//
//  RenderingBlockView.swift
//  GeminiRenderer
//
//  Created by Shadowfacts on 7/13/20.
//

import SwiftUI
import GeminiFormat

struct RenderingBlockView: View {
    let block: RenderingBlock
    let changeURL: ((URL) -> Void)?
    @State var hovering = false
    
    init(block: RenderingBlock, changeURL: ((URL) -> Void)? = nil) {
        self.block = block
        self.changeURL = changeURL
    }
    
    @ViewBuilder
    var body: some View {
        switch block {
        case let .text(text):
            self.text(text)
        case let .link(url, text: linkText):
            self.link(url, text: linkText)
        case let .preformatted(text, alt: _):
            preformatted(text)
        case let .heading(text, level: level):
            heading(text, level: level)
        case let .unorderedListItem(text):
            unorderedListItem(text)
        case let .quote(text):
            quote(text)
        }
    }
    
    private func text(_ text: String) -> some View {
        Text(text)
            .font(.documentBody)
            .frame(maxWidth: .infinity, alignment: .leading)
    }
    
    private func link(_ url: URL, text: String?) -> some View {
        let text = text ?? url.absoluteString
        
        #if os(macOS)
            let buttonStyle = LinkButtonStyle()
        #elseif os(iOS)
            let buttonStyle = PlainButtonStyle()
        #endif
        
        let button: some View = Button {
            self.changeURL?(url)
        } label: {
            Text(verbatim: text)
                .font(.documentBody)
                .foregroundColor(hovering ? .blue : Color.blue.opacity(0.8))
                .underline()
                .frame(maxWidth: .infinity, alignment: .leading)
        }
            .buttonStyle(buttonStyle)
            .onHover { hovering in
                self.hovering = hovering
            }
        
        if #available(macOS 10.16, iOS 14.0, *) {
            return AnyView(button.help(url.absoluteString))
        } else {
            return AnyView(button)
        }
    }
    
    private func preformatted(_ text: String) -> some View {
        ScrollView(.horizontal) {
            Text(verbatim: text)
                .font(.documentBodyPreformatted)
                .frame(maxWidth: .infinity, alignment: .leading)
        }
    }
    
    private func heading(_ text: String, level: Document.HeadingLevel) -> some View {
        Text(verbatim: text)
            .font(level.font)
            .frame(maxWidth: .infinity, alignment: .leading)
    }
    
    private func unorderedListItem(_ text: String) -> some View {
        // todo: should this be .firstTextBaseline?
        HStack(alignment: .top, spacing: 4) {
            Text(verbatim: "\u{2022}")
            Text(verbatim: text)
                .font(.documentBody)
            Spacer()
        }.frame(maxWidth: .infinity, alignment: .leading)
    }
    
    private func quote(_ text: String) -> some View {
        HStack(spacing: 4) {
            Color.gray
                .frame(width: 4)
            Text(verbatim: text)
                .font(Font.documentBody.italic())
                .foregroundColor(.gray)
            Spacer()
        }.frame(maxWidth: .infinity, alignment: .leading)
    }
}

struct RenderingBlockView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            RenderingBlockView(block: .text("Some Text"))
            RenderingBlockView(block: .quote("A Quote"))
        }
    }
}