import SwiftUI

struct TitleOptimizerView: View {
    @Bindable var viewModel: TitleOptimizerViewModel

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

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

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

                        PostPageBoundary {
                            switch viewModel.selectedTab {
                            case .optimize:
                                optimizeContent
                            case .compare:
                                compareContent
                            case .preview:
                                previewContent
                            }
                        }
                    }
                    .padding(.horizontal, Layout.horizontalPadding)
                    .padding(.top, 12)
                    .padding(.bottom, 24)
                }
                .onChange(of: viewModel.variants.count) { _, count in
                    guard count > 0, viewModel.selectedTab == .optimize else { return }
                    withAnimation(.easeInOut(duration: 0.25)) {
                        scrollProxy.scrollTo("title-suggestions", anchor: .top)
                    }
                }
            }
        }
        .background(AppTheme.background)
    }

    // MARK: - Header

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

                VStack(alignment: .leading, spacing: 2) {
                    Text("Title Optimizer")
                        .font(.system(size: 18, weight: .semibold))
                        .foregroundStyle(AppTheme.textPrimary)
                    Text(viewModel.generationEngineSubtitle)
                        .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.activeTitle.trimmingCharacters(in: .whitespaces).isEmpty)

            Button {
                Task { await viewModel.optimizeTitles() }
            } label: {
                HStack(spacing: 6) {
                    if viewModel.isOptimizing {
                        ProgressView()
                            .controlSize(.small)
                            .tint(.white)
                    } else {
                        Image(systemName: "sparkles")
                            .font(.system(size: 11, weight: .semibold))
                    }
                    Text(viewModel.isOptimizing ? "Optimizing…" : "Optimize")
                        .font(.system(size: 11, weight: .semibold))
                }
                .foregroundStyle(.white)
                .padding(.horizontal, 14)
                .padding(.vertical, 8)
                .background(viewModel.canOptimize ? AppTheme.accentBlue : AppTheme.accentBlue.opacity(0.4))
                .clipShape(RoundedRectangle(cornerRadius: 8))
            }
            .buttonStyle(AppPrimaryButtonStyle())
            .disabled(!viewModel.canOptimize)
        }
    }

    // MARK: - Tab Bar

    private var tabBar: some View {
        ToolSegmentedTabBar(
            selection: $viewModel.selectedTab,
            accentColor: AppTheme.accentBlue,
            width: 300
        )
    }

    // MARK: - Optimize

    private var optimizeContent: some View {
        optimizeColumns
    }

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

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

            optimizeColumn(title: "Title & Suggestions", icon: "textformat") {
                editorPanel
            }
            .frame(minWidth: 0, maxWidth: .infinity)
            .layoutPriority(0)
        }
    }

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

    private func sectionHeader(title: String, icon: String) -> some View {
        HStack(spacing: 6) {
            Image(systemName: icon)
                .font(.system(size: 10, weight: .semibold))
                .foregroundStyle(AppTheme.accentBlue)
            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: "Target Subreddit", subtitle: "Tailor titles for the community") {
                PostFormField(
                    label: "Subreddit",
                    placeholder: "technology",
                    text: $viewModel.draft.subreddit,
                    prefix: "r/",
                    isRequired: true
                )
            }

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

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

            PostFormCard(title: "Title Goal", subtitle: "What kind of hook do you want?") {
                TitleGoalPicker(selectedGoal: $viewModel.draft.titleGoal)
            }

            PostFormCard(title: "Preview Context", subtitle: "Optional — affects preview style") {
                VStack(alignment: .leading, spacing: 12) {
                    PostTypePicker(selectedType: Binding(
                        get: { viewModel.draft.postType },
                        set: { viewModel.selectPostType($0) }
                    ))

                    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
                    )
                }
            }

            PostFormCard(title: "Suggestions", subtitle: "How many variants to generate") {
                TitleVariantCountPicker(selectedCount: $viewModel.draft.variantCount)
            }
        }
    }

    private var editorPanel: some View {
        VStack(spacing: Layout.sectionSpacing) {
            PostFormCard(title: "Original Title", subtitle: "The title you want to improve") {
                PostFormField(
                    label: "Post Title",
                    placeholder: "Enter your draft title here",
                    text: $viewModel.draft.originalTitle,
                    isRequired: true
                )
            }

            characterCountFooter

            if let analysis = viewModel.analysis {
                TitleAnalysisCard(analysis: analysis)
            }

            suggestionsSection
                .id("title-suggestions")
        }
    }

    @ViewBuilder
    private var suggestionsSection: some View {
        PostFormCard(
            title: "AI Suggestions",
            subtitle: viewModel.variants.isEmpty
                ? "Hit Optimize to generate title variants"
                : "\(viewModel.variants.count) optimized titles ranked by score"
        ) {
            if viewModel.variants.isEmpty {
                TitleOptimizerEmptyState(
                    icon: "textformat.size",
                    title: "No suggestions yet",
                    subtitle: "Fill in your subreddit, topic, and title,\nthen tap Optimize to get AI-powered variants."
                )
            } else {
                VStack(spacing: 8) {
                    ForEach(viewModel.variants) { variant in
                        TitleVariantRow(
                            variant: variant,
                            isSelected: viewModel.selectedVariantID == variant.id,
                            onApply: { viewModel.applyVariant(variant) }
                        )
                    }
                }
            }
        }
    }

    private var characterCountFooter: some View {
        HStack(spacing: 12) {
            Text("\(viewModel.draft.originalTitle.count) / 300")
                .font(.system(size: 10, weight: .medium, design: .monospaced))
                .foregroundStyle(
                    viewModel.draft.originalTitle.count > 300 ? Color(hex: 0xF87171) : AppTheme.textTertiary
                )

