import SwiftUI

@MainActor
final class NativeStore: ObservableObject {
    @Published private(set) var server = ""
    @Published private(set) var appName = "Yuvomi"
    @Published private(set) var user: NativeUser?
    @Published private(set) var permissions: NativePermissions?
    @Published private(set) var setup = false
    @Published private(set) var passwordAllowed = true
    @Published private(set) var oidc = false
    @Published private(set) var twoFactor = false
    @Published private(set) var busy = false
    @Published var error: String?
    @Published private(set) var page = NativePage.home
    @Published private(set) var dashboard: NativeDashboard?
    @Published private(set) var tasks: [NativeTask] = []
    @Published private(set) var notes: [NativeNote] = []
    @Published private(set) var lists: [NativeShoppingList] = []
    @Published private(set) var items: [NativeShoppingItem] = []
    @Published private(set) var selectedList: NativeShoppingList?
    private var api: NativeAPI?
    private var vault: NativeSessionVault?
    private var generation = 0

    func restore() async {
        guard server.isEmpty, let saved = UserDefaults.standard.string(forKey: "native-origin") else { return }
        await connect(saved)
    }

    @discardableResult
    private func run(_ operation: () async throws -> Void) async -> Bool {
        guard !busy else { return false }
        let current = generation
        busy = true
        error = nil
        defer { if generation == current { busy = false } }
        do {
            try await operation()
            return true
        } catch {
            guard current == generation else { return false }
            if case NativeAPIError.response(401) = error, user != nil {
                clearLoadedData()
                self.error = "Deine Sitzung ist abgelaufen. Bitte erneut anmelden."
            } else {
                self.error = (error as? NativeAPIError)?.errorDescription ?? NativeAPIError.unavailable.errorDescription
            }
            return false
        }
    }

    func connect(_ input: String) async {
        await run {
            let address = try ServerAddress(input)
            let storage = NativeSessionVault(origin: address.url.absoluteString)
            let client = try NativeAPI(server: address, saved: storage.load(), persist: storage.save)
            let metadata = try await client.request("/version", as: NativeBootstrap.self)
            let authentication = try await client.request("/auth/oidc/config", as: NativeAuthentication.self)
            api = client
            vault = storage
            server = address.url.absoluteString
            appName = metadata.appName
            setup = metadata.setupRequired
            oidc = authentication.enabled
            passwordAllowed = authentication.passwordLoginEnabled || authentication.guestPasswordLoginEnabled == true
            UserDefaults.standard.set(server, forKey: "native-origin")
            do { try await accept(client.request("/auth/me", as: NativeIdentity.self)) } catch NativeAPIError.response(
                401)
            { return }
        }
    }

    func login(username: String, password: String, displayName: String) async {
        await run {
            guard let api else { throw NativeAPIError.closed }
            if setup {
                let _: NativeEmpty = try await api.request(
                    "/auth/setup", method: "POST",
                    body: [
                        "username": .string(username.trimmingCharacters(in: .whitespaces)),
                        "password": .string(password),
                        "display_name": .string(displayName.isEmpty ? username : displayName),
                    ], as: NativeEmpty.self)
            }
            let response = try await api.request(
                "/auth/login", method: "POST",
                body: [
                    "username": .string(username.trimmingCharacters(in: .whitespaces)), "password": .string(password),
                ], as: NativeIdentity.self)
            if response.twoFactorRequired == true {
                twoFactor = true
                setup = false
            } else {
                try await accept(response)
            }
        }
    }

    func verify(_ code: String) async {
        await run {
            guard let api else { throw NativeAPIError.closed }
            try await accept(
                api.request("/auth/2fa/verify", method: "POST", body: ["code": .string(code)], as: NativeIdentity.self))
        }
    }
    func cancelTwoFactor() {
        if !busy {
            twoFactor = false
            error = nil
        }
    }

    private func accept(_ identity: NativeIdentity) async throws {
        guard let user = identity.user, let permissions = identity.permissions else {
            throw NativeAPIError.invalidResponse
        }
        self.user = user
        self.permissions = permissions
        setup = false
        twoFactor = false
        page = .home
        try await reload()
    }

    func navigate(_ selected: NativePage) async {
        await run {
            page = selected
            selectedList = nil
            try await reload()
        }
    }
    func open(_ list: NativeShoppingList) async {
        await run {
            page = .shopping
            selectedList = list
            try await reload()
        }
    }
    func refresh() async { await run { try await reload() } }

    private func reload() async throws {
        guard let api else { throw NativeAPIError.closed }
        switch page {
        case .home: dashboard = try await api.request("/dashboard", as: NativeDashboard.self)
        case .tasks: tasks = try await api.request("/tasks", as: NativeEnvelope<[NativeTask]>.self).data
        case .notes: notes = try await api.request("/notes", as: NativeEnvelope<[NativeNote]>.self).data
        case .shopping:
            if let selectedList {
                items = try await api.request(
                    "/shopping/\(selectedList.id)/items", as: NativeEnvelope<[NativeShoppingItem]>.self
                ).data
            } else {
                lists = try await api.request("/shopping", as: NativeEnvelope<[NativeShoppingList]>.self).data
            }
        case .more: break
        }
    }

    func mutate(_ path: String, method: String, body: [String: NativeValue] = [:]) async -> Bool {
        await run {
            guard let api else { throw NativeAPIError.closed }
            let _: NativeEmpty = try await api.request(path, method: method, body: body, as: NativeEmpty.self)
            try await reload()
        }
    }

    func logout() async {
        await run {
            let revoked: Bool
            do {
                if let api {
                    let _: NativeEmpty = try await api.request("/auth/logout", method: "POST", as: NativeEmpty.self)
                }
                revoked = true
            } catch { revoked = false }
            await api?.close()
            clearLoadedData()
            try vault?.clear()
            if let address = try? ServerAddress(server), let storage = vault {
                api = try NativeAPI(server: address, saved: nil, persist: storage.save)
            }
            if !revoked { error = "Lokal abgemeldet. Die Abmeldung auf dem Server konnte nicht bestätigt werden." }
        }
    }

    func forget() async {
        guard !busy else { return }
        busy = true
        defer { busy = false }
        generation += 1
        await api?.close()
        clearLoadedData()
        do { try vault?.clear() } catch {
            self.error = NativeAPIError.unavailable.errorDescription
            return
        }
        api = nil
        vault = nil
        server = ""
        appName = "Yuvomi"
        setup = false
        passwordAllowed = true
        oidc = false
        error = nil
        UserDefaults.standard.removeObject(forKey: "native-origin")
    }

    private func clearLoadedData() {
        user = nil
        permissions = nil
        dashboard = nil
        tasks = []
        notes = []
        lists = []
        items = []
        selectedList = nil
        page = .home
        twoFactor = false
    }
}