import Foundation
#if os(macOS)
import AppKit
private typealias PlatformFont = NSFont
#else
import UIKit
private typealias PlatformFont = UIFont
#endif

extension NSAttributedString.Key {
    static let docsNode = NSAttributedString.Key("OficinaDocsNode")
    static let docsBlock = NSAttributedString.Key("OficinaDocsBlock")
    static let docsOffset = NSAttributedString.Key("OficinaDocsOffset")
    static let docsQuoteBorders = NSAttributedString.Key("OficinaDocsQuoteBorders")
    static let docsMarks = NSAttributedString.Key("OficinaDocsMarks")
}
@MainActor enum NativeTextProjection {
    static func render(_ projection: CRDTProjection, images: [String: DocsPlatformImage] = [:]) -> NSAttributedString {
        let output = NSMutableAttributedString(string: "")
        for node in projection.children {
            let start = output.length
            append(node, to: output, depth: 0, lists: [], images: images)
            #if os(macOS)
            let margins = DocumentBlockSpacing.margins(node)
            output.addAttributes([.docsTopBlock: node.id, .docsMarginBefore: margins.0, .docsMarginAfter: margins.1],
                                 range: NSRange(location: start, length: output.length - start))
            #endif
        }
        DocumentBlockSpacing.apply(projection.children, to: output)
        DocumentInlineCode.apply(to: output)
        return output
    }
    private static func append(_ node: CRDTNode, to output: NSMutableAttributedString, depth: Int, lists: [NSTextList], images: [String: DocsPlatformImage], containers: [DocsClipboardContainer] = []) {
        if ["bullet_list", "ordered_list", "list_item", "blockquote"].contains(node.type) {
            var nested = lists
            if node.type == "bullet_list" { nested.append(NSTextList(markerFormat: .disc, options: 0)) }
            if node.type == "ordered_list" {
                let list = NSTextList(markerFormat: .decimal, options: 0)
                if let order = Int(node.attrs?["order"] ?? ""), (Int(Int32.min)...Int(Int32.max)).contains(order) { list.startingItemNumber = order }
                nested.append(list)
            }
            let ancestry = containers + [DocsClipboardContainer(id: node.id, type: node.type, attrs: node.attrs)]
            for child in node.children ?? [] { append(child, to: output, depth: depth + (node.type == "list_item" || node.type == "blockquote" ? 1 : 0), lists: nested, images: images, containers: ancestry) }
            return
        }
        let start = output.length
        let style = NSMutableParagraphStyle()
        style.paragraphSpacing = 0
        style.textLists = lists
        let indent = max(0, min(8, Int(node.attrs?["indent"] ?? "0") ?? 0))
        style.headIndent = containers.reduce(CGFloat(indent * 36)) { offset, container in
            offset + (container.type == "list_item" ? 16.8 : container.type == "blockquote" ? 14.25 : 0)
        }
        style.firstLineHeadIndent = style.headIndent
        switch node.attrs?["align"] { case "center": style.alignment = .center; case "right": style.alignment = .right; default: style.alignment = .left }
        let heading = node.type == "heading" ? max(1, min(6, Int(node.attrs?["level"] ?? "1") ?? 1)) : 0
        #if os(macOS)
        style.headerLevel = heading
        #endif
        let base: CGFloat = heading == 1 ? 19.2 : heading == 2 ? 15.6 : heading == 3 ? 13.2 : 12
        let leading: CGFloat = heading > 0 ? 1.3 : 1.4
        var inheritedMarks: [String: JSONValue] = [:]
        if heading >= 4 || containers.contains(where: { $0.type == "blockquote" }) { inheritedMarks["em"] = .object([:]) }
        if node.type == "code_block" { inheritedMarks["code"] = .object([:]) }
        let baseFont = font(marks: inheritedMarks, size: base, heading: heading > 0)
        #if os(macOS)
        let naturalHeight = NSLayoutManager().defaultLineHeight(for: baseFont)
        #else
        let naturalHeight = baseFont.lineHeight
        #endif
        style.lineHeightMultiple = base * leading / naturalHeight
