import UIKit
import SwiftUI
import UniformTypeIdentifiers

// MARK: - Quick Update share extension
//
// Appears in the share sheet when the user shares/selects text in ANY app (their
// bank, broker…) or shares a screenshot where the balance is visible. Shows a
// compact form floating over the host app: pick a source (the next one pending
// this month is preselected), amount prefilled from the shared text — or OCR'd
// on-device from the image — save, and the user never leaves the bank app. The
// main app turns these captures into real snapshots on its next activation.

@objc(ShareViewController)
final class ShareViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .clear
        extractSharedContent { [weak self] text, image in
            DispatchQueue.main.async {
                self?.presentForm(sharedText: text, sharedImage: image)
            }
        }
    }

    private func extractSharedContent(completion: @escaping (String?, UIImage?) -> Void) {
        let providers = (extensionContext?.inputItems as? [NSExtensionItem])?
            .compactMap { $0.attachments }
            .flatMap { $0 } ?? []

        if let provider = providers.first(where: {
            $0.hasItemConformingToTypeIdentifier(UTType.plainText.identifier)
        }) {
            provider.loadItem(forTypeIdentifier: UTType.plainText.identifier, options: nil) { item, _ in
                completion(item as? String, nil)
            }
            return
        }

        if let provider = providers.first(where: {
            $0.hasItemConformingToTypeIdentifier(UTType.image.identifier)
        }) {
            provider.loadItem(forTypeIdentifier: UTType.image.identifier, options: nil) { item, _ in
                completion(nil, Self.image(from: item))
            }
            return
        }

        completion(nil, nil)
    }

    /// Share sheets deliver images as UIImage, file URL, or raw Data depending on the host app.
    private static func image(from item: NSSecureCoding?) -> UIImage? {
        switch item {
        case let image as UIImage: return image
        case let url as URL: return (try? Data(contentsOf: url)).flatMap(UIImage.init(data:))
        case let data as Data: return UIImage(data: data)
        default: return nil
        }
    }

    private func presentForm(sharedText: String?, sharedImage: UIImage?) {
        let form = QuickUpdateShareView(
            sharedText: sharedText,
            sharedImage: sharedImage,
            onDone: { [weak self] in
                self?.extensionContext?.completeRequest(returningItems: nil)
            },
            onCancel: { [weak self] in
                self?.extensionContext?.cancelRequest(withError: NSError(
                    domain: "com.alexandrevazquez.PortfolioJournal.QuickUpdate",
                    code: NSUserCancelledError
                ))
            }
        )
        let host = UIHostingController(rootView: form)
        host.modalPresentationStyle = .formSheet
        if let sheet = host.sheetPresentationController {
            sheet.detents = [.medium(), .large()]
            sheet.prefersGrabberVisible = true
        }
        host.isModalInPresentation = true
        present(host, animated: true)
    }
}

// MARK: - Form

struct QuickUpdateShareView: View {
    let sharedText: String?
    let sharedImage: UIImage?
    let onDone: () -> Void
    let onCancel: () -> Void

    @State private var sources: [ExtSourceInfo] = []
    @State private var selectedSourceId: UUID?
    @State private var amountText: String = ""
    @State private var saved = false
    @State private var scanning = false
    @State private var candidates: [ExtAmountCandidate] = []
    @State private var scanFoundNothing = false
    @FocusState private var amountFocused: Bool

    private var parsedAmount: Decimal? {
        ExtAmountParser.parse(amountText)
    }

    var body: some View {
        NavigationStack {
            Group {
                if sources.isEmpty {
                    ContentUnavailableView(
                        String(localized: "ext_no_sources_title"),
                        systemImage: "list.bullet",
                        description: Text(String(localized: "ext_no_sources_body"))
                    )
                } else if saved {
                    savedConfirmation
                } else {
                    form
                }
            }
            .navigationTitle(String(localized: "ext_title"))
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button(String(localized: "ext_cancel")) { onCancel() }
                }
                if !sources.isEmpty && !saved {
                    ToolbarItem(placement: .confirmationAction) {
                        Button(String(localized: "ext_save")) { save() }
                            .disabled(parsedAmount == nil || selectedSourceId == nil)
                            .fontWeight(.semibold)
                    }
                }
            }
        }
        .onAppear(perform: load)
    }

