import {Service} from '../../../di/src/decorator/Service.ts'

export type CanonicalResolver = (key: string) => any

export class DuplicateResolverKeyError extends Error {
    constructor(key: string) {
        super(`There is already a canonical resource with the scope ${key} registered.`)
    }
}

@Service()
export class Canon {
    protected resources: { [key: string]: any } = {}

    get(key: string): any {
        const key_parts = key.split('::')
        let desc_value = this.resources
        key_parts.forEach(part => {
            if ( typeof desc_value === 'function' ) {
                desc_value = desc_value(part)
            } else {
                desc_value = desc_value[part]
            }
        })
        return desc_value
    }

    register_resource(scope: string, resolver: CanonicalResolver) {
        if ( this.resources[scope] ) {
            throw new DuplicateResolverKeyError(scope)
        }

        this.resources[scope] = resolver
    }
}