// Copyright 2016-2017, Pulumi Corporation.  All rights reserved.

import { registerResource, registerResourceOutputs } from "./runtime/resource";
import { getRootResource } from "./runtime/settings";

export type ID = string;  // a provider-assigned ID.
export type URN = string; // an automatically generated logical URN, used to stably identify resources.

/**
 * Resource represents a class whose CRUD operations are implemented by a provider plugin.
 */
export abstract class Resource {
    /**
     * urn is the stable logical URN used to distinctly address a resource, both before and after
     * deployments.
     */
    public readonly urn: Promise<URN>;

    /**
     * Creates and registers a new resource object.  t is the fully qualified type token and name is
     * the "name" part to use in creating a stable and globally unique URN for the object.
     * dependsOn is an optional list of other resources that this resource depends on, controlling
     * the order in which we perform resource operations.
     *
     * @param t The type of the resource.
     * @param name The _unqiue_ name of the resource.
     * @param custom True to indicate that this is a custom resource, managed by a plugin.
     * @param props The arguments to use to populate the new resource.
     * @param opts A bag of options that control this resource's behavior.
     */
    constructor(t: string, name: string, custom: boolean, props: ComputedValues = {}, opts: ResourceOptions = {}) {
        if (!t) {
            throw new Error("Missing resource type argument");
        }
        if (!name) {
            throw new Error("Missing resource name argument (for URN creation)");
        }

        // If there wasn't an explicit parent, and a root resource exists, parent to that.
        if (!opts.parent) {
            opts.parent = getRootResource();
        }

        // Now kick off the resource registration.  If we are actually performing a deployment, this
        // resource's properties will be resolved asynchronously after the operation completes, so
        // that dependent computations resolve normally.  If we are just planning, on the other
        // hand, values will never resolve.
        registerResource(this, t, name, custom, props, opts);
    }
}

/**
 * ResourceOptions is a bag of optional settings that control a resource's behavior.
 */
export interface ResourceOptions {
    /**
     * An optional parent resource to which this resource belongs.
     */
    parent?: Resource;
    /**
     * An optional additional explicit dependencies on other resources.
     */
    dependsOn?: Resource[];
    /**
     * When set to true, protect ensures this resource cannot be deleted.
     */
    protect?: boolean;
}

/**
 * CustomResource is a resource whose create, read, update, and delete (CRUD) operations are managed
 * by performing external operations on some physical entity.  The engine understands how to diff
 * and perform partial updates of them, and these CRUD operations are implemented in a dynamically
 * loaded plugin for the defining package.
 */
export abstract class CustomResource extends Resource {
    /**
     * id is the provider-assigned unique ID for this managed resource.  It is set during
     * deployments and may be missing (undefined) during planning phases.
     */
    public readonly id: Computed<ID>;

    /**
     * Creates and registers a new managed resource.  t is the fully qualified type token and name
     * is the "name" part to use in creating a stable and globally unique URN for the object.
     * dependsOn is an optional list of other resources that this resource depends on, controlling
     * the order in which we perform resource operations. Creating an instance does not necessarily
     * perform a create on the physical entity which it represents, and instead, this is dependent
     * upon the diffing of the new goal state compared to the current known resource state.
     *
     * @param t The type of the resource.
     * @param name The _unqiue_ name of the resource.
     * @param props The arguments to use to populate the new resource.
     * @param opts A bag of options that control this resource's behavior.
     */
    constructor(t: string, name: string, props?: ComputedValues, opts?: ResourceOptions) {
        super(t, name, true, props, opts);
    }
}

/**
 * ComponentResource is a resource that aggregates one or more other child resources into a higher
 * level abstraction. The component resource itself is a resource, but does not require custom CRUD
 * operations for provisioning.
 */
export class ComponentResource extends Resource {
    /**
     * Creates and registers a new component resource.  t is the fully qualified type token and name
     * is the "name" part to use in creating a stable and globally unique URN for the object. parent
     * is the optional parent for this component, and dependsOn is an optional list of other
     * resources that this resource depends on, controlling the order in which we perform resource
     * operations.
     *
     * @param t The type of the resource.
     * @param name The _unqiue_ name of the resource.
     * @param props The arguments to use to populate the new resource.
     * @param opts A bag of options that control this resource's behavior.
     * @param protect True to ensure this resource cannot be deleted.
     */
    constructor(t: string, name: string, props?: ComputedValues, opts?: ResourceOptions) {
        super(t, name, false, props, opts);
    }

    // registerOutputs registers synthetic outputs that a component has initialized, usually by allocating
    // other child sub-resources and propagating their resulting property values.
    protected registerOutputs(outputs: ComputedValues | undefined): void {
        if (outputs) {
            registerResourceOutputs(this, outputs);
        }
    }
}

/**
 * Computed is a property output for a resource.  It is just a promise that also permits undefined
 * values.  The undefined values are used during planning, when the actual final value of a resource
 * may not yet be known.
 */
export type Computed<T> = Promise<T | undefined>;

/**
 * ComputedValue is a property input for a resource.  It may be a promptly available T or a promise
 * for one.
 */
export type ComputedValue<T> = T | undefined | Promise<T | undefined>;

/**
 * ComputedValues is a map of property name to optional property input, one for each resource
 * property value.
 */
export type ComputedValues = { [key: string]: ComputedValue<any> };