import * as uuidv4 from "uuid/v4"

import * as T from "./Types";
import * as I from "./Interfaces";
import { SubscriptionResponse } from "./Types";

/**
 * Translate an RPC to RPCInfo for serialization.
 * @param rpc The RPC to transform
 * @param owner The owning RPC group's name
 * @throws Error on RPC without name property
 */
export const rpcToRpcinfo = <SubResT = {}>(rpc : T.RPC<any, any, SubResT>, owner: string):T.RpcInfo => {
    switch (typeof rpc){
        case  "object":
            if(rpc['call']){
                return {
                    owner: owner,
                    argNames: extractArgs(rpc['call']),
                    type: "Call",
                    name: rpc.name,
                    call: rpc['call'],
                }
            }else{
                const generator = hookGenerator(<T.HookRPC<any, any, any>>rpc)
                return {
                    owner: owner,
                    argNames: extractArgs(generator(undefined)),
                    type: "Hook",
                    name: rpc.name,
                    generator: generator,
                }
            }
        case "function":
            if(!rpc.name) throw new Error(`
RPC did not provide a name. 
\nUse 'funtion name(..){ .. }' syntax instead.
\n
\n<------------OFFENDING RPC:
\n`+rpc.toString()+`
\n>------------OFFENDING RPC`)
            return {
                owner : owner,
                argNames: extractArgs(rpc),
                type: "Call",
                name: rpc.name,
                call: async(...args) => (<Function>rpc).apply({}, args),
            }
    }
    throw new Error("Bad socketIORPC type "+ typeof rpc)
}

/**
 * Utility function to apply the RPCs of an {@link RPCExporter}.
 * @param socket The websocket (implementation: bsock) to hook on
 * @param exporter The exporter
 * @param makeUnique @default true Attach a suffix to RPC names
 */
export function rpcHooker<SubResT = {}>(socket: I.Socket, exporter:I.RPCExporter<any, any, SubResT>, makeUnique = true):T.ExtendedRpcInfo[]{
    const owner = exporter.name
    const RPCs = [...exporter.exportRPCs()]
    const suffix = makeUnique?"-"+uuidv4().substr(0,4):""
    return RPCs.map(rpc => rpcToRpcinfo(rpc, owner))
    .map(info => {
        const ret:any = info
        ret.uniqueName = info.name+suffix

        switch(info.type){
            case "Hook":
                socket.hook(ret.uniqueName, info.generator(socket))
                break;
            case "Call":
                socket.hook(ret.uniqueName, info.call)
                break;
        }
        socket.on('close', () => socket.unhook(info.name))
        return ret
    })
}
/**
 * Utility function to generate {@link HookFunction} from a RPC
 * @param rpc The RPC to transform
 * @returns A {@link HookFunction}
 */
const hookGenerator = (rpc:T.HookRPC<any, any, any>): T.HookInfo['generator'] => { 
    const argsArr = extractArgs(rpc.hook)
    argsArr.pop()
    const args = argsArr.join(',')

    return eval(`(socket) => async (`+args+`) => { 
        const res = await rpc.hook(`+args+(args.length!==0?',':'')+` (...cbargs) => {
            if(rpc.onCallback) rpc.onCallback.apply({}, cbargs)
            socket.call.apply(socket, [res.uuid, ...cbargs])
        })
        if(res.result === 'Success'){
            if(rpc.onClose){
                socket.on('close', async () => {
                    rpc.onClose(res, rpc)
                })
            }
        }
        return res
    }`)
}

/**
 * Extract a string list of parameters from a function
 * @param f The source function
 */
const extractArgs = (f:Function):string[] => {
    let fn:string
    return (fn = String(f)).substr(0, fn.indexOf(")")).substr(fn.indexOf("(")+1).split(",")
}

/**
 * Simple utility function to create basic {@link SubscriptionResponse}
 * @param uuid optional uuid to use, otherwise defaults to uuid/v4
 */
export function makeSubResponse<T extends {} = {}>(extension:T):SubscriptionResponse & T{
    return {
        result: "Success",
        uuid: uuidv4(),
        ...extension
    }
}