//
//  CVFilledPreviewPageView.swift
//  App for Indeed
//
//  Full-screen preview of a profile merged into the selected CV template.
//

import Cocoa
import UniformTypeIdentifiers

private final class CVPreviewFlippedDocumentView: NSView {
    override var isFlipped: Bool { true }
}

/// Same metrics as job cards’ **Apply** (`DashboardView` `JobPayloadButton`): 13pt semibold, 32pt tall, 8pt corners.
private final class CVPreviewPrimaryCTAButton: NSButton {
    private static let fill = NSColor(srgbRed: 37 / 255, green: 87 / 255, blue: 167 / 255, alpha: 1)
    private static let fillHover = NSColor(srgbRed: 28 / 255, green: 70 / 255, blue: 140 / 255, alpha: 1)
    /// Slightly wider than default title metrics so the label is not flush to the pill edges.
    private static let horizontalOutset: CGFloat = 20

    private var trackingAreaRef: NSTrackingArea?
    private var didPushCursor = false

    init(title: String, target: Any?, action: Selector?) {
        super.init(frame: .zero)
        self.title = title
        self.target = target as AnyObject?
        self.action = action
        translatesAutoresizingMaskIntoConstraints = false
        isBordered = false
        bezelStyle = .rounded
        font = .systemFont(ofSize: 13, weight: .semibold)
        wantsLayer = true
        layer?.cornerRadius = 8
        layer?.backgroundColor = Self.fill.cgColor
        contentTintColor = NSColor(srgbRed: 1, green: 1, blue: 1, alpha: 1)
        focusRingType = .none
        setContentHuggingPriority(.required, for: .horizontal)
        setContentCompressionResistancePriority(.required, for: .horizontal)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var intrinsicContentSize: NSSize {
        let s = super.intrinsicContentSize
        guard s.width != NSView.noIntrinsicMetric, s.width >= 1 else { return s }
        return NSSize(width: s.width + Self.horizontalOutset, height: s.height)
    }

    override func updateTrackingAreas() {
        super.updateTrackingAreas()
        if let ta = trackingAreaRef { removeTrackingArea(ta) }
        let ta = NSTrackingArea(
            rect: bounds,
            options: [.activeInKeyWindow, .mouseEnteredAndExited, .inVisibleRect],
            owner: self,
            userInfo: nil
        )
        addTrackingArea(ta)
        trackingAreaRef = ta
    }

    override func mouseEntered(with event: NSEvent) {
        super.mouseEntered(with: event)
        layer?.backgroundColor = Self.fillHover.cgColor
        if !didPushCursor {
            NSCursor.pointingHand.push()
            didPushCursor = true
        }
    }

    override func mouseExited(with event: NSEvent) {
        super.mouseExited(with: event)
        layer?.backgroundColor = Self.fill.cgColor
        if didPushCursor {
            NSCursor.pop()
            didPushCursor = false
        }
    }

    override func viewWillMove(toWindow newWindow: NSWindow?) {
        super.viewWillMove(toWindow: newWindow)
        if newWindow == nil, didPushCursor {
            NSCursor.pop()
            didPushCursor = false
        }
    }
}

/// Hosts a scrollable `CVProfileDocumentView` with a simple chrome header and back navigation.
final class CVFilledPreviewPageView: NSView {

    var onDismiss: (() -> Void)?

    private let backButton = NSButton(title: "← Profiles", target: nil, action: nil)
    private let titleLabel = NSTextField(labelWithString: "CV preview")
    private let exportButton = CVPreviewPrimaryCTAButton(title: "Export PDF…", target: nil, action: nil)
    private let scrollView = NSScrollView()
    private let documentView = CVPreviewFlippedDocumentView()
    private let contentStack = NSStackView()

    private weak var profileDocumentView: CVProfileDocumentView?
    private var lastProfile: SavedProfile?
    private var lastTemplate: CVTemplate?

    private static let pageBackground = NSColor(srgbRed: 1, green: 1, blue: 1, alpha: 1)
    private static let secondaryText = NSColor(srgbRed: 100 / 255, green: 116 / 255, blue: 139 / 255, alpha: 1)
    private static let brandBlue = NSColor(srgbRed: 37 / 255, green: 87 / 255, blue: 167 / 255, alpha: 1)

