FORM_INPUT(3)                  RSX Framework Manual                  FORM_INPUT(3)

NAME
    form_input - Form input component contract and implementation

SYNOPSIS
    // Creating a custom input component (template method pattern)
    class My_Custom_Input extends Form_Input_Abstract {
        _get_value() {
            return this.$sid('input').val();
        }

        _set_value(value) {
            this.$sid('input').val(value || '');
        }

        on_ready() {
            this._mark_ready();

            const that = this;
            this.$sid('input').on('input', function() {
                const value = that.val();
                that.trigger('input', value);
                that.trigger('val', value);
            });
        }
    }

DESCRIPTION
    Form input components are the building blocks of RSX forms. They provide
    a consistent interface for getting and setting values, handling user
    interaction, and integrating with the form system.

    The base class (Form_Input_Abstract) implements a template method pattern
    that handles all common logic:
    - Pre-initialization value buffering
    - val() getter/setter implementation
    - Automatic trigger('val') on value changes
    - Applying buffered values when ready

    Concrete input classes only need to implement:
    - _get_value() - How to read the current value
    - _set_value(value) - How to write a value
    - on_ready() - Call _mark_ready() and setup event handlers

    Key difference from Laravel:
    - Laravel: Form inputs are standard HTML elements, values read via request
    - RSX: Form inputs are components with rich behavior and event system

    Unlike regular JQHTML components:
    - Input components have NO on_load() method
    - Input components do not use this.data (it's always empty)
    - Values are managed via the base class val() method
    - Templates render EMPTY elements (no value attributes)

TEMPLATE METHOD PATTERN

    The base class handles the complex logic, concrete classes provide simple
    hooks for getting and setting values.

    Base Class Provides:
        on_create()         Initializes _pending_value and _is_ready
        val()               Full getter/setter with buffering and events
        _mark_ready()       Apply buffered value, mark component ready
        _transform_value()  Default pass-through (override if needed)

    Concrete Class Implements:
        _get_value()        Return current DOM/component value (REQUIRED)
        _set_value(value)   Set DOM/component value (REQUIRED)
        _transform_value()  Transform buffered value for getter (OPTIONAL)
        on_ready()          Call _mark_ready(), setup events (REQUIRED)

    Benefits:
        - Cannot forget trigger('val') - base class handles it
        - Cannot forget buffering - base class handles it
        - Reduced boilerplate: ~10 lines instead of ~40
        - Consistent behavior across all inputs

MINIMAL IMPLEMENTATION

    class My_Input extends Form_Input_Abstract {
        _get_value() {
            return this.$sid('input').val();
        }

        _set_value(value) {
            this.$sid('input').val(value || '');
        }

        on_ready() {
            this._mark_ready();

            const that = this;
            this.$sid('input').on('input', function() {
                const value = that.val();
                that.trigger('input', value);
                that.trigger('val', value);
            });
        }
    }

    That's it. No on_create(), no val() method, no buffering logic.

VALUE TRANSFORMATION

    Some inputs need to transform the buffered value when returning it.
    Override _transform_value() for this:

    class Checkbox_Input extends Form_Input_Abstract {
        on_create() {
            super.on_create();
            this.checked_value = this.args.checked_value || '1';
            this.unchecked_value = this.args.unchecked_value || '0';
        }

        _get_value() {
            return this.$sid('input').prop('checked')
                ? this.checked_value
                : this.unchecked_value;
        }

        _set_value(value) {
            const should_check = (value === this.checked_value ||
                                  value === '1' || value === 1 || value === true);
            this.$sid('input').prop('checked', should_check);
        }

        _transform_value(value) {
            const should_check = (value === this.checked_value ||
                                  value === '1' || value === 1 || value === true);
            return should_check ? this.checked_value : this.unchecked_value;
        }

        on_ready() {
            this._mark_ready();
            // setup change handler...
        }
    }

ASYNC INITIALIZATION

    Some components initialize asynchronously (e.g., waiting for external
    libraries). Call _mark_ready() when actually ready, not at the start
    of on_ready().

    class Wysiwyg_Input extends Form_Input_Abstract {
        _get_value() {
            if (!this.quill) return '';
            return safe_html(this.quill.root.innerHTML);
        }

        _set_value(value) {
            if (value) {
                this.quill.root.innerHTML = value;
            }
        }

        _transform_value(value) {
            return safe_html(value);
        }

        on_ready() {
            const that = this;
            quill_ready(function() {
                that._initialize_quill();
                that._mark_ready();  // Called AFTER quill is ready
            });
        }
    }

EVENT SYSTEM

    Two events serve different purposes:

    'input' Event:
        Fires only on user interaction. Use for dependent fields, live search,
        or any logic that should respond to user changes but not programmatic
        population.

        this.sid('country').on('input', (component, value) => {
            this.reload_states(value);
        });

    'val' Event:
        Fires on ALL value changes. Because jqhtml triggers already-fired
        events when .on() is registered late, this provides immediate callback
        with the current value plus all future changes.

        this.sid('amount').on('val', (component, value) => {
            // Fires immediately with current value
            // Then fires on every subsequent change
            this.update_total(value);
        });

    Event Triggering:
        - Base class val() setter automatically triggers 'val'
        - Concrete classes trigger BOTH 'input' and 'val' on user interaction
        - Never trigger 'input' from the val() setter

PRE-INITIALIZATION

    Why Required:
        Forms call vals() during on_ready() to populate all inputs with data.
        Child input components may still be loading (e.g., Select_Input
        fetching options via Ajax). The base class buffers the value and
        applies it when _mark_ready() is called.

