import AppKit
import SwiftUI
import UniformTypeIdentifiers

struct PostGeneratorView: View {
    @Environment(\.requirePremiumAccess) private var requirePremiumAccess
    @Bindable var viewModel: PostGeneratorViewModel

    private enum Layout {
        static let horizontalPadding: CGFloat = 24
        static let columnWidth: CGFloat = 300
        static let columnSpacing: CGFloat = 20
        static let sectionSpacing: CGFloat = 12
        static let imageUploadHeight: CGFloat = 140
    }

    var body: some View {
        VStack(spacing: 0) {
            header
            messageBanners

            ScrollView {
                VStack(alignment: .leading, spacing: 12) {
                    tabBar

                    PostPageBoundary {
                        switch viewModel.selectedTab {
                        case .compose:
                            composeContent
                        case .preview:
                            previewContent
                        }
                    }
                }
                .padding(.horizontal, Layout.horizontalPadding)
                .padding(.top, 12)
                .padding(.bottom, 24)
            }
        }
        .background(AppTheme.background)
        .fileImporter(
            isPresented: $viewModel.showImageImporter,
            allowedContentTypes: [.image],
            allowsMultipleSelection: false
        ) { result in
            switch result {
            case .success(let urls):
                if let url = urls.first {
                    viewModel.setImage(from: url)
                }
            case .failure(let error):
                viewModel.handleImageImportFailure(error)
            }
        }
        .alert("Replace existing content?", isPresented: $viewModel.showOverwriteConfirmation) {
            Button("Cancel", role: .cancel) {
                viewModel.cancelOverwriteConfirmation()
            }
            Button("Replace", role: .destructive) {
                guard !viewModel.usesLiveAI || requirePremiumAccess() else { return }
                Task { await viewModel.confirmOverwriteAndGenerate() }
            }
        } message: {
            Text("Generating will replace your current title, body, and poll options.")
        }
        .onChange(of: viewModel.draft.topic) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.subreddit) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.title) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.body) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.linkURL) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.videoURL) { _, _ in viewModel.notifyDraftEdited() }
        .onChange(of: viewModel.draft.flair) { _, _ in viewModel.notifyDraftEdited() }
    }

    // MARK: - Header

    private var header: some View {
        VStack(spacing: 0) {
            HStack(spacing: 14) {
                ModernSidebarIconView(kind: .postGenerator, size: 40)

                VStack(alignment: .leading, spacing: 2) {
                    HStack(spacing: 6) {
                        Text("Post Generator")
                            .font(.system(size: 18, weight: .semibold))
                            .foregroundStyle(AppTheme.textPrimary)

                        if viewModel.hasDraftChanges {
                            Circle()
                                .fill(AppTheme.accentOrange)
                                .frame(width: 6, height: 6)
                                .help("Draft has unsaved edits")
                        }
                    }

                    Text(viewModel.usesLiveAI ? "Create Reddit-ready posts with AI" : "Create Reddit-ready posts with AI templates")
                        .font(.system(size: 11))
                        .foregroundStyle(AppTheme.textSecondary)
                }

                Spacer()

                headerActions
            }
            .padding(.horizontal, Layout.horizontalPadding)
            .padding(.vertical, 16)

            FullWidthDivider()
        }
    }

    @ViewBuilder
    private var messageBanners: some View {
        if let error = viewModel.errorMessage {
            PostGeneratorMessageBanner(message: error, isError: true)
                .padding(.horizontal, Layout.horizontalPadding)
                .padding(.top, 8)
        } else if let success = viewModel.successMessage {
            PostGeneratorMessageBanner(message: success, isError: false)
                .padding(.horizontal, Layout.horizontalPadding)
                .padding(.top, 8)
        }
    }

    private var headerActions: some View {
        HStack(spacing: 8) {
            Button {
                viewModel.resetDraft()
            } label: {
                Label("Reset", systemImage: "arrow.counterclockwise")
                    .font(.system(size: 11, weight: .medium))
            }
            .buttonStyle(AppSecondaryButtonStyle())

            Button {
                viewModel.copyToClipboard()
            } label: {
                Label("Copy", systemImage: "doc.on.doc")
                    .font(.system(size: 11, weight: .medium))
            }
            .buttonStyle(AppSecondaryButtonStyle())
            .disabled(!viewModel.canExport)

