import AppKit
import SwiftUI
import UniformTypeIdentifiers

@MainActor
@Observable
final class PostGeneratorViewModel {
    var draft = PostDraft()
    var selectedTab: PostGeneratorTab = .compose
    var isGenerating = false
    var errorMessage: String?
    var successMessage: String?
    var showImageImporter = false

    private let generationService: any PostGenerationServiceProtocol

    init(generationService: any PostGenerationServiceProtocol = MockPostGenerationService()) {
        self.generationService = generationService
    }

    var formattedSubreddit: String {
        let trimmed = draft.subreddit.trimmingCharacters(in: .whitespaces)
        guard !trimmed.isEmpty else { return "r/subreddit" }
        return trimmed.hasPrefix("r/") ? trimmed : "r/\(trimmed)"
    }

    var canGenerate: Bool {
        !draft.topic.trimmingCharacters(in: .whitespaces).isEmpty
            && !draft.subreddit.trimmingCharacters(in: .whitespaces).isEmpty
            && !isGenerating
    }

    var canAddPollOption: Bool {
        draft.pollOptions.count < 6
    }

    var canRemovePollOption: Bool {
        draft.pollOptions.count > 2
    }

    func selectPostType(_ type: RedditPostType) {
        draft.postType = type
        clearMessages()
    }

    func addPollOption() {
        guard canAddPollOption else { return }
        draft.pollOptions.append(PollOption())
    }

    func removePollOption(_ option: PollOption) {
        guard canRemovePollOption else { return }
        draft.pollOptions.removeAll { $0.id == option.id }
    }

    func setImage(from url: URL) {
        draft.imageFileURL = url
        clearMessages()
    }

    func removeImage() {
        draft.imageFileURL = nil
    }

    func generatePost() async {
        guard canGenerate else { return }

        isGenerating = true
        errorMessage = nil
        successMessage = nil

        do {
            let result = try await generationService.generatePost(from: draft)
            draft.title = result.title
            if draft.postType == .text || draft.postType == .poll {
                draft.body = result.body
            }
            if let flair = result.suggestedFlair, draft.flair.isEmpty {
                draft.flair = flair
            }
            successMessage = "Post generated successfully."
        } catch {
            errorMessage = error.localizedDescription
        }

        isGenerating = false
    }

    func copyToClipboard() {
        let content = exportText()
        NSPasteboard.general.clearContents()
        NSPasteboard.general.setString(content, forType: .string)
        successMessage = "Copied to clipboard."
        errorMessage = nil
    }

    func resetDraft() {
        draft = PostDraft()
        selectedTab = .compose
        clearMessages()
    }

    func exportText() -> String {
        var lines: [String] = []
        lines.append("Subreddit: \(formattedSubreddit)")
        lines.append("Type: \(draft.postType.title)")

        if !draft.title.isEmpty {
            lines.append("Title: \(draft.title)")
        }

        switch draft.postType {
        case .text:
            if !draft.body.isEmpty { lines.append("\n\(draft.body)") }
        case .image:
            if let url = draft.imageFileURL {
                lines.append("Image: \(url.lastPathComponent)")
            }
            if !draft.body.isEmpty { lines.append("Caption: \(draft.body)") }
        case .link:
            if !draft.linkURL.isEmpty { lines.append("URL: \(draft.linkURL)") }
            if !draft.body.isEmpty { lines.append("\n\(draft.body)") }
        case .video:
            if !draft.videoURL.isEmpty { lines.append("Video URL: \(draft.videoURL)") }
            if !draft.body.isEmpty { lines.append("\n\(draft.body)") }
        case .poll:
            lines.append("Duration: \(draft.pollDuration.label)")
            for (index, option) in draft.pollOptions.enumerated() where !option.text.isEmpty {
                lines.append("Option \(index + 1): \(option.text)")
            }
            if !draft.body.isEmpty { lines.append("\n\(draft.body)") }
        }

        var tags: [String] = []
        if draft.isNSFW { tags.append("NSFW") }
        if draft.isSpoiler { tags.append("Spoiler") }
        if draft.isOC { tags.append("OC") }
        if !tags.isEmpty { lines.append("Tags: \(tags.joined(separator: ", "))") }

        if !draft.flair.isEmpty { lines.append("Flair: \(draft.flair)") }

        return lines.joined(separator: "\n")
    }

    private func clearMessages() {
        errorMessage = nil
        successMessage = nil
    }
}