            Spacer()

            Text("Reddit limit: 300 characters for title")
                .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)
                )
        )
    }

    // MARK: - Compare

    private var compareContent: some View {
        VStack(alignment: .leading, spacing: Layout.columnSpacing) {
            compareHeader

            if viewModel.variants.isEmpty {
                TitleOptimizerEmptyState(
                    icon: "arrow.left.arrow.right",
                    title: "Nothing to compare yet",
                    subtitle: "Generate title suggestions on the Optimize tab first."
                )
                .frame(maxWidth: .infinity)
            } else {
                compareBody
            }
        }
    }

    private var compareBody: some View {
        VStack(spacing: Layout.sectionSpacing) {
            TitleCompareCard(
                title: viewModel.draft.originalTitle,
                score: viewModel.analysis?.overallScore,
                label: "Original",
                isOriginal: true,
                isSelected: viewModel.selectedVariantID == nil
            )

            HStack {
                Rectangle()
                    .fill(AppTheme.border)
                    .frame(height: 1)
                Text("vs")
                    .font(.system(size: 10, weight: .semibold))
                    .foregroundStyle(AppTheme.textTertiary)
                    .padding(.horizontal, 8)
                Rectangle()
                    .fill(AppTheme.border)
                    .frame(height: 1)
            }

            VStack(spacing: 8) {
                ForEach(viewModel.variants) { variant in
                    TitleCompareCard(
                        title: variant.title,
                        score: variant.score,
                        label: "Variant #\(variantRank(variant))",
                        isOriginal: false,
                        isSelected: viewModel.selectedVariantID == variant.id
                    )
                    .onTapGesture {
                        viewModel.applyVariant(variant)
                    }
                }
            }

            compareMetadata
        }
        .frame(maxWidth: 640)
        .frame(maxWidth: .infinity)
    }

    private var compareHeader: some View {
        HStack(alignment: .top) {
            sectionHeader(title: "Side-by-Side Comparison", icon: "arrow.left.arrow.right")

            Spacer()

            if let best = viewModel.bestVariant {
                HStack(spacing: 6) {
                    Image(systemName: "trophy.fill")
                        .font(.system(size: 10))
                        .foregroundStyle(AppTheme.accentYellow)
                    Text("Best: \(best.score)/100")
                        .font(.system(size: 10, weight: .semibold))
                        .foregroundStyle(AppTheme.textSecondary)
                }
                .padding(.top, 1)
            }
        }
    }

    private var compareMetadata: some View {
        VStack(alignment: .leading, spacing: 0) {
            metadataRow(label: "Subreddit", value: viewModel.formattedSubreddit)
            metadataDivider
            metadataRow(label: "Goal", value: viewModel.draft.titleGoal.title)
            metadataDivider
            metadataRow(label: "Tone", value: viewModel.draft.tone.title)
            metadataDivider
            metadataRow(label: "Engine", value: viewModel.usesLiveAI ? "AI" : "Local templates")
            metadataDivider
            metadataRow(label: "Active", value: viewModel.activeTitle)
        }
        .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 func variantRank(_ variant: TitleVariant) -> Int {
        (viewModel.variants.firstIndex(where: { $0.id == variant.id }) ?? 0) + 1
    }

    // MARK: - Preview

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

            HStack {
                Spacer(minLength: 0)

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

                    PostFormCard(title: "Feed Preview", subtitle: "How your title looks in a crowded feed") {
                        VStack(spacing: 6) {
                            TitleFeedPreviewRow(
                                title: "Other trending post in this subreddit right now",
                                subreddit: viewModel.formattedSubreddit
                            )
                            TitleFeedPreviewRow(
                                title: viewModel.activeTitle,
                                subreddit: viewModel.formattedSubreddit,
                                isHighlighted: true
                            )
                            TitleFeedPreviewRow(
                                title: "Another popular discussion happening nearby",
                                subreddit: viewModel.formattedSubreddit
                            )
                        }
                    }

                    previewMetadata
                }
                .frame(maxWidth: 560)

                Spacer(minLength: 0)
            }
        }
    }

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

            if let score = viewModel.analysis?.overallScore {
                metadataDivider
                metadataRow(label: "Score", value: "\(score)/100")
            }

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

#Preview {
    TitleOptimizerView(viewModel: TitleOptimizerViewModel())
        .frame(width: 880, height: 720)
}