import Foundation
import Ink

final class PageContentParser {

    private let language: ContentLanguage

    private let content: Content

    private let results: PageGenerationResults

    // MARK: Command handlers

    private let buttonHandler: ButtonCommandProcessor

    private let labelHandler: LabelsCommandProcessor

    private let audioPlayer: AudioPlayerCommandProcessor

    private let icons: IconCommandProcessor

    private let box: BoxCommandProcessor

    private let html: PageHtmlProcessor

    // MARK: Other handlers

    private let inlineLink: InlineLinkProcessor

    private let code: PageCodeProcessor

    var largeImageWidth: Int {
        content.settings.pages.largeImageWidth
    }

    var thumbnailWidth: Int {
        content.settings.pages.contentWidth
    }

    init(content: Content, language: ContentLanguage, results: PageGenerationResults) {
        self.content = content
        self.results = results
        self.language = language
        self.buttonHandler = .init(content: content, results: results)
        self.labelHandler = .init(content: content, results: results)
        self.audioPlayer = .init(content: content, results: results)
        self.icons = .init(content: content, results: results)
        self.box = .init(content: content, results: results)
        self.html = .init(content: content, results: results)

        self.inlineLink = .init(content: content, results: results, language: language)
        self.code = .init(results: results)
    }

    func generatePage(from content: String) -> String {
        let parser = MarkdownParser(modifiers: [
            Modifier(target: .images, closure: processMarkdownImage),
            Modifier(target: .codeBlocks, closure: code.process),
            Modifier(target: .links, closure: inlineLink.process),
            Modifier(target: .html, closure: html.process),
            Modifier(target: .headings, closure: handleHeadlines)
        ])
        return parser.html(from: content)
    }

    /**
     Modify headlines by extracting an id from the headline and adding it into the html element

     Format: ##<title>#<id>

     The id is created by lowercasing the string, removing all special characters, and replacing spaces with scores
     */
    private func handleHeadlines(html: String, markdown: Substring) -> String {
        let id = markdown
            .last(after: "#")
            .trimmed
            .filter { $0.isNumber || $0.isLetter || $0 == " " }
            .lowercased()
            .components(separatedBy: " ")
            .filter { $0 != "" }
            .joined(separator: "-")
        let parts = html.components(separatedBy: ">")
        return parts[0] + " id=\"\(id)\">" + parts.dropFirst().joined(separator: ">")
    }

    private func percentDecoded(_ string: String) -> String {
        guard let decoded = string.removingPercentEncoding else {
            print("Invalid string: \(string)")
            return string
        }
        return decoded
    }

    private func processMarkdownImage(html: String, markdown: Substring) -> String {
        //
        let argumentList = percentDecoded(markdown.between(first: "](", andLast: ")"))
        let arguments = argumentList.components(separatedBy: ";")


        let rawCommand = percentDecoded(markdown.between("![", and: "]").trimmed)
        guard rawCommand != "" else {
            return handleImage(arguments, markdown: markdown)
        }

        guard let command = ShorthandMarkdownKey(rawValue: rawCommand) else {
            // Treat unknown commands as normal links
            results.invalid(command: nil, markdown)
            return html
        }

        switch command {
        case .image:
            return handleImage(arguments, markdown: markdown)
        case .labels:
            return labelHandler.process(arguments, markdown: markdown)
        case .buttons:
            return buttonHandler.process(arguments, markdown: markdown)
        case .video:
            return handleVideo(arguments, markdown: markdown)
        case .pageLink:
            return handlePageLink(arguments, markdown: markdown)
        case .includedHtml:
            return self.html.process(arguments, markdown: markdown)
        case .box:
            return box.process(arguments, markdown: markdown)
        case .model:
            return handleModel(arguments, markdown: markdown)
        case .svg:
            return handleSvg(arguments, markdown: markdown)
        case .audioPlayer:
            return audioPlayer.process(arguments, markdown: markdown)
        case .tagLink:
            return handleTagLink(arguments, markdown: markdown)
        case .icons:
            return icons.process(arguments, markdown: markdown)
        }
    }

    /**
     Format: `![image](<imageId>;<caption?>]`
     */
    private func handleImage(_ arguments: [String], markdown: Substring) -> String {
        guard (1...2).contains(arguments.count) else {
            results.invalid(command: .image, markdown)
            return ""
        }
        let imageId = arguments[0]

        guard let image = content.image(imageId) else {
            results.missing(file: imageId, source: "Image command")
            return ""
        }
        results.used(file: image)

        let caption = arguments.count == 2 ? arguments[1] : nil
        let altText = image.localized(in: language)

        let path = image.absoluteUrl

        guard !image.type.isSvg else {
            return SvgImage(imagePath: path, altText: altText).content
        }
        let thumbnail = image.imageSet(width: thumbnailWidth, height: thumbnailWidth, language: language)
        results.require(imageSet: thumbnail)

        let largeImage = image.imageSet(width: largeImageWidth, height: largeImageWidth, language: language)
        results.require(imageSet: largeImage)

        return PageImage(
            imageId: imageId.replacingOccurrences(of: ".", with: "-"),
            thumbnail: thumbnail,
            largeImage: largeImage,
            caption: caption).content
    }

