import Foundation
import Observation
import OrgSocialKit

@Observable @MainActor
final class PollVoteViewModel {

    var isPosting = false
    var errorMessage: String?
    /// The option the user voted for on the target poll, or nil if not voted.
    var votedOption: String?
    /// RFC 3339 timestamp of the vote post in the user's own feed, kept so we
    /// can locate and delete it on unvote.
    var votedTimestamp: String?

    /// Restores the voted state for `pollURL`. Reads `OwnInteractionCache`
    /// first for an instant, relay-independent answer; falls back to scanning
    /// the user's own feed so votes cast from another client still register.
    func loadExistingVote(for pollURL: String) async {
        if let cached = OwnInteractionCache.shared.vote(for: pollURL) {
            votedOption = cached.option
            votedTimestamp = cached.timestamp
            return
        }
        guard let feedURL = publicFeedURL else { return }
        do {
            let content = try await FeedFetcher().fetch(from: feedURL, bypassCache: false)
            let profile = OrgSocialParser().parse(content)
            let match = profile.posts.first { post in
                post.replyTo == pollURL &&
                post.pollOption?.isEmpty == false &&
                post.text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
            }
            if let match, let option = match.pollOption {
                votedOption = option
                votedTimestamp = match.timestamp
                OwnInteractionCache.shared.recordVote(
                    pollURL: pollURL, option: option, timestamp: match.timestamp
                )
            }
        } catch {
            // Silent: UI will just show the "open to vote" state.
        }
    }

    func vote(for option: String, on pollURL: String) async {
        guard let feedURL = publicFeedURL, let uploader = makeUploader() else {
            errorMessage = "Configure your feed in Settings before voting."
            return
        }
        isPosting = true
        errorMessage = nil
        defer { isPosting = false }

        do {
            let content = try await FeedFetcher().fetch(from: feedURL, bypassCache: true)
            let options = NewPostOptions.vote(for: option, on: pollURL)
            let writer = PostWriter()
            let date = Date()
            let (updated, _) = try writer.appendPost(to: content, feedURL: feedURL, options: options, date: date)
            try await uploader.upload(content: updated)
            FollowCoordinator.shared.updateCachedContent(updated)
            let ts = writer.generateTimestamp(for: date)
            votedOption = option
            votedTimestamp = ts
            OwnInteractionCache.shared.recordVote(pollURL: pollURL, option: option, timestamp: ts)
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    /// Deletes the user's vote post on `pollURL`. If `votedTimestamp` is unset
    /// the own feed is scanned to locate the vote.
    func unvote(from pollURL: String) async {
        guard let feedURL = publicFeedURL, let uploader = makeUploader() else {
            errorMessage = "Configure your feed in Settings before removing the vote."
            return
        }
        isPosting = true
        errorMessage = nil
        defer { isPosting = false }

        do {
            let content = try await FeedFetcher().fetch(from: feedURL, bypassCache: true)
            let timestamp: String
            if let known = votedTimestamp {
                timestamp = known
            } else {
                let profile = OrgSocialParser().parse(content)
                guard let match = profile.posts.first(where: { post in
                    post.replyTo == pollURL &&
                    post.pollOption?.isEmpty == false &&
                    post.text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
                }) else {
                    errorMessage = "Vote post not found in your feed."
                    return
                }
                timestamp = match.timestamp
            }
            let writer = PostWriter()
            let updated: String
            do {
                updated = try writer.deletePost(timestamp: timestamp, from: content)
            } catch PostWriterError.postNotFound {
                votedOption = nil
                votedTimestamp = nil
                OwnInteractionCache.shared.removeVote(pollURL: pollURL)
                return
            }
            try await uploader.upload(content: updated)
            FollowCoordinator.shared.updateCachedContent(updated)
            votedOption = nil
            votedTimestamp = nil
            OwnInteractionCache.shared.removeVote(pollURL: pollURL)
        } catch {
            errorMessage = error.localizedDescription
        }
    }

    private var publicFeedURL: URL? {
        guard let raw = UserDefaults.standard.string(forKey: "publicFeedURL"),
              let url = URL(string: raw),
              url.scheme?.hasPrefix("http") == true else { return nil }
        return url
    }

    private func makeUploader() -> (any FeedUploader)? { UploaderFactory.makeUploader() }
}