//
//  Document.swift
//  GeminiFormat
//
//  Created by Shadowfacts on 7/12/20.
//

import Foundation

public struct Document {
    public let url: URL
    public var lines: [Line]
    
    public init(url: URL, lines: [Line] = []) {
        self.url = url
        self.lines = lines
    }
    
    /// Renders this Document to Gemini formatted text. This is not guaranteed to be the original input text.
    public func toGeminiText() -> String {
        // todo: should this be \r\n
        return lines.map { $0.geminiText() }.joined(separator: "\n")
    }
    
    public var title: String? {
        for case let .heading(text, level: _) in lines {
            return text
        }
        return nil
    }
}

public extension Document {
    enum Line: Equatable {
        case text(String)
        case link(URL, text: String?)
        case preformattedToggle(alt: String?)
        case preformattedText(String)
        case heading(String, level: HeadingLevel)
        case unorderedListItem(String)
        case quote(String)
        
        func geminiText() -> String {
            switch self {
            case let .text(text):
                return text
            case let .link(url, text: text):
                if let text = text {
                    return "=> \(url.absoluteString) \(text)"
                } else {
                    return "=> \(url.absoluteString)"
                }
            case let .preformattedToggle(alt: alt):
                if let alt = alt {
                    return "```\(alt)"
                } else {
                    return "```"
                }
            case let .preformattedText(text):
                return text
            case let .heading(text, level: level):
                return "\(level.geminiText) \(text)"
            case let .unorderedListItem(text):
                return "* \(text)"
            case let .quote(text):
                return "> \(text)"
            }
        }
    }
}

public extension Document {
    enum HeadingLevel: Int, Comparable {
        case h1 = 1, h2 = 2, h3 = 3
        
        var geminiText: String {
            switch self {
            case .h1:
                return "#"
            case .h2:
                return "##"
            case .h3:
                return "###"
            }
        }
        
        public static func < (lhs: Document.HeadingLevel, rhs: Document.HeadingLevel) -> Bool {
            return lhs.rawValue < rhs.rawValue
        }
    }
}