            Button {
                guard !viewModel.usesLiveAI || requirePremiumAccess() else { return }
                Task { await viewModel.generatePost() }
            } label: {
                HStack(spacing: 6) {
                    if viewModel.isGenerating {
                        ProgressView()
                            .controlSize(.small)
                            .tint(.white)
                    } else {
                        Image(systemName: "sparkles")
                            .font(.system(size: 11, weight: .semibold))
                    }
                    Text(viewModel.isGenerating ? "Generating…" : "Generate")
                        .font(.system(size: 11, weight: .semibold))
                }
                .foregroundStyle(.white)
                .padding(.horizontal, 14)
                .padding(.vertical, 8)
                .background(viewModel.canGenerate ? AppTheme.accentPurple : AppTheme.accentPurple.opacity(0.4))
                .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .buttonStyle(AppPrimaryButtonStyle())
            .disabled(!viewModel.canGenerate)
        }
    }

    // MARK: - Tab Bar

    private var tabBar: some View {
        ToolSegmentedTabBar(
            selection: $viewModel.selectedTab,
            accentColor: AppTheme.accentPurple,
            width: 220
        )
    }

    // MARK: - Compose

    private var composeContent: some View {
        composeColumns
    }

    private var composeColumns: some View {
        HStack(alignment: .top, spacing: Layout.columnSpacing) {
            composeColumn(title: "Configuration", icon: "slider.horizontal.3") {
                configurationPanel
            }
            .frame(width: Layout.columnWidth)
            .layoutPriority(1)

            Rectangle()
                .fill(AppTheme.border)
                .frame(width: 1)
                .padding(.vertical, 2)

            composeColumn(title: "Post Content", icon: "doc.text") {
                editorPanel
            }
            .frame(minWidth: 0, maxWidth: .infinity)
            .layoutPriority(0)
        }
    }

    private func composeColumn<Content: View>(
        title: String,
        icon: String,
        @ViewBuilder content: () -> Content
    ) -> some View {
        VStack(alignment: .leading, spacing: Layout.sectionSpacing) {
            composeSectionHeader(title: title, icon: icon)
            content()
        }
    }

    private func composeSectionHeader(title: String, icon: String) -> some View {
        HStack(spacing: 6) {
            Image(systemName: icon)
                .font(.system(size: 10, weight: .semibold))
                .foregroundStyle(AppTheme.accentPurpleLight)
            Text(title)
                .font(.system(size: 11, weight: .semibold))
                .foregroundStyle(AppTheme.textSecondary)
        }
        .textCase(.uppercase)
        .tracking(0.4)
    }

    private var configurationPanel: some View {
        VStack(spacing: Layout.sectionSpacing) {
            PostFormCard(title: "Post Type", subtitle: "Choose how you want to post") {
                PostTypePicker(selectedType: Binding(
                    get: { viewModel.draft.postType },
                    set: { viewModel.selectPostType($0) }
                ))
            }

            PostFormCard(title: "Target Subreddit", subtitle: "Where will this be posted?") {
                VStack(alignment: .leading, spacing: 6) {
                    PostFormField(
                        label: "Subreddit",
                        placeholder: "technology",
                        text: $viewModel.draft.subreddit,
                        prefix: "r/"
                    )

                    if !viewModel.draft.subreddit.isEmpty,
                       !PostDraftValidator.isValidSubreddit(viewModel.draft.subreddit) {
                        validationHint("Use 3–21 characters: letters, numbers, underscores only.")
                    }
                }
            }

            PostFormCard(title: "AI Settings", subtitle: "Guide the tone and topic") {
                VStack(alignment: .leading, spacing: 12) {
                    PostFormField(
                        label: "Topic / Keywords",
                        placeholder: "e.g. macOS productivity tips",
                        text: $viewModel.draft.topic
                    )

                    VStack(alignment: .leading, spacing: 6) {
                        Text("Tone")
                            .font(.system(size: 10, weight: .medium))
                            .foregroundStyle(AppTheme.textTertiary)
                        TonePicker(selectedTone: $viewModel.draft.tone)
                    }
                }
            }

            PostFormCard(title: "Labels", subtitle: "Tags and optional flair") {
                VStack(alignment: .leading, spacing: 12) {
                    HStack(spacing: 8) {
                        PostTagToggle(
                            title: "NSFW",
                            systemImage: "exclamationmark.triangle.fill",
                            activeColor: Color(hex: 0xEF4444),
                            isOn: $viewModel.draft.isNSFW
                        )
                        .frame(maxWidth: .infinity)

