daton/di/src/Container.ts

import AbstractFactory from './factory/AbstractFactory.ts'
import Factory from './factory/Factory.ts'
import SingletonFactory from './factory/SingletonFactory.ts'
import FunctionFactory from './factory/FunctionFactory.ts'
import NamedFactory from './factory/NamedFactory.ts'
import { DependencyKey } from './type/DependencyKey.ts'
import { collect, Collection } from '../../lib/src/collection/Collection.ts'
import Instantiable, {isInstantiable} from './type/Instantiable.ts'

type MaybeFactory = AbstractFactory | undefined
type MaybeDependency = any | undefined
type ResolvedDependency = { param_index: number, key: DependencyKey, resolved: any }

/**
 * Interface used to keep track of singleton factory values, by their dependency key.
 */
interface InstanceRef {
    key: DependencyKey,
    value: any,
}

/**
 * Error thrown when a factory is registered with a duplicate dependency key.
 * @extends Error
 */
class DuplicateFactoryKeyError extends Error {
    constructor(key: DependencyKey) {
        super(`A factory definition already exists with the key for ${key}.`)
    }
}

/**
 * Error thrown when a dependency key that has not been registered is passed to a resolver.
 * @extends Error
 */
class InvalidDependencyKeyError extends Error {
    constructor(key: DependencyKey) {
        super(`No such dependency is registered with this container: ${key}`)
    }

}

/**
 * A factory-based inversion-of-control container.
 */
class Container {
    /**
     * Collection of factories registered with this container.
     * @type Collection<AbstractFactory>
     */
    private factories: Collection<AbstractFactory> = new Collection<AbstractFactory>()

    /**
     * Collection of singleton instances produced by this container.
     * @type Collection<InstanceRef>
     */
    private instances: Collection<InstanceRef> = new Collection<InstanceRef>()

    constructor() {
        this.register(Container)
        this.instances.push({
            key: Container,
            value: this,
        })

        this.register_singleton('injector', this)
    }

    /**
     * Register a basic instantiable class as a standard Factory with this container.
     * @param {Instantiable} dependency
     */
    register(dependency: Instantiable<any>) {
        if ( this.resolve(dependency) )
            throw new DuplicateFactoryKeyError(dependency)

        const factory = new Factory(dependency)
        this.factories.push(factory)
    }

    /**
     * Register the given function as a factory within the container.
     * @param {string} name - unique name to identify the factory in the container
     * @param {function} producer - factory to produce a value
     */
    register_producer(name: string, producer: () => any) {
        if ( this.resolve(name) )
            throw new DuplicateFactoryKeyError(name)

        const factory = new FunctionFactory(name, producer)
        this.factories.push(factory)
    }

    /**
     * Register a basic instantiable class as a standard Factory with this container,
     * identified by a string name rather than static class.
     * @param {string} name - unique name to identify the factory in the container
     * @param {Instantiable} dependency
     */
    register_named(name: string, dependency: Instantiable<any>) {
        if ( this.resolve(name) )
            throw new DuplicateFactoryKeyError(name)

        const factory = new NamedFactory(name, dependency)
        this.factories.push(factory)
    }

    /**
     * Register a value as a singleton in the container. It will not be instantiated, but
     * can be injected by its unique name.
     * @param {string} key - unique name to identify the singleton in the container
     * @param value
     */
    register_singleton(key: string, value: any) {
        if ( this.resolve(key) )
            throw new DuplicateFactoryKeyError(key)

        this.factories.push(new SingletonFactory(value, key))
    }

    /**
     * Register a given factory with the container.
     * @param {AbstractFactory} factory
     */
    register_factory(factory: AbstractFactory) {
        if ( !this.factories.includes(factory) )
            this.factories.push(factory)
    }

    /**
     * Returns true if the container has an already-produced value for the given key.
     * @param {DependencyKey} key
     */
    has_instance(key: DependencyKey): boolean {
        return this.instances.where('key', '=', key).isNotEmpty()
    }

