import Foundation

/// Mac-local answer model for the shared `AskRequest` DTO.
///
/// iOS has richer ask-card presentation code in the iOS target. The Mac client
/// keeps a small encoder here so selected-session ask handling can stay in the
/// Mac target without pulling iOS view code into the desktop app.
enum MacAskAnswer: Equatable, Sendable {
    case single(String)
    case multi(Set<String>)
    case custom(String)
}

enum MacAskResponseEncoder {
    static let inlineQuestionId = "extension-ui"
    static let confirmValue = "__oppi_confirm"
    static let cancelValue = "__oppi_cancel"

    static func encode(_ answers: [String: MacAskAnswer]) -> String {
        var result: [String: Any] = [:]
        for (key, answer) in answers {
            switch answer {
            case .single(let value):
                result[key] = value
            case .multi(let values):
                result[key] = Array(values).sorted()
            case .custom(let text):
                result[key] = text
            }
        }

        guard let data = try? JSONSerialization.data(
            withJSONObject: result,
            options: [.sortedKeys]
        ) else {
            return "{}"
        }
        return String(data: data, encoding: .utf8) ?? "{}"
    }

    static func responseMessage(request: AskRequest, draft: MacAskResponseDraft) -> ClientMessage {
        switch request.responseEncoding {
        case .ask:
            return .extensionUIResponse(id: request.id, value: draft.encodedValue())

        case .extensionSelect:
            guard case .single(let value) = draft.answers[inlineQuestionId] else {
                return .extensionUIResponse(id: request.id, cancelled: true)
            }
            return .extensionUIResponse(id: request.id, value: value)

        case .extensionConfirm:
            if draft.answers[inlineQuestionId] == .single(confirmValue) {
                return .extensionUIResponse(id: request.id, confirmed: true)
            }
            return .extensionUIResponse(id: request.id, cancelled: true)

        case .extensionInput:
            switch draft.answers[inlineQuestionId] {
            case .custom(let value), .single(let value):
                return .extensionUIResponse(id: request.id, value: value)
            case .multi, nil:
                return .extensionUIResponse(id: request.id, cancelled: true)
            }
        }
    }
}

struct MacAskResponseDraft: Equatable, Sendable {
    private(set) var answers: [String: MacAskAnswer] = [:]

    var isEmpty: Bool { answers.isEmpty }

    mutating func toggle(_ option: AskOption, question: AskQuestion) {
        if question.multiSelect {
            let existing: Set<String>
            if case .multi(let values) = answers[question.id] {
                existing = values
            } else {
                existing = []
            }
            var next = existing
            if next.contains(option.value) {
                next.remove(option.value)
            } else {
                next.insert(option.value)
            }
            answers[question.id] = next.isEmpty ? nil : .multi(next)
        } else {
            answers[question.id] = .single(option.value)
        }
    }

    mutating func setCustom(_ text: String, question: AskQuestion) {
        let trimmed = text.trimmingCharacters(in: .whitespacesAndNewlines)
        answers[question.id] = trimmed.isEmpty ? nil : .custom(trimmed)
    }

    func isSelected(_ option: AskOption, question: AskQuestion) -> Bool {
        guard let answer = answers[question.id] else { return false }
        switch answer {
        case .single(let value):
            return value == option.value
        case .multi(let values):
            return values.contains(option.value)
        case .custom:
            return false
        }
    }

    func encodedValue() -> String {
        MacAskResponseEncoder.encode(answers)
    }
}