import {AppClass} from '../../lifecycle/AppClass'
import {HTTPMethod, Request} from '../lifecycle/Request'
import {Application} from '../../lifecycle/Application'
import {RouteGroup} from './RouteGroup'
import {ResponseFactory} from '../response/ResponseFactory'
import {Response} from '../lifecycle/Response'
import {Controllers} from '../../service/Controllers'
import {ErrorWithContext, Collection} from '../../util'
import {Container} from '../../di'
import {Controller} from '../Controller'
import {Middlewares} from '../../service/Middlewares'
import {Middleware} from './Middleware'
import {Config} from '../../service/Config'

/**
 * Type alias for an item that is a valid response object, or lack thereof.
 */
export type ResponseObject = ResponseFactory | string | number | void | any | Promise<ResponseObject>

/**
 * Type alias for an item that defines a direct route handler.
 */
export type RouteHandler = ((request: Request, response: Response) => ResponseObject) | ((request: Request) => ResponseObject) | (() => ResponseObject) | string

/**
 * Type alias for a function that applies a route handler to the request.
 * The goal is to transform RouteHandlers to ResolvedRouteHandler.
 */
export type ResolvedRouteHandler = (request: Request) => ResponseObject


// TODO domains, named routes - support this on groups as well

/**
 * A class that can be used to build and reference dynamic routes in the application.
 *
 * Routes can be defined in nested groups, with prefixes and middleware handlers.
 *
 * @example
 * ```typescript
 * Route.post('/api/v1/ping', (request: Request) => {
 *     return 'pong!'
 * })
 *
 * Route.group('/api/v2', () => {
 *     Route.get('/status', 'controller::api:v2:Status.getStatus').pre('auth:UserOnly')
 * })
 * ```
 */
export class Route extends AppClass {
    /** Routes that have been created and registered in the application. */
    private static registeredRoutes: Route[] = []

    /** Groups of routes that have been registered with the application. */
    private static registeredGroups: RouteGroup[] = []

    /**
     * The current nested group stack. This is used internally when compiling the routes by nested group.
     * @private
     */
    private static compiledGroupStack: RouteGroup[] = []

    /** Register a route group handler. */
    public static registerGroup(group: RouteGroup): void {
        this.registeredGroups.push(group)
    }

    /**
     * Load and compile all of the registered routes and their groups, accounting
     * for nested groups and resolving handlers.
     *
     * This function attempts to resolve the route handlers ahead of time to cache
     * them and also expose any handler resolution errors that might happen at runtime.
     */
    public static async compile(): Promise<Route[]> {
        let registeredRoutes = this.registeredRoutes
        const registeredGroups = this.registeredGroups

        this.registeredRoutes = []
        this.registeredGroups = []

        const configService = <Config> Container.getContainer().make(Config)
        const globalMiddleware = configService.get('server.middleware.global', {})

        const stack = [...this.compiledGroupStack].reverse()
        for ( const route of registeredRoutes ) {
            for ( const group of stack ) {
                route.prepend(group.prefix)
                group.getGroupMiddlewareDefinitions()
                    .each(def => route.prependMiddleware(def))
            }

            for ( const group of this.compiledGroupStack ) {
                group.getGroupMiddlewareDefinitions()
                    .each(def => route.appendMiddleware(def))
            }

            // Add the global pre- and post- middleware
            if ( Array.isArray(globalMiddleware?.pre) ) {
                const globalPre = [...globalMiddleware.pre].reverse()
                for ( const item of globalPre ) {
                    if ( typeof item !== 'string' ) {
                        throw new ErrorWithContext(`Invalid global pre-middleware definition. Global middleware must be string-references.`, {
                            configKey: 'server.middleware.global.pre',
                        })
                    }

                    route.prependMiddleware({
                        stage: 'pre',
                        handler: item,
                    })
                }
            }

            if ( Array.isArray(globalMiddleware?.post) ) {
                const globalPost = [...globalMiddleware.post]
                for ( const item of globalPost ) {
                    if ( typeof item !== 'string' ) {
                        throw new ErrorWithContext(`Invalid global post-middleware definition. Global middleware must be string-references.`, {
                            configKey: 'server.middleware.global.post',
                        })
                    }

                    route.appendMiddleware({
                        stage: 'post',
                        handler: item,
                    })
                }
            }

            route.resolvePreflight()  // Try to resolve here to catch any errors at boot-time and pre-compile
            route.resolveHandler()
            route.resolvePostflight()
        }

        for ( const group of registeredGroups ) {
            this.compiledGroupStack.push(group)
            await group.group()

            const childCompilation = await this.compile()
            registeredRoutes = registeredRoutes.concat(childCompilation)

            this.compiledGroupStack.pop()
        }

        return registeredRoutes
    }

    /**
     * Create a new route on the given endpoint for the given HTTP verb.
     * @param method
     * @param definition
     * @param handler
     */
    public static endpoint(method: HTTPMethod | HTTPMethod[], definition: string, handler: RouteHandler): Route {
        const route = new Route(method, handler, definition)
        this.registeredRoutes.push(route)
        return route
    }