                        PostTagToggle(
                            title: "Spoiler",
                            systemImage: "eye.slash.fill",
                            activeColor: AppTheme.textSecondary,
                            isOn: $viewModel.draft.isSpoiler
                        )
                        .frame(maxWidth: .infinity)

                        PostTagToggle(
                            title: "OC",
                            systemImage: "star.fill",
                            activeColor: AppTheme.accentGreen,
                            isOn: $viewModel.draft.isOC
                        )
                        .frame(maxWidth: .infinity)
                    }

                    PostFormField(
                        label: "Flair",
                        placeholder: "Discussion, Question, Meme…",
                        text: $viewModel.draft.flair
                    )
                }
            }
        }
    }

    private var editorPanel: some View {
        VStack(spacing: Layout.sectionSpacing) {
            PostFormCard(title: "Title", subtitle: "Required for all post types") {
                PostFormField(
                    label: "Post Title",
                    placeholder: "An engaging title for your post",
                    text: $viewModel.draft.title
                )
            }

            postTypeEditor
                .frame(minHeight: 260, alignment: .top)

            characterCountFooter
        }
    }

    @ViewBuilder
    private var postTypeEditor: some View {
        switch viewModel.draft.postType {
        case .text:
            textPostEditor
        case .image:
            imagePostEditor
        case .link:
            linkPostEditor
        case .video:
            videoPostEditor
        case .poll:
            pollPostEditor
        }
    }

    private var textPostEditor: some View {
        PostFormCard(title: "Body", subtitle: "Markdown supported — **bold**, *italic*, links") {
            PostFormTextEditor(
                label: "Post Body",
                placeholder: "Write your post content here…",
                text: $viewModel.draft.body,
                minHeight: 220
            )
        }
    }

    private var imagePostEditor: some View {
        PostFormCard(title: "Image", subtitle: "Upload an image for your post") {
            VStack(alignment: .leading, spacing: 12) {
                imageUploadArea

                PostFormTextEditor(
                    label: "Caption (optional)",
                    placeholder: "Add context for your image…",
                    text: $viewModel.draft.body,
                    minHeight: 80
                )
            }
        }
    }

    private var linkPostEditor: some View {
        PostFormCard(title: "Link", subtitle: "Share a URL with the community") {
            VStack(alignment: .leading, spacing: 12) {
                PostFormField(
                    label: "URL",
                    placeholder: "https://example.com/article",
                    text: $viewModel.draft.linkURL
                )

                if !viewModel.draft.linkURL.isEmpty,
                   !PostDraftValidator.isValidHTTPURL(viewModel.draft.linkURL) {
                    validationHint("Enter a valid http or https URL.")
                }

                PostFormTextEditor(
                    label: "Description (optional)",
                    placeholder: "Why are you sharing this link?",
                    text: $viewModel.draft.body,
                    minHeight: 100
                )
            }
        }
    }

    private var videoPostEditor: some View {
        PostFormCard(title: "Video", subtitle: "Link to YouTube, Vimeo, or direct video URL") {
            VStack(alignment: .leading, spacing: 12) {
                PostFormField(
                    label: "Video URL",
                    placeholder: "https://youtube.com/watch?v=…",
                    text: $viewModel.draft.videoURL
                )

                if !viewModel.draft.videoURL.isEmpty,
                   !PostDraftValidator.isValidHTTPURL(viewModel.draft.videoURL) {
                    validationHint("Enter a valid http or https URL.")
                }

                PostFormTextEditor(
                    label: "Description (optional)",
                    placeholder: "Add context for your video…",
                    text: $viewModel.draft.body,
                    minHeight: 100
                )
            }
        }
    }

    private var pollPostEditor: some View {
        PostFormCard(title: "Poll", subtitle: "2–6 options, community votes") {
            VStack(alignment: .leading, spacing: 12) {
                ForEach(Array(viewModel.draft.pollOptions.enumerated()), id: \.element.id) { index, option in
                    HStack(spacing: 8) {
                        PostFormField(
                            label: "Option \(index + 1)",
                            placeholder: "Enter poll option",
                            text: Binding(
                                get: { option.text },
                                set: { viewModel.updatePollOption(id: option.id, text: $0) }
                            )
                        )

