import Foundation
import Observation

/// `mr range-diff <owner/name> <n> --from <sha> --to <sha>` — git's
/// range-diff between two heads the merge request has had, as text.
@Observable
@MainActor
final class RangeDiffViewModel {

    private(set) var state: LoadState<String> = .loading

    private let client: GitbayClient
    let repoPath: String
    let number: Int64
    let from: String
    let to: String

    init(client: GitbayClient, repoPath: String, number: Int64, from: String, to: String) {
        self.client = client
        self.repoPath = repoPath
        self.number = number
        self.from = from
        self.to = to
    }

    func load() async {
        state = .loading
        do {
            let text = try await client.readText(
                ["mr", "range-diff", repoPath, String(number), "--from", from, "--to", to])
            state = text.isEmpty ? .empty("The two revisions carry the same commits.") : .loaded(text)
        } catch {
            state = .from(error)
        }
    }
}