    private var form: some View {
        Form {
            Section(String(localized: "ext_amount_section")) {
                if scanning {
                    HStack(spacing: 10) {
                        ProgressView()
                        Text(String(localized: "ext_scanning_image"))
                            .font(.subheadline)
                            .foregroundColor(.secondary)
                    }
                } else {
                    TextField(String(localized: "ext_amount_placeholder"), text: $amountText)
                        .keyboardType(.decimalPad)
                        .font(.title3.weight(.semibold))
                        .focused($amountFocused)
                    if scanFoundNothing {
                        Text(String(localized: "ext_ocr_no_amounts"))
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }
                }
            }

            if candidates.count > 1 {
                Section(String(localized: "ext_detected_amounts")) {
                    ScrollView(.horizontal, showsIndicators: false) {
                        HStack(spacing: 8) {
                            ForEach(candidates) { candidate in
                                Button {
                                    amountText = "\(candidate.value)"
                                } label: {
                                    Text(candidate.display)
                                        .font(.subheadline.weight(.medium))
                                        .padding(.horizontal, 12)
                                        .padding(.vertical, 7)
                                        .background(
                                            Capsule().fill(
                                                amountText == "\(candidate.value)"
                                                    ? Color.blue.opacity(0.18)
                                                    : Color(.tertiarySystemFill)
                                            )
                                        )
                                        .overlay(
                                            Capsule().strokeBorder(
                                                amountText == "\(candidate.value)" ? Color.blue : .clear,
                                                lineWidth: 1
                                            )
                                        )
                                        .foregroundColor(.primary)
                                }
                                .buttonStyle(.plain)
                            }
                        }
                        .padding(.vertical, 2)
                    }
                }
            }

            Section(String(localized: "ext_source_section")) {
                ForEach(sources) { source in
                    Button {
                        selectedSourceId = source.id
                    } label: {
                        HStack {
                            VStack(alignment: .leading, spacing: 2) {
                                Text(source.name)
                                    .foregroundColor(.primary)
                                    .font(.subheadline.weight(.medium))
                                if source.updatedThisMonth {
                                    Text(String(localized: "ext_already_updated"))
                                        .font(.caption2)
                                        .foregroundColor(.secondary)
                                }
                            }
                            Spacer()
                            if selectedSourceId == source.id {
                                Image(systemName: "checkmark.circle.fill")
                                    .foregroundColor(.blue)
                            }
                        }
                    }
                }
            }
        }
    }

    private var savedConfirmation: some View {
        VStack(spacing: 14) {
            Image(systemName: "checkmark.circle.fill")
                .font(.system(size: 52))
                .foregroundColor(.green)
            Text(String(localized: "ext_saved_title"))
                .font(.headline)
            Text(String(localized: "ext_saved_body"))
                .font(.subheadline)
                .foregroundColor(.secondary)
                .multilineTextAlignment(.center)
        }
        .padding(32)
        .onAppear {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1.2) { onDone() }
        }
    }

    private func load() {
        var mirror = ExtSharedStore.readMirror()
        // Pending-first ordering: the sources still waiting this month come on top.
        mirror.sort { a, b in
            if a.updatedThisMonth != b.updatedThisMonth { return !a.updatedThisMonth }
            return a.name.localizedCaseInsensitiveCompare(b.name) == .orderedAscending
        }
        sources = mirror
        selectedSourceId = mirror.first(where: { !$0.updatedThisMonth })?.id ?? mirror.first?.id

        if let sharedText, let parsed = ExtAmountParser.parse(sharedText) {
            amountText = "\(parsed)"
        } else if let sharedImage {
            scanImage(sharedImage)
        } else {
            amountFocused = true
        }
    }

    private func scanImage(_ image: UIImage) {
        scanning = true
        ExtImageAmountScanner.scan(image) { found in
            DispatchQueue.main.async {
                scanning = false
                candidates = found
                if let best = found.first {
                    // Most visually prominent number — in bank UIs, the balance.
                    amountText = "\(best.value)"
                } else {
                    scanFoundNothing = true
                    amountFocused = true
                }
            }
        }
    }

    private func save() {
        guard let amount = parsedAmount, let sourceId = selectedSourceId else { return }
        ExtSharedStore.appendPending(ExtPendingUpdate(
            sourceId: sourceId,
            amount: NSDecimalNumber(decimal: amount).doubleValue,
            capturedAt: Date()
        ))
        withAnimation { saved = true }
    }
}