                        if viewModel.canRemovePollOption {
                            Button {
                                viewModel.removePollOption(option)
                            } label: {
                                Image(systemName: "minus.circle.fill")
                                    .font(.system(size: 14))
                                    .foregroundStyle(Color(hex: 0xEF4444).opacity(0.8))
                            }
                            .buttonStyle(AppPlainButtonStyle())
                            .hoverOverlay(cornerRadius: 7)
                            .padding(.top, 18)
                        }
                    }
                }

                if viewModel.canAddPollOption {
                    Button {
                        viewModel.addPollOption()
                    } label: {
                        Label("Add Option", systemImage: "plus.circle.fill")
                            .font(.system(size: 11, weight: .medium))
                            .foregroundStyle(AppTheme.accentPurpleLight)
                    }
                    .buttonStyle(AppPlainButtonStyle())
                    .hoverOverlay(cornerRadius: 6)
                }

                VStack(alignment: .leading, spacing: 6) {
                    Text("Poll Duration")
                        .font(.system(size: 10, weight: .medium))
                        .foregroundStyle(AppTheme.textTertiary)

                    HStack(spacing: 8) {
                        ForEach(PollDuration.allCases) { duration in
                            Button {
                                viewModel.draft.pollDuration = duration
                                viewModel.notifyDraftEdited()
                            } label: {
                                Text(duration.label)
                                    .font(.system(size: 10, weight: .semibold))
                                    .foregroundStyle(
                                        viewModel.draft.pollDuration == duration ? .white : AppTheme.textSecondary
                                    )
                                    .frame(maxWidth: .infinity)
                                    .padding(.vertical, 7)
                                    .background(
                                        RoundedRectangle(cornerRadius: 7)
                                            .fill(
                                                viewModel.draft.pollDuration == duration
                                                    ? AppTheme.accentPurple
                                                    : AppTheme.panelBackground
                                            )
                                    )
                                    .overlay(
                                        RoundedRectangle(cornerRadius: 7)
                                            .stroke(AppTheme.cardBorder, lineWidth: 1)
                                    )
                            }
                            .buttonStyle(AppPlainButtonStyle())
                            .hoverOverlay(cornerRadius: 7)
                        }
                    }
                }

                PostFormTextEditor(
                    label: "Context (optional)",
                    placeholder: "Explain why you're running this poll…",
                    text: $viewModel.draft.body,
                    minHeight: 80
                )
            }
        }
    }

    @ViewBuilder
    private var imageUploadArea: some View {
        Group {
            if let url = viewModel.draft.imageFileURL, let nsImage = NSImage(contentsOf: url) {
                ZStack(alignment: .topTrailing) {
                    Image(nsImage: nsImage)
                        .resizable()
                        .scaledToFit()
                        .frame(maxWidth: .infinity, maxHeight: Layout.imageUploadHeight)
                        .frame(maxWidth: .infinity, maxHeight: Layout.imageUploadHeight)
                        .clipped()

                    Button {
                        viewModel.removeImage()
                    } label: {
                        Image(systemName: "xmark.circle.fill")
                            .font(.system(size: 18))
                            .foregroundStyle(.white)
                            .shadow(radius: 2)
                    }
                    .buttonStyle(AppPlainButtonStyle())
                    .hoverOverlay(cornerRadius: 8)
                    .padding(8)
                }
            } else {
                Button {
                    viewModel.showImageImporter = true
                } label: {
                    VStack(spacing: 8) {
                        Image(systemName: "photo.badge.plus")
                            .font(.system(size: 24))
                            .foregroundStyle(AppTheme.accentPurpleLight)
                        Text("Click to upload image")
                            .font(.system(size: 11, weight: .medium))
                            .foregroundStyle(AppTheme.textSecondary)
                        Text("PNG, JPG, GIF, WebP")
                            .font(.system(size: 9))
                            .foregroundStyle(AppTheme.textTertiary)
                    }
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                    .background(AppTheme.panelBackground)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .overlay(
                        RoundedRectangle(cornerRadius: 8)
                            .strokeBorder(
                                AppTheme.accentPurple.opacity(0.3),
                                style: StrokeStyle(lineWidth: 1, dash: [6, 4])
                            )
                    )
                }
                .buttonStyle(AppPlainButtonStyle())
                .hoverCard(cornerRadius: 8)
            }
        }
        .frame(maxWidth: .infinity)
        .frame(height: Layout.imageUploadHeight)
        .clipShape(RoundedRectangle(cornerRadius: 8))
    }

    private var characterCountFooter: some View {
        HStack(spacing: 12) {
            Text(titleCharacterCount)
                .font(.system(size: 10, weight: .medium, design: .monospaced))
                .foregroundStyle(
                    viewModel.draft.title.count > PostDraftValidator.maxTitleLength
                        ? Color(hex: 0xF87171)
                        : AppTheme.textTertiary
                )

            if !viewModel.draft.body.isEmpty {
                Text("·")
                    .foregroundStyle(AppTheme.textTertiary)

