import Foundation

/// What `issue list` is narrowed to. Renders itself to the flags the
/// command accepts; an empty value sends no flag at all, since
/// `--search ""` is a different query from no search.
nonisolated struct IssueFilter: Equatable, Sendable {

    enum State: String, CaseIterable, Identifiable, Sendable {
        case open, closed, all
        var id: String { rawValue }
        var label: String { stateLabel(rawValue) }
    }

    var state: State = .open
    var search = ""
    var label: String?
    var assignee: String?
    var author: String?
    /// A milestone title, or the literal "none" for issues without one.
    var milestone: String?

    func flags() -> [String] {
        var flags = ["--state", state.rawValue]
        flags += filterFlag("--search", search)
        flags += filterFlag("--label", label)
        flags += filterFlag("--assignee", assignee)
        flags += filterFlag("--author", author)
        flags += filterFlag("--milestone", milestone)
        return flags
    }

    /// True when anything beyond the state picker is set, which is what
    /// decides whether the empty state blames the filters.
    var isNarrowed: Bool { flags().count > 2 }

    var emptyMessage: String {
        if isNarrowed {
            return state == .all
                ? "No issues match these filters."
                : "No \(state.rawValue) issues match these filters."
        }
        return state == .all ? "No issues." : "No \(state.rawValue) issues."
    }
}

/// One flag, or nothing when the value is absent or blank. Shared by
/// both filters, so it is named for what it does rather than taking the
/// bare name `flag` in the module namespace.
nonisolated func filterFlag(_ name: String, _ value: String?) -> [String] {
    guard let value else { return [] }
    let trimmed = value.trimmingCharacters(in: .whitespaces)
    return trimmed.isEmpty ? [] : [name, trimmed]
}