import Foundation
import SwiftUI
import WebKit

struct KakaoPostcodeResult {
    let zonecode: String
    let address: String

    init?(payload: Any) {
        guard let values = payload as? [String: Any],
              let zonecode = values["zonecode"] as? String,
              let address = values["address"] as? String,
              !zonecode.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty,
              !address.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else { return nil }
        self.zonecode = zonecode
        self.address = address
    }
}

struct KakaoPostcodeSearchView: View {
    let onSelect: (KakaoPostcodeResult) -> Void
    @Environment(\.dismiss) private var dismiss
    @State private var isLoading = true
    @State private var hasFailed = false

    var body: some View {
        VStack(spacing: 0) {
            HStack {
                Text("우편번호 검색").appFont(.body2)
                Spacer()
                Button("닫기") { dismiss() }
                    .appFont(.body3)
                    .frame(minHeight: 44)
                    .accessibilityLabel("우편번호 검색 닫기")
            }
            .foregroundColor(.white)
            .padding(.horizontal, SodaSpacing.s14)
            ZStack {
                KakaoPostcodeWebView(onSelect: onSelect) { failed in
                    hasFailed = failed
                    isLoading = false
                }
                .opacity(hasFailed ? 0 : 1)
                .allowsHitTesting(!hasFailed)
                .accessibilityHidden(hasFailed)
                if hasFailed {
                    Text("주소 검색을 불러오지 못했습니다. 닫은 후 다시 시도해 주세요.")
                        .appFont(.body3)
                        .foregroundColor(.white)
                        .padding(SodaSpacing.s14)
                } else if isLoading {
                    ProgressView("주소 검색을 불러오는 중")
                        .tint(.white)
                        .foregroundColor(.white)
                        .padding(SodaSpacing.s14)
                        .background(Color.gray900)
                        .cornerRadius(SodaRadius.r14)
                }
            }
        }
        .background(Color.black)
    }
}

private struct KakaoPostcodeWebView: UIViewRepresentable {
    let onSelect: (KakaoPostcodeResult) -> Void
    let onLoad: (Bool) -> Void
    private static let handlerName = "postcodeSelection"

    func makeCoordinator() -> Coordinator {
        Coordinator(onSelect: onSelect, onLoad: onLoad)
    }

    func makeUIView(context: Context) -> WKWebView {
        let configuration = WKWebViewConfiguration()
        configuration.userContentController.add(context.coordinator, name: Self.handlerName)
        let webView = WKWebView(frame: .zero, configuration: configuration)
        webView.navigationDelegate = context.coordinator
        webView.loadHTMLString(Self.html, baseURL: URL(string: "https://postcode.map.kakao.com/"))
        return webView
    }

    func updateUIView(_ uiView: WKWebView, context: Context) {}

    static func dismantleUIView(_ uiView: WKWebView, coordinator: Coordinator) {
        coordinator.isActive = false
        uiView.stopLoading()
        uiView.configuration.userContentController.removeScriptMessageHandler(forName: handlerName)
        uiView.navigationDelegate = nil
        uiView.uiDelegate = nil
    }

    private static let html = """
    <!doctype html>
    <html><head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>html,body,#postcode{margin:0;width:100%;height:100%;}</style>
    <script src="https://t1.kakaocdn.net/mapjsapi/bundle/postcode/prod/postcode.v2.js"
      onerror="document.documentElement.dataset.postcodeError='true'"></script>
    </head><body><div id="postcode"></div>
    <script>
    try {
      new kakao.Postcode({
        width: '100%', height: '100%',
        oncomplete: function(data) {
          window.webkit.messageHandlers.postcodeSelection.postMessage({ zonecode: data.zonecode, address: data.address });
        }
      }).embed(document.getElementById('postcode'));
    } catch (error) {
      document.documentElement.dataset.postcodeError = 'true';
    }
    </script></body></html>
    """

    final class Coordinator: NSObject, WKScriptMessageHandler, WKNavigationDelegate {
        private let onSelect: (KakaoPostcodeResult) -> Void
        private let onLoad: (Bool) -> Void
        fileprivate var isActive = true
        private var hasFailed = false
        private var hasSelected = false

        init(onSelect: @escaping (KakaoPostcodeResult) -> Void, onLoad: @escaping (Bool) -> Void) {
            self.onSelect = onSelect
            self.onLoad = onLoad
        }

        func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
            guard isActive, !hasFailed, !hasSelected,
                  message.name == KakaoPostcodeWebView.handlerName,
                  message.frameInfo.isMainFrame,
                  let result = KakaoPostcodeResult(payload: message.body) else { return }
            hasSelected = true
            onSelect(result)
        }

        func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
            webView.evaluateJavaScript("document.documentElement.dataset.postcodeError === 'true'") { [weak self] value, error in
                guard let self, self.isActive, !self.hasFailed else { return }
                if error != nil || value as? Bool != false {
                    self.fail()
                } else {
                    self.onLoad(false)
                }
            }
        }

        func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
            fail()
        }

        func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
            fail()
        }

        func webViewWebContentProcessDidTerminate(_ webView: WKWebView) {
            fail()
        }

        private func fail() {
            guard isActive else { return }
            hasFailed = true
            onLoad(true)
        }
    }
}