import crypto from 'crypto'

import bodyParser from 'body-parser'
import cookieParser from 'cookie-parser'

import express, { Request, Router } from 'express'

import { StatusCodes } from 'http-status-codes'

import {
    createDatabase,
    createProblem,
    createSolution,
    deleteProblem,
    deleteSolution,
    getProblem,
    getProblems,
    getSolution,
    getSolutions,
    getUser,
    getUsers,
    updateProblem,
    updateSolution,
} from './db/database'

import {
    isAdministrator,
    isStudent,
    Opaque,
    Problem as ProblemModel,
    ProblemId,
    Solution as SolutionModel,
    SolutionId,
    SolutionStat,
    User as UserModel,
    UserId,
} from '../shared/model'
import { initialDatabaseValue } from './db/example-data'

import { validateObjectKeys } from '../shared/utils'
import { setupOAuth } from './auth'

type SessionId = Opaque<string, string, 'session'>

export interface SessionService {
    createSession(userId: UserId): SessionId
    getUserForSession(sid: SessionId): UserId | null
}

export async function createApiRouter() {
    const sessionStore: Record<SessionId, UserId> = {}
    const sessions: SessionService = {
        createSession(userId: UserId) {
            const sid = crypto.randomBytes(10).toString('hex') as SessionId
            sessionStore[sid] = userId
            return sid
        },
        getUserForSession(sid: SessionId) {
            return sessionStore[sid] ?? null
        },
    }

    const db = createDatabase(process.env.DATABASE_PATH ?? './db.local.json', initialDatabaseValue)

    async function getRequestUser(req: Request): Promise<UserModel | null> {
        const userId = sessions.getUserForSession(req.cookies.sid)
        if (!userId) {
            return null
        }

        return await getUser(db, userId)
    }

    const r: Router = express.Router()

    r.use(bodyParser.json())
    r.use(cookieParser())

    const authRouter: Router = express.Router()

    setupOAuth(authRouter, db, sessions)
    r.use('/auth', authRouter)

    r.get('/api/status', (req, res) => {
        res.json({ url: req.originalUrl, status: 'ok' })
    })

    r.get('/api/current-user', async (req, res) => {
        res.json(await getRequestUser(req))
    })

    // r.post('/api/login', async (req, res) => {
    //     const { id, name } = req.body

    //     const user = await getUser(db, id)
    //     if (!user) {
    //         res.sendStatus(StatusCodes.FORBIDDEN)
    //         return
    //     }

    //     res.cookie('sid', sessions.createSession(id), { maxAge: 1000 * 60 * 60 * 24 * 7 })
    //     res.json({ status: 'ok' })
    // })

    r.post('/api/logout', (req, res) => {
        res.cookie('sid', '', { expires: new Date() })
        res.json({ status: 'ok' })
    })

    r.get('/api/users', async (req, res) => {
        const requestUser = await getRequestUser(req)
        if (!requestUser || !isAdministrator(requestUser.role)) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        const users = await getUsers(db)
        res.json(users)
    })

    r.get('/api/problems', async (req, res) => {
        type ProblemWithSolutionsCount = ProblemModel & { solutionsCount?: number }

        const problems: ProblemWithSolutionsCount[] = await getProblems(db)
        const solutions = await getSolutions(db)

        const solutionCounts: Record<ProblemId, number> = {}

        for (const s of solutions) {
            solutionCounts[s.forProblem] ||= 0
            solutionCounts[s.forProblem]++
        }

        for (const p of problems) {
            p.solutionsCount = solutionCounts[p.id] || 0
        }

        res.json(problems)
    })

    r.get('/api/problem/:id', async (req, res) => {
        res.json(await getProblem(db, req.params.id))
    })

    r.patch('/api/problem/:id', async (req, res) => {
        const id = req.params.id as ProblemId

        const user = await getRequestUser(req)
        // l'utente deve essere loggato
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        // l'utente deve essere un admin o un moderatore
        if (!isAdministrator(user.role)) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        // uno studente può modificare solo il campo "content"
        if (user.role === 'moderator' && !validateObjectKeys<keyof ProblemModel>(req.body, ['content'])) {
            res.status(StatusCodes.UNAUTHORIZED)
            res.send(`a moderator can only modify the field "content"`)
            return
        }

        await updateProblem(db, id, req.body)

        res.send({ status: 'ok' })
    })

    r.delete('/api/problem/:id', async (req, res) => {
        const id = req.params.id as ProblemId

        const user = await getRequestUser(req)
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        if (user.role !== 'admin') {
            res.status(StatusCodes.UNAUTHORIZED)
            res.send(`only an admin can delete this entity`)
            return
        }

        await deleteProblem(db, id)

        res.send({ status: 'ok' })
    })

    r.post('/api/problem', async (req, res) => {
        const user = await getRequestUser(req)
        // l'utente deve essere loggato
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }
        // Solo un amministratore può inviare nuovi problemi
        if (user.role !== 'admin' && user.role !== 'moderator') {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }
        // Il contenuto del problema deve essere non vuoto
        if (req.body.content.trim().length === 0) {
            res.sendStatus(StatusCodes.UNPROCESSABLE_ENTITY)
            return
        }

        const problemNextId = (await getProblems(db)).map(p => parseInt(p.id)).reduce((acc, v) => Math.max(acc, v), 0) + 1

        const id = await createProblem(db, {
            title: req.body.title ?? `Problema ${problemNextId}`,
            content: req.body.content,
            createdBy: user.id,
        })

        res.json(id)
    })

