A recursive schema for building conditions within Sanity.io Condition functions must be implemented as separate input components and handled accordingly, but the basic structure is present.

sanityConditions.ts

export const conditionFunction = {
  title: "Condition function",
  name: "conditionFunction",
  type: "object",
  fields: [
    {
      title: "Function name",
      name: "name",
      type: "string",
      description: "The type of condition",
      options: {
        list: [
          {
            title: "Existence",
            value: "existence"
          },
          {
            title: "Equality",
            value: "equality"
          }
        ]
      },
      validation: (rule) => rule.required()
    },
    {
      title: "Options",
      name: "options",
      type: "string",
      description: "JSON representation of the condition options."
    }
  ]
}

export const conditionGroup = {
  title: "Condition group",
  name: "conditionGroup",
  type: "object",
  fields: [
    {
      title: "Relation",
      name: "relation",
      type: "string",
      description:
        'Choose whether any or all of the conditions within this group must be met. If not specified "All" is used',
      options: {
        list: [
          {
            title: "All (default)",
            value: "all"
          },
          {
            title: "Any",
            value: "any"
          }
        ]
      }
    },
    {
      title: "Conditions",
      name: "conditions",
      type: "array",
      of: [
        {
          title: "Nested condition group",
          name: "subConditionGroup",
          type: "conditionGroup"
        },
        {
          title: "Condition function",
          name: "conditionFn",
          type: "conditionFunction"
        }
      ]
    }
  ],
  preview: {
    select: {
      relation: "relation"
    },
    prepare: ({ relation = "" }) => ({
      title: "Condition group",
      subtitle: relation
    })
  }
}

export const condition = {
  title: "Condition",
  name: "condition",
  type: "object",
  fields: [
    {
      title: "Item",
      name: "onItem",
      type: "string",
      description: "Reference to the item in the form this condition will apply to.",
      validation: (rule) => rule.required()
    },
    {
      title: "Conditions",
      name: "conditions",
      type: "conditionGroup"
    }
  ]
}