import Foundation

// TODO: add versioning (XEP-0237) if needed
// TODO: implement error catching
final class RosterModule: XmppModule {
    let id = "Roseter module"

    private weak var storage: (any XMPPStorage)?
    private var fullReqId = ""

    init(_ storage: any XMPPStorage) {
        self.storage = storage
    }

    func reduce(oldState: ClientState, with _: Event) -> ClientState {
        oldState
    }

    func process(state: ClientState, with event: Event) async -> Event? {
        switch event {
        case .streamReady:
            return .requestRoster

        case .requestRoster:
            let req = Stanza.iqGet(
                from: state.jid.full,
                payload: XMLElement(name: "query", xmlns: "jabber:iq:roster", attributes: [:], content: nil, nodes: [])
            )
            if let req {
                fullReqId = req.id ?? "???"
                return .stanzaOutbound(req)
            } else {
                return nil
            }

        case .stanzaInbound(let stanza):
            if let query = stanza.wrapped.nodes.first(where: { $0.name == "query" }), query.xmlns == "jabber:iq:roster" {
                return await processRoster(state: state, stanza: stanza)
            } else {
                return nil
            }

        case .addRosterItem(let jidStr):
            return updRoster(state: state, target: jidStr, remove: false)

        case .deleteRosterItem(let jidStr):
            return updRoster(state: state, target: jidStr, remove: true)

        default:
            return nil
        }
    }
}

private extension RosterModule {
    private func processRoster(state: ClientState, stanza: Stanza) async -> Event? {
        // get inner query
        guard let query = stanza.wrapped.nodes.first(where: { $0.name == "query" })
        else { return nil }

        // get exists roster items
        var existItems: [RosterItem] = []
        if let data = await storage?.getRoster(jid: state.jid), let decoded = try? JSONDecoder().decode([XMLElement].self, from: data) {
            existItems = decoded.compactMap { RosterItem(wrap: $0, owner: state.jid) }
        }

        // process push (.set from server)
        if stanza.type == .iq(.set) {
            guard
                let item = query.nodes.first(where: { $0.name == "item" }),
                let new = RosterItem(wrap: item, owner: state.jid)
            else { return nil }
            existItems = existItems.filter { $0.jid != new.jid }
            existItems.append(new)
            guard let data = try? JSONEncoder().encode(existItems.map { $0.wrapped }) else { return nil }
            await storage?.setRoster(jid: state.jid, roster: data)
            return .rosterUpdated

            // process .result from server
        } else if stanza.type == .iq(.result) {
            // process full list
            if stanza.id == fullReqId {
                let items = query.nodes.filter { $0.name == "item" }
                guard let data = try? JSONEncoder().encode(items) else { return nil }
                await storage?.setRoster(jid: state.jid, roster: data)

                // process changed item
            } else {
                // TODO: Fix removing item!
                // guard
                //     let item = query.nodes.first(where: { $0.name == "item" }),
                //     let new = RosterItem(wrap: item, owner: state.jid)
                // else { return nil }
                // existItems = existItems.filter { $0.jid != new.jid }
                // if new.subsription != .remove {
                //     existItems.append(new)
                // } else {
                //     print("REMOVED!!!")
                // }
                // guard let data = try? JSONEncoder().encode(existItems.map { $0.wrapped }) else { return nil }
                // await storage?.setRoster(jid: state.jid, roster: data)
            }
            return .rosterUpdated
        } else {
            return nil
        }
    }

    private func updRoster(state: ClientState, target: String, remove: Bool) -> Event? {
        var attributes = ["jid": target]
        if remove {
            attributes["subcription"] = "remove"
        }
        let item = XMLElement(name: "item", xmlns: "jabber:iq:roster", attributes: attributes, content: nil, nodes: [])
        let query = XMLElement(name: "query", xmlns: "jabber:iq:roster", attributes: [:], content: nil, nodes: [item])
        if let req = Stanza.iqSet(from: state.jid.full, payload: query) {
            return .stanzaOutbound(req)
        } else {
            return nil
        }
    }
}