lib/src/di/Container.ts

import {DependencyKey, InstanceRef, Instantiable, isInstantiable} from './types'
import {AbstractFactory} from './factory/AbstractFactory'
import {collect, Collection, globalRegistry, logIfDebugging} from '../util'
import {Factory} from './factory/Factory'
import {DuplicateFactoryKeyError} from './error/DuplicateFactoryKeyError'
import {ClosureFactory} from './factory/ClosureFactory'
import NamedFactory from './factory/NamedFactory'
import SingletonFactory from './factory/SingletonFactory'
import {InvalidDependencyKeyError} from './error/InvalidDependencyKeyError'

export type MaybeFactory<T> = AbstractFactory<T> | undefined
export type MaybeDependency = any | undefined
export type ResolvedDependency = { paramIndex: number, key: DependencyKey, resolved: any }

/**
 * A container of resolve-able dependencies that are created via inversion-of-control.
 */
export class Container {
    /**
     * Get the global instance of this container.
     */
    public static getContainer(): Container {
        const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
        if ( !existing ) {
            const container = new Container()
            globalRegistry.setGlobal('extollo/injector', container)
            return container
        }

        return existing
    }

    /**
     * Collection of factories registered with this container.
     * @type Collection<AbstractFactory>
     */
    protected factories: Collection<AbstractFactory<unknown>> = new Collection<AbstractFactory<unknown>>()

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

    constructor() {
        this.registerSingletonInstance<Container>(Container, this)
        this.registerSingleton('injector', this)
    }

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

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

    /**
     * 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
     */
    registerProducer(name: DependencyKey, producer: () => any): this {
        if ( this.resolve(name) ) {
            throw new DuplicateFactoryKeyError(name)
        }

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

    /**
     * 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
     */
    registerNamed(name: string, dependency: Instantiable<any>): this {
        if ( this.resolve(name) ) {
            throw new DuplicateFactoryKeyError(name)
        }

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

    /**
     * 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
     */
    registerSingleton<T>(key: DependencyKey, value: T): this {
        if ( this.resolve(key) ) {
            throw new DuplicateFactoryKeyError(key)
        }

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

    /**
     * Register a static class to the container along with its already-instantiated
     * instance that will be used to resolve the class.
     * @param staticClass
     * @param instance
     */
    registerSingletonInstance<T>(staticClass: Instantiable<T>, instance: T): this {
        if ( this.resolve(staticClass) ) {
            throw new DuplicateFactoryKeyError(staticClass)
        }

        this.register(staticClass)
        this.instances.push({
            key: staticClass,
            value: instance,
        })

        return this
    }

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

        return this
    }

    /**
     * Returns true if the container has an already-produced value for the given key.
     * @param {DependencyKey} key
     */
    hasInstance(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
     */
    hasKey(key: DependencyKey): boolean {
        return Boolean(this.resolve(key))
    }

    /**
     * Get the already-produced value for the given key, if one exists.
     * @param {DependencyKey} key
     */
    getExistingInstance(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<unknown> {
        const factory = this.factories.firstWhere(item => item.match(key))
        if ( factory ) {
            return factory
        } else {
            logIfDebugging('extollo.di.injector', 'unable to resolve factory', factory, this.factories)
        }
    }

    /**
     * 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
     */
    resolveAndCreate(key: DependencyKey, ...parameters: any[]): any {
        logIfDebugging('extollo.di.injector', 'resolveAndCreate', key, {parameters})

        // If we've already instantiated this, just return that
        const instance = this.getExistingInstance(key)
        logIfDebugging('extollo.di.injector', 'resolveAndCreate existing instance?', instance)
        if ( typeof instance !== 'undefined' ) {
            return instance.value
        }

        // Otherwise, attempt to create it
        const factory = this.resolve(key)
        logIfDebugging('extollo.di.injector', 'resolveAndCreate factory', factory)
        if ( !factory ) {
            throw new InvalidDependencyKeyError(key)
        }

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

        return newInstance
    }

    /**
     * Given a factory and manually-provided parameters, resolve the dependencies for the
     * factory and produce its value.
     * @param {AbstractFactory} factory
     * @param {array} parameters
     */
    protected produceFactory<T>(factory: AbstractFactory<T>, parameters: any[]): T {
        // Create the dependencies for the factory
        const keys = factory.getDependencyKeys().filter(req => this.hasKey(req.key))
        const dependencies = keys.map<ResolvedDependency>(req => {
            return {
                paramIndex: req.paramIndex,
                key: req.key,
                resolved: this.resolveAndCreate(req.key),
            }
        }).sortBy('paramIndex')

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

        // Produce a new instance
        const inst = factory.produce(constructorArguments, params.reverse().all())

        factory.getInjectedProperties().each(dependency => {
            if ( dependency.key && inst ) {
                (inst as any)[dependency.property] = this.resolveAndCreate(dependency.key)
            }
        })

        return inst
    }

    /**
     * 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<T>(target: DependencyKey, ...parameters: any[]): T {
        if ( this.hasKey(target) ) {
            return this.resolveAndCreate(target, ...parameters)
        } else if ( typeof target !== 'string' && isInstantiable(target) ) {
            return this.produceFactory(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
     */
    getDependencies(target: DependencyKey): Collection<DependencyKey> {
        const factory = this.resolve(target)

        if ( !factory ) {
            throw new InvalidDependencyKeyError(target)
        }

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

    /**
     * Given a different container, copy the factories and instances from this container over to it.
     * @param container
     */
    cloneTo(container: Container): this {
        container.factories = this.factories.clone()
        container.instances = this.instances.clone()
        return this
    }
}