import Foundation
import Observation

/// `mr create <repo> --source <b> --target <b> --title <t> --file -`.
///
/// Branch names are typed, not picked: no command lists branches yet
/// (krz/gitbay#45). The target prefills with the default branch from
/// `repo show`.
@Observable
@MainActor
final class MRCreateViewModel {

    private(set) var working = false
    private(set) var errorMessage: String?
    private(set) var defaultBranch: String?

    private let client: GitbayClient
    let repoPath: String

    init(client: GitbayClient, repoPath: String) {
        self.client = client
        self.repoPath = repoPath
    }

    func loadDefaultBranch() async {
        guard defaultBranch == nil else { return }
        defaultBranch = (try? await client.read(
            ["repo", "show", repoPath], as: RepoDetail.self
        ))?.defaultBranch
    }

    nonisolated private struct Created: Decodable, Sendable {
        let number: Int64
    }

    func create(source: String, target: String, title: String, body: String) async -> Int64? {
        working = true
        errorMessage = nil
        defer { working = false }
        do {
            var argv = ["mr", "create", repoPath,
                        "--source", source, "--target", target, "--title", title]
            var stdin: String?
            if !body.isEmpty {
                argv.append(contentsOf: ["--file", "-"])
                stdin = body
            }
            let created = try await client.run(argv, stdin: stdin, as: Created.self)
            return created?.number
        } catch let error as GitbayError {
            errorMessage = error.userFacingMessage
        } catch {
            errorMessage = GitbayError.transport(error).userFacingMessage
        }
        return nil
    }
}