forms/forms.go

package forms

import (
	"bytes"
	"context"
	_ "embed"
	"html/template"
	"strconv"
)

/* ValidatorFunc defines a function for FormField data validation */
type ValidatorFunc func(*FormField, context.Context) error

/* ValidatorsList defines a list of ValidatorFunc */
type ValidatorsList []ValidatorFunc

/* A general purpose form  field struct */
type FormField struct {
	Name         string
	Error        []error
	Value        string
	Label        string
	Kind         string
	Placeholder  string
	Help         string
	Required     bool
	AutoFocus    bool
	Sticky       bool
	Checked      bool
	AutoComplete string
	Validators   ValidatorsList
}

/* AddError appends a new error message to the form field errors list */
func (f *FormField) AddError(err error) *FormField {
	f.Error = append(f.Error, err)
	return f
}

/* Add AddValidator appends a new validator to the form field validators list */
func (f *FormField) AddValidator(validator ValidatorFunc) *FormField {
	f.Validators = append(f.Validators, validator)
	return f
}

/* SetValidators configures validators list in form field */
func (f *FormField) SetValidators(validators ...ValidatorFunc) *FormField {
	for _, validator := range validators {
		f.AddValidator(validator)
	}
	return f
}

/* SetLabel configures form label */
func (f *FormField) SetLabel(label string) *FormField {
	f.Label = label
	return f
}

/* SetRequired marks FormField as mandatory */
func (f *FormField) SetRequired() *FormField {
	f.Required = true
	return f
}

/* SetAutoFocus gives focus to current FormField on page load  */
func (f *FormField) SetAutoFocus() *FormField {
	f.AutoFocus = true
	return f
}

/* SetKind specifies input field type */
func (f *FormField) SetKind(t string) *FormField {
	f.Kind = t
	return f
}

/* SetPlaceholder specified a placeholder property in Formfield */
func (f *FormField) SetPlaceholder(placeholder string) *FormField {
	f.Placeholder = placeholder
	return f
}

/* SetHelp specified a help message for current Formfield */
func (f *FormField) SetHelp(help string) *FormField {
	f.Help = help
	return f
}

/* SetAutoComplete sets the autocomplete flag for a field */
func (f *FormField) SetAutoComplete(on bool) *FormField {
	f.AutoComplete = "off"
	if on {
		f.AutoComplete = "on"
	}
	return f
}

/* GetString returns FormField.Value as string */
func (f *FormField) GetString() string {
	return f.Value
}

/* GetInt returns FormField.Value as int */
func (f FormField) GetInt() (v int, err error) {
	v, err = strconv.Atoi(f.Value)
	if err != nil {
		err = EInvalidIntValue
	}
	return
}

/* Int converts FormField.Value to integer value and ignores errors */
func (f *FormField) Int() int {
	if result, err := strconv.Atoi(f.Value); err == nil {
		return result
	}
	return 0
}

/* GetFloat returns FormField.Value as float */
func (f *FormField) GetFloat() (float64, error) {
	return strconv.ParseFloat(f.Value, 64)
}

/* Float converts FormField.Value to float and ignores errors */
func (f *FormField) Float() float64 {
	if result, err := strconv.ParseFloat(f.Value, 64); err == nil {
		return result
	}
	return 0.0
}

/* GetBool returns true if checkbox is selected, always returns nil error */
func (f *FormField) GetBool() (bool, error) {
	/* if box is checked, it sends a non-empty value */
	return len(f.Value) != 0, nil
}

/* Bool returns true if checkbox is selected, ignores errors */
func (f *FormField) Bool() bool {
	return len(f.Value) != 0
}

/* fieldsTemplateStr is a template to render FormField element in HTML format */
//go:embed fields.html
var fieldsTemplateStr string

/* must checks for compile/start up errors */
func must(r any, e error) any {
	if e != nil {
		panic(e)
	}
	return r
}

/* fieldsTemplate is compiled template to render FormField element in HTML format */
var fieldsTemplate = template.Must(
	template.New("FormField").Parse(fieldsTemplateStr),
)

/* HTML renders FormField element in html format */
func (f *FormField) HTML() template.HTML {
	var buffer bytes.Buffer
	if err := fieldsTemplate.ExecuteTemplate(&buffer, f.Kind, f); err == nil {
		return template.HTML(buffer.String())
	}
	return template.HTML("")
}