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        wantsLayer = true
        layer?.backgroundColor = Self.pageBackground.cgColor
        userInterfaceLayoutDirection = .leftToRight

        backButton.translatesAutoresizingMaskIntoConstraints = false
        backButton.bezelStyle = .rounded
        backButton.isBordered = false
        backButton.font = .systemFont(ofSize: 13, weight: .semibold)
        backButton.contentTintColor = Self.brandBlue
        backButton.target = self
        backButton.action = #selector(didTapBack)

        titleLabel.font = .systemFont(ofSize: 18, weight: .semibold)
        titleLabel.textColor = NSColor(srgbRed: 31 / 255, green: 41 / 255, blue: 55 / 255, alpha: 1)

        exportButton.target = self
        exportButton.action = #selector(didTapExportPDF)

        let subtitle = NSTextField(wrappingLabelWithString: "Layout matches the CV Maker thumbnail for this template. Export a PDF that matches what you see here (fonts, columns, colours, and rules).")
        subtitle.font = .systemFont(ofSize: 12, weight: .regular)
        subtitle.textColor = Self.secondaryText
        subtitle.maximumNumberOfLines = 0

        let headerCol = NSStackView(views: [backButton, titleLabel, subtitle, exportButton])
        headerCol.orientation = .vertical
        headerCol.alignment = .leading
        headerCol.spacing = 6
        headerCol.setCustomSpacing(14, after: backButton)
        headerCol.setCustomSpacing(10, after: subtitle)
        headerCol.translatesAutoresizingMaskIntoConstraints = false

        contentStack.orientation = .vertical
        contentStack.alignment = .leading
        contentStack.spacing = 20
        contentStack.translatesAutoresizingMaskIntoConstraints = false

        documentView.translatesAutoresizingMaskIntoConstraints = false
        documentView.addSubview(contentStack)

        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.drawsBackground = false
        scrollView.hasVerticalScroller = true
        scrollView.hasHorizontalScroller = false
        scrollView.autohidesScrollers = true
        scrollView.borderType = .noBorder
        scrollView.documentView = documentView

        addSubview(headerCol)
        addSubview(scrollView)

        NSLayoutConstraint.activate([
            headerCol.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 32),
            headerCol.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -32),
            headerCol.topAnchor.constraint(equalTo: topAnchor, constant: 16),

            exportButton.heightAnchor.constraint(equalToConstant: 32),
            exportButton.widthAnchor.constraint(greaterThanOrEqualToConstant: 96),

            scrollView.leadingAnchor.constraint(equalTo: leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: trailingAnchor),
            scrollView.topAnchor.constraint(equalTo: headerCol.bottomAnchor, constant: 16),
            scrollView.bottomAnchor.constraint(equalTo: bottomAnchor),

            documentView.leadingAnchor.constraint(equalTo: scrollView.contentView.leadingAnchor),
            documentView.widthAnchor.constraint(equalTo: scrollView.contentView.widthAnchor),
            documentView.topAnchor.constraint(equalTo: scrollView.contentView.topAnchor),
            documentView.bottomAnchor.constraint(equalTo: contentStack.bottomAnchor, constant: 40),

            contentStack.leadingAnchor.constraint(equalTo: documentView.leadingAnchor, constant: 32),
            contentStack.trailingAnchor.constraint(lessThanOrEqualTo: documentView.trailingAnchor, constant: -32),
            contentStack.topAnchor.constraint(equalTo: documentView.topAnchor, constant: 8),
            contentStack.widthAnchor.constraint(lessThanOrEqualTo: documentView.widthAnchor, constant: -64)
        ])
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func configure(profile: SavedProfile, template: CVTemplate) {
        lastProfile = profile
        lastTemplate = template
        for v in contentStack.arrangedSubviews {
            contentStack.removeArrangedSubview(v)
            v.removeFromSuperview()
        }
        let doc = CVProfileDocumentView(profile: profile, template: template)
        profileDocumentView = doc
        contentStack.addArrangedSubview(doc)
        let profileTitle = profile.profileDisplayName.isEmpty ? "Untitled profile" : profile.profileDisplayName
        titleLabel.stringValue = "\(template.name) · \(profileTitle)"
    }

