import UIKit

public extension NSAttributedString.Key {
    static let rdPageBlockRange = NSAttributedString.Key("com.rdreader.epub.pageBlockRange")
    static let rdPageBlockIndex = NSAttributedString.Key("com.rdreader.epub.pageBlockIndex")
    static let rdPageFragmentID = NSAttributedString.Key("com.rdreader.epub.pageFragmentID")
    static let rdPageAttachmentKind = NSAttributedString.Key("com.rdreader.epub.pageAttachmentKind")
}

public struct RDEPUBTextRenderStyle {
    public var font: UIFont
    public var lineSpacing: CGFloat
    public var textColor: UIColor?
    public var backgroundColor: UIColor?

    public init(font: UIFont, lineSpacing: CGFloat, textColor: UIColor? = nil, backgroundColor: UIColor? = nil) {
        self.font = font
        self.lineSpacing = lineSpacing
        self.textColor = textColor
        self.backgroundColor = backgroundColor
    }
}

public enum RDEPUBTextStyleSheetLayerKind: String, CaseIterable, Equatable {
    case `default`
    case replace
    case dark
    case epub
    case user
}

public struct RDEPUBTextStyleSheetLayer: Equatable {
    public var kind: RDEPUBTextStyleSheetLayerKind
    public var css: String

    public init(kind: RDEPUBTextStyleSheetLayerKind, css: String) {
        self.kind = kind
        self.css = css
    }
}

public struct RDEPUBTextStyleSheetPackage: Equatable {
    public var layers: [RDEPUBTextStyleSheetLayer]

    public init(layers: [RDEPUBTextStyleSheetLayer]) {
        self.layers = layers
    }

    public var combinedCSS: String {
        layers
            .filter { !$0.css.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
            .map { layer in
                "/* \(layer.kind.rawValue) */\n\(layer.css)"
            }
            .joined(separator: "\n\n")
    }
}

public enum RDEPUBTextResourceReferenceKind: String, Equatable {
    case stylesheet
    case image
}

public struct RDEPUBTextResourceReferenceDiagnostic: Equatable {
    public var kind: RDEPUBTextResourceReferenceKind
    public var chapterHref: String
    public var originalReference: String
    public var normalizedHref: String?
    public var resolvedFileURL: URL?
    public var existsOnDisk: Bool

    public init(
        kind: RDEPUBTextResourceReferenceKind,
        chapterHref: String,
        originalReference: String,
        normalizedHref: String?,
        resolvedFileURL: URL?,
        existsOnDisk: Bool
    ) {
        self.kind = kind
        self.chapterHref = chapterHref
        self.originalReference = originalReference
        self.normalizedHref = normalizedHref
        self.resolvedFileURL = resolvedFileURL
        self.existsOnDisk = existsOnDisk
    }
}

public struct RDEPUBTextChapterContext: Equatable {
    public var href: String
    public var title: String
    public var html: String
    public var baseURL: URL?
    public var stylesheet: RDEPUBTextStyleSheetPackage
    public var resourceDiagnostics: [RDEPUBTextResourceReferenceDiagnostic]

    public init(
        href: String,
        title: String,
        html: String,
        baseURL: URL?,
        stylesheet: RDEPUBTextStyleSheetPackage,
        resourceDiagnostics: [RDEPUBTextResourceReferenceDiagnostic]
    ) {
        self.href = href
        self.title = title
        self.html = html
        self.baseURL = baseURL
        self.stylesheet = stylesheet
        self.resourceDiagnostics = resourceDiagnostics
    }
}

public struct RDEPUBTextChapterRenderRequest {
    public var context: RDEPUBTextChapterContext
    public var style: RDEPUBTextRenderStyle

    public init(context: RDEPUBTextChapterContext, style: RDEPUBTextRenderStyle) {
        self.context = context
        self.style = style
    }
}

public struct RDEPUBRenderedChapterContent {
    public var attributedString: NSAttributedString
    public var fragmentOffsets: [String: Int]
    public var resourceDiagnostics: [RDEPUBTextResourceReferenceDiagnostic]

    public init(
        attributedString: NSAttributedString,
        fragmentOffsets: [String: Int],
        resourceDiagnostics: [RDEPUBTextResourceReferenceDiagnostic] = []
    ) {
        self.attributedString = attributedString
        self.fragmentOffsets = fragmentOffsets
        self.resourceDiagnostics = resourceDiagnostics
    }
}

public protocol RDEPUBTextRenderer {
    func renderChapter(
        request: RDEPUBTextChapterRenderRequest
    ) throws -> RDEPUBRenderedChapterContent

    func renderChapter(
        html: String,
        baseURL: URL?,
        style: RDEPUBTextRenderStyle
    ) throws -> RDEPUBRenderedChapterContent
}

public extension RDEPUBTextRenderer {
    func renderChapter(
        html: String,
        baseURL: URL?,
        style: RDEPUBTextRenderStyle
    ) throws -> RDEPUBRenderedChapterContent {
        let context = RDEPUBTextChapterContext(
            href: "",
            title: "",
            html: html,
            baseURL: baseURL,
            stylesheet: RDEPUBTextStyleSheetPackage(layers: []),
            resourceDiagnostics: []
        )
        return try renderChapter(request: RDEPUBTextChapterRenderRequest(context: context, style: style))
    }
}

public enum RDEPUBTextRenderingError: LocalizedError {
    case htmlEncodingFailed
    case htmlImportFailed

    public var errorDescription: String? {
        switch self {
        case .htmlEncodingFailed:
            return "HTML 编码失败"
        case .htmlImportFailed:
            return "HTML 富文本导入失败"
        }
    }
}