import Foundation
import Observation

/// Whose label or milestone set a screen manages. A repository's is
/// `label <verb> <repo>`; an org's is `org label <verb> <org>`, and its
/// rows are seen by every repository under the org (v1.19.0).
nonisolated enum LabelOwner: Hashable, Sendable {
    case repo(String)
    case org(String)

    /// The command prefix for `noun` (`label` or `milestone`) and `verb`.
    func argv(_ noun: String, _ verb: String) -> [String] {
        switch self {
        case .repo(let path): [noun, verb, path]
        case .org(let name): ["org", noun, verb, name]
        }
    }

    var isOrg: Bool {
        if case .org = self { return true }
        return false
    }
}

/// `label list`, plus the two commands that change the set: `label set`
/// creates one or recolours it, `label remove` takes it off the owner and
/// off every issue that carried it.
@Observable
@MainActor
final class LabelListViewModel {

    private(set) var state: LoadState<[IssueLabel]> = .loading
    private(set) var actionError: String?
    private(set) var working = false

    private let client: GitbayClient
    let owner: LabelOwner

    init(client: GitbayClient, owner: LabelOwner) {
        self.client = client
        self.owner = owner
    }

    convenience init(client: GitbayClient, repoPath: String) {
        self.init(client: client, owner: .repo(repoPath))
    }

    func load() async {
        state = .loading
        do {
            let labels = try await client.readList(
                owner.argv("label", "list"), of: IssueLabel.self
            )
            state = labels.isEmpty ? .empty("No labels yet.") : .loaded(labels)
        } catch {
            state = .from(error)
        }
    }

    /// Create a label or set its colour. A nil colour omits `--color`
    /// entirely, which the server reads as "make sure it exists" and
    /// leaves any colour it already had; an empty string clears it.
    func setLabel(_ name: String, color: String?) async {
        var argv = owner.argv("label", "set") + [name]
        if let color { argv.append(contentsOf: ["--color", color]) }
        await perform(argv)
    }

    func remove(_ name: String) async {
        await perform(owner.argv("label", "remove") + [name])
    }

    private func perform(_ argv: [String]) async {
        working = true
        actionError = nil
        defer { working = false }
        do {
            try await client.run(argv)
            await load()
        } catch let error as GitbayError {
            actionError = error.userFacingMessage
        } catch {
            actionError = GitbayError.transport(error).userFacingMessage
        }
    }
}