import { defineMetadata, getMetadata } from "muddle/metadata";
import type { FieldOptions } from "muddle/contracts/typegen/orm/field.ts";
import type { FieldDescriptor } from "muddle/contracts/typegen/orm/field.ts";

export const FIELD_METADATA_KEY = "muddle:orm:fields";

/** Converts a property name into the default column name. */
export function toColumnName(property: string): string {
	return property
		.replace(/([a-z0-9])([A-Z])/g, "$1_$2")
		.replace(/([A-Z]+)([A-Z][a-z])/g, "$1_$2")
		.toLowerCase();
}

/** Declares the column backing a property. */
export function Field<Value = any>(
	options: FieldOptions<Value>,
): PropertyDecorator {
	return (target, propertyKey) => {
		const constructor = target.constructor as object;
		const fields = getFields(constructor);
		const property = String(propertyKey);
		fields.set(property, {
			property,
			column: options.column ?? toColumnName(property),
			options,
		});
	};
}

/** Reads the fields declared on a model class. */
export function getFields(target: object): Map<string, FieldDescriptor> {
	const existing = getMetadata(FIELD_METADATA_KEY, target) as
		| Map<string, FieldDescriptor>
		| undefined;
	if (existing) return existing;
	const fields = new Map<string, FieldDescriptor>();
	defineMetadata(FIELD_METADATA_KEY, fields, target);
	return fields;
}