/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License.
 */
import * as BB from 'botbuilder'
import { CLDebug, DebugType } from './CLDebug'
import { BotMemory } from './Memory/BotMemory'
import { BotState } from './Memory/BotState'
import { AppBase } from '@conversationlearner/models'

export class CLMemory {
    private static memoryStorage: BB.Storage | null = null
    private memCache = {}
    private userkey: string
    private turnContext: BB.TurnContext | undefined

    public static Init(memoryStorage: BB.Storage | null): void {
        CLMemory.memoryStorage = memoryStorage
        // If memory storage not defined use disk storage
        if (!memoryStorage) {
            CLDebug.Log('Storage not defined.  Defaulting to in-memory storage.')
            CLMemory.memoryStorage = new BB.MemoryStorage()
        }
    }

    private constructor(userkey: string) {
        this.userkey = userkey
    }
  
    public static GetMemory(key: string): CLMemory {
        return new CLMemory(key)
    }

    // Generate memory key from session
    public static async InitMemory(turnContext: BB.TurnContext): Promise<CLMemory> {
        const user = turnContext.activity.from
        const conversationReference = BB.TurnContext.getConversationReference(turnContext.activity)
        if (!user) {
            throw new Error(`Attempted to initialize memory, but cannot get memory key because current request did not have 'from'/user specified`)
        }
        if (!user.id) {
            throw new Error(`Attempted to initialize memory, but user.id was not provided which is required for use as memory key.`)
        }

        let memory = new CLMemory(user.id)
        memory.turnContext = turnContext
        await memory.BotState.SetConversationReference(conversationReference)
        return memory
    }

    private Key(datakey: string): string {
        return `${this.userkey}_${datakey}`
    }

    public async GetAsync(datakey: string): Promise<any> {
        if (!CLMemory.memoryStorage) {
            throw new Error('Memory storage not found')
        }

        let key = this.Key(datakey)
        let cacheData = this.memCache[key]
        if (cacheData) {
            CLDebug.Log(`-< ${key} : ${cacheData}`, DebugType.MemVerbose)
            return cacheData
        } else {
            try {
                let data = await CLMemory.memoryStorage.read([key])
                if (data[key]) {
                    this.memCache[key] = data[key].value
                } else {
                    this.memCache[key] = null
                }
                CLDebug.Log(`R< ${key} : ${this.memCache[key]}`, DebugType.Memory)
                return this.memCache[key]
            }
            catch (err) {
                CLDebug.Error(err);
                return null;
            }
        }
    }

    public async SetAsync(datakey: string, jsonString: string): Promise<void> {
        if (!CLMemory.memoryStorage) {
            throw new Error('Memory storage not found')
        }

        if (jsonString == "null") {
            await this.DeleteAsync(datakey)
            return
        }

        let key = this.Key(datakey)
        try {
            // First check mem cache to see if anything has changed, if not, can skip write
            let cacheData = this.memCache[key]
            if (cacheData == jsonString) {
                CLDebug.Log(`-> ${key} : ${jsonString}`, DebugType.MemVerbose)
            } else {
                // Write to memory storage (use * for etag)
                await CLMemory.memoryStorage.write({ [key]: { value: jsonString, eTag: '*' } })
                this.memCache[key] = jsonString
                CLDebug.Log(`W> ${key} : ${jsonString}`, DebugType.Memory)
            }
        } catch (err) {
            CLDebug.Error(err)
        }
    }

    public async DeleteAsync(datakey: string): Promise<void> {
        let key = this.Key(datakey)

        try {
            // TODO: Remove possibility of being null
            if (!CLMemory.memoryStorage) {
                CLDebug.Error(`You attempted to delete key: ${key} before memoryStorage was defined`)
            }
            else {

                CLMemory.memoryStorage.delete([key])
                this.memCache[key] = null
                CLDebug.Log(`D> ${key} : -----`, DebugType.Memory)
            }
        } catch (err) {
            CLDebug.Error(err)
        }
    }

    public async SetAppAsync(app: AppBase | null): Promise<void> {
        const curApp = await this.BotState.GetApp();
        await this.BotState._SetAppAsync(app)

        if (!app || !curApp || curApp.appId !== app.appId) {
            await this.BotMemory.ClearAsync()
        }
    }

    public get BotMemory(): BotMemory {
        return BotMemory.Get(this)
    }

    public get BotState(): BotState {
        return BotState.Get(this)
    }

    public get TurnContext(): BB.TurnContext | undefined {
        return this.turnContext
    }
}