import Foundation

/// Resolves a link target or image source to a safe absolute URL string, or nil when it
/// cannot be made safe.
///
/// Because the tree keeps targets typed, resolution is a renderer concern applied to the
/// `.file` case only — no resolver closure has to be threaded through the parse. Both
/// renderers resolve identically, so a link that degrades to text in HTML degrades to text
/// natively too.
package struct OrgURLResolver: Sendable {
    package var options: OrgRenderOptions

    package init(options: OrgRenderOptions) {
        self.options = options
    }

    package func href(for target: OrgLinkTarget) -> String? {
        switch target {
        case .id(let identifier):
            return sanitizedReadmeLinkURLString("#\(identifier)")
        case .external(let url):
            return sanitizedReadmeLinkURLString(url)
        case .file(let path):
            return sanitizedReadmeLinkURLString(options.linkURLResolver()?(path) ?? path)
        }
    }

    package func imageSource(_ source: String) -> String? {
        sanitizedReadmeImageURLString(options.imageURLResolver()?(source) ?? source)
    }

    /// The text a target shows when it carries no description.
    package func displayValue(_ target: OrgLinkTarget) -> String {
        switch target {
        case .external(let url): return url
        case .file(let path): return path
        case .id(let identifier): return identifier
        }
    }
}