//
//  GeminiHTMLRenderer.swift
//  GeminiRenderer
//
//  Created by Shadowfacts on 12/16/20.
//

import Foundation
import GeminiFormat
import HTMLEntities

public class GeminiHTMLRenderer {
    
    public var linkPrefix: ((URL) -> String?)?
    
    public init() {
    }
    
    public func renderDocumentToHTML(_ doc: Document) -> String {
        var str = ""
        
        var inPreformatting = false
        var inList = false
        
        for (index, line) in doc.lines.enumerated() {
            if inList && !line.isListItem {
                str += "</ul>"
            }
            
            switch line {
            case let .text(text):
                str += "<p>\(text.htmlEscape())</p>"
            case let .link(url, text: maybeText):
                let text = maybeText ?? url.absoluteString
                let linkPrefix = self.linkPrefix?(url) ?? ""
                str += "<p class=\"link\">\(linkPrefix)<a href=\"\(url.absoluteString)\">\(text.htmlEscape())</a></p>"
            case .preformattedToggle(alt: _):
                inPreformatting = !inPreformatting
                if inPreformatting {
                    str += "<pre>"
                } else {
                    str += "</pre>"
                }
            case let .preformattedText(text):
                str += text.htmlEscape()
                str += "\n"
            case let .heading(text, level: level):
                let tag = "h\(level.rawValue)"
                str += "<\(tag) id=\"l\(index)\">\(text.htmlEscape())</\(tag)>"
            case let .unorderedListItem(text):
                if !inList {
                    inList = true
                    str += "<ul>"
                }
                str += "<li>\(text.htmlEscape())</li>"
            case let .quote(text):
                str += "<blockquote>\(text.htmlEscape())</blockquote>"
            }
        }
        
        return str
    }
    
}

fileprivate extension Document.Line {
    var isListItem: Bool {
        switch self {
        case .unorderedListItem(_):
            return true
        default:
            return false
        }
    }
}