        style.minimumLineHeight = base * leading
        if heading > 0 {
            style.paragraphSpacingBefore = base * 1.5
            style.paragraphSpacing = base * 0.5
        }
        var baseAttributes: [NSAttributedString.Key: Any] = [.paragraphStyle: style, .font: baseFont, .docsBlock: node.id, .docsBlockType: node.type, .docsHeading: heading]
        #if os(macOS)
        baseAttributes[.docsBaseFont] = baseFont
        baseAttributes[.docsLeading] = leading
        #endif
        var quoteBorders: [CGFloat] = []
        var containerIndent: CGFloat = 0
        for container in containers {
            if container.type == "blockquote" { quoteBorders.append(containerIndent); containerIndent += 14.25 }
            if container.type == "list_item" { containerIndent += 16.8 }
        }
        if !quoteBorders.isEmpty {
            baseAttributes[.docsQuoteBorders] = quoteBorders
            #if os(macOS)
            baseAttributes[.foregroundColor] = NSColor(white: 74.0 / 255, alpha: 1)
            #else
            baseAttributes[.foregroundColor] = UIColor(white: 74.0 / 255, alpha: 1)
            #endif
        }
        baseAttributes[.docsBlockAttributes] = try? JSONEncoder().encode(node.attrs ?? [:])
        baseAttributes[.docsClipboardContainers] = try? JSONEncoder().encode(containers)
        if node.type == "horizontal_rule" {
            let rule = NSMutableAttributedString(attributedString: DocsAttachments.rule(width: 468))
            rule.addAttributes(baseAttributes, range: NSRange(location: 0, length: rule.length))
            output.append(rule); output.append(NSAttributedString(string: "\n", attributes: baseAttributes)); return
        }
        for child in node.children ?? [] {
            if child.type == "text" {
                var offset = 0
                for run in child.runs ?? [] {
                    var attributes = baseAttributes
                    let marks = run.marks ?? [:]
                    var visualMarks = inheritedMarks.merging(marks, uniquingKeysWith: { _, authored in authored })
                    if node.type == "code_block" { visualMarks["code"] = .object([:]) }
                    attributes[.font] = font(marks: visualMarks, size: base, heading: heading > 0)
                    attributes[.docsNode] = child.id
                    attributes[.docsOffset] = offset
                    attributes[.docsMarks] = try? JSONEncoder().encode(marks)
                    if case .object(let link)? = marks["link"], case .string(let href)? = link["href"], let url = URL(string: href), ["https", "http", "mailto"].contains(url.scheme ?? "") { attributes[.link] = url }
                    output.append(NSAttributedString(string: run.insert, attributes: attributes))
                    offset += run.insert.utf16.count
                }
            } else if child.type == "hard_break" { output.append(NSAttributedString(string: "\u{2028}", attributes: baseAttributes)) }
            else if child.type == "image" { let image = NSMutableAttributedString(attributedString: DocsAttachments.image(images[child.attrs?["src"] ?? ""], alt: child.attrs?["alt"] ?? "", maxWidth: 468))
                image.addAttributes(baseAttributes.merging([.docsNode: child.id], uniquingKeysWith: { _, new in new }), range: NSRange(location: 0, length: image.length))
                if let attrs = try? JSONEncoder().encode(child.attrs ?? [:]) { image.addAttribute(.docsImageAttributes, value: attrs, range: NSRange(location: 0, length: image.length)) }
                output.append(image) }
            else { append(child, to: output, depth: depth, lists: lists, images: images, containers: containers) }
        }
        var ending = baseAttributes
        if output.length == start { ending[.docsNode] = node.id; ending[.docsOffset] = 0 }
        output.append(NSAttributedString(string: "\n", attributes: ending))
    }
    private static func font(marks: [String: JSONValue], size: CGFloat, heading: Bool) -> PlatformFont {
        DocsFonts.font(marks: marks, size: size, heading: heading)
    }
}