    @objc private func didTapBack() {
        onDismiss?()
    }

    @objc private func didTapExportPDF() {
        // NSSavePanel and sandboxed file writes must run on the main thread (and after a button
        // callback can be mis-attributed under Swift’s default actor isolation).
        DispatchQueue.main.async { [weak self] in
            self?.runExportPDFOnMainThread()
        }
    }

    private func runExportPDFOnMainThread() {
        guard let doc = profileDocumentView else { return }
        doc.layoutSubtreeIfNeeded()
        let bounds = doc.bounds
        guard !bounds.isEmpty else { return }
        // `dataWithPDF` uses the print pipeline and often drops layer-backed chrome (card fill,
        // borders, hairlines, tinted sidebars) while keeping text — so the PDF looks like plain
        // text. Rasterising what is actually drawn on screen preserves the full layout.
        let data = doc.pdfDataMatchingScreenAppearance() ?? doc.dataWithPDF(inside: bounds)
        guard !data.isEmpty else {
            presentExportError("The résumé could not be rendered to PDF (empty output). Try scrolling the preview so it lays out, then export again.")
            return
        }

        let panel = NSSavePanel()
        panel.canCreateDirectories = true
        panel.allowedContentTypes = [.pdf]
        let base = lastTemplate?.name ?? "CV"
        let safe = base.replacingOccurrences(of: "/", with: "-")
        panel.nameFieldStringValue = "\(safe).pdf"

        guard let hostWindow = window else {
            if panel.runModal() == .OK, let url = panel.url {
                writePDFData(data, to: url)
            }
            return
        }
        panel.beginSheetModal(for: hostWindow) { [weak self] response in
            guard let self, response == .OK, let url = panel.url else { return }
            self.writePDFData(data, to: url)
        }
    }

    private func writePDFData(_ data: Data, to url: URL) {
        let accessing = url.startAccessingSecurityScopedResource()
        defer {
            if accessing { url.stopAccessingSecurityScopedResource() }
        }
        do {
            try data.write(to: url, options: .atomic)
        } catch {
            presentExportError(error.localizedDescription)
        }
    }

    private func presentExportError(_ message: String) {
        let alert = NSAlert()
        alert.messageText = "Couldn’t save PDF"
        alert.informativeText = message
        alert.alertStyle = .warning
        alert.addButton(withTitle: "OK")
        if let window {
            alert.beginSheetModal(for: window, completionHandler: nil)
        } else {
            alert.runModal()
        }
    }
}

// MARK: - PDF export (screen-accurate)

private extension NSView {

    /// Single-page PDF that matches the composited on-screen appearance, including
    /// `CALayer` backgrounds, borders, and rules. Callers fall back to `dataWithPDF` when this returns nil.
    func pdfDataMatchingScreenAppearance() -> Data? {
        layoutSubtreeIfNeeded()
        let rect = bounds
        guard rect.width > 1, rect.height > 1 else { return nil }

        guard let rep = bitmapImageRepForCachingDisplay(in: rect) else { return nil }
        cacheDisplay(in: rect, to: rep)
        guard let cgImage = rep.cgImage else { return nil }

        let data = NSMutableData()
        guard let consumer = CGDataConsumer(data: data as CFMutableData) else { return nil }
        var mediaBox = CGRect(origin: .zero, size: NSSize(width: rect.width, height: rect.height))
        guard let ctx = CGContext(consumer: consumer, mediaBox: &mediaBox, nil) else { return nil }

        ctx.beginPDFPage(nil)
        ctx.interpolationQuality = .high
        // Draw without an extra Y-flip: `cacheDisplay`’s bitmap + `cgImage` already match PDF user space
        // on macOS here; a translate/scale(-1) was inverting the whole page in Preview.
        ctx.draw(cgImage, in: mediaBox)
        ctx.endPDFPage()
        ctx.closePDF()

        let out = data as Data
        return out.isEmpty ? nil : out
    }
}