import Foundation

enum RDEPUBFixedLayoutTemplate {

    static func html(for request: RDEPUBFixedRenderRequest, publication: RDEPUBPublication) -> String {

        let panes = request.spread.resources.enumerated().compactMap { index, resource -> String? in
            guard let url = publication.resourceResolver.resourceURL(forRelativePath: resource.href)?.absoluteString else {
                return nil
            }

            let pageType: String
            if request.spread.resources.count == 1 {
                pageType = "single"
            } else if request.spread.resources.count == 2 {
                pageType = index == 0 ? "left" : "right"
            } else {
                pageType = "center"
            }

            return """
            <div class=\"ss-fixed-viewport\" data-page-type=\"\(pageType)\">
              <iframe class=\"ss-fixed-page\" data-page-type=\"\(pageType)\" scrolling=\"no\" src=\"\(url)\"></iframe>
            </div>
            """
        }.joined()

        let background = request.backgroundColorCSS ?? "#FFFFFF"
        let viewportWidth = max(1, Int((request.viewportSize.width - request.contentInset.left - request.contentInset.right).rounded(.down)))
        let viewportHeight = max(1, Int((request.viewportSize.height - request.contentInset.top - request.contentInset.bottom).rounded(.down)))
        let insetTop = Int(request.contentInset.top.rounded(.down))
        let insetRight = Int(request.contentInset.right.rounded(.down))
        let insetBottom = Int(request.contentInset.bottom.rounded(.down))
        let insetLeft = Int(request.contentInset.left.rounded(.down))

        return RDEPUBAssetRepository.string(
            for: .fixedLayoutTemplate,
            replacements: [
                "BACKGROUND": background,
                "INSET_TOP": String(insetTop),
                "INSET_RIGHT": String(insetRight),
                "INSET_BOTTOM": String(insetBottom),
                "INSET_LEFT": String(insetLeft),
                "VIEWPORT_WIDTH": String(viewportWidth),
                "VIEWPORT_HEIGHT": String(viewportHeight),
                "PANES": panes,
                "FIT_MODE": request.fit.rawValue,
                "FIXED_LAYOUT_READY_MESSAGE": RDEPUBJavaScriptBridgeMessage.fixedLayoutReady.rawValue
            ]
        )
    }
}