    // questa route ritorna la lista di utenti con associato numero di soluzioni inviate, corrette.
    r.get('/api/stats', async (req, res) => {
        let queryUser = (req.query.user ?? null) as UserId | null

        let solutions = await getSolutions(db)

        if (queryUser !== null) {
            solutions = solutions.filter(s => s.sentBy === queryUser)
        }

        const stats: Record<string, SolutionStat> = {}

        solutions.forEach(s => {
            if (!stats[s.sentBy]) {
                stats[s.sentBy] = {
                    sentSolutionsCount: s.status !== 'pending' ? 1 : 0,
                    correctSolutionsCount: s.status === 'correct' ? 1 : 0,
                }
            } else {
                if (s.status !== 'pending') {
                    stats[s.sentBy].sentSolutionsCount += 1
                }
                if (s.status === 'correct') {
                    stats[s.sentBy].correctSolutionsCount += 1
                }
            }
        })

        return res.json(stats)
    })

    r.get('/api/solutions', async (req, res) => {
        let queryUser = (req.query.user ?? null) as UserId | null
        let queryProblem = (req.query.problem ?? null) as ProblemId | null
        let isPublic = req.query.public === ''

        const requestUser = await getRequestUser(req)

        let solutions = await getSolutions(db)
        // se l'utente non è loggato o se non è un amministratore, mostra solo le soluzioni "visibili"
        if (!requestUser || !isAdministrator(requestUser.role)) {
            solutions = solutions.filter(s => s.visible || (requestUser && s.sentBy === requestUser.id))
        }
        // filtra rispetto agli utenti
        if (queryUser !== null) {
            solutions = solutions.filter(s => s.sentBy === queryUser)
        }

        if (isPublic) {
            solutions = solutions.filter(s => s.visible)
        }

        // filtra rispetto ai problemi
        if (queryProblem !== null) {
            solutions = solutions.filter(s => s.forProblem === queryProblem)
        }

        res.json(solutions)
    })

    r.get('/api/solution/:id', async (req, res) => {
        const user = await getRequestUser(req)

        const solution = await getSolution(db, req.params.id as SolutionId)
        // la soluzione deve esistere
        if (solution === null) {
            res.sendStatus(StatusCodes.NOT_FOUND)
            return
        }
        // uno studente può vedere solo soluzioni visibili o proprie soluzione
        if (!solution.visible && user && isStudent(user.role) && solution.sentBy !== user.id) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        res.json(solution)
    })

    r.post('/api/solution', async (req, res) => {
        const user = await getRequestUser(req)
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        await createSolution(db, {
            sentBy: user.id,
            forProblem: req.body.forProblem,
            content: req.body.content,
        })

        res.send({ status: 'ok' })
    })

    r.patch('/api/solution/:id', async (req, res) => {
        const id = req.params.id as SolutionId

        const user = await getRequestUser(req)
        // l'utente deve essere loggato
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        const solution = await getSolution(db, id)
        // la soluzione deve esistere
        if (solution === null) {
            res.sendStatus(404)
            return
        }
        // uno studente non può modificare una soluzione di un altro utente
        if (user.role === 'student' && solution.sentBy !== user.id) {
            res.status(StatusCodes.UNAUTHORIZED)
            res.send(`a student can only modify its own solution`)
            return
        }
        // uno studente può modificare solo il campo "content"
        if (user.role === 'student' && !validateObjectKeys<keyof SolutionModel>(req.body, ['content'])) {
            res.status(StatusCodes.UNAUTHORIZED)
            res.send(`a student can only modify the field "content"`)
            return
        }
        // un moderatore può modificare solo i campi "content", "visible", "status"
        if (user.role === 'moderator' && !validateObjectKeys<keyof SolutionModel>(req.body, ['content', 'status', 'visible'])) {
            res.status(StatusCodes.UNAUTHORIZED)
            res.send(`a moderator can only modify the fields "content", "visible", "status"`)
            return
        }

        await updateSolution(db, id, req.body)

        res.json({ status: 'ok' })
    })

    r.delete('/api/solution/:id', async (req, res) => {
        const id = req.params.id as SolutionId

        const user = await getRequestUser(req)
        // l'utente deve essere loggato
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        const solution = await getSolution(db, id)

        // la soluzione deve esistere
        if (solution === null) {
            res.sendStatus(StatusCodes.NOT_FOUND)
            return
        }

        // solo un admin può eliminare le soluzioni degli utenti
        if (user.role !== 'admin' && solution.sentBy !== user.id) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        await deleteSolution(db, id)

        res.send({ status: 'ok' })
    })

    r.get('/api/user/:id', async (req, res) => {
        const user = await getRequestUser(req)

        // intanto l'utente deve essere loggato
        if (!user) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        // solo gli amministratori possono usare questa route
        if (!isAdministrator(user.role)) {
            res.sendStatus(StatusCodes.UNAUTHORIZED)
            return
        }

        const requestedUser = await getUser(db, req.params.id)

        // l'utente richiesto magari deve esistere
        if (!requestedUser) {
            res.sendStatus(404)
            return
        }

        res.json(requestedUser)
    })

    return r
}