    /**
     * Create a new GET route on the given endpoint.
     * @param definition
     * @param handler
     */
    public static get(definition: string, handler: RouteHandler): Route {
        return this.endpoint('get', definition, handler)
    }

    /** Create a new POST route on the given endpoint. */
    public static post(definition: string, handler: RouteHandler): Route {
        return this.endpoint('post', definition, handler)
    }

    /** Create a new PUT route on the given endpoint. */
    public static put(definition: string, handler: RouteHandler): Route {
        return this.endpoint('put', definition, handler)
    }

    /** Create a new PATCH route on the given endpoint. */
    public static patch(definition: string, handler: RouteHandler): Route {
        return this.endpoint('patch', definition, handler)
    }

    /** Create a new DELETE route on the given endpoint. */
    public static delete(definition: string, handler: RouteHandler): Route {
        return this.endpoint('delete', definition, handler)
    }

    /** Create a new route on all HTTP verbs, on the given endpoint. */
    public static any(definition: string, handler: RouteHandler): Route {
        return this.endpoint(['get', 'put', 'patch', 'post', 'delete'], definition, handler)
    }

    /** Create a new route group with the given prefix. */
    public static group(prefix: string, group: () => void | Promise<void>): RouteGroup {
        const grp = <RouteGroup> Application.getApplication().make(RouteGroup, group, prefix)
        this.registeredGroups.push(grp)
        return grp
    }

    /** Middlewares that should be applied to this route. */
    protected middlewares: Collection<{ stage: 'pre' | 'post', handler: RouteHandler }> = new Collection<{stage: 'pre' | 'post'; handler: RouteHandler}>()

    /** Pre-compiled route handlers for the pre-middleware for this route. */
    protected compiledPreflight?: ResolvedRouteHandler[]

    /** Pre-compiled route handlers for the post-middleware for this route. */
    protected compiledHandler?: ResolvedRouteHandler

    /** Pre-compiled route handler for the main route handler for this route. */
    protected compiledPostflight?: ResolvedRouteHandler[]

    constructor(
        /** The HTTP method(s) that this route listens on. */
        protected method: HTTPMethod | HTTPMethod[],

        /** The primary handler of this route. */
        protected readonly handler: RouteHandler,

        /** The route path this route listens on. */
        protected route: string,
    ) {
        super()
    }

    /**
     * Returns true if this route matches the given HTTP verb and request path.
     * @param method
     * @param potential
     */
    public match(method: HTTPMethod, potential: string): boolean {
        if ( Array.isArray(this.method) && !this.method.includes(method) ) {
            return false
        } else if ( !Array.isArray(this.method) && this.method !== method ) {
            return false
        }

        return Boolean(this.extract(potential))
    }

    /**
     * Given a request path, try to extract this route's paramters from the path string.
     *
     * @example
     * For route `/foo/:bar/baz` and input `/foo/bob/baz`, extracts:
     *
     * ```typescript
     * {
     *     bar: 'bob'
     * }
     * ```
     *
     * @param potential
     */
    public extract(potential: string): {[key: string]: string} | undefined {
        const routeParts = (this.route.startsWith('/') ? this.route.substr(1) : this.route).split('/')
        const potentialParts = (potential.startsWith('/') ? potential.substr(1) : potential).split('/')

        const params: any = {}
        let wildcardIdx = 0

        for ( let i = 0; i < routeParts.length; i += 1 ) {
            const part = routeParts[i]

            if ( part === '**' ) {
                params[wildcardIdx] = potentialParts.slice(i).join('/')
                return params
            }

            if ( (potentialParts.length - 1) < i ) {
                return
            }

            if ( part === '*' ) {
                params[wildcardIdx] = potentialParts[i]
                wildcardIdx += 1
            } else if ( part.startsWith(':') ) {
                params[part.substr(1)] = potentialParts[i]
            } else if ( potentialParts[i] !== part ) {
                return
            }
        }

        // If we got here, we didn't find a **
        // So, if the lengths are different, fail
        if ( routeParts.length !== potentialParts.length ) {
            return
        }
        return params
    }