    /**
     * Returns true if the container has a factory for the given key.
     * @param {DependencyKey} key
     */
    has_key(key: DependencyKey): boolean {
        return !!this.resolve(key)
    }

    /**
     * Get the already-produced value for the given key, if one exists.
     * @param {DependencyKey} key
     */
    get_existing_instance(key: DependencyKey): MaybeDependency {
        const instances = this.instances.where('key', '=', key)
        if ( instances.isNotEmpty() ) return instances.first()
    }

    /**
     * Find the factory for the given key, if one is registered with this container.
     * @param {DependencyKey} key
     */
    resolve(key: DependencyKey): MaybeFactory {
        const factory = this.factories.firstWhere(item => item.match(key))
        if ( factory ) return factory
    }

    /**
     * Resolve the dependency key. If a singleton value for that key already exists in this container,
     * return that value. Otherwise, use the factory an given parameters to produce and return the value.
     * @param {DependencyKey} key
     * @param {...any} parameters
     */
    resolve_and_create(key: DependencyKey, ...parameters: any[]): any {
        // If we've already instantiated this, just return that
        const instance = this.get_existing_instance(key)
        if ( typeof instance !== 'undefined' ) return instance.value

        // Otherwise, attempt to create it
        const factory = this.resolve(key)
        if ( !factory )
            throw new InvalidDependencyKeyError(key)

        // Produce and store a new instance
        const new_instance = this.produce_factory(factory, parameters)
        this.instances.push({
            key,
            value: new_instance,
        })

        return new_instance
    }

    /**
     * Given a factory and manually-provided parameters, resolve the dependencies for the
     * factory and produce its value.
     * @param {AbstractFactory} factory
     * @param {array} parameters
     */
    protected produce_factory(factory: AbstractFactory, parameters: any[]) {
        // Create the dependencies for the factory
        const keys = factory.get_dependency_keys().filter(req => this.has_key(req.key))
        const dependencies = keys.map<ResolvedDependency>(req => {
            return {
                param_index: req.param_index,
                key: req.key,
                resolved: this.resolve_and_create(req.key),
            }
        }).sortBy('param_index')

        // Build the arguments for the factory, using dependencies in the
        // correct param_index positions, or parameters of we don't have
        // the dependency.
        const construction_args = []
        let params = collect(parameters).reverse()
        for ( let i = 0; i <= dependencies.max('param_index'); i++ ) {
            const dep = dependencies.firstWhere('param_index', '=', i)
            if ( dep ) construction_args.push(dep.resolved)
            else construction_args.push(params.pop())
        }

        // Produce a new instance
        return factory.produce(construction_args, params.reverse().all())
    }

    /**
     * Create an instance of the given target. The target can either be a DependencyKey registered with
     * this container (in which case, the singleton value will be returned), or an instantiable class.
     *
     * If the instantiable class has the Injectable decorator, its injectable parameters will be automatically
     * injected into the instance.
     * @param {DependencyKey} target
     * @param {...any} parameters
     */
    make(target: DependencyKey, ...parameters: any[]) {
        if ( this.has_key(target) )
            return this.resolve_and_create(target, ...parameters)
        else if ( typeof target !== 'string' && isInstantiable(target) )
            return this.produce_factory(new Factory(target), parameters)
        else
            throw new TypeError(`Invalid or unknown make target: ${target}`)
    }

    /**
     * Get a collection of dependency keys required by the given target, if it is registered with this container.
     * @param {DependencyKey} target
     */
    get_dependencies(target: DependencyKey): Collection<DependencyKey> {
        const factory = this.resolve(target)

        if ( !factory )
            throw new InvalidDependencyKeyError(target)

        return factory.get_dependency_keys().pluck('key')
    }
}

export {
    Container,
    InvalidDependencyKeyError,
    DuplicateFactoryKeyError,
    MaybeDependency,
    MaybeFactory,
    ResolvedDependency,
    InstanceRef,
}