    /**
     Format: `![video](<fileId>;<option1...>]`
     */
    private func handleVideo(_ arguments: [String], markdown: Substring) -> String {
        guard arguments.count >= 1 else {
            results.invalid(command: .video, markdown)
            return ""
        }
        let fileId = arguments[0].trimmed

        let options = arguments.dropFirst().compactMap { convertVideoOption($0, markdown: markdown) }

        guard let file = content.file(fileId) else {
            results.missing(file: fileId, source: "Video command")
            return ""
        }
        #warning("Create/specify video alternatives")
        results.require(file: file)

        guard let videoType = file.type.htmlType else {
            results.invalid(command: .video, markdown)
            return ""
        }

        return ContentPageVideo(
            filePath: file.absoluteUrl,
            videoType: videoType,
            options: options)
        .content
    }

    private func convertVideoOption(_ videoOption: String, markdown: Substring) -> VideoOption? {
        guard let optionText = videoOption.trimmed.nonEmpty else {
            return nil
        }
        guard let option = VideoOption(rawValue: optionText) else {
            results.invalid(command: .video, markdown)
            return nil
        }
        switch option {
        case .poster(let imageId):
            if let image = content.image(imageId) {
                let width = 2*thumbnailWidth
                let version = image.imageVersion(width: width, height: width, type: .jpg)
                results.require(image: version)
                return .poster(image: version.outputPath)
            } else {
                results.missing(file: imageId, source: "Video command poster")
                return nil // Image file not present, so skip the option
            }
        case .src(let videoId):
            if let video = content.video(videoId) {
                results.used(file: video)
                let link = video.absoluteUrl
                return .src(link)
            } else {
                results.missing(file: videoId, source: "Video command source")
                return nil // Video file not present, so skip the option
            }
        default:
            return option
        }
    }

    /**
     Format: `![page](<pageId>)`
     */
    private func handlePageLink(_ arguments: [String], markdown: Substring) -> String {
        guard arguments.count == 1 else {
            results.invalid(command: .pageLink, markdown)
            return ""
        }
        let pageId = arguments[0]

        guard let page = content.page(pageId) else {
            results.missing(page: pageId, source: "Page link command")
            return ""
        }
        guard !page.isDraft else {
            // Prevent linking to unpublished content
            return ""
        }

        results.linked(to: page)

        let localized = page.localized(in: language)
        let url = page.absoluteUrl(in: language)
        let title = localized.linkPreviewTitle ?? localized.title
        let description = localized.linkPreviewDescription ?? ""
        let image = makePageImage(item: localized)

        return RelatedPageLink(
            title: title,
            description: description,
            url: url,
            image: image)
            .content
    }

    /**
     Format: `![tag](<tagId>)`
     */
    private func handleTagLink(_ arguments: [String], markdown: Substring) -> String {
        guard arguments.count == 1 else {
            results.invalid(command: .tagLink, markdown)
            return ""
        }
        let tagId = arguments[0]

        guard let tag = content.tag(tagId) else {
            results.missing(tag: tagId, source: "Tag link command")
            return ""
        }

        let localized = tag.localized(in: language)
        let url = tag.absoluteUrl(in: language)
        let title = localized.name
        let description = localized.description ?? ""
        let image = makePageImage(item: localized)

        return RelatedPageLink(
            title: title,
            description: description,
            url: url,
            image: image)
            .content
    }

    private func makePageImage(item: LinkPreviewItem) -> ImageSet? {
        item.linkPreviewImage.map { image in
            let size = content.settings.pages.pageLinkImageSize
            let imageSet = image.imageSet(width: size, height: size, language: language)
            results.require(imageSet: imageSet)
            return imageSet
        }
    }

    /**
     Format: `![model](<file>)`
     */
    private func handleModel(_ arguments: [String], markdown: Substring) -> String {
        guard arguments.count == 1 else {
            results.invalid(command: .model, markdown)
            return ""
        }
        let fileId = arguments[0]
        guard fileId.hasSuffix(".glb") else {
            results.invalid(command: .model, markdown)
            return ""
        }

        guard let file = content.file(fileId) else {
            results.missing(file: fileId, source: "Model command")
            return ""
        }
        results.require(file: file)
        results.require(header: .modelViewer)

        let description = file.localized(in: language)
        return ModelViewer(file: file.absoluteUrl, description: description).content
    }

    private func handleSvg(_ arguments: [String], markdown: Substring) -> String {
        guard arguments.count == 5 else {
            results.invalid(command: .svg, markdown)
            return ""
        }

        guard let x = Int(arguments[1]),
              let y = Int(arguments[2]),
              let partWidth = Int(arguments[3]),
              let partHeight = Int(arguments[4]) else {
            results.invalid(command: .svg, markdown)
            return ""
        }

        let imageId = arguments[0]

        guard let image = content.image(imageId) else {
            results.missing(file: imageId, source: "SVG command")
            return ""
        }
        guard image.type.isSvg else {
            results.invalid(command: .svg, markdown)
            return ""
        }

        return PartialSvgImage(
            imagePath: image.absoluteUrl,
            altText: image.localized(in: language),
            x: x,
            y: y,
            width: partWidth,
            height: partHeight)
        .content
    }
}

/*
private func handleGif(file: String, altText: String) -> String {
    let imagePath = page.pathRelativeToRootForContainedInputFile(file)
    results.require(file: imagePath, source: page.path)

    guard let size = results.getImageSize(atPath: imagePath, source: page.path) else {
        return ""
    }
    let width = Int(size.width)
    let height = Int(size.height)
    return factory.html.image(file: file, width: width, height: height, altText: altText)
}
*/