Checkbox

// Pseudocode walkthrough of the Foldkit integration points. Each labeled
// block below is an excerpt. Fit them into your own Model, init, Message,
// update, and view definitions.
import { Schema } from 'effect'
import type { HtmlBuilder } from 'foldkit/html'
import { defineMessageUnion } from 'foldkit/message'
import { modifyFields } from 'foldkit/struct'

import { Checkbox } from '@foldkit/ui'

// Store the checked state as a plain boolean field in your Model:
const Model = Schema.Struct({
  acceptedTerms: Schema.Boolean,
  // ...your other fields
})

// In your init function, start it unchecked:
const init = () => ({
  model: {
    acceptedTerms: false,
    // ...your other fields
  },
})

// A verb-first, past-tense Message carries the new checked state:

const Message = defineMessageUnion({
  ToggledTerms: { isChecked: Schema.Boolean },
})

// In the corresponding Message.match handler, store the value.
// This is the moment to fire analytics, validate a form, or push the value
// to a backend.
ToggledTerms: ({ isChecked }) => ({
  model: modifyFields(model, { acceptedTerms: () => isChecked }),
})

// Inside your view function, render the checkbox with Checkbox.view. It reads
// the checked state from your Model and calls onToggle with the new state.
const view = (model, h: HtmlBuilder<Message>) => {
  const checkboxView = (attributes: Checkbox.CheckboxAttributes<Message>) =>
    h.div(
      [h.Class('flex flex-col gap-1')],
      [
        h.div(
          [h.Class('flex items-center gap-2')],
          [
            h.button(
              [...attributes.checkbox, h.Class('h-5 w-5 rounded border')],
              model.acceptedTerms ? ['✓'] : [],
            ),
            h.label(
              [...attributes.label, h.Class('text-sm')],
              ['Accept terms and conditions'],
            ),
          ],
        ),
        h.p(
          [...attributes.description, h.Class('text-sm text-gray-500')],
          ['You agree to our Terms of Service.'],
        ),
      ],
    )

  return Checkbox.view(
    {
      id: 'accept-terms',
      isChecked: model.acceptedTerms,
      hasDescription: true,
      onToggle: isChecked => Message.ToggledTerms({ isChecked }),
      toView: checkboxView,
    },
    h,
  )
}

// Pseudocode walkthrough of the Foldkit integration points. Each labeled
// block below is an excerpt. Fit them into your own Model, init, Message,
// update, and view definitions.
import { Schema } from 'effect'
import type { HtmlBuilder } from 'foldkit/html'
import { defineMessageUnion } from 'foldkit/message'
import { modifyFields } from 'foldkit/struct'

import { Checkbox } from '@foldkit/ui'

// Store each child's checked state as a plain boolean field in your Model:
const Model = Schema.Struct({
  optionA: Schema.Boolean,
  optionB: Schema.Boolean,
  // ...your other fields
})

// In your init function, start each unchecked:
const init = () => ({
  model: {
    optionA: false,
    optionB: false,
    // ...your other fields
  },
})

// One Message per child, plus one for the "Select All" parent. Each carries
// the new checked state:

const Message = defineMessageUnion({
  ToggledSelectAll: { isChecked: Schema.Boolean },
  ToggledOptionA: { isChecked: Schema.Boolean },
  ToggledOptionB: { isChecked: Schema.Boolean },
})

// In the corresponding Message.match handler, toggling "Select All"
// writes the same value to every child:
ToggledSelectAll: ({ isChecked }) => ({
  model: modifyFields(model, {
    optionA: () => isChecked,
    optionB: () => isChecked,
  }),
})

// Inside your view function, compute the parent's checked and indeterminate
// state from the children and pass isIndeterminate straight to Checkbox.view:
const view = (model, h: HtmlBuilder<Message>) => {
  const isAllChecked = model.optionA && model.optionB
  const isNoneChecked = !model.optionA && !model.optionB
  const isIndeterminate = !isAllChecked && !isNoneChecked

  const resolveSelectAllMark = () => {
    if (isIndeterminate) {
      return ['—']
    } else if (isAllChecked) {
      return ['✓']
    } else {
      return []
    }
  }

  const selectAllView = (attributes: Checkbox.CheckboxAttributes<Message>) =>
    h.div(
      [h.Class('flex items-center gap-2')],
      [
        h.button(
          [...attributes.checkbox, h.Class('h-5 w-5 rounded border')],
          resolveSelectAllMark(),
        ),
        h.label(
          [...attributes.label, h.Class('text-sm')],
          ['All notifications'],
        ),
      ],
    )

  return Checkbox.view(
    {
      id: 'select-all',
      isChecked: isAllChecked,
      isIndeterminate,
      onToggle: isChecked => Message.ToggledSelectAll({ isChecked }),
      toView: selectAllView,
    },
    h,
  )
}