                Text(bodyCharacterCount)
                    .font(.system(size: 10, weight: .medium, design: .monospaced))
                    .foregroundStyle(
                        viewModel.draft.body.count > PostDraftValidator.maxBodyLength
                            ? Color(hex: 0xF87171)
                            : AppTheme.textTertiary
                    )
            }

            Spacer()

            Text("Reddit limits: 300 title · 40,000 body")
                .font(.system(size: 10))
                .foregroundStyle(AppTheme.textTertiary)
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 9)
        .background(
            RoundedRectangle(cornerRadius: AppTheme.cornerRadiusSmall)
                .fill(AppTheme.cardBackground)
                .overlay(
                    RoundedRectangle(cornerRadius: AppTheme.cornerRadiusSmall)
                        .stroke(AppTheme.cardBorder, lineWidth: 1)
                )
        )
    }

    private var titleCharacterCount: String {
        "\(viewModel.draft.title.count) / \(PostDraftValidator.maxTitleLength) title"
    }

    private var bodyCharacterCount: String {
        "\(viewModel.draft.body.count) / \(PostDraftValidator.maxBodyLength) body"
    }

    // MARK: - Preview

    private var previewContent: some View {
        VStack(alignment: .leading, spacing: Layout.columnSpacing) {
            composeSectionHeader(title: "Live Preview", icon: "eye")

            HStack {
                Spacer(minLength: 0)

                VStack(spacing: Layout.sectionSpacing) {
                    RedditPostPreviewCard(
                        draft: viewModel.draft,
                        formattedSubreddit: viewModel.formattedSubreddit
                    )

                    previewMetadata
                }
                .frame(maxWidth: 560)

                Spacer(minLength: 0)
            }
        }
    }

    private var previewMetadata: some View {
        VStack(alignment: .leading, spacing: 0) {
            metadataRow(label: "Type", value: viewModel.draft.postType.title)
            metadataDivider
            metadataRow(label: "Subreddit", value: viewModel.formattedSubreddit)
            metadataDivider
            metadataRow(label: "Tone", value: viewModel.draft.tone.title)
            metadataDivider
            metadataRow(label: "Engine", value: viewModel.usesLiveAI ? "AI" : "Local templates")

            if viewModel.draft.isNSFW || viewModel.draft.isSpoiler || viewModel.draft.isOC {
                metadataDivider
                metadataRow(
                    label: "Tags",
                    value: [
                        viewModel.draft.isNSFW ? "NSFW" : nil,
                        viewModel.draft.isSpoiler ? "Spoiler" : nil,
                        viewModel.draft.isOC ? "OC" : nil,
                    ]
                    .compactMap { $0 }
                    .joined(separator: ", ")
                )
            }
        }
        .padding(14)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(
            RoundedRectangle(cornerRadius: AppTheme.cornerRadiusSmall)
                .fill(AppTheme.cardBackground)
                .overlay(
                    RoundedRectangle(cornerRadius: AppTheme.cornerRadiusSmall)
                        .stroke(AppTheme.cardBorder, lineWidth: 1)
                )
        )
    }

    private var metadataDivider: some View {
        Rectangle()
            .fill(AppTheme.border)
            .frame(height: 1)
            .padding(.vertical, 6)
    }

    private func metadataRow(label: String, value: String) -> some View {
        HStack(alignment: .top, spacing: 12) {
            Text(label)
                .font(.system(size: 10, weight: .medium))
                .foregroundStyle(AppTheme.textTertiary)
                .frame(width: 72, alignment: .leading)
            Text(value)
                .font(.system(size: 10))
                .foregroundStyle(AppTheme.textSecondary)
                .fixedSize(horizontal: false, vertical: true)
        }
    }

    private func validationHint(_ message: String) -> some View {
        HStack(spacing: 4) {
            Image(systemName: "exclamationmark.circle.fill")
                .font(.system(size: 9))
            Text(message)
                .font(.system(size: 9))
        }
        .foregroundStyle(Color(hex: 0xF87171))
    }
}

private struct PostSecondaryButtonStyle: ButtonStyle {
    func makeBody(configuration: Configuration) -> some View {
        AppSecondaryButtonStyle().makeBody(configuration: configuration)
    }
}

#Preview {
    PostGeneratorView(viewModel: PostGeneratorViewModel())
        .frame(width: 880, height: 720)
}