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// Copyright 2024 New Vector Ltd.
// Copyright 2022-2024 The Matrix.org Foundation C.I.C.
//
// SPDX-License-Identifier: AGPL-3.0-only
// Please see LICENSE in the repository root for full details.
use std::{collections::HashMap, hash::Hash};
use serde::{Deserialize, Serialize};
/// A trait which should be used for form field enums
pub trait FormField: Copy + Hash + PartialEq + Eq + Serialize + for<'de> Deserialize<'de> {
/// Return false for fields where values should not be kept (e.g. password
/// fields)
fn keep(&self) -> bool;
}
/// An error on a form field
#[derive(Debug, Serialize)]
#[serde(rename_all = "snake_case", tag = "kind")]
pub enum FieldError {
/// A required field is missing
Required,
/// An unspecified error on the field
Unspecified,
/// Invalid value for this field
Invalid,
/// The password confirmation doesn't match the password
PasswordMismatch,
/// That value already exists
Exists,
/// Denied by the policy
Policy {
/// Message for this policy violation
message: String,
},
}
/// An error on the whole form
#[derive(Debug, Serialize)]
#[serde(rename_all = "snake_case", tag = "kind")]
pub enum FormError {
/// The given credentials are not valid
InvalidCredentials,
/// Password fields don't match
PasswordMismatch,
/// There was an internal error
Internal,
/// Rate limit exceeded
RateLimitExceeded,
/// Denied by the policy
Policy {
/// Message for this policy violation
message: String,
},
/// Failed to validate CAPTCHA
Captcha,
}
#[derive(Debug, Default, Serialize)]
struct FieldState {
value: Option<String>,
errors: Vec<FieldError>,
}
/// The state of a form and its fields
#[derive(Debug, Serialize)]
pub struct FormState<K: Hash + Eq> {
fields: HashMap<K, FieldState>,
errors: Vec<FormError>,
#[serde(skip)]
has_errors: bool,
}
impl<K: Hash + Eq> Default for FormState<K> {
fn default() -> Self {
FormState {
fields: HashMap::default(),
errors: Vec::default(),
has_errors: false,
}
}
}
#[derive(Deserialize, PartialEq, Eq, Hash)]
#[serde(untagged)]
enum KeyOrOther<K> {
Key(K),
Other(String),
}
impl<K> KeyOrOther<K> {
fn key(self) -> Option<K> {
match self {
Self::Key(key) => Some(key),
Self::Other(_) => None,
}
}
}
impl<K: FormField> FormState<K> {
/// Generate a [`FormState`] out of a form
///
/// # Panics
///
/// If the form fails to serialize, or the form field keys fail to
/// deserialize
pub fn from_form<F: Serialize>(form: &F) -> Self {
let form = serde_json::to_value(form).unwrap();
let fields: HashMap<KeyOrOther<K>, Option<String>> = serde_json::from_value(form).unwrap();
let fields = fields
.into_iter()
.filter_map(|(key, value)| {
let key = key.key()?;
let value = key.keep().then_some(value).flatten();
let field = FieldState {
value,
errors: Vec::new(),
};
Some((key, field))
})
.collect();
FormState {
fields,
errors: Vec::new(),
has_errors: false,
}
}
/// Add an error on a form field
pub fn add_error_on_field(&mut self, field: K, error: FieldError) {
self.fields.entry(field).or_default().errors.push(error);
self.has_errors = true;
}
/// Add an error on a form field
#[must_use]
pub fn with_error_on_field(mut self, field: K, error: FieldError) -> Self {
self.add_error_on_field(field, error);
self
}
/// Add an error on the form
pub fn add_error_on_form(&mut self, error: FormError) {
self.errors.push(error);
self.has_errors = true;
}
/// Add an error on the form
#[must_use]
pub fn with_error_on_form(mut self, error: FormError) -> Self {
self.add_error_on_form(error);
self
}
/// Set a value on the form
pub fn set_value(&mut self, field: K, value: Option<String>) {
self.fields.entry(field).or_default().value = value;
}
/// Checks if a field contains a value
pub fn has_value(&self, field: K) -> bool {
self.fields.get(&field).is_some_and(|f| f.value.is_some())
}
/// Returns `true` if the form has no error attached to it
#[must_use]
pub fn is_valid(&self) -> bool {
!self.has_errors
}
}
/// Utility trait to help creating [`FormState`] out of a form
pub trait ToFormState: Serialize {
/// The enum used for field names
type Field: FormField;
/// Generate a [`FormState`] out of [`Self`]
///
/// # Panics
///
/// If the form fails to serialize or [`Self::Field`] fails to deserialize
fn to_form_state(&self) -> FormState<Self::Field> {
FormState::from_form(&self)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[derive(Serialize)]
struct TestForm {
foo: String,
bar: String,
}
#[derive(Serialize, Deserialize, Debug, Clone, Copy, Hash, PartialEq, Eq)]
#[serde(rename_all = "snake_case")]
enum TestFormField {
Foo,
Bar,
}
impl FormField for TestFormField {
fn keep(&self) -> bool {
match self {
Self::Foo => true,
Self::Bar => false,
}
}
}
impl ToFormState for TestForm {
type Field = TestFormField;
}
#[test]
fn form_state_serialization() {
let form = TestForm {
foo: "john".to_owned(),
bar: "hunter2".to_owned(),
};
let state = form.to_form_state();
let state = serde_json::to_value(state).unwrap();
assert_eq!(
state,
serde_json::json!({
"errors": [],
"fields": {
"foo": {
"errors": [],
"value": "john",
},
"bar": {
"errors": [],
"value": null
},
}
})
);
let form = TestForm {
foo: String::new(),
bar: String::new(),
};
let state = form
.to_form_state()
.with_error_on_field(TestFormField::Foo, FieldError::Required)
.with_error_on_field(TestFormField::Bar, FieldError::Required)
.with_error_on_form(FormError::InvalidCredentials);
let state = serde_json::to_value(state).unwrap();
assert_eq!(
state,
serde_json::json!({
"errors": [{"kind": "invalid_credentials"}],
"fields": {
"foo": {
"errors": [{"kind": "required"}],
"value": "",
},
"bar": {
"errors": [{"kind": "required"}],
"value": null
},
}
})
);
}
}