    Example Scenario:
        1. Form on_ready() calls this.vals(data)
        2. Select_Input is still loading options from server
        3. Form sets val('123') on the Select_Input
        4. Base class buffers '123' in _pending_value
        5. Select_Input on_ready() calls _mark_ready()
        6. Base class applies buffered '123' via _set_value()

    The base class handles all this automatically. Concrete classes just
    need to implement _get_value() and _set_value().

BUILT-IN INPUTS

    Text_Input
        Text, email, url, tel, number, textarea inputs.
        REQUIRES $max_length argument for character limits.

        <Text_Input $name="email" $max_length=User_Model.field_length('email') />
        <Text_Input $name="notes" $type="textarea" $max_length=-1 $rows="5" />

        $max_length values:
        - Positive number: Sets HTML maxlength attribute
        - -1: Unlimited (no maxlength applied)
        - Undefined: Console error with guidance

        Use Model.field_length('column') for database-driven limits.
        Subclasses (Phone_Text_Input, Currency_Input) are exempt.

    Select_Input
        Dropdown with static options.
        <Select_Input $options="<%= JSON.stringify(options) %>" />

    Select_Ajax_Input
        Dropdown that loads options via Ajax.
        <Select_Ajax_Input $controller="Controller" $method="get_options" />

    Checkbox_Input
        Boolean checkbox input.
        <Checkbox_Input $label="I agree to terms" />

    Checkbox_Multiselect
        Multiple checkbox selection as array value.

    Wysiwyg_Input
        Rich text editor (Quill-based).

EXTENDING OTHER INPUTS

    When extending another input (e.g., Select_Ajax_Input extends Select_Input),
    call super methods appropriately:

    class Select_Ajax_Input extends Select_Input {
        async on_load() {
            this.data.select_values = await Controller.get_options();
        }

        on_ready() {
            // Parent sets up TomSelect and calls _mark_ready()
            super.on_ready();
        }

        // _get_value() and _set_value() inherited from Select_Input
    }

CREATING CUSTOM INPUTS

    1. Create JavaScript class extending Form_Input_Abstract
    2. Create jqhtml template (NO class="Widget" needed)
    3. Implement _get_value() and _set_value()
    4. Implement on_ready() calling _mark_ready() and setting up events

    Template Example:
        <Define:My_Custom_Input>
            <div class="my-input-wrapper">
                <input type="text" $sid="input" class="form-control" />
            </div>
        </Define:My_Custom_Input>

    JavaScript Example:
        class My_Custom_Input extends Form_Input_Abstract {
            _get_value() {
                return this.$sid('input').val();
            }

            _set_value(value) {
                this.$sid('input').val(value || '');
            }

            on_ready() {
                this._mark_ready();

                const that = this;
                this.$sid('input').on('input', function() {
                    const val = that.val();
                    that.trigger('input', val);
                    that.trigger('val', val);
                });
            }
        }

COMMON MISTAKES

    Implementing val():
        Don't override val(). Implement _get_value() and _set_value() instead.
        The base class handles all the buffering and event logic.

    Forgetting _mark_ready():
        Must call in on_ready() to apply buffered values and mark ready.

    Calling _mark_ready() too early:
        For async initialization, wait until actually ready before calling.

    Using this.data:
        Input components have no on_load(), so this.data is always {}.
        Never use this.data.value or similar patterns.

    Adding class="Widget":
        No longer required. The .Form_Input_Abstract class is automatic.

    Not triggering both events:
        User interaction must trigger both 'input' and 'val'.

    Setting value in template:
        Templates must render empty. Forms populate via val().

TROUBLESHOOTING

    Value Not Appearing:
        - Check _set_value() actually sets DOM element
        - Verify _mark_ready() is called in on_ready()
        - Confirm template has $sid="input" or equivalent

    Events Not Firing:
        - Verify on_ready() sets up DOM event listeners
        - Confirm both 'input' and 'val' triggered on user interaction
        - Base class handles trigger('val') in setter automatically

    Form Not Finding Input:
        - Input must extend Form_Input_Abstract
        - Check for typos in class name
        - Verify component is inside Rsx_Form

    Pre-Init Values Lost:
        - Verify _mark_ready() is called in on_ready()
        - For async init, call _mark_ready() after initialization completes
        - Check _get_value() returns correct value

SEE ALSO
    jqhtml(3) - Component lifecycle and templates
    form_conventions(3) - Form patterns and data flow
    spa(3) - SPA action forms
    rsx/theme/components/inputs/CLAUDE.md - Implementation details