    /**
     * Try to pre-compile and return the preflight handlers for this route.
     */
    public resolvePreflight(): ResolvedRouteHandler[] {
        if ( !this.compiledPreflight ) {
            this.compiledPreflight = this.resolveMiddlewareHandlersForStage('pre')
        }

        return this.compiledPreflight
    }

    /**
     * Try to pre-compile and return the postflight handlers for this route.
     */
    public resolvePostflight(): ResolvedRouteHandler[] {
        if ( !this.compiledPostflight ) {
            this.compiledPostflight = this.resolveMiddlewareHandlersForStage('post')
        }

        return this.compiledPostflight
    }

    /**
     * Try to pre-compile and return the main handler for this route.
     */
    public resolveHandler(): ResolvedRouteHandler {
        if ( !this.compiledHandler ) {
            this.compiledHandler = this.compileResolvedHandler()
        }

        return this.compiledHandler
    }

    /** Register the given middleware as a preflight handler for this route. */
    pre(middleware: RouteHandler): this {
        this.middlewares.push({
            stage: 'pre',
            handler: middleware,
        })

        return this
    }

    /** Register the given middleware as a postflight handler for this route. */
    post(middleware: RouteHandler): this {
        this.middlewares.push({
            stage: 'post',
            handler: middleware,
        })

        return this
    }

    /** Prefix the route's path with the given prefix, normalizing `/` characters. */
    private prepend(prefix: string): this {
        if ( !prefix.endsWith('/') ) {
            prefix = `${prefix}/`
        }
        if ( this.route.startsWith('/') ) {
            this.route = this.route.substring(1)
        }
        this.route = `${prefix}${this.route}`
        return this
    }

    /** Add the given middleware item to the beginning of the preflight handlers. */
    private prependMiddleware(def: { stage: 'pre' | 'post', handler: RouteHandler }): void {
        this.middlewares.prepend(def)
    }

    /** Add the given middleware item to the end of the postflight handlers. */
    private appendMiddleware(def: { stage: 'pre' | 'post', handler: RouteHandler }): void {
        this.middlewares.push(def)
    }

    /**
     * Resolve and return the route handler for this route.
     * @private
     */
    private compileResolvedHandler(): ResolvedRouteHandler {
        const handler = this.handler
        if ( typeof handler !== 'string' ) {
            return (request: Request) => {
                return handler(request, request.response)
            }
        } else {
            const parts = handler.split('.')
            if ( parts.length < 2 ) {
                const e = new ErrorWithContext('Route handler does not specify a method name.')
                e.context = {
                    handler,
                }
                throw e
            }

            const [controllerName, methodName] = parts

            const controllersService = <Controllers> this.make(Controllers)
            const controllerClass = controllersService.get(controllerName)
            if ( !controllerClass ) {
                const e = new ErrorWithContext('Controller not found for route handler.')
                e.context = {
                    handler,
                    controllerName,
                    methodName,
                }
                throw e
            }

            return (request: Request) => {
                // If not a function, then we got a string reference to a controller method
                // So, we need to use the request container to instantiate the controller
                // and bind the method
                const controller = <Controller> request.make(controllerClass, request)
                const method = controller.getBoundMethod(methodName)
                return method()
            }
        }
    }

    /**
     * Resolve and return the route handlers for the given pre- or post-flight stage.
     * @param stage
     * @private
     */
    private resolveMiddlewareHandlersForStage(stage: 'pre' | 'post'): ResolvedRouteHandler[] {
        return this.middlewares.where('stage', '=', stage)
            .map<ResolvedRouteHandler>(def => {
                const handler = def.handler
                if ( typeof handler !== 'string' ) {
                    return (request: Request) => {
                        return handler(request, request.response)
                    }
                } else {
                    const parts = handler.split('.')
                    if ( parts.length < 2 ) {
                        parts.push('apply')  // default middleware method name, if none provided
                    }

                    const [middlewareName, methodName] = parts

                    const middlewaresService = <Middlewares> this.make(Middlewares)
                    const middlewareClass = middlewaresService.get(middlewareName)
                    if ( !middlewareClass ) {
                        const e = new ErrorWithContext('Middleware not found for route handler.')
                        e.context = {
                            handler,
                            middlewareName,
                            methodName,
                        }
                        throw e
                    }

                    return (request: Request) => {
                        // If not a function, then we got a string reference to a middleware method
                        // So, we need to use the request container to instantiate the middleware
                        // and bind the method
                        const middleware = <Middleware> request.make(middlewareClass, request)
                        const method = middleware.getBoundMethod(methodName)
                        return method()
                    }
                }
            })
            .toArray()
    }

    /** Cast the route to an intelligible string. */
    toString(): string {
        const method = Array.isArray(this.method) ? this.method : [this.method]
        return `${method.join('|')} -> ${this.route}`
    }
}