHANNEL_STEPS.AWAIT_VALUE,
    };
    return {
      state: next,
      actions: [{ type: next.step === HEALTH_CHANNEL_STEPS.AWAIT_CONTEXT ? 'prompt_context' : 'prompt_value' }],
    };
  }

  if (current.step === HEALTH_CHANNEL_STEPS.AWAIT_CONTEXT && type === 'pick_context') {
    return {
      state: {
        ...current,
        context: event.context || 'other',
        step: HEALTH_CHANNEL_STEPS.AWAIT_VALUE,
      },
      actions: [{ type: 'prompt_value' }],
    };
  }

  if (current.step === HEALTH_CHANNEL_STEPS.AWAIT_VALUE) {
    if (type === 'submit_value' || type === 'image' || type === 'voice') {
      return {
        state: {
          ...current,
          step: HEALTH_CHANNEL_STEPS.CONFIRM,
          pendingDraftId: event.draftId ?? current.pendingDraftId ?? 'draft',
        },
        actions: [{ type: 'prompt_confirm', draft: event.draft ?? null, requireConfirm: true }],
      };
    }
    if (type === 'unexpected') {
      return {
        state: current,
        actions: [{ type: 'prompt_unexpected', prompt: healthChannelUnexpectedPrompt(current) }],
      };
    }
  }

  if (current.step === HEALTH_CHANNEL_STEPS.CONFIRM) {
    if (type === 'commit') {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.COMMITTED },
        actions: [{ type: 'commit_observation', draftId: current.pendingDraftId }],
      };
    }
    if (type === 'revise') {
      return {
        state: { ...current, step: HEALTH_CHANNEL_STEPS.AWAIT_VALUE },
        actions: [{ type: 'prompt_value' }],
      };
    }
    if (type === 'discard') {
      return {
        state: createIdleHealthChannelState({ channel: current.channel }),
        actions: [{ type: 'discard_draft', draftId: current.pendingDraftId }],
      };
    }
  }

  if (current.step === HEALTH_CHANNEL_STEPS.COMMITTED && type === 'continue') {
    return {
      state: createIdleHealthChannelState({ channel: current.channel }),
      actions: [{ type: 'reset' }],
    };
  }

  return {
    state: current,
    actions: [{ type: 'noop' }],
  };
}