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derived-value.ts
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derived-value.ts
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import type {
Field,
FieldOutput,
App,
Collection,
CollectionItem,
Context,
} from "../../../main";
import { HybridField, ValidationResult } from "../../../chip-types/field";
import isEmpty from "../../../utils/is-empty";
import { BadContext } from "../../../response/errors";
/*
todo: make the deriving_fn more type-safe by reading the types of the fields?
*/
export type DerivingFn<T extends Field> = (
context: Context,
item: CollectionItem,
...args: any[]
) => Promise<FieldOutput<T>>;
export default class DerivedValue<T extends Field> extends HybridField<T> {
typeName = "derived-value";
fields: string[];
deriving_fn: DerivingFn<T>;
private blessed_symbol = Symbol();
constructor(
base_field: T,
params: {
fields: string[];
deriving_fn: DerivingFn<T>;
}
) {
super(base_field);
if (typeof params.deriving_fn !== "function") {
throw new Error(
"Error: 'deriving_fn' param in name_and_surname derived-value field is not a function."
);
}
super.setParams(params);
this.fields = params.fields;
this.deriving_fn = params.deriving_fn;
if (typeof this.deriving_fn !== "function") {
throw new Error(
`'derived_fn' param in ${this.name} derived-value field is not a function.`
);
}
if (!Array.isArray(this.fields)) {
throw new Error(
`'fields' param in ${this.name} derived-value field is not an array.`
);
}
}
async init(app: App, collection: Collection): Promise<void> {
await super.init(app, collection);
for (const field of this.fields) {
if (!collection.fields[field]) {
throw new Error(
`Collection '${collection.name}' does not have a field named '${field}', which was passed to DerivedValue`
);
}
}
const not_matching_fields = this.fields.filter(
(field) => !Object.keys(this.collection.fields).includes(field)
);
if (not_matching_fields.length) {
throw new Error(
`Missing declaration for fields from derived-value params: ${not_matching_fields
.map((field) => `'${field}'`)
.join(", ")} in ${
this.collection.name
} collection. REMEMBER: 'derived-value' field must be declared *after* the fields it depends on.`
);
}
this.collection.on("before:create", async ([context, item]) => {
context.app.Logger.debug2(
"FIELD.DERIVED VALUE",
"Before:create handler"
);
const derived_fn_args = this.fields.map((field_name) => {
const value = item.body.getInput(field_name);
return value === undefined || value === null ? "" : value;
});
context.app.Logger.debug3(
"FIELD.DERIVED VALUE",
"Passing to derived_fn:",
derived_fn_args
);
const derived_value = await this.deriving_fn(
context,
item,
...derived_fn_args
);
item.set(this.name, derived_value, this.blessed_symbol);
});
this.collection.on("before:edit", async ([context, item]) => {
if (
!this.fields.some((field) =>
item.body.changed_fields.has(field)
)
) {
return;
}
context.app.Logger.debug("DERIVED VALUE", "Handling before:edit", {
item_body: item.body,
});
const derived_fn_args = await Promise.all(
this.fields.map((field_name) =>
item.getDecoded(field_name, context)
)
);
const derived_value = await this.deriving_fn(
context,
item,
...derived_fn_args
);
context.app.Logger.debug2("DERIVED VALUE", "Setting new value", {
[this.name]: derived_value,
});
item.set(this.name, derived_value, this.blessed_symbol);
});
}
async isProperValue(
context: Context,
new_value: Parameters<T["checkValue"]>[1],
old_value: Parameters<T["checkValue"]>[2],
new_value_blessing_token: symbol | null
): Promise<ValidationResult> {
if (
!isEmpty(new_value) &&
!context.is_super &&
!(new_value_blessing_token == this.blessed_symbol)
) {
throw new BadContext("This is a read-only field");
}
return this.virtual_field.checkValue(
context,
new_value,
old_value,
new_value_blessing_token
);
}
async hasIndex() {
return await this.virtual_field